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  • Articles  (722)
  • Solanum tuberosum L.  (270)
  • Zea mays  (240)
  • tomato  (212)
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  • Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition  (722)
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  • Articles  (722)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Biology and fertility of soils 31 (2000), S. 348-355 
    ISSN: 1432-0789
    Keywords: Key words Agroforestry ; Land use ; Nitrate leaching ; Zea mays ; Musa spp.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  We hypothesized that the integration of trees and shrubs in agricultural landscapes can reduce NO3 – leaching and increase utilization of subsoil N. A field survey was conducted on 14 farms on acid soils in the subhumid highlands of Kenya, where there is little use of fertilizers, to determine the effect of vegetation types (VT) on soil NH4 + and NO3 – to 4 m depth. The VT included maize (Zea mays) with poor growth and good growth, Markhamia lutea trees scattered in maize, natural weed fallow, banana (Musa spp.), hedgerow, and eucalyptus woodlot. The effect of VT on NH4 + was small (〈1 mg N kg–1). NO3 – within a VT was about constant with depth below 0.25 m, but subsoil NO3 – varied greatly among VT. Mean NO3 –-N concentrations at 0.5–4 m depth were low beneath hedgerow and woodlot (〈0.2 mg kg–1), intermediate beneath weed fallow (0.2–0.7 mg kg–1), banana (0.5–1.0 mg kg–1) and markhamia (0.5–1.6 mg kg–1), and high beneath both poor (1.0–2.1 mg kg–1) and good (1.9–3.1 mg kg–1) maize. Subsoil NO3 – (0.5–4 m) was agronomically significant after maize harvest with 37 kg N ha–1 m–1 depth of subsoil beneath good maize and 27 kg N ha–1 m–1 depth beneath poor maize. In contrast, subsoil NO3 – was only 2 kg N ha–1 m–1 depth beneath woodlot and hedgerow. These results demonstrate that the integration of perennial vegetation and the rotation of annual and perennial crops can tighten N cycling in agricultural landscapes.
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  • 2
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    Biology and fertility of soils 31 (2000), S. 525-532 
    ISSN: 1432-0789
    Keywords: Key words Ferrihydrite ; Phosphate ; Polygalacturonic acid ; Root mucilage ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  This study was conducted to determine the influence of root mucilage (RM) from Zea mays, polygalacturonic acid (PGA), and galacturonic acid (GA), on the adsorption, desorption, and exchangeability of orthophosphate (P) on a synthetic ferrihydrite in deionized water. The adsorption rate and affinity on the oxide decreased in the order P〉GA〉PGA≥RM. The results suggest that P and GA were adsorbed by ligand exchange on Fe-OH surface sites, while RM and PGA might in addition also be adsorbed by hydrogen and van der Waals bonds to the oxide surface. Whereas P and GA could be adsorbed at sites located inside the micropores of ferrihydrite aggregates, PGA and RM probably remained on the external surfaces because of their large molecular weight. The preliminary adsorption of organic compounds decreased the subsequent P adsorption. The larger decrease of P adsorption occurred when dry ferrihydrite powder was directly added to the RM/water suspension. This effect was due to the flocculation of ferrihydrite aggregates, which limited the transport of P to the adsorption sites. Preliminary adsorption of GA also decreased P adsorption, because both compounds competed for the same Fe-OH sites. The ability of the organic compounds to desorb P from the ferrihydrite was not very pronounced and decreased in the order GA〉PGA≥RM. The preliminary adsorption of organic compounds on the oxide resulted in an increase in isotopically exchangeable P in 300 min compared to the treatment without organic compounds. However, because of its higher affinity for the oxide surface, P exchangeability was not modified when P was added before the organic compounds.
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  • 3
    ISSN: 1871-4528
    Keywords: Solanum tuberosum L. ; Storite Clear ; Storite Flowable ; radionuclide ; scintillation counting ; sprout suppression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The use of imazethapyr as a sprout suppressant in potatoes has been investigated. Novel radionuclide techniques were developed to establish the patterns of uptake and movement of imazethapyr in potatoes. Protocols for tissue analysis were established to homogenise potato tuber tissue samples, enabling radiolabel recovery by liquid scintillation counting to approach 100%. The movement of imazethapyr was also examined in the presence of an acidic formulation of thiabendazole which caused increased uptake. The movement of imazethapyr within the tuber was also influenced by pH and ion trapping.
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  • 4
    ISSN: 1871-4528
    Keywords: Solanum tuberosum L. ; plant development ; antioxidant genes ; gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The expression of antioxidant genes has been analyzed in a potato plant and during tuber dormancy. Manganese superoxide dismutase (MnSOD), cytosolic copper and zinc superoide dismutase (Cu/ZnSOD), catalase class II, cytosolic ascorbate peroxidase (APX) and glutathione peroxidase (GPX) are expressed at the RNA level in all the contexts analyzed. By contrast, the expression of the iron superoxide dismutase (FeSOD) and plastidic Cu/ZnSOD seems to be limited to green tissues, as shown by northern blots and native gels. A complex DAB-peroxidase isozyme pattern (using diaminobenzidine as substrate) has been observed in different developmental contexts analyzed, but hardly observed in tubers. During tuber dormancy, MnSOD and cytosolic Cu/ZnSOD activity was relatively constant in both Désirée and Bintje varieties while catalase activity decreases. Moreover, tuber dormancy breakage did not involve significant changes in the activity of these enzymes. On the basis of these results, the possible link between active oxygen species (AOS) metabolism and dormancy is discussed.
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  • 5
    ISSN: 1871-4528
    Keywords: actinomycetes ; resistance ; scab incidence ; Solanum tuberosum L. ; Streptomyces scabies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Concentrations of Ca, P, K, Mg, Al, Fe, Mn, Cu and Zn were determined in healthy tuber peelings of cultivars less (Karin, Santé and Symfonia) and more (Agria, Désirée and Tomensa) susceptible to common scab when grown at two sites that differed in the level of scab incidence. The accumulation of some elements was significantly influenced by site, year, cultivar, maturity and the age of tuber periderm. At both sites, Ca and P in periderm tissue declined but Mg increased during the growing season. The Ca/P ratios in tuber periderm of all cultivars greatly decreased 83 days after planting. Concentrations of mineral elements measured at harvest may not reflect conditions present during the infection period, and consequently may not be related to scab incidence or severity.
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  • 6
    ISSN: 1871-4528
    Keywords: Solanum tuberosum L. ; prickle pollination ; ploidy level ; flow-cytometry ; adventitious shoots ; in vitro tuber induction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary For the induction and selection of double mutants with altered starch composition, a uniform (homohistont) amylose-free (amf) monoploid as basic plant is of vital importance. Therefore, newamf monoploids had to be developed via prickle pollination. And 26 monoploids were obtained which were screened in vitro for vigour, leaf size and for the percentage of monoploid cells. The number of monoploid cells was underestimated at about 28%. Seven vigorous monoploids were tested in vitro for tuberization capacity, which varied from 0 to 100%. After regeneration in vitro, 0 to 3.7 adventitious shoots per leaf explant were formed. The tuberization capacity of these shoots varied from 0 to 48. Twoamf monoploids were selected which were vigorous and tuberized well in vitro. They are the basis for the application of an in vitro mutation breeding protocol that should lead to the induction and selection of new starch mutants in potato.
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  • 7
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    Potato research 43 (2000), S. 253-261 
    ISSN: 1871-4528
    Keywords: laboratory tests ; storage ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary After a wet autumn and harvesting under wet conditions, slugs brought into potato stores via clods and soil adhering to tubers may cause substantial damage by feeding on the tubers. A carvone sprout inhibitor, Talent®, applied in the potato stores at a dose of 50 ml per tonne potatoes, controlled slugs within a few days. A dose of 25 ml carvone was insufficient. Using a laboratory box test, the slug (Deroceras reticulatum) affected only wounded tubers and, although slime was present on the unwounded potatoes, they were not damaged by slugs.
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  • 8
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    Potato research 43 (2000), S. 273-278 
    ISSN: 1871-4528
    Keywords: cold storage ; store management ; potato handling ; tuber temperature ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The effect of using radiant heat to quickly warm potatoes and reduce damage in handling after cold storage was investigated. Two treatments were investigated: tubers dropped 350 mm with no radiant heat applied, and tubers dropped with radiant heat applied. Both treatments were compared with a control set of tubers which were taken directly out of store. The mean damage index per tuber was significantly reduced following radiant heat treatment although there were cultivar and size variations. The temperature profile under radiant heat was also measured which showed an increase in the outside flesh temperature of 8–12°C depending on tuber colour.
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  • 9
    ISSN: 1871-4528
    Keywords: chemical inducible gene expression ; glutathione S-transferase ; Solanum tuberosum L. ; herbicide safener ; tuber
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Chemically inducible gene regulation systems provide a mechanism for a temporal control of expression of transgenes. In this study expression from the herbicide safener inducible maize GST-27 promoter was tested in potato, with the aim of using this to provide inducible expression of transgenes implicated in dormancy control. A binary vector comprising 3.8 kb of the GST-27 promoter was fused to the β-glucuronidase (GUS) reporter gene and transformed into potato. Application of the chemical inducer elevated the expression of GUS up to 40 fold in leaf tissue. However in stems, roots and tubers the GST-27 promoter caused high levels of expression of GUS in the absence of safener, demonstrating that in these tissues it acts as a constitutive promoter. A deleted promoter region of the GST-27 promoter displayed a similar expression pattern. Analysis of GUS activity in dormant and sprouting tubers showed that the GST-27 promoter was a strong constitutive promoter throughout the tuber life cycle.
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  • 10
    ISSN: 1871-4528
    Keywords: Solanum tuberosum L. ; damage ; bruising ; blackspot ; handling ; velocity change
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Potatoes are exposed to mechanical forces which can lead to subcutaneous tissue discoloration resulting in losses. We investigated the number and intensity of impacts in different phases of representative Dutch ware potato handling chains using an instrumented sphere (IS). Other questions we asked were, to which drop height onto a defined surface do measured impacts correspond, and what is the relation between the number of impacts and damage? Close relationships between peak acceleration and velocity change for different drop heights were found for various cushioning materials, thus allowing interpretation of impact measurements in terms of drops. The IS recorded c. 340 impacts exceeding 30g. The contribution to the total number of impacts was 11% for Harvest, 0% for Storage, 10% for Transport and 79% for Packaging. The number and intensity of impacts correlated well with the amount of subcutaneous tissue discoloration. It is concluded that the produce-friendliness of the handling chains can be improved.
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  • 11
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    Potato research 43 (2000), S. 287-295 
    ISSN: 1871-4528
    Keywords: nutrient analysis ; culture media ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Boron (B) requirements differ widely among plant species and the concentration range between toxicity and deficiency is less for B than for any other nutrient. Excess B can adversely affect calcium (Ca) uptake and plant growth. Potato cvs Bintje and Norland plantlets were micropropagated on Murashige & Skoog (MS) nutrient medium, supplemented with 3 (MS control level) or 9 mM Ca, and a range of H3BO3 levels (0.025 to 0.300 mM B). Medium B levels of 0.100 and 0.300 mM decreased Ca content in leaves and shoots of cv. Norland, but not Bintje. Medium B level of 0.025 mM, which is 25% of the control MS level, enhanced Ca uptake in cv. Norland and did not compromise normal plantlet growth in either cultivar. This lower H3BO3 level (0.025 mM B), and a B-free gelling agent such as Gelrite, could be used for micropropagation of potato and possibly other species susceptible to Ca defifiency disorders.
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  • 12
    ISSN: 1871-4528
    Keywords: root-water uptake ; modeling ; SWACROP ; Ferralsols ; tropics ; Cuba ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The SWACROP root-water uptake function for potatoes was determined in the 1994–95 crop season on a Ferralsol in Havana province, west Cuba. The maximum pressure-heads under which water is optimally extracted by potato roots were very similar to the original Feddes function. Nevertheless, the anaerobiosis point and the wilting point pressure-head in both functions were not in agreement. However, the simulated values of soil water contents in the 0–40 cm soil depth by performing SWACROP runs in the 1995–96 potato crop season using both functions were very similar. The original Feddes function seems to be good enough for predicting soil water contents in the tropics and no specific other functions need to be developed for any particular soil or climate condition.
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  • 13
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    Potato research 43 (2000), S. 43-48 
    ISSN: 1871-4528
    Keywords: Solanum tuberosum L. ; Decis® ; Colorado potato beetle ; tuber quality ; dry matter content
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Tubers showed changes in their nutritional value caused by the treatment of the plants with the insecticide deltamethrin. The level of starch was increased in comparison with control tubers; but the amylose percentage was not affected. In contrast, the total protein content decreased in tubers from treated plants, whereas free amino acids level and ascorbic acid content increased. The results showed that the changes in the tubers caused by the treatment of potato plants with deltamethrin did not adversely affect the nutritional value of the progeny tubers.
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  • 14
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    Potato research 43 (2000), S. 97-106 
    ISSN: 1871-4528
    Keywords: Solanum tuberosum L. ; National List ; Recommended Trials ; growing crop ; tuber ; yield ; quality ; disease ; nematodes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary In 1994, a postal questionnaire was sent to 41 institutes in 27 countries to obtain information on the national potato cultivar testing programmes in Europe. Responses were received from 19 countries. Foliage, tuber and yield characteristics were assessed in all countries but the number of sites and replicated varied considerably between the countries. Cooking and taste qualities were measured in most countries using relatively simple methods but processing characteristics were tested less commonly. Susceptibility to the most common diseases, i.e. late blight, common scab, leafroll and PVYo, was assessed in over 75% of the countries while resistance to another 21 disease and 4 potato cyst nematode pathotypes was assessed by various countries, depending on their national importance. Many of the assessments were based on records of natural infection although controlled inoculation tests were done more frequently for the more important diseases.
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  • 15
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    Potato research 43 (2000), S. 49-59 
    ISSN: 1871-4528
    Keywords: Solanum tuberosum L. ; soil fertility ; soluble salts ; plant spacing ; Rhizoctonia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Excessive fertilizer application in North Carolina, USA results in high residual soil levels of P, K and total soluble salts in potato fields. Our objectives were to determine the salt sensitivity of three common cultivars (Atlantic. Snowden and Superior), and the effects of planting density and fertilization on stand establishment, soilborne disease, and yield. Greenhouse results suggest that potato growth and emergence, but not shoot initation, are reduced by high salinity. On a Portsmouth fine sandy loam, high fertilizer rates did not reduce stands of cv. Atlantic in the field in 1996 or 1997. Excess N resulted in moreRhizoctonia stem canker in 1996, and lower yields at the lower planting density in 1997. Yield compensation for reduced plant density occurred in 1997 at the lower N rates (56 and 112 kg N ha−1) and at the high PK rate (49 kg P and 139 kg K ha−1).
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  • 16
    ISSN: 1871-4528
    Keywords: Solanum tuberosum L. ; potato tuberization ; growth regulators
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A reverse of the delaying effect of gibberellic acid (GA3) was observed in in vitro tuberization of potato plantlets when the medium contained 0.8×10−5 M jasmonic acid (JA). The promoting effect of JA seemed to be correlated with the initial absence of growing roots, probably through direct activity of JA in microtuber-producing buds in the stoloniferous shoots. This is based on the fact that JA did not inhibit root growth a posteriori. Endogenous gibberellins (GAs) synthesized by roots did not interfere with the previous activity of JA in tuberization. The absence of a JA promoting-effect on tuberization of previously-rooted plantlets could be related to the capacity of potato roots to synthesize endogenous GAs which might antagonize the JA effect on buds of stoloniferous shoots.
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  • 17
    ISSN: 1871-4528
    Keywords: transgenic plants ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Helicoverpa armigera is one of the important insect pests adversely affecting the yield of potatoes in India. A synthetic gene encoding the insecticidal crystal protein (Cry1Ab) ofBacillus thuringiensis (Bt) has been introduced into five genotypes of potato usingAgrobacterium tumefaciens. Southern analysis of DNA from transgenic plants confirmed the integration and copy number of the transgene. Double-antibody quantitative sandwich ELISA analysis demonstrated high levels of Cry1Ab protein expression in transgenic plants. Insect bioassays on the leaves of transgenic plants showed considerable protection against the larvae ofH. armigera in terms of leaf area consumed and larval weight reduction.
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  • 18
    ISSN: 1871-4528
    Keywords: Solanum tuberosum L. ; damage ; bruising ; impact ; blackspot ; handling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary In the chain of handling operations from harvesting to packaging inclusive, potatoes are exposed to many brief mechanical forces (impacts) and to long-term pressure. Impact and pressure can lead to subcutaneous tissue discoloration causing qualitative and quantitative losses. We investigated the characteristics of construction and utilization of representative Dutch ware potato handling chains and found that the number and height of drops appeared to be too high, the use of cushioning materials insufficient and the speed of the transporting parts too high and not in balance with each other. The contribution to the total amount of subcutaneous tissue discoloration was 16% for the harvesting to bin filling phases inclusive, 22% for the storage phase, 27% for the shovelling to truck loading phases inclusive and 35% for the truck unloading to packaging phases inclusive. These contributions varied considerably within phases and within links. The results can be used to develop equipment, upgrade present chains and design new, produce-frendly handling chains.
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  • 19
    ISSN: 1871-4528
    Keywords: Helminthosporium solani ; storage conditions ; disease resistance ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Optimum storage conditions to identify resistance to silver scurf among commercially grown potato cultivars were determined in a series of experiments. Inoculation of field-grown tubers with a conidial suspension ofH. solani (concentration 104 conidia per ml of water) and incubation at 15°C with 95% RH for 1 month followed by 2 months at 85% RH produced the greatest differences in disease severity between potato cultivars. Results with glasshouse-grown tubers were comparable with those from field-grown tubers, indicating that the test could be used to identify resistance in wild species of potato and to understand the inheritance of this resistance.
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  • 20
    ISSN: 1871-4528
    Keywords: Solanum tuberosum L. ; sexual reproduction ; oospores
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The severity of late blight tuber rot in five potato cultivars (Green Mountain, Sebago, Dorita, AC Brador and Island Sunshine) resulting from inoculation with US-1/US-8 combinations of Canadian isolates ofPhytophthora infestans was evaluated. In addition, the potential for mixed (A1∶A2) inoculations to result in oospore formation was examined. In studies conducted in 1996 and 1997, cv. Dorita (and Island Sunshine in 1997) developed the least amount of surface or internal necrosis relative to the other cultivars following co-inoculation with US-1 and US-8 isolates ofP. infestans. Differences also were revealed among isolate combinations used for inoculation. The combination of a US-1 isolate from Prince Edward Island with a US-8 isolate from New Brunswick consistently produced the least amount of necrosis in tubers of the various cultivars. There was no evidence of oospore production in any of the tubers examined.
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  • 21
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    European journal of plant pathology 106 (2000), S. 693-698 
    ISSN: 1573-8469
    Keywords: differential gene expression ; grey mould ; ribosomal biogenesis ; tomato
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract To identify genes of the necrotrophic pathogenic fungus Botrytis cinerea that are expressed during infection of tomato leaves, a differential screening of a genomic library with radioactively labelled cDNA was performed. This resulted in the identification of a B. cinerea gene, denominated Bcubi4, which encodes a precursor protein consisting of four identical head-to-tail repeats of a 76 aa ubiquitin unit. Subsequently a gene denominated Bcubi1CEP79, encoding a single ubiquitin unit joined to a Carboxyl Extension Protein of 79 amino acids, was isolated. The expression of the two ubiquitin genes was studied during pathogenesis of B. cinerea on tomato. Bcubi1CEP79, but not Bcubi4, mRNA was transiently induced at 16 h after inoculation. The increased expression of the Bcubi1CEP79 gene at this stage of pathogenesis might be required for enhanced ribosomal biogenesis.
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  • 22
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    European journal of plant pathology 106 (2000), S. 465-473 
    ISSN: 1573-8469
    Keywords: tomato ; powdery mildew ; Oidium lycopersici ; host range ; host resistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Nine accessions of three cucurbit species, ten of eight legume species, three of lettuce (Lactuca sativa) and 34 of 14 Solanaceae species were inoculated with a Dutch isolate of the tomato powdery mildew fungus (Oidium lycopersici) to determine its host range. Macroscopically, no fungal growth was visible on sweet pepper (Capsicum annuum), lettuce, petunia (Petunia spp.) and most legume species (Lupinus albus, L. luteus, L. mutabilis, Phaseolus vulgaris, Vicia faba, Vigna radiata, V. unguiculata). Trace infection was occasionally observed on melon (Cucumis melo), cucumber (Cucumis sativus), courgette (Cucurbita pepo), pea (Pisum sativum) and Solanum dulcamara. Eggplant (Solanum melongena), the cultivated potato (Solanum tuberosum) and three wild potato species (Solanum albicans, S. acaule and S. mochiquense) were more heavily infected in comparison with melon, cucumber, courgette, pea and S. dulcamara, but the fungus could not be maintained on these hosts. All seven tobacco (Nicotiana tabacum) accessions were as susceptible to O. lycopersici as tomato (Lycopersicon esculentum cv Moneymaker), suggesting that tobacco is an alternative host. This host range of the tomato powdery mildew differs from that reported in some other countries, which also varied among each other, suggesting that the causal agent of tomato powdery mildew in the Netherlands differ from that in those countries. Histological observations on 36 accessions showed that the defense to O. lycopersici was associated with a posthaustorial hypersensitive response.
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  • 23
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    European journal of plant pathology 106 (2000), S. 589-592 
    ISSN: 1573-8469
    Keywords: Closterovirus ; Crinivirus ; ToCV ; tomato ; whiteflies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Tomato chlorosis virus (ToCV), a new whitefly-transmitted and phloem-limited Crinivirus infecting tomatoes in Europe, is reported for the first time in Portugal. Tomato plants with symptoms of interveinal chlorosis, collected during autumn 1998 and summer and autumn 1999 in Algarve, southern Portugal, were positive in RT-PCR assays using ToCV-specific primers. The amplified 439 bp fragment was sequenced and showed 99% homology with the ToCV sequence in the GenBank database. A digoxigenin–DNA probe was produced and tested in dot-blot with total RNAs extracted from tomato samples. Both the RT-PCR and dot-blot hybridisation procedures enabled rapid and reliable detection of ToCV from field samples.
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  • 24
    ISSN: 1573-5036
    Keywords: Crop residues ; dry-matter yields ; Medicago sativa ; N mineralization ; 15N uptake ; Zea mays ; VAM fungi
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Legume crop residues serve as a source of nitrogen (N) for succeeding crops in low-input production systems, and characterizing the release of this N supports efforts to develop sound economic and environmental management practices. Nitrogen mineralization of 15N-labelled field crop residues was monitored in a Greenville sandy loam during a 140-day laboratory incubation at 25°C. Residue type strongly influenced the rate of N mineralization; decomposition rate constants were 0.283, 0.083, 0.00047 and 0.0014 day-1 for alfalfa (Medicago sativa L.) stover (above-ground plant parts), alfalfa roots, maize (Zea mays L.) stover (above-ground plant parts excluding cob and kernels) and maize roots, respectively. At the end of the incubation, 50% of alfalfa stover and 25% of alfalfa root residues N were mineralized, whereas these proportions were 8% for maize stover and 12% for root residues. Mineralization of 15N from alfalfa stover residues was also monitored in a greenhouse experiment to determine N availability during the growth of maize inoculated or not with vesicular-arbuscular mycorrhizal (VAM) fungi, and to evaluate the effects of the presence of plants on the decomposition of the residues. Stover and root dry matter yields were greatest for maize inoculated with VAM fungi and grown in residue-amended soil. At the final harvest, maize grown in residue-amended soils had accumulated 44% more dry matter and 40% more N than maize grown in unamended soils. Enhanced VAM colonization of roots inoculated with a mixture of three Glomus spp. increased the residue N accumulation in maize roots at 5 weeks after silking and at the final harvest. Alfalfa stover decomposed rapidly both in the presence and absence of maize plants, but the amount of 15N mineralized at the end of the experiment was influenced by the presence of living roots; 23% of the 15N in alfalfa stover residues was mineralized in soil without plants compared to about 38% when maize plants were present. These results suggest that N mineralization is enhanced by the presence of living roots.
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  • 25
    ISSN: 1573-5036
    Keywords: agricultural practices ; extra-radical mycelium ; Gliricidia sepium ; organic matter addition ; Peltophorum dasyrachis ; soil disturbance ; species richness of AMF ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Two pre-established agricultural field trials were assessed for the abundance of arbuscular mycorrhizal fungi (AMF) in the soil (density of spores, species richness and lengths of extra-radical mycelium [ERM]) in association with one of three tropical plant species (Gliricidia sepium, Peltophorum dasyrachis and Zea mays). The trials were managed by one of three agricultural practices: soil disturbance in a monoculture system, a root barrier to prevent interactions between plants in an agroforestry system or the addition of organic matter (OM) in an agroforestry and a monoculture system. The lengths of ERM of AMF in the soil were greater in the agroforestry system than the monoculture system. These were greater when a root barrier was present, but decreased when OM was added. Soil disturbance reduced the density of spores, species richness and the lengths of ERM of AMF compared with the undisturbed soil. This work indicates that agricultural trials may provide a useful tool to monitor the abundance of AMF in the field. Clearly, there is potential to increase the abundance of AMF, from different genera, in the soil through the management of agricultural practices. The significance of the abundance of AMF for subsequent benefits to plant growth and development and ultimately the sustainability of tropical agro-ecosystems are discussed.
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  • 26
    ISSN: 1573-5036
    Keywords: amino acids ; chicory ; copper ; tomato ; xylem sap
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effect of rooting media Cu concentration (0.05–20 mg Cu L-1) on amino acid concentrations and copper speciation in the xylem sap of chicory and tomato plants was measured using 6 week old plants grown in a nutrient film technique system (NFT). Irrespective of the Cu concentration in the nutrient solutions, more than 99.68% and 99.74% of total Cu in tomato and chicory xylem sap was in a bound form. When exposed to high Cu concentrations in the rooting media, amino acid concentrations in the sap increased. Relative to other amino acids, the concentrations of glutamine (Gln), histidine (His), asparagine (Asn), valine (Val), nicotianamine (NA) and proline (Pro) in tomato xylem saps, and His, γ-aminobutyric acid (Gaba), glutamic acid (Glu), leucine (Leu), NA and phenylalanine (Phe) in chicory xylem saps showed the greatest increases. The data indicate that induced synthesis of some free amino acids as a specific and proportional response to Cu treatment. For a single complexation amino acid, the solution Cu2+concentration vs pH titration curve for NA at 0.06–0.07 mM was most similar, closely followed by His at 0.5–0.6 mM, to the solution Cu2+concentration behaviour in both tomato and chicory xylem sap. It is concluded that increased Cu concentrations in the rooting media induced selective synthesis of certain amino acid which include NA, His, Asn and Gln which have high stability constants with Cu. NA and His have the highest binding constants for Cu and the concentrations of NA and His in chicory and tomato xylem saps can account for all the bound Cu carried in the sap.
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  • 27
    ISSN: 1573-5036
    Keywords: biological control ; Paecilomyces lilacinus ; Pseudomonas aeruginosa ; root-knot nematode ; root-infecting fungi ; tomato
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Efficacy of Pseudomonas aeruginosa alone or in combination with Paecilomyces lilacinus was evaluated in the control of root-knot nematode and root-infecting fungi under laboratory and field conditions. Ethyl acetate extract (1 mg/ml) of P. lilacinus and P. aeruginosa,respectively, caused 100 and 64% mortality of Meloidogyne javanica larvae after 24 h. Ethyl acetate fractions of biocontrol agents were more effective than hexane extracts in the suppression of M. javanica larvae, indicating that active nematicidal compounds are intermediary in polarity. In field experiments, biocontrol fungus and bacterium significantly suppressed soilborne root-infecting fungi including Macrophomina phaseolina, Fusarium oxysporum, Fusarium solani, Rhizoctonia solani and Meloidogyne javanica, the root-knot nematode. P. lilacinus parasitized eggs and female of M. javanica and this parasitism was not significantly influenced in the presence of P. aeruginosa. P. aeruginosa was reisolated from the inner root tissues of tomato, whereas P. lilacinusdid not colonize tomato roots.
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  • 28
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    Plant and soil 226 (2000), S. 113-116 
    ISSN: 1573-5036
    Keywords: aluminium ; root cells ; stress adaptation ; structural response ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Plant cells respond to a certain stress factor in different ways depending on their developmental stage and type of tissue. Structural damage may be severe or even lethal in individual cells within a tissue that exhibits moderate or no effects of stress. In the case of aluminium toxicity, detailed observations of root tips of 3 day old Zea mays L., cv. TO360 seedlings revealed differences in the response of some cells. Two different structural changes appeared within root epidermis just behind the root cap. Cells with dark and shrunken cytoplasm occurred next to swollen cells with preserved cellular compartments. Within the root cortex, individual cells or a few cells of a file have severely damaged cytoplasm, in contrast to almost undisturbed cytoplasm of adjacent cells. Such extremely sensitive cells appear irregularly within the root apex. Their structural similarity with cells that are observed after a hypersensitive response in infected plant tissues suggests a role to accumulate aluminium, in order to allow the surrounding tissue to survive the stress.
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  • 29
    ISSN: 1573-5060
    Keywords: Host plant resistance ; heat-sensitivity ; root-knot nematodes ; tomato ; virulence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Accessions of Lycopersicon peruvianum complex and their F1progenies were screened for genotype specific resistance to Mi-1-avirulent M. incognita and M. javanica biotypes at25 °C and at 32 °C (a temperature at which Mi-1resistance is not expressed), and to Mi-1-virulent M.incognita at 25 °C. All entries of the L. peruvianumChotano-humifusum race accessions LA2157 and LA2334 were resistantto Mi-1-avirulent biotype at 25 °C and at 32 °C,indicating that the accessions are homozygous for the heat-stableresistance. The L. peruvianum Maranon race accessions LA1626,LA1708, LA2172, LA2185, LA2326 and LA2328 segregated for heat-stableresistance to Mi-1-avirulent biotype. The F1 progeny tested ofLA392 × LA2157, LA2334 × LA2157, LA2328 × LA2326,LA2328 × LA2185, LA1708 × LA2328 andLA1626 × LA2172 were resistant to Mi-1-avirulent biotype at32 °C. There were differences in the segregating accessions andF1 hybrids for expression of heat-unstable and heat-stable resistanceto Mi-1-avirulent Meloidogyne spp. The L. peruvianumLA392 and LA2163 and L. chilense LA1968, LA1972, LA2404, LA2405,LA2406, LA2748, LA2930, and the L. peruvianum × L.chilense hybrids were homozygous susceptible with all entries testedsusceptible at 32 °C. Cuttings of these L. peruvianumaccessions and their F1 progenies were susceptible to Mi-1-virulent M. incognita biotype at 25 °C.
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  • 30
    ISSN: 1573-5060
    Keywords: Andean maize ; cold tolerance ; germplasm evaluation ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Cold in the initial growth stages is an important stressfactor for maize grown in regions with a temperate climate,particularly in case of early sowing. Sources of tolerancehave been identified in adapted genotypes, but promisinggenes for cold tolerance should also be found in materialdeveloped under the lower-temperature margins of the cropdistribution. This research was conducted in order to testAndean maize accessions for cold tolerance expressed duringboth the heterotrophic and early autotrophic growth stages.Experiments were conducted in controlled environments tostudy cold tolerance traits (germination %, germinationindex and plant growth rate) at continuous 10°C (heterotrophic growth) and at varying 10–16°C (autotrophic growth). An experiment was also performed inthe field with early sowing (both heterotrophic and autotrophic growth). In each experiment, a control trialwas conducted in more favourable conditions (i.e. continuous25°C in a controlled environment or late planting inthe field) so that cold tolerance traits could also beexamined as the ratio between the stress and the controltrial. None of the accessions was superior for all coldtolerance traits. However, several Andean maize accessionsoutperformed the US Corn-belt hybrid checks for one or moretraits, both in heterotrophic and autotrophic growth. Overall, BOZM 855, PMS 636, Poblacion D, Poblacion E andBOZM 696 were the best accessions, suggesting that they canbe a promising source of genes for improving cold toleranceof adapted maize genotypes.
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  • 31
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    Euphytica 115 (2000), S. 149-158 
    ISSN: 1573-5060
    Keywords: Maize ; mature plant resistance ; Striga hermonthica ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Twelve maize genotypes with different degrees of resistance were evaluated in plots inoculated with seeds of the phytoparasite Striga hermonthica (Del.) Benth. and in Striga-free (control) plots for three seasons between 1991 and 1993. Resistant genotypes, although showing similar levels of underground infection as susceptible 9 weeks after maize planting (WAP), had significantly fewer emerged parasitic plants and sustained lower damage. Host damage was not determined by the severity of infection. Percent height and dry matter reductions increased from 3 to 6 WAP for resistant and susceptible genotypes. While percent height and dry matter reductions for resistant genotypes declined at 9 and 12 WAP, susceptible genotypes either maintained or increased their levels of damage. Correlation between the severity of height and dry matter reductions at the vegetative (3 and 6 WAP) and reproductive (9 and 12 WAP) stages of maize growth were not significant, indicating that damage at early stages of growth cannot be used to predict mature plant response. Maize damage score (1–9) at 8 WAP, a non destructive and composite shoot indicator of host performance under Striga infestation, was significantly correlated (r = 0.88, r = 0.82; p 〈 0.01) to the level of shoot reduction at mature plant stages. Emerged Striga count at 8 WAP was significantly correlated (r = 0.98, p 〈 0.01) to the count at 10 WAP, the time when parasite emergence was highest. Under high and uniform infestation, mature plant resistance can be detected at 8 WAP, the onset of flowering in maize.
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  • 32
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    Plant growth regulation 32 (2000), S. 295-305 
    ISSN: 1573-5087
    Keywords: Cold stress ; Immunolocalization ; Phaseolus vulgaris ; Zeatin O-glycosyltransferase ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Zeatin O-glycosides have been reported as inactive and stable storage forms of cytokinins whose concentrations increase in cold stressed plants. Zeatin O-glycosides accumulation in developing bean seeds has been correlated with an increase of zeatin O-glycosyltransferase , which is specific to trans-zeatin, and catalyzes the conjugation of zeatin O-glycosides. When Phaseolus vulgaris and Zea mays seedlings were grown for 3 days at 25 and then incubated at 4 or 10 for 6 days no further growth was observed in roots. Hypertrophy was observed in the root tips of both species. In shoot-hypocotyl complexes, in contrast, growth occurred when seedlings were incubated at 10 . Western analysis, with Mabs specific to zeatin O-glycosyltransferase, detected antigenically related proteins in roots, shoot tips and cotyledons after seedlings were cold stressed for 1–6 days at 4 or 10 . Immunolocalization, of both maize and bean root sections grown at 25 revealed antigenically related proteins that were detected at low levels in cortical cells. The signal intensified upon cold stress. The localization of zeatin O-glycosyltransferase in Z. mays root tips was directly comparable to the distribution of the zeatin O-glycosides. The enzyme was detected in the nucleus, cytoplasm, and closely associated with the plasma membrane and in the cell wall of Z. mays root cells. Southern analysis suggested that more than one gene in Z. mays that were homologous to zeatin O-glycosyltransferase in P. vulgaris. Zeatin O-glycosyltransferase may be involved in modulation of cytokinins under cold stress.
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  • 33
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    Plant growth regulation 32 (2000), S. 219-230 
    ISSN: 1573-5087
    Keywords: Arabidopsis thaliana ; arbuscular mycorrhiza ; biosynthesis ; indole-3-acetic acid ; indole-3-butyric acid ; regulation ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Within the last ten years it has been established by GC-MS thatindole-3-butyric acid (IBA) is an endogenous compound in a variety ofplant species. When applied exogenously, IBA has a variety of differenteffects on plant growth and development, but the compound is stillmainly used for the induction of adventitious roots. Using moleculartechniques, several genes have been isolated that are induced duringadventitious root formation by IBA. The biosynthesis of IBA in maize(Zea mays L.) involves IAA as the direct precursor. Microsomalmembranes from maize are able to convert IAA to IBA using ATP andacetyl-CoA as cofactors. The enzyme catalyzing this reaction wascharacterized from maize seedlings and partially purified. The invitro biosynthesis of IBA seems to be regulated by several externaland internal factors: i) Microsomal membranes from light-grownmaize seedlings directly synthesize IBA, whereas microsomal membranesfrom dark-grown maize plants release an as yet unknown reaction product,which is converted to IBA in a second step. ii) Drought and osmoticstress increase the biosynthesis of IBA maybe via the increaseof endogenous ABA, because application of ABA also results in elevatedlevels of IBA. iii) IBA synthesis is specifically increased byherbicides of the sethoxydim group. iv) IBA and IBA synthesizingactivity are enhanced during the colonization of maize roots with themycorrhizal fungus Glomus intraradices. The role of IBA forcertain developmental processes in plants is discussed and somearguments presented that IBA is per se an auxin and does notact via the conversion to IAA.
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  • 34
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    Plant growth regulation 32 (2000), S. 151-155 
    ISSN: 1573-5087
    Keywords: ATP production ; ATPase ; auxin ; membrane vesicles ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Microsomal membrane vesicles and purified plasma membranevesicles obtained from coleoptiles of maize (Zea mays L.) weresubjected to pH shifts from pH 7.8 to 4.7. In the presence of ATPaseinhibitors such as vanadate, net accumulation of radiolabelled butyricand indole-3-acetic acid (IAA) remained higher than in controls. When 2min after the pH shift, at 4°C, the microsomal vesicles weredenatured the amount of ATP could be determined using theluciferin/luciferase assay. Significantly increased ATP production overcontrol values – no pH-shift or ionophore treatment – wasfound. Therefore, such vesicles might produce ATP for in vitrotransport processes such as auxin efflux.
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  • 35
    ISSN: 1573-5060
    Keywords: interplot interference ; Lycopersicon esculentum ; Lycopersicon pennellii ; Lycopersicon pimpinellifolium ; spider mites ; Tetranychus urticae ; tomato
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract We have previously found an accession of Lycopersicon pimpinellifolium (Jusl.) Mill. (`TO-937') that appeared to resist attack by the two-spotted spider mite (Tetranychus urticae Koch). L. pimpinellifolium is a very close relative of the cultivated tomato (Lycopersicon esculentum Mill.) and thereby a potential source of desirable traits that could be introgressed to the crop species. The objective of this study was to investigate the genetics of the resistance present in `TO-937'. Resistance to infestation by the spider mite was quantified in 24-plant plots of L. pimpinellifolium accessions `TO-937' and `PE-10', L. pennellii accession `PE-45', L. esculentum cultivars `Moneymaker', `Roma' and `Kalohi' (reported to be partially resistant: Stoner & Stringfellow, 1967), and the interspecific F1 cross, L. esculentum `Moneymaker' × L. pimpinellifolium `TO-937'. Only `TO-937', the F1, and`PE-45' were found to be resistant. Resistance of `TO-937' was complete when evaluated in two small greenhouses completely planted with `TO-937' so as to simulate the genotypic homogeneity usual in commercial crops. Generations (P1, P2, F1, F2, BC1P1, and BC1P2) of a P1 (susceptible) × P2 (resistant) cross (`Moneymaker' × `TO-937') were studied for resistance in a single-plant per plot design. Resistance of `TO-937' was inherited with complete dominance and appeared to be controlled by either two or four genes according to whether segregation in the F2 or the BC1P1, respectively, were considered. However, calculation of the number of genes involved in the resistance was complicated by negative interplot interference due to the high frequency of resistant genotypes within most of the generations.
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  • 36
    ISSN: 1573-5036
    Keywords: chicory ; Cu distribution ; Cu uptake ; free Cu2+ ; tomato ; xylem sap
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The uptake and distribution of copper was examined in chicory (Cichorium intybus L. cv. Grasslands Puna) and tomato (Lycopersicon esculentumMill. cv. Rondy) plants grown in a Nutrient Film Technique System (NFT) with addition of 0.05, 5, 10 and 20 mg Cu L-1. Biomass production of shoots and roots of both chicory and tomato was strongly depressed by Cu concentrations higher than 5 mg Cu L-1 in the rooting media. Although Cu concentrations in both shoots and roots of both species increased with increasing Cu concentrations in the rooting media, the increase in roots was very much greater than that in shoots, in which the range of concentrations was small. A large proportion of total Cu uptake was retained by roots except when plants were grown in solution Cu concentrations of 0.05 mg Cu L-1. Copper retention by roots limited Cu translocation to xylem and shoots. Copper adsorption by the root appears to buffer against increases of Cu in the rooting media. A cupric-sensitive electrode used in conjunction with total Cu analysis by graphite furnace atomic absorption spectrophotometry (GFAAS) indicated that more than 99.6% of total Cu in xylem sap was in a complexed form. Large differences between measured and predicted Cu accumulation by shoots of tomato (0.134–0.243 mg Cu plant-1, 0.660–4.274 mg Cu plant-1, respectively) and chicory (0.095–0.203 mg Cu plant-1, 0.626–1.620 mg Cu plant-1, respectively) suggest that some xylem transported Cu is recirculated to roots via the phloem.
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  • 37
    ISSN: 1572-9680
    Keywords: A,nus rubra ; hedgerow intercropping ; Robina pseudoacacia ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The objective of this study was to determine crop and tree productivity in several alley cropping planting patterns. The four- year study was conducted in western Oregon, United States and involved irrigated sweet corn (Zea mays) intercropped between hedgerows of red alder (Alnus rubra) and black locust (Robina pseudoacacia). Three alley cropping planting patterns with variable plant populations and tree-crop proximity were tested with each tree species in a randomized block design. Space available to trees and crops determined yield of both plant components. High crop yield coincided with low pruning yield, and vice versa. Compared to monocropping, yield reductions in traditional alley cropping planting patterns with widely spaced, double tree rows ranged from 5% to 15%. A. rubra and R. pseudoacacia coppiced readily and produced 0.9 to 4.7 tons of dry matter pruning biomass per growing season, depending on planting pattern and year. A. rubra yield continually increased during the trial, while the ability of R. pseudoacacia to produce green manure after frequent coppicing appeared to weaken. After four years, soil organic matter was 4 to 7% higher in the topsoil of an alley cropping system compared to a monocropping system. However, continuous growing of sweet corn resulted in decreased soil organic matter levels in both cropping systems compared to original levels. Crop yield reductions and the need for additional management inputs constrain the implementation of alley cropping in temperate climates. Only if benefits other than minor soil fertility improvements are realized is alley cropping a feasible alternative in temperate climate regions.
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  • 38
    ISSN: 1871-4528
    Keywords: Solanin ; Chaconin ; Magnesium ; Kalium ; Stickstoff ; Solanum tuberosum L. ; Phytophthora infestans ; Feldversuch
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Description / Table of Contents: Summary Field experiments were carried out for three years to study the effect of various magnesium, potassium and nitrogen fertilization rates on two medium-early edible potato cultivars. Additionally, one of the experimental areas was sprayed againstPhytophthora infestans to ascertain the effect of fungicides on the content of total glycoalkaloids (TGA) in potato tubers after harvest and after six months of storage. The applied fungicide treatments increased total glycoalkaloids (TGA) of potato tubers (Fig. 4). Fertilization with mineral nitrogen caused different reactions in both cultivars. There was a tendency for cv. Beryl to accumulate more glycoalkaloids with increasing nitrogen fertilization rates, while the opposite was observed for cv. Mila (Fig. 7). Fertilization with potassium and magnesium did not affect the results. On the basis of these results there was no conclusive evidence that the TGA content in the tubers was dependent on cultivar or on the weather during the growing season (Figs 1,2 and 3). The TGA content increased during storage, independently of previous treatments, (Figs 4–7).
    Notes: Zusammenfassung Es wurden Feldversuche in drei Jahren mit zwei Speisekartoffelsorten, verschiedenen Mengen an Mineraldüngern und der Anwendungen eines Pflanzenschutzmittelns gegenPhytophthora infestans angelegt. Die Knollen wurden direkt nach der Ernte sowie nach einer sechsmonatigen Lagerung auf Glykoalkaloidgehalt untersucht. Zwischen den Sorten treten statistisch gesicherte Unterschiede im Gehalt an Glykoalkaloiden auf. Die Anwendung von Pflanzenschutzmitteln während der Vegetation erhöht den Gesamtgehalt an Glykoalkaloiden (TGA) in den Kartoffelknollen kurz nach der Ernte. Eine variierte Mineraldüngung hat keinen statistisch signifikanten Einfluss auf den TGA-Gehalt in den Proben kurz nach der Ernte, N- und K-Düngung verändern diesen jedoch im Laufe der Lagerung. Unabhängig von den übrigen Bedingungen erhöht sich der TGA-Gehalt in diesem Versuch während der Lagerung im Mittel von 5,8 auf 7,7 mg/100g Frischsubstanz.
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  • 39
    ISSN: 1871-4528
    Keywords: growth regulator ; sucrose ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Ancymidol-induced in vitro tuberisation under different photoperiodic regimes (dark, SD=8 h, LD=16 h) and sucrose concentrations (2, 4, 6 and 8%) in cv. Jaerla (early) and cv. Baraka (late) was studied. Tuberisation was scored after 4 (dark) or 8 (light) weeks. Ancymidol significantly increased tuberisation under LD-SD for any sucrose concentration in both cultivars. Ancymidol also significantly increased tuberisation under LD-dark for 6% sucrose in both cultivars. Tuberisation in cv. Jaerla was significantly higher than in cv. Baraka for any photoperiodic treatment in the presence or absence of ancymidol with 4, 6 or 8% sucrose. The photoperiod SD-SD resulted in the higher level of tuberisation for any combination of sucrose, cultivar and ancymidol. The possible role of ancymidol is discussed.
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  • 40
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    Potato research 42 (1999), S. 611-617 
    ISSN: 1871-4528
    Keywords: dormancy ; potato ; losses ; Solanum tuberosum L. ; seed potato production
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Microtubers can be stored longer, transported and handled easier than plantlets, but they have some disadvantages related to long dormancy. Dormancy, number of sprouts per tuber and loss of microtubers under different storage temperatures were studied. Microtubers of four genotypes originated from different tuberization treatments (photoperiod combinations) were observed. We found that dormancy depended on cultivar and — in some cases — on the photoperiod treatment applied during tuberization. Generally, the dormacy was long and was greatly elongated by low storage temperature. One of the photoperiod treatments shortened while the other treatment prolonged the rest-period compared to the control, maybe due to a change in temperature accompanying the change in daily light (photoperiod combination). Besides, these treatments affected the number of sprouts per tuber. There was no significant difference in duration of dormancy between different tuber-size groups, but the loss increased significanctly with a decrease in tuber size. Based on this information we can use microtubers more effectively in the seed potato production programme.
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  • 41
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    Potato research 42 (1999), S. 101-105 
    ISSN: 1871-4528
    Keywords: late blight ; testing methods ; electrolyte leakage ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The resistance of ten potato cultivars (Agria, Ajax, Désirée, Liseta, Kennebec, Majestic. Monalisa, Prima, Spunta and Tonda di Berlino) toPhytophthora infestans was analyzed in vitro using 8 fungal strains. An assay based on electrolyte leakage was used for screening leaves and tuber tissues with fungal culture filtrates. With almost all cultivars the resistance of leaves did not correlate with the resistance of tubers. Cv. Ajax appeared the least susceptible in both leaf and tuber tests, while the cv. Prima was the most susceptible in tuber tests.
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  • 42
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    Potato research 42 (1999), S. 229-240 
    ISSN: 1871-4528
    Keywords: earliness ; planting season ; Mediterranean area ; off-season production ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary In Italy, the early potato cultivars of greatest economic significance are those grown off-season, in a cycle which is generally much earlier than the typical spring-summer cycle. Of the area given over to early potatoes in Italy, more than 90% is in the southern regions. The economic value of this production is due to its extraseasonality, which allows much of the early potato harvest to be sold on foreign markets. In Sicily, more than 5000 ha of potato are grown, with a high frequency of potato crops on small plots. Early potatoes are often rotated with various fruits and vegetables, and the length of the cycle is variable, from 100 to 140 days. Choosing the most suitable cultivar is the most complex aspect of early potato growing. Of the criteria used, tuber growth rate has shown most validity. In Sicily two cultivars are mainly grown: Sieglinde and the more recent but well-established Spunta. Agricultural techniques used for early potato cultivation vary depending on the area. An overview of the agronomic practices used in different areas is given in this paper.
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  • 43
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    Potato research 42 (1999), S. 381-395 
    ISSN: 1871-4528
    Keywords: agronomy ; breeding ; pathology ; physiology ; Solanum tuberosum L. ; storage ; utilisation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary This contribution presents highlights of the oral and poster presentations in the various sessions of the 14th Triennial Conference of the European Association for Potato Research, held in Sorrento, Italy, May 1999. It is based on the reports of the session chairpersons and the book of abstracts. The paper reports the progress made in many aspects of potato research, but also stresses the need for further collaborative work, especially in the fields of molecular physiology, marker assisted breeding, control of late blight, potato tuber moth and other pests and diseases, stress physiology and stress resistance, and sustainable cropping systems with both short and long cycle potato crops.
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  • 44
    ISSN: 1871-4528
    Keywords: Solanum tuberosum L. ; tuberisation ; extensin ; acyl carrier protein thioesterase ; high mobility group protein ; gene expression ; plant development
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary In screening to isolate a full-length copy of a previously isolated cDNA clone, a further three cDNAs were also isolated from a library prepared from sub-apical swelling-stolon tissue of potato (Solanum tuberosum L.). Sequence analysis showed these clones to be similar to extensin-like protein genes, acyl carrier protein thioesterase genes and high mobility group protein genes, respectively. A further cDNA, isolated by subtractive hybridisation, was similar to a tomato cDNA previously isolated on the basis of its down-regulation following nematode infection. While all the newly isolated genes were expressed in swelling stolons, for most, maximal expression was seen to be in stem tissue. Possible roles for these genes in the development of potato plants are discussed, as is the significance of gene expression in stems and stolons to the process of tuberisation.
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  • 45
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    Potato research 42 (1999), S. 89-93 
    ISSN: 1871-4528
    Keywords: analysis ; HPLC ; β-glucoside ; 1,2-dihydro-3,6-pyridazinedione ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The method of Vadukul (1991) for determining maleic hydrazide (MH) was modified and gave recoveries of free MH of 89%±4%. The values recorded on individual tubers ranged from 2–14 mg kg−1. Maleic hydrazide was evenly distributed throughout the tuber (peel, outer and inner flesh) but concentration increased slightly as tuber size increased. The concentration of free MH decreased from 7 to 3 mg kg−1 over the storage period of 5 1/2 months. Acid hydrolysis released substantial amounts of MH particularly from older potatoes (13 mg kg−1) compared with 6 mg kg−1 from new potatoes, implying that free MH is gradually converted to a bound form with time after treatment. No evidence was found for the presence of a β-glucoside of MH.
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  • 46
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    Potato research 42 (1999), S. 241-264 
    ISSN: 1871-4528
    Keywords: global distribution ; prospects ; diversification ; specialization ; price risk ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary We examine the changing character of supply and demand for potatoes over time and space with an eye towards implications for agricultural research. Diversification in consumption and specialization in production are our organizing themes. The foundation for comparative analysis is a map of the global distribution of potato growing area. We highlight the adverse impact of price risk on specialization and discuss several sources of uncertainty that condition the size but not the direction of major trends.
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  • 47
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    Potato research 42 (1999), S. 499-504 
    ISSN: 1871-4528
    Keywords: Solanum tuberosum L. ; microtuber ; liquid medium ; temporary immersion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary CIRAD developed a new apparatus for plant tissue culture, using temporary immersion in a liquid medium. This apparatus was adapted to the microtuber production in potato. The procedure is as follows: single node cultivation on MS medium containing 30 g/l sucrose in the light for 2 weeks, induction of microtuberisation with 80 g/l sucrose over a 2 week period in the light, followed by a further 6 weeks in the dark. All experiments were performed at 20 °C. The basic vessel had a capacity of approximately 11;30 nodes were cultivated per vessel. Depending on the cultivars tested (Bintje, Ostara and Désirée) 47 to 115 microtubers were harvested per vessel. Between 30 and 60% of the microtubers weighted over 0.5 g and between 10 and 40% over 0.8 g. Sprouting is still under investigation. Preliminary results indicate that the dormancy period was relatively short and several stems were obtained per microtuber. These results seem to be better than those usually reported. Only one simple protocol has been tested and further improvements are probably easy to obtain.
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  • 48
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    Potato research 42 (1999), S. 585-591 
    ISSN: 1871-4528
    Keywords: Solanum tuberosum L. ; microtubers ; acetic acid ; propionic acid ; asscorbic acid ; salicylic acid ; acetylsalicylic acid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Potato microtubers are usually induced in media containing growth regulatory, typically cytokinins and growth retardants. However, since these substances may imbalance the physiology of the cultured explants and cause adverse carry-over effects on the subsequent performance of the microtubers, the potential acid-induction of in vitro-mass tuberization was investigated as an alternative. For this purpose, a range of explant types (stolons, single-node or apex-containing multinodal sections), organic acids (acetic, propionic, ascorbic, acetylsalicylic or salicylic acid), and photoperiods (continuous dark, 8 or 16 h photoperiod) were established. Gellified medium or raft membranes on liquid medium were also tested. Although variations due to explant type, photoperiod, organic acid supplemented, and medium type were found, all organic acids tested under the different experiments caused tuberization. Multiple tuber formation or bigger tubers did not develop on multinodal explants. In terms of tuberization rate and mean tuber weight, gellified medium performed better than liquid medium with rafts. The recently established role of the salicylic and acetylsalicylic acids on tuberization is corroborated by our system. The results with the acetic, propionic and ascorbic acids show that in vitro hormone-free tuberization can be easily and rapidly achieved.
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  • 49
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    Potato research 42 (1999), S. 73-78 
    ISSN: 1871-4528
    Keywords: growth parameters ; K+/Na+ ratio ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Increased potassium (K) fertilization of saline soils has been implicated in alleviating salt stress in plants. We examined whether varying K concentrations in Murashige & Skoog (MS: 1962) basal medium could affect salt (NaCl) stress in micropropagated potatoes. Plantlets of cvs Sierra and Russet Burbank were evaluated after 1 month of growth in a medium containing 0. 40, or 80 mM NaCl and 6,20, or 30 mMK. The medium K was adjusted using KNO3 while total nitrogen was kept constant using NH4NO3. Growth parameters were less affected in Sierra than Russet Burbank, and roots were less affected than shoots, as the medium salinity increased. Tissue Na levels were greater when the medium K was 6 mM compared with 20 mM MS control. The medium K concentration 50% greater than MS control did not promote growth and did not limit tissue Na levels. While this should be confirmed by field assessment, our results suggest that while K deficiency promotes salt damage, its addition beyond the usual fertilizer recommendations is not beneficial in alleviating salinity stress.
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  • 50
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    Potato research 42 (1999), S. 607-610 
    ISSN: 1871-4528
    Keywords: seed production ; Greece ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Large scale, commercial production of potato minitubers, cvs Spunta, Jaerla and Kennebec, has been carried out in VITRO HELLAS S.A. since 1995, according to protocols based on in vitro methods. Apical meristems were cultured on MS medium supplemented with 1 μM IBA, 20 g/l sucrose and 6 g/l agar (pH 5.8). Subculture was carried out every 15 days. Multiplication rate was 4–5 per cycle. Self-rooted microplants were transferred into screen houses (200 plants/m2) in a mixture of peat and perlite 1∶1 (v/v). Cultivation period was 15 August to 15 November each year. During the period 1995–1997, the number of minitubers produced/plant was 2.07 for cv. Spunta, 1.85 for cv. Jaerla and 2.52 for cv. Kennebec and their average weights were 10.8 g, 10.9 g and 9.8 g, respectively. The percentage of minitubers〈10 mm in diameter was 2%, 50.1% were 10–20 mm and 47.9% were〉20 mm.
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  • 51
    ISSN: 1871-4528
    Keywords: cultivar ; virus diseases ; nematodes ; ground cover ; physiological age ; seed production ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary In Argentina, different areas are suitable for seed potato production: however, each has particular problems, mainly related to different pest and diseases. Tierra del Fuego Island is well isolated from traditional potato growing areas. Therefore, it was tested for its potential for seed production. The cultivars Achatt. Mailén INTA. Pampeana INTA and Spunta were grown in Río Grande, San Pablo and Ushuaia from 1991–1994. Nematode presence and aphid population dynamics were recorded. Average tuber yield ranged from 20.1–37.6 t ha−1. After three years PVY and PLRV remained low (0–1% for different cultivars and locations). Moreover, seed tubers obtained were physiologically young. Long days, early frosts and strong winds may limit tuber yield in some years. The island can be considered as an ecological “safe haven” and is very suitable to obtain healthy and physiologically adequate seed potatoes.
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  • 52
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    Potato research 42 (1999), S. 25-29 
    ISSN: 1871-4528
    Keywords: chlorpropham ; particulates ; dusts ; solvents ; ignition source ; explosive limits ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary An appraisal was undertaken of the key factors involved in explosion and combustion processes mainly associated with the fogging of chlorpropham formulations into potato stores. The key factors considered are source of ignition, solvents, explosive limits of solvents, the presence and atmospheric concentrations of particulate clouds and the role of particulate material in dust explosions. Also the sequence of events that takes place in a dust explosion, including critical concentrations of dust required to initiate the reactions involved and the particular relevance of the above events to the behaviour of chlorpropham fogs both at the time of application and when distributed throughout a store. The relevance of fine dust already present in the store to the initiation of explosions, particularly secondary explosions, which are considered to be a major cause of concern due to their severity, is also emphasised.
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  • 53
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    Potato research 42 (1999), S. 95-99 
    ISSN: 1871-4528
    Keywords: analysis ; HPLC ; filter paper model ; Diels-Alder reaction ; 1,2-dihydro-3,6-pyridazinedione ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A method used for estimating extractable maleic hydrazide (MH) concentrations in fresh potato material, concentration range 5–17 mg kg−1, was found not to be suitable for processed potato products (10–33% recoveries) although, boiling potato pieces enhanced recovery by 20%. Each step of the determination was examined and a modified procedure developed with particular emphasis on the extraction of MH from the dried potato matrix, and the quality of the HPLC column used. Potato slices and model systems based on filter papers plus additives were used. Recoveries from fried potato slices were 74±6%. Based on the effect of glucose in reducing extractable MH recoveries, it is suggested that the remainder of the MH (20–25%) is converted into a conjugated structure on reaction with dehydrated sugar (Diels-Alder reaction).
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  • 54
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    Potato research 42 (1999), S. 215-221 
    ISSN: 1871-4528
    Keywords: potato virus Y ; strain differentiation ; RFLP ; potato tuber necrotic ringspot disease ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A procedure for differentiating PVYNTN from PVYN is described and is based on the unique cleavage of their respective PCR products with strain specific restriction endonucleases. The PCR products corresponding to the 5′ end of the N and NTN strains of PVY were cloned and sequenced, and a restriction map was constructed which included common enzymes that were used for the differentiation of PVYNTN. Unique, single cleavage of PCR products derived from the 5′ end of the PVYNTN genome by Nco I, and that of the N-strain of PVY by Bgl II restriction endonuclease were demonstrated. The specific digestion patterns in polyacrylamide gel were used for the unequivocal differentiation between the N and NTN strains of the virus. Both single and mixed infections were detected in field samples of potatoes using this procedure.
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  • 55
    ISSN: 1871-4528
    Keywords: wild species ; gene introgression ; heat stress ; drought stress ; frost stress ; biotic stresses ; off-season production ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary In the Mediterranean area the potato is a very important crop and can be cultivated throughout the year. However, tuber yields are generally much lower than those in Northern European countries. This is because the environmental and agro-economic conditions are different from those of Northern countries where most cultivars were developed. We feel that the objective for the “new Mediterranean potato” must be the availability of potato cultivars for each environment and for each planting season. Breeding programmes should focus on improving potato production within a specific agro-ecological Mediterranean area rather than improving crop production across areas. This paper reports aspects of potato breeding and physiology related to resistance to stress conditions in the Mediterranean area, with particular emphasis given to resistance to abiotic (heat, drought and frost) as well as biotic stresses. We also discuss the potential to produce seed tubers suitable for potato cultivation in the Mediterranean area.
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  • 56
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    Potato research 42 (1999), S. 279-282 
    ISSN: 1871-4528
    Keywords: late blight ; mating types ; sexual recombination ; Solanum tuberosum L. ; diversification ; aggressiveness ; migration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Since the early 1980s and continuing through the end of the 20th century, potato late blight caused byPhytophthora infestans has become noticeably more problematic throughout the world. Exotic strains of the pathogen are largely responsible for the increased problems. The new strains were initially detected in Europe, but subsequently they have been detected in Asia, the Middle East, South America and North America. Populations in the Middle East and South America may represent secondary migrations from Europe. Several independent migrations have occurred such that migrant populations in North America are very different from those in Europe. Also, population structures ofP. infestans are different in different worldwide locations. In some locations the migrant strains are resistant to metalaxyl, but in other locations either migrant or indigenous strains may be resistant. In most locations, the migrant strains are more aggressive than the previous indigenous strains.
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  • 57
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    Potato research 42 (1999), S. 489-498 
    ISSN: 1871-4528
    Keywords: Solanum tuberosum L. ; microtubers ; nodal cuttings ; in vitro tuberization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A tissue culture technique is described in which nodal cuttings ofSolanum tuberosum L. are induced to form usable microtubers in order to produce high health status of the seed potato genotypes cultivated in Switzerland.
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  • 58
    ISSN: 1871-4528
    Keywords: genes ; transgenic plants ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Continuing study of the potato plant's response to stressful conditions has led to the identification of a large number of plant genes whose expression, is regulated by external stimuli. Stress-induced genes can be broadly divided into functional or regulatory genes. To the first category belong genes encoding proteins or enzymes of plant metabolic pathway, of molecules involved in repairing cellular damages and/or indispensable for restoring a new cellular homeostasis compatible with the external conditions. The other class includes genes primarily involved in the perception and/or intracellular transduction of the stress signal, such as kinases, phosphatases or transcription, factors. The research objectives in the field of plant stress tolerance has recently evolved from a mere cloning and description of stress-induced genes to the design of the best strategy of producing transgenic plants tolerant to environmental constraints. It is well known that stress tolerance is a complex trait, requiring the coordinated regulation of a network of genes that act synergistically and additively. At best, manipulation of one single down-stream gene may contribute only partially to the tolerance of the transgenic plants. Recent studies have shown that it is feasible to regulate the level of expression of many down-stream stress-induced genes in a coordinated fashion by regulating the expression of genes encoding transcription factors able to bind DNA motifs in the promoter of stress-induced genes. However, the constitutive high level of expression of transcription factors often causes detrimental phenotypic effects. This drawback could be bypassed by putting genes for transcription factors under the control of inducible promoters. In this way, endogenous tolerance genes are activated only when the stress event occurs, minimizing the negative pleiotropic effect. Novel technology (reverse genetics, DNA microarrays, mRNA differential display, T-DNA tagging, complementation and over-expression of plant cDNA in yeast as model for cellular stress tolerance), improvement of genetic transformation techniques (multiple gene transfer, gene targeting by homologous recombination) as well as a better efficiency of foreign gene expression (discovery of plant promoters with cell-specific, tissue-specific, developmental stage-specific, and/or inducible patterns of expression) will give a tremendous impulse to produce stress tolerant commercial cultivars of the main crops through genetic engineering.
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  • 59
    ISSN: 1572-9788
    Keywords: cucumber mosaic virus ; tomato ; transgenic resistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract For the production of broad commercial resistance to cucumber mosaic virus (CMV) infection, tomato plants were transformed with a combination of two coat protein (CP) genes, representing both subgroups of CMV. The CP genes were cloned from the CMV-D strain and Italian CMV isolates (CMV-22 of subgroup I and CMV-PG of subgroup II) which have been shown to produce severe disease symptoms. Four plant transformation vectors were constructed: pMON18774 and pMON18775 (CMV-D CP), pMON18831 (CMV-PG CP) and pMON18833 (CMV-22 CP and CMV-PG CP). Transformed R0 plants were produced and lines were selected based on the combination of three traits: CMV CP expression at the R0 stage, resistance to CMV (subgroup I and/or II) infection in growth chamber tests in R1 expressing plants, and single transgene copy, based on R1 segregation. The results indicate that all four vector constructs generated plants with extremely high resistant to CMV infection. The single and double gene vector construct produced plants with broad resistance against strains of CMV from both subgroups I and II at high frequency. The engineered resistance is of practical value and will be applied for major Italian tomato varieties.
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  • 60
    ISSN: 1572-9788
    Keywords: cucumber mosaic virus ; tomato ; transgenic ; virus resistance ; field
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Since the summer of 1993, transgenic tomato plants expressing the coat protein (CP) genes of cucumber mosaic cucumovirus have been tested under field conditions to assess the level of resistance and agronomic performance. Trials were performed in different areas in Italy and the target virus in the majority of tests was spread naturally by the indigenous aphid populations. Twenty-three homozygous lines of variety UC82B, transformed to contain four different CP genes of CMV, were evaluated. The lines were preselected for CP expression, single gene copy, and virus resistance in growth chamber experiments. In general, CMV resistance was confirmed under field conditions though resistance in the field was less effective than what was observed in growth chamber experiments. The resistance observed in multi-year and multi-location experiments is of commercial value for several of the most resistant lines. Engineered resistance upon transfer to Italian varieties by breeding or direct transformation will be used in tomato production in Italy or elsewhere.
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  • 61
    ISSN: 1573-5036
    Keywords: flax ; nitrate dissimilation ; Pseudomonas ; rhizosphere ; soil ; tomato
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The distribution of nitrogen dissimilative abilities among 618 isolates of fluorescent pseudomonads was studied. These strains were isolated from two uncultivated soils (C and D; collected at Châteaurenard and Dijon, France, respectively) and from rhizosphere, rhizoplane and root tissue of two plant species (flax and tomato) cultivated on these two soils. According to their ability to dissimilate nitrogen, the isolates have been distributed into three metabolic types: non-dissimilators, NO2 - accumulators and denitrifiers. While the three metabolic types were recovered in all the compartments of soil D experiments, only two (non-dissimilators and denitrifiers) were recovered in all the compartments of soil C experiments. Even under the contrasting conditions of the two soil types, both plants were able to select the nitrate dissimilating community among the total community of fluorescent Pseudomonas, but the mode of this selection seems to be dependent on both plant and soil type. The soil type appears to be unable to significantly modulate the strong selective effect of tomato. Indeed, similar dissimilator to non-dissimilator ratios were found in the root tissue of this plant species cultivated in both soils. In contrast, the different dissimilator to non-dissimilator ratios observed in flax roots between soils C and D suggest that the selective effect of flax was modulated by the soil type. Taxonomic identifications showed that the 618 isolates were distributed among three species (P. chlororaphis, P. fluorescens, P. putida) plus an intermediate type between P. fluorescens and P. putida. However, no clear relationship between the distribution of the metabolic types (functional diversity) and the distribution of bacterial species has been found.
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  • 62
    ISSN: 1573-5036
    Keywords: ammonium ; H+ flux ; H+-selective microelectrode ; mineral uptake ; pH-indicator dye ; nitrate ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Two methods for measuring proton fluxes along intact maize roots grown with NH 4 + or NO 3 − at pH 6.5 were compared. Videodensitometric measurement of changes in a pH-indicator dye by video camera was used to map pH around roots and determine the amounts of protons released by various root regions. This method was compared with potentiometric determination of the concentration of H+ in the unstirred layer at the root surface using ion-selective microelectrodes. With NH 4 + the roots released large amounts of H+ in preferential regions where the rate of flux can reach 1.4 or even 2.5 nmol m−1 s−1. Videodensitometry indicated a first region of root acidification in the subapical zone, but this was more difficult to localize with microelectrodes. With NO3 − both methods showed that the roots released small amounts of H+ and that the apical region took up H+ in the first 10 mm then sometimes released H+ over the following 10 mm of root. The H+ flux profiles obtained by both methods were in good agreement in terms of both order of magnitude of the fluxes and spatial differences along the root. These results suggest that videodensitometry, which is easier to use than potentiometry, can be used to screen different plant species or cultivars under various experimental conditions. The microelectrode technique is indispensable, however, for studying the underlying mechanisms of net H+ fluxes.
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  • 63
    ISSN: 1573-5036
    Keywords: 14CO2 labelling ; flow detection of beta radiations ; rhizosphere respiration ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The present work describes an original method to follow rate of 14CO2 and total CO2 production from rhizosphere respiration after plant shoots had been pulse-labelled with 14CO2. We used a radioactivity detector equipped with a plastic cell for flow detection of beta radiation by solid scintillation counting. The radioactivity detector was coupled with an infrared gas analyser. The flow detection of 14CO2 was compared to trapping of 14CO2 in NaOH and counting by liquid scintillation. First, we demonstrated that NaOH (1 M) trapped 95% of the CO2 of a gaseous sample. Then, we determined that the counting efficiency of the radioactivity flow cell was 41% of the activity of gaseous samples as determined by trapping in NaOH (1 M) and by counting by static liquid scintillation. The sensitivity of the 14CO2- flow detection was 0.08 Bq mL−1 air and the precision was 2.9% of the activity measured compared to 0.9% for NaOH trapping method. We presented two applications which illustrate the relevance of 14CO2-flow detection to investigations using 14C to trace photoassimilates within the plant-soil system. First, we examined the kinetics of 14CO2 production when concentrated acid is added to NaH14CO3. This method is the most commonly used to label photoassimilates with 14C. Then, we monitored 14CO2 activity in rhizosphere respiration of 5-week old maize cultivated in soil and whose shoots had been pulse-labelled with 14CO2. We conclude that alkali traps should be used for a cumulative determination of 14CO2 because they are cheap and accurate. On the other hand, we demonstrated that the flow detection of 14CO2 had a finer temporal resolution and was consequently a relevant tool to study C dynamics in the rhizosphere at a short time scale.
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  • 64
    ISSN: 1573-5036
    Keywords: field root studies ; modelling ; root ; root growth ; root mapping ; root orientation ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Root length density (RLD) is an important determinant of crop water and nutrient acquisition, but is difficult to measure in the field. On a soil profile, in-situ counts of root impacts per unit surface on soil profiles (NI) can be used to calculate RLD if crop-specific parameters for preferential root orientation (anisotropy) are known. An improved method for field determinations of RLD was developed and validated for maize at sites in Côte d'Ivoire and Burkina Faso. Root anisotropy was measured with cubes of undisturbed soil with 0.1 m sidelength, based on NI observed on three planes oriented perpendicularly to each other. RLD was also measured for the enclosed volume. Repetition of such measurements enabled estimation of the robustness across sites of empirical and geometric models for the relationship between RLD and NI:RLD = NI CO, with CO being the coefficient of root orientation, theoretically equals 2 for an isotropic distribution. Root systems were found to be nearly isotropic, except near the root front (0.3 to 0.5 m), where roots had a preferentially orthotropic orientation. Measured RLD was generally about 50% larger than RLD calculated from observed NI and CO, indicating that at least one of the measurement techniques had a systematic error. The ratio between measured and calculated RLD (CE), which ranged from 0.8 to 2, increased with the age of the plants and decreased with soil depth. CE was therefore introduced as an additional coefficient, resulting in RLD = NI CO CE. The empirical value for CO CE was between 2 and 5. The empirical coefficients CO and CE were the same for the sites in Cote d'Ivoire (oxisol with an iron pan at 0.6 to 0.9 m) and Burkina Faso (alfisol with an iron pan at 0.4 to 0.8 m). The model was validated with independent data sets at both sites, and gave satisfactory predictions of RLD on the basis of NI obtained from single soil planes, which can be easily measured in the field.
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  • 65
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    Euphytica 108 (1999), S. 145-150 
    ISSN: 1573-5060
    Keywords: maize ; North Carolina model 2 ; salinity tolerance ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The genetic basis of salt tolerance was examined in selected salt tolerant and sensitive material from a sample of accessions previously assessed for variability in salinity tolerance. The North Carolina Model 2 Design and analysis was followed, tolerance being assessed in 10-day-old seedlings grown in salinized solution culture at control (0 mM), 60 mM and 80 mM NaCl concentrations). Salinity tolerance was shown to be under the control of genes with additive and non-additive effects, with broad and narrow sense heritability estimates being approximately 0.7 and 0.4 over all treatments.
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  • 66
    ISSN: 1573-5087
    Keywords: abscisic acid ; gene-expression ; H1 histone ; tomato ; water-deficit-stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Many genes are induced by periods of water deficit, and a subset of these are dependent on elevated ABA content for expression. A number of drought-induced genes are not induced in leaves of the ABA-deficient mutant flacca from tomato (Lycopersicon esculentum) but are induced in detached, wilted wild-type leaves and ABA-treated leaves of both genotypes. The nucleotide sequence of the cDNA and corresponding genomic DNA fragment of one of these genes, his1-s (formerly called le20), encodes an amino acid sequence that is rich in Lys, Ala, and Ser. The predicted protein contains the tripartite structure of H1 histone and is similar to other H1 histones, especially in the globular domain. Since, his1-s is more closely related to a stress-induced gene from Lycopersicon pennellii than to another H1 histone in the tomato genome it is considered a stress-induced variant of H1 histone. his1-s mRNA accumulated in vegetative plants in response to other abiotic stress treatments, including application of polyethylene glycol, and salt. The mRNA preferentially accumulated in leaves as compared to roots. his1-s mRNA accumulation was controlled during development; the level was higher in developing seeds of mature green fruit than in detached wilted leaves. H1 histones have been implicated in the general repression of gene expression and in the regulation of specific genes. The rapid accumulation of his1-s mRNA during stress may indicate that this unique, stress-induced H1 histone is involved in controlling gene expression during plant stress.
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  • 67
    ISSN: 1573-5087
    Keywords: auxin biosynthesis ; auxin inhibitors ; indole analogues ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Maize liquid endosperm extracts contain the enzymes necessary for all of the steps of the plant IAA biosynthetic pathway from tryptophan, and provide a means to assay the pathway in vitro. We have analyzed the reactions in the presence of a series of indole and indole-like analogues in order to evaluate the potential of these compounds to act as inhibitors of IAA biosynthesis. Such inhibitors will be useful to investigate the tryptophan to IAA pathway, to determine the precursors and intermediates involved, and to select for mutants in this process. A number of such compounds were tested using in vitro enzyme assays for both the tryptophan dependent IAA biosynthesis pathway and for tryptophan synthase β activity. Some compounds showed strong inhibition of IAA biosynthesis while having only a slight effect on the reaction rate of tryptophan synthase β. These results: (1) show that IAA biosynthesis can be selectively inhibited relative to tryptophan biosynthesis; (2) suggest potential ways to screen for IAA biosynthetic pathway mutations in plants; and (3) provide additional tools for studies of IAA biosynthesis in plants.
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  • 68
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    Nutrient cycling in agroecosystems 54 (1999), S. 73-80 
    ISSN: 1573-0867
    Keywords: anhydrous ammonia ; dicyandiamide ; nitrification inhibitor ; urea-ammonium nitrate ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract One approach to reduce NO3 movement to groundwater is increasing the proportion of N supplied to the crop as NH4–N. Nitrification inhibitors (NI's) can be used to enhance NH4–N supply, but most studies have focused on yield response, with little attention given to environmental impacts. To determine the effect of enhanced NH4 sources on corn grain yield, N uptake and NO3 movement to groundwater, three sidedress materials were compared during three different growing seasons. Application of anhydrous ammonia (AA) and addition of the NI, dicyandiamide (DCD) to urea-ammonium nitrate (UAN) both reduced NO3 leaching losses relative to that incurred with UAN. With AA and UAN + DCD (as compared with UAN) subsoil solution NO3 concentrations were reduced by an average of: 1.1 mg NO3–N kg-1 soil following (fall 1993) a dry growing season; 2.4 mg NO3–N kg-1 soil during (spring and summer 1994) and 1.4 mg NO3–N kg-1 soil after (fall 1994) a wet growing season; and 0.5 mg NO3–N kg-1 soil following (fall 1995) a growing season with intermediate rainfall. Based on average solution NO3 concentrations and approximate drainage after harvest, estimated N losses between harvest and freeze-up were 43, 22 and 19 kg N ha-1 with UAN, UAN + DCD and AA, respectively (average of 3 years). Grain yields and aboveground N uptake were greater with AA and UAN + DCD than with UAN, and residual fertilizer N (applied N less aboveground N uptake) was 18, 6 and -2 kg N ha-1 with UAN, UAN + DCD and AA, respectively (average of 3 years). As is often observed, the trend for greater yield with addition of the NI was not large or consistent enough to meet registration criteria. Data demonstrating reduced NO3 leaching are also relevant, and positive environmental impacts should be a criterion for registration. For growers who are reluctant to use AA, this would provide an alternative source to maximize yield while minimizing NO3 movement to groundwater.
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  • 69
    ISSN: 1573-0654
    Keywords: cotton ; drainage ; irrigation ; salinity ; shallow groundwater ; tomato
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In situ use of ground water by plants is one optionbeing considered to reduce discharge of subsurfacedrainage water from irrigated agriculture. Laboratory, lysimeter, and field studies havedemonstrated that crops can use significant quantitiesof water from shallow ground water. However, moststudies lack the data needed to include the crop wateruse into an integrated irrigation and drainage watermanagement system. This paper describes previousstudies which demonstrated the potential use of groundwater to support plant growth and the associatedlimitations. Included are results from three fieldstudies which demonstrated some of the managementtechniques needed to develop an integrated system. The field studies demonstrated that approximately 40to 45% of the water requirement for cotton can bederived from shallow saline ground water. Thatregulation of the outflow will result in increasinguse. Implementation of integrated management ofirrigation and subsurface drainage systems is a viableand sustainable alternative in the management ofsubsurface drainage water from arid and semi-aridareas only if soil salinity can be managed and if thesystem is profitable.
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  • 70
    ISSN: 1573-5060
    Keywords: functional male sterility ; hybrid seed production ; tomato
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Data and findings concerning the development of an effective male sterility system (as already applied in the practice of producing tomato hybrid seed) through the use of the positional sterility (ps 2) gene are reported. Undesirable selfing and the necessity of emasculation are discussed as the two main disadvantages that limit the use of ps 2-sterile seed parents in tomato hybrid seed production. The following specific characteristics in the performance of ps 2-lines were evaluated: 1) the percentage of selfing in the ps 2-lines varies within and between the years of growing, being forever lowest during the period of hybrid seed production; 2) the percentage of selfed seeds when using a ps 2-line as seed parent in producing hybrid seed is significantly lower than the percentage of selfing, observed on this same line; 3) the ps 2-gene expressivity varies depending on the genotype. This enables the breeding of ps 2-lines exhibiting very low percentage of selfing; 4) stamen emasculation at anthesis (as applied in ps 2-lines) is significantly easier and more rapid than emasculation in floral buds. The easy maintenance of the sterile lines – by artificial selfing it is possible to produce 100% ps 2 progeny – and the high yield of hybrid seed obtained are discussed as important advantages in using this type of sterility in tomato hybrid seed production.
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  • 71
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    Plant and soil 212 (1999), S. 163-171 
    ISSN: 1573-5036
    Keywords: amino acids ; carboxylic acids ; nicotianamine ; Tc ; tomato ; xylem
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract This paper deals with a new analytical approach for studying metal speciation in the xylem, as applied to the nuclear waste metal technetium (99Tc) in tomato plants (Lycopersicon esculentum Mill, cv. Tiny Tim). Special attention was paid to sampling protocols and sample handling so that metal oxidation/reduction processes during analytical procedures did not influence the results. Marker Tc-ligand complexes were synthesized in vitro (Tc-cysteine, Tc-histidine, Tc-citrate, and Tc-nicotianamine) and sampling was performed under both argon and atmospheric conditions. Analyses were carried out using paper chromatography, gel electrophoresis (PAGE), and reversed phase ion-pair chromatography (RP-IPC). The results show Tc to be present predominantly in the TcO4 − form in the xylem, indicating transport similarities with molybdenum and chromium. Probably, the approach used is also valuable in other metal-speciation studies in the xylem.
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  • 72
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    Plant and soil 212 (1999), S. 201-206 
    ISSN: 1573-5036
    Keywords: complexation ; CrIII ; organic acids ; root exudates ; solubilization ; tomato
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Pot experiments were conducted to investigate the effect of various organic acids (carboxylic and amino acids) on the uptake and translocation of root-absorbed trivalent chromium by tomato ( Lycopersicum esculentum) plants grown in sand and soil culture. Statistically significant increases in chromium accumulation from Cr(III) treated plants in the presence of increasing concentrations of organic acid suggest the existence of Cr(III) — organic acid interactions in the soil-plant system. However, the amino acids have been less effective in the mobilization of chromium compared to carboxylic acids. The results are discussed on the basis of the potential of organic acids to form complexes with Cr(III).
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  • 73
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    Nutrient cycling in agroecosystems 52 (1998), S. 61-65 
    ISSN: 1573-0867
    Keywords: acidulated phosphates ; available P ; cationic impurities ; corn ; phosphorus sources ; water soluble P ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In Brazil, where the rock phosphates are high in impurities, no attempthas been made to evaluate the P supplying efficiency of the neutral ammoniumcitrate fraction (NAC) of P fertilizers, or to verify if the NAC +H2O extraction solution (AOAC) is satisfactory for estimatingthe P availability. To attain these objectives, a greenhouse experiment wascarried out with samples of a Typic Hapludox soil. Four acidulatedphosphates obtained from Brazilian raw materials were studied; monocalciumphosphate p.a.[Ca(H2PO4)2·H2O]was included as a standard source of P, as well as leached samplescontaining no water-soluble P. The fertilizers were thoroughly mixed withthe whole soil in the pots or with only 1% of its volume, at the rateof 50 mg kg-1 of P, soluble in NAC + H2O. Cornplants (Zea mays, L.) were grown for 35 days and the amounts of dry matterand P accumulated in plant tops were determined. Increasing the amount ofcationic impurities in the raw materials decreased the concentration ofwater-soluble P, NAC + H2O-soluble P and water-soluble P/NAC+H2O soluble P ratio of the fertilizers obtained. The P in theNAC fraction was not as much available to plants as in the NAC +H2O fraction or in pure MCP. The great variation found in drymatter (5.4 to 17.1 g pot-1) and in P uptake (6.3 to 22.2 mgpot-1) indicates that the AOAC method is not an adequate indexfor evaluating the P availability of fertilizers with high amounts ofcationic impurities.
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  • 74
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    Potato research 41 (1998), S. 117-125 
    ISSN: 1871-4528
    Keywords: α-solanine ; α-chaconine ; C:S ratio ; glycoalkaloid content ; tuber size ; individual tubers ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Plants of early potato cultivars were sampled at successive harvests during tuber development and individual tubers were analysed for α-solanine and α-chaconine using high-performance liquid chromatography. Mean tuber total glycoalkaloid concentration (α-solanine plus α-chaconine) per plant decreased with time and statistically significant differences between cultivars were observed in the patterns of decline during tuber growth. The mean tuber ratio of α-chaconine to α-solanine increased during tuber development and was also affected by genotype. Total glycoalkaloid concentration for individual tubers of marketable sizes (up to 50 g fresh weight) exceeded the safety limit of 20 mg per 100 g fresh weight for cultivars Home Guard and British Queen but not for Rocket. These differences were attributable to differences in both rates and patterns of glycoalkaloid accumulation during tuber development, although in all cultivars results were consistent with glycoalkaloid accumulation occurring in the expanding peripheral cell layers of tubers for a considerable period after tuber initiation.
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  • 75
    ISSN: 1871-4528
    Keywords: ratio ; root-shoot ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Potato, wheat and sugar beet were grown in a growth chamber in tanks with flowing solutions containing K-concentrations of 1.5, 5, 15, 50 and 200 μM to find reasons for different K contents of solution needed to reach 90% maximum dry matter accumulation (external K requirement). All species showed variation in dry matter accumulation with varying K levels. To reach 90% maximum dry matter accumulation potato needed 40 μM K, whereas wheat and sugar beet needed 6.4 and 4.4 μM K respectively. These differences in external K requirement could not be explained by differences in their internal K requirement since the internal requirement of potato (7.7% K) was about one and a half times of that of sugar beet (5.4%) but its external requirement was nine times of that of sugar beet. At low K supply potato plants showed a lower influx and a reduced root growth as compared with wheat and sugar beet.
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  • 76
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    Potato research 41 (1998), S. 311-317 
    ISSN: 1871-4528
    Keywords: Solanum tuberosum L. ; general combining ability ; specific combining ability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary In an epiphytotic year of early blight, data were recorded on its incidence in 72 progenies (18 females x 4 males) and their parents planted in a randomised complete block design at the Punjab Agricultural University, Ludhiana, India. Combining ability analysis showed that both additive and non-additive gene action were important, with a preponderance of the latter in the inheritance of resistance to early blight. In general, progenies were as good as or better than mid-parent values. Crosses involving both or at least one parent with good general combining ability resulted in heterotic early blight resistant progenies. Promising parents and crosses were identified.
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  • 77
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    Potato research 41 (1998), S. 1-8 
    ISSN: 1871-4528
    Keywords: immobilisation ; filter paper ; dot RT-PCR ; print RT-PCR ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A test procedure for PSTVd is described based on immobilisation of plant sap on filter paper, by dotting or tissue printing followed by RT-PCR. Tests were carried out using primarily and secondarily infected potato plants, primarily infected in vitro plants, and potato tubers. Print PCR was shown to be suitable for testing large samples of potato plants whereas dot PCR is recommended for in vitro plantlets and tuber tissue. Bulking one infected plant to 4 or 9 healthy plants gave reliable results with secondarily infected potato plants, but sometimes the test failed to detect PSTVd in primarily infected in vitro plants. Dotted and printed paper squares could be stored at 4°C for at least 2 weeks in Triton X-100 solution or under dry conditions. Storing at room temperature can lead to unreliable results.
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  • 78
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    Potato research 41 (1998), S. 219-228 
    ISSN: 1871-4528
    Keywords: homozygous genotypes ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Using potato parental lines homozygous at a locus or loci controlling resistance to potato leafroll virus (PLRV) can give advantages in the selection of resistant forms. In order to identify homozygous diploid clones their test-cross families were evaluated. All the clones that were test-crossed expressed resistance in primarily- and secondarily-infected plants and etiolated sprouts, and were derived from mating genotypes highly resistant to PLRV. Genotypes from test-cross families varied in resistance to PLRV, and one family was found which had only resistant genotypes, suggesting that the resistant parent of this progeny was homozygous at resistance loci. Evidence was gathered that resistance in some diploid clones may result from resistance to virus multiplication as well as restricted virus transport from leaves to tubers.
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  • 79
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    Potato research 41 (1998), S. 277-287 
    ISSN: 1871-4528
    Keywords: Solanum tuberosum L. ; quality ; bruising ; external ; internal ; model ; index
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Methods for quantifying external damage and bruising can be inaccurate and result in an index that is difficult to interpret. A new index was derived by taking measurements of peeled slices from cv. Record and developing a mathematical model to predict the percentage volume removed per peeler stroke for a range of potato cultivars. It was found that an average of 1.25% of the tuber volume was removed per peeler stroke. By counting the number of peeler strokes to remove damaged tissue and multiplying by 1.25, an estimate of the percentage tuber volume lost due to bruising or external damage can be obtained. The index can accommodate most types of damage and result in an index that is readily understood.
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  • 80
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    Potato research 41 (1998), S. 345-354 
    ISSN: 1871-4528
    Keywords: tuber blight ; Solanum tuberosum L. ; disease assessment ; fungal pathogenicity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Variation in aggressiveness to tubers among isolates ofPhytophthora infestans sampled from three potato growing regions in the Netherlands was compared. Variation in the ability to infect tubers of cv. Bintje was found between isolates of each of the three regional populations. The most aggressive isolate of the old population matched the average level of the new population in its ability to infect tubers. As a consequence, the commonly used reference isolate VK 6C can no longer be considered to be representative of the present population ofP. infestans. Therefore it is recommended that testing tuber resistance for the official list of potato cultivars with this isolate should be discontinued. Tuber infection and subsequent spread of the fungus in the tuber tissues were not found to be correlated. The components of tuber pathogenicity studied were not correlated to pathogenicity factors in the foliage, as measured under growth chamber conditions.
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  • 81
    ISSN: 1871-4528
    Keywords: alcohol dehydrogenase ; phosphoglucose isomerase ; sugar assay ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Artefactual results were obtained during assay of sugars in ethanolic extracts of potato tubers with the microplate method. The problem was attributed to contamination with alcohol dehydrogenase of the commercial (yeast) phosphoglucose isomerase used in the assay. The use of phosphoglucose isomerase from another source (rabbit muscle) eliminated the problem.
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  • 82
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    Potato research 41 (1998), S. 21-28 
    ISSN: 1871-4528
    Keywords: Solanum tuberosum L. ; general combining ability ; seedling generation ; clonal generations ; genotypexenvironment ; yield ; tuber colour and shape
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary General combining ability and its repeatability in the early generations of a potato breeding programme was studied by evaluating 72 progenies (18×4) of 22 parents in a factorial mating design for three successive generations. The mean squares for combining ability due to females, males and females × males were significant for eight out of the ten characters studied. Variance estimates due to specific combining ability were more important than those due to general combining ability for most of the characters in all the generations. General combining ability effects varied from generation to generation. Most of the correlation coefficients between generations for general combining ability effects were significant, but of moderate magnitude (0.5–0.8). Parents with consistent performance over generations and those specifically suitable for a TPS crop were identified.
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  • 83
    ISSN: 1871-4528
    Keywords: Solanum tuberosum L. ; Phytophthora infestans ; inducer agents ; plant protection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Tests for systemic induced resistance (SIR) to late blight were performed with different potato cultivars in field trials and in growth chamber experiments. The non-pathogenPhytophthora cryptogea (Pc) and salicylic acid (Sa) were used as inducer agents. In the field, plants were naturally infected byPhytophthora infestans while the indoor plants were inoculated. The degree of SIR obtained varied with the cultivar used and also with the type of inducer. For example in the field the susceptible cv. St. Cecilia had enhanced resistance with Pc whereas Sa caused increased susceptibility. Inbred resistant cvs acquired increased resistance after treatment with Sa. In a separate pilot experiment in a growth chamber, Sa at two different concentrations was injected into potato seed tubers before planting. The higher Sa concentration increased resistance in genetically resistant cultivars while the lower Sa concentration brought about increased susceptibility.
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  • 84
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    Potato research 41 (1998), S. 203-209 
    ISSN: 1871-4528
    Keywords: Solanum tuberosum L. ; tuber ; blanching ; pre-drying
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Factors affecting the volume expansion of potato cubes during puffing in a fluidised bed were examined. It was found that puffing temperature, initial size, pre-drying time and puffing time influenced the degree of expansion of the cube during the puffing step. Blanching alone was found not to influence expansion, but in conjunction with the other factors it was found that blanched samples showed greater volume expansion than unblanched samples. The optimum conditions for maximum volume expansion were found to be; blanching for 80 s, cube size between 7.5–12.5 mm, pre-drying time of 90 min. at 90°C and a puffing time of 270s at 130°C.
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  • 85
    ISSN: 1871-4528
    Keywords: Solanum tuberosum L. ; drought tolerance ; irrigation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Potato crops in subtropical climates are often subjected to water stress, resulting in low yields and poor tuber quality. The yield response of potato genotypes to water supply was investigated in six trials, three each in spring and autumn plantings. Trials were conducted under automated rain shelters, using an irrigation boom to impose five soil water regimes. The negative effect of water stress on tuber yield was more detrimental in spring than in autumn, because of higher atmospheric evaporative demand and higher temperatures in spring. An average yield reduction of 68% was recorded for the most severely stressed regime in spring plantings, while the mean reduction for the same treatment in autumn was only 42%. Genotypic differences in yield response to drought were clearly illustrated in spring, but not in autumn. This suggests that the choice of genotypes is only influenced by the availability of water in spring, when more drought tolerant genotypes should be used.
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  • 86
    ISSN: 1871-4528
    Keywords: post harvest disease ; potato ; Solanum tuberosum L. ; resistance ; toxin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Virulence of 12Fusarium oxysporum isolates was determined on three potato cultivars Late Harvest, BP1 and Kimberley Choice. The production of fusaric acid by the 12F. oxysporum isolates was also determined. The aim of the study was to determine whether a correlation exists between fusaric acid production and virulence ofF. oxysporum isolates. Late Harvest was the most tolerant and BP1 the most susceptible cultivar. Virulence ranking, order of theF. oxysporum isolates with the different cultivars corresponded with the mean of value of the ranking order for all three cultivars. A correlation was found between virulence of isolates and fusaric acid production except for Late Harvest. Fusaric acid production may play a major role in the development of dry rot in potato tubers.
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  • 87
    ISSN: 1871-4528
    Keywords: potato blight ; hydrolytic enzymes ; chitinases ; glucanases ; phytoalexins ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The kinetics of accumulation of chitinases, glucanases and phytoalexins were studied in two potato cultivars, differing in their degrees of vertical and horizontal resistance, when infected with two races ofPhytophthora infestans. Tuber disks of cvs Kennebec (susceptible, low horizontal resistance) and Huinkul (tolerant, high horizontal resistance) were infected with either race “0” (avirulent) or “C” (complex, race 1.3.5.7.11) ofPhytophthora infestans. Extracts of tuber tissue (0–7 days) from cv. Kennebec infected with race “0” showed a strong increase in phytoalexin production and in chitinase and glucanase activities when compared with those infected with race “C”. These results indicate that race “C” is able to block defensive reactions. No significant differences were observed in cv. Huinkul infected with both races. The contribution of these reactions to horizontal resistance is unknown, and our results would not support a conclusive role for them in the interaction.
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  • 88
    ISSN: 1871-4528
    Keywords: prochloraz ; Solanum tuberosum L. ; soil treatment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Soil in a potato field naturally infested with black dot (Colletotrichum coccodes) was fumigated with methyl bromide at 126 g m−2 or left unfumigated. Potato seed tubers (cv. BP1) uninfected, lightly infected (1–25% surface affected), severely infected (26–100% surface affected) and severely infected withC. coccodes but dusted with prochloraz manganese chloride as Octave 2.5% DP at 750 g per 100 kg seed were planted in fumigated and unfumigated soil. When harvested, the incidence of black dot on the progeny of infected seed planted in unfumigated soil was twice that of progeny in fumigated soil, with progeny of uninfected seed having a 68.5 times higher disease incidence in unfumigated soil. Black dot on progeny tubers was reduced by pre-treatment of seed with prochloraz in fumigated soil only. With black dot infested fields, planting disease-free seed or treating seed with fungicides would not decrease disease on progeny tubers.
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  • 89
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    Potato research 41 (1998), S. 211-217 
    ISSN: 1871-4528
    Keywords: in vitro tuberization ; micropropagation ; mineral nutrition ; seed potato production ; Solanum tuberosum L. ; tissue culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The effect of inorganic nitrogen nutrition on the induction and development of microtubers by cytokinin-induced tuberization was studied in four potato genotypes belonging to different maturity groups. The objective of this study was to investigate whether a reduction in total nitrogen level in the Murashige & Skoog medium would improve cytokinin-induced tuberization rate. The effect of three levels of total nitrogen (15, 30 and 45 meq) on tuberization was studied at constant (20 meq K) and varying potassium levels approximating to 5, 10 and 15 meq. Reducing the total nitrogen supply increased the number but decreased the size of nitrogen level on the rate of assimilate partitioning (harvest index) during cytokinin-induced microtuberization.
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  • 90
    ISSN: 1871-4528
    Keywords: Solanum tuberosum L. ; host differentials ; R genes ; multilocus genotype ; host-pathogen interactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A collection of 80 isolates ofPhytophthora infestans, representing multilocus genotypes of the pathogen found in Canada from 1994 to 1996, was screened on a series of nine differential potato host cultivars to determine the physiological race of the isolates. A total of 28 pathotypes were found among the 11 genotypes present in the collection. There was a significant increase in the complexity of pathotypes from 1994 to 1996 which reflected the displacement of the US-1 genotype (mean of 2.2 host differentials infected) by the US-8 genotype (mean of 8.1 host differentials infected). Eighteen of the US-8 isolates could overcome all nine of the resistance genes tested. Virulence genes which overcame host resistance conferred by R8 were the rarest in the populations studied. The predominance of complex populations ofP. infestans in Canada implies that the introduction of cultivars with specific R genes for resistance would be an ineffective control measure.
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  • 91
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    Potato research 41 (1998), S. 305-310 
    ISSN: 1871-4528
    Keywords: potato late blight ; mating types ; oospores ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary In this paper we present observations made during three years in a potato field in Sweden that indicated the presence of soil borne inoculum ofPhytophthora infestans. In 1994, a fungicide trial against late blight was left in the field with various degrees of late blight infection. In 1995, cereals was grown in the field. In 1996, certified potato seed tubers were planted and blight appeared early in the season in a pattern corresponding to the heavily infected areas in 1994. No volunteer potato plants were found in 1995 or 1996. Both mating types A1 and A2 were isolated in 1996 and 1997 and oospores were found in leaves, stems as well as in stolons.
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  • 92
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    Potato research 41 (1998), S. 327-334 
    ISSN: 1871-4528
    Keywords: near infrared spectrometry ; modified partial least squares regression ; quality characterisation ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The development of a method of NIR (near infrared) spectrometric analysis to measure the quality determining constituents of potatoes and the accuracy of its performance are presented. The results show that it is possible to obtain quantitative information about different constituents from reflectance measurement of homogenized peeled potatoes. The analytical performance of NIR spectrometry is highly dependent on the cultivar being measured. Consequently, the calibration and validation sample sets will have to be expanded to provide greater utility.
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  • 93
    ISSN: 1572-9788
    Keywords: composite interval mapping ; maize streak virus ; QTL ; RFLP ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Resistance to maize streak virus (MSV) is an essential trait of improved maize varieties in sub-Saharan Africa. We mapped quantitative trait loci (QTL) for resistance to MSV in a population of 196 F2:3 lines derived from a cross between the maize inbred lines CML202 (resistant) from CIMMYT-Zimbabwe and Lo951 (susceptible) from Italy. Field tests were planted at two locations in Zimbabwe, inoculated with viruliferous leaf hoppers (Cicadulina mbila), and scored twice (21 and 83 days after infesting, DAI) on a 1–5 scale. The mean final streak intensity (score 2) of the parent lines was 2.2 (CML202) and 4.8 (Lo951). Genotype × location interaction was large for score 1 but negligible for score 2. Consequently, the heritability was higher for score 2 (0.93) than for score 1 (0.62). By composite interval mapping across locations, using a linkage map with 110 RFLP loci, four significant (LOD ≥3.0) QTL were identified for score 1 on chromosomes (C) 1, 2, 3, and 4, respectively. All four were contributed by CML202. For score 2, only the QTL on C 1 was significant (LOD =37), explaining 59% of the phenotypic and 64% of the genotypic variance. The QTL's partially dominant gene action was consistent with the nearly intermediate resistance of the F1 generation (relative heterosis for resistance 12%). The presence of one major QTL is consistent with the bimodal frequency distribution of the mapping population showing a clear 3:1 segregation. This gene seems to be allelic or identical to Msv1, a major resistance gene which was previously identified in the same genomic region in Tzi4, an inbred line from IITA. Inbred CML202 had lower final disease ratings than Tzi4. The greater resistance of CML202 may be due to allelic differences at the msv1 locus or due to the minor QTL on C 2, 3, and 4 which were not detected in Tzi4. z y Trigo (International Maize and Wheat Improvement Center); IITA, International Institute of Tropical Agriculture; IRAT, Institute de Recherches Agronomiques Tropicales et des Cultures Vivrières; KARI, Kenya Agricultural Research Institute; MSV, maize streak virus; QTL, quantitative trait locus/loci
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  • 94
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    European journal of plant pathology 104 (1998), S. 29-36 
    ISSN: 1573-8469
    Keywords: biological control ; Zea mays ; Pythium spp. ; Fusarium spp. ; seed bacterization Burkholderia cepacia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Burkholderia cepacia (syn. Pseudomonas cepacia) strain PHQM100 applied as a seed coating was tested in growth chamber experiments for its ability to suppress preemergence damping-off, and postemergence damping-off in corn induced by Pythium and Fusarium spp. The symptoms observed in bioassays with soils naturally infested with the fungal pathogens were seed rot with Pythium spp. and mesocotyl and root tissue necrosis in the presence of Fusarium spp. Three corn cultivars that differed in their susceptibility to damping-off pathogens were used. Cultivar L was susceptible to pre- and postemergence damping-off, whereas cv. LPDP and cv. LG11 were moderately resistant and resistant to the damping-off diseases respectively. In the presence of Pythium spp., seed treatment with B. cepacia reduced seed rot, as compared to the untreated seeds, and this reduction was more consistent in the cv. LPDP than in the resistant cv. LG11 or the susceptible cv. L. In soils infested with Fusarium spp., seed treatment significantly reduced root and mesocotyl necrosis as compared to the untreated seeds, and this reduction was more consistent in the resistant cultivars LG11 and LPDP than in the susceptible cv. L. Root colonization levels by B. cepacia were similar in the three corn cultivars tested. Biocontrol efficiency of B. cepacia varied among cultivars mainly due to the differences in their susceptibility to the fungal pathogens. In spite of variability and also irrespective of the soil characteristics, B. cepacia increased seedling emergence and decreased mesocotyl and root necrosis when used as a seed coating.
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  • 95
    ISSN: 1573-5087
    Keywords: antioxidant system ; brassinolide ; drought stress ; methyl jasmonate ; uniconazole ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effects of brassinolide, uniconazole and methyl jasmonate on the antioxidant system were studied in seedlings of drought-resistant (PAN 6043) and drought-sensitive (SC 701) cultivars of Zea mays L. When seedlings treated with the three regulators were subjected to water stress (−1.0 MPa PEG 6000 solution), the activities of superoxide dismutase, catalase and ascorbate peroxidase, as well as the ascorbic acid and total carotenoid contents, increased in the resistant cultivar, whereas the levels remained unaltered in the sensitive cultivar. The increased tolerance to drought stress induced by the growth regulators in the resistant cultivar seems to be due to the maintenance of increased antioxidant enzyme activity and antioxidant substance levels.
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  • 96
    ISSN: 1573-5087
    Keywords: androgenesis ; anther ; cold pretreatment ; endogenous IAA ; peroxidase ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A cold pretreatment is usually applied to induce maize androgenesis. Peroxidase activity, including indole-3-acetic acid (IAA) oxidase activity, and endogenous IAA concentrations were followed during a cold pretreatment (14 days, 7°C) in anthers of two maize genotypes, Seneca 60 and DH5×DH7, respectively with a low or high androgenetic response. The most prominent result was the absence of a detectable IAA oxidase activity in DH5×DH7. Adding effectors of IAA-oxidase activity or IAA transport did not affect significantly the crude peroxidase activity of DH5×DH7 anthers while inducing a clear inhibition of androgenesis at higher concentrations. No strict correlation was found between IAA level and physiological response, the low responding variety having as much IAA as DH5×DH7. However, for DH5×DH7, every treatment that lowered the IAA level after 14 days of cold resulted in a decrease in androgenetic response.
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  • 97
    ISSN: 1573-8469
    Keywords: Bemisia tabaci ; geminivirus ; primers ; tomato
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract DNA of tomato yellow leaf curl virus (TYLCV), a geminivirus transmitted by the whitefly Bemisia tabaci, was amplified from squashes of infected tomato plants and of viruliferous vectors using the polymerase chain reaction (PCR). Samples of infected tissues as small as 1 mm2 were squashed onto a nylon membrane. A 1 × 2 mm strip containing the squash was introduced into a 25 µl PCR reaction mix. The reaction products were subjected to gel electrophoresis, blotted and hybridized with a radiolabeled virus-specific DNA probe. TYLCV DNA was amplified from squashes of leaves, roots, and stem of infected tomato and from individual viruliferous whiteflies. The same squash could be used several times to amplify different virus DNA fragments with various sets of primers. Thus plant and insect squashes can be used as templates for the amplification of geminiviral DNA with no need to prepare tissue extracts or purify nucleic acids. The squash-PCR procedure was applied to study whitefly transmission of TYLCV. Tomato plants were inoculated by placing a single viruliferous insect in the center of a young leaflet. In some plants TYLCV DNA was detected at the site of inoculation as early as 5 min after the beginning of the access feeding and in all plants after 30 min. The squash-PCR procedure also was applied to the study of TYLCV acquisition by the insect vector. TYLCV DNA was detected in the head of whiteflies as early as 5 min after the beginning of the access feeding on infected tomato plants. Viral DNA was detected in the thorax after 10 min and in the abdomen after 25 min.
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  • 98
    ISSN: 1573-8469
    Keywords: Fusarium ; Pythium ; Pseudomonas ; tomato ; cucumber ; 2,4-diacetylphloroglucinol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Fluorescent pseudomonads producing the antimicrobial compound 2,4-diacetylphloroglucinol (Phl) are being studied extensively for use as biocontrol agents of soil-borne fungal diseases. Some of them can produce pyoluteorin (Plt) in addition to Phl, whereas others synthesise only Phl. Here, a collection of seven Phl+ Plt- pseudomonads, seven Phl+ Plt+ pseudomonads and seven Phl- biocontrol pseudomonads were compared for protection of plant roots against fungal pathogens. The seven Phl+ Plt+ pseudomonads were identical by restriction analysis of amplified spacer ribosomal DNA (spacer ARDRA), whereas the Phl+ Plt- pseudomonads and especially the Phl- biocontrol pseudomonads were quite diverse by spacer ARDRA. Collectively, the Phl+ Plt- pseudomonads proved superior to the Phl+ Plt+ pseudomonads and the Phl- biocontrol pseudomonads for protection of tomato against Fusarium crown and root rot (in rockwool microcosms) or cucumber against Pythium damping-off (in non-sterile soil microcosms). There was no correlation between protection in vivo and inhibition of the corresponding fungal pathogen on plates. However, there was a significant correlation between the amount of Phl produced on plates and protection of tomato against Fusarium crown and root rot, but not with protection of cucumber against Pythium damping-off. Interestingly, the minority of strains unable to produce HCN, an extracellular protease, or both, were among those unable to protect plants in both pathosystems. A seedling assay was developed to compare pseudomonads for suppression of Fusarium crown and root rot in vitro, and a significant correlation was found between disease severity in vitro and in vivo. Overall, results suggest that promising biocontrol pseudomonads may be identified based on the ability to produce Phl and/or specific ARDRA-based fingerprints.
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  • 99
    ISSN: 1573-5036
    Keywords: Lycopersicon esculentum ; nitrogen ; plant growth ; plant nutrition ; soil solarization ; tomato
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Soil solarization is a non-chemical disinfestation technique that frequently promotes plant growth in the absence of known major pathogens, a phenomenon termed increased growth response (IGR). The effect of solarization on plant nutrients and their role in the IGR was studied with tomato plants grown in solarized or non-solarized (control) sandy soil, under controlled conditions. Solarization considerably increased the soil concentrations of water extractable N, K, Ca, Mg and Na at most sites, whereas Cl and DTPA extractable Mn, Zn, Fe and Cu were decreased by the treatment. Plant growth and specific leaf area were enhanced in solarized as well as in N-supplemented control soil. In tomato plants grown in solarized soil, concentrations of most nutrients in the xylem sap, including N, were increased compared to the control, whereas Cl and SO4 levels decreased. The most significant increase in leaf nutrient concentration caused by soil solarization was recorded for N. Furthermore, leaf N concentration was highly and positively correlated with shoot growth. The concentration of Cu increased in leaves from the solarization vs. the control treatment, whereas that of SO4 and Cl decreased, the latter presumably below the critical toxicity level. The correlation between shoot growth and leaf concentration was positive for Cu and inverse for Cl and SO4. In conclusion, we found that soil solarization significantly affects nutrient composition in tomato plants, and provided strong evidence that N, and eventually also Cl, play a major role in IGR.
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  • 100
    ISSN: 1573-5060
    Keywords: Zea mays ; corn ; insect resistance ; antibiosis ; resistance breeding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The European corn borer (ECB) has become a serious pest for maize cultivation in Central and Western Europe. This study was conducted to evaluate resistance against ECB in a cross section of the European maize germplasm. A total of 115 flint and dent inbreds were evaluated for resistance under protected and artificial infestation conditions at two German sites in 1993. Resistance to ECB was assessed by damage rating before harvest, tunnel length in dissected stalks, and relative yield under infestation compared to protected control plots. Means for damage rating of stalks were significantly higher in flint lines than in dent lines. Artificial infestation reduced grain yield by 31% in flint lines and 20% in dent lines. Significant genotypic variances among lines and high genetic ratios (GR) were found in both flint and dent lines for all agronomic and ECB resistance traits. Exceptions were relative yield of stover in both germplasm groups and tunnel length in flint lines. Phenotypic correlations between agronomic and resistance traits were moderate to low. Damage rating was negatively correlated with days to silking and dry matter yield of stover in both germplasm groups. In vitro digestibility of stover was not associated with ECB resistance. Correlations of relative grain yield with tunnel length below the ear and damage rating were significantly negative, even though their magnitude was low. Our results indicate substantial genetic variation among European inbred lines for resistance to the univoltine ECB. Among all resistance traits measured, damage rating of stalks is best suited for assessment of ECB resistance in breeding programs because of its easy recording and high genetic ratio.
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