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  • 1
    Electronic Resource
    Electronic Resource
    Effects of mycorrhizal fungus isolates on mineral acquisition by Panicum virgatum in acidic soil (1999)
    Springer
    Mycorrhiza 9 (1999), S. 167-176 
    Details
    ISSN: 1432-1890
    Keywords: Key words Acaulospora ; Gigaspora ; Glomus ; Alleviation of toxic minerals ; Mineral nutrient concentrations ; Low pH soil ; Switchgrass
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Plant ability to withstand acidic soil mineral deficiencies and toxicities can be enhanced by root-arbuscular mycorrhizal fungus (AMF) symbioses. The AMF benefits to plants may be attributed to enhanced plant acquisition of mineral nutrients essential to plant growth and restricted acquisition of toxic elements. Switchgrass (Panicum virgatum L.) was grown in pHCa (soil:10 mM CaCl2, 1 : 1) 4 and 5 soil (Typic Hapludult) inoculated with Glomus clarum, G. diaphanum, G. etunicatum, G. intraradices, Gigaspora albida, Gi. margarita, Gi. rosea, and Acaulospora morrowiae to determine differences among AMF isolates for mineral acquisition. Shoots of mycorrhizal (AM) plants had 6.2-fold P concentration differences when grown in pHCa 4 soil and 2.9-fold in pHCa 5 soil. Acquisition trends for the other mineral nutrients essential for plant growth were similar for AM plants grown in pHCa 4 and 5 soil, and differences among AMF isolates were generally higher for plants grown in pHCa 4 than in pHCa 5 soil. Both declines and increases in shoot concentrations of N, S, K, Ca, Mg, Zn, Cu, and Mn relative to nonmycorrhizal (nonAM) plants were noted for many AM plants. Differences among AM plants for N and Mg concentrations were relatively small (〈2-fold) and were large (2- to 9-fold) for the other minerals. Shoot concentrations of mineral nutrients did not relate well to dry matter produced or to percentage root colonization. Except for Mn and one AMF isolate, shoot concentrations of Mn, Fe, B, and Al in AM plants were lower than in nonAM plants, and differences among AM plants for these minerals ranged from a low of 1.8-fold for Fe to as high as 6.9-fold for Mn. Some AMF isolates were effective in overcoming acidic soil mineral deficiency and toxicity problems that commonly occur with plants grown in acidic soil.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s005720050302
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  • 2
    Electronic Resource
    Electronic Resource
    Corn Root Growth in Soil Columns with Artificially Constructed Aggregates (1999)
    Springer
    Crop science 39 (1999), S. 725-730 
    Details
    ISSN: 1435-0653
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Zea mays L.) seedlings were grown for 33 d in soil columns, with Collamer silt loam soil (Fine-silty, mixed, mesic Glossaquic Hapludalf), that was artificially manipulated to create cubical aggregates of different sizes (25 and 50 mm, on each edge) and densities (1.4, 1.6, and 1.8 Mg m-3). Plant response was characterized by root and shoot growth. Root length, diameter, and weight were measured in zones within aggregates (intraaggregate pores, or micropores), and between aggregates and between horizontal slices of soil (collectively, interaggregate pores, or macropores). The preferred root growth pathway (within micropores or within macropores) differed with aggregate density and was influenced by aggregate size. Length of roots penetrating aggregates decreased exponentially with increasing aggregate density. Root growth (length) also shifted from within micropores to within macropores with increasing aggregate size, suggesting an interaction effect between density and size of aggregates. Accurate assessment of this interaction may allow the determination of the optimum conditions for root growth and, consequently, the maximum potential for crop growth in a specific soil.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/
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  • 3
    Electronic Resource
    Electronic Resource
    Predictive and postdictive success of statistical analyses of yield trials (1988)
    Springer
    Theoretical and applied genetics 76 (1988), S. 1-10 
    Details
    ISSN: 1432-2242
    Keywords: AMMI ; Genotype-environment interaction ; Prediction ; Soybean ; Yield trials
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The accuracy of a yield trial can be increased by improved experimental techniques, more replicates, or more efficient statistical analyses. The third option involves nominal fixed costs, and is therefore very attractive. The statistical analysis recommended here combines the Additive main effects and multiplicative interaction (AMMI) model with a predictive assessment of accuracy. AMMI begins with the usual analysis of variance (ANOVA) to compute genotype and environment additive effects. It then applies principal components analysis (PCA) to analyze non-additive interaction effects. Tests with a New York soybean yield trial show that the predictive accuracy of AMMI with only two replicates is equal to the predictive accuracy of means based on five replicates. The effectiveness of AMMI increases with the size of the yield trial and with the noisiness of the data. Statistical analysis of yield trials with the AMMI model has a number of promising implications for agronomy and plant breeding research programs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00288824
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  • 4
    Electronic Resource
    Electronic Resource
    Imputing missing yield trial data (1990)
    Springer
    Theoretical and applied genetics 79 (1990), S. 753-761 
    Details
    ISSN: 1432-2242
    Keywords: AMMI ; Missing data ; Prediction ; Soybean ; Yield trials
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The Additive Main effects and Multiplicative Interaction (AMMI) statistical model has been demonstrated effective for understanding genotype-environment interactions in yields, estimating yields more accurately, selecting superior genotypes more reliably, and allowing more flexible and efficient experimental designs. However, AMMI had required data for every genotype and environment combination or treatment; i.e., missing data were inadmissible. The present paper addresses the problem. The Expectation-Maximization (EM) algorithm is implemented for fitting AMMI depite missing data. This missing-data version of AMMI is here termed “EM-AMMI”. EM-AMMI is used to quantify the direct and indirect information in a yield trial, providing theoretical insight into the gain in accuracy observed and into the process of imputing missing data. For a given treatment, the direct yield data are the replicates of that treatment, and the indirect data are all the other yield data in the trial. EM-AMMI is used to inpute missing data for a New York soybean yield trial. Important applications arise from both unintentional and intentional missing data. Empirical measurements demonstrate good predictive success, and statistical theory attributes this success to the Stein effect.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00224240
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  • 5
    Electronic Resource
    Electronic Resource
    Photoperiod gene control over partitioning between reproductive and vegetative growth (1993)
    Springer
    Theoretical and applied genetics 86 (1993), S. 6-16 
    Details
    ISSN: 1432-2242
    Keywords: Sink ; Sink activity ; Source ; Harvest index ; Crop adaptation ; Yield physiology ; Maturity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The hypothesis tested was that lack of photoperiod gene activity allows inherent partitioning of photosynthate to continued growth of the earliest potential buds, flowers, pods, and seeds (the organs that give rise to the yield). Alternatively, and competitively, photoperiod gene activity causes the photosynthate to be partitioned predominantly toward continued growth of new vegetative organs plus later initiation of more reproductive (yield) organs. This hypothesis was tested by comparing an insensitive and a photoperiod-sensitive bean (Phaseolus vulgaris L.) cultivar and their F1 with F2 segregates of undetermined genotype. Randomly derived homozygous F8 segregates were also compared. The F8 generation included one photoperiod-insensitive and one photoperiod-sensitive genotype in a 1:1 ratio, which verified control by one photoperiod gene. Under long daylength (LD), in addition to early versus late flowering and maturity, the two genotypes expressed opposite levels of 23 other traits that would be changed by competitive partitioning of the photosynthate. In contrast, under short daylength (SD), both genotypes flowered and matured early, and both expressed the levels for all 25 traits that the photoperiod-insensitive genotype expressed in both SD and LD. The photoperiod gene interacted with daylength to control the levels of all three major physiological components of yield: the aerial biomass, harvest index, and days to maturity. Included among the other traits with levels altered by daylength-modulated photoperiod gene activity were: the number of branches, nodes, leaves and leaf area, the rate of yield accumulation, and sink activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00223803
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  • 6
    Electronic Resource
    Electronic Resource
    Accuracy and selection success in yield trial analyses (1989)
    Springer
    Theoretical and applied genetics 77 (1989), S. 473-481 
    Details
    ISSN: 1432-2242
    Keywords: AMMI ; Order statistics ; Selection ; Soybean ; Yield trials
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Yield trials serve research purposes of estimation and selection. Order statistics are used here to quantify the successes or problems to be expected in selection tasks commonly encountered in breeding and agronomy. Greater accuracy of yield estimates implies greater selection success. A New York soybean yield trial serves as a specific example. The Additive Main effects and Multiplicative Interaction (AMMI) statistical model is used to increase the accuracy of these soybean yield estimates, thereby increasing the probability of successfully selecting, on the basis of the empirical yield data, that genotype which has the maximum true mean. The statistical strategy for increasing accuracy is extremely cost effective relative to the alternative strategy of increasing the number of replications. Better selections increase the speed and effectiveness of breeding programs, and increase the reliability of variety recommendations. Selection tasks are frequently more difficult than may be suspected.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00274266
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  • 7
    Electronic Resource
    Electronic Resource
    Use of AMMI and linear regression models to analyze genotype-environment interaction in durum wheat (1992)
    Springer
    Theoretical and applied genetics 83 (1992), S. 597-601 
    Details
    ISSN: 1432-2242
    Keywords: Triticum turgidum L var ‘durum’ ; Durum wheat ; Genotype-environment interaction ; AMMI model ; Prediction assessment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The joint durum wheat (Triticum turgidum L var ‘durum’) breeding program of the International Maize and Wheat Improvement Center (CIMMYT) and the International Center for Agricultural Research in the Dry Areas (ICARDA) for the Mediterranean region employs extensive multilocation testing. Multilocation testing produces significant genotype-environment (GE) interaction that reduces the accuracy for estimating yield and selecting appropriate germ plasm. The sum of squares (SS) of GE interaction was partitioned by linear regression techniques into joint, genotypic, and environmental regressions, and by Additive Main effects and the Multiplicative Interactions (AMMI) model into five significant Interaction Principal Component Axes (IPCA). The AMMI model was more effective in partitioning the interaction SS than the linear regression technique. The SS contained in the AMMI model was 6 times higher than the SS for all three regressions. Postdictive assessment recommended the use of the first five IPCA axes, while predictive assessment AMMI1 (main effects plus IPCA1). After elimination of random variation, AMMI1 estimates for genotypic yields within sites were more precise than unadjusted means. This increased precision was equivalent to increasing the number of replications by a factor of 3.7.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00226903
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  • 8
    Electronic Resource
    Electronic Resource
    A whole-system reconsideration of paradigms about photoperiod and temperature control of crop yield (1993)
    Springer
    Theoretical and applied genetics 86 (1993), S. 17-26 
    Details
    ISSN: 1432-2242
    Keywords: Yield physiology ; Phenology ; Crop adaptation ; Harvest index ; Crop maturity ; Aerial biomass
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Effects by photoperiod gene(s) and daylength on crop yield and its three major physiological components (aerial biomass, harvest index, and days to harvest maturity) are reviewed for bean (Phaseolus vulgaris L.) and peanut (Arachis hypogaea L.). In these plus many other cited crops, photoperiod sensitive gene(s) delay days to flowering and/or days to maturity in non-promotive daylength while simultaneously lowering the harvest index. Thus, for many crops, earlier maturity is associated with higher harvest index, and/or it has been shown that photoperiod gene(s) control partitioning of photosynthate toward reproductive growth versus toward competitive partitioning to continued vegetative growth. Our conclusion is that photoperiod gene control over this partitioning precedes and is causal of the photoperiodgene control over days to flowering and maturity. This implies shifts from commonly accepted paradigms about effects by photoperiod and about breeding for higher yield. These paradigm shifts suggest more efficient ways to breed for cultivar adaption to the specific growing season duration and environment of each geographical site and for higher crop yield.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00223804
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  • 9
    Electronic Resource
    Electronic Resource
    Improving efficiency of breeding for higher crop yield (1993)
    Springer
    Theoretical and applied genetics 86 (1993), S. 27-40 
    Details
    ISSN: 1432-2242
    Keywords: Yield physiology ; Photoperiod/temperature ; Partitioning ; Harvest index ; Maturity ; Culivar adaptation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Exclusive selection for yield raises, the harvest index of self-pollinated crops with little or no gain in total bipmass. In addition to selection for yield, it is suggested that efficient breeding for higher yield requires simultaneous selection for yield's three major, genetically controlled physiological components. The following are needed: (1) a superior rate of biomass accumulation. (2) a superior rate of actual yield accumulation in order to acquire a high harvest index, and (3) a time to harvest maturity that is neither shorter nor longer than the duration of the growing season. That duration is provided by the environment, which is the fourth major determinant of yield. Simultaneous selection is required because genetically established interconnections among the three major physiological components cause: (a) a correlation between the harvest index and days to maturity that is usually negative; (b) a correlation between the harvest index and total biomass that is often negative, and (c) a correlation between biomass and days to maturity that is usually positive. All three physiological components and the correlations among them can be quantified by yield system analysis (YSA) of yield trials. An additive main effects and multiplicative interaction (AMMI) statistical analysis can separate and quantify the genotype × environment interaction (G × E) effect on yield and on each physiological component that is caused by each genotype and by the different environment of each yield trial. The use of yield trials to select parents which have the highest rates of accumulation of both biomass and yield, in addition to selecting for the G × E that is specifically adapted to the site can accelerate advance toward the highest potential yield at each geographical site. Higher yield for many sites will raise average regional yield. Higher yield for multiple regions and continents will raise average yield on a world-wide basis. Genetic and physiological bases for lack of indirect selection for biomass from exclusive selection for yield are explained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00223805
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  • 10
    Electronic Resource
    Electronic Resource
    Relationship between root elongation rate and diameter and duration of growth of lateral roots of maize (1989)
    Springer
    Plant and soil 119 (1989), S. 271-279 
    Details
    ISSN: 1573-5036
    Keywords: axile root ; maize ; root diameter ; lateral root ; rhizotron ; root elongation rate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The objective of this work was to describe the relationship between elongation rate and diameter of maize roots and to estimate the length and growth duration of lateral roots of maize. Diameters and elongation rates of roots were measuredin situ on plants grown 5 weeks in small rhizotrons under greenhouse conditions. At the end of the experimental period the roots were harvested and diameters of axile and lateral roots were measured. The frequency distribution of diameters of harvested roots was bimodal with a minimum at 0.6 mm; 97% of axile roots were larger than this value and 98% of the lateral roots were smaller. Root elongation per day increased as diameter increased but the slope of the relationship with lateral roots was about 2.5 times that with axile roots when separate linear regressions were fitted to the two populations. The length of lateral roots found on axillary roots between the base and about 30 cm from the apex was approximately 2.2 cm. All of the data was consistent with the hypothesis that the lateral roots grew for about 2.5 days and then ceased growing. The axillary roots continued to grow throughout the experimental period at a rate of about 3 cm day−1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02370419
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