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1

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Spatio-temporal dynamics of brown rot (Monilinia fructigena) on apple and pear (2001)

Xu, X.-M. ; Robinson, J. D. ; Berrie, A. M. ; [et al.]

Oxford, UK : Blackwell Science Ltd

Plant pathology 50 (2001), S. 0

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ISSN: 1365-3059

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Spatio-temporal development of brown rot (Monilinia fructigena) on apple and pear was monitored in an apple (cv. Cox) orchard and a pear orchard of several cultivars over several years. Disease on individual trees was recorded weekly from July to harvest, individual fruits with brown rot were tagged but not removed and rot-origin identified. On apple cv. Cox and pear (cvs Conference and Comice), all primary rot arose from infection via wounds caused by insects, birds and growth cracks. Birds were the most important wounding agents on pear in the field. Secondary (fruit-to-fruit contact) rot was considerably less than primary rot, especially for pear. Incidence of disease (percentage of fruits with brown rot) increased gradually from late July up to harvest; the final disease incidence varied with seasons and cultivars, ranging from 1 to 11%. For pear, Comice had greater incidence than Conference. Significant aggregation of diseased fruits among trees was detected for assessment dates when the overall incidence of disease was greater than 0·5%. On Cox and Conference, significant correlation of disease incidence between adjacent trees or trees separated by one or more trees (i.e. spatial lag measured as units of distance between adjacent trees) was detected, but there was no clear relationship between the correlation, the distance or time. For Comice, there was consistent and significant positive correlation of brown rot incidence over 3 years. It is speculated that behavioural characteristics of wounding agents may have played an important role in influencing the spatio-temporal dynamics of brown rot on apple and pear.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1046/j.1365-3059.2001.00602.x

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Effects of temperature and relative humidity on conidial germination and viability, colonization and sporulation of Monilinia fructigena (2001)

Xu, X.-M. ; Guerin, L. ; Robinson, J. D.

Oxford, UK : Blackwell Science Ltd

Plant pathology 50 (2001), S. 0

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ISSN: 1365-3059

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Experiments were conducted to investigate the effects of temperature and relative humidity (RH) on the in vitro germination and viability of conidia of the apple brown rot fungus (Monilinia fructigena), and on colonization and sporulation on detached fruits by M. fructigena. Conidia only germinated under near-saturation humidity (≥ 97% RH) and the rate of germination initially increased with temperature to a maximum at ≈ 23–25°C and then decreased. Conidia germinated rapidly – more than 70% of viable conidia had germinated within 2 h at 20 and 25°C. The rate of colonization on detached fruits increased log-linearly with increasing temperature. Sporulation on detached fruits was not observed at 5 or 25°C; sporulation appeared to be unaffected by either temperature (10–20°C) or RH (45–98%) once infection was established. Detached conidia remained viable for a long period of time, up to 20 days, the longest assessment time in this study, depending on storage temperature (10 or 20°C) and RH (45 or 85%). Temperature appeared to be more important than RH in affecting conidial viability. Low temperature and high RH resulted in reduced loss of conidial viability. Storage at 10°C and 85% RH for up to 20 days appeared not to affect conidial viability. These results indicate that environmental conditions during the main UK growing seasons are unlikely to be limiting factors for the development of brown rot on apple.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1046/j.1365-3059.2001.00606.x

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Effects of temperature on the incubation and latent periods of hawthorn powdery mildew (Podosphaera clandestina) (2000)

Xu, X-M. ; Robinson, J. D.

Oxford, UK : Blackwell Science Ltd

Plant pathology 49 (2000), S. 0

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ISSN: 1365-3059

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: The effects of temperature on the length of the incubation and latent periods of hawthorn powdery mildew, caused by Podosphaera clandestina, were studied. At constant temperatures over the range 10–28°C, the incubation period ranged from 5 to 14 days and the latent period from 5 to 16 days; no visible colonies had developed at 30°C after 15 days. The relationships between temperature and the rates of fungus development within the incubation and latent periods were well described by a nonlinear model. The resulting curves were asymmetrically bell-shaped with an optimum temperature of approximately 23°C. The lengths of the incubation and latent periods under fluctuating temperatures were also determined, and were used to evaluate the models developed from constant temperature experiments for their accuracy of prediction. The incubation and latent periods under fluctuating temperature regimes were predicted using a rate-summation scheme with a time step of 24 min, by integrating the respective incubation and latent rate functions obtained under constant temperatures. The predicted incubation or latent periods agreed well with the observed values. Under constant temperature the interval between the times when symptoms and sporulation on the same leaflet were first observed was very short, on average 〈1 day, and was not significantly correlated with temperature. However, this interval was negatively correlated with mean temperature under fluctuating regimes.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1046/j.1365-3059.2000.00520.x

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Yield of doubled haploid lines of Nordic spring barley infected with net blotch, Pyrenophora teres (2000)

ROBINSON, J.

Oxford, UK : Blackwell Publishing Ltd

Plant breeding 119 (2000), S. 0

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ISSN: 1439-0523

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Five Nordic spring barley lines (‘Rolfi’, ‘Arve’, ‘Botnia’, ‘Pohto’ and WW7977) and doubled haploid (DH) populations from a half diallel of crosses between them, were sown in the field in Finland over 2 years and were artificially infected with Pyrenophora teres, the causal agent of net blotch. The purpose of the experiments was to determine the extent of yield loss under net blotch infection in a range of parent barleys and DH populations differing in symptom expression. Analysis of foliar damage symptoms, yield and aerial biomass data indicated that, in both years, there were statistically significant differences among parents and crosses, but the relationships between symptom expression and yield maintenance and between symptom expression and aerial biomass maintenance were stronger in 1997, when yields were higher and net blotch was less severe.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1046/j.1439-0523.2000.00474.x

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Stable resistance in barley to Pyrenophora teres f. teres isolates from the Nordic-Baltic region after increase on standard host genotypes (2000)

Jalli, M. ; Robinson, J.

Springer

Euphytica 113 (2000), S. 71-77

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ISSN: 1573-5060

Keywords: Hordeum vulgare ; net blotch ; resistance

Source: Springer Online Journal Archives 1860-2000

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Abstract Results from tests of a mixture of Finnish net blotch, Pyrenophora teres Drechs. f. teres Smedeg., isolates on a differential series of barley seedlings, comprising 17genotypes, indicated that patterns of infection response (IR)and percentage leaf area damaged (PLAD) were unaffected by differences in seedling size. Variation of the concentration of inoculum between 1,250 conidia ml-1 and 20,000 conidia ml-1 produced similar patterns of IR and PLAD on the differential series. IR and PLAD scored on the second seedling leaf differentiated resistance to P. teres f. teresamong the genotypes better than on the first seedling leaf. Ina second experiment, 120 single-spore P. teres f. teres isolates from Finland, Sweden, Norway, Latvia, Estonia and Ireland were used in tests conducted in the greenhouse to differentiate them in terms of virulence reaction on seedlings of six differential barley genotypes. Each isolate was tested directly following isolation from the leaf material and after having passaged each through barley cvs. Arve or Pohto, to produce 360 isolates in total. Virulence of the isolates differed significantly on the members of the differential series, but differences associated with country of origin and passaging, and interactions, were small. It is concluded that little variation between virulence of P. teres f. teres isolates is evident over a large geographic area, incorporating Nordic and Baltic countries, and Ireland. Barley genotype response to P. teres f. teres appeared to be of more significance than relative virulence of the pathogen isolates. This could simplify breeding barley for improved resistance to this phytopathogen.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1003912825455

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6

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Residual stress prediction and determination in 7010 aluminum alloy forgings (2000)

Tanner, D. A. ; Robinson, J. S.

Springer

Experimental mechanics 40 (2000), S. 75-82

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ISSN: 1741-2765

Keywords: residual stress ; aluminum alloy ; forging ; solution heat treatment

Source: Springer Online Journal Archives 1860-2000

Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Notes: Abstract Precipitation-hardened aluminum alloys gain their high strength through heat treatment involving a severe quenching operation, which can have the adverse effect of introducing residual stresses. The finite element code ABAQUS is used to simulate the quenching of aluminum alloy 7010 in an attempt to predict the residual stress distribution that develops in simple shapes. The rate of heat transfer from the material is determined using the finite element method to predict the heat transfer coefficient from surface cooling curves achieved experimentally. The flow stress of the material is assumed to be strain rate dependent and to behave in a perfectly plastic manner. The predicted residual stress magnitudes and directions are compared to values determined using the holedrilling strain gage method and the X-ray diffraction technique.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF02327551

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