Epidemiology of Stemhylium blight on lentil (Lens culinaris) in Saskatchewan
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Stemphylium blight is a defoliating fungal disease caused by Stemphylium botryosum. It has become more prevalent in Saskatchewan. Although not much is known about the biology of the fungus, increasing lentil (Lens culinaris) yield losses of up 62% have been reported in Bangladesh and India. The infection of lentil by S. botryosum was investigated under a range of temperatures (5 to 30°C), wetness periods (0 to 48 h) and wetness periods interrupted by dry periods of 6 to 24 h. The experiments involved testing the impact of environmental conditions on germination of conidia on glass slides and stemphylium blight infection on lentil (cv. CDC Milestone). Generalised linear models and non-parametric tests were used to determine the effects of these factors on conidial germination and disease development. Infection levels increased with increasing temperature and wetness duration. A latent period of 48 h was observed at 25°C and 30°C under continuous wetness. The duration of the latent period increased with decreasing temperatures and decreasing wetness duration. S. botryosum required warm temperatures (above 25°C) and a minimum wetness period of 8 h for optimal disease development. Low levels of infection were observed within the first 2 h of incubation at 10°C and increased with longer wetting periods up to 48 h and temperatures up to 30°C. The pathogen could maintain infectivity during interrupted wetness periods despite its requirement for prolonged wetness periods. Infection levels were not significantly affected by interrupting dry periods of 6 to 24 h although long dry periods (24 h) combined with higher temperatures (30°C) resulted in a decrease in stemphylium blight severity. Germination studies on glass slides supported these findings. Response surface models were developed that provided a good fit for the response of conidial germination to temperature and wetness duration. The coefficients of determination for the regression of observed against predicted effects ranged from 0.88 to 0.97. The general additive model could also be used to predict stemphylium blight severity responses to temperature and wetness duration (scaled deviance = 1.04). However, that model tended to overestimate infection levels especially at lower temperatures. The coefficients of determination for the observed against predicted effects at 5 to 30ºC ranged from 0.77 to 0.92 for the general additive model.
DegreeMaster of Agriculture (M.Agr.)
Copyright DateApril 2006