Predicting Wheat Leaf Rust Severity Using Planting Date, Genetic Resistance, and Weather Variables

Abstract

Leaf rust epidemics of wheat, caused by Puccinia recondita f. sp. tritici, were analyzed for the 1972 to 1990 growing seasons. The disease severity values recorded for leaf rust in early and late bread-wheat planting dates at Pergamino were used to identify the best genetic and environmental predictors of disease severity. Leaf rust severity (early planting date) could be predicted (R2 = 0.88) as a function of heat accumulation (base daily mean temperature >12°C), days with relative humidity >70% without precipitation, and a cultivar resistance index. For late planting date, the predictive value of meteorological variables decreased, while the importance of the resistance index increased over that found for the early seeded trials. In general, predicted and observed leaf rust severity levels agreed during 1994 to 1996 at Pergamino, and for trials (1991) that were grown at some distance from the area where the original data for model development were recorded.