Analysis of the effects of climate, host resistance, maturity and sowing date on wheat stem rust epidemics

Under appropriate environmental conditions, stem rust (caused by Puccinia graminis Pers.:Pers. f. sp. tritici) is a destructive disease of wheat crops worldwide. Although fungicide application and host genotype resistance are the most commonly used methods to control wheat stem rust, efficient agronomic methods are needed to lower disease management expenses and improve sustainability of wheat production. However, an understanding of highly effective agronomic practices to control stem rust is still lacking. From 2013 to 2017, 282 wheat-stem-rust progress curves were studied using three agronomic, three climatic, and two disease variables at plot scale in Kermanshah province, Iran. Cultivar, sowing date, and disease-assessment time significantly affected stem rust severity. From principal component analysis (PCA), three principal components explained 79% of data variance. According to PCA and multiple regression model, AUDPC corresponded with disease-onset and maturity date, mean minimum temperature and number of rainy days over designated spring months, number of days with minimum temperature within 5–20 °C and maximum relative humidity above 60%, resistance index, and sowing date. These new findings suggested improvement of current predicting models by involving dates of maturation and sowing, and wheat resistance besides rainfall-temperature-wetness variables for more effective, economic and sustainable management of stem rust epidemics.