Wheat stripe rust epidemics in interaction with climate, genotype and planting date

Stripe rust is a potential threat to wheat production in the world. From 2013 to 2017, a total number of 282 stripe rust progress curves were characterized at the plot scale in Kermanshah province, Iran, according to a number of agro-ecological traits. Disease incidence and severity varied by cultivar, planting date, sampling time and year. Area under disease progress curve (AUDPC) on a severity rating basis was ranked according to the Kruskal-Wallis one-way ANOVA. H-test comparisons among cultivars showed greater mean AUDPC values for cvs. Sivand, Bahar and Chamran II, while cv. Pishgam had a lowest AUDPC value. Mean AUDPC value for early disease onset was greater than that for late disease onset. Greater AUDPC corresponded to smaller resistance index ranging from 0 to 70. Highest and lowest AUDPC occurred in spring 2016 and 2015, respectively. From principal component analysis, three principal factors accounting for 84% of the total variance evidenced dependence of stripe rust development on air temperature and moisture, disease-onset and maturity date, resistance index, and planting date. From regression analysis, the number of days with minimum temperatures within the range of 5–12 °C and RH above 60%, disease-onset and maturity date, resistance index, and planting date accounted for 62% of variations in AUDPC values. The present findings emphasize careful selection of cultivar resistance, maturity and planting dates, along with climatic descriptors, to improve accuracy of disease prediction models, durability of cultivar resistance to stripe rust, and sustainability of disease management programs.