Study of Virulence Factors of Causal Agent of Wheat Leaf Rust (Puccinia triticina Eriks.) in Iran during 2017-2021

Wheat leaf rust caused by Puccinia triticina Eriks is one of the most important wheat disease due to its wide distribution and yield loss in the world. Racial variation and emergence of new races leads to break the resistance of resistant wheat cultivars. To study these changes and to identify the virulence of P. triticina Erkis., a research project was carried out by planting trap nurseries in four cropping seasons (2017-2021) in Karaj, Gorgan, Gharakhil, Kalardasht, Ardebil, Moghan, Boroujerd, Ahvaz and Dezful. At flag leaf stage and when maximum disease infection on susceptible check was observed, the disease severity and infection type were scored based on the Modified Cobbs Scale and Rolfes et al. method, respectively. According to the results of this study, during four growing seasons in different locations, no virulence was observed on varieties with Lr2a, Lr2b, Lr19, Lr34 gene(s) and the Lr10/Lr27+/Lr31 gene combination, and these genes were identified as effective for wheat leaf rust disease in Iran. Virulence was observed on varieties carrying other resistance gene(s), at least in one test location, and indicated that the above genes were ineffective in those region. Differential lines carrying Lr22a and Lr21 genes, with resistance reaction in most seasons, were effective genes, following the aforementioned genes, for resistance to wheat leaf rust in Iran, respectively.