Virulence and diversity of Puccinia striiformis in South Russia

Abstract

Puccinia striiformis causes wheat yield losses in all countries where wheat is cultivated. Virulence and diversity of the P. striiformis were assessed in 2013–2018 in South Russia, and this showed that the North Caucasian population of the pathogen was diverse. One hundred and eighty two virulence phenotypes were identified in 186 P. striiformis isolates. Among isolates collected in 2014, 2015, and 2018, all phenotypes were unique. In the 2013 and 2017 populations, phenotypes with few (one to eight) virulence alleles prevailed. In the 2014, 2015, and 2018 populations, most of the phenotypes contained greater numbers (nine to 19) of virulence alleles. Over the 5 years of research, the pathogen population lacked isolates virulent to the host Yr resistance genes 3, 5, 26, and Sp. Single (from 1 to 5%) occurrences of isolates virulent to host lines with Yr genes 3a, 17, 24, 3b + 4a + H46, and 3c + Min were identified. Differences in frequencies of virulence alleles between years in the P. striiformis populations (Ney indices, N) were generally non-significant (N = 0.11 to 0.23), with the exception of the populations in 2013 and 2017 (N = 0.37). The minimum N values was found for the populations of 2015 and 2018 (N = 0.10). Over the five years of this study, the dynamics of the virulence of the population and jumps in the frequency of isolates with respect to many Yr genes were identified. This feature of the P. striiformis populations in South Russia, combined with high phenotypic diversity, indicates the ability for rapid race formation and morphogenesis in response to changes in biotic and abiotic factors.