SSR-based analysis of structural variation of the Russian population of Puccinia striiformis f. sp. tritici in 2019–2021

The importance of monitoring and management of yellow rust, caused by Puccinia striiformis f. sp. tritici (Pst), has markedly increased in Russia over recent years because of intensifying negative effects of this destructive disease on wheat production. The Pst virulence survey was conducted in 2019–2021 in the European (North-West, Volga, North Caucasus) and Asian (Siberia) parts of Russia, and the same 109 isolates have been genotyped here with 20 SSR markers. Fifty-three multilocus genotypes (MLGs) were detected, seven of which occurred in two or more regions. The most frequent MLG was found in three European Pst collections (except Dagestan) and Siberia. SSR-based variation within the regional collections was low because many MLGs were closely related. Nevertheless, each collection contained relatively different small genotype groups. No clear geographic structure of the Russian Pst population was observed because the five studied regional collections shared groups of similar genotypes. The most singular SSR genotype was identified in the North-West collection, but genotypes of four invasive isolates belonging to the PstS2 temperature-adapted aggressive strain did not considerably differ from others. The observed heterozygosity at all SSR loci exceeded the expected one in all regional Pst collections, which could imply asexual reproduction of the pathogen. Both the SSR and virulence analyses demonstrated similar patterns of relationships between the regional Pst collections, although the magnitude of differences between the collections was larger for virulence pathotypes. However, no significant association was established between the virulence pathotypes and SSR genotypes because multiple pathotypes had the same genotype and vice versa.