A Local Siberian Sample of <i>Puccinia graminis</i> f. sp. <i>tritici</i> Showing Great Differentiation From the Pathogen in Neighbouring Regions

ABSTRACT The occurrence of wheat stem rust has increased significantly in various regions of the European and Asian parts of the Russian Federation in recent decades. Despite several stem rust outbreaks in Western Siberia, the pathogen Puccinia graminis f. sp. tritici (Pgt) was never surveyed in the Kemerovo region, where wheat crops occupy more than 350,000 ha. A set of 30 Pgt single pustule isolates was obtained in 2021 from field bulk samples during the regional pathogen survey in 2020–2022. Virulence and simple‐sequence repeat (SSR) analyses revealed the uniqueness of the Kemerovo Pgt sample among the neighbouring Novosibirsk and Altai regions of Western Siberia. The relative virulence complexity was low. All nine virulence phenotypes identified for the Kemerovo Pgt isolates were closely related, being avirulent on 15 wheat differentials. Cases of virulence to Sr24 and avirulences to Sr5 , Sr9d , Sr10 , Sr17 and SrMcN were detected, that are uncommon for the Pgt pathogen in Western Siberia. The SSR genotypes were also closely related, although all but one of them were clearly separated into two groups characterised by fixed homozygous and heterozygous states at Pgestssr293 locus. This locus could serve as an indicator for tracking the dynamics of the Kemerovo Pgt sample on a microevolutionary level regardless of virulence selection. Highly significant differentiation of the Kemerovo Pgt sample from the neighbouring regions and regional wind directions make west‐to‐east pathogen migration and exogenous origin of the primary inoculum very improbable, and raises a hypothesis of local infection coming from wild grasses.