Regional Virulence Differentiation of Puccinia striiformis f. sp. tritici in Russia During 2024–2025

Yellow (stripe) rust, caused by Puccinia striiformis f. sp. tritici (Pst), is a devastating disease of common wheat worldwide. The virulence variability of Pst isolates from common wheat was studied in geographically distant Russian regions (the North Caucasus, North-West, Volga, and Urals), which differ in climatic and environmental conditions, types of cultivated wheat (winter vs. spring wheat), and genotypes of commercial cultivars. A total of 95 isolates were tested for virulence on a differential set comprising 12 Avocet near-isogenic lines and 15 supplemental wheat varieties. In total, 38 distinct Pst pathotypes were identified: seven of them were detected in two regions, while a single pathotype was shared by three regions. Most pathotypes from the North Caucasus and North-West were clearly distinct from pathotypes in the Volga and Ural regions. The regional Pst collections were clearly divided into two major clusters: the first comprising the North-West and North-Caucasian collections (Dagestan, Krasnodar, and Rostov), and the second comprising the Volga and Ural collections. No virulence was detected to Yr5, Yr10, Yr15, Yr24, and the Moro variety. Isolates virulent to Yr17 were identified in the North Caucasus (Dagestan, Krasnodar, and Rostov) and Urals; however, no virulence to Yr17 was observed in the North-West and Volga regions.