Virulence Diversity and Population Structure of Puccinia striiformis f. sp. tritici in Tibet, China

Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is a major constraint to wheat production in China. Although the disease occurs in Tibet every year under the favorable weather conditions, the virulence diversity and population structure of the Pst population in this region remain poorly understood. In this study, 312 Pst isolates collected in 2025 from five major wheat-growing regions of Tibet (Qamdo, Nyingchi, Lhasa, Shannan, and Shigatse) were characterized using virulence phenotyping and the Pst 5K genotyping-by-target-sequencing (GBTS) platform. Virulence testing on 19 Chinese differentials identified 139 races, including 88 previously reported and 51 novel races, with Su11-3, HY-009-1, and CYR34 being the predominant races. Testing the isolates with 18 Yr single-gene differentials identified 190 virulence phenotypes. None of the isolates were virulent to Yr5 or Yr15, whereas virulence frequencies to the remaining Yr genes ranged from 2.2% to 89.7%. Population genetic analyses using the GBTS data revealed clear regional differentiations. The Nyingchi population formed a distinct cluster with relatively low genomic diversity despite maintaining considerable virulence diversity, whereas the Lhasa and Shannan populations showed extensive admixture.The Qamdo and Shigatse populations consisted of unique genetic components and exhibited relatively high levels of virulence and genetic diversities. Combined virulence and genomic analyses indicated region-specific epidemiological characteristics and suggested that Qamdo may represent an important center of Pst diversification, whereas Lhasa and Shannan may facilitate pathogen dispersal and gene exchange. This study provides the first comprehensive assessment of Pst populations across Tibet and offers valuable information for disease surveillance, resistance breeding, and integrated management of wheat stripe rust in Tibet and neighboring wheat-growing regions.