The Virulence and Genetic Diversities of Puccinia striiformis f. sp. tritici in Shaanxi, Gansu, and Qinghai Provinces, China

Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most significant wheat diseases in China. Gansu and Qinghai provinces are critical oversummering areas for Pst, while Shaanxi functions as an epidemiological bridge facilitating pathogen dispersal from northwestern regions to eastern wheat-growing zones, however the genetic relationships between populations of Pst in these provinces are not well understood. A total of 167 Pst isolates were collected from Shaanxi, Gansu, and Qinghai provinces in 2022, phenotyped for virulence using two sets of Pst differential host, and genotyped using 23 Kompetitive allele-specific PCR-single nucleotide polymorphism (KASP-SNP) markers. The phenotypic results showed that the Guinong 22 race group, CYR34, and CYR32 were the predominant races or race groups with different occurrence frequencies in different provinces. Genotyping analysis revealed 122 multilocus genotypes (MLGs), and the Shaanxi Pst population exhibited the highest genetic diversity with the Shanon’s information index (I) 0.66. The genetic structures of the Pst populations in Shaanxi, Gansu, and Qinghai were similar and the Nei's genetic distances from 0 to 0.0025, of which, Shaanxi and Gansu Pst populations were more similar with Nei's genetic distances 0.0019. The highest gene flow (Nm=62.25) was observed between the Baoji subpopulation in Shaanxi and the Tianshui subpopulation in Gansu. Overall, the Pst sources of Shaanxi and Qinghai were mainly from Gansu. These results provide a theoretical basis for the prediction of the occurrence of stripe rust epidemics and effective disease management in China.