Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most destructive diseases worldwide. In China, wheat stripe rust generally occurs in the northwestern and southwestern regions; however, the genetic relationships of Pst populations between these regions are largely unclear. To determine the population structure and potential migration route in these regions, 235 isolates collected from Xinjiang (XJ), Gansu (GS), Ningxia (NX), Shaanxi (SX), Sichuan (SC), and Yunnan (YN) provinces in 2021 and 2022 were phenotyped using two sets of Pst differentials and genotyped using 20 competitive allele-specific PCR-single nucleotide polymorphism (KASP-SNP) markers. The phenotype tests indicated that CYR34, CYR32, and CYR33 were the predominant races with different occurrence frequencies in different regions and years. Genotypic analysis revealed that a total of 183 multilocus genotypes (MLGs) were identified, and the genetic diversity in the YN subpopulation was the highest. The genetic background in the SX subpopulation is similar to the GS and NX subpopulations, and the YN subpopulation is similar to that of SC and SX. A high level of gene flow (Nm) was found between the SX and GS, SX and NX, GS and NX, and SC and YN subpopulations, respectively, suggesting the migration of Pst among these regions, while a small amount of Nm existed between the SX and SC subpopulations. SC may funct as a bridge connecting Pst subpopulations between the northwestern provinces (SX, GS and NX) and southwestern provinces (SC and YN). With relative high genetic distance and low Nm values to other Pst subpopulations, XJ is considered as a relatively independent epidemiological region in China. These results improved our current understanding of wheat stripe rust epidemic in northwestern and southwestern of China.
Keywords: Genetic diversity; Puccinia striiformis f. sp. tritici; northwestern and southwestern China; population structure; wheat.