| Summary: | Stripe rust, caused by <i>Puccinia striiformis</i> f. sp. <i>tritici</i> (<i>Pst</i>), is one of the most important fungal diseases affecting wheat (<i>Triticum aestivum</i> L.) worldwide. In this study, the genetic diversity and population structure of <i>Pst</i> isolates were analyzed using 15 microsatellite markers. Isolates were collected from five wheat cultivars with different levels of resistance from Yanting county and Fucheng district, Mianyang city, Sichuan province, China. The aim of this study was to investigate whether <i>Pst</i> populations are differentiated by wheat genotype or geographic origin. Seventy-six multilocus genotypes (MLGs) were identified from all 289 single uredinial isolates. In general, the genotypic diversity of <i>Pst</i> populations from five wheat cultivars in Fucheng was higher than that in Yanting. In addition, the genetic diversity was highest in the <i>Pst</i> populations from Mianmai 367, a cultivar considered to be highly resistant. The unweighted pair group method with arithmetic mean (UPGMA) phylogenetic tree, Bayesian clustering analysis, and minimum spanning network for the MLGs revealed two major genetic clusters based on geographical location. Greater differentiation was observed between the populations from the two sampling locations than between the populations from different hosts in the same location. The results suggest that geographic and environmental differences could partially explain the genetic differentiation of <i>Pst</i> more than wheat genotype. This study provides novel insight into the interactions between <i>Pst</i> populations and their hosts. The results could be helpful in designing more effective management strategies for stripe rust in wheat production.
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