Collections of Puccinia triticina in different provinces of China are highly related for virulence and molecular genotype

Collections of Puccinia triticina, the wheat leaf rust pathogen, were obtained from seven provinces in China from 2009 and 2010. Single uredinial isolates were derived and tested for virulence phenotype to 20 lines of Thatcher wheat that differ for single leaf rust resistance genes, and for molecular genotype with 23 simple sequence repeat (SSR) primers. Forty-eight virulence phenotypes were described among the 155 isolates tested for virulence. All but four isolates were virulent to Lr26, and no isolates with virulence to Lr18 or Lr24 were found. The three most common phenotypes, FCBQQ, PCGLN, and PCGLL, were found in five, five, and three provinces, respectively. Thirty-six SSR genotypes were found among the 100 isolates tested for molecular variation. Isolates with identical virulence phenotypes and SSR genotypes were found in more than one province. Analysis of variation showed no overall differentiation of SSR genotypes or virulence phenotypes based on province of origin. The SSR genotypes had high levels of linkage disequilibrium, high levels of observed heterozygosity, and significant correlation with the virulence phenotypes, all measures that indicated clonal reproduction. Bayesian cluster analysis and principle component plots indicated three groups of SSR genotypes that also varied significantly for virulence. The seven provinces are continuously adjacent to each other and likely form a single epidemiological zone for P. triticina.