Population Genetic Analysis of From Tobacco in Chongqing, Southwestern China.

Tobacco black shank, caused by , is one of the most notorious tobacco diseases and causes huge economic losses worldwide. Understanding the genetic variation of populations is essential to the development of disease control measures. In this research, 210 simple sequence repeat (SSR) markers for were identified, 10 of which were polymorphic among nine reference strains. We further performed population genetic analysis of 245 isolates randomly collected from tobacco fields in Chongqing for mating type, molecular variation at 14 SSR loci (four of which were identified previously), and sensitivity to the fungicide metalaxyl. The results showed that the A2 mating type was dominant and no A1 mating type isolate was discovered. SSR genotyping distinguished 245 isolates into 46 genotypes, four of which were dominant in the population. Low genotypic diversity and excess heterozygosity were common in nearly all of the populations from Chongqing. Population analysis showed that no differentiation existed among different populations. All isolates tested were highly sensitive to metalaxyl. Taken together, our results showed that the populations from tobacco fields in Chongqing belonged to a clonal lineage and were highly sensitive to metalaxyl.