Comparison of genetic diversity and pathogenicity among Fusarium culmorum isolates, the causal agent of wheat root and crown rot disease in Varamin fields

Fusarium culmorum, is one of the most important causal agents of crown rot of wheat in Iran. Simple sequence repeats or microsatellite (SSR) and virulence assays were used to investigate genetic variability among 49 isolates of F. culmorum collected from wheat fields in three districts of Varamin. Eight pairs of single-locus microsatellite markers were used to analyze the genomic DNA of isolates. The result of analysis showed that all loci were polymorphic and the numbers of alleles ranged between two to six with an average of 3.75 per locus. Cluster analysis of SSR data revealed that 49 isolates clustered into five distinct groups. The index of multilocus association was calculated using SSR data and 44 multilocus haplotypes were detected among 49 isolates. The results of this study indicated that a there was a high level of genetic diversity (0.528) among the isolates examined, and genetic similarity among Varamin isolates was less than those obtained from Pishva and Javad-abad regions. In addition, pathogenicity of the isolates was tested on a bread wheat cv. Bolani under greenhouse conditions. A significant difference for pathogenicity was found among the isolates. Comparison of the means showed that the isolates of Varamin districts were more pathogenic than Javad-abad and Pishva districts. The significant difference in the genetic diversity and pathogenicity of the Varamin’s isolates in comparison to the other districts suggests that there is a potential for the occurrence of new genotypes with greater virulence in this district. The statistically no correlation was observed between molecular variation and pathogenicity.