Isolation, characterization and genetic diversity analysis of Bipolaris sorokiniana (Sacc.) Shoen., the causal agent of spot blotch of wheat using molecular markers

The spot blotch disease caused by Bipolaris sorokiniana is one of the most important diseases of wheat worldwide. The knowledge about genetic structure of fungal pathogens is important to design appropriate strategy to control the disease. In this study, a total of 46 samples were isolated, purified and characterized from samples collected from Mazandaran and Golestan provinces. Pathogenicity tests showed that isolates were able to cause typical spot blotch symptoms on Bulani as the susceptible cultivar. Genetic diversity analysis of isolates using 17 ISSR and RAPD markers showed that out of 179 amplified bands, 98 were polymorphic. The average of amplified bands for each marker was 10.4, while the average of polymorphic bands was calculated 5.6 for each marker. The average PIC value was 0.32 ranging from the highest PIC value (0.41) for the ISSR marker, UBC874, to the lowest PIC value (0.18) for the RAPD marker, OPF2. Cluster analysis of banding pattern data showed that populations of this fungus had a high genetic diversity. Based on bootstrap analysis the isolates were differentiated with a high genetic distance to seven distinct groups. Highly distinct clusters belonging to different geographic regions revealed that there were high genetic differences between fungal populations indicating that fungal populations might be adapted to different climate regions.