Analysis of Genetic Diversity of Botrytis Pathogens Causing Broad Bean Chocolate Spot in Qinghai Province

This study investigated the cultural characteristics and pathogenicity isolates of broad bean chocolate spot pathogens collected from 352 fields across 143 villages, 66 towns, and 4 prefectures in Qinghai Province, where broad beans are predominantly cultivated.Genetic diversity analysis was conducted on the dominant Botrytis pathogens causing broad bean chocolate spot, with populations grouped by species and geographical origin.Results showed that the growth rate of Botrytis strains primarily ranged between 20-25 mm/d (68 strains) and 15-20 mm/d (96 strains), indicating an overall rapid growth rate.Based on colony characteristics, spore-type pathogens were the most prevalent.Pathogenicity assays revealed that most pathogens exhibited strong to moderate virulence, with variations in virulence distribution among strains from different geographical origins.Using 15 selected ISSR primers, 235 Botrytis strains were amplified, yielding 166 loci with 100% polymorphism.Analyses indicated genetic differences among strains from different geographical regions, which correlated with their geographical locations, alongside evidence of gene flow between regional populations.Genetic diversity analysis by pathogen species showed scattered relationships and significant genetic differences among populations.This study provides a critical basis for understanding the genetic evolution of Botrytis, the dominant pathogen of broad bean chocolate spot.