Diaporthe Diversity and Pathogenicity Revealed from a Broad Survey of Soybean Stem Blight in China

Many species in the fungal Diaporthe (anamorph Phomopsis) genus have become a group of the most important pathogens that cause seed decay, stem and pot blight, and stem canker in soybean production worldwide, resulting in significant yield loss. Due to increased disease prevalence but a lack of research, we performed an extensive field survey to isolate and identify the Diaporthe species associated with soybean stem blight in six provinces of China between 2019 and 2020. A total of 92 Diaporthe isolates were identified based on morphological and multilocus phylogenetic analysis and classified into six species: D. longicolla, D. unshiuensis, D. sojae, D. caulivora, D. tectonigena, and an unknown Diaporthe sp. The most frequently identified species was D. longicolla with 57 isolates. High genetic diversity was observed for the D. longicolla isolates, and haplotype network analysis revealed a mixed structure among the population in the six provinces. In comparative pathogenicity assays, different virulence levels were observed among the 92 Diaporthe isolates. The results of this study provide new insights into the Diaporthe spp. associated with soybean stem blight in China and can help in the development of effective management strategies.