Occurrence of Charcoal Rot Caused by Macrophomina phaseolina, an Emerging Disease of Adzuki Bean in China

Adzuki bean (Vigna angularis) is an important legume crop in China. Soil-borne charcoal rot caused by Macrophomina phaseolina (Tassi) Goid is an important and devastating disease of many crops including legumes. During late August and early September, 2014, symptoms similar to charcoal rot were observed on adzuki bean plants in Yulin City of Shanxi Province, and Fangshan County of Beijing, China. This study was conducted to determine the causal agent of the emerging disease on adzuki bean. Four fungal isolates were obtained and identified as M.phaseolina based on morphological and molecular characteristics, including species-specific primer detection and sequences of internal transcribed spacer (ITS) of nuclear ribosomal DNA. The resulting sequences showed 99% identity with more than 60M.phaseolina strains from diverse hosts. The virulence on adzuki bean was verified using pathogenicity tests, producing symptoms similar to those observed in the fields. To our knowledge, this is the first report of M.phaseolina causing charcoal rot on adzuki bean.