Stem canker disease of Phaseolus vulgaris caused by Paramyrothecium roridum in Iran

Brown circular stem canker symptom was observed on common bean plants in Mahallat county, Markazi province, Iran, in the summer of 2022. Five identical associated fungal isolates were recovered from the infected plants. Morphological and molecular characterization of the representative isolate (UTR38) using the partial sequence of beta-tubulin, and as well as RNA polymerase II second largest subunit loci was done. The associated fungus was identified as Paramyrothecium roridum. Pathogenicity of the isolate UTR38 was conducted on six-week-old seedling stems of the P. vulgaris cultivar Sunray. The inoculated fungus was also reisolated from the inoculated plants to fulfill the Koch’s postulates. According to the results, this is the first report of P. roridum as the causal agent of stem canker disease in P. vulgaris in Iran and worldwide.