Nigrospora musae and N. oryzae as new causal agents of broad bean leaf spot disease in China

Abstract

Broad bean (Vicia faba L.) is a cold-season legume crop, planted worldwide for its superior nutritional value and important role in sustainable agriculture. Leaf spot is one of the major diseases on broad bean leaves, stems and pods, the infections will result in severe yield reduction. In 2021, a leaf spot disease was extensively observed on broad bean plants in Longli County and Guiyang, Zunyi and Liupanshui Cities, Guizhou Province, China. Based on morphology and phylogenetic analysis using the ribosomal internal transcribed spacer region (ITS), 28S rRNA gene (LSU), β-tubulin (TUB2) and translation elongation factor 1-alpha (TEF1-α) gene sequences, the 12 isolates in this study represent two species of Nigrospora, namely N. musae, and N. oryzae. Moreover, the isolates of the two Nigrospora species found in the survey were tested for pathogenicity and indicated that they were all pathogenic to the broad bean plants. Same pathogens were successfully reisolated from the typical leaf spot lesions. Koch's postulates for N. musae and N. oryzae were fulfilled in this study. Thus, this study confirms species of Nigrospora as causal agents of leaf spot disease on broad bean in China, which provides a basis for subsequent research to develop effective preventative measures.