Molecular Detection, Aggressiveness, and Vegetative Compatibility of Macrophomina phaseolina Isolates from Common Bean Fields in Sinaloa, Mexico

Charcoal rot of common bean, caused by Macrophomina, is one of the most economically important diseases worldwide. In Mexico, charcoal rot of bean has been associated exclusively with M. phaseolina; however, in recent years, new Macrophomina species affecting various crops have been described globally. Information on this pathogen in common bean in Mexico remains limited. Therefore, the objectives of this study were to characterize Macrophomina isolates obtained from bean fields in northern Sinaloa morphologically and molecularly using species-specific primers, and to determine their aggressiveness and vegetative compatibility groups (VCGs). During the 2020–2021 growing season, 50 Macrophomina isolates were obtained from common bean tissues exhibiting charcoal rot symptoms collected from 12 fields in the municipalities of Ahome and Guasave, Sinaloa, Mexico. Molecular analysis using species-specific primers for three Macrophomina species (M. phaseolina, M. pseudophaseolina, and M. euphorbiicola) identified all 50 isolates as M. phaseolina. Pathogenicity tests indicated that the M. phaseolina isolates differed in aggressiveness toward common bean plants. Mycelial compatibility assays revealed at least seven vegetative compatibility groups among M. phaseolina isolates distributed across northern Sinaloa. To our knowledge, this is the first study to provide phenotypic characterization, aggressiveness assessment, vegetative compatibility grouping, and species-specific primer-based identification of M. phaseolina isolates from common bean fields in Sinaloa, Mexico.