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

Charcoal rot of common bean, caused by <i>Macrophomina</i>, is one of the most economically important diseases worldwide. In Mexico, charcoal rot of bean has been associated exclusively with <i>M. phaseolina</i>; however, in recent years, new <i>Macrophomina</i> 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 <i>Macrophomina</i> 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 <i>Macrophomina</i> 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 <i>Macrophomina</i> species (<i>M. phaseolina</i>, <i>M. pseudophaseolina</i>, and <i>M. euphorbiicola</i>) identified all 50 isolates as <i>M. phaseolina</i>. Pathogenicity tests indicated that the <i>M. phaseolina</i> isolates differed in aggressiveness toward common bean plants. Mycelial compatibility assays revealed at least seven vegetative compatibility groups among <i>M. phaseolina</i> 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 <i>M. phaseolina</i> isolates from common bean fields in Sinaloa, Mexico.