Genetic diversity of Phaeoisariopsis griseola in the state of Minas Gerais, Brazil

Due to the importance of common bean angular leaf spot in the state of Minas Gerais-Brazil and to the great variability of the pathogen, Phaeoisariopsis griseola, monitoring races becomes an important tool for breeding programs aiming at genetic resistance. The pathogenic variability of 30 isolates of the P. griseola, collected from various locations in the state of Minas Gerais, was studied using the following common bean differential series (Don Timoteo, Bolon Bayo, Montcalm, G 5686, Amendoin, G 11796, BAT 332, PAN 72, Cornell 49-242, Mexico 54, Flor de Mayo and G 2858). The first trifoliate leaf was inoculated with a 2 x 10(4) conidia/mL. Plants were maintained at 20-22 degreesC and 95% relative humidity for 48 hours. Symptom evaluation was performed 15 days after inoculation. Thirteen races were identified demonstrating the wide genetic variability of the pathogen in the state of Minas Gerais. Race 63.63 was the most virulent, whereas race 63.23 was the most frequent (10 of 30 isolates), being widely distributed among the regions studied. The virulence phenotype indicated that the races studied belonged to the Mesoamerican group, which was confirmed when the 30 isolates were compared to Andean and Mesoamerican standards using RAPD markers.