VIRULENCE AND MOLECULAR DIVERSITY IN COLLETOTRICHUM-LINDEMUTHIANUM FROM SOUTH, CENTRAL, AND NORTH-AMERICA

Isolates of Colletotrichum lindemuthianum (138 total) from Argentina, Brazil, the Dominican Republic, Honduras, Mexico, and the United State s were characterized into 41 races based on virulence to 12 differenti al cultivars of Phaseolus vulgaris. These 41 races were categorized in to two groups: those found over a wide geographic area and those restr icted to a single country. Races 7, 65, and 73 were widespread. Race 7 3 was the most common (28%). Race 7 was found once in Argentina and Me xico but at a higher frequency in the United States. Race 65 was found repeatedly in Brazil and the United States. Although 39% of the races were detected repeatedly and three races were widespread, no race was isolated from both P. vulgaris gene pools. Phenetic analyses showed n o obvious patterns correlated with virulence clusters. No geographic p attern was evident. Molecular polymorphism generated by random amplifi ed polymorphic DNA confirmed the extensive variability in virulence of C. lindemuthianum. Virulence phenotypes were grouped into 15 clusters . The two largest clusters contained isolates from all the geographic regions sampled. Molecular polymorphism was observed among isolates fr om races 65 and 73 within and among countries, except among Brazilian isolates of race 65. The genetic diversity of C. lindemuthianum was gr eatest in Mexico and Honduras. Our data suggest that C. lindemuthianum may not be highly structured to specific Phaseolus gene pools.