BIODIVERSITY, EPIDEMIOLOGY AND VIRULENCE OF COLLETOTRICHUM-GLOEOSPORIOIDES - I - GENETIC AND PATHOGENIC DIVERSITY IN COLLETOTRICHUM-GLOEOSPORIOIDES ISOLATES FROM STYLOSANTHES-GUIANENSIS

Anthracnose, caused by Colletotrichum gloeosporioides, is the most imp ortant and widespread disease of Stylosanthes, a diverse tropical and subtropical forage legume naturally distributed in central and South A merica. This paper compares the genetic and pathogenic diversity of 45 isolates, which originated from S. guianensis genotypes. Published in formation on the pathogenic diversity of these isolates on a set of 12 S. guianensis was used. The amount of genetic diversity was measured at molecular level by polymerase chain reaction amplifications of DNA with 9 arbitrary primers of 10 bases each using the Random Amplified P olymorphic DNA (RAPD) markers. The amplifications revealed scorable po lymorphism among the isolates, and a total of 80 band positions were s cored. Using Ward's method (N = 6) of statistical analysis, the isolat es were separated into 6 clusters. Generally, isolates were clustered together by their geographic origin and/or their original host genotyp e. Isolates from Carimagua, Colombia, a savanna ecosystem and a long-t ime Stylosanthes breeding and selection site, exhibited a relatively w ider range of genetic diversity than those from a newly opened trial s ite in the Amazon basin of Colombia. No strict correlation existed bet ween genetic diversity, as measured by RAPD, and differential virulenc e, as defined by the pathotype. Isolates of the same pathotype/RAPD gr ouping often originated from the same host genotype and/or geographica l locality. This information will be useful in determining future samp ling strategies for the pathogen population.