GENETIC-VARIATION IN THE COFFEE BERRY DISEASE PATHOGEN, COLLETOTRICHUM-KAHAWAE

The genetic variation among 25 isolates of Colletotrichum kahawae from widely distributed sources in Africa was studied. Pathogenicity tests on hypocotyls of Coffea arabica cv. Caturra, distinguished a moderate ly aggressive and a highly aggressive group of isolates. Analysis of r estriction fragment length polymorphisms (RFLPs) with a Fusarium oxysp orum ribosomal DNA repeat from the plasmid pDG312 clearly distinguishe d C. kahawae from the other two species, C. gloeosporioides and C. acu tatum, commonly found with the pathogen on coffee. However, no polymor phisms were detected amongst the isolates of C. kahawae. Despite this apparent uniformity in probed DNA, complementation tests with mutants in the nitrate assimilation pathway revealed at least five vegetative compatibility groups (VCGs). This apparent lack of correlation between the RFLP analysis and the variation predicted from the vegetative com patibility grouping may indicate the existence of a teleomorphic stage of the pathogen, which is as yet undiscovered.