Vegetative Compatibility Groups in Colletotrichum coccodes Subpopulations from Australia and Genetic Links with Subpopulations from Europe/Israel and North America

Abstract

Vegetative compatibility of 94 isolates of Colletotrichum coccodes from Australia originating from potato, soil, and a weed (Solanum esuriale) was tested using nitrate-nonutilizing (nit) mutants. Isolates distributed to six vegetative compatibility groups (VCGs), five of them multimember (24.5, 23.4, 13.8, 12.8, and 7.5% distribution) and only one composed of two isolates (2.1%); 15.9% of them were not assigned to any of the VCGs. Aggressiveness of 51 isolates representing all six VCGs was tested by mature green tomato bioassay: isolates assigned to AUS-VCG-4 were the most aggressive and those in AUS-VCG-3 the least (P < 0.05). Isolates from warmer climates and lower latitudes were more aggressive (P < 0.05). In addition, we report for the first time complementations between isolates from Australia (AUS); North America (NA); and Israel, The Netherlands, Scotland, France, Germany (EU/I). Isolates assigned to AUS-VCG-4 anastomosed with isolates assigned to EU/I-VCG-7 and NA-VCG-5 (which also anastomosed with each other). Isolates assigned to EU/I-VCG-6 anastomosed with isolates assigned to NA-VCG-2 and isolates assigned to AUS-VCG-2 anastomosed with isolates assigned to EU/I-VCG-2. The linkage between subpopulations could result from the limited exchange of seed tubers among continents, or could be due to, for instance, gene flow, selection, or a limited number of polymorphic vegetative incompatibility genes.