DNA-FINGERPRINTING AND VEGETATIVE COMPATIBILITY ANALYSIS INDICATE MULTIPLE ORIGINS FOR VERTICILLIUM-DAHLIAE RACE-2 TOMATO ISOLATES FROM ONTARIO, CANADA

RFLP, DNA fingerprinting and VCG methods were used to characterize fou rteen Verticillium? dahliae isolates collected from southwestern Ontar io, Canada. The isolates were typed as not pathogenic to tomato (NP), race I (avirulent on cvs carrying the Ve resistance gene) or race 2 (v irulent on Ile cvs). On the basis of RFLPs, RAPDs, and DNA fingerprint s detected by hybridization to a dispersed, repetitive genomic DNA pro be, the isolates were classified into Eve DNA types. Type I included t wo NP isolates. Type II included four race 2, and three NP isolates. T ypes III and V were represented by single race 2 and race I isolates. respectively Type IV included one race 2, and two race I isolates. Veg etative compatibility was determined for selected NP, race I, and race 2 isolates of each race type/DNA type combination. Isolates of the sa me DNA type were compatible, as were type II and III isolates (VCG 4B) , and type IV (VCG 2A) and V isolates (VCG 2B). These data show a leve l of genetic diversity not previously identified in the V. dahliae tom ato pathogen population, and suggest multiple origins for the Ontario race 2 pathotype.