CHARACTERIZATION OF FUSARIUM-OXYSPORUM F-SP PHASEOLI BY PATHOGENIC RACES, VCGS, RFLPS, AND RAPD

Isolates of Fusarium oxysporum were obtained from the vascular tissue of Phaseolus spp. and characterized by pathogenicity, vegetative compa tibility, restriction fragment length polymorphisms (RFLPs), and rando m amplified polymorphic DNA (RAPD) analyses. Eleven isolates were F. o xysporum f. sp. phaseoli and comprised five pathogenic races. Two race s, nine vegetative compatibility groups (VCGs), and three heterokaryon self-incompatible isolates are new reports for this forma specialis. Pathogenic and nonpathogenic isolates were not found in the same VCGs and, in some cases, there was a correspondence of VCG to race and plac e of origin. RFLPs with five different restriction enzymes and RAPD wi th four different primers indicated genetic diversity in F. oxysporum f. sp. phaseoli. The banding patterns showed a correspondence to the V CGs, but not to the pathogenic races. RFLPs and RAPD markers could be used to distinguish isolates that were nonpathogenic, self-incompatibl e, and from obscure origins. The use of all four methods combined was effective in characterizing and providing insight into the complex rel ationship of F. oxysporum f. sp. phaseoli.