Vegetative Compatibility Groups and Pathogenicity Among Isolates of Fusarium oxysporum f. sp. cucumerinum.

Seventy-eight isolates of Fusarium oxysporum f. sp. cucumerinum, the causal agent of cucumber wilt, were isolated from symptomatic tissues of cucumber from four provinces in Korea. These isolates were grouped into vegetative compatibility groups (VCGs) by demonstrating heterokaryosis by complementation tests using nitrate nonutilizing (nit) mutants. All isolates were grouped into six VCGs-1-A, 1-B, 1-C, 1-D, 1-E, and 1-F. No self-incompatibility was observed in any of the isolates tested. VCG 1-A was the most common group within growing regions in Korea and proved to be the most virulent of the VCGs identified. These data indicate that the level of virulence in F. oxysporum f. sp. cucumerinum is related to VCG.