Vegetative Compatibility Among Fusarium oxysporum f. sp. basilicum Isolates Recovered from Basil Seed and Infected Plants. WADE H. ELMER, Department of Plant Pathology and Ecology, Connecticut Agricultural Experiment Station, Box 1106, New Haven 06504. ROBERT L. WICK and PATRICIA H AVILAND, Department of Plant Pathology, University of Massachusetts, Amherst 01003. Plant Dis. 78:789-791. Accepted for publication 2 May 1994. Copyright 1994 The American Phytopathological Society. DOI: 10.1094/PD-78-0789.

Forty-five isolates of Fusarium oxysporum f. sp. basilicum were used in heterokaryon tests to classify isolates into vegetative compatibility groups (VCGs). Nitrate nonutilizing mutants were selected from isolates obtained during 1991-1993 from diseased basil plants and infested seeds from California, Colorado, Connecticut, Massachusetts, Nevada, New York, South Carolina, and Italy. An Italian isolate of F. o. basilicum (ATCC 38560) deposited by researchers in 1975 was included also. All isolates except NY63 from New York were vegetatively compatible with each other and were virulent on susceptible basil in the greenhouse. Because isolates of F. o. basilicum may represent a unique VCG, heterokaryon tests could replace the lengthy pathogenicity tests and reduce the amount of time necessary to distinguish nonpathogenic isolates of F. oxysporum from isolates of F. o. basilicum. The rapid spread of this disease in the United States is likely caused by dissemination of infested seeds.

Keyword(s): Fusarium wilt, heterokaryosis