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Epidemiology and Ecology

Vegetative Compatibility Groups of Fusarium proliferatum from Asparagus and Comparisons of Virulence, Growth Rates, and Colonization of Asparagus Residues Among Groups. Wade H. Elmer, Assistant plant pathologist, Department of Plant Pathology and Ecology, The Connecticut Agricultural Experiment Station, Box 1106, New Haven, 06504; Phytopathology 81:852-857. Accepted for publication 4 February 1991. Copyright 1991 The American Phytopathological Society. DOI: 10.1094/Phyto-81-852.

Nitrogen metabolism mutants were selected from 110 isolates of Fusarium proliferatum isolated from four asparagus plantings during 1985 and 19871989. These nitrogen metabolism mutants were used in complementation tests for vegetative compatibility. Twenty vegetative compatibility groups (VCGs) were identified, but most (88) isolates fell into six VCGs that were found at more than one location. Isolates in the three most common VCGs (VCGs 5, 7, and 8) contained 39, 15, and 10% of the isolates, respectively, and were found at all locations. VCGs 13, 1, and 4 were found less frequently and comprised 5, 4, and 4% of isolates, respectively. Isolates from the six VCGs were compared for virulence on asparagus, for rates of radial growth on a minimal medium at 7, 12, 17, and 22 C, and for the rate that they colonized asparagus residues at 10 C and at 20 C. VCG was not correlated with virulence, or with radial growth rates at any temperature. Isolates in VCG 5 colonized asparagus residues at a higher rate than isolates in other VCGs, which may contribute to their frequent recovery in asparagus fields. More variation was found among VCGs in their rates of colonizing asparagus residues than within a VCG, which may indicate that these VCGs are genetically isolated and asexually propagated. There was no strong correlation between VCG and field. The frequent recovery of VCGs 5, 7, and 8 in many different plantings suggests that these VCGs are selectively maintained within and among asparagus fields.

Additional keywords: Asparagus officinalis, Fusarium crown and root rot, heterokaryosis.