Vegetative compatibility groups among nonpathogenic root-colonizing strains of Fusarium oxysporum

Abstract

A total of 110 isolates of Fusarium oxysporum were collected from apparently healthy celery roots from the major celery production areas of California. All isolates used in this study were nonpathogenic on celery. Nitrate-nonutilizing mutants (nit mutants) were used to test for vegetative compatibility among the isolates. Twenty-eight isolates were randomly selected from the collection and used as tester isolates. Complementary nit mutants, arbitrarily designated nitA and nitB, were recovered from each of the 28 tester isolates and paired in all combinations to test for vegetative compatibility among the isolates. Fourteen distinct vegetative compatibility groups, designated VCG2001 through VCG2014, were recovered. The remaining 82 isolates were then tested for vegetative compatibility with these 14 vegetative compatibility groups. Fifty of the 110 isolates belong to one of the 14 vegetative compatibility groups. Two vegetative compatibility groups, VCG2001 and VCG2002, were found in the highest frequency and from the most fields. The data suggest that some vegetative compatibility groups found colonizing celery roots may be much more common than others. Vegetative compatibility may be a way to identify and characterize strains of nonpathogenic F. oxysporum.