Vegetative Compatibility Grouping of Formae Speciales of Fusarium oxysporum Pathogenic to the Liliaceae

Abstract

Vegetative compatibility groups (VCGs) within seventy-five isolates of Fusarium oxysporum pathogenic to the Liliaceae, i.e. ff. sp. garlic, lilii, asparagi, cepae, allii and tulipae, were determined. The nitrate non-utilizing mutants (nit mutants) were recovered from F. oxysporum isolates cultured on minimal agar amended with 1.5% potassium chlorate. Nit mutants were assigned to one of three phenotypic classes (nit1, nit3, nitM) by their ability to utilize various nitrogen sources. Vegetative compatibility between isolates was demonstrated with heterokaryon formation between complementary nit mutants. Fiftyeight isolates of F. oxysporum f. sp. garlic were placed into 3 VCGs. Five isolates of F. oxysporum f. sp. asparagi were placed into 2 VCGs and 12 isolates of F. oxysporum ff. sp. lilii, cepae, allii and tulipae belonged to a VCG each of formae speciales. Vegetative compatibility was not detected among isolates from different formae speciales of F. oxysporum tested.