GENETICS OF PHYTOPATHOGENIC FUNGI: VI. HETEROCARYONS INVOLVING GIBBERELLA FUJIKUROI AND FORMAE OF FUSARIUM OXYSPORUM

Abstract

Heterocaryons involving nutritionally deficient mutant strains of Gibberella fujikuroi and mutant strains of this species and of four formae of Fusarium oxysporum were obtained. It was not possible to get heterocaryons of G. fujikuroi and F. oxysporum f. pisi until the latter mutant strain was adapted to grow on minimal medium. Spores from heterocaryons had either the genotype of only one component strain or of either component strain, depending on the heterocaryon. It was possible to alter nuclear ratios by growing certain heterocaryons on minimal medium supplemented with the compound(s) required by one or the other component strain. Sectors from certain heterocaryons grown on potato dextrose agar were homocaryotic for the nutritional requirement(s) of one component strain. Heterocaryosis as a taxonomic tool and the difficulties involved in demonstrating the parasexual cycle in the genus Fusarium are discussed.