Classification of races by DNA polymorphism analysis and vegetative compatibility grouping in Fusarium oxysporum f.sp. pisi

Abstract

The race structure of a collection of Fusarium oxysporum f.sp. pisi isolates from the U.K. and the U.S.A. was investigated. Isolates were assigned to races 1,2,5 or 6 by pathogenicity tests on a series of host differentials. The relationships between isolates within each race and between races was then examined by restriction fragment length polymorphism analysis and vegetative compatibility grouping. For the restriction fragment length polymorphism analysis three clones, containing DNA from Race 1, were constructed and used as probes; pDG102 and pDG106 contained moderately repetitive DNA and pDG312 contained a ribosomal DNA repeat. Vegetative compatibility was studied by complementation tests of chlorate resistant mutants. Both restriction fragment length polymorphism analysis and vegetative compatibility grouping were able to distinguish the four races and revealed that Race 2 comprised two separate groups, termed 2A and 2B. The evolutionary implications of the findings are discussed.