A Molecular Strategy for Isolation of the TOXl Allele from Cochliobolus Heterostrophus

Abstract

The fungal maize pathogen Cochliobolus heterostrophus (anamorph: Helminthosporium maydis) exists as two pathotypes: race T, which produces T-toxin and race O, which does not. All race T isolates are highly virulent on maize with Texas male sterile cytoplasm; race O isolates are weakly virulent. On maize lines lacking T-cytoplasm, the virulence of races T and O is comparable. Crosses between isolates of races T and O have demonstrated that T-toxin production is determined by a single locus, Tox1. TOX1 progeny produce T-toxin and are highly virulent on T-cytoplasm maize; tox1 progeny do not produce T-toxin and are weakly virulent. Dominance of the TOX1 allele has been established by hetero-karyon analysis (Leach et al, 1982).