Genetic Control and Distorted Segregation of T-Toxin Production in Field Isolates ofCochliobolus heterostrophus

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Abstract
T-toxin is a family of linear polyketols responsible for the high specific virulence of race T of Cochliobolus heterostrophus on cms-T maize. To date, a single locus, Tox1, has been shown to be involved in T-toxin synthesis. In an attempt to find additional loci, 12 race T (Tox+) and 11 race O (Tox-) field isolates were examined. Crosses to genetically defined strains demonstrated that all the race T isolates had the TOX1 allele and that all the race O isolates had the alternate allele, tox1. There was no evidence that these isolates differed at any other loci controlling T-toxin production. Five of the race O isolates carried a factor that caused distorted segregation at Tox1.