Effect of the nuclear genome of corn on sensitivity to helminthosporium maydis race t toxin and on susceptibility to helminthosporium maydis race t
Payne, G.A.; Yoder, O.C.
Phytopathology 68(3): 331-338
Differences in susceptibility of corn genotypes (containing Texas male-sterile cytoplasm) to H. maydis (Nisikado and Miyake) race T and in sensitivity to H. maydis race T-toxin were determined using quantitative bioassays. Evaluation of a wide range of genotypes indicated that both the level of susceptibility of corn to the fungus and the degree of sensitivity to the toxin were influenced by the nuclear genome. However, differences in susceptibility to the fungus were not correlated with differences in sensitivity to the toxin. Nuclear genes that influence cytoplasmic sensitivity to the toxin appear to play no role in disease development, whereas cytoplasmic sensitivity to toxin causes increased susceptibility to H. maydis race T. These observations, and those of previous studies on the genetics of H. maydis, support the hypothesis that this toxin is not required for the establishment of a compatible host-parasite relationship but that it does contribute to the virulence of H. maydis race T on corn containing Texas male-sterile cytoplasm. This role in disease differs from those described for host-specific toxins produced by several other fungal plant pathogens.