The Genetics of Pathogenicity in Cochliobolus Heterostrophus

Abstract

The ability of toxin producing fungi to cause disease on plants is dependent, not only on their ability to produce a toxin, but also their fundamental ability to infect and grow within plant tissues. Our laboratory has taken a variety of approaches to understand both basic pathogenicity and toxin production in the maize pathogen Cochliobolus heterostrophus. Mutational analysis suggests that a layer of mucilaginous material around germ tubes and appressoria is essential for pathogenicity, but only after the fungus enters the plant; the layer is not needed for adhesion. QTL analysis of T-toxin production indicates that regions of the genome unlinked to Toxl influence T-toxin biosynthesis, degradation, and/or secretion. QTL analysis also has revealed a difference in growth rate associated with alternate alleles at Toxl This difference may have contributed to the decline in race T after the 1970 Southern Corn Leaf Blight epidemic.