Phytotoxins from the pathogenic fungi <i>Drechslera maydis</i> and <i>Drechslera sorghicola</i>

Abstract

Drechslera maydis, the causal agent of Southern corn leaf blight, and Drechslera sorghicola, the causal agent of leaf spot on Johnson grass, produce a series of phytotoxic sesterterpenoids. These sesterterpenoids belong to the ophiobolin family. One of them, ophiobolin I, was characterized by x-ray diffraction and served as a crucial reference compound for characterizing four other ophiobolins. All of the ophiobolins studied produce characteristic lesions on host plants at concentrations of 1 mM to 1 muM. The ophiobolin characterized as 6-epiophiobolin A is selectively toxic to corn bearing Texas-male-sterile (Tms) cytoplasm when assayed in a dark CO(2) fixation assay. It is plausible that these ophiobolins had a role in the 1970 corn-blight epidemic in North America.