A single gene encodes a selective toxin causal to the development of tan spot of wheat.

The identification and characterization of pathogenicity factors are essential to an understanding of the molecular events that regulate the interaction of plant-pathogenic microbes with their hosts. We have isolated the gene that encodes a host-selective toxic protein produced by the fungus Pyrenophora tritici-repentis and confirmed that this gene functions in the plant as the primary determinant of pathogenicity in the Pyrenophora-wheat interaction. These results demonstrate that a single gene encodes the production of a host-selective toxin and that transformation of this gene into a non-toxin-producing isolate of P. tritici-repentis leads to both toxin production and pathogenicity.