This proposal is directed at evaluating whether a victorin-binding protein (VBP) isolated from oat is the receptor for this toxin and is the molecular determinant of susceptibility to the disease Victoria bight. Using purified VBP, antibody thereto, and a full length cDNA already cloned, the functional role of VBP will be examined in biochemical aspects, the binding domains examined, sequence of VBP-cDNA determined, a determination of segregation of the gene encoding VBP studied, and sequence heterogeneity in VBP of resistant and susceptible phenotypes compared. This work is directed at a critical issue in modern plant pathology, namely an understanding of the site and function of a plant gene product which regulated the pathogenicity of a fungal pathogen that causes the disease, Victoria bight, of oat.