MADISON, WISCONSIN
University of Wisconsin-Madison

Corngrass (Cg) increases susceptibility to common rust and European corn borer
--B. G. Abedon and W. F. Tracy

Cg, when fully expressed, greatly alters the phenotype of the plant, often making plants carrying the allele unrecognizable as corn. Over the years we have observed that Cg increases susceptibility to many diseases and pests. To test this observation we performed two trials. In trial 1 we evaluated the effects of Cg on susceptibility to common rust (Puccinia sorghi). Seed of five inbreds segregating for Cg were planted in three replications. Plants were inoculated with spores of common rust and later evaluated for per cent leaf area destroyed by common rust. Averaged over all reps and inbreds the Cg plants had significantly more rust damage (51%) than did their normal counterparts (21%). The difference was consistent over all inbreds but the magnitude of difference was greatest in the more susceptible inbreds. We also did a feeding study with second instar European corn borers (Ostrinia nubilalis) in which the insects were offered a choice of Cg leaf tissue vs. normal leaf tissue. The data are not fully analyzed, however when averaged over reps and inbreds Cg leaf tissue was consumed more rapidly than the normal tissue. Thus in addition to its many effects on plant development, Cg affects host-parasite interactions for both insects and fungi. 


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