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The Effects of Nuclear Restorer Genes of Texas Male-Sterile Cytoplasm on Host Response to Helminthosporium maydis Race T. L. S. Watrud, Research Associate, Department of Agronomy, University of Illinois, Urbana 61801; A. L. Hooker(2), and D. E. Koeppe(3). (2)Professor, Department of Plant Pathology, University of Illinois, Urbana 61801; (3)Associate Professor, Department of Agronomy, University of Illinois, Urbana 61801. Phytopathology 65:178-182. Accepted for publication 26 August 1974. DOI: 10.1094/Phyto-65-178.

The effects of the dominant nuclear restorer factors Rf1 and Rf2, which restore fertility to corn (Zea mays) with Texas male-sterile (Tms) cytoplasm, upon host response to Helminthosporium maydis (Cochliobolus heterostrophus) race T toxin(s) were determined. The effects of H. maydis toxin on isolated mitochondria, excised leaves, and seedling roots, were compared for several isogenic lines containing normal (N), Tms, and fertility-restored Texas male-sterile (TRf) cytoplasms. The effects of the toxin on TRf plants were intermediate to those on N and Tms plants. Toxin effects on isolated mitochondria were compared with field susceptibility data for the N, Tms, and TRf versions of the isogenic lines B37, A632, and C103D. A greater toxin effect was seen on mitochondria from B37 and A632 Tms cytoplasms, than on those isolated from their respective TRf shoots. The C103D data were the inverse, which correlated with field observations. The results suggest that the restoration of pollen fertility modifies the intensity of the toxin effect on leaves, roots, or isolated mitochondria.

Additional keywords: southern corn leaf blight, nucleo-cytoplasmic interactions, cytoplasmic inheritance.