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Resistance

Inheritance of Resistance to Anthracnose Stalk Rot of Corn. J. Toman, Jr.,, Graduate research assistant, Department of Plant Pathology, University of Illinois, Urbana 61801; D. G. White, associate professor, Department of Plant Pathology, University of Illinois, Urbana 61801. Phytopathology 83:981-986. Accepted for publication 18 May 1993. Copyright 1993 The American Phytopathological Society. DOI: 10.1094/Phyto-83-981.

Inheritance of resistance to anthracnose stalk rot of corn (Zea mays), caused by Colletotrichum graminicola, was studied in progeny derived from a cross between the resistant inbred DW 1035 [(MP305 × FRB73^[5]_S8] and the susceptible inbred FRB73. In 1987, 1988, and 1989, the parental lines and the F₁, F₂, and both backcross generations were tested. Generation mean analysis indicated significant additive and dominance genetic effects were of primary importance in all 3 yr. Dominance estimates ranged from 8.3 to 33.9%. Estimates of the number of effective factors conditioning resistance ranged from 0.38 to 2.08. Significant dominance genetic effects from generation mean analysis, low estimates of the number of effective factors, and frequency distributions of individual plant reactions indicate genetic dominance controlled by one or a few genes. To further evaluate the inheritance, individual stalk rot reactions within a particular generation were classified as resistant or susceptible by discriminant analysis. Expected stalk rot reaction distributions were then determined by means of a partitioning method. The observed distributions were compared for goodness of fit to the expected distributions using a chi-square test. The data could best be explained by a single, dominant gene difference between DW1035 and FRB73 for anthracnose stalk rot resistance in some generations. The use of discriminant analysis to identify resistant and susceptible plants, followed by partitioning, is a method that can be extremely useful with data where genetically resistant and susceptible plants may not be correctly identified by the phenotypic reaction.