INHERITANCE OF RESISTANCE TO ANTHRACNOSE STALK ROT OF CORN

Inheritance of resistance to anthracnose stalk rot of corn (Zea mays), caused by Colletotrichum graminicola, was studied in progeny derived from across between the resistant inbred DW1035[(MP305 X FRB73[5])S8] and the susceptible inbred FRB73. In 1987, 1988, and 1989, the parenta l lines and the F1, F2, and both backcross generations were tested. Ge neration mean analysis indicated significant additive and dominance ge netic effects were of primary importance in all 3 yr. Dominance estima tes ranged from 8.3 to 33.9%. Estimates of the number of effective fac tors conditioning resistance ranged from 0.38 to 2.08. Significant dom inance genetic effects from generation mean analysis, low estimates of the number of effective factors, and frequency distributions of indiv idual 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 ex pected distributions using a chi-square test. The data could best be e xplained by a single, dominant gene difference between DW1035 and FRB7 3 for anthracnose stalk rot resistance in some generations. The use of discriminant analysis to identify resistant and susceptible plants, f ollowed by partitioning, is a method that can be extremely useful with data where genetically resistant and susceptible plants may not be co rrectly identified by the phenotypic reaction.