GENOTYPE × ENVIRONMENT INTERACTIONS FOR EAR MOLD RESISTANCE AND ITS SUBCOMPONENTS IN MAIZE HYBRIDS

Abstract

Twelve short season maize (Zea mays L.) hybrids were evaluated over five environments between 1979 and 1982 to determine the magnitude of the genotype × environment interaction for ear mold (Gibberella zeae (Schwabe)) resistance. Mold damage (MD) was characterized into two subcomponents, percent infected plants (%IP) and spread of infection on infected ears (SI). All three traits (%MD, %IP and SI) exhibited highly significant genotype × environment interactions. Weather variables were considered to account for an insignificant proportion of this variation due to the nature of the artificial inoculaton procedure. An undetermined proportion of the variation was likely attributable to differences in fungal isolates used over the years. Estimates of stability indicated that four of the 12 hybrids had relatively low mold damage and high stability over the five environments. Broad-sense heritabilities estimated over the five environments were 0.73, 0.84 and 0.54 for %MD, %IP and SI, respectively. Evaluation of mold damage in one environment gave estimated heritabilities of 0.35, 0.50 and 0.19 for the three traits, respectively. Low genotypic correlation between %IP and SI indicated that they are in fact substantially different traits which may be selected for independently. Percent infected plants was a more stable trait than percent mold damage per se when selection occurred in one environment and, depending on the relative proportions of additive and nonadditive gene action conditioning the two traits, %IP may be a more suitable selection criterion in a recurrent selection program than percent mold damage.Key words: Gibberella zea, initial infection, spread of infection, corn, maize, ear mold