Gene action and reciprocal effects for ear rot resistance in crosses derived from five tropical maize populations

Devastating maize grain yield and quality losses are caused by Aspergillus flavus, Fusarium verticillioides and Stenocarpella maydis ear rots especially in tropical countries. Therefore, combining ability of tropical maize populations for ear rot severity and ear rot-related traits was investigated. Ten full-sib progenies, comprising one resistant and one susceptible from each of the five populations, were selected for mating in a 10 × 10 full diallel. The full-sib progeny crosses were evaluated across two environments with two replications in Zambia. To determine resistance across three ear rots that occur together in Zambia, the crosses were artificially inoculated with a mixture of Aspergillus flavus, Fusarium verticillioides and Stenocarpella maydis isolates. There were marked differences between environment main effects and their interaction with GCA and SCA effects were highly significant, suggesting observation of genotype × environment interaction effects. Both additive and non-additive gene effects were significant for ear rot severity. Highly significant reciprocal differences were also revealed, suggesting that cytoplasmic gene effects and their interaction with nuclear genes were responsible in modifying resistance across the three ear rot diseases in the full-sib progenies that were derived from the five tropical maize populations.