Diallel Analysis of Resistance to Fusarium Ear Rot and Fumonisin Contamination in Maize

The fungus Fusarium verticillioides infects maize (Zea mays L.) ears and kernels, resulting in Fusarium ear rot disease, reduced grain yields, and contamination of grain with the mycotoxin fumonisin. Hybrid maize breeding programs involve selection for both inbred and hybrid performance; the emphasis placed on inbred versus hybrid selection depends on heritability of and the genetic correlation between resistance in the different generations. The objectives of this study were to assess the importance of general combing ability (GCA) and specific combining ability (SCA) for resistance to Fusarium ear rot and fumonisin contamination and to estimate the correlation between resistance measured in inbred and hybrid generations. We evaluated a diallel mating of 18 inbred lines from different heterotic groups with different levels of resistance. Hybrids had 27% less ear rot and 30% less fumonisin content than their inbred parents, demonstrating the importance of hybrid vigor to disease resistance. Both GCA and SCA were significant for yield and disease resistance, and inbred performance per se and corresponding GCA in hybrids were significantly correlated (r >= 0.78). Genetic variation for resistance was greater in inbred lines than among hybrids, however. These results suggest that the most efficient way to improve Fusarium ear rot and fumonisin contamination resistances in hybrids is to evaluate and select among inbred lines before using resources to create and evaluate hybrids.