Comprehensive diallel analysis of combining ability and heterosis to Fusarium verticillioides ear rot resistance in maize

Maize (Zea mays L.) Fusarium ear rot (FER), which is caused by the fungal pathogen Fusarium verticillioides, is a major ear disease affecting maize production in China. Developing resistant maize hybrids is a cost-effective and environmentally friendly method of reducing yield losses due to FER. Using the nail punch inoculation method, 17 highly resistant and 16 highly susceptible inbred lines were identified in this study, and a large-scale maize hybrid consisting of 528 F-1's was produced using a half-diallel cross model. The hybrids were inoculated with F. verticillioides in 6 year-location environment combinations during 2020-2022. Our results showed that estimates of genotypic, environmental, and genotype x environment interaction variance components were very significant (p < 0.001). All the crosses generated from highly resistant inbred lines exhibited high kernel resistance, whereas those generated from highly susceptible inbred lines mostly exhibited high susceptibility to FER. Crosses between resistant and susceptible inbred lines showed intermediate resistance to FER. The general combining ability (GCA) effect was greater than the specific combining ability effect across multiple environments, indicating that the inheritance of FER resistance was mainly influenced by additive genetic effects. The correlation coefficient between the expected GCA value and hybrid resistance was 0.789, whereas that between the mid-parent value and hybrid resistance was only 0.644. Inbred performance per se and their corresponding hybrids across multiple environments were significantly correlated (r = 0.823). However, no relationship was observed between the FER resistance of F-1's and that of their parental heterotic groups.