Inheritance and genotype by environment analyses of resistance to Fusarium verticillioides and fumonisin contamination in maize F1 hybrids

Fusarium ear rot (FER) and fumonisin accumulation in maize, caused by Fusarium verticillioides, can lead to lower grain quality, crop yield reduction and mycotoxicosis of humans and livestock. The best approach to control this fungus is through the development of resistant maize varieties, however, no immune cultivars are available with commercial cultivars ranging from susceptible to moderately resistant. Therefore, this study evaluated F-1 maize hybrids, generated from inbred lines resistant to FER/fumonisins and Aspergillus flavus/aflatoxins, for improved resistance to F. verticillioides infection and fumonisin contamination. Diallel analysis was performed to understand the inheritance of resistance to F. verticillioides/fumonisins. Consequently, maize inbred lines resistant to F. verticillioides/fumonisins under South African conditions and lines resistant to Aspergillus flavus under Kenyan conditions were crossed to produce 18 hybrids. Hybrids and parental lines were planted in replicated field trials at three localities in South Africa. Artificially inoculated trials were conducted with disease severity, F. verticillioides target DNA and total fumonisin concentrations determined by visual assessment, quantitative PCR and liquid chromatography tandem mass spectrometry, respectively. Hybrids R119W x CKL05015, CML 495 x CKL05015 and CKL05015 x R119W were the most resistant to FER severity, F. verticillioides colonisation and fumonisin contamination, respectively. The resistance levels of hybrids did not differ significantly from their parental inbred lines, except for specific hybrids in certain test environments. General combining ability and specific combining ability were significant (P ae 0.05) for all three parameters evaluated. Kenyan inbred lines CKL05015 and CML 495 were good general combiners for resistance to fumonisin contamination. Specific combinability estimates showed that CKL05015 x R119W was the best hybrid combination for resistance to FER severity, F. verticillioides colonisation and fumonisin contamination. Additive gene effects were predominant in the inheritance of resistance in this set of hybrids. Parental inbred line performance was indicative of F-1 hybrids performance. This study provided fundamental information on the maize lines evaluated that would be useful to breeders in the development of F. verticillioides/fumonisin-resistant cultivars.