Genetic analysis and genotype x environment interaction for resistance to northern leaf blight disease in tropical maize (Zea mays L.) genotypes

Akinlolu O Ohunakin


Northern leaf blight (NLB) disease one of the most devastating foliar diseases of maize accounting for more than 50% yield losses annually. Information on inheritance of NLB resistance of maize population adaptable to tropical environments is required. Thus, hybrids generated through 10 x 10 half-diallel of tropical maize inbred lines were evaluated in five environments to determine their combining ability, impact of NLB disease on grain yield, and genotype x environment (G x E). The 45 single cross F1 hybrids and nine hybrid checks were evaluated across five environments using 9 x 6 alpha lattice with three replications. The greater proportion of general combining ability (GCA) over specific combining ability (SCA) effects across environments implies that additive gene action influences the inheritance of these traits. Predominance of additive gene indicates that rapid progress would be achieved from selection for NLB disease resistance. Regression analysis revealed 1030–1130 kg ha-1 reduction in maize grain yield per increase in NLB severity score. Significant negative relationships (r = -0.33 to -0.77) were reported between grain yield and NLB severity scores in this study. This showed the potential of NLB to cause yield reduction in susceptible genotypes. GGE revealed that the test environments fell into two sectors, indicating the existence of two mega-environments and presence of significant crossover interaction.