Gene action and heterotic groups of early white quality protein maize inbreds under multiple stress environments

Abstract

Food insecurity and malnutrition are major challenges facing rural populations in sub-Saharan Africa. A total of 150 quality protein maize (Zea mays L.) (QPM) hybrids generated from 30 earlymaturing QPM inbreds plus six checks were evaluated under drought, low soil N, and Striga [Striga hermonthica (Delile) Benth.]-infested environments in Nigeria for 2 yr. The objectives were to (i) examine the gene action conditioning the traits in the inbreds, (ii) classify them into heterotic groups using two methods, (iii) identify the best QPM inbred testers across environments, and (iv) identify stable and high-yielding hybrids. General and specific combining ability (GCA and SCA, respectively) mean squares were significant (P < 0.01) for grain yield and other traits across environments, indicating that additive and nonadditive gene actions were important in the inheritance of most traits of the inbreds. Preponderance of SCA sum of squares over GCA for most measured traits across environments indicated that nonadditive gene action largely modulated inbred trait inheritance. The GCA effects of multiple traits (HGCAMT) method classified the inbreds into three heterotic groups each under drought and across environments and four groups under low N and Striga-infested environments. Single nucleotide polymorphism (SNP)-based method placed the inbreds into three groups across environments and was more efficient. TZEQI 6 and TZEQI 55 were identified as testers across environments. TZEQI 44 × TZEQI 4, TZEQI 35 × TZEQI 39, TZEQI 35 × TZEQI 59, TZEQI 6 × TZEQI 35, and TZEQI 45 × TZEQI 33 were the most stable and highest- yielding hybrids across environments and should be commercialized for improved nutrition and food security in sub-Saharan Africa.