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 early‐maturing 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.

Genetic analysis of tropical quality protein maize (Zea mays L.) germplasm

“…The QPM inbred lines used in this study were developed from conversion of a variety of mid-altitude normal endosperm inbred lines and OPVs to QPM and this explained the observed large genetic variability for various traits. This result is consistent with reports of genetic variability in tropical and temperate QPM germplasm (Spaner et al 1992;Vasal et al 1993a;Pixley and Bjarnason 1993;Bhatnagar et al 2004;Musila et al 2010;BaduApraku and Lum 2010;Badu-Apraku et al 2016) and in opaque-2 types (Motto et al 1978;Wessel-Beaver et al 1985).…”

Heterotic Patterns of IITA and CIMMYT Early‐Maturing Yellow Maize Inbreds under Contrasting Environments

“…In contrast, Badu-Apraku et al (2015a) found SNP marker-based GD method as the most effective in classifying early yellow quality protein maize (QPM) inbreds into heterotic groups under multiple stress environments. In another study involving the grouping of early white QPM inbreds under similar multiple stress environments, using the SNPbased GD, SCA effects of grain yield, HSGCA, and HGCAMT, the SNP-based GD method was identified as the most efficient in classifying the QPM inbreds into heterotic groups (Badu-Apraku et al, 2015c). The implication of the results of these studies is that the efficiency of the heterotic grouping methods, varies with the type of genetic material being studied.…”

Breeding for Quality Protein Maize (QPM) Varieties: A Review

“…In some cases, the traits recorded were conditioned mainly by additive gene effects under stress conditions (drought, low soil nitrogen, heat stress, combined drought and heat stress, Striga) and non-stress environments [20,21,23,[26][27][28]49]. Evaluation of yellow QPM genotypes under combined drought and heat stresses showed that grain yield was influenced by non-additive gene effects in South Africa [27].…”

“…[20] QPM hybrids Drought, low soil N, and Striga infested environments in Nigeria SCA effects were higher than GCA indicated the action of nonadditive genes. [21] Inbred lines and single cross hybrids…”

“…constraints. To alleviate some of these constraints, several studies have been done around the world on breeding for the resistance of QPM to pests and diseases [14,16,20,21] and tolerance to abiotic stresses such as drought, low soil nitrogen, heat stress and, combined heat and drought stress [9,14,[21][22][23][24][25][26][27][28].…”