Grouping of early maturing quality protein maize inbreds based on SNP markers and combining ability under multiple environments

Abstract

a b s t r a c tFood insecurity and malnutrition are two major challenges facing rural populations in sub-Saharan Africa (SSA). Hybrids of quality protein maize (QPM) have a crucial role here to play because QPM contains increased lysine and tryptophan concentrations and has a higher biological value than the normal maize. Information on the combining ability and heterotic patterns of QPM inbreds is crucial for the success of hybrid programs in the sub-region. Ninety-one diallel crosses derived from 14 early maturing yellowendosperm QPM inbreds were evaluated from 2010 to 2012 under Striga infested, drought, low-N and optimal environments in Nigeria. The objectives were to (i) examine the combining ability of the set of early yellow QPM inbreds, (ii) classify the inbreds into heterotic groups and identify the best testers (iii) compare the efficiencies of the heterotic grouping methods in classifying the inbreds and (iv) determine the grain yield and stability of the inbreds in hybrid combinations under the research environments. General (GCA) and specific (SCA) combining ability effects were important in the inheritance of grain yield and other traits of the inbreds. However, GCA was more important than SCA under each contrasting environment and across environments suggesting that the additive gene action was more important than the non-additive in the set of inbreds. The SCA effects of grain yield and the heterotic group's SCA and GCA of grain yield (HSGCA) methods classified the inbreds into three groups each, while the heterotic grouping based on GCA of multiple traits (HGCAMT) and the SNP-based genetic distance (GD) methods had two groups each across research environments. There was close correspondence among the classifications of all the grouping methods in terms of placement of inbreds into the same heterotic groups. The SNP-based method was the most efficient and was used to identify TZEQI 87 and TZEQI 91 as the best testers for the SNP-based heterotic groups 1 and 2. The hybrids, TZEQI 87 × TZEQI 93, TZEQI 77 × TZEQI 91 and TZEQI 80 × TZEQI 91 were identified as the most stable and high yielding across research environments and should be commercialized.

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

“…These markers could, therefore, constitute the framework for marker assisted introgression of the op2 trait into maize genotypes [57]. Badu-Apraku et al [20] grouped inbred lines based on GCA of multiple traits and the SNP-based genetic distance methods and they found that the two methods identified two groups each across research environments with close correspondence among the classifications of all the grouping methods in terms of placement of inbreds into the same groups. Moreover, the SNP-based method was found to be most efficient in identifying TZEQI 87 and TZEQI 91 as the best testers for the SNP-based heterotic groups 1 and 2.…”

“…[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…”

“…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].…”

“…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].…”

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

“…Assessment of the new diversity can guide sound strategies for hybrid development and other uses of the germplasm. Molecular markers have been used to investigate genetic diversity and suggest heterotic groupings, hybrid testers, and possible hybrid combinations (Warburton et al 2002;Duarte et al 2004;Lu et al 2009;Wen et al 2011;Semagn et al 2012a;Wegary et al 2013;Akinwale et al 2014;Badu-Apraku et al 2015). Markers could thus be used to ascertain if an increase in diversity levels in mid-altitude maize germplasm can be measured following introduction of QPM germplasm from tropical breeding programs.…”