Striga hermonthica (Del.) Benth parasitism, low soil N, and nutritional deficiencies of normal-endosperm maize (Zea mays L.) threaten maize yield and exacerbate nutritional problems in sub-Sahara Africa (SSA). This study was conducted (a) to evaluate genetic variation among extra-early maturing maize hybrids with provitamin A and quality protein characteristics, (b) to investigate gene action governing the inheritance of Striga resistance, grain yield, low N tolerance, and other measured traits under low-N, high-N, and Striga-infested environments, and (c) to identify hybrids with high yield and stability across environments. One hundred and fifty hybrids developed using North Carolina Design II were evaluated with six checks under low-N, high-N, and Striga-infested environments in Nigeria. Mean squares for hybrids were highly significant (P < .01) for grain yield and other traits across environments. Only general combining ability (GCA) for female and/or male mean squares were significant for measured traits under low N. In addition to significant GCA effects for most traits, specific combining ability was significant (P < .05) for Striga emergence count under Striga infestation, and ear height and ears per plant under high N, indicating that additive and nonadditive genetic effects controlled the inheritance of few traits under Striga and high N, whereas additive genetic effect governed the inheritance of the traits under low N. Hybrids TZEEIORQ 55 × TZEEIORQ 26, TZEEIORQ 49 × TZEEIORQ 75, and TZEEIORQ 52 × TZEEIORQ 43 were high yielding and stable across environments and have potential for improving nutrition and maize yields in SSA. Abbreviations: AEA, average environment axis; ASI, anthesis-silking interval; ATC, average tester coordinate; DA, days to 50% anthesis; DS, days to 50% silking; EASP, ear aspect; EHT, ear height; EPP, ears per plant; ESP1, Striga emergence count at 8 wk after planting; ESP2, Striga emergence count at 10 wk after planting; GCA, general combining ability; GCA f , general combining ability for female effect; GCA m , general combining ability for male effect; GGE, genotype main effect plus genotype x environment interaction;

A hemiparasitic plant, Striga hermonthica (Del.) Benth and soil nitrogen stress are the key constraints to maize (Zea mays L.) productivity in sub-Saharan Africa, where commonly cultivated maize is the normal endosperm type that is deficient in provitamin A, tryptophan and lysine (PVATL). Seventy-six extra-early maize inbreds with provitamin A, tryptophan, and lysine qualities (TZEEIORQ) were developed to address these constraints, and four checks were assessed under Striga, low and high nitrogen conditions at three locations in Nigeria. The inbreds were further genotyped with two beta-carotene hydroxylase 1 (crtRB1) markers, and their seeds were quantified for provitamin A content. Significant (P < 0.01) genetic variations were observed for grain yield and other agronomic attributes of the inbreds under varying environmental conditions. Levels of PVATL for the inbreds ranged from 2.21–10.95 µg g−1, 0.04–0.08%, and 0.19–0.39%, respectively. Beta-carotene marker, crtRB1-3′TE, was polymorphic and grouped the inbreds into two. The marker was effective in identifying inbreds with moderate provitamin A content. Inbreds TZEEIORQ 5, TZEEIORQ 52, and TZEEIORQ 55 exhibited resistance to Striga, tolerance to nitrogen stress with moderate levels of PVATL and could be invaluable sources of favorable alleles for breeding nutritionally improved maize varieties with resistance/tolerance to Striga and soil nitrogen stress.

Maize (Zea mays L.) is a staple food for millions of people across the globe, and it supplies more than 30% of total dietary calories. However, the normal endosperm lacks a sufficient quantity of the nutritive precursor of vitamin A. To achieve food security and avert malnutrition, there is a need to adopt the cultivation of the early multiple stress-tolerant pro-vitamin A maize hybrid. The objective of this study was to assess the agronomic performance and yield of the newly developed maize hybrids. Fifteen improved maize hybrids and one commercial hybrid used as a local check were evaluated in a randomized complete block design with two replications for two years at the Ladoke Akintola University of Technology Teaching and Research farm in Ogbomoso, Nigeria. Hybrids exhibited significant variation (P < 0.01) for grain yield, number of days to anthesis and silking, ear height and husk cover. Across the years, the grain yield of hybrids ranged between 4,780.8 kg ha?1 (PVAEH-19) and 7,886.9 kg ha?1 (PVAQEH-1), with a mean of 6,354.2 kg ha?1. PVAEH-15 ranks the best on the basis of superiority in grain yield, early flowering and tight husk cover. Fourteen hybrids out-yielded the local check (4,947.2 kg ha-1), and five hybrids had a significant (P < 0.05) yield advantage of > 26% over the local check. The consistent performance of PVAEH-15 and PVAEH-16 in the two years of evaluation indicates potential for the adaptability of the hybrids to the agro-ecology. Farmers? adoption of these maize hybrids will boost maize production and prevent malnutrition in the derived savanna agro-ecology of Nigeria.