Vitamin A deficiency (VAD) is a serious problem in sub-Saharan Africa (SSA) and other parts of the world. Understanding the effect of marker-based improvement (MARS) of two maize synthetics (HGA and HGB) representing different heterotic groups on their agronomic performance, carotenoid content, and combining abilities could help identify suitable sources to develop divergent inbred lines for optimizing heterosis. This study involved three selection cycles each of the two synthetics and their nine varietal-cross hybrids together with a released check variety was conducted across four diverse locations in Nigeria in 2018 and 2019. Environment and hybrid effects were significant on grain yield and other agronomic traits as well as provitamin A content and other carotenoids. Genetic improvement per cycle of MARS in the parental synthetics was 15% for provitamin A, 25% for β-carotene and 26% for lutein in HGA and 4% for grain yield, 3% for zeaxanthin and 5% for α-carotene in HGB. Grain yield and agronomic traits of the two maize synthetics were controlled by additive and non-additive gene effects, while provitamin A content and other carotenoids were mainly controlled by additive gene effects. Some selection cycles which were high in grain yield and provitamin A content were identified as potential sources of new and divergent maize inbred lines in maize breeding programs. Some varietal-cross hybrids expressed significant mid-parent heterosis for grain yield and moderate mid-parent heterosis for provitamin A, β-carotene and xanthophylls. These hybrids could be commercialized at reasonable prices to small-scale farmers in rural areas that are most affected by vitamin A deficiency.

Bambara groundnut is a reliable source of carbohydrates and protein in rainforest agroecology, but limited research had been done and few varieties commercialised. The magnitude of phenotypic variability, character association, and contribution of characters to seed yield were investigated among 50 accessions received from IITA, Nigeria. Field evaluation took place during the 2017 – 18 cropping seasons. The accessions were allocated to experimental plots using a Randomised Complete Block Design with three replicates. Data were collected on phenological, agronomic, and seed yield characters. The main effect showed significant (p ≤ 0.05) differences for phenological, vegetative, and reproductive characters. The year effect influenced agronomic and seed yield characters while accessions by year interaction were insignificant for all characters. The stepwise discriminant analysis identified three redundant characters. The leaflet length and width, canopy spread, leaf/plant, seeds/plant, and seed weight showed high discriminatory ability and are efficient for morphological characterisation and conservation. Hybridisation between accessions dispersed in quadrants 1, 2, and 4 may evolve early and medium maturity types with improved seed yield and biomass. The number of seeds/plant and pods/plant are indices for seed yield. The contribution of pods/plant to seed yield was masked by canopy spread, peduncle length, and pod width indicating competition for photo-assimilates. TVSu 17, TVSu 277, TVSu 271, and TVSu 278 are donor parents for earliness. TVSu 261 performed best for seed yield and yield component characters. Hybridisation among TVSu 261, TVSu 587, TVSu 275, and TVSu 17 will evolve medium maturing and high seed-yielding varieties for further evaluation.

Maize is a major staple food in Sub-Saharan Africa (SSA). Vitamin A deficiency index is high in Africa and could be reduced through the consumption of provitamin-A-enriched maize. However, foliar diseases such as maize streak virus, northern corn leaf blight and common rust constrain maize production in SSA. The cultivation of host-resistant varieties is the most effective approach to mitigate their effects. Therefore, maize synthetics improved for PVA carotenoids, their selection cycles and crosses as well as a commercial disease-resistant check were assessed for resistance to maize streak virus, northern corn leaf blight and common rust at hotspots in Nigeria. The foliar diseases’ effects on the agronomic performance and carotenoid content of the maize genotypes were assessed. The Genotypes differed for most agronomic traits and foliar disease resistance. Stepwise regression revealed that, although the agronomic traits determined 93% of the grain yield, each foliar disease had effect on the yield. A unit increase in maize streak virus score increased plant aspect and husk cover scores by 0.6 and 0.4, respectively, whereas an increase in common rust score decreased plant height by 16.2 cm and increased plant aspect score by 0.7. Maize streak virus and common rust decreased genotypic variability for lutein by 36.7 and 18.7%, respectively, while northern corn leaf blight decreased genotypic variability for provitamin A by 27.1%. Most of the genotypes exhibited moderate susceptibility to northern corn leaf blight. However, three selection cycles and three crosses exhibited high tolerance to maize streak virus and moderate tolerance to common rust, thus can serve as sources of PVA-enriched, maize streak virus and common rust tolerant lines.