Low soil Nitrogen (low‐N) is one of the most important abiotic stressors responsible for significant yield losses in maize (Zea mays L.). The development and commercialization of low‐N–tolerant genotypes can contribute to improved food security in developing countries. However, selection for low‐N tolerance is difficult because it is a complex trait with strong interaction between genotypes and environments. Marker‐assisted breeding holds great promise for improving such complex traits more efficiently and in less time, but requires markers associated with the trait of interest. In this study, 150 BC2F1 families of CML 444 × CML 494 were evaluated at two locations for two consecutive seasons to identify SNP markers associated with quantitative trait loci (QTL) for yield and other agronomic traits under low‐ and high‐N environments. A total of 13 QTL were identified with 158 SNP markers, of which nine and four QTL were detected under low‐ and high‐N environments, respectively. Five QTL one each for grain yield (qgy‐1), days to silking (qdts‐1) and anthesis‐ silking interval (qasi‐6), and two for stay green characteristic (qsg‐1 and qsg‐4) were close to their adjacent markers, with an interval of 0.7 to 5.2 cM between them and explained phenotypic variance of 9 to 21%. These QTL would be invaluable for rapid introgression of genomic regions into maize populations using marker‐assisted selection (MAS) approaches. However, further validation of these QTL is needed before use in MAS.

Ideas 1. General combining ability (GCA) effects were superior over specific combining ability (SCA) effects indicating that additive genes largely controlled grain yield and other traits among the newly developed extra-early quality protein maize inbred lines under low nitrogen, Striga-infested and high nitrogen conditions. 2. Maternal genetic effects influenced plant height under Striga-infested condition which suggested that inbred lines that exhibited significant and positive GCA-female effects for plant height should not be used as female parents to avoid production of tall hybrids that are liable to lodging. 3. Genetic distances were significantly associated with grain yield under low nitrogen, Strigainfested and high nitrogen conditions which implied that inbred lines that had high pairwise genetic distances should be considered for hybrid production to maximize heterosis. This article is protected by copyright. All rights reserved. 2 4. TZEEQI 358 displayed significant and desirable GCA effects for grain yield and other important traits across low nitrogen, Striga-infested and high nitrogen conditions and could be a useful source of valuable alleles for population improvements. 5. TZEEIORQ 58 x TZEEQI 397 exhibited high grain yield and stability across the low nitrogen, Striga-infested and high nitrogen environments and could potentially address the food and nutritional insecurities prevailing in sub-Saharan Africa.

Vitamin A deficiency, drought, low soil nitrogen (low-N), and Striga hermonthica parasitism of maize (Zea mays L.) cause malnutrition and food insecurity in sub-Saharan Africa. The objectives of this study were to determine combining abilities of extra-early provitamin A (PVA) lines, classify them into heterotic groups (HGs), identify testers, and determine yield stability of hybrids under contrasting environments in two trials. In Trial 1, 190 F 1 hybrids plus six checks were tested under Strigainfested, drought, and stress-free environments in Nigeria from 2015-2017. In Trial 2, 35 extra-early yellow hybrids were evaluated under low-N, Striga-infested, and stress-free environments in 2018. TZEEIOR 202 and TZEEIOR 205 had PVA concentrations of 23.98 and 22.56 μg g −1 . TZEEIOR 197 × TZEEIOR 205 (20.1 μg g −1 ) and TZEEIOR 202 × TZEEIOR 205 (22.7 μg g −1 ) contained about double the PVA level of the commercial check, TZEEI 58 × TZEE-Y Pop STR C5 (11.4 μg g −1 ). Both general (GCA) and specific (SCA) combining ability variances were significant for most agronomic traits, although GCA was larger than SCA effects, indicating GCA effects primarily controlled the inheritance of those traits. TZEEIOR 97 and TZEEIOR 197

In spite of efforts by national and international scientists to improve crop productivity, varieties of crops grown in Africa have low productivity.