Agronomy

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Genetic analysis and yield assessment of maize hybrids under low and optimal nitrogen environments
(Elsevier Ltd., 2022) Amegbor, I. K.; Abe, A.; Adjebeng‑Danquah, J.; Adu, G. B.
Development of maize hybrids that possess tolerant genes to low soil nitrogen is critical for long-term maize production in areas with low soil fertility. In this study, estimates for combining ability effects for grain yield and secondary traits of selected inbred lines, identify potential parents for hybrid development and yield potential of the crosses under sub-optimal and optimal N environments. One hundred hybrids were evaluated under suboptimal and optimal N environments for two years. The experimental layout was a 10 X 10 alpha lattice design with two replications for two experiments. The results obtained showed that, the genotypes evaluated varied for grain yield and the characters measured under sub-optimal and optimal N conditions. Grain yield reduction due to N stress was 40.9%. General and specific combining ability (GCA) and (SCA) effects for mean squares varied for grain yield demonstrating the importance of additive and non-additive genetic effects for the hybrids evaluated under the study conditions. Even though significant variations were detected for GCA and SCA, GCA which is the additive gene action component mainly controlled the heritage of grain yield under both conditions. Inbred line 15 was identified as the superior parent with positive and significant GCA for grain yield under sub-optimal N. Genotypic correlation studies displayed that grain yield was positively correlated with ears per plant under sub-optimal N and was also positively associated with anthesis-silking interval under high N. The hybrids 52, 75, 81 and 37 were identified to be significantly superior in terms of grain yield, ASI and EPP under the two-contrasting conditions. The results suggest that, there is a need for development of low N tolerant inbred lines and hybrids for production under soils with low N status in the Guinea savanna of Ghana for high grain yield to be realised.
Agronomic performance and combining ability estimates of yellow maize inbred lines under adequate and deficit moisture conditions
(Springer, 2022) Amegbor, I. K.; Abe, A.; Adjebeng‑Danquah, J.; Adu, G. B.; Oteng‑Frimpong, R
Breeding for drought tolerance and increased grain yield is vital in mitigating the threat posed by recurrent drought stress on maize production, as well as tackling malnutrition with plant-based food products. The study was conducted to assess the combining ability of yellow maize lines and the performance of their single-cross hybrids under drought and rain-fed conditions. A total of 24 yellow maize inbred lines from CSIR-Savanna Agricultural Research Institute Maize Improvement Programme gene pool were selected and inter-mated using North Carolina II mating design to generate 96 single-cross hybrids. The 96 hybrids together with four advanced hybrids used as checks (a total of 100 hybrids) were evaluated under drought and rain-fed conditions for two years using a 10 × 10 lattice design with two replications. The hybrids differed significantly in their grain yield (GY) and agronomic performance under the growing conditions. In the present study, drought stress reduced GY by 50.3%. The general combining ability (GCA) and specific combining ability (SCA) for GY and its related traits were significant. Even though additive and non-additive gene actions controlled the inheritance of the traits, additive gene action was found to be more important than non-additive genetic effects. Hybrids 27, 81 and 68 on the other hand 89, 18 and 26 were identified as the outstanding genotypes under drought and rain-fed conditions, respectively. These hybrids should be extensively evaluated under varied conditions and commercialized to enhance food insecurity in sub-Saharan Africa.
Assessing effect of marker-based improvement of maize synthetics on agronomic performance, carotenoid content, combining ability and heterosis
(MDPI (Multidisciplinary Digital Publishing Institute), 2020) Iseghohi, I.; Abe, A.; Meseka, S.; Mengesha, W.; Gedil, M.; Menkir, A
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.

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