Abstract
Drought and heat stress have perceptibly become major maize (Zea mays L.) yield reducing factors in Sub-Saharan Africa. As such, the objectives of this study were to: (i) determine the type of gene action conditioning tolerance to combined drought and heat stress (CDHS), and (ii) identify inbred lines with good combining ability for yield and other morpho-agronomic traits under CDHS. Twenty-four single cross hybrids (SCHs) obtained from crossing 10 inbred lines in a 4 × 6 North Carolina Design II, and a drought-tolerant check, were evaluated under CDHS and optimum conditions in the field. The experiment was laid out in a 5 × 5 alpha lattice incomplete block design, replicated three times. Additive gene effects influenced all the traits under CDHS except grain yield, which was influenced by non-additive gene effects. A preponderance of additive genetic effects was observed for all traits recorded under optimum conditions. Inbred lines L30, L6, L5, L17 and L2 showed good combining ability for yield under CDHS, indicating that they could be good parental lines in hybridization programs. Based on the results, SCHs L2*30, L6*13 and L5*18 exhibited high specific combining ability (SCA) effects for yield under CDHS. These hybrids are recommended for further multi-locational evaluation to determine the stability of their performance.
Highlights
Quality protein maize (QPM) has double the amounts of essential amino acids, namely lysine and tryptophan, compared to normal maize [1]
Under combined drought and heat stress (CDHS) conditions, the mean sum of squares for GCAm was significantly different at p ≤ 0.05 for all traits except ears per plant, anthesis-silking interval, grain yield and cob length (Table 3)
The mean squares for general combining ability of females (GCAf) were significantly different at p ≤ 0.05 for most traits except plant height, ears per plant, chlorophyll content and cob length only
Summary
Quality protein maize (QPM) has double the amounts of essential amino acids, namely lysine and tryptophan, compared to normal maize [1]. QPM can be an excellent source of protein in areas where maize is the staple food. Due to its nutritional value, QPM can be added into animal feed where it can be used as a supplementary protein source. Studies by Tiwari et al [2] observed that broiler chickens fed on QPM increased in weight by approximately 8% compared to chickens fed on normal maize. Maize cultivars that are good for both human food and fodder purposes have far received little attention in breeding programs for tolerance to abiotic stresses [3]. Drought and/or heat stress have perceptibly become major maize yield reducing factors in
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