Abstract
Knowledge of the genetic mechanisms conditioning drought tolerance in maize is crucial to the success of hybrid breeding programs aimed at developing high-yielding cultivars under drought. The objectives of this study were to determine the combining ability of extra-early inbreds, compute the heritability of measured traits, assess the performance of inbreds in hybrid combinations and investigate the associations among traits under drought and optimal conditions. A total of 252 hybrids generated by crossing 63 inbreds to four testers, along with four commercial hybrid checks, were evaluated for 2 years under drought and rainfed conditions. General combining ability (GCA) and specific combining ability (SCA) for the traits were significant. A total of 57.1% and 53.4% of the genotypic sum of squares were attributable to GCA effects for grain yield under managed drought and rainfed conditions, respectively. Hybrids TZdEEI 91 × TZEEI 21 and TZdEEI 55 × TZEEI 13 out-yielded the best checks under drought and optimal conditions by 49.13% and 39.05%, respectively. The most promising hybrids with consistently high grain yield under drought and rainfed conditions, were TZdEEI 54 × TZEEI 13, TZdEEI 91 × TZEEI 21 and TZdEEI 55 × TZEEI 21 and should be further evaluated for possible commercial production in sub-Saharan Africa.
Highlights
Maize (Zea mays L.) is ranked among the top three most widely cultivated cereal crops globally, with a total production of 114.75 million tons in 2019 and a projected increase in production of 6.47% in [1]
The general combining ability (GCA) (GCA-line + GCA-tester) variance was higher than the variance for specific combining ability (SCA) of hybrids for grain yield, days to 50% silking (DS), days to 50% anthesis (DA), plant height (PLHT), ear aspect (EASP) and Plant aspect (PASP), whereas the SCA variance of hybrids were more important for anthesis–silking interval (ASI), ear height (EHT), Ears per plant (EPP) and leaf death score (LD) under drought conditions
GCA variance for grain yield, DA, DS, PLHT and EHT was greater than the SCA variance, whereas the SCA variance for ASI, PASP, EASP and EPP was greater than the GCA variance
Summary
Maize (Zea mays L.) is ranked among the top three most widely cultivated cereal crops globally, with a total production of 114.75 million tons in 2019 and a projected increase in production of 6.47% in [1]. In most parts of Africa, maize serves as an important staple cereal crop and is utilized in preparing a variety of local dishes and as feed for animals. Despite the enormous potential and crucial role that maize plays in sub-Saharan Africa (SSA), its production and average yield per hectare are low because of recurring droughts during the cropping season. About 15% of the annual yield loss in SSA has been attributed to drought stress [2]. 17% yield loss attributable to drought stress, while drought stress in southern Africa reportedly causes. Reduction in maize grain yield attributable to inadequate moisture depends on the developmental stage of the crop at which the drought occurs, and on the intensity and duration of the drought [7,8]
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