Abstract
Genetic gain studies in a breeding program are very important for measuring the efficiency of the program over a specific period. It also provides breeders with an understanding of the outcomes of the huge investments committed to the breeding programs. This study sought to (i) estimate the gains in grain yield under drought and rainfed conditions and (ii) identify high-yielding and stable hybrids developed in the last two decades under drought and rainfed conditions. Sixty extra-early maturing hybrids developed by the International Institute of Tropical Agriculture (IITA), Ibadan, during three breeding periods: (2008–2010, 2011–2013, and 2014–2016) were assessed under managed drought and rainfed conditions across 14 environments in Nigeria to estimate the genetic gains in grain yield using linear regression analysis. Considerably high genetic gains (4.1%) per year for grain yield was obtained for the extra-early maturing hybrids under drought environments. Six of the top ten hybrids identified were from period 3, an indication of the high genetic gains from selection in period 3. Additionally, two of the top six period 3 hybrids (TZEEI 29 × TZEEI 13) × TZEEI 64 and TZdEEI 64 × TZEEI 54 were found to be the best yielding and most stable across the 14 test environments and were highly recommended for extensive evaluations to warrant their commercialization in sub-Saharan Africa (SSA).
Highlights
Drought stress alone could lead to 40–90% loss in grain yield (GY) if it occurs at the same time as the flowering or grain-filling periods [8,9,10]
The analysis of variance (ANOVA) for the combined data of the 60 extra-early hybrids revealed a significant variance for GY and the related traits for period, environment (Env), hybrid, Env × Hybrid, and Env × period (Table 2)
Of the overall sum of squares across drought and well-watered conditions. This indicated that each research condition was distinct from the others; performing separate ANOVA for the two different soil moisture conditions was necessary
Summary
In the savannas of SSA, cultivation and use of the extra-early (80–85 days to obtain physiological maturity) maturing varieties [4] have been phenomenal in bridging the hunger gap within the cropping cycle, especially in the rural communities. This has paved the way for the acceptance of the extra-early maize varieties in areas of shorter unimodal rainfall distribution of the savanna of SSA which until a few decades ago had not been considered suitable for intensive maize cultivation [3]. Grain yield losses of 53% was reported when early maturing maize varieties were tested under drought environments in Nigeria [11]
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