Maize Genomics and Genetics 2025, Vol.16, No.1, 10-19 http://cropscipublisher.com/index.php/mgg 15 Additionally, the research on genotype by environment interaction and yield stability found significant genetic correlations between grain yield under managed drought stress and yield under Striga-infestation and multiple rainfed environments, with correlation coefficients of 0.51 and 0.57, respectively (Menkir et al., 2020; Zheng et al., 2023). These correlations imply that selecting for yield stability under one stress condition could potentially improve performance under other stress conditions, facilitating the development of robust maize lines. 6 Insights from Maize Line Evaluation 6.1 Interpretation of results The evaluation of maize lines revealed several key traits contributing to improved maize quality and stress resistance. Notably, the presence of additive gene effects was significant for most traits under combined drought and heat stress (CDHS), except for grain yield, which was influenced by non-additive gene effects. This suggests that selecting for traits such as chlorophyll content, transpiration rate, and proline content, which exhibited higher levels under water stress conditions, could be beneficial for developing stress-resistant maize lines (Chiuta and Mutengwa, 2020; Balbaa et al., 2022). Additionally, the identification of inbred lines with good combining ability for yield under CDHS, such as L30, L6, L5, L17, and L2, indicates their potential as parental lines in hybridization programs (Table 2) (Chiuta and Mutengwa, 2020). Table 2 General combining ability effects for yield,yield components and other morpho-agronomic traits under combined drought and heat stress conditions (Adopted from Chiuta and Mutengwa, 2020) Inbred Line GY CL NRE EPP CC DS DT ASI CT PH GCAf L2 0.01 -0.31 0.33 -0.04 1.44 -2.51 -0.60 -1.78 -0.26 -2.47 L5 0.04 0.19 -0.39 0.01 -2.51 -0.24 -0.68 0.44 0.95 -2.62 L6 0.08 -0.45 -0.17 -0.10 -0.33 1.76 1.54 0.22 0.42 6.17 L14 -0.12 0.57 0.22 0.13 1.40 0.99 -0.13 1.11 -1.11 -1.07 GCAm L13 -0.03 0.62 -0.44 -0.10 3.22 -1.01 -1.29 0.28 -0.85 -9.81 L16 -0.10 0.11 0.31 -0.01 0.43 -0.10 -0.46 0.36 0.82 -20.08 L17 0.04 -0.47 0.14 -0.01 2.19 -1.01 -0.71 -0.31 0.60 3.79 L18 -0.05 -0.72 0.81 0.07 -7.36 0.99 1.38 -0.39 1.43 11.17 L27 -0.01 0.72 -0.94 0.15 0.01 0.65 0.46 0.19 -1.96 10.67 L30 0.14 -0.26 0.14 -0.10 1.51 0.49 0.63 -0.14 -0.04 4.26 Table caption: GY=grain yield, CL=cob length, NRE=number of rows per ear, EPP=ears per plant, CC=chlorophyl content, DS=days to 50% silking, DT=days to 50% anthesis, ASI=anthesis-silking interval, CT=canopy temperature, PH=plant height, GCAf=general combiningability (female) and GCAm=general combining ability (male) (Adopted from Chiuta and Mutengwa, 2020) Furthermore, the study highlighted the importance of both additive and dominance gene effects in controlling traits under various stress conditions. For instance, lines L6 and L7 showed positive general combining ability (GCA) effects for grain yield and secondary traits under optimal and low nitrogen conditions, while L8 and L9 were good general combiners under heat and drought stress conditions (Matongera et al., 2023). This dual influence of gene effects underscores the complexity of breeding for stress resistance and the necessity of a multifaceted approach in selecting superior maize lines. 6.2 Comparisons with previous studies Comparing the current study’s results with previous research validates the findings and provides a broader context. For example, the significant influence of additive gene effects on traits under stress conditions aligns with earlier studies that reported similar genetic control mechanisms for drought and heat tolerance in maize (Chiuta and Mutengwa, 2020; Dawaki et al., 2023). Additionally, the identification of specific combining ability (SCA) effects for yield under stress conditions corroborates findings from other studies that emphasized the role of non-additive gene effects in enhancing grain yield under adverse conditions (Chiuta and Mutengwa, 2020; Okunlola et al., 2023).
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