Heterosis and Combining Ability for Striga Tolerance in Maize (Zea mays L.)
N’da Hugues Annicet *
National Agricultural Research Center, 01 BP 121 Ferké 01, Côte d’Ivoire.
Konaté Dofougo
National Agricultural Research Center, 01 BP 121 Ferké 01, Côte d’Ivoire.
Kouakou Kouakou Romaric
National Agricultural Research Center, 01 BP 121 Ferké 01, Côte d’Ivoire.
N’cho Achi Laurent
National Agricultural Research Center, 01 BP 121 Ferké 01, Côte d’Ivoire.
Letto Kouakou Yann Cédric
National Agricultural Research Center, 01 BP 121 Ferké 01, Côte d’Ivoire.
*Author to whom correspondence should be addressed.
Abstract
Background: Maize is a major staple in sub-Saharan Africa, but its production is severely constrained by Striga hermonthica, which causes significant yield and economic losses. Developing tolerant varieties remains the most sustainable control strategy.
Aims: To evaluate 45 F1 hybrids from a 10×10 diallel cross of maize inbred lines for Striga (Striga hermonthica) tolerance, estimate combining ability parameters, and identify the best hybrid combinations for infested zones in Côte d'Ivoire.
Study Design: Randomised complete block design with two replications per environment.
Place and Duration of Study: CNRA research station, Ferkessédougou, northern Côte d'Ivoire, 2024.
Methodology: Fifty-five genotypes (45 hybrids + 10 parents) were evaluated under non-infested and artificially Striga-infested conditions (5,000 germinable seeds m⁻²). Combining ability was estimated using Griffing’s (1956) Method 4 with a fixed-effects model, focusing specifically on the 45 F1 hybrids to determine GCA and SCA effects. Mid-parent (MPH) and better-parent (BPH) heterosis were computed. Pearson correlations were calculated among measured agronomic traits.
Results: Combined ANOVA showed highly significant effects (**) of genotype, environment and G×E interaction for all traits. Mean yield reduction due to Striga was 62.8% in parents and 45.3% in hybrids. Using Griffing’s Method 4, genetic analysis revealed that non-additive effects predominated in tolerance expression, as indicated by a σ2SCA/σ2GCA ratio of 4.32 under infested conditions versus 3.17 in non-infested environments. Lines P8 (TZMI 20672) and P10 (TZMI 1262) showed the highest GCA effects under stress (0.92 and 0.88, respectively). Hybrids P5×P10, P2×P8 and P8×P10 yielded above 6.5 t ha⁻¹ under infestation with reductions below 35% and highly significant SCA effects.
Conclusion: Heterosis exploitation offers substantial gains in Striga tolerance. Lines P8 and P10 are major tolerance sources for breeding programmes. Hybrids P8×P10, P5×P10 and P2×P8 are priority candidates for national catalogue registration; however, their stability across diverse environments remains to be confirmed through multi-location validation before broad commercial recommendation.
Keywords: Zea mays L., Striga hermonthica, Côte d'Ivoire, combining ability, GCA, SCA, heterosis, tolerance