Monitoring of Drought Adaptive Mechanisms of Some Cowpea (Vigna unguiculata) Genotypes Grown Under Water Deficit Conditions in Burkina Faso

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Résumé

Cowpea is an essential crop in Burkina Faso’s agriculture, but its production must cope with the consequences of climate change, particularly drought, which significantly reduces yields. The mechanisms of adaptation to drought vary between species and varieties and need to be understood to develop more drought-tolerant varieties. Seven cowpea genotypes were subjected to a 21-day water deficit induced before flowering under a screen house, using plastic pots. A split-plot design with three replications was used. The water regimes included continuous watering and induction of a 21-day water deficit initiated from the 30th day after sowing (DAS). Physiological, morphological, and productivity parameters were measured before and during the water deficit application. The results demonstrated a significant depressive effect of stress conditions on the evaluated parameters. The water deficit reduced average grain weight by 47% and fodder weight by 38%. Tolerant genotypes displayed distinct adaptive strategies, including enhanced root elongation, reduced leaf size and plant height, and lowered leaf water potential, while maintaining high chlorophyll content under drought. Notably, TN88-63, Gorom local, IT98K-111-1, and Bambey 21 exhibited the most effective water management, improving water uptake and limiting water loss through reduced stomatal conductance and smaller transpiring leaf surface. By contrast, KVx441-2 was more sensitive to water deficit. This study provides additional answers by highlighting the specific mechanisms of drought tolerance in different cowpea genotypes. These genotypes could be used in breeding programs with a view to investigating how these adaptation traits can be passed on to offspring.

Mots-clés

Cowpea · Genotypes · Drought · Stomatal conductance · Leaf water potential · Roots longer · Productivity