Responses of seven cowpea (Vigna unguiculataL. WALP) genotypes to 14-day water deficitsat various phenological stages

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Résumé

In West Africa, cowpea is a key crop valued for its nutritional, ecological, andeconomic value. However, this region of the world frequently suffers from drought,which severely compromises the productivity of this species. Varietal selection, oneof the most effective approaches to adressing this constraint, requires identifyingthe most sensitive stages of development and selecting high-performance varietiesfor breeding programmes. This study evaluated the agronomic responses of sevencowpea genotypes subjected to a 14-day water deficit at four phenological stages(20, 30, 40, and 50 days after sowing) using a completely randomized block designwith three replicates under controlled greenhouse conditions, with the aim ofidentifying genotypes likely to be tolerant at different stages of development andstress levels. Total grain weight (g) per genotype under each water regime wasused as the primary performance criterion. Under continuous irrigation (WR0), grainweights ranged from 2.83 ± 0.28 g (KVx150) to 7.80 ± 0.37 g (Waongo), with a meanof 5.39 ± 0.44 g. The early vegetative stage (20 DAS) was the most critical, with amean grain weight of only 0.29 ± 0.11 g across surviving genotypes, representingan average loss of 94.95% relative to WR0. In contrast, the pod-filling stage (50 DAS)showed the lowest impact, with a mean grain weight of 1.06 g and average lossesof 74.65%. Based on drought tolerance indices (GMP, STI, YI), Waongo recorded thehighest grain weight across all stress regimes (0.83 g at WR1, 1.76 g at WR2, 2.10 gat WR3, and 1.43 g at WR4), making it the best overall performer. IT93K-503-1 alsoperformed well, with a total grain weight of 6.50 ± 0.30 g under WR0 and a higherhundred-grain weight than Waongo across most regimes, but showed sensitivity tostress applied at 40 DAS (0.90 ± 0.36 g, loss of 86.15%). The performances of Waongoand IT93K-503-1 are attributed to mechanisms ranging from cell turgor maintenanceto phenological plasticity, making them suitable candidates for drought breeding programmes.

Mots-clés

Cowpea, Water deficit, Intermittent stress, Tolerance, Drought indices