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Objective : To obtain high yields under more and more irregular agro-climatic conditions, varieties with high resistance to drought in different stages of their cycles are necessary. The objectives of this study are to obtain tolerant cowpea varieties by using parents with different mechanisms of tolerance and to understand mechanisms of tolerance to drought in cowpea. Methodology and Results : Eight varieties were estimated for their response to different hydric conditions.. The transpiration of well watered plant under different VPD (vapor pressure deficit) was estimated in a pot. In the field, plants were subjected to two water conditions, intermittent and terminal stress. The transpiration at 3 pm (the highest VPD) was low in the tolerant genotypes compared with the sensitive genotypes. The leaf area index decreases while the leaf temperature increased significantly under water deficit. Mouride and IT93K-503-1 had the highest grain and fodder yield of ten plants. The terminal stress proved more severe than the intermittent stress. IT93K-503-1 had the greatest specific leaf area, a transpiration curve accorded to the VPD different from those of the other varieties, a high leaf temperature and a long life cycle. Mouride had important leaf area and pod harvest index. Mouride is more adapted to the terminal stress and has a good tolerance in the intermittent stress. IT93K-503-1 is more adapted to the intermittent stress than Mouride but had a low yield in seeds during the terminal stress. Mouride and IT93K- 503-1 had different physiological responses. Leaf area index and leaf temperature are correlated to the variables of yield. Conclusion and application of results : This work permitted to highlight the importance of some physiological and agronomic parameters in the breeding for drought tolerance in cowpea. Mouride and IT93K-503-1 are adapted genotypes to water stress with different mechanisms. These results can let us understanding more the mechanism of drought tolerance in cowpea and these two genotypes can be used in a program of breeding for varieties adapted to the terminal and intermittent drought. Keywords : Cowpea; drought resistance; transpiration; VPD; leaf temperature; yield.

Amélioration de l’adaptation à la sécheresse chez le niébé (<i>Vigna unguiculata</i> L. Walpers).