Selection of cowpea cultivars for high temperature tolerance: physiological, biochemical and yield aspects

High temperature stress can hinder the development of cowpea resulting in several damages including vegetative and reproductive phases of the crop. In this context, the objective of this study was to select cowpea cultivars tolerant to high temperature stress using various parameters related to physiological, biochemical, and yield aspects. For this, the cultivars Carijo, Itaim, Pujante, Rouxinol, and Tapahium were used, maintained in two temperature regimes: 20-26-33 degrees C and 24.8-30.8-37.8 degrees C. The experiment was carried out in growth chambers, in a 5 x 2 factorial arrangement (cultivars x temperature regimes). Responses differentiated among the cultivars Carijo, Itaim, Pujante, Rouxinol, and Tapahium with the increase of 4.8 degrees C in air temperature. The high temperature promoted a greater quantity of aborted flowers, leading to a reduction in the yield of the cultivars Carijo, Pujante, Rouxinol, and Tapahium. The photosynthesis, stomatal conductance, leaf transpiration and enzymatic activities were significantly influenced by high temperature. From the combination of the responses of biometric, physiological and productive variables, the cultivar Itaim can be considered as tolerant to an increase of 4.8 degrees C in air temperature.