Water Use Efficiency in Common Beans Under Cool Temperatures

The common bean (Phaseolus vulgaris L. ) a warm season legume, is considered the most important food legume for humans globally because it provides 30 % of the protein and calories of diets in many countries. However, drought is considered a major issue affecting the worlds production of P. vulgaris. Therefore, there has been a growing demand recently for improving common beans so that they become more tolerant to drought stress. Drought-adaptation mechanisms in common beans include deep root systems, increased water use efficiency (WUE), ratio between photosynthesis and transpiration, and transfer of photosynthate to seed via efcient mobilisation. WUE contributes to increasing yield under drought, and is associated with physiological processes of the plant such as leaf gas exchange, stomatal conductance, osmotic adjustment and root characteristics. Recently, breeding crops to make more efficient use of water is one of the most important strategies that has become an urgent necessity. Phaseolus beans are being proposed as a potential alternative legume crop for mild winter, rain-fed cropping seasons and the current research aims to assess their water use efficiency and drought tolerance under cool temperatures in comparison to already adapted cool-seasons legumes such as lupin.