Yield and seed quality parameters of common bean cultivars grown under water and heat stress field conditions

Drought and heat stress strongly influence common bean development. The aim of this work was to study the effect of water stress on yield and quality traits of four common bean cultivars under xerothermic Mediterranean conditions. The field experiments were conducted under normal and water stress (50% of the normal) conditions applied 25 days after seed emergence (first flower buds visible). Agronomic, physiomorphological, quality traits and drought indices were assessed. Water stress reduced the number of pods plant(-1) (53%), seeds pod(-1) (9.7%), harvest index (49%) and seed yield (58%). Cultivar 'Cannellino' provided the higher performance both under normal and water stressed conditions and exhibited the lower drought susceptibility index and the highest mean productivity and geometric mean productivity across water treatments. These results were attributed primarily to the earliness of the cultivar 'Cannellino' which enabled avoidance of very high temperatures and severe drought and to the robustness and quick pod set. Valuable genetic variability was also observed for important quality seed traits (cooking time, protein). In conclusion, water stress is a significant limiting factor for seed yield and quality traits eventhough, suitable cultivars (i.e. 'Cannellino', 'G. Northern') were indentified in the course of this study. It is suggested that breeders select for early-flowering and quick pod-setting varieties to reduce the negative effects of water and heat stress in these environments.