Identifying drought-tolerant genotypes of faba bean and their agro-physiological responses to different water regimes in an arid Mediterranean environment

Faba bean (Vicia faba L.), a major legume crop, helps in maintaining soil health by fixing atmospheric nitrogen (N2) and thus mostly used as a rotational crop. However, faba bean is sensitive to water stress, which limits its yield potential in water-limited environments. The objectives of the present study were to (i) characterize the agro-physiological performance of 14 faba bean genotypes with different genetic backgrounds to various levels of water stress in an arid environment and (ii) identify the most drought-tolerant genotypes that maximize the marginal use of unit water without significant yield loss. Field experiments were conducted for two consecutive growing seasons in an arid Mediterranean climate, and several agronomic and physiological measurements of different faba bean genotypes in response to water stress were recorded. A great variation among the tested genotypes, according to several drought-response indices, was observed as a result of water stress on the basis of which they were classified into five groups (A-E) ranging from drought-tolerant to highly sensitive genotypes. Yield and water productivity results indicated that drought-tolerant genotypes produced more yield with less water compared with drought-sensitive genotypes and thus are highly recommended for faba bean production in water-limited environments. Certain physiological parameters, such as photosynthetic pigment, net photosynthetic rate, transpiration rate, leaf nutrient status (N, P and K content), relative water content and membrane stability index, exhibited highly positive association with seed yield and yield contributing traits. It is valid to use these parameters as rapid indicators of drought tolerance in breeding programs aiming to screen and improve faba bean genotypes for drought tolerance in arid environments.