Effect of genotypes and artificial shading during flowering stage on the productivity patterns of Faba bean (<i>Vicia faba</i> L.) under Mediterranean conditions

In agroforestry systems, higher-positioned crops frequently tend to impose shade stress on lower-positioned ones, with consequent negative repercussions on the agronomic characteristics of the latter. The present study was conducted under field conditions over two cropping seasons 2020-2021 and 2021-2022, to evaluate the mechanisms of physiological (e.g., stomatal conductance and water relative content) and biochemical (e.g., proline and chlorophyll content) variations, as well as grain yield and its components of different Faba bean varieties subjected to shade stress. Six varieties of Vicia faba L. (Aguadulce, Hiba, Zina, Alfia17, Defes, and Extra hative) were subjected to three levels of artificial shade stress S1 (0%), S2 (50%), and S3 (90%) during the flowering stage. The results showed that variety, shade treatment, and year significantly affected above-ground biomass and yield attributes. Substantial reductions in grain yield of 31.17% and 53.34% were observed under S2 and S3, respectively, compared with S1, demonstrating the adverse impact of shading on this parameter. Significant differences between the studied varieties were noticed. Among the varieties tested, Hiba and Zina showed the highest grain yield under shade stress conditions. Shading decreased stomatal conductance for all varieties tested, influencing proline synthesis in response to this abiotic stress. The results suggest that incorporating high-performance varieties Hiba and Zina into agroforestry systems can provide significant added value to local farmers since they are the most tolerant to shade stress, which can improve the performance of the tree-plant association in terms of yield and productivity.