Biochemical and antioxidant proprieties associated with the adaptation of faba bean (Vicia faba L.)–rhizobia symbiosis to phosphorus deficit

Faba bean is an important legume species in Morocco due to its ability to fix N_2 in association with indigenous rhizobia. So, exploring this symbiosis to cope with abitic stresses such as phosphorus deficieny is of great importance. This study aims to assess the P deficit (50 μmol plant^-1 week^-1) effects on growth, biochemical and antioxidant responses in six faba bean-rhizobia symbioses involving three Mediterranean varieties, Alfia (AL), Reina Mora (RM) and Luz do Otoño (LO), and two rhizobial strains RhF16T and RhF5T isolated from Haouz region of Morocco. The results showed that P deficit decreased growth and nodulation, increased acid phosphatase (APase), phytase, peroxidase (PO), polyphenoloxidase (PPO) activities and decreased malonyldialdehyde (MDA) content in the nodules. AL-RhF16T presented the lowest reductions in growth (11.3%), nodulation (34.4%), the highest APase, phytase, PO and PPO activities and the lowest MDA content under P deficit. In general, high enzymatic activities in the nodules may improve faba bean tolerance to P deficit, especially in the presence of rhizobial strains with high phosphate solubilization capacity. Based on our results, AL-RhF16T symbiotic combination was qualified as more tolerant to P deficit, while LO-RhF5T was qualified as less tolerant.