Plant growth-promoting rhizobacteria and biochar as bioeffectors and bioalleviators of drought stress in faba bean (Vicia faba L.)

Plants are subjected to a variety of abiotic stressors, including drought stress, that are fatal to their growth and ability to produce under natural conditions. Therefore, the present study was intended to investigate the drought tolerance potential of faba bean (Vicia faba L.) plants under the co-application of biochar and rhizobacteria, Cellulomonas pakistanensis (National Culture Collection of Pakistan (NCCP)11) and Sphingobacterium pakistanensis (NCCP246). The experiment was initiated by sowing the inoculated seeds with the aforementioned rhizobacterial strains in earthen pots filled with 3 kg of sand-mixed soil and 5% biochar. The morphology of biochar was observed with highly porous nature, along with the detection of various essential elements. The biochemical and physiological data showed that phenolic compounds and osmolytes were adversely affected by the induction of drought stress. However, the application of biochar and rhizobacteria boosted the level of flavonoids on average by 52.03%, total phenols by 50.67%, soluble sugar by 82.85%, proline by 76.81%, glycine betaine by 107.25%, and total protein contents by 89.18% in all co-treatments of biochar and rhizobacteria. In addition, stress indicator compounds, including malondialdehyde (MDA) contents and H2O2, were remarkably alleviated by 54.21% and 47.03%, respectively. Similarly, the amplitude of antioxidant enzymes including catalase, peroxidase, superoxide dismutase, ascorbate peroxidase, and guaiacol peroxidase was also enhanced by 63.80%, 80.95%, 37.87%, and 58.20%, respectively, in all co-treatments of rhizobacteria and biochar. Conclusively, biochar and rhizobacteria have a magnificent role in enhancing the drought tolerance potential of crop plants by boosting the physio-biochemical traits and enhancing the level of antioxidant enzymes.