Rhizobial-metabolite based biocontrol of fusarium wilt in pigeon pea.

The application of rhizobial cells for improving pigeon pea fitness has been practiced for ages. As cell-based approaches have limitations, the focus is on the usage of cell-free formulations. In the present study exopolysaccharide (EPS) producing, plant health promoting Bradyrhizobium sp. IC-4059 was monitored for its biocontrol potential against Fusarium udum. Strain IC-4059, its EPS, and supernatant antagonized F.udum by 52.6%, 20.5%, and 48.1%, respectively in comparison to control. Diverse formulations prepared using EPS, supernatant, and cells of strain IC-4059 were: EPS based, supernatant based, IC-4059 liquid culture (rhizobia based), dual combination (IC-4059 cells + supernatant; IC-4059 cells + EPS; EPS + supernatant), and triple combination (IC-4059 cells + supernatant + EPS). The potency of these bioformulations was observed under in planta tubes followed by in vivo pot study, both in F.udum infested and non-infested sets taking pigeon pea cultivar UPAS-120 as a model crop. The study highlighted that seeds receiving triple combination exhibited significantly higher plant growth attributes, nodule enhancing, and disease suppressing activity in comparison to individual application of Bradyrhizobium. Antifungal compounds were analyzed by a metabolomic approach using UPLC-MS. Thus, the study disseminates the tripartite role of triple formulation as a plant growth stimulator, nodule enhancer, and disease suppressor, both under in vitro and in vivo conditions in the presence of phytopathogen F. udum.