A bacterial formulation based on two exopolysaccharide-producing rhizobacteria from Dongxiang wild rice (Oryza rufipogon Griff.) confers drought tolerance in cultivated rice Dongdao-4 (Oryza sativa L.)

Abstract Objectives. The present study aims to isolate exopolysaccharide-producing bacterial strains from the rhizosphere of Dongxiang wild rice (Oryza rufipogon Griff.); elaborate a bacterial formulation, and quantify its effect on the defense against stress in cultivated rice seedlings under drought. Methods. Dongxiang wild rice rhizospheric soil was used to isolate exopolysaccharide-producing bacteria; and bacteria isolates were identified, at the taxonomic level of genus, following polyphasic methods. A bacterial formulation was made; and the enzymatic activity and the malondialdehyde content were quantified; in addition to measuring morphological indicators of growth in cultivated rice Dongdao-4 (Oryza sativa L.) seedlings under drought stress. Results. The inoculation of cultivated rice with the bacterial formulation made from two selected isolates had positive impacts on growth parameters and the antioxidant defense under drought, significantly surpassing the effect of the commercial products PB (Biofertilizer P) and EM (Efficient Microorganisms). Even the shoot length of the inoculated plants under drought does not differ significantly from control plants under normal water conditions; while the root dry weight was significantly higher. The enzymatic activity of the inoculated plants significantly exceeds the other treatments in drought; and the malondialdehyde content was the lowest of the treatments. The exopolysaccharides-producing bacterial strains mitigate the adverse effects of drought stress; and the bacterial formulation improve relevant parameters of the plants under drought, and can be used as a potential inoculant in arid zones. Conclusions. This study demonstrates the efficacy of exopolysaccharide-producing Dongxiang wild rice rhizobacteria in improving drought tolerance and consequently enhancing plant growth.