Alleviation of water stress in soybean symbiosis by salicylic acid and methyl jasmonate-activated Bradyrhizobium.

BACKGROUND

The use of exogenous compounds with growth-regulatory properties can play an effective part in providing plants with the necessary plastic resources for the synthesis of protective compounds. The aim of the research is to determine the effectiveness of salicylic acid and methyl jasmonate treatment for inducing resistance in soybean-Bradyrhizobium symbiosis, and improving symbiotic capacity.

METHODS

Soybean nodule bacteria Bradyrhizobium japonicum cultures were treated with salicylic acid (50 µM) or methyl jasmonate (0.75 µM) and used to create symbioses with soybean. The symbioses were cultivated under normal watering and water stress conditions, and the resulting plants were tested for inter alia pro-oxidant-antioxidant status, productivity and N-fixation activity.

RESULTS

The 0.75 µM methyl jasmonate treatment demonstrated 54.7% catalase and 14.6% greater superoxide dismutase (by 14.6%) activity, as well as and induced two-fold higher hydrogen peroxide, under water stress; in addition, nodulation processes were stimulated by 40% and inhibited nitrogen-fixing activity inhibited by 73.5%. The 50 µM salicylic acid treatment exhibited 54.5% lowered hydrogen peroxide, but 20.7% greater superoxide dismutase activity and 44.8% higher catalase activation water stress; this increased the efficiency of molecular nitrogen fixation (by 23.5%) and productivity (by 15.9%) in soybeans.

CONCLUSIONS

Effect of 50 µM SA-treated Bradyrhizobium effectively activates the protective antioxidant mechanisms of soybean, improving symbiotic capacity and stress tolerance. Methyl jasmonate 0.75 µM in combination with Bradyrhizobium stimulates nodulation and inhibites nitrogen fixation in soybean under both optimal and insufficient water supply.