Role of Bacillus subtilis BE-L21 in enhancing the heat tolerance of spinach seedlings

Abstract

Owing to cold resistance and a lack of heat resistance in spinach (Spinacea oleracea L.), heat is the primary constraint that limits its production in summer. This study examined the auxiliary effects of spinach rhizosphere microbes on improving the heat resistance of spinach. A strain isolated from the rhizosphere soil of heat-stressed spinach was identified as Bacillus subtilis and designated B. subtilis BE-L21. It produces indoleacetic acid, amylase, and protease and solubilizes phosphorus. Further research revealed that spinach seedlings inoculated with this strain of B. subtilis had increased content of soluble protein, soluble sugar, and proline that adjusted their osmotic potential. The reducing content of malondialdehyde showed alleviated irreversible damage of spinach plants under heat stress. Also the increased activities of antioxidant enzynes peroxidase, superoxide dismutase, and catalase enhanced the heat resistance of spinach. The results indicate that B. subtilis BE-L21 can contribute to tolerance of spinach seedlings to elevated temperatures by inducing physiological and biochemical changes in the plant.