Bacillus Strains with Catalase Enzyme Improve the Physiology and Growth of Rice (Oryza sativa L.)

Catalase can decompose hydrogen peroxide in plants under controlled and stressed conditions. In a stressed environment, an increase in hydrogen peroxide production makes catalase activity a major defense system for plant growth. The current study was conducted to evaluate the catalase activity of the pre-isolated and identified bacterial strains Bacillus aryabhattai (AN30), Bacillus megaterium (AN24), Bacillus megaterium (AN31) and Bacillus megaterium (AN35) and their potential for rice seedling growth promotion. These strains were characterized for quantitative catalase, urease, siderophore and exopolysaccharide production using LB media. Subsequently, the effectiveness of these strains was checked by quantifying the catalase activity in the rhizosphere, roots and shoots of rice seedlings. The secretion of organic and phenolic compounds produced by the tested strains in liquid culture was also investigated. Plant growth parameters were also studied in a growth room trial. Our results showed that the strain AN24 showed the maximum catalase activity (1.36 mol cm−1), urease activity (1.35 mol cm−1) and exopolysaccharide (4.20 µg mL−1) and siderophore (2.32%) production in LB media. All tested strains showed significantly higher catalase activity in soil compared to the control. Among sole applications, strain AN24 showed better results; however, the consortium application of strains AN24 + AN30 + AN35 + AN31 showed the maximum improvement in dry biomass, shoot and root length, and increase in catalase activity of rice seedlings. The results showed that a consortium of these Bacillus strains with catalase activity has greater potential to enhance the antioxidant defense system and growth promotion of rice seedlings. However, further experimentation under natural conditions is required before using these strains as potential bioinoculants for improving rice growth and yield.