Bacillus subtilis Bs006 FORMULATIONS: STORAGE STABILITY, BIOLOGICAL ACTIVITY AND ENDOPHYTISM IN VEGETABLES

Abstract

Solid and liquid formulations based on the plant growth-promoting bacteria Bacillus subtilis Bs006 were designed as biological inoculant for vegetable nursery production. Considering the importance of microbial survival from the production process to the soil application, spore viability (CFU) in each formulation was assessed during twelve months of storage at 20°C, 30°C, and 40°C. At the three temperature levels evaluated, survival was higher than 85% and 90% for solid and liquid formulations, respectively. The bacterial biological activity was evaluated as plant growth promotion on lettuce, broccoli, and tomato in nursery. The formulations were applied at three concentrations (1x10⁷, 5x10⁷, 1x10⁸ CFU/mL) at sowing and 21 days after seeding. Root and aerial part length and dry weight were the response variables evaluated. A positive effect was observed, particularly with the liquid formulation at 1x10⁸ spores/mL, showing the longest length of root and aerial part and the highest dry weight values in the root and foliar parts. Regarding the endophytism, B. subtilis colonized roots, stems, and leaves, achieving concentrations between 8x10² and 1x10⁵ CFU/g.