Impact of Bacillus subtilis on Tomato Plants Growth and Some Biochemical Characteristics under Combined Application with Humic Fertilizer

In this study we investigated the mechanisms of action and effect of plant growth promoting rhizobacteria (PGPR) Bacillus subtilis No.2 when utilized alone and in conjunction with a humic fertilizer (HF). Different mechanisms of action of B. subtilis No.2 and HF Stimulife on tomato plants were identified in pot experiments under controlled conditions. PGPR B. subtilis No.2 was identified by using the16s rRNA gene sequence method. We applied factor analyses to evaluate differences in the responses of plants to the individual effects of B. subtilis No.2 and HF when they were used together. Auxin-producing B. subtilis No.2 enhanced tomato yield by increased average number of fruits per plant. Humic fertilizer Stimulife, which also contains auxins, improved tomato yield by increasing average fruit weight. As shown by factor analysis, the impact of weight coefficients for plant responses (across tomato varieties) to B. subtilis No.2 and Stimulife were 0.54 and 0.28, respectively, indicating a greater response to B. subtilis No.2 than to HF Stimulife. Combined use of Stimulife and B. subtilis No.2 had a positive impact on tomato yield, increasing fruit yield by 25-29%. Tomato fruit quality was improved by increasing the amounts of dry matter, carbohydrates, sugar-index acid, and ascorbic acid. Results suggest that HF Stimulife and B. subtilis No.2could be successfully used to enhance tomato plant growth and yield under controlled conditions. We hypothesize that, along with direct impact, HF may also indirectly affect plants by stimulating PGPR.