Growth Enhancement of Tomato by a Plant Growth Promoting Bacterium, Bacillus subtilis PE7

Abstract

Bacillus species are well recognized as effective bio-stimulants to enhance crop quality and productivity. Our study demonstrates the effect of a plant growth promoting bacterium, Bacillus subtilis PE7 on tomato growth. In vitro screening assay for plant growth promoting traits indicated that the indole-3-acetic acid (IAA) production of B. subtilis PE7 in terms of increasing intensity of pink color with the increasing concentration of ⳑ-tryptophan supplemented in tryptone soy broth (TSB) medium. The supplementation of ⳑ-tryptophan (1 g L -1 ) in the TSB medium resulted in the maximum IAA production of strain PE7 with 25.59 µg mL -1 at 6 days after incubation. Moreover, the highest ammonia production of strain PE7 with 21.22 µg mL -1 was observed at an incubation period of 72 h. The results of our pot experiment revealed that treatment with the strain PE7 culture (inoculated in fertilizer-based medium) induced a significant growth promotion of tomato plants resulting in higher values of leaf number, length, fresh and dry weights of shoot as compared to the control and fertilizer treatment. Therefore, B. subtilis PE7 could be considered as an effective candidate for the development of eco-friendly commercial fertilizer in crop production.