Auxin Production by Bacillus simplex Enhanced the Growth of Zea mays (L.) under In-Vitro and In-Vivo Conditions

Abstract

In the current study Bacillus simplex was evaluated for its role inimproving the growth of maize (Zea mays (L.)) under lab and natural environmental conditions. Bacterial strains were tested for several biochemical traits and auxin biosynthesis. Maize seeds were surface sterilized and treated with bacterial strains as single and mixed cultures to evaluate the enhancement of maize vegetative growth parameters. All bacterial strains exhibited positive results for catalase, citrate and nitrate while negative for urease, indole, triple sugar iron and oxidase test. Colorimetric analysis revealed significant production of auxin by Z-13 (6.7μg/ml), Z-09 (5.8μg/ml), Z-37 (5.7 μg/ml), Z-38 (5.7μg/ml), Z-02 (5 μg/ml), Z-37 (4.5 μg/ml)and Z-04 (3.5 μg /ml) at 1000μg/ml concentration of L-tryptophan. At 0 μg/ml conc of L-tryptophan, Z-37, Z-13, Z-04, Z-09and Z-38 also manifested significant levels of auxin biosynthesis. In-vitrorooting assay revealed that Z-09, Z-35 and Z-37 showed significant increase in root length i.e., 1.2, 1.18 and 1.11-fold, respectively, as compared to control. Pot trials under natural conditions manifested significant improvements in shoot length by Z-38 (67.1%), Z-13 (51%), and Z-09 (43%), over control. Most significant results for fresh weight (120%) and dry weight (100%) in maize were shown by strain Z-38. Among mixed cultures C-1 (Z-02, Z-04, Z-09) improved shoot length (42%) and fresh weight (45%) with respect to control. Improvement in vegetative growth parameters of maize suggests that B. simplex can be used as an effective biofertilizer.