Study on the Growth Promotion Effect and IAA Production Capacity of Bacillus subtilis B9

PurposeB9 strain is an endophytic Bacillus subtilis isolated from the root of sugarcane. The study on its growth-promoting effect and indole-3-acetic acid (IAA) production capacity provides a theoretical basis for the development of high-efficiency microbial fertilizer inoculant.

MethodCorn seed, sugarcane single bud stem and sugarcane tissue culture seedlings were test materials, and corn seed and sugarcane single bud stem were inoculated by soaking, and the optimal growth concentration of B9 was explored. Their growth potential was observed and the bud length, root length, plant height, root number and root weight were measured. The roots of the sugarcane tissue culture seedlings were inoculated by root irrigation, and the root growth of the tissue culture seedlings was observed. The root length, plant height, root activity, nitrogen metabolism related enzyme activities, chlorophyll and photosynthetic indexes of the potted seedlings were measured. The use of liquid chromatography-mass spectrometry (LC-MS) to detected probiotic-related substances of content in indole-3-acetic acid (IAA).

ResultThe dilution of B9 bacteria had a certain promoting effect on corn seeds and seedlings. The growth-promoting effect showed an increasing first and then decreasing trend with the increase of the dilution factor. At the concentration of 1.0×10⁶ CFU/mL, the effect on corn growth is optimal. The related morphological and agronomic characters of sugarcane single bud stem were significantly better than those of clear water by treatment with 1.0×10⁶ CFU/mL B9 bacterial solution (P<0.05). At this concentration, plant height, root length, chlorophyll content, glutamine synthetase (GS), glutamate synthase (GOGAT), net photosynthetic rate (P_n), stomatal conductance (G_s), transpiration rate (T_r), root activity of sugarcane tissue culture seedlings were significantly better than CK treatment. In the B9 bacterial solution of LB medium, the increase indole-3-acetic was significant, reaching (95.63±2.33) ng/mL at the 9 d and an increase of 1054.9% over the blank control. In the Landy medium, the indoleacetic acid was detected to be increasing trend, which was 2.56 times higher than the control at the 9 d.

ConclusionIn conclusion, B9 strain has obvious growth promotion effect on sugarcane and corn, and the secretion capacity of IAA in fermentation liquid is strong.