Isolation and identification of Bacillus tequilensis JN-369 and antimicrobial substance analysis

In order to screen the resources of biocontrol bacteria strains for the control of rice blast caused by Magnaporthe oryzae, a bacteria JN-369 was isolated from the healthy rice plants of the susceptible rice cultivar Xiangzaoxian 24 by dilution plate method. And its activity against mycelial growth of M. oryzae was tested by the plate confrontation method. The strain JN-369’s taxonomic status was identified based on morphological characteristics, physiological, biochemical characteristics and 16S rDNA sequence analysis. The antifungal spectrum of strain JN-369 was determined by the dural culture method, the inhibitory effects of volatile organic compounds (VOCs), crude proteins and crude lipopeptides from strain JN-369 against M. oryzae were preliminarily determined. The results showed that the strain JN-369 was identified as Bacillus tequilensis, with the inhibition rate of 80.46% ± 0.83% against M. oryzae. It also had obvious antifungal activity against the tested fungi, such as Colletotrichum gloeosporioides, Alternaria alternata, Phytophthora melonis, and the other plant pathogenic fungi and oomycetes, while it exhibited no inhibition effect on the tested pathogenic bacteria. The volatile organic compounds produced by 1 × 10⁸ cfu/mL strain JN-369 had the strongest inhibition rate on M. oryzae with the inhibition rate of 72.92% ± 3.01%. The inhibition rate of 1.454 mg/mL protein extract and 1.026 mg/mL lipopeptide extract against M. oryzae were only 24.68% ± 0.80% and 14.34% ± 1.08%, respectively. These results showed that the strain JN-369 had potential for development and application.