Volatiles from the endophytic bacteria Bacillus sp. T6 confer Verticillium resistance in cotton

Abstract [Aims] To obtain the endophytic bacteria with Verticillium wilt-resistance and explore the interactions between soil and plants. [Methods] Active tracking screening experiments were used to isolate the target strains. Morphological examination and 16s rRNA sequence analysis were performed to identify the strain. GC-mass spectrometry was used to explore the inhibition factor. Transcriptome analysis was carried out to explore the potential genes. Molecular docking and qRT PCR were used to validate the gene function. [Results] An endophytic bacterium Bacillus sp. T6 was obtained from the Verticillium wilt-resistant cotton Gossypium barbadense ‘Xinhai15’. The strain possessed strong antagonistic abilities that inhibited V. dahliae spore germination and mycelial growth without contact, and thus, it was speculated that the active factor of the bacteria might be volatile compounds. A total of 46 volatile substances were detected. The styrene produced by the T6 strain was the main virulence factor. Following styrene induction, 247 genes in V. dahliae, including genes of four hydrolase, eight dehydrogenase, 11 reductase, and 17 genes related to transport and transfer were upregulated. Additionally, 72 genes, including two chitinase, two protease, five transport-related, and 33 hypothetical protein genes, were downregulated. The expression of the four genes VDAG_02838, VDAG_09554, VDAG_045572, and VDAG_08251 was increased by 3.18, 78.83, 2.71, and 2.92 times, respectively, compared with the uninduced control group. [Conclusions] The research provides a new reference for the development and application of the volatile compounds of endophytic bacteria as new biocontrol agents for the control of Verticillium wilt and as biological preservatives for agricultural products.