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

Abstract Background: Verticillium wilt, caused by the fungus Verticillium dahliae, leads to significant losses in cotton yield worldwide. Biocontrol management is a promising way to suppress verticillium wilt. The purpose of the study is to obtain and analyze the endophytic bacteria with Verticillium wilt-resistant activities from the root of the cotton Gossypium barbadense ‘Xinhai15’ and to explore the interactions between soil and plants. Results: An endophytic bacterium Bacillus sp. T6 was obtained from the Verticillium wilt-resistant cotton Gossypium barbadense ‘Xinhai15’, which showed significant antagonistic abilities against cotton Verticillium wilt. The bioassay results showed that 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 via headspace solid-phase microextraction and gas chromatography-mass spectrometry analysis. The pure product verification experiment confirmed that the styrene produced by the TW11 strain was the main virulence factor. Transcriptome analysis showed that following styrene induction, 247 genes in V. dahliae, including four hydrolase genes, eight dehydrogenase genes, 11 reductase genes, 17 genes related to transport and transfer were upregulated. Additionally, 72 genes, including two chitinase genes, two protease genes, five transport-related genes, and 33 hypothetical protein genes, were downregulated. The quantitative real-time PCR results confirmed that 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.