Antagonism against forest pathogens and stability of fermentation broth of Burkholderia multivorans WS-FJ9

Abstract:

[Background] Some Burkholderia are important plant rhizosphere growth-promoting bacteria, which can inhibit plant pathogens and promote plant growth. [Objective] This study is to investigate the antagonistic ability of phosphate solubilizing and growth-promoting bacteria B. multivorans WS-FJ9 against different forest pathogens. [Methods] The antagonistic effect of WS-FJ9 strain against five forest pathogenics, the changes of mycelial contents of pathogenic fungi and oomycetes treated by strain WS-FJ9, the prediction of secondary metabolites and the antagonistic activity and stability of the fermentation broth were studied by using dual culture, colorimetric method, antiSMASH 5.0 online prediction site and mycelium growth inhibition rate method, respectively. [Results] The strain WS-FJ9 had different inhibitory effects against the five forest pathogens, in which the suspension had the best inhibitory effect against Phytophthora cinnamomi with the inhibitory zone width up to 14.82±0.20 mm. The fermentation broth of WS-FJ9 had significant inhibitory effect against Phomopsis macrospore and Sphaeropsis sapinea, and the inhibition rates were 62.22% and 62.78%, respectively. The contents of malondialdehyde (MDA), reducing sugar and soluble protein in the mycelia of pathogenic bacteria were increased after the treatment of sterile fermentation filtrate. The genome of the WS-FJ9 strain contained 27 different gene clusters encoding secondary metabolites, including genes encoding siderophores, bacteriocins and antibiotics. The antifungal activity of the fermentation broth of the strain was not affected under high temperature, ultraviolet irradiation, protease treatment, extreme acid and alkali treatment. [Conclusion] B. multivorans WS-FJ9 could be potentially used as biocontrol agent against forest pathogens.