The siderophore-producing bacterium, Bacillus subtilis CAS15, has a biocontrol effect on Fusarium wilt and promotes the growth of pepper

Abstract

In this study, the Chrome Azurol Sulphonate (CAS) agar plate assay for siderophores was used to screen bacteria from the rhizospheric soil of pepper in Hainan, China. As a result, Bacillus subtilis CAS15, which produced a large orange halo, was obtained. A dual-culture test showed that CAS15 strongly antagonized the growth of 15 plant fungal pathogens, with rates of inhibition ranging from 19.26 to 94.07%. Analysis of the siderophore production by the ESI-MS and DHB(G) assays showed that CAS15 produced the catecholic siderophore 2,3-dihydroxybenzoate-glycine-threonine trimeric ester bacillibactin, and that siderophore productivity was inhibited by iron. A pot culture experiment was used to study the effects of B. subtilis CAS15 on pathogen development and plant growth. CAS15 reduced the incidence of Fusarium wilt in pepper significantly, by 12.5–56.9%, which indicated that B. subtilis CAS15 induced systemic resistance to Fusarium wilt in pepper. Iron supplementation reduced this biocontrol effect. There were significant differences in plant height at 14, 21, 28 and 40 days, with treated plants growing 27.24–54.53% taller than controls. B. subtilis CAS15 also enhanced the yield of pepper by shortening the time to 50 percent flowering to 17.26 days, increasing the average fruit weight 36.92%, and increasing the average yield per plant 49.68%. This research showed that B. subtilis CAS15 has great potential for plant growth promotion and biological control.