Rhizosphere Inhibition of Cucumber Fusarium Wilt by Different Surfactinexcreting Strains of Bacillus subtilis

Abstract

Bacillus subtilis B006 strain effectively suppresses the cucumber fusarium wilt caused by Fusarium oxysporum f. sp. cucumerinum (Foc). The population dynamics of Foc, strain B006 and its surfactin over-producing mutant B841 and surfactin-deficient mutant B1020, in the rhizosphere were determined under greenhouse conditions to elucidate the importance of the lipopeptides excreted by these strains in suppressing Foc. Results showed that B. subtilis strain B006 effectively suppressed the disease in natural soil by 42.9%, five weeks after transplanting, whereas B841 and B1020 suppressed the disease by only 22.6% and 7.1%, respectively. Quantitative PCR assays showed that effective colonization of strain B006 in the rhizosphere suppressed Foc propagation by more than 10 times both in nursery substrate and in field-infected soil. Reduction of Foc population at the cucumber stems in a range of 0.96 log10 ng/g to 2.39 log10 ng/g was attained at the third and the fifth weeks of B006 treatment in nursery substrate. In field-infected soil, all three treatments with B. subtilis suppressed Foc infection, indicated by the reduction of Foc population at a range of 2.91 log10 ng/g to 3.36 log10 ng/g at the stem base, one week after transplanting. This study reveals that the suppression of fusarium wilt disease is affected by the effective colonization of the surfactin-producing B. subtilis strain in the rhizosphere. These results improved our understanding of the biocontrol mechanism of the B. subtilis strain B006 in the natural soil and facilitate its application as biocontrol agent in the field.

Biocontrol of Bacterial Fruit Blotch by Bacillus subtilis 9407 via Surfactin-Mediated Antibacterial Activity and Colonization

“…Moreover, the quantity of surfactrin produced by different Bacillus strains is different. For example, Jia et al (2015) reported that C12-, C13- and C16-surfactin are more abundant than C14- and C15-surfactin in B. subtilis B841. While, B. subtilis BS-37 usually produces C15-surfactin as the major component ( Liu et al, 2015 ).…”

Draft Genome Sequence of Bacillus velezensis B6, a Rhizobacterium That Can Control Plant Diseases

“…Through successful colonization in rhizosphere and the production of antifungal metabolites, this strain performs good biocontrol efficacy in suppressing cucumber wilt disease caused by Fusarium oxysporum and pepper root rot caused by Phytophthora capsici . In addition, B. velezensis B6 could inhibit the multiplication and delay the spread of F. oxysporum in cucumber stems ( 2 , 3 ) to suppress the disease development. However, the genes related to the biocontrol functions of B. velezensis B6 are not well known.…”

Beneficial Microbes and Basal Fertilization in Antagonism of Banana Fusarium Wilt

“…Some reports indicate that Bacillus species can effectively promote plant growth and may be a candidate for a biological control agent (BCA) [16]. Jia et al [17] reported that the colonization of B. subtilis and suppression of F. oxysporum in the rhizosphere are important for Fusarium wilt disease control. Chen et al [18] investigated two sets of bacterial samples: Bacillus licheniformis (X-1) and Bacillus methylotrophicus (Z-1) both with a strong inhibitory effect on Fusarium wilt caused by F. oxysporum f. sp.…”