Identification of Bacillus velezensis SBB and Its Antifungal Effects against Verticillium dahliae

Abstract

Traditional control methods have drawbacks in controlling Verticillium wilt diseases caused by Verticillium dahliae Kleb.; therefore, an efficient and environmentally friendly strategy for disease control must be identified and the mechanisms determined. In this study, a soil-isolated strain SBB was identified as Bacillus velezensis based on 16S rRNA, gyrA, and gyrB gene sequences. In vitro, strain SBB had excellent inhibitory effects on V. dahliae, with the highest inhibition rate of 70.94%. Moreover, strain SBB inhibited production of the conidia of V. dahliae and suppressed the production of microsclerotia and melanin. Through gas chromatograph–mass spectrometer analysis, nine compounds were detected from the volatile organic compounds produced by SBB, among which 2-nonanol, 2-heptanone, 6-methyl-2-heptanone, and 2-nonanone could completely inhibit V. dahliae growth. Strain SBB produced cellulase, amylase, protease, and siderophore. During inhibitory action on V. dahliae, strain SBB showed upregulated expression of genes encoding non-volatile inhibitory metabolites, including difficidin, bacilysin, and bacillaene, at 1.923-, 1.848-, and 1.448-fold higher, respectively. Thus, our study proved that strain SBB had an efficient antagonistic effect on V. dahliae, suggesting strain SBB can be used as a potential biological control agent against Verticillium wilt.

Bacillus VOCs in the Context of Biological Control

“…T6 [ 64 ]. B. velezensis SBB VOCs (2-nonanol—0.06 μL/mL, 2-heptanone—0.3 μL/mL, 6-methyl-2-heptanone—0.3 μL/mL, and 2-nonanone—0.6 μL/mL) completely inhibited Verticillium dahliae growth in vitro and inhibited production of conidia and microsclerotia [ 80 ]. Phenylacetic acid and methylphenyl acetate produced by B. mycoides BM02 suppressed spore germination but had no effects on the hyphal growth of Fusarium oxysporum f. sp.…”

“…lactucae [ 1 ]. B. velezensis SBB VOCs (2-nonanol, 2-heptanone, 6-methyl-2-heptanone, and 2-nonanone) inhibited melanin production by Verticillium dahliae [ 80 ]. Melanin plays an important role in providing the mechanical strength required for germ tubes, obtained by conidia germination, to penetrate host tissues [ 93 ].…”

Biological control potential of worrisome wheat blast disease by the seed endophytic bacilli

“…The major gene clusters identified in the bacterial genomes include macrolactin, bacillaene, bacilysin, bacillibactin, fengycin, and iturin A ( Table 3 ; Figure 6 ). Biosynthesis and secretion of these compounds by Bacillus isolates have been shown direct mechanisms to suppress plant pathogens ( Bidima et al, 2022 ; Wang et al, 2022 ). Several studies reported that the macrolide compounds such as macrolactin, bacillaene, and difficidin inhibit protein synthesis, impair cell division, and damage the cell membrane to restrict the growth of phytopathogens ( Wu et al, 2015 ; Chen et al, 2021 ).…”

“…Moreover, recent studies suggest that these compounds also play a role in transcription regulation and enhance plant resistance against phytopathogens ( Chen et al, 2021 ; Surovy and Islam, 2021 ). Siderophores such as bacilibactin and bacilysin suppress fungal growth by competing for nutrition ( Dimopoulou et al, 2021 ; Wang et al, 2022 ).…”

Probiotic <em>Bacillus</em> Species: Promising Biological Control Agents for Managing Worrisome Wheat Blast Disease

“…Biosynthesis and secretion of all these compounds by Bacillus spp. have shown direct mechanisms to suppress plant pathogens [57,58,59]. Several studies reported that the macrolide compounds macrolactin, bacillaene, and difficidin inhibit protein synthesis, impair cell division, and damage the cell membrane to restrict growth of phytopathogens [33,60].…”