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. 2022 Jun 9:13:885430.
doi: 10.3389/fmicb.2022.885430. eCollection 2022.

Evaluation and Genome Analysis of Bacillus subtilis YB-04 as a Potential Biocontrol Agent Against Fusarium Wilt and Growth Promotion Agent of Cucumber

Wen Xu  1 , Qian Yang  1   2 , Fan Yang  3 , Xia Xie  1 , Paul H Goodwin  4 , Xiaoxu Deng  1 , Baoming Tian  2 , Lirong Yang  1
Affiliations

Evaluation and Genome Analysis of Bacillus subtilis YB-04 as a Potential Biocontrol Agent Against Fusarium Wilt and Growth Promotion Agent of Cucumber

Wen Xu et al. Front Microbiol. .

Abstract

Cucumber wilt caused by Fusarium oxysporum f.sp. cucumerinum (Foc) is a highly destructive disease that leads to reduced yield in cucumbers. In this study, strain YB-04 was isolated from wheat straw and identified as Bacillus subtilis. It displayed strong antagonistic activity against F. oxysporum f.sp. cucumerinum in dual culture and exhibited significant biocontrol of cucumber Fusarium wilt with a higher control effect than those of previously reported Bacillus strains and displayed pronounced growth promotion of cucumber seedlings. B. subtilis YB-04 could secrete extracellular protease, amylase, cellulose, and β-1,3-glucanase and be able to produce siderophores and indole acetic acid. Inoculation with B. subtilis YB-04 or Foc increased cucumber defense-related enzyme activities for PPO, SOD, CAT, PAL, and LOX. However, the greatest increase was with the combination of B. subtilis YB-04 and Foc. Sequencing the genome of B. subtilis YB-04 showed that it had genes for the biosynthesis of various secondary metabolites, carbohydrate-active enzymes, and assimilation of nitrogen, phosphorous, and potassium. B. subtilis YB-04 appears to be a promising biological control agent against the Fusarium wilt of cucumber and promotes cucumber growth by genomic, physiological, and phenotypic analysis.

Keywords: Bacillus subitilis; Fusarium oxysporum f.sp. cucumerinum; biocontrol agent; genome sequencing and assembly; growth promotion.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

FIGURE 1
FIGURE 1
Colony morphology of Foc co-cultivated with or without strain YB-04. (A) Colony morphology of Foc in PDA; (B) inhibition of strain YB-04 on Foc growth.
FIGURE 2
FIGURE 2
Effect of strain YB-04 against Fusarium wilt and on growth-promotion of Cucumber Seedlings. (A) Only Foc inoculation; (B) Foc inoculation and hymexazol treatment; (C) inoculation of strain YB-04 and Foc; (D) sterile distilled water; (E) only strain YB-04 inoculation.
FIGURE 3
FIGURE 3
Antifungal and PGP traits of strain YB-04. (A) Protease production; (B) amylase production; (C) cellulose production; (D) β-1,3-glucanase production; (E) siderophore production; (F) IAA production.
FIGURE 4
FIGURE 4
Map of the strain YB-04 genome. The distributions of circles from outwards to inwards are as follows: ring 1 for genome size (black line); ring 2 for the restriction modification system, for forward strand (red) and reverse strand (blue); ring 3 for COG classifications of protein-coding genes on the forward strand and reverse strand; ring 4 for the distribution of tRNAs (brown) and rRNAs (green); ring 5 for GC skew; ring 6 for GC content.
FIGURE 5
FIGURE 5
Phylogenetic tree of B. subtilis YB-04 and 10 other Bacillus species based on 16S rRNA sequences.
FIGURE 6
FIGURE 6
ANI analysis of B. subtilis YB-04 and 10 other Bacillus species.
FIGURE 7
FIGURE 7
Distribution of CAZy families in the genome of B. subtilis YB-04.
See this image and copyright information in PMC

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