Screening Biocontrol Agents for Cash Crop Fusarium Wilt Based on Fusaric Acid Tolerance and Antagonistic Activity against Fusarium oxysporum

Development and Utilization of Quantitative Detection for Probiotics Bacillus velezensis B31 with Potential Protection Against Tomato Fusarium Wilt

The biocontrol efficacy of probiotics Bacillus velezensis B31 against fusarium wilt is contingent upon its successful colonization in the plant rhizosphere. This study aimed to develop a quantitative detection method for probiotics strain B31 and to monitor its rhizosphere dynamics. Utilizing comparative genomics, a specific gene in strain B31 was identified, which facilitated the design of precise primers and a Taqman probe. The resulting real-time PCR assay demonstrated high specificity to strain B31 and high sensitivity with detection limit of 28 copies/µL of the genome. Comparative analysis with regular PCR methods revealed a strong correlation, yet highlighted the superior sensitivity and rapidity of the real-time PCR technique. The temporal colonization profile of strain B31, post root-inoculation, was charted using this assay. An initial rhizosphere population of 7.2 × 107 CFU g-1 was observed, which then tapered to 105 CFU g-1 over 14 days. These dynamics corresponded with the observed control effect, where a higher initial population correlated with enhanced disease suppression. This study underscores the potential of real-time PCR as a robust tool for biocontrol agents' monitoring, offering insights into the microbial interactions within the rhizosphere.

Mechanism of a novel Bacillus subtilis JNF2 in suppressing Fusarium oxysporum f. sp. cucumerium and enhancing cucumber growth

Cucumber Fusarium wilt caused by Fusarium oxysporum f. sp. cucumerium (FOC), is a prevalent soil-borne disease. In this study, Bacillus subtilis JNF2, isolated from the high incidence area of cucumber Fusarium wilt in Luoyang, demonstrated significant inhibitory effects on FOC and promoted cucumber seedling growth. The biocontrol mechanism of strain JNF2 were elucidated through morphological observation, physiological and biochemical experiments, and whole genome sequence analysis. Pot experiments revealed an 81.33 ± 0.21% control efficacy against Fusarium wilt, surpassing the 64.10 ± 0.06% efficacy of hymexazol. Seedlings inoculated with JNF2 exhibited enhanced stem thickness and leaf area compared to control and hymexazol-treated plants. Physiological tests confirmed JNF2's production of indole-3-acetic acid (IAA), siderophores, and hydrolytic enzymes, such as β-1,3-glucanase, amylase, and protease, which inhibited FOC growth and promoted plant development. Genome analysis identified genes encoding antimicrobial peptides and hydrolases, as well as a novel glycocin synthetic gene cluster. These findings underscore B. subtilis JNF2's potential as a biocontrol agent for sustainable cucumber cultivation.

Complete genome sequence of Bacillus velezensis B31, a potential biocontrol agent with ability of tolerance to fusaric acid and antagonism against Fusarium oxysporum

Bacillus velezensis B31 is tolerant to fusaric acid, exhibits antagonism against Fusarium oxysporum, and has an excellent control effect on tomato fusarium wilt. Here, we present the complete genome sequence of B31, which contains 4,056,755 bp DNA with a G + C ratio of 46.39%. The genome has 3,838 protein-coding genes.