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Results provide novel insights into the molecular mechanisms underlying microbial interactions in the tomato rhizosphere and highlight the potential of P. chlororaphis ToZa7 for effective biological control of FORL.
Verticillium dahliae is a destructive soil-borne fungus with a broad host range, and its persistence in soil complicates control. Current measures, mainly resistant cultivars and chemicals, are limited and environmentally risky, promoting biocontrol as a green alternative. Here, we investigated the biocontrol mechanisms of Bacillus velezensis L33a against V. dahliae JR2 in tomato. In vitro assays on PDA plates at 26°C for 9 d showed that L33a inhibited JR2 by 58.6%, caused hyphal malformation and disruption, and its volatile organic compounds suppressed pathogen growth. In pot experiments, tomato roots dipped in JR2 suspension (1 ×10⁶ CFU/mL) for 30 min at 7 d after transplanting and grown for 21 d achieved 60.9% control efficacy. Physiological assays indicated reduced peroxidase and catalase activities, while qPCR revealed that L33a alone upregulated JA signaling (SlJAZ1, SlMYC2, SlPI II) and antioxidant (SlCAT, SlAPX) genes, with further enhancement upon JR2 co-treatment. To track their interactions, we generated GFP-labeled JR2 and RFP-labeled L33a; dual fluorescence labeling showed that L33a endophytically colonized Arabidopsis thaliana roots and competed with JR2 for the same niche, correlating with reduced pathogen colonization. Integrated metabolomic and transcriptomic analysis further revealed that L33a treatment altered pathways related to ABC transporters, amino acid metabolism, cell wall integrity, and energy metabolism in JR2, with tyrosine metabolism significantly enriched at both levels. Collectively, these findings suggest that L33a is a promising biocontrol strain for green management of tomato Verticillium wilt.
Fusarium wilt, caused by the soil-borne fungus Fusarium oxysporum f. sp. lycopersici (Fol), is a devastating disease that severely constrains tomato production worldwide. In this study, an endophytic bacterium, designated ZN-S18, was isolated from healthy tomato stems and identified as Bacillus amyloliquefaciens based on phylogenetic analyses of the 16S rRNA and rpoB genes. Dual culture assays demonstrated that ZN-S18 exhibited strong antagonistic activity against Fol and significantly inhibited fungal mycelial growth. The cell-free culture filtrate of ZN-S18 markedly suppressed Fol spore germination and mycelial growth, and the inhibitory effect on spore germination was irreversible. LC-MS analyses confirmed that ZN-S18 produces the cyclic lipopeptides surfactin and iturin A. In planta assays further demonstrated that pretreatment with ZN-S18, its culture filtrate, or the combination of surfactin and iturin A significantly reduced Fusarium wilt in tomato seedlings. Moreover, the culture filtrate disrupted fungal cell wall integrity, as indicated by the increased sensitivity of Fol to Congo red stress. Notably, the combined application of surfactin and iturin A exhibited significantly stronger antifungal activity than either compound alone under Congo red-containing conditions, suggesting a synergistic effect on fungal cell wall integrity. Collectively, these findings indicate that the endophytic strain B. amyloliquefaciens ZN-S18 is a promising biocontrol agent against tomato Fusarium wilt, primarily through the synergistic action of surfactin and iturin A. This study provides an environmentally friendly alternative to chemical fungicides and establishes a foundation for future investigations into the molecular mechanisms underlying lipopeptide-mediated antagonism.
It is reported that the methyltransferase FpLaeA is a global regulator essential for F. proliferatum pathogenicity and a target for integrated control of F. proliferatum and its associated mycotoxin risk.
Fusarium oxysporum f. sp. cucumerinum is a destructive soilborne pathogen that causes Fusarium wilt in cucumbers. This study evaluated the antagonistic activity of the endophytic fungus Trichoderma viride TVa199 against F. oxysporum f. sp. cucumerinum and the mechanisms underlying its suppression of fungal virulence. TVa199 exhibited strong activity against F. oxysporum f. sp. cucumerinum, achieving 96.03 % inhibition in a dual culture assay. The culture filtrate, ethyl acetate, and methanol extracts of T. viride effectively inhibited mycelial growth, spore germination, and germ tube elongation of F. oxysporum f. sp. cucumerinum. The ethyl acetate extract caused severe damage to the morphology and ultrastructure of the hyphae and conidia of the pathogen, as evidenced by SEM and TEM observations. GC-MS analysis identified various bioactive secondary metabolites. Molecular docking predicted strong interactions between representative metabolites and virulence-associated proteins, including Avr2, M36 metalloprotease, and feruloyl esterase C. In the greenhouse experiments, the incidence of Fusarium wilt was reduced by 89.9 %, with a control efficacy of 87.5 % following the application of T. viride culture filtrate at 80 %. It also enhanced host defense by increasing phenolic content and defense-related enzyme activities while reducing oxidative stress markers. These results demonstrate that T. viride TVa199 suppresses F. oxysporum f. sp. cucumerinum via a multi-target mechanism involving direct microbial antagonism, disruption of fungal cellular integrity, and metabolite-mediated interference with virulence-associated proteins. This study provides mechanistic evidence that fungal secondary metabolites contribute to the suppression of pathogen virulence. These findings expand the current understanding of microbial antagonism beyond conventional growth inhibition and support the development of sustainable biocontrol strategies against Fusarium wilt.
Coptotermes formosanus, a worldwide pest, inflicts large losses on agriculture, forestry, construction, and other industries. As efficient, environmentally friendly pest control methods, microbial biopesticides are widely used to manage major pests. We previously isolated an Akanthomyces lecanii strain with strong insecticidal activity against termites. However, the interaction between the biocontrol agent and termites is still unknown. In this study, PacBio single-molecule real-time (SMRT) sequencing technology and Illumina RNA-seq sequencing technology were used to explore the transcriptomic differences in C. formosanus before and after A. lecanii infection. A total of 7,882,407 full-length transcripts were obtained. Single genes were further annotated using the NR, GO, KEGG, COG/KOG, Swiss-Prot, and KEGG homology public databases. A total of 2,782 differentially expressed genes were identified, including 1,440 upregulated genes and 1,342 downregulated genes. The expression of the Toll signaling pathway, mitogen-activated protein kinase (MAPK) pathway, detoxification metabolism, and immune-related genes, including scavenger receptor, apolipophorin, Cdc42, Integrin, Toll, serine protease, and transferrin genes, may be related to A. lecanii infection. This work not only greatly enriches the gene annotation resources of C. formosanus but also provides a new perspective for understanding the fungal immune defense mechanisms of social insects at the molecular level. These findings provide a theoretical basis for the development of new immunosuppressive agents.
The potential of P1 as a promising bioinoculant candidate for sustainable agriculture in the potato sector is demonstrated and the genome lacked major virulence factors and antimicrobial traits, supporting the non-pathogenic nature of the P1 strain.
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