Aug 2026· Plant Pathology Journal· 0 citations· 45 references
Medicine
TL;DR
Overall, Streptomyces virginiae JCK-8401 is a highly promising, multifunctional biocontrol agent for managing soil-borne diseases through a synergistic combination of antibiosis, bioinoculation, and the induction of host plant defense responses.
Abstract
Bacterial wilt caused by Ralstonia solanacearum is a destructive soil-borne disease affecting numerous crops worldwide. Although synthetic pesticides and antibiotics are commonly used for disease management, their excessive application has raised concerns regarding environmental pollution, human health risks, and the emergence of antibiotic-resistant pathogens. As a sustainable alternative, rhizosphere microorganisms have gained attention as potential biocontrol agents. In our previous study, strain JCK-8401 exhibited strong antibacterial activity against R. solanacearum. In the present study, its biocontrol potential was comprehensively characterized through analyses of physiological and biochemical traits, antagonistic activity against phytopathogens, induction of salicylic acid (SA)-mediated defense responses using Arabidopsis thaliana PR1::GUS reporter line, and in vivo suppression of tomato bacterial wilt. Based on 16S rRNA sequence analysis, JCK-8401 was identified as Streptomyces virginiae. The strain utilized diverse carbon sources and produced hydrolytic enzymes and indole-3-acetic acid. Furthermore, it exhibited antibacterial activity against various phytopathogenic bacteria and oomycetes, though it lacked antifungal activity. Both cell suspension and culture filtrate of the strain induced GUS expression, indicating activation of the SA-mediated defense pathway. In vivo assay demonstrated that seed treatment with JCK-8401 achieved 96.40% control efficacy against tomato bacterial wilt. Additionally, pretreatment with diluted culture filtrates (250-, 500-, and 1000-fold) effectively suppressed disease incidence regardless of the application method, strongly suggesting the activation of induced systemic resistance. Overall, Streptomyces virginiae JCK-8401 is a highly promising, multifunctional biocontrol agent for managing soil-borne diseases through a synergistic combination of antibiosis, bioinoculation, and the induction of host plant defense responses.
Pathogenic strains of Fusarium oxysporum are major soilborne fungal pathogens responsible for Fusarium wilt in tomato, leading to significant yield losses worldwide. This study evaluated the biocontrol potential of rhizospheric bacterial isolates from argan (Argania spinosa) and raspberry (Rubus idaeus) soils through an integrated approach combining in vitro screening, greenhouse validation, and phylogenetic analysis. A total of 27 bacterial isolates were screened for antifungal activity using dual culture assays, of which ten exhibited more than 50% inhibition of fungal growth. Selected isolates were further evaluated for volatile organic compound (VOC)-mediated inhibition. Despite strong in vitro performance for several isolates, greenhouse experiments revealed that antifungal activity in vitro was not a reliable predictor of in planta efficacy. Among the tested isolates, BSA25, BSA23, and BSF8 significantly reduced disease severity and incidence under greenhouse conditions, with BSA25 achieving the greatest suppression. In addition to disease control, certain isolates promoted plant growth under pathogen stress, indicating dual functionality as plant growth-promoting rhizobacteria (PGPR). Molecular identification based on 16S rRNA gene sequencing and phylogenetic analysis (Neighbor-Joining, Kimura 2-parameter) revealed that the isolates belong to PGPR-associated genera, including Bacillus and Pseudomonas, while also highlighting functional variability among closely related taxa. Overall, this study demonstrates that multi-trait evaluation, integrating mechanistic screening and in planta validation, provides a more reliable framework for selecting effective biocontrol agents. The identified isolates, particularly BSA25, represent promising candidates for further evaluation for sustainable management of Fusarium wilt in tomato production systems.
Safouane Benjaa, R. Bouharroud, S. Chafiki et al.· International Journal of Pla...· 0 citations
Bacterial and fungal diseases cause significant losses in horticultural crops, and biocontrol using beneficial microorganisms offers a sustainable alternative to chemical pesticides. In this study, a novel Pseudomonas strain D3 was isolated from Actinidiae rhizosphere. D3 exhibited strong antibacterial activity in LB medium but showed no activity against fungi or oomycetes. However, when cultured in KIDO medium, it demonstrated potent antifungal activity. Phylogenetic analysis based on 16S rRNA gene showed that D3 was most closely related to Pseudomonas mosselii CIP_105259T, while whole-genome sequencing revealed ANI values below 95% with eight known P. mosselii strains. Digital DNA-DNA hybridization (dDDH) further confirmed its genomic distinctiveness, with the highest dDDH value (58.2%) against the type strain P. mosselii DSM 17497T, well below the 70% species delineation threshold, supporting D3 as a novel Pseudomonas species. Functional validation via targeted gene knockout revealed a dichotomy in the antagonistic mechanisms of D3. Knockout of individual biosynthetic gene clusters (BGCs) only partially reduced antibacterial activity against Pseudomonas syringae pv. actinidiae, indicating that multiple BGCs contribute to this activity in a partially redundant manner. In contrast, disruption of a specific lipopeptide synthase cluster completely abolished antifungal activity against Valsa mali. LC-MS/MS analysis confirmed that this lipopeptide was produced exclusively in KIDO medium, consistent with the observed medium-dependent antifungal activity. Detached leaf and twig assays showed that D3 provides strong preventive biocontrol against both pathogens. Collectively, strain D3 employs a dual biocontrol mechanism, combining antibacterial activity mediated by multiple BGCs with lipopeptide-dependent antifungal activity, positioning it as a promising agent for sustainable disease management in horticultural crops.
Ming-Ming Yang, Guang-Zhe Li, Yun-Cong Wang et al.· Pesticide Biochemistry and P...· 0 citations
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.
Pronounced cultivar × treatment interactions confirmed that PGPR efficacy is modulated by host genetic background, with resistant varieties carrying pyramided Xa resistance genes showing additive responses to biological treatment.
S. Naqvi, Ateeq ur Rehman, Ummad ud Din Umar· World Journal of Microbiolog...· 0 citations
Indigenous rhizospheric Streptomyces possess complementary plant growth-promoting and biocontrol characteristics that support their use as multifunctional bioinoculants.
