Results clarify the ecological strategy underlying the recruitment of beneficial B. velezensis in the rhizosphere of maize to resist F. oxysporum invasion and elucidate the specific antimicrobial mechanism of Bacillus, providing an important foundation for future green prevention and control of soil-borne pathogens.
Abstract
Microorganisms of the crop rhizosphere are essential for maintaining crop health. Corn root rot (CRR) caused by Fusarium oxysporum is a severe disease that affects global maize yield and food security. Maize recruits beneficial rhizosphere microorganisms to resist F. oxysporum; however, the mechanism underlying this recruitment remains poorly understood. Here, we performed multi-omics analyses and experimental validation to investigate the microbial community in F. oxysporum-invaded maize roots. Maize-enriched Bacillus velezensis in the rhizosphere alleviated pathogenic stress by inhibiting F. oxysporum growth primarily through the direct production of antimicrobial metabolites that disrupted the pathogen's cellular structure. We elucidated the antimicrobial mechanism of the cell-free supernatant (CFS) by performing multi-omics analyses and validation. As CFS treatment duration increased, the pathogenic metabolic disorder intensified, and metabolic homeostasis of the genetic material showed increased disruption owing to interference of RNA processing and transcription. Additionally, the expression of pathogenicity-related genes NR1, STUA, and FOW was significantly downregulated. The key antimicrobial components comprised non-volatile metabolites (NVMs) of the benzenoid class (e.g., 4-Hydroxybenzaldehyde) and volatile metabolites (VOCs) of the alcohol and ketone classes (e.g., 5-methyl-2-heptanol) in the CFS. All compounds exhibited broad-spectrum antimicrobial activity. Thus, these results clarify the ecological strategy underlying the recruitment of beneficial B. velezensis in the rhizosphere of maize to resist F. oxysporum invasion, and they elucidate the specific antimicrobial mechanism of Bacillus. Notably, these findings provide an important foundation for future green prevention and control of soil-borne pathogens.
Durum wheat is highly susceptible to Fusarium head blight (FHB) caused by the fungal pathogen Fusarium graminearum. Wheat can be protected with the use of environmentally-friendly and sustainable methods involving biological control agents (BCAs) such as yeasts. However, the mechanism underlying the antagonistic effects of yeasts on plant pathogens has not been fully elucidated. Therefore, the aim of this study was to expand the existing knowledge about the mechanisms of action of a Debaryomyces hansenii biopreparation through transcriptome profiling in F. graminearum cells using RNA sequencing (RNA-seq). The changes in the F. graminearum transcriptome resulting from biotic stress induced by the application of D. hansenii cells to durum wheat spikes, and abiotic stress induced by the application of a cell-free supernatant were compared and comprehensively analyzed. Each stressor elicited a completely different transcriptomic response, and differentially expressed genes (DEGs) encoding metabolic pathways essential for pathogen development associated with carbohydrate and amino acid metabolism, pathogenicity factors, effectors, and secondary metabolites. Numerous transporter genes were also identified, which indicates that fungi exhibit complex responses to biotic and abiotic stresses. The study demonstrated that F. graminearum uses various strategies to overcome the biotic stress associated with BCAs, including the upregulation of the brefeldin A resistance gene (FGSG_02870), which encodes an antifungal compound that inhibits the growth of BCA cells. The present findings provide novel insights into the interactions between pathogens and BCAs with specific mechanisms of action at the transcriptome level, thus helping to explain the relative ineffectiveness of BCAs under certain conditions.
Weronika Giedrojć, W. Pluskota, U. Wachowska· Fungal Genetics and Biology· 0 citations
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
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.
L. T. Nguyen, A. Park, H. Le et al.· Plant Pathology Journal· 0 citations
It is indicated that healthy tobacco roots harbor disease-suppressive endophytic microorganisms and suggested that TM-1 may suppress F. solani by interfering with sugar transport and carbon acquisition and provide a potential biocontrol resource for the sustainable management of tobacco root rot.
Tian-Miao Li, Xiao-Yu Zhou, Fei Xiong et al.· Frontiers in Microbiology· 0 citations
