Document Type : Research Paper
Authors
1 Department of Plant Protection, Faculty of Agriculture, College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran
2 Plant Protection Research Department, Khorasan Razavi Agricultural and Natural Resources Research Center, Agricultural Research, Education and Extension Organization (AREEO), Mashhad, Iran
Abstract
Keywords
Extended Abstract
Introduction
Potato is among the world's most important crops, and Fusarium wilt causes substantial annual losses. Various management strategies are employed to control the disease and mitigate its impacts. Among these, biological control using beneficial microorganisms has long attracted attention.. In recent years, the combination of Bacillus and Trichoderma has emerged as a promising approach for plant disease management, with multiple studies reporting synergistic effects from the concurrent application of these two agents. This study evaluated the effectiveness of the combined use of Bacillus velezensis strain UTB96 and Trichoderma harzianum strain T22, in comparison with their individual application, for controlling Fusarium wilt in potato.
Materials and methods
Fungal isolates FOT and Trichoderma harzianum T22 were obtained from the plant pathology collection at the Khorasan Razavi Agricultural Research Center. The bacterium Bacillus velezensis (Probio96, Biorun Co.) was cultured and purified for experimental use. Compatibility between T. harzianum and B. velezensis was evaluated via dual culture on potato dextrose agar (PDA). Antagonistic activity against the pathogen was assessed using in vitro dual culture and volatile metabolite assays, arranged in a completely randomized design with four replications. The radial growth inhibition of FOT was calculated as described below.
For greenhouse experiments, FOT inoculum was prepared on sterilized wheat and incubated for four weeks. T. harzianum T22 spore suspension (10⁶ spores/mL) was prepared in PDB, and B. velezensis UTB96 was applied as a commercial formulation (10⁸ cfu/mL). The potato cultivar Agria was planted in sterilized soil inoculated with FOT at a rate of 14 g/kg soil. Treatments included individual and combined applications of the biocontrol agents. Plants were maintained under greenhouse conditions at 24°C. At 75 days after planting, growth parameters were recorded, including plant height and fresh and dry weights of roots, stems, and leaves. Data were analyzed with SPSS, and means were compared using Duncan’s multiple range test at 1% significance.
Results and discussion
The compatibility test showed no antagonism between Bacillus velezensis UTB96 and Trichoderma harzianum T22, confirming their suitability for combined use. In dual culture assays, the B. velezensis UTB96 + T. harzianum T22 combination significantly reduced FOT mycelial growth by 77.73%, greater than either B. velezensis UTB96 alone (40.12%) or T. harzianum T22 alone (70.12%). Volatile metabolite assays likewise demonstrated the highest antifungal activity for the combined treatment, indicating a synergistic effect. All biological and chemical treatments significantly reduced Fusarium wilt severity in greenhouse conditions compared with the control. The combined application of B. velezensis + T. harzianum achieved the greatest disease suppression (76.75%) and improved plant growth parameters. Among individual treatments, T. harzianum T22 performed better than B. velezensis UTB96 in reducing disease severity. Significant differences (p < 0.01) were observed among treatments for plant height, and fresh and dry weights of roots, stems, and leaves.
Overall, the combined application of the biocontrol agents yielded the most favorable outcomes, reducing Fusarium wilt while simultaneously enhancing plant growth under greenhouse conditions. The results align with prior work showing that consortia of microbial biocontrol agents can outperform single organisms (synergistic effects). For example, Bacillus subtilis V26 reduced Fusarium wilt in potato under greenhouse conditions (Khedher et al., 2021). Across studies, Trichoderma harzianum has reduced disease severity by approximately 54.8%–60.8%, supporting the present findings, and has been reported to control up to 65% of disease in greenhouse settings (Bibi et al., 2024). Collectively, these findings underscore the potential of microbial agents such as T. harzianum and B. velezensis as sustainable alternatives to chemical controls. In conclusion, integrating biological agents appears to be an effective strategy for managing potato Fusarium wilt in greenhouse environments.
Conclusion
The combined application of Trichoderma harzianum and Bacillus velezensis can serve as an effective strategy for deploying biological control agents to manage Fusarium wilt of potato caused by Fusarium oxysporum f. sp. tuberosi at the field level. This combination demonstrated superior efficacy not only under greenhouse conditions but also in laboratory assays compared with individual treatments. The concurrent use of T. harzianum and B. velezensis led to increased seedling height and enhanced fresh and dry biomass relative to the control. Based on the results obtained, the combined use of T. harzianum and B. velezensis is recommended for managing Fusarium wilt in potato.
Mohsen Bahra: Software, Formal analysis, Data curation, Sampling, Extraction and Writing-original draft; Hossein Saremi: Supervision for real samples, planning, Investigation, Validation, Writing-original draft; Mojtaba Moradzadeh Eskandari: Methodology, Data curation, Investigation, Validation; Masoud Ahmadzadeh: Methodology, Formal analysis, Validation. All authors have read and approved the published version of the manuscript.
Data will be available upon request.
The authors greatly thank the Iranian Research Institute of Plant Protection (IRIPP) to provide the necessary facilities and equipment.
Not applicable.
The authors declare that they have no conflict of interest.
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