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Published on: April 11, 2013
A Novel Neotropical Bacillus siamensis Strain Inhibits Soil-Borne Plant Pathogens and Promotes Soybean Growth
Rodrigo F Moreira1, Elizabeth B E Pires1, Odaiza F Sousa1
1Programa de Pós-graduação em Biotecnologia, Universidade Federal do Tocantins (UFT), Gurupi 77402-970, TO, Brazil.
Abstract:
Soil-borne fungal pathogens such as Sclerotium spp., Rhizoctonia spp., and Macrophomina spp. pose significant threats to global agriculture, with soybean crops among the most severely affected due to damping-off disease. These pathogens cause substantial yield losses, making their management a critical concern. In this study, we investigated the potential of Bacillus siamensis BCL, a novel Neotropical strain, as an eco-friendly solution for managing Sclerotium, Rhizoctonia, and Macrophomina species. The strain exhibited strong antifungal activity, significantly inhibiting fungal growth in vitro, with the greatest suppression observed against Macrophomina spp., reaching up to 81%. In vivo assays further confirmed the biocontrol potential of B. siamensis. When applied at 106 colony-forming units (CFU)/mL, the strain reduced disease symptoms and improved plant growth parameters-including root length, shoot biomass, and leaf number-compared to untreated, infected controls. The protective effect varied by pathogen, with the most significant recovery in root length observed against Macrophomina spp. (85%) and Sclerotium spp. (78%). In preventive treatments, fermentation extracts of the B. siamensis strain suppressed disease progression, although they did not promote seedling growth. A genomic analysis of B. siamensis BCL revealed genes encoding antimicrobial secondary metabolites, including terpenes, fengycins, and surfactins. These findings highlight B. siamensis BCL as a promising candidate for sustainable crop protection and a valuable resource for developing novel antimicrobial strategies in agriculture.
Insights
A novel strain of Bacillus siamensis BCL shows potent antifungal activity against soil-borne pathogens like Sclerotium, Rhizoctonia, and Macrophomina. This eco-friendly biocontrol agent effectively reduces disease and enhances soybean growth, offering a sustainable agricultural solution.
Area of Science:
- Agricultural Science
- Microbiology
- Plant Pathology
Background:
- Soil-borne fungal pathogens (Sclerotium, Rhizoctonia, Macrophomina spp.) cause significant crop losses, particularly damping-off disease in soybeans.
- Effective and sustainable management strategies are critical for global agriculture to mitigate yield reductions.
Purpose of the Study:
- To evaluate the biocontrol potential of a novel Neotropical strain, Bacillus siamensis BCL, against key soil-borne fungal pathogens.
- To assess the efficacy of B. siamensis BCL in managing Sclerotium, Rhizoctonia, and Macrophomina species in soybean crops.
Main Methods:
- In vitro antifungal activity assays were performed to determine growth inhibition of target fungi.
- In vivo biocontrol efficacy was tested using soybean plants, assessing disease severity and growth parameters.
- Genomic analysis was conducted to identify genes responsible for antimicrobial compound production.
Main Results:
- Bacillus siamensis BCL demonstrated significant in vitro inhibition of fungal growth, with up to 81% suppression against Macrophomina spp.
- In vivo application of B. siamensis BCL (10^6 CFU/mL) reduced disease symptoms and improved soybean growth (root length, shoot biomass, leaf number).
- Protective effects were pathogen-dependent, with notable root length recovery against Macrophomina spp. (85%) and Sclerotium spp. (78%).
Conclusions:
- Bacillus siamensis BCL is a promising eco-friendly biocontrol agent for managing destructive soil-borne fungal pathogens in agriculture.
- The strain's genomic potential for producing antimicrobial secondary metabolites (terpenes, fengycins, surfactins) supports its biocontrol capabilities.
- This research highlights B. siamensis BCL as a valuable resource for developing sustainable crop protection strategies and novel antimicrobial solutions.
