Abstract
Problem statement: Application of biocontrol agents to the field in pre-existing free-cell forms often results in poor cell viability which subsequently affects their efficacy in suppressing pathogen development. There is therefore a need to bioformulate these biocontrol agents not just to enhance their field potential, but for easy storage, delivery and application as well. Approach: In this study, the bioformulations for a biocontrol bacterium Serratia marcescens, was developed using bentonite clay as carrier material with various combinations of enrichment and additive materials. The most suitable bioformulation was determined by assessing the compatibility of the formulative materials in preserving cell viability during storage, the resulting appearance of the bioformulation, the protection confered to cells upon sunlight exposure and the efficacy of the formulated cells (with and without sunlight exposure) in inhibiting the growth of the pathogenic Fusarium oxysporum F. sp. cubense race 4 (FocR4). Results: Bioformulation benefited the cells when exposed to sunlight (UV rays). The benefits of bioformulation were attributed to the carrier material (bentonite clay) and the enhancement materials (NFSM and sucrose). They confer UV-protectant effects as well as providing nutrient source for the formulated cells. The additive material PABA was observed to have antimicrobial effect on the formulated cells. Formulative materials however has no impact on the efficacy of the cells in inhibiting FocR4 as no significant differences in percentages of FocR4 inhibition were observed between bioformulations with and without exposure to sunlight. Conclusion: Present study observed that incorporation of sucrose into Bentonite (BS) has the most potential for large-scale testing as it showed good viability and efficacy results.
Highlights
The application of many biocontrol agents at the glasshouse and field stage is often hampered by the susceptibility of the viable cells to the unfavorable environmental conditions
We examined the potential of combining several formulative materials to protect the cells of Serratia marcescens, a bacterium which have showed immense potential in managing Fusarium wilt disease of bananas caused by the fungal pathogen Fusarium oxysporum F. sp. cubense race 4 (FocR4)[15,17]
Our study showed that formulative materials used in the bioformulation of S. marcescens have a significant impact in improving cell viability compared to Free-Cell suspension (FC) after sunlight exposure
Summary
The application of many biocontrol agents at the glasshouse and field stage is often hampered by the susceptibility of the viable cells to the unfavorable environmental conditions. To ensure that the biocontrol agents remain viable when introduced into the soil, they must be protected from these unfavorable conditions which may diminish their viability and subsequently affect their efficacy towards the pathogens One such approach to ensure the viability of cells is to formulate the viable cells using suitable formulative materials[4]. The carrier materials and enrichment materials are aimed to protect the active cells from temperature changes and desiccation[18,19], while PABA has a protective role against intense UV rays from the sunlight[19] Their combination is expected to permit the retention of cell viability[4] increasing the effectiveness of the active material[18]. Formulated cells of S. marcescens were tested for their efficacy in reducing the inoculum of FocR4 in a laboratory-scale testing and the results reported in this paper
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More From: American Journal of Agricultural and Biological Sciences
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