Biocontrol of Fusarium oxysporum f.sp. cubense tropical race 4 by formulated cells and cell-free extracts of Streptomyces griseus in sterile soil environment

Abstract

The biocontrol activities of cells and cell-free extracts of Streptomyces griseus was tested against Fusarium oxysporum f.sp. cubense tropical race 4 (FOC race 4) in a sterile soil environment. They were first formulated in sodium alginate, kaolin clay and in alginate–kaolin combination, prior to introducing into sterile soil inoculated with 6 log₁₀ cfu FOC race 4 g⁻¹ soil. Results revealed that bioformulated cells of S. griseus, irrespective of the materials used, were generally more effective in inhibiting growth of FOC race 4 when compared to non-formulated cells of S. griseus. Kaolin was the most suitable inert material as formulation of S. griseus with kaolin effectively suppressed FOC race 4, with only 5.40 log₁₀ cfu g⁻¹ of FOC race 4 recovered after 20 days. Kaolin formulations also allowed good cell recovery post-formulation. Alginate was less desirable as poorer control was demonstrated, with 6.12 and 6.16 log₁₀ cfu g⁻¹ of FOC race 4 recovered from soils treated with alginate only and alginate–kaolin formulated S. griseus, respectively. Bioformulations did not benefit cell-free extracts at all. Our study suggests formulation of cells of S. griseus is more beneficial than cell-free extracts and kaolin is the preferred material for formulation.

Keywords:

• alginate
• biocontrol
• formulation
• Fusarium oxysporum f.sp. cubense tropical race 4
• kaolin
• Streptomyces griseus

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by Monash University Malaysia.