Investigating the bioactivity of cells and cell-free extracts of Streptomyces griseus towards Fusarium oxysporum f. sp. cubense race 4.

摘要

The antifungal activity of viable cells of Streptomyces griseus (St 4) and its cell-free extracts were investigated against the pathogenic Fusarium oxysporum f. sp. cubense race 4 (FOC race 4), causal agent of wilt disease in bananas. Results from in vitro and soil assays showed cells and cell-free extracts of S. griseus were able to inhibit FOC race 4 with varying degree of success. Antifungal activity was attributed to chitinase and beta -1,3-glucanase, detected in both cells and cell-free extracts, which caused lysis of fungal cell wall and inhibited sporulation. Interestingly, beta -1,3-glucanase and chitinase activities were significantly higher in cell-free extracts compared to cells, with 8.30 and 5.43 against 7.96 and 4.95 U mL-1, respectively. Application to soil however, showed inoculation using S. griseus cells were more effective in suppressing growth of FOC race 4 than crude extracts, with 6 log₁₀ CFU of FOC race 4 g-1 soil enumerated compared to 7 log₁₀ CFU of FOC race 4 g-1 soil after 20 days. To summarize, this study has shown that cell-free extracts of S. griseus have antifungal properties but may not be suitable for soil application in its current form (liquid suspension). Further investigations on bioformulation may address this limitation.