ANTIMICROBIAL ACTIVITY OF BARK-COMPOST EXTRACTS

The application of bark-compost to farmland has been reported to suppress soil-borne diseases, including Fusarium wilt. The "bacterial type" microflora of the compost has been considered to play the significant role in disease control. Using the disk-diffusion technique, we found that acetone extracts of the bark-compost possessed strong antifungal activity against Fusarium oxysporum f. sp. cucumerinum. The extracts were relatively stable against heat treatment at 100°C and the antifungal extracts were also active against Gibberella zeae. Helminthosporium sigmoideum and Glomerella cingulata, fungi of interest to plant pathologists, but they were inactive against yeasts and procaryotic organisms. There might be a parallel between this selective antimicrobial activity of the acetone extracts of the bark-compost and the formation of the "bacterial type" microflora of the compost. Furthermore, we partially purified the acetone extracts by reverse-phase HPLC and found at least 10 active antifungal peaks in the chromatogram. These antifungal agents appear to be relatively low polar lipids. © 1990.