SUPPRESSION OF SOILBORNE PATHOGENS BY COMPOST: SUPPRESSIVE EFFECTS OF GRAPE MARC COMPOST ON PHYTOPATHOGENIC OOMYCETES

Suppression of soil-borne diseases of horticultural crops by compost has been attributed to the activities of antagonistic microorganisms. A great diversity of biological control agents naturally colonize compost. This is especially true for biological control agents effective against the soilborne Oomycete pathogens. The purpose of this research was to determine the suppressive capacity of grape marc compost against Pythium aphanidermatum and Phytophthora parasitica. Antagonist in vitro assay were performed with 432 microbial morphologies isolated from grape marc compost. Seven microorganisms were selected for further bioassay with cucumber-Pythium aphanidermatum, and two microorganisms for tomato-Phytophthora parasitica. Those experiments indicate, that grape marc compost reduce the severity of Pythium dumping-off on cucumber, but do not reduce the severity of Phytophthora root rot on tomato. The enrichment of compost or vermiculite with the selected microbes for compost do not improved the suppressive effects.