Suppressive effects of grape marc compost on phytopathogenic oomycetes

Abstract

Suppression of soil-borne diseases of horticultural crops by compost has been attributed to the activities of antagonistic micro-organisms. A great diversity of biological control agents naturally colonize compost. This is especially true for biological control agents effective against the soil-borne 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 assays were performed with 432 microbial morphologies isolated from grape marc compost. Seven micro-organisms were selected for further bioassay with cucumber – P. aphanidermatum, and two micro-organisms for tomato – P. parasitica. Those experiments indicate that grape marc compost reduces 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 improve the suppressive effects.

Keywords:

• Disease suppressivity
• biological control
• microbial antagonisms
• Phytophthora parasitica
• Pythium aphanidermatum