Abstract
Among 57 species in 32 families of plants tested, root extracts from 6 species were strongly inhibitory, 4 were moderately inhibitory and 10 were weakly inhibitory to spore germination of Phytophthora palmivora. Root extract from 37 species and additional 51 unidentified plants tested were not inhibitory to P. palmivora. Root extract of garlic, the representative species of antagonistic plants selected in this study, inhibited germination of chlamydospores and encysted zoospores of P. palmivora in soil and reduced damping-off of papaya seedlings caused by this pathogen. These results indicate the possibility of finding antagonistic plants in nature which are capable of releasing antifungal substances from roots to control certain pathogens in soil.
