Efficacy of plant extracts against the rice blast fungus Magnaporthe oryzae

Rice blast disease caused by Magnaporthe oryzae is the most destructive fungal disease affecting rice production. Overcoming fungicide-resistance to M. oryzae is critical for chemical control. Accordingly, in this study, the fungicidal activity of extracts of Houttuynia cordata and Artemisia indica against rice blast caused by M. oryzae was evaluated for new fungicide development. When spores of M. oryzae were suspended in an extract of H. cordata or A. indica and transferred onto glass slides, spore germination and appressorium formation of M. oryzae were significantly inhibited. Furthermore, blast lesion formation by M. oryzae was significantly inhibited in the presence of both extracts, compared to distilled water. These results suggest that antifungal substance（s） effective against rice blast fungus M. oryzae are contained in extracts of H. cordata and A. indica. Thus, extracts of H. cordata and A. indica may be candidate control agents for plant protection against diseases such as rice blast disease.