Antagonistic activities of mycoparasitic Pythium species against Fusarium oxysporum f. sp. lycopersici and Botrytis cinerea on tomatoes

Abstract

In this study, antagonistic effects of Pythium acanthophoron, P. lycopersicum, P. oligandrum and P. paroecandrum against Fusarium oxysporum f. sp. lycopersici and Botrytis cinerea were investigated by in vitro and in vivo trials. In vitro mycoparasitic activities of Pythium species were determined by dual culture, inverted plate culture and agar diffusion tests. As a result of dual culture tests, suppressive effects of all mycoparasites were over 70% against mycelial growth of the pathogens. Inverted plate tests showed that antagonistic effects of mycoparasites regarding their volatile compounds were rather low. In the agar diffusion test, all mycoparasites showed antibiosis effect, however P. lycopersicum had the highest suppressive effect on both pathogens. In pot trials, mycoparasites were effective to protect tomato seedlings when pathogens were seperately inoculated, and suppressed the symptoms. When two pathogens were inoculated together, P. paroecandrum was ineffective against B. cinerea, but decreased the severity of wilt symptoms, while other mycoparasites totally inhibited both diseases. Chromatographic analyses made by using leaf samples taken 12, 24, 48 and 72 hours after pathogen inoculation showed meaningful increase on chlorogenic acid, caffeic acid and epicatechine, in the samples taken 48 hours after inoculation. Analyses after the inoculations of tomatoes with the mycoparasites and/or pathogens showed that mycoparasites also caused increase in the amounts of phenolics. This indicated that the mycoparasites could be effective to induce defense mechanisms of tomato plants against pathogens. Among them, P. oligandrum can be mentioned as the most effective mycoparasite regarding the induction of phenolics.