Enhancement of development and induction of resistance in tomato plants by the antagonist, Pythium oligandrum

To exert an optimal biological control, P. oligandrum must colonise roots and persist in the rhizosphere of plants throughout the cultural season. The present study demonstrated that, after inoculation of root system by P. oligandrum, it colonised 20 to 40% of roots of tomato plants grown in hydroponic system. Constant presence of the introduced fungus in the rhizosphere over the cultural season is correlated with an increase in tomato yield. The combination of several factors likely explains this P. oligandrum-mediated increase. Among them, one may cite mycoparasitism; however, though P. oligandrum can parasitize other pathogenic Pythium species; root colonisation by the antagonist was not associated with significant reduction in Pythium spp. populations. In the present case, the induction of plant resistance seems more prevalent. Indeed, root colonisation with P. oligandrum induced systemic resistance. Interestingly, P. oligandrum-inoculated plants triggered and amplified PR proteins synthesis only when leaves had been attacked by the pathogen, Botrytis cinerea.