Selection of antagonists from compost to control soil-borne pathogens

One-hundred and one microorganisms have been selected and tested for their antagonistic activity towards soil-borne plant pathogens from a compost originated from urban organic and yard wastes. Among them, twenty eight microorganisms, tested under laboratory conditions on tomato seedlings growing on perlite medium in Petri plates, controlled tomato wilt caused by Fusarium oxysporum f. sp. radicis-lycopersici. In a second round of trials, they were assessed under greenhouse condition on three pathosystems: Fusarium oxysporum f.sp. basilici on basil, Phytophthora nicotianae on tomato and Rhizoctonia solani on bean. The Fusarium strain K5 showed a disease control of 69% and an increase in biomass production of basil of 32% compared to inoculated control. In the case of tomato/P. nicotianae, the bacteria strain B17 showed a disease control of 82% and an increase of 216% of biomass production of tomato. Two microorganisms, E19 and P11 controlled root and stem rot caused by R. solani on bean and increased the biomass of bean up to 163%. None of the microorganisms was able to control all the soil-borne pathogens. Three Fusarium (K7, K9 and K11) and two Trichoderma (E28 and E36) isolates showed the best results and were tested in a third round of trials mixed together and at different dosages. Two Fusarium isolates, K7 and K9, were able to control F. oxysporum f. sp. basilici and confirmed they could be used in the future as commercial antagonists.