Biological control of the rice root-knot nematode Meloidogyne graminicola on rice, using endophytic and rhizosphere fungi

We investigated the antagonistic activities of endophytic and rhizosphere fungi, isolated from three different rice cropping areas in Vietnam, against the rice root-knot nematode Meloidogyne graminicola. Amongst the three types of soils (alluvial, acid sulphate and gleyic acrisol), the alluvial soils contained the highest number of fungal strains that were able endophytically to colonise rice roots, and also showed a high biological control potential against the rice root-knot nematode. The gleyic acrisol contained fewer fungi with intermediate biological control levels while the acid sulphate soil hosted the lowest number of endophytic fungi. By inoculating roots of rice seedlings with conidia of endophytic and rhizosphere Fusarium isolates, root-galling severity was reduced by 29-42% and root weight was increased by up to 33%. Trichoderma species, which were recovered only from the rhizosphere of the rice plants grown in the three sampled soils, showed similar biological control effects on nematode galling and on plant growth by reducing galling severity by up to 38%. We conclude that Fusarium and Trichoderma isolates are potential biological control agents against M. graminicola in rice in that fungal treatments reduced root-knot levels significantly and that depending on initial nematode density in the soil, these reductions would have an economic impact on rice production.