Arbuscular mycorrhizal fungi induce systemic resistance in tomato against the sedentary nematode Meloidogyne incognita and the migratory nematode Pratylenchus penetrans

Abstract

Arbuscular mycorrhizal fungi (AMF) are able to protect plants against a range of soil-borne pathogens, but the biocontrol modes of action remain largely unknown, especially in the case of plant-parasitic nematodes. As a first step toward the elucidation of the modes of action, the interaction between the AMF Glomus mosseae and two nematode species with a different infection cycle was studied in tomato: the sedentary root-knot nematode Meloidogyne incognita and the migratory root-lesion nematode Pratylenchus penetrans. In greenhouse interaction experiments, nematode infection was investigated 8 weeks (M. incognita) or 10 weeks (P. penetrans) after nematode inoculation, in tomato roots either colonized by G. mosseae or not. The mycorrhiza-induced resistance was confirmed against both nematode species as the nematode population was significantly lower in mycorrhizal roots, with an overall reduction of 45% in the case of M. incognita and 87% for P. penetrans, although the latter nematode showed low infection numbers in tomato. In subsequently conducted split-root experiments, consisting of a two-compartment set-up, AMF were applied either locally (i.e. nematodes in the same compartment as AMF) or systemically (i.e. nematodes and AMF physically separated). The presence of AMF, either local or systemic, resulted in a significant infection reduction for both nematodes. The results show for the first time that infection by the root-knot nematode M. incognita and the root-lesion nematode P. penetrans is systemically reduced by G. mosseae.