Protective enzymes and genes related to the JA pathway are involved in the response to root-knot nematodes at high soil temperatures in tomatoes carrying Mi-1

Abstract

Root-knot nematodes (RKNs; Meloidogyne spp.) are obligate endoparasites that infect a large number of crop plants and cause severe yield losses. Tomato cultivars carrying the Mi-1 gene conferring root-knot nematode resistance have been widely used, but this gene loses its effectiveness at soil temperatures above 28°C. In this study, the mechanism of the loss of resistance to RKNs at high soil temperatures was examined using LA0655 (Solanum lycopersicum cv. Anahu), which contains the Mi-1 gene. It was found that high soil temperatures delayed the expression of the Mi-1 gene and reduced the activities of superoxide dismutase, peroxidase, chitinase, and β-1,3-glucanase. Although genes in the jasmonic acid (JA) pathway exhibited an obvious response at high soil temperatures, this response could not prevent the invasion of RKNs; indeed, at 30 days after inoculation with RKNs, the plants produced large numbers of root knots and egg masses at a soil temperature of 32°C.