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

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 28A degrees 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 beta-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 32A degrees C.