Root-knot nematodes parasites of grapes.

Root-knot nematodes, especially Meloid'gyne arenaria (Neal) Chitwood, M. incognita (Kofoid & White) Chitwood, and M. javanica (Trmb) Chitwood, are severe pathogens of grapevine in most sandy soils and warm areas in the Mediterranean Basin, California, and South Africa. Conversely, M. hapla Chitwood is predominant in the cooler areas of southern Australia and Hungary, M. ethiopica Whitehead infects grapevines in Chile and M. nataliei Golden, Rose & Bird do it in Michigan. Mebidogyne-infected grapevine plants show reduced plant vigour and decline, as well as an increase in biotic and abiotic stresses. In this study, we report severe infections 2nd damage by root-knot nematodes in grapevines from southern Italy, Spain, South Africa, California, Egypt and Morocco. Studies of host-parasite relationships in naturally Meloidogyne-infected Vitis spp. showed a typically susceptible disease reaction, with permanent feeding sites induced in roots infected by M. arenaria, M. ethiopica, M. incognita and M. javanica. Galls induced by these four root-knot nematode species commonly occurred both individually and in clusters, with evident distortions of the entire root circumference. The galls varied in size though relatively small (up to two times the root diameter), and usually located along the root axis but rarely at -he root tip. Comparative histological observation of healthy and Meloidogne-infected grapepine roots showed cellular alterations in the cortex, endodermis, pericycle, and vascular parenchyma induced by nematode feeding. In permanent feeding sites, the nematode induced latge multinucleate giant cells adjacent to the vascular tissues, leading to disorganization and disruption of xylem elements and primary phloem.