Penetration, development and reproduction of a Harmony pathotype of Meloidogyne arenaria was studied on two resistant grape rootstocks, 10-23B and RS-3. Associated resistance mechanisms were examined microscopically. Cabernet Sauvignon was used as a susceptible control. The plants were inoculated with freshly hatched second-stage juveniles (J2). Significantly more J2 penetrated roots of Cabernet than 10-23B by 4 days after inoculation. Penetration was delayed by one week in roots of RS-3. Cabernet roots contained a greater number of nematodes coupled with faster development than that found in resistant rootstocks. Hypersensitive responses were expressed in the presence of penetrating J2 in resistant rootstocks only. This occurred along the root epidermis, among the cortical cells and along the differentiating vascular bundle. Cortical necrosis halted or delayed migration of J2 to vascular tissues and vascular necrosis prevented establishment of successful feeding sites which arrest
