Infection of Olive Trees by Heterodera mediterranea in Orchards in Southern Spain

High infection rates of olive feeder roots and soil infestation by the cyst-forming nematode Heterodera mediterranea were found in commercial olive orchards cv. Manzanilla established in sandy soils at two localities of Sevilla Province of Andalucía, southern Spain. No disease symptoms were noted on the aboveground plant parts, but slightly distorted feeder roots and necrotic areas were observed near the infection points. Sedentary juvenile stages and adult females showed a semi-endoparasitic feeding habit. Histopathological studies of infected olive roots showed a disease response typical of cyst nematode infection of susceptible hosts. Nematode feeding induced syncytial formation involving cellular alterations in the cortex, endoder-mis, pericycle, and vascular parenchyma tissues in both cortical and endodermal root cells.