Changes in wheat root enzymes correlated with resistance to cereal cyst nematodes

. The response of the resistant wheat/Aegilops ventricosa introgression line, H-93-8, to a Spanish population of the cereal cyst nematode, Heterodera avenae, was studied in order to determine changes in gene expression correlated with resistance. . Roots of susceptible (Triticum aestivum cv. Anza) and resistant wheat seedlings were analysed using histological (electron microscopy), cytochemical (at tissue and cytological level) and biochemical (isoelectrofocusing) techniques. . Infection of resistant wheat lines with H. avenae resulted in a hypersensitive reaction, with syncytial cells deteriorating in a few days. Following nematode infection, peroxidase, esterase and superoxide dismutase activities were increased in H-93-8 roots compared with the susceptible wheat. Syncytial cells in roots of resistant lines were highly reactive to diaminobenzidine and homovanillic acid oxidase, the latter associated with plasma and nuclear membranes and vacuoles. The same syncytial cells showed early positive reaction to phloroglucinol, indicating lignification. . The Cre2 resistance gene in H-93-8 inhibited reproduction of H. avenae. Peroxidases, esterases and superoxide dismutase might represent products of genes whose expression is correlated with the resistance response to this nematode.