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

. The response of the resistant wheat/Aegilops ventricosa introgression lin e, H-93-8, to a Spanish population of the cereal cyst nematode, Heterodera avenae, was studied in order to determine changes in gene expression correl ated with resistance. . Roots of susceptible (Triticum aestivum cv. Anza) and resistant wheat see dlings were analysed using histological (electron microscopy), cytochemical (at tissue and cytological level) and biochemical (isoelectrofocusing) tec hniques. . Infection of resistant wheat lines with H. avenae resulted in a hypersens itive reaction, with syncytial cells deteriorating in a few days. Following nematode infection, peroxidase, esterase and superoxide dismutase activiti es were increased in H-93-8 roots compared with the susceptible wheat. Sync ytial cells in roots of resistant lines were highly reactive to diaminobenz idine and homovanillic acid oxidase, the latter associated with plasma and nuclear membranes and vacuoles. The same syncytial cells showed early posit ive reaction to phloroglucinol, indicating lignification. . The Cre2 resistance gene in H-93-8 inhibited reproduction of H. avenae. P eroxidases, esterases and superoxide dismutase might represent products of genes whose expression is correlated with the resistance response to this n ematode.