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

The response of the resistant wheat Aegilops ventricosa introgression line H93-8 to a spanish population of the cereal cyst nematode Heterodera avenae was studied to determine changes in gene expression correlated with resistance. Roots of susceptible (Triticum aestivum cv Anza) and resistant wheat seedlings were analysed using hstological (electron microscopy), cytochemical (at tissue and cytological level) and biochemical (isoelectrofocusing) techniques. Infection of resistant wheat lines resulted in a hypersensitive reaction, with syncitial cells deteriorating in a few days. Following nematode infection, peroxidase, esterase and superoxide dismutase activities were increased in H-93-8 roots compared with susceptible wheat. Syncitial 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 syncitial cells showed early positive reaction to phloroglucinol, indicating lignification. The cre-2 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.