Characterization of Heterodera zeae Populations from Portugal.

Three populations of the corn cyst nematode Heterodera zeae, one found in the rhizosphere of a fig tree and two infecting corn, were studied using the morphology and morphometry of cysts and second-stage juveniles, and compared with other populations. The intrapopulation and intraspecific variability are discussed. A simple and improved technique to prepare vulval cones for SEM is described. The non-specific esterase patterns of females, isolated from infected corn, were analyzed by electrophoresis in polyacrylamide gels. Two bands of esterase activity were detected. The occurrence of H. zeae is reported for the first time in Portugal and Europe.