EFFECTS OF FUNGAL PARASITES ON CEREAL CYST NEMATODE (HETERODERA-AVENAE WOLL) FROM NATURALLY INFESTED SOIL - A SCANNING ELECTRON-MICROSCOPY STUDY

The effects of fungal endoparasites, attacking the eggs of the cereal cyst nematode Heterodera avenae, and details of the infection process were studied by low-temperature scanning electron microscopy. Some female nematodes, even young ones containing no eggs, were colonized by fungi. Spores and hyphae similar to those of Nematophthora gynophila were found in infected specimens. Fungi colonized both roots and nematodes. In early stages of infection, fungi developed within the female nematode between the organs, presumably using the female's body as a food source. In some immature females, the fungi appeared to have destroyed the uterus. In old females, appressoria of Verticillium spp., including V. chlamydosporium, penetrated the eggs they contained and progressively destroyed their contents until the egg shell was filled with hyphae and spores. Only rarely were second-stage juveniles within eggs infected by these fungi. Fungal infection of eggs, which arrests their development at an early stage, therefore occurs predominantly in females rather than in newly formed cysts.