Histopathology of Brassica oleracea var. capitata subvar. alba infected with Heterodera cruciferae Franklin, 1945 (Tylenchida: Heteroderidae)

Abstract

Anatomical changes induced by the cabbage cyst nematode (Heterodera cruciferae) have been insufficiently characterized. Here these changes were described in the root tissues of white head cabbage variety (Yalova F1) commonly grown in the Black Sea region of Turkey, where cabbage-growing areas are heavily infested. In glasshouse experiments conducted at 20 degrees C, susceptible white head cabbage seedlings were inoculated with 0 (untreated control) or 1000 juveniles/300 ml soil. Three, 6, 12, 24, 48, 72 h and 30 days after inoculations, two plants from each treatment were removed, embedded in paraffin by using microwave technique and then examined by photomicrography. Second-stage passed through the vascular system after root penetration and they started to feed as sedentary. In cross section of the roots, large cells in the cortex of infected plants were filled with moderately dense cytoplasm and the walls were heavily stained and ruptured. In longitudinal section, internal walls were perforated. Syncytia that had different degrees of vacuolization, and syncytial nuclei were hypertrophied and deeply indented. Contained conspicuous nucleoli were noticeable 24 h after inoculation. Syncytia originating from endodermal cells possessed ruptured walls around the feeding site of the developing juvenile. White females were observed on the roots 30 days after inoculation, a time at which plant height was reduced and root proliferation increased. Concurrently, above- and below-ground symptoms were also observed.