|Mennan, Sevilhan -|
Submitted to: Turkish Journal of Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 28, 2011
Publication Date: January 13, 2012
Citation: Mennan, S., Handoo, Z.A. 2012. Histopathology of Brassica oleracea var. capitata subvar. alba infected with Heterodera cruciferae Franklin, 1945 (Tylenchida: Heteroderidae). Turkish Journal of Entomology. 36(3):301-309. Interpretive Summary: Plant-parasitic nematodes are microscopic worms that feed on plants and cause an estimated ten billion dollars of crop losses each year in the United States and 100 billion dollars globally. Cabbage cyst nematode is an economically important nematode that damages the roots of cabbage and related plants. One approach to solving the problem of developing a safe method of controlling this pest is by studying the anatomical changes induced by this nematode in cabbage roots and subsequently designing methods to interfere with the formation of these changes. In this study, an ARS scientist from Beltsville, Maryland in collaboration with a scientist from the Ondokuz Mayis University, Samsun, Turkey, discovered the anatomical changes induced by cabbage cyst nematode on the roots of cabbage plants growing in Turkey. The most conspicuous anatomical change was the dissolving of plant cell walls within 24 hours of infection to form a specialized structure upon which the nematodes feed. The results are significant because they provide the first microscopic description of the interaction between the cabbage cyst nematodes and the cabbage varieties grown in Turkey. Because this information will be helpful in the development of cabbage varieties resistant to Turkish cabbage cyst nematodes, this research will be used by scientists developing safe methods of controlling this nematode.
Technical Abstract: Because anatomical changes induced by the cabbage cyst nematode (Heterodera cruciferae) have been insufficiently characterized, here we describe these changes in the root tissues of white head cabbage varieties 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 (control) or 1000 juveniles/300 ml soil. Three, 6, 12, 24, 48 and 72 h and 30 days after inoculations, two plants were removed from both treatments and put into FAA fixative for 10 days, and then examined by photomicrography. Second-stage juveniles directly penetrated roots, passed through the vascular system (xylem and phloem), became sedentary and started to feed. In the cortex of infected plants, large cells seen in cross section were filled with moderately dense cytoplasm and the walls were heavily stained and ruptured. In longitudinal section, the internal walls were perforated. Several significant changes were observed in root tissue of Brassica cultivars 3 hours after inoculation. Syncytia were noticeable 24 hours after inoculation. The syncytia had different degrees of vacuolization, and syncytial nuclei were usually hypertrophied and deeply indented and contained conspicuous nucleoli. 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. Plant height in infected plants was extremely smaller than the control plants, and uninfected plants had moderately more leaves than infected plants. Root proliferation was conspicuous in infected plants; although root color was the same, roots were shorter in infected plants.