Figure 1. Soybean field with symptoms of infection by soybean cyst nematode, Heterodera glycines. Note poor stand and stunting of soybean plants. (Printed with permission of Dr. Lorin R. Krusberg, Department of Botany, University of Maryland, College Park, MD).
Figure 2. Segment of soybean root infected with soybean cyst nematode. Signs of infection are brown-white females or cysts with egg masses that are attached to root surfaces.
Figure 3. Histological section of soybean root showing intracortical penetration by an infective juvenile of soybean cyst nematode at 1 day after inoculation.
Figure 4. Longitudinal section of soybean root showing a third-stage juvenile of soybean cyst nematode at its feeding site and a syncytium. The syncytium, which functions as a food reservoir, has dense cytoplasm and multiple nuclei that result from dissolution of cell walls.
Figure 5. Extensive syncytium induced by a third-stage juvenile of soybean cyst nematode at 10 days after inoculation. Note cell wall fragments dispersed throughout cytoplasm.
Figure 6. Cross section of soybean root resistant to soybean cyst nematode, showing restricted development of nematodes and associated syncytia at 5 days after inoculation.
Figure 7. Cross section of root from a susceptible soybean cultivar, showing extensive sectors of xylem and phloem tissues replaced by syncytia with dense cytoplasm. At 21 days after inoculation, a nematode at this site (not shown) would be an adult female producing eggs that are either embedded in a gelatinous matrix secreted by the nematode or held within the cyst body for long-term survival and subsequent dispersal (see fig 2.)
Figure 8. Cross section of susceptible soybean cultivar at 40 days after inoculation, showing sectors of root occupied by syncytia. Some syncytia have been replaced by parenchymatous tissue.
Figure 9. Cross section of resistant soybean cultivar at 31 days after inoculation, showing minimal damage to vascular system. Necrotic area indicates former site of syncytium induced by nematode.
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