 How Does SCN Cause
Disease?
The effect of SCN on soybean growth and yield involves
several mechanisms that are directly related to the numbers of nematodes
feeding on the root system: plant nutrients are removed, nutrient and water
uptake in the roots are disrupted, and root growth is retarded. Plants
infected with high numbers of SCN have poorly developed root systems that
cannot efficiently utilize nutrients and water available in the soil. The
results stunted plants and, often, chlorotic (yellow) foliage. Seed yields
are low because fewer pods develop on infected plants. SCN infections by
themselves do not reduce seed size, number of seed per pod, or seed quality.
SCN infection may also reduce the number of nodules
formed by the beneficial nitrogen-fixing bacteria that are necessary for
optimum soybean growth. In addition, penetration of roots by the infective
juvenile and swelling of the maturing female may create openings in the
root surface that serve as entry points for other soil-borne soybean pathogens.
This may make the plant more susceptible to root-rotting diseases such
as Rhizoctonia (seedling blight), Fusarium (sudden death
syndrome, wilt), and Macrophomina (charcoal rot).
SCN juveniles (stained pink) inside a soybean root.
Its specialized feeding cells are visible as gray masses(arrow).
Soybean Cyst Nematode Life Cycle
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