UW Soybean Plant Health
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Soybean seed with seed coat mottle. Photo credit: Craig Grau |
Seed coat mottling occurs when pigments diffuse from the seed hilum. Some seed are entirely black or brown, but bicolored seed are by far more common. Hilum color will determine the color and intensity of seed coat discoloration.
Mottled seeds are an issue for grain grading, especially for food grade soybeans. Mottling is associated with poor germination and yield.
Seed coat mottling is a symptom associated with virus-infected plants, including Bean Pod Mottle Virus and Soybean Mosaic Virus. All mottled seed is not caused by virus, however. Insect feeding and physiological stresses can also cause seed mottle. Sometimes virus-infected seed does not show mottling symptoms. Therefore seed mottling is not a good predictor of virus infection.
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Fewer seed, shriveled seed and feeding scars on seed caused by bean leaf beetle. Photo credit: Craig Grau. |
Importance of Virus-Free Seed
Seed transmission of soybean viruses is frequently 1% or less and different for each virus. Assuming 225,000 seeds/acre, this means a potential for 2250 virus-infected soybean plants. Insect vectors then increase this number during the growing season by spreading the virus as they feed.
Planting virus-free seed is an effective control of soybean mosaic virus because the virus is rarely found in plants other than soybean.
Information from this site can be copied and distributed for educational use. Please credit the source with our name and URL: University of Wisconsin-Madison, Departments of Agronomy, Entomology, and Plant Pathology at www.plantpath.wisc.edu/soyhealth.
Last update 4/4/06