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Soybean
Mosaic Virus (SMV) also can cause seed
quality problems. Aphids are the vectors that spread the disease during a growing season.
Sometimes, portions of the soybean seed coat have a black discoloration as a
result of infection by SMV. However, this discoloration should not be considered
as a reliable indicator of SMV because other stresses can cause such mottling.
Seed testing is necessary to determine the presence of the infection. Infected
plant leaves are spindly, narrower than normal, have dark green swellings along
veins. Plants are stunted, petioles are short, as are the internodes. Infected
pods are small, flat, have less hair, and are curved more. Seed germination may
be reduced. This virus is seed-borne, can overwinter in perennial weeds, and is
spread by aphid species.
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