VIEW ARTICLE

Ecology and Epidemiology

Soybean Mosaic Virus: Infection of Soybean Seed Parts and Seed Transmission. G. R. Bowers, Jr., Graduate research assistant, Department of Plant Pathology and International Soybean Program; Robert M. Goodman, associate professor, Department of Plant Pathology and International Soybean Program. Phytopathology 69:569-572. Accepted for publication 25 November 1978. Copyright 1979 The American Phytopathological Society. DOI: 10.1094/Phyto-69-569.

The presence of soybean mosaic virus (SMV) (Illinois severe isolate) in reproductive plant parts was compared in field-grown, manually inoculated soybean (Glycine max) cultivars Merit and Midwest. Soybean mosaic virus was detected in 100% of the flowers, immature seeds, and green pods that were tested but not in any of the dry pods. The percentage of Merit seeds containing detectable virus was 58% at physiological maturity and 0.8% at harvest maturity; the corresponding values for Midwest were 94 and 66%, respectively. The percentage of mature seeds containing SMV was the same as the percentage of SMV-infected seedlings arising from those seeds. The incidence of SMV transmission through seed was only slightly reduced after storage for 6 mo at 14 C. Infectious SMV was detected in the testas, cotyledons, and embryos from immature seeds of both Midwest and Merit. In mature seeds, infectious virus was detected in embryos of Midwest seeds but not in those of Merit seeds. Infectious virus was not detected in testas from mature Midwest seeds by a local lesion index, but the same testas contained viral antigen detectable by enzyme-linked immunosorbent assay. The relationship between the time during the growing season when the plants were inoculated with SMV and the incidence of seed coat mottling, percent germination, and the incidence of SMV transmission through seed was tested in field-grown Williams soybeans. Time of inoculation affected only virus transmission through seed, which averaged 16 or 3% if inoculation was before or after the onset of flowering, respectively.