Inheritance of Reaction to Soybean Mosaic Virus in Soybeans1

Eight soybean [Glycine max (L.) Merr.] cultivars previously identiifed as resistant to soybean mosaic virus (SMV) and three susceptible cultivars were used in a study to determine the inheritance of reaction to SMV. Field‐grown F2 and F3 populations were inoculated with virus strain SMV‐1. Greenhouse studies were also conducted in which the stock was inoculated and the reaction of homozygous and heterozygous scions determined. A variant of SMV‐1, designated SMV‐l‐B, was isolated and used to inoculate cultivars showing differential reactions to SMV‐1. Two types of resistance were recognized. The highest level of resistance gave complete protection against both SMV‐1 and SMV‐l‐B. The lesser level of resistance gave protection against SMV‐1 in the homozygous condition, but some of the heterozygous plants were necrotic. All homozygous plants became necrotic after inoculation with SMV‐l‐B. We proposed that the highest level of resistance be symbolized Rsv Rsv, the lesser level of resistance as rsvt rsvt, and the susceptible as rsv rsv. Rsv, rsvt, and rsv form an allelomorphic series with Rsv dominant to rsvt and rsv; and rsvt dominant to rsv.