2002 The American Genetic Association 93:179–184 Complementary Action of Two Independent Dominant Genes in Columbia Soybean for Resistance to Soybean Mosaic Virus

A stem-tip necrosis disease was observed in the soybean [Glycine max (L.) Merr.] cultivar Columbia and its derivative OX686 when infected with a necrosis-causing strain of Soybean mosaic virus (SMV) in Canada. A dominant gene named Rsv3 was found in OX686 for the necrotic reaction. In the present research we have found that Columbia is resistant to all known SMV strains G1–G7, except G4. Ge-netic studies were conducted to investigate the inheritance of resistance in Colum-bia and interactions of resistance gene(s) with SMV strains. Columbia was crossed with a susceptible cultivar, Lee 68, and with resistant lines PI96983, Ogden, and LR1, each possessing a resistance gene at the Rsv1 locus. F1 individuals, F2 pop-ulations, and F2:3 lines from these crosses were inoculated with G7 or G1 in the greenhouse. Our inheritance data confirmed the presence of two independent dom-inant genes for SMV resistance in Columbia. Results from allelism tests further demonstrate that the two genes (referred to as R3 and R4 in this article) in Columbia were independent of the Rsv1 locus. R3 appears to be the same gene previously reported as Rsv3 in OX686, which was derived from Columbia. The R3 gene confer