EVIDENCE FOR COMPLEMENTATION OF PLANT POTYVIRUS PATHOGENIC STRAINS INMIXED INFECTION

Several strains of soybean mosaic virus (SMV) can be differentiated on the basis of the phenotypic response of Various soybean cultivars (e. g., the soybean line Williams '82 is susceptible to all SMV strains, w hereas the lines P.I. 96983, L78-379, and Davis are functionally immun e to SMV strain G2 but susceptible to strains G7 and G7a). Inoculation of the immune lines with G2, followed 2 days later by inoculation wit h G7 or G7a, resulted in systemic spread of the avirulent SMV G2. Furt her evidence suggests that complementation groups of SMV strains may e xist.