Standardization in Inoculation Procedure and Effect of a Resistance Gene on Infection of Tomato Protoplasts with Tobacco Mosaic Virus RNA

Abstract

Inoculation at 0.degree. C improved the efficiency of infecting tomato protoplasts with RNA of tobacco mosaic virus (TMV). Up to 41% infection was obtained when inoculation was at 0.degree. C with 10 .mu.g/ml RNA in the presence of 1 .mu.g/ml poly-D-lysine in 0.01 M-potassium citrate buffered 0.7 M-mannitol (pH 5.2). The homozygous gene for resistance Tm-1 was expressed in tomato protoplasts inoculated with RNA of TMV-L, a common tomato strain of TMV; no virus progeny were detected by fluorescent antibody staining or infectivity assay. Virus multiplied rapidly in protoplasts from susceptible homozygotes. Protoplasts homozygous for Tm-1 were infected by the RNA of TMV-CH2, a tomato strain which can overcome this resistance in plants. These results resemble those previously reported for inocula using intact virus, and suggest that Tm-1 blocks virus growth after the uncoating stage.