Resistance conferred against bean common mosaic virus by the incompletely dominant I locus of Phaseolus vulgaris is active at the single cell level.

A protoplast transfection system was used in Phaseolus vulgaris to study the incompletely dominant resistance locus I. The genetic materials in the study were cultivar 'Black Turtle Soup' lines nearly isogenic for I and their F1. Accumulation of bean common mosaic virus (BCMV; genus Potyvirus) RNA and virions was assayed following BCMV RNA electrotransfection of protoplasts from each genotype. BCMV RNA and virions accumulated in all genotypes tested but the relative rates of RNA accumulation differed. This suggests that the I allele is active at the single cell level and in a dosage-dependent fashion and supports previous work in this area.