Cowpea mosaic virus infection of protoplasts from Samsun tobacco leaves

Palisade parenchyma protoplasts i olated from the tobacco varieties Samsun and Samsun NN were inoculated in vitro with cowpea mosaic virus (CPMV). By fluorescent antibody staining it was demonstrated that about 75 o/o of the proto-plasts became infected. Poly-L-ornithine was required for infection. The cytopathic structures shown previously to be characteristic for CPMV-infected cowpea cells were also produced in CPMV-infected tobacco protoplasts. The optimum inoculum concentration for CPMV was 4 to 2o/zg/ml. Compared with CPMV multiplication in cowpea protoplasts and tobacco mosaic virus multiplication i tobacco proto-plasts, the growth of CPMV in tobacco protoplasts had a longer lag period but the virus concentrations in all three kinds of infection finally reached similar values. The difficulty with which tobacco leaves are infected with CPMV contrasts with the ease of infection of tobacco mesophyll protoplasts