In order to transfer the dominant gene N , responsible for the resistance to TSWV, from Nicotiana alata to some Virginia tobacco cultivars, interspecific hybridations were performed followed by the "in vitro" culture of the immature embryos (around 7 days old), in order to obtain mature plants. Fertilization was achieved by applying a solution of colchicine (0.2%) in the culture medium. Backcrossings were performed in F2 using pollen from Virginia cultivars (Virginia 196 and Virginia 207) and F3 plants were obtained whose phenotype was almost identical to that of the tabacum type. The artificial test regarding the behaviour to TSWV, in the stage of 5-7 leaves, showed that the hybrid plants are resistant to the infection with TSWV. Thus, out of the 75 tested plants, 68 of them showed resistance to the artificial infection with TSWV. The resistant plants were grown up to their maturity. From 5 of these plants, anthers were collected and cultured "in vitro". Haploid plants were obtained which in approximately eight weeks reached the stage of 3-4 small leaves. Out of the two hybrid combinations, 25 haploid plants from each one were tested regarding the behaviour to the artificial infection with TSWV. It was found that almost all the plants showed resistance, by the appearance of small necrosis on the little leaves from the bottom of the plants. The haploid plants hypersusceptible to TSWV are going to be diploidized. Through the performed experiments, plants of Virginia type were obtained with the resistance to TSWV acquired from Nicotiana alata . The hypersusceptibility to artificial infection with TSWV showed by the haploid plants with a hemizygot genetic structure, emphasize the fact that the gene for the resistance to this virosis is dominant.