This is the first record of Tobacco mosaic Tobamovirus (TMV-S) on sunflower in Egypt. It was originally isolated from naturally infected sunflower plants growing in Giza Res. Station, showing systemic mosaic and spots. Purified TMV-S migrated as a single zone in density gradient column. Ultraviolet absorbance ofTMV-S was typical of nucleoprotein with minimum and maximum at 247 and 260 nm respectively. The ratios of A260/280 and Amax/min were 1.2 and 1.1 respectively. Electron microscopy of purified virus showed the presence of rod shape particles with a size 300 nm. Titer of the prepared antisera as determined using ELISA was 1/2000. Electron microscopic examination of infected leaves of N. clevelandii founed various cytological abnormalities. Due to the non-availability of sources of resistance in Egypt to TMV-S in sunflower, a mutation breeding program was initiated. Seeds of two genotypes were subjected to four doses of gamma rays; O, 100, 200 and 300 Gy from a 60Co source. Ml and M2 generations were sown at the experimental fann of the Agricultural Res. Center to induce variability in the sunflower genotypes; Giza 102 and Sakha 53, which could be resistant to TMV-S. The statistical analysis indicated significant differences among irradiation doses on plant height; all used doses increased plant height comparing with the control. Inoculation with TMV-S caused decreases in plant height over all other factors. Number of leaves differed significantly according to the used cultivars, gamma ray doses and T&W-S. The highest number of leaves were found during M2 generation, The differences in head diameter between cultivars were significant. The highest head diameter was observed in Giza 102 (21.7cm) in M1 generation, followed by 20.2 and 20.0 cm for Giza 102 genotype developed through irradiation with 300 Gy in M  generation and Sakha 53 genotype developed through irradiation with 300 Gy in M1 generation. Seed yield per plant differed significantly between all cultivars.