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International Journal of Virology
Year: 2012  |  Volume: 8  |  Issue: 1  |  Page No.: 27 - 38

Characterization of Tobacco Mosaic Tobamovirus (TMV-S) Isolated from Sunflower (Helianthus annuus L.) in Egypt

Salwa N. Zein, Abd El-khalik, Khatab Samaa, A.A.H. Eman and Clara R. Azzam    

Abstract: 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 Research Station, showing systemic mosaic and spots. Purified TMV-S migrated as a single zone in density gradient column. Ultraviolet absorbance of TMV-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 found 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; 0, 100, 200 and 300 Gy from a 60Co source. M1 and M2 generations were sown at the experimental farm of the Agricultural Research 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 TMV-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 (21.7 cm) in M1 generation, followed by 20.2 and 20.0 cm for Giza 102 genotype developed through irradiation with 300 Gy in M2 generation and Sakha 53 genotype developed through irradiation with 300 Gy in M1 generation. Seed yield per plant differed significantly between all cultivars, irradiation doses and infection statuses. The 100 Gy of gamma ray irradiation doses decreased seed yield, while 200 and 300 Gy gamma ray dose increased seed yield per plant for both cultivars in both generations, the highest seed yield per plant were observed with Sakha 300 Gy in both generations, it was 104.1 g (M2) and 102.1 g (M1), while the highest seed index (100-seed weight) was noticed for Giza 102 genotype developed through irradiation with 200Gy in M1 generation. It seems that 200 and 300 Gy treatments increased the most of studied characters in M1 and M2 generations in sunflower. The increments in mean of head diameter as a result of applying 300 Gy gamma ray dose increased seed yield/plant and seed index which finally improved seed yield. Both morphological characters and seed yield were reduced significantly as a result of virus infection. The effect of treatment with the virus was negative in all irradiated Sakha genotype developed through irradiation with 100, 200 and 300 Gy, as well as and Giza 102 genotype developed through irradiation with 100 Gy, because these genotypes tend to be resistant to TMV-S as ELISA test reported.

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