الفهرس 
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Abstract
In order to investigate the influence of genetic background on salt tolerance, 20-day old seedlings from seven canola (Brassica napus L.) cultivars were subjected to salt stress for two weeks. The data showed that the cultivars differ genetically for their response to salt stress; and both of the plant dry weight and osmotic potential were decreased with increasing NaCl concentration in the irrigation water. The changes in protein and isozyme banding patterns under salt stress were determined. Salt stress increased peroxidase band intensities and induced some new peroxidase bands. Glutathione reductase (GR) activity was decreased with increasing NaCl concentration. But its activity was greater in leaves of salt stressed plants than in control plants. The genetic polymorphism among the seven canola cultivars tested, were resolved by using isozyme, protein and RAPD analyses. The protein profile showed a low level of polymorphism, as out of the 17 bands obtained only six were polymorphic (35.29 %). The esterase enzyme revealed high polymorphism among the seven canola cultivars (75 %). For RAPD a total of 152 scoreable bands were detected, 89 bands (58.5%) of them were polymorphic. The RAPD-genotype-specific marker indicates that 13 markers distinguish the cultivar Masrri-L11 and five markers distinguish the cultivar Masrri-L16. These markers can be verified as being RAPD markers associated with salt tolerance in the two canola genotypes. Five canola genotypes namely, Serw-4, Masrri-L11, Masrri-L16, Semu-304 and Semu-249 were selected for further tissue culture and transformation experiments. The data indicate that the hypocotyl explants exhibited an initial swelling followed by callus formation within two weeks of incubation. The cultivars Serw-4 and Semu-304 showed higher capability for production of somatic embryos at 4.5 mg l-1 BA compared with the other cultivars. The hypocotyl explants isolated from three canola genotypes (Serw-4, Massri-L11 and Semu-249) were co-cultivated with Agrobacterium tumefaciens LBA-4404 harboring the binary vector pBI-121. The stable integration of the T-DNA into the plant genome was confirmed using PCR and histochemical GUS assay. The transformation frequency was higher in the cultivar Serw-4, followed by Masrri-L11, while in Semu-249 no transformants were detected using the Agrobacterium method. To improve salt tolerance in canola plants, the Bnplc-2 (Phospholipase C-2) gene responsible for the stomatal opening under salt stress was fused with the gus gene under the genetic control of the 35S-CaMV promoter. The results indicate that the gus gene expression could be detected only in the transgenic plant leaves while the non transgenic leaves showed no gus expression. The gus gene expression in the biolistic-derived T0 plants was used as an evidence of the transferred plc-2 gene expression, the transformed plant material showing gus activity while the non-transformed plantlet showing no gus activity at all.