الفهرس 
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Abstract
This work was carried out during two growing seasons of 2015 and 2016 at experimental farm of Faculty Agricultural Kafrelsheikh University, Egypt. on four grapevine rootstocks Ramsey, Harmony, Freedom, So4 and Thompson seedless as a cultivar. The objectives of this study was to induce mutations by gamma rays in five grapevine genotypes including commercial variety Thompson seedless to generate promising salt tolerant mutant grapevine rootstocks. In this study molecular markers were used to detect mutations induced and to test gene expression associated with salinity tolerance in grapevine.
Results showed that both doses of 10 and 20 Gy were effective in obtaining mutations in all five grapevine genotypes including Thompson seedless. Mutations were confirmed by morphological markers such as bud burst percentage, shoot length and number of leaves, and by genetic markers using RAPD technique. Six RAPD markers were able to generate polymorphic bands ranged from 1 to 9 among irradiated and un-irradiated grapevine genotypes. The similarity coefficients detected by RAPD markers ranged from 0.24 to 0.87, which revealed clear genetic variation among irradiated and un-irradiated grapevine genotypes. According to phylogenetic analysis, genotypes were divided into two clusters, where all five un-irradiated genotypes and irradiated Freedom genotype with 10 Gy were placed in one cluster and second cluster included the rest of nine irradiated genotypes. Furthermore, there was significant upregulation of VviERF073 gene expression level in the leaves of irradiated Thompson seedless and four rootstock plants compared to un-irradiated plants under various salinity concentration (50, 100, 150 mM). VviERF073 gene expression levels were increased in all genotypes significantly as a result of irradiation and salinity recording higher expression (10.68-folds) with Thompson seedless at 30 Gy, and 150 Mm.. This study suggests use of mutation breeding by gamma rays in grapevine rootstock improvements for salinity tolerance, and use molecular markers for detecting mutations and genetic diversity among grapevine genotypes.