Thesis for the degree of

Ph. D, (Genetics), Faculty of Agricultural, Ain Shams University, 2013



Mono dehydroascorbate reductase (MDAR), an important enzyme of the ascorbate–glutathione cycle, is involved in salt tolerance of plants through scavenging of reactive oxygen species (ROS). In this study, a cDNA encoding AtMDAR1 gene from the Arabidopsis plant was introduced into wheat plants of Bobwhite 56 cultivar using biolistic gene gun to examine its role in salt tolerance. Two stable transgenic plants (MD5 and MD6) were selected in vitro in the second generation (T2). Overexpressing MDAR1 gene was selected in vitro using basta and confirmed by quantitative reverse-transcription PCR (qRT). The transgenic plants; MD6 were predicted to possess two copies of the transgene, while the other transgenic plants; MD5 was predicted to have four transgene integrations. The AtMDAR1 transcripts in transgenic wheat plants were higher than untransformed plants. The abundance of AtMDAR1 transcripts in transgenic plants; MD5 and MD6 were approximately 1.75 and 1.65, respectively, times the amount found in non-transgenic plants. MD5 and MD6 plants, also, accumulated greater amounts of ascorbic acid (AsA) than the non-transgenic plants. They also showed tolerance to salt at germination stage under NaCl 200mM concentration (11,600ppm). In a greenhouse experiment, these transgenic plants showed more vigorous growth than the non-transgenic plants (Bobwhite56) at 200 mM NaCl. In a high salt, transgenic plants; MD5 and MD6 had higher dry mass, shoot and root length, and higher tolerance index (Ti) in comparison to the non-transgenic plants. This suggested that the transgenic plants were more tolerant to salt stress and have potential for breeding salt-tolerant wheat.

Key Words: Wheat, MDAR, ROS, Bombardment, Transformation

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