الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Since date palm is a dioecious and heterozygous fruit tree, and for commercial purposes most often vegetatively propagated through offshoots, its germplasm cannot be stored or handled easily by conventional means. At the present, the most common method used to preserve the genetic resources of date palm is as whole plants on farm. Tissue culture in combination with molecular biology techniques are of great interest for collecting, characterization, multiplication and conservation of date palm germplasm.In this study two different approaches for in vitro conservation using minimal growth conditions or cryopreservation of date palm cultivars (Bartamoda and Sakkoty) were investigated.
Results obtained could be summarized as follow:
1. In vitro conservation using minimal growth conditions.
1.1. In vitro conservation using low temperature (5 ° C).
1. Storing at low temperature (5 ° C) increased the survival percentage and subsequently decreased the mortality percentage of embryogenic callus cultures of the two cultivars.
2. The survival percentage was decreasing with increasing the storage periods in both two cultivars.
3. The embryogenic callus cultures could be stored for twelve months in low temperature with considerable survival percentage, in which Bartamoda registered 97.7 % and Sakkoty registered 88.8 % of survival.
4. Storing the embryogenic callus cultures of the two cultivars at low temperature (5 ° C) decreased the browning of cultures.
5. Storing the embryogenic callus cultures of the two cultivars at low temperature (5 ° C) decreased number of germinated embryos / culture comparing with storing at normal temperature(24 °C).
6. The cultures of Bartamoda were dark brown compared with those of Sakkoy.
1.2. In vitro conservation using different illumination conditions
1. Storing the embryogenic callus cultures of the two cultivars in dark condition significantly increased the survival percentage compared with those stored in light.
2. There was no sign of browning during the first six months as a result of both incubation conditions light or darkness for the two cultivars.
3. At the second six months, embryogenic callus cultures incubated at dark turned to be brownish. While, those kept in light turned to brown then dark brown at the end of the twelve months.
4. The number of germinated embryos/ cultures increased significantly till the ninth month for the two cultivars.
5. Non – significant increase with number of germinated embryos / culture was recorded at the end of storage period for the two cultivars.
6. Storing in dark conditions decreased significantly the number of germinated embryos / culture comparing with storing in light conditions.
1.3 In vitro conservation using osmotic active substances
1. Among the three types of osmotic substances, the different sucrose concentrations gave the highest percentage of survival and subsequently the lowest percentage of mortality with Sakkoty cultivar.
2. Using 40 g / l or 60 g/l mannitol and 20 g/l sorrbitol gave the highest percentage of survival and subsequently the lowest mortality percentage with Bartamoda cultivar.
3. Embryogenic callus cultures of Bartamoda were more sensitive to the browning than Sakkoty cultivar.
4. Using the different sucrose concentrations decreased the browning of the embryogenic callus cultures of the two cultivars.
5. The different sucrose concentrations gave the highest number of germinated embryos / culture of the two cultivars.
2. In vitro conservation using cryopreservation with liquid nitrogen (- 196 ͦ C):
2.1. Effect of sucrose concentrations in preculturing medium and air desiccation for two hour on survival and recovery percentages of cryopreserved embryos and callus cultures.
1. By increasing the sucrose concentration in the preculturing medium the survival percentage and subsequently the recovery percentage increased.
2. Adding 0.5 or 0.7 M sucrose to the pretreatment medium gave moderate survival percentage for embryos(20, 40 %) and callus (20, 10 %)of Sakkoty and embryos (20, 10 %) of Bartamoda.
3. By comparing the two cultivars it is found that Sakkoty cultivar gave significantly higher survival and recovery percentages than Bartamoda cultivar.
4. Exposing the explants to desiccation in the air laminar flow for two hours increased the survival percentage and subsequently the recovery percentages.
5. As for Bartamoda, its recovery percentage was low it does not exceed 10 % for embryos when 0.5 M or 0.7 M sucrose was added to the preculturing medium followed by air desiccation for two hours.
2.2 Effect of encapsulation using sodium alginate concentrations on survival and recovery percentages of cryopreserved embryos and callus cultures.
1. Using encapsulation technique increased the survival percentage and subsequently the recovery percentage.
2. The highest survival and recovery percentages were recorded with adding 0.5 and 0.7 M sucrose in the pretreatment medium and encapsulated with 4, 5 % sodium alginate for embryos and callus of Sakkoty.
3. Recovery was observed with Bartamoda embryos only, its recovery percentage was low it does not exceed 10 % with adding 0.5 and 0.7 M sucrose in the pretreatment medium and encapsulated with 4, 5 % sodium alginate.
4. All Bartamoda callus failed completely to recover.
5. Sakkoty cultivar gave significantly higher survival percentage than Bartamoda cultivar and subsequently the recovery percentage of Sakkoty was significantly higher than Bartamoda.
3- Genetic stability study:-
3-1.Molecular characterization using Random Amplified polymorphic DNA ( RAPD ) for conserved embryogenic callus cultures of date palm cvs Bartamoda and Sakkoty
3.1.1. RAPD analysis for in vitro conserved embryogenic callus cultures using both low temperature (5°c) and darkness of date palm cvs Bartamoda and Sakkoty.
1. At DNA molecular level, RAPD analysis of in vitro preservation treatments of the two date palm cultivars exhibited a genetic variations.
2. The Bartamoda cultivar gave the highest percent of similarity (57.5) and Sakotty cultivar gave the lowest percent of similarity (31.25).
3.1.2. RAPD analysis for in vitro conserved embryogenic callus cultures using osmotic substances added to the medium of date palm cvs Bartamoda and Sakkoty.
1.At DNA molecular level, RAPD analysis of in vitro preservation treatments of the two date palm cultivars exhibited a genetic variations.
2. The Bartamoda cultivar gave the lowest percent of similarity (40.91) and Sakotty cultivar gave the highest percent of similarity (78.95).
3. Preservation using different osmotic agents had an inversely results for preservation using low temperature and light conditions for similarity percent.
3.2-Molecular characterization using Random Amplified polymorphic DNA ( RAPD ) among the different in vitro preservation treatments using different cryopreservation methods (pretreatments or pretreatments and encapsulation) for both callus and embryos of Bartamoda and sakkoty cultivars.
1. At DNA molecular level, RAPD analysis of in vitro pretreatment of callus tissues and embryos and also for pretreatment and encapsulated embryos cultures and callus tissues for date palm cultivars (Bartamoda and sakkoty) exhibited a genetic variations.
2. The pretreatment Bartamoda cultivar embryos cultures gave the highest percent of similarity (83.34) followed by pretreatment and encapsulated sakkoty callus tissues (81.5), pretreatment sakkoty cultivar embryos cultures (75), pretreatment and encapsulated sakkoty cultivar embryos cultures (70), pretreatment and encapsulated Bartamoda embryos cultures (69.23) and the lowest similarity was recorded for pretreatment sakkoty cultivar callus tissues (62.5).
3. This variation could be due to the somaclonal variations occurred during culturing of explants in non-normal conditions and proliferation of callus tissues with high variation in cell division or differentiation under in vitro conditions or occurred during in vitro conservation process.