الفهرس 
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Abstract
This work was carried out in the Tissue Culture Laboratory, Ain Shams Center for Genetic Engineering and Biotechnology (ACGEB), Faculty of Agriculture, Ain Shams University, Egypt, during the period between 2013-2018.
• Explants used in in vitro micropropagation were shoot tips from a three years old tree of Paulownia tomentosa and in Khaya senegalensis explants were shoot tips collected from young transplants.
• Murashige and Skoog basal medium (MS) was used as a culture medium in all stages of in vitro experiments.
• Shoot-tip explants were surface-sterilized under aseptic conditions using commercial bleach as ‘clorox’ (5.25% NaOCl) at 10, 15, 20, 25 and 30% + 0.5 g/l mercuric chloride (HgCl2) for 10, 15, 20 and 25 min.
• For multiplication, established shoot tips were transferred individually to an MS medium at 3/4 strength containing BA and Kin each at 0, 0.5, 1, 2, and 4 mg/l.
• For in vitro rooting, microshoots resulted from the multiplication stage were cultured on an MS medium at ¾ strength supplemented with IBA and NAA at 0, 0.5, 1, 2, and 4 mg/l.
• For ex vitro acclimatization, plantlets resulting from in vitro rooting were washed to get rid of medium remains and then dipped in a fungicide solution (Rhizolex) at 0.5 g / l for 30 min. Afterwards, they were ex vitro acclimatized by culturing in plastic pots filled with a mixture of
• Peat moss: perlite at (1 : 1 , 2 : 1 and 3 : 1 v / v) and kept afterwords under a plastic tunnel inside a plastichouse.
6.2. Most Relevant Results
The following summing up of results is true and verifiable for both Paulownia tomentosa and Khaya senegalensis plant species unless mentioned otherwise:
• The treatment with ‘clorox’ at 30%+0.5 g/l HgCl2 for 20 min recorded the highest survival percentage (100%).
• The supplementing of Kin at 4 mg/l to the multiplication culture medium gave the highest shoot length/shoot.
• The provision of BAP at 2 and 4 mg/l to the multiplication medium culture gave the highest leaf number and shoot number / shoot.
• The inclusion of NAA at 4 mg/l to the in vitro rooting medium gave the highest root length/shoot in Paulownia tomentosa but in Khaya senegalensis incorporation of NAA at 1 mg/l to in vitro rooting medium gave the highest root length/shoot.
• The incorporation of both IBA and NAA at 0.5 mg/l gave the highest root number/shoot in Paulownia tomentosa but in Khaya senegalensis incorporation of NAA at 0.5 and 1 mg/l to in vitro rooting medium gave the highest root number/shoot.
• The combination of peat moss: perlite at 2:1(v/v) as an ex vitro acclimatization potting medium recorded the highest survival percentage (80-86%) for the final produced plantlets after 6 weeks of acclimatization. The season of spring proved to be the best for ex vitro acclimatization of plantlets (refer to Plate 3 and 4).
• Up to 12 subcultures of multiplication no polymorphism was detected upon use of ISSR markers indicating the absence of genetic variation between in vitro raised plantlets.
6.3. Conclusions
Both Paulownia tomentosa and Khaya senegalensis could be successfully micropropagated through tissue culture by adopting the following protocol:
• Applying clorox (5.25% NaOCl) at 30% + 0.5 g/l HgCl2 for 20 min. as a sterilization agent was sufficient and satisfactory to ensure high survival rate of initial explants.
• Use of an MS medium at only 3/4 strength was adequate enough for initial establishment of explants.
• *The highest multiplication rate (number of shoots /shoot) could be achieved by inclusion of BAP at 2 mg/l.
• Adding NAA at 0.5 mg/l to the in vitro rooting medium was appropriate to obtain best (root number / shoot).
• A mixture of peat moss: perlite (2: 1 v / v) under a plastic tunnel was suitable during ex vitro acclimatization to achieve high survival percentage.
• The season of spring is the best for ex vitro acclimatization of plantlets. If not, then summer is second best to ex vitro acclimatize under Egyptian conditions.
• It is safe to undergo up to 12 subcultures during in vitro multiplication without any risk of genetic un-stability of the final produced plantlets.
Plate (3): Final produced plantlets of Paulownia tomentosa after 6 weeks of ex vitro acclimatization
Plate (4): Final produced plantlets of Khaya senegalensis after 6 weeks of ex vitro acclimatization