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Results of this research could be summed up in the following:
6.1. Most Relevant Results of Surveyed Populus Species
■ There were five species of Populus found in four different governorates as a result of the survey study. Surveyed species according to their location were as follow:
1) Giza governorate: P. euramericana female, P. euramericana male and P. Deltoides.
2) Cairo governorate: P. nigra.
3) Gharbia governorate: P. nigra, P. deltoides, P. alba and P. euramericana female.
4) Qaliobia governorate: P. nigra.
■ Populus species surveyed were characterized by different morphological, chemical and genetic differences that can help in discrimination of these species.
■ Leaf area and both width and length of leaves represent a very good descriptive indicator that can discriminate among species from a morphological point of view.
■ Chemical analysis results did not show any special variation among surveyed species of Populus.
■ from the genetic ISSR markers analysis, a high polymorphism percentage of 67.52% was obtained indicating that variation did exist between Populus species surveyed in their four locations.
6.2. Most Relevant Results of In Vitro Culture of Populus alba
■ For sterilization, the treatment with ‘clorox’ at 30% + 0.1 g/l HgCl2 for 10 min recorded the highest survival percentage (100%).
■ For culture media choice, MS medium showed better performance than WPM in the establishment stage. Moreover, ¾ medium strength of MS showed better performance for stem node explants.
■ For the multiplication stage, the supplementing of BAP at 0.075 mg/l + Kin at 0.1 mg/l to culture medium (¾ MS) gave the highest shoot and leaf number /cluster.
■ For in vitro rooting, the incorporation of NAA at 0.5 mg/l + AC at 0.25 g/l to the rooting medium (¾ MS) was adequate to obtain best root length and number/ young rooted shoot.
■ For ex vitro acclimatization, the combination of peat moss: vermiculite at 1:1 (v/v) as a potting medium recorded the highest survival percentage for produced plantlets (100%) with the tallest plantlets (25.1cm) after 6 weeks of acclimatization when compared to peat moss : sand (2:1 v/v).
■ No polymorphism was detected up to 14 subcultures of multiplication when an ISSR marker was used indicating the absence of genetic variation between in vitro raised plantlets of Populus alba and there to-start-with mother plants.
■ Populus species can be discriminated by two morphological characters, namely LA and/or width and length of leaves.
■ ISSR markers analysis of surveyed species suggests that there was a degree of recognizable polymorphism among them which means that there were clear differences in their genetic make-up.
■ Populus alba could be successfully micropropagated through tissue culture using a well fine-tuned protocol described earlier in this research study
■ It is safe to undergo up to 14 subcultures during in vitro multiplication without any risk of genetic un-stability of the final produced Populus alba plantlets.