الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Fire blight is an important disease that causes decreasing in the yield of trees especially in pear and apple.Some antibiotics were used to treatment fire blight but some strain of bacteria gave resistance to these antibiotics.
The research study in this thesis was carried out at TissueCulture and Germplasm Conservation Laboratory Research-Horticulture Research Institute - Agriculture Research Centre and Horticultural Department, Faculty of Agriculture, BenhaUniversity during the period from 2013 – 2016.
Aim of the work The first experiment were carried out to micropropagate
both of two economical fruits pear Pyrus communis and Ananas
comosus to reach the best method on the behavior of micropropagation during two cycle of culture with callusproduction of pear and acclimatization of pineapple. The second experiments were achieved to evaluate the ideal method to prepare nanoparticle of silver or chromium by reduction method with stabilizing agents of two medicinal plants Melia azadrichtia Artemisia and study physical characterizations
of nanoparticles formed by SEM, TEM and UV-vis spectrum.
The third experiments were studied the effect of each chromium nanoparticles and silver nanoparticles with its
stabilizing agents on growth of Erwinia amylovora.by disk
diffuse test The fourth experiments are conducted in order to investigate the growth behaviors of infected callus in vitro and infected plants in vivo.
5.1.Pyrus communis 5.1.1. Sterilization stage It could be concluded that the treatments of 20 % colorex for 15 minutes and15% Clorox for 15 minutes were superior for sterilizing explants (micro nodes) Pyrus communis cv. Le-Cont Also, the other treatments should be avoided.The survival percentage of both treatments was highest level 100 %5.1.2. Establishment stage It could be present MS full as a good or satisfied media forin vitro growing the explants of Pyrus communis cv. Le-cont without die (100% survival). It could be recommended to use MS full for producing the callus from leaves of Pyrus communis cv. Le-Cont.