Samar Ahmed Abdelaziz Ahmed, <br/><br/>
The induction and selection of abiotic stresses tolerance in balady apple through tissue culture technique / 
 الإستحداث والإنتخاب لصفة تحمل الإجهادات البيئيه فى أصل التفاح البلدى باستخدام تقنية زراعة الأنسجة 
by  Samar Ahmed Abdelaziz Ahmed ; Supervisors Dr. Emam Abdel Mobdi Abdel-Rahim, Dr. Mohamed Magdy Rashed, Dr. Rania Ahmed Mahmoud.  
 - 156 pages :  illustrations ;  25 cm. +   CD. 
<br/><br/>Thesis (Ph.D)-Cairo University, 2025. 
<br/><br/>Bibliography: pages 139-156. 
<br/><br/> The apple (Malus domestica) is a fruit that is cultivated extensively and has <br/>significant economic value worldwide. Soil salinization and drought consider to be <br/>major threats to apple production in some regions. The study aimed to facilitate the <br/>detection and selection of salt and drought stresses tolerance in apple (Malus domestica) <br/>seedling clones through tissue culture technique. Open pollinated mature seeds of local <br/>Egyptian ‘Balady’ apple were collected from ripped fruits of one tree and used as <br/>establishment plant materials. Every surface-sterilized seed was cultivated <br/>independently and assigned a distinct serial number. None of the micro-propagated <br/>individuals was typically as compared to each other or with the mother-plant according <br/>to similarity indices based on Inter Simple Sequence Repeats (ISSRs), where the most <br/>dissimilar genotype to the mother-plant was MS5 represents 84.9% similarity. After <br/>three consecutive subcultures, salt stress was achieved by adding different <br/>concentrations of NaCl (0, 1000, 2000 and 3000 ppm) to the proliferation medium, <br/>while stimulated drought stress by adding different concentrations of mannitol (0, 50, <br/>100, 150 and 200 mM). The MS5 clone maintained relatively higher number of shoots, <br/>average shoot height and fresh weight together up to 3000 ppm NaCl comparing to <br/>other tested clones which indicated the superiority of MS5 clone under severe salt stress <br/>conditions. A specific positive marker of 290 bp by HB12 ISSR exclusively detected in <br/>the most salt-tolerant MS5 clone may support early selection for salinity tolerance. The <br/>most salt-tolerant MS5 clone was characterized by the least average of reducing sugars <br/>and total phenols accompanied by the minimum overall antioxidant activity, with <br/>stimulated activities of superoxide dismutase (SOD), peroxidase (Px) and catalase <br/>(CAT) antioxidative enzymes over control as affected by elevated salt concentration up <br/>to 3000 ppm NaCl. Data of three common differentially expressed genes (DEGs) <br/>revealed that, protein phosphatases PP2C-77a and ABA insensitive transcription factor <br/>ABI5-5b were downregulated while serine/threonine-protein kinase SAPK3 was <br/>overexpressed in MS5 genotype under severe salt stress conditions. The MS18 clone <br/>was the most adversely affected by osmotic stress induced by mannitol additives <br/>indicating its sensitivity to drought stress compared to other clones which responded to <br/>drought at varying levels. Also, it was the most susceptible clone under saline <br/>conditions, which indicates potential overlapping tolerance pathways of both <br/>dehydration and salinity abiotic stresses. The study confirmed the viability of in vitro <br/>screening for salt- or drought-tolerant genotypes within apple seedling populations.    باستخدام تقنية زراعة الأنسجة جمعت بذور ناضجة ملقحة تلقيحا حرا لتفاح "بلدي" المصري المحلي (Malus domestica) من ثمار شجرة واحدة واستخدمت كمواد نباتية تأسيسية. زُرعت البذوروتم تعيين رقم تسلسلي مميز لها. ولم تتماثل الأفراد المتكاثرة بدقة مع بعضها أو مع النبات الأم وفقًا لمؤشرات التشابه القائمة على التكرارات التسلسلية البسيطة (ISSRs)، و ثبت جدوى الفحص المختبري لتحمل الجفاف، ووجود نمط جيني عالي التحمل للملوحة بين شتلات التفاح. و امكان استخدام الفحص المختبري للجينات عالية التحمل لصفتي الملوحة و الجفاف بين مجموعات شتلات التفاح لانتاج شتلات تتحمل ظاهرتي الاجهاد البيئي الملوحة و الجفاف. 
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<br/><br/><br/>Text in English and abstract in Arabic & English. 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Agricultural Biochemistry   <br/>الكيمياء الحيويه
<br/><br/><label>Subjects--Index Terms: </label>Apple  salinity  drought  in vitro  seedling clones  antioxidant  ISSR  التفاح  الملوحة 
<br/><br/><label>Dewey Class. No.: </label>630.24