Thesis (Ph.D)-Cairo University, 2025.

Bibliography: pages 134-152.

Improvement of fruit trees to withstand abiotic stress is becoming a major
goal to mitigate the threatening effects of the climatic changes on fruits
productivity. Apricot (Prunus armeniaca L.) is one of the most economic
deciduous stone fruit crops globally. This study aimed to develop an efficient in
vitro regeneration protocol for the Egyptian Al-Amar apricot rootstock, and laying
the foundation for its genetic enhancement through introducing a dehydrin gene
isolated from mangrove (Avicennia marina L.) via the agrobacterium-mediated
transformation system. Two types of explants, cotyledons and hypocotyls, were
cultured on 48 woody plant medium (WPM) with various concentrations of TDZ,
IBA or NAA to optimize shoot induction and regeneration. Cotyledons exhibited
direct somatic organogenesis, with the highest bud induction (78%) achieved on
WPM containing 13.62 µM TDZ + 2.46 µM IBA. While, hypocotyls underwent
indirect regeneration through callus formation, with the callusing rate (96.87%) on
WPM supplemented with 15.89 µM TDZ + 1.61 µM NAA. Shoot proliferation
was most successful on media with 8.87 µM BAP and 0.54 µM NAA, with
hypocotyls producing more shoots per explant than cotyledons. Optimal rooting
occurred on WPM with 9.80 µM IBA. In parallel, the full-length of the dehydrin
gene DHN was isolated from Avicennia marina via RT-PCR and cloned into
pGEM-T Easy vector for sequencing and subsequently cloned into the pRI 201-AN
plant expression vector. This construct was introduced into Agrobacterium
tumefaciens LBA4404. Al-Amar cotyledon and hypocotyl explants were co-
cultivated with Agrobacterium, followed by selection on media containing
kanamycin and cefotaxime. For cotyledons, the highest survival rate (54.1%) was
observed with 500 mg/l cefotaxime and 100 mg/l kanamycin and buds induction of
20.9% was achieved on 400 mg/l cefotaxime and 50 mg/l kanamycin. In contrast,
hypocotyls showed better survival on 500 mg/l cefotaxime and 50 mg/l kanamycin,
but had limited callus formation. PCR screening confirmed the presence of the
DHN gene in transformed tissues. The transformation efficiency of buds derived
from cotyledons and calli induced from hypocotyls was 1.04% and 0.50%,
respectively. This study represents the first attempt to develop an Egyptian
transgenic apricot rootstock with improved salinity tolereance which could pave
the way for producing non-transgenic apricot fruits under adverse conditions via
transgrafting.

تم تأسيس برتوكول فعال لإعادة التكشف معملياً لأصل المشمش المصري (العمار) باستخدام نوعين من المنفصلات النباتية وهي: الفلقات والتي أظهرت تخليق الأعضاء الجسدية المباشر دون تكوين كالس وقد بلغت أعلى نسبة لتكوين البراعم (78%) و المنفصلات السويقة الجنينية والتي اتجهت للتخليق الغير مباشر للأعضاء النباتية من خلال تكوين الكالس ثم البراعم حيث بلغت أعلى نسبة لتحفيز انتاج الكالس (96.87%)، بالتوازي تم عزل جين الديهيدرين (DHN) الكامل من نبات المانجروف باستخدام تقنية النسخ العكسي (RT-PCR) ، وكلونته في ناقل التعبير الجيني في النبات pRI 201-AN ثم ادخاله إلى بكتريا الأجروباكتريم والتي استخدمت لاحقاً في التحول الوراثي لأصل المشمش "العمار" و بلغت كفاءة التحول الوراثي للبراعم الناتجة من الفلقات والكالس الناتج من السويقات الجنينية 1.04% و 0.50% على التوالي.

Issues also as CD.

Text in English and abstract in Arabic & English.