Studies Of Establishment Of Regeneration System Of Populus Alba. And Transformation Of RolB-pttGA20ox Genes For Promoting Rooting And High Growth Of The Plants

The major objective of this study was to breed new Populus alba varieties with improved rooting ability and apical dominance through transformation of the rolB-pttGA20ox two genes by using Agrobacterium tumefaciens-mediate transformation technology. For this purpose, first, an efficient in vitro propagation system and plant regeneration system were developed for Populus alba. Factors that affecting shoots regeneration via direct organogenesis, including cultivation conditions and plant growth regulators, etc., were also investigated in details. Subsequently, parameters that affecting the efficiency of Agrobacterium tumefaciens-mediate transformation of Populus alba were comprehensively studied and optimized by accessing NPTⅡexpression, and a transformation protocol was established. Finally, on the basis of the established transformation protocol, rolB-pttGA20ox genes were stably transferred to the Populus alba by PCR and Southern blotting tests.The main results of this study were introduced separately as following:1. Regeneration system of adventitious buds from stem segmentsStem segments with axillary buds were sterilized in 70% alcohol about 30s and then in 1%NaClO about 15min～35min. Survival percentage of explants was 94%. The most optimal induction medium was MS+6-BA0.5mg/L+NAA0.1mg/L,in which the differentiation rate of explants could be up to 74.1%. The most optimal proliferation medium was MS+6-BA1.0mg/L+NAA0.3mg/L+KT0.2mg/L+IBA0.4mg/L, the proliferation coefficient of buds being 8.3. The most optimal rooting medium was 1/2MS+IBA0.2mg/L, rooting rate being up to 100%.2. Regeneration System of adventitious bud from leavesThe optimum medium for adventitious bud regeneration was MS medium supplementing with 6-BA and NAA(ratio was 5:1) (MS+6-BA0.5mg/L+NAA0.1mg/L+Sugar2.5%+agar0.55%),and the frequency of adventitious bud regeneration is more 95%;The best leaves for adventitious bud regeneration is the first three top leaves of a shoot.The leaf explants of rooted tube plants is more propitious to induce adventitious buds than those of non-rooted tube plants.The differentiation rate of adventitious bud is higher under 14h illuminations per day than others.3. Hyperhydricity in Populus alba.regenerated in vitro: involvement of physiological, biochemical and morphological aspectsThe leaf and stem anatomy in non-hyperhydric and hyperhydric Populus alba was investigated aimed to identify structural changes associated with this phenomenon. In non-hyperhydric organs there were smaller and more organized cells, besides a more differentiated vascular system when compared...