| Cotton is the world's leading natural fiber crop and the second largest oil crop. The production and consumption of cotton fiber is a mainstay of the world's economy, and is also very important for the economy of china. Because of the narrow germplasm base of today's cultivated cottons , the variation among today's cultivated varieties is very small. Traditional breeding methods are not so effective today as in the past. New breeding methods are demanded to create new cotton varieties for the purpose of increasing fiber yield per acre, improving fiber quality, lowering production cost and increasing the income of cotton growers.Biotechnology is a new approach of plant breeding. Its goal is to manipulate gene expression in ways that produce desired phenotypic effect. Cotton biotechnology have achieved complete success in the past decade, the total acres committed to transgenic cotton engineered for insect or herbicide resistance have been increasing fast from its commercial release. However, the development of transgenic cotton plants is still very difficult with barriers such as long transformation cycle, highly genotype dependent and fertile of regenerated plants in the way. The cotton transformation methods should be improved.Cotton disease causes enormous loss of potential production every year. Although, the insect and herbicide transgenic cotton have reached great success, disease-resistant transgenic cottons have not reached the market yet. It is needed to deliver disease-resistant genes into cotton to evaluate their effects for cotton disease resistance.The high frequent somaclonal variation of regenerated cotton plants is an obstacle to the cotton transformation, and the plant somaclonal variation itself is worth exploring. So we decided to study the rules and mechanism of cotton somclonal variation.In this dissertation, gene delivery systems used to generate transgenic cotton were compared, effective cotton transformation procedure was set up, then we delivered a few disease genes intocotton genome, and morphological changes of transgenic cotton plants \\ith disease gene were analysed. A few characters of cotton somalclonal variation were analysed, the morphological and gene expression difference between the chvl, a homeotic somalclonal variani of conon. and the wild type were researched. The main results are as following:1. Selection of lines with high regeneration abilityWhen hypocotyls segments of seeds from regenerated Chuanmian 239 and Jimian14 plants were cultured on hormone free MSB+KNO31.9g/1hMSBK) medium, callus induction frequency was 70%, plant regeneration can achieved within 3 months in some cases. Typical direct embryogenesis was found when hypocotyls segments of seeds from regenerated Jiminn14 plants were cultured on MSBK medium. The second generation seeds reproduced by regenerated plants remained high regeneration ability but the ability was different among seeds collected from different individual plants.Seeds from regenerated Jimian14 plants are our selected material with high regeneration ability, the embryogenetic frequency of the material was 87.3%. 63.9% or 90.0% on MSB medium with IA A 0.5mg/L+KT0.1 mg/L, 2.4-D0. 1 mg/L+KT0. 1 mg/L or ZT2.0mg/L respectively.2. Cotton transformation approachesTransformation of embryogenetic callus by particle bombardment: Embryogenic callus of 'Chuanmian 239' were bombarded with gold particle coated with plasmids coding B-glucuronidase (GUS) and neomycin phosphatransferase (NPTII). Regenerated plants were verified to be transgenic by histologicai staining for GUS expression and PCR amplification of the NPTII. Factors that affect biolistic transformation efficiency were studied. Plasmids isolated by alkaline lysis and purified by PEG precipitation produced more blue foci, when bombarded into cotton callus, than plasmids isolated with Roche DNA maxprep kit; When the helium was 1550PSI, the suitable target distance were 6cm and 9cm; Embryogentic callus cultured for l-2week before bombardment were found to be the best t...
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