| Upland cotton (Gossypium hirsutum L.) is an important economic crop, also is an alien species introduced most successfully from America continent in China. Due to the poor natural resources of cotton germplasm in this country, it is difficult to bring a breakthrough in breeding out new varieties with fine agronomic and economic traits by traditional breeding program. Alternatively, by adopting the technology of genetic transformation, to transfer the genes with high economic values into the genome of cotton cultivars is an efficient way of creating out new varieties and new breeding materials. In this study, upland cotton shoot apexes were transformed with the constructs, which contain the gene encoding monooxygenase involved in growth hormone biosynthesis, via Agrobacterium mediated transformation. Novel cotton materials with the traits of high yield, fine quality, earlier ripening and male sterility were expected to be obtained in the population of transgenic plants.The main results in this study were as follows:1. Shoot apexes excised from sterile seedlings which were germinated in 1/2MS medium, were drenched in 0.8-1.2 OD concentrations Agrobacterium cultures about 15 min, then co-cultured 2d on the MS medium without antibiotic substance at 26℃. The explants were transferred onto the shoot selective medium supplemented with 30mg/L kanamycin and 100 mg/L cefotaxime to isolate kanamycin-resistant transformants.2. Total 3000 shoot apexes were prepared and used as receptor in the transformation experiment. After entire plantlets were regenerated under selection, then the shoots were grafted to the cotton seedlings with 1 to 2 flatted true leaves. The survival ratio of plantlets in grafting reached 13.9%-72.2%. By this method, we obtained 117 putative transgenic plants in the field, among which 82 plants were detected as positive through the PCR analysis. Then 7 putative transgenic plants were randomly chosen and applied in Southern blotting analysis, among which 6 plants were proved to have the foreign genes integrated in the genome and to be true transgenic.3. 21.4% to 78.9% plants in T1 populations were detected as positive by PCR analysis, indicating that some of the TO transgenic plants were chimera.4. The expression of GUS gene was detected by histochemistry localization method in root tissue of some TO transgenic plant, and the ratio of GUS staining positive was 50%.5. Compared with the control, great differences in growth characters existed inseveral TO transgenic plants, among which 7 showed crimple leaves in seedling stage; 6 showed prematurity; 16 showed overgrowth and boll-bearing branch changed to foliage branch; 2 had shortened internodes etc. Also compared with the control, the ratio of boll falling off in TO transgenic cotton was lower significantly and certain economic traits tended to be improved.6. The developmental characters of Tl transgenic cotton did not segregate apparently. The economic characters of the Tl plants were similar to those of the control except shorter plant height.7. The observation of pollen fertility in TO and Tl generations indicated that most male sterile flowers appeared during the period of high temperature. 73.3 percent of plants in Tl populations transformed with antisense-mo?o gene were expressed seasonal male sterility...
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