| Cotton is an important cash crop for its natural fiber. Production of cotton general decreases about 10%-20% for diseases and insect infestation every year. Many excellent cotton cultivars have been developed through genetic engineering since 1987, which play a role in further improving yield and quality of fiber, feed, and oil and in increasing the production efficiency and reducing both the monetary and environmental cost of production. However, many hinders still exisist in cotton transformation.. The main reason is that cultivars of transgenic cotton, which requires transformation of appropriate tissue followed by regeneration, remains extremely difficult in somatic embryogenesis and regeneration. Recalcitrant cotton cultivars, long tissue culture duration, the unpredictability of tissue culture, and a high degree of genotype dependence are more troublesome in regeneration of cotton. The length of time in cotton transformation can result in a higher rate of somaclonal variation. We have examined some factors that can significantly affect the efficiency of regeneration and transformation in cotton. The regeneration of insect-resistant plants and disease-resistant plants is developed through cotton embryogenic calli mediated by Agrobacterium tumefaciens, and some variations and mutants of transgenic plants are examined and analyzed in this dissertation. The main results obtained are listed below.1. IBA is one of the main factors determining the tissue culture response in cotton. Calli and embryogenic calli are induced in both media containing the optional combinations of IBA and KT, IBA 1.0 mg/L + KT 0.5 mg/L and IBA 0.5 mg/L + KT 0.3 mg/L, respectively. The efficiency of induction of embryogenic calli from the tissue culture reached 89.5% of Coker 201.2. Medium supplemented with 120 mg/L MgS04 7H2O is more effective for callus induction and proliferation of Coker 201 than the other media. And the medium supplemented with FeSO4 - 7H2O (chelated with EDTA) suppressed the growth of calli, however, and increased the quality of calli and promoted somatic embryogenesis. Somatic embryogenesis is facilitated through increasing the concentration of KC1 in medium. The same phenomenon is observed in the medium supplemented with 200 mg/L CaCl2 2H2O, however, which restrains the proliferation of calli. Somatic embryogenesis from calli derived from hypocotyls segments are observed only on inducing original callimedium containing NHLtNOs. Calli do not form somatic embryos in inducing original calli medium without NH4NO3. though most of calli remain good quality. The large number of somatic embryogenic calli are recorded on the medium containing double KNOj (3.8 g/L) but free of NI-LtNCv?. The percentage of embryogenic calli from all cultures reached more than 80% in Coker 201 through doubling KNO3 and omitting NH4NO3. In Coker 201, somatic embryos in the medium with 2.0 g/L Gin and 1.0 g/L Asn facilitated maturation, germination, and regeneration.3. A new protocol has been developed for the highly efficient somatic embryogenesis and plant regeneration of ten recalcitrant Chinese cotton cultivars. In-depth study of interaction of factors would enable the development of genotype-specific culture protocols to better exploit regeneration potential, which might enhance the embryogenesis of recalcitrant cultivars, e.g., Ekang 3, Ekang 4, Ekang 6, Ekang 8, Ekang 9, Ekang 10, Emian 22, Ejing 1, Bl, and Bll. The two regeneration protocols via somatic embryogenesis previously of choice for most laboratories, 2,4-D + KT and NAA + 2ip, suffer from extremely genotype dependence and low embryogenesis efficiency, 21.8% and 43.5%, respectively in our study, which were much lower efficiency in cotton somatic embryogenesis than the newly developed protocol, IBA + KT.4. It is a common knowledge that callus browning existed during somatic proliferation and somatic embryogenesis of cotton, but the mechanism is not clear. This research revealed that callus browning was related with programmed cell d...
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