| Soybean is an important oil crop, grain and forage crop in China. With the acomplishment of soybean genome sequencing and the acceptance to transgenic plants for human being, more and more scientists are devoted to study soybean gene function and soybean germplasm innovation through transgenic method. Although soybean is sensitive to Agrobacterium infection, due to the difficulty of tissue regeneration, the Agrobacterium tumefaciens mediated transformation efficiency is still very low. The low transformation efficiency in soybean is limited to soybean gene function and gene transformation research. In this study, we optimizated the soybean Agrobacterium-tumefaciens mediated transformation sytem by explant, genotypes, Agrobacterium concentration, antioxidants and co-cultivation conditions so on. Using the optimized transformation system, the average soybean Agrobacterium-mediated transformation efficiency could be amounted to about 1.2% and in some occassions'transformation efficiency reached 8.83%. The optimized Agrobacterium mediated transformation system for soybean was:using the germinated Id cotyledonary node of YC-1 and YC-2 cultivars as explants, the concentration of Agrobacterium 0.8 (OD650) and co-infected 30 min, the 4d lighing co-cultivation on the co-cultivation medium which added 25 mg/L LA-a new antioxidant. The earliest transgenic seedlets emergences at 80 d after infection. We also transformed Sporamin and Chitinase KDEL genes into soybean using the optimized Agrobacterium-mediated transformation system. Twenty-five positive transgenic events were obtained and verified by PCR identification, leave herbicide painting assay. To assess the ability of the sporamin and chitinase KDEL genes to improvement of insect resistance. The resistance of transgenic plants to insects had also been evaluated by starscream and bollworm feeding. The Southern hybridization and RNA expression analysis for the transgenic plants need to be done.
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