| Sweet potato is an important food and economic crop. There is abundant nutrition in their storage root and leaf. It is widely used for man's food and materials of industry. The nucleus type of sweet potato is homogenous hexaploid. The chromosome background is rather complex. The self-crossing is sterile. Crossing in specific and interspecific crossing are non-compatible or leading to low seed ratio in sweet potato. Conventional breeding technology has localization in variety improvement while transgenic technology has great potential to increase the production,improve quality and resist plant diseases and pests.An efficient regeneration system is very important for successful transformation. Comparingwith other plants, regeneration of sweet potato is very difficult. The difference of regeneration frequency is great in different genotypes. There are about 1100 varieties while only ten of them have been studied. Several varieties have been reported for high regeneration frequency and been successful transformed, such as Jewel, White Star, Lizixiang, Gaoxi14 and so on. Most of popular varieties have such a low regeneration frequency that there is not one transgenic plant that has been commercially used though the genetic engineering have made much progress.There are several methods to introduce foreign gene into the genome of sweet potato, but only the Agrobacterium-mediated transformation is most effective. The foreign gene is transformed in single copy by this means and so convenient for breeding. Chuanshu34 is an excellent variety in southwest area. This experiment established high frequency regeneration system of Chuanshu34, Chuanshu8129-4 and Xushu18 via somatic embryogenesis, optimized the transformation conditions of Chuanshu34 by transient expression of GUS-intron gene. These work founded the base for next step to improve quality of sweet potato by gene engineering technology.The primary results are listed as following:1.Established 3 high frequency somatic embryo regeneration systems of different genotype by testing different plant hormones. The regeneration frequency of Chuanshu34, Chuanshu8129-4, Xushu18 was 49.9%, 29.7%, 14.7% respectively.2.L22 and L8 with high frequent embryogenesis, the two lines were chosen from plantlets of Chuanshu34. Explants from them were good for genetic transformation.3. Optimized the transformation factors through GUS-intron transient expression. The most effective transformation factors were detailed as below:Inoculation bacterium was O.D.600=0.5. The explant was leaf or petiole of Chuanshu34, inoculation time was 60 min, and the explant was sonicated for 1 min to increase the tansformation frequency. Inoculation bacterium and co-cultivated medium were added 200umol/LAS. Co-culture took place in dark for 3 days. Transient expression frequency detected by reporter gene was 30% or so and transgene can steadily express in next step. |
