Abstract: 【Objective】Sugar beet is an important sugar crop in the world. The sucrose content in roots is the key determinant of sugar beet quality. In order to study the improvement of saccharinity of sugar beet by two sucrose transporter genes from grape, VvSUC11 and VvSUC12, were introduced into sugar beet root using plant genetic engineering. The work will lay a foundation for using sucrose transporter genes to increase crop yield and quality. 【Method】 A bivalent root specific expression vector called pCAMBIA2301-SP1-VvSUC11-SP2-VvSUC12 containing grape sucrose transporters VvSUC11 and VvSUC12 genes was constructed and transformed into sugar beet variety KWS-9103 by Agrobacterium tumefaciens mediated transformation. Then PCR and RT-PCR analyses were used to confirm the integration and expression of the two genes in transgenic sugar beets. The leaf characters, physiological targets, tuberous root weight and saccharinity of transgenic and control plants were measured after transplanting to the field.【Result】Thirteen transgenic sugar beet lines were obtained by PCR and RT-PCR analyses. Results indicated that the average number of leaf width, petiole length and leaf number of transgenic plants were 19.31 cm, 29.17 cm and 38.33, which increased obviously by 31.81%, 16.61% and, 17.04%, respectively, the average number of leaf length were 25.16 cm, which increased insignificantly by 1.68%. However, there were no significant difference in the content of Chlorophyll a（1.31 mg•g-1）, Chlorophyll b（0.562 mg•g-1） and total Chlorophyll（1.87 mg•g-1） between transgenic and control plants. Compared to control, soluble sugar content (14.59 mg•g-1) of leaf was reduced markedly by 13.04%, but soluble sugar content (21.90 mg•g-1) of petiole was only increased by 3.36%. The average root weight and sugar content of individual plants were 3.067 kg and 183.2 g•kg-1, respectively. Compared with control plants, the root weight of transgenic plants increased by 5.91%, while saccharinity increased significantly by 9.41%. These results demonstrated that larger leaves and higher leaf number lead to the expansion of photosynthetic leaf area, and shorter petiole in transgenic sugar beets was not only helpful to accelerate the rate of transport of sugar molecules from the source leaves to the sink, but also promotes the formation of tuberous root and the accumulation of sugar.【Conclusion】The sugar transporters VvSUC11 and VvSUC12 genes transformation could effectively improve saccharinity in transgenic sugar beet.

Key words: Beta vulgaris , sucrose transporters , transformation , agronomic character , saccharinity