Abstract: The factors affecting Agrobacterium -mediated gene -transformation of epicotyls of Citrus in viro are studied in this papre .Transgenic Poncitrus trifoliata with CTV-cp gene were obtained. The main results are as follows:As a selectable agent,concentration of Kanamycin is 20-30 μg/mL for Citrus except P.trifoliata,which is 50 μg/mL. The optimal cocultivation time of explants & Agrobacterium is 3 days. Gus transient expression frequency was promoted ,when the concentration of acetosyingone is 70-100 μmol /L. Gustransient expression frequency is higher in epicotyle from 20d seedling. Under the same transformation conditon, the rate of explant with resistant shoot and the rate of explant with Gus positive shoot are different in different Citrus species. Extral gene is proved to be into P.trfoliata by southern blot examination with probe of plasmind pGA482GG cut by Nco IE.

Key words: Agrobacterium, Citrus, Transformation