Abstract: Agrobacterium-mediated in vivo transformation of lateral buds of citrus plants has been developed and been combined with in vitro cloning. This new approach has ingeniously detoured plant regeneration and the long juvenile stage of regenerated plants from protoplasts, which limits gene transformation of most fruit trees including citrus. It makes the elimination of remaining bacteria and the selection of transformants be easy and efficient by using the natural growth of buds. In addition, this approach has combined the cloning of transfonnants in order to increase population rapidly. In demonstrating experiment, 21 out of 112 treated buds of Shatian pummelo ( Citrus grandIs Osb. ) developed into primary branches which gave 76 secondary buds. 4 in 76 secondary buds (5.26%) were proved to be positive by GUS activity assay. Among 14 cluster buds differentiated from the in vitro culture of 4 positive buds, 4 showing highest GUS activity and being positive in Southern hybridization were regenerated into tree plants. This approach could be used as a simple and effecient method for the transformation of a wide range of fruit tree species.

Key words: Gene transformation, Citrus