The present invention provides a method for Agrobacterium-mediated gene
introduction into a plant material, comprising: 1) treating the plant
material, and then 2) infecting the plant material with an Agrobacterium,
characterized in that a medium enriched in a metal salt containing copper
ion is used in step 1) and/or 2). The present invention also provides a
process for preparing a transformed plant characterized in that the gene
introduction method of the present invention is used.