Abstract：Identifying the copy number of foreign gene in transgenic primary plants is the basic step in genetic engineering application. In this paper, Real-time PCR and the related PfaffI method, usually applied to studying transgenic expression，was used to analyze comparatively the differences of exogenous gene copy number of transgenic cotton(Gossypium hirsutum) T0 plants transformed with one same vector by three different methods, Agrobacterium-mediated, gene-gun bombardment and pollen tube injection, respectively. Results showed that in Agrobacterium-mediated T0 generation, the transgenic plants integrated one or two copy number accounted for only 26.2% of the total plants, respectively; In contrast, that of transgenic plants transformed by gene-gun bombardment and pollen tube injection were 60% and 42.8%, respectively. Transgenic lines with three to five copies accounted for 47.5%, 40% and 57.1%, respectively. In addition, in Agrobacterium-mediated T0 generation, transgenic lines with more than 5 copies accounted for 27.3%, while there was no transgenic plant with more than 5 copies in genetically modified T0 generation transformed by gene gun bombardment or pollen tube methods. These results provide some rationale for selection of transformation methods in crops transgene breeding.
