Testing the possibility of horizontal transfer of introduced neomycin phosphotransferase(nptⅡ) gene of transgenic Eucalyptus camaldulensis into soil bacteria

The possible horizontal transfer of transgenes is of great concern when the transgenic plants are released into the field. To test the possible transfer of nptⅡ of transgenic trees into soil bacteria, we have used a stool DNA preparation kit to isolate the DNA from the soils in the rhizospheres of two non- and eight transgenic Eucalyptus camaldulensis trees. All the samples have provided the corresponding PCR products in the amplification with bacterial 16S RNA specific sequences, which indicates that the quality of the isolated DNA is adequate for amplification. The nptⅡ specific band has been amplified in three soil samples from the transgenic trees and even treated with filtration before the DNA isolation. This indicates that nptⅡ DNA exists in the soil, although it is still unclear whether the DNA was in the soil particles, in the soil bacteria or in the Agrobacterium contamination which was used for the E. camaldulensis transformation. Two approaches on isolation of bacterial DNA have been suggested for testing the possibility of this event in the future.