Evidence of multiple complex patterns of T-DNA integration into the rice genome

The transfer of the long T-DNA (T-DNA and non-T-DNA) of a binary plasmid fr om Agrobacterium into the rice genome was investigated at both molecular ge netic levels. Out of 226 independent transgenic plants, 33% of the transfor mants contained non-T-DNA sequences. There was no major difference in the f requency of non-T-DNA transfer among three Agrobacterium tumefaciens strain s. Four TI plants containing a single putative long T-DNA insertion were se lected for Southern analysis. Three of them were confirmed to have a long T -DNA insertion with a size of greater-than-unit-length of the binary plasmi d. This was further confirmed by rescuing the intact binary plasmid from th ese plants. Our results suggest that long T-DNA transfer by rolling-circle replication from Agrobacterium to rice occurs frequently, and that the high frequency of non-T-DNA transfer should be considered when producing transg enic rice for commercial production.