The transfer of the long T-DNA (T-DNA and non-T-DNA) of a binary plasmid from
Agrobacterium into the rice genome was investigated at both molecular and genetic levels. Out of 226 independent transgenic plants, 33%
of the transformants contained non-T-DNA sequences. There was no major difference in the frequency of non-T-DNA transfer among
three
Agrobacterium tumefaciens strains.Four T1 plants containing a single putative long T-DNA insertion were selected 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 plasmid. This was further
confirmed by rescuing the intact binary plasmid from these 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 transgenic
rice for commercial production.
Key words Agrobacterium tumefaciens - T-DNA - Non-T-DNA - Long T-DNA transfer - Rice transformation
Received: 22 April 1999 / Accepted: 22 June 1999