Backbone-free transformation of barrel medic (Medicago truncatula) with a Medicago-derived transfer DNA

In the present work, Agrobacterium tumefaciens-
mediated genetic transformation of the model legume
Medicago truncatula Gaertn. (barrel medic) was carried out
using the pSIM843 vector that contains a Medicago-derived
transfer DNA, delineated by a 25-bp sequence homologous
to bacterial T-DNA borders. The transfer DNA contains an
expression cassette for the nptII (neomycin phosphotransferase)
gene and is flanked by an expression cassette for the
backbone integration marker gene ipt (isopentenyl transferase).
Our results demonstrate that the Medicago-derived
RB-like elements efficiently support DNA mobilization
from A. tumefaciens to M. truncatula. Kanamycin-resistant
shoots with normal phenotype and ipt-shooty lines were
recovered at a frequency of 11.7 and 7.8%, respectively.
Polymerase chain reaction (PCR) analyses demonstrated
that 44.4% of the independent transgenic lines were backbone-
free and evidenced the occurrence of backbonetransfer events