Sj. Dalton et al., THE EFFECT OF SELECTION PRESSURE ON TRANSFORMATION FREQUENCY AND COPYNUMBER IN TRANSGENIC PLANTS OF TALL FESCUE (FESTUCA-ARUNDINACEA SCHREB), PLANT SCI, 108(1), 1995, pp. 63-70
Protoplasts of Festuca arundinacea (Schreb.) were transformed with pla
smids containing a hygromycin resistance gene, and plants were regener
ated under a variety of selection regimes. Plant regeneration was high
est under discontinuous selection, but resulted in the production of s
ignificant numbers of escapes. Continuous selection at low concentrati
ons of hygromycin produced the highest numbers of transgenic plants wi
thout escapes. Transgene copy numbers for 83 plants were estimated and
related to the selection regime under which the plants were regenerat
ed. Discontinuous application of hygromycin produced a high proportion
of plants containing two or fewer inserted copies of the transgene (8
7%), as did low levels (50 mg . l(-1)) of continuous selection on hygr
omycin (88%). Continuous selection at high concentrations of hygromyci
n biased selection in favour of multiple-copy containing plants. Using
a plasmid encoding a hygromycin phosphotransferase enzyme of higher s
pecific activity (pROB5) resulted in the production of significantly m
ore transgenic plants.