Scientists have entered a new era of agricultural biotechnology. No lo
nger is it sufficient merely to introduce a gene into a plant. The new
generation of technology requires that genes be introduced into agron
omically important crops in single copy and without the integration of
extraneous vector 'backbone' sequences and, perhaps, even selectable
markers. The expression of transgenes must be predictable and consiste
nt among numerous independent transformants. Recent research has more
clearly defined these problems and pointed the way to their solution.