Single-copy transgenic wheat generated through the resolution of complex integration patterns

Genetic transformation of plants often results in multiple copies of the in troduced DNA at a single locus. To ensure that only a single copy of a fore ign gene resides in the plant genome, we used a strategy based on site-spec ific recombination. The transformation vector consists of a transgene flank ed by recombination sites in an inverted orientation. Regardless of the num ber of copies integrated between the outermost transgenes, recombination be tween the outermost sites resolves the integrated molecules into a single c opy. An example of this strategy has been demonstrated with wheat transform ation, where four of four multiple-copy loci were resolved successfully int o single copy transgenes.