Single-stranded DNA in the genetic transformation of wheat (Triticum aestivum L.): transformation frequency and integration pattern

Two non-linked marker genes (gus and bar) were co-introduced by microprojec tile bombardment into wheat cells. Four different DNA structures were compa red with respect to ability to integrate into the wheat genome: circular or linear (1) DNA as a single- or double-stranded plasmid (ss and ds, respect ively). In eight independent experiments, linearized DNA integrated in the ds or ss form with a high efficiency of up to 14% for 1-ssDNA. Molecular an alyses by Southern blotting showed that all DNA forms gave a similar compli cated integration pattern of the bar gene.