Southern blot showing copy numbers of the 16D10i-2 RNAi transgene in transformed potato lines and controls. For each plant line, 15 µg DNA was digested with 50 U Xba I and separated on a 0.8% agarose gel. 82-4, PA99N82-4 advanced breeding line; RB, wild type ‘Russet Burbank’; E34, empty vector control; D1 to D36, 16D10i-2 transgenic lines.