Potato is an important crop for starch production, but there are limitations regarding the genetic variation of starch quality. In maize, starches with various properties have been available for a long time by mutational breeding. Amylose starch from potatoes differs from cereal amyloses in several functionally important aspects, such as a higher degree of polymerization. Areas of application in which the degree of polymerization is of importance include film forming and the polymeric properties of bioplastics. High-amylose potato lines have been achieved by inhibiting the two known branching enzyme forms of potato. A single inserted gene construct for the inhibition of both forms resulted in structural changes of the starch to levels of branching that were below the commercially available amylose standards of potato. The high-amylose potato lines were tested in multiple year field trials of agronomic performance and were used for the pilot plant production of starch. The introduced trait was confirmed to be stable over multiple years. The consequences of the modification were found to be an increased tuber yield, reduced starch content, smaller granule size and an increase in reducing sugars.