Amid the excitement around being able to synthesise and edit DNA directly, it's easy to forget about some of the older methods for altering a genome. Methods that are more acceptable in places such as Europe when genetic modification has an extremely bad image.
For a new breed of potatoes designed to only produce a starch suitable for treating paper as well as foodstuffs, a team at the Fraunhofer Institute in Germany used good old-fashioned breeding to get the job done. Well almost. Good old-fashioned selective breeding with the foot hard on the accelerator pedal, using directed-evolution techniques to speed up the process of producing viable variants.
There's nothing particularly new about speeding up the process. Although protesters look upon direct genetic modification as 'unnatural', it's worth noting that plant breeders have used chemical and radiation treatment for some years to induce mutations that speed up the process of moving the candidate genomes into new territory. However, because these techniques do not carry the tag 'GM', nor do they carry the stigma.
"We are working here with natural principles. In nature, sunlight triggers changes in the genome, With chemistry, we accomplish the same thing - only faster," said Jost Muth of Fraunhofer IME in the release put together by the institute.
Normally, you have to wait after a burst of cross-breeding and mutation to see what crops develop. Not in this case. As soon as the seeds germinated, samples of the leaves were taken and their genomes analysed directly to see which mutants had picked up desired traits.
The researchers analysed 2748 seedlings to find a genome that had the genetic profile they were aiming for: the ability to produce amylopectin exclusively. Luckily the potato already has an amylopectin-production gene, which reduces the amount of mutation that the potato has to go through. However, the aim was to find a mutant that could shut off the production of sister starch amylose, which the 'Tilling' potato could. This avoids the need to purify the starch after harvesting and separation.
This autumn, the team grew about 100 tonnes of potatoes with the required genome, and without specialised GM trials. "Special measures aren't necessary, because the Tilling potatoes are totally normal breeds that contain no genetically modified material," said Muth.
The name Tilling is derived from the name the team gave to the process: targeting induced local lesions in genomes, a technique developed in the late 1990s in Seattle.