Cultivated potato (Solanum tuberosum) is a tough nut to crack in terms of plant breeding. It is a tetraploid crop, which means it has four sets of chromosomes and it is largely a heterozygous crop, which makes potato research and breeding through traditional crossbreeding a huge challenge. But help is on the way: by specific applications of genome editing, one or a few traits can be added to a commercial potato variety, hence the time-consuming and costly crossbreeding can be avoided. In recent years, genome editing through either TALEN or CRISPR‐Cas9 has been used to study and develop commercially important traits in potato and these are traits which would otherwise be very difficult and time consuming to include through traditional breeding technologies.
Now, before going into the benefits, first this: regular potato starch contains two types of molecules: amylopectin (approx. 80 per cent) and amylose (approx. 20 per cent). And it is the mix of these two and the resulting problems of starch retrogradation, that blocks optimal utilization of these two different polymers. Till now, to deal with this, the native starch needs to be chemically modified.
No foreign DNA
In the Swedish CRISPR Potato Starch project, amylopectin starch potatoes were developed by eliminating the amylose formation by knocking out the sole enzyme responsible for synthesis of amylose. This was done with the help of CRISPR (Clustered regularly interspaced short palindromic repeats) and CRISPR‐associated protein‐9 (CRISPR‐Cas9). The beauty of this project is that transgene‐free genome edited plants have been produced using the technique. For potato, a system that is yielding no foreign DNA integration would clearly be the preferred method, because it would allow the plant breeder to avoid any crossbreeding of this highly heterozygous tetraploid crop, which in addition could also result in inbreeding depression.
European Seed has reported on plant breeding innovation on many occasions in the recent past, with their tombstone cover (Oct. 2018) as a strong reminder of the dire straits they consider Europe to be in as a continent. To learn more about this project, they asked Hans Berggren from the Lyckeby Starch company and Mariette Andersson from the Swedish University of Agricultural Sciences for their take on their achievements.
Read more at european-seed.com