The potato is being increasingly incorporated into regular diets worldwide, even in Asian countries where rice has been the traditional staple food for millennia. However, unlike in the case of other major crop staples such as rice or wheat, efforts to breed new varieties of potatoes with higher yields have remained large unsuccessful.
A research team led by the Max Planck Institute for Plant Breeding Research is trying to solve this problem by implementing genome-assisted breeding of new potato varieties that will be more productive and resistant to climate change.
After shopping for potatoes on a market today, it is quite possible that the buyer will return home with a potato variety which was already available a century ago. This is not only testament to the enduring popularity of traditional potato varieties, but also highlights their lack of genetic variety. This can have dramatic consequences, such as the Irish famine of the 1840s, where for several years the only existent variety of potato crops was attacked by the newly emergent tuber blight and rotted in the ground.
The difficulty of breeding different potato varieties stems from this plant’s genetic peculiarity. Instead of inheriting one copy of every chromosome from both the father and the mother (as in the case of humans), potatoes inherit two copies of each chromosome from each parent, making them a tetraploid species.
This increased genetic complexity makes it highly challenging and time-consuming to generate new varieties with desired combinations of individual properties. Moreover, multiple copies of each chromosome also make the scientific reconstruction of the potato genome a highly challenging task.
The scientists from the Max Planck Institute have managed to overcome these longstanding problems and succeeded in generating the first full assembly of the potato genome through a simple and elegant trick. Rather than trying to differentiate the four – often very similar – chromosome copies from one another, the researchers sequenced the DNA of large numbers of individual pollen cells, which contain only two random copies of each chromosome. This helped them reduce the complexity of the problem and finally sequence the entire potato genome.
With this information, researchers can now identify more easily the genetic variants responsible for desirable or undesirable traits, and incorporate or exclude them during breeding. Improvements in potato breeding could have an enormous impact on delivering food security in the decades to come.