Scientists, at the Ludwig-Maximilians-Universität München and the Max Planck Institute for Plant Breeding Research in Cologne, have decoded the highly complicated genome of the potato for the first time after over 20 years since the first release of the human genome.
Before the potato was recognized as edible, it was popular in Europe as an ornamental plant. The pollen in the large flowers is normally collected by bumblebees, which thus take over pollination. In the present study, genomes from individual pollen grains were analyzed to produce the first, complete map of a potato genome. Image Credit: Ulrich Pollmann (2022)
This technically challenging study sets the biotechnological foundation to speed up the breeding of stronger varieties—an aim of plant breeding for several years and an essential step towards global food security.
While buying potatoes today, it is highly possible that the consumers might be buying a variety that is available on the market for more than 100 years. Conventional potato breeds are well-known. And, however, this example also indicates a diversity lack among major potato varieties.
Nevertheless, the situation would change soon: scientists in the team of geneticist Korbinian Schneeberger generated the first complete assembly of a potato genome, paving the way for propagating new, healthy varieties:
“The potato is becoming more and more integral to diets worldwide including even Asian countries like China where rice is the traditional staple food. Building on this work, we can now implement genome-assisted breeding of new potato varieties that will be more productive and also resistant to climate change—this could have a huge impact on delivering food security in the decades to come,” the authors add.
Notably, the low diversity tends to make potato plants vulnerable to diseases. It can have severe consequences, for example, the most dramatic 1840s Irish famine where for many years almost complete potato crops rotted in the field and millions of people in Europe went through starvation just because the single-variety bred was not immune to recently emerging tuber blight.
Through the Green Revolution between the 1950s and 1960s, researchers and plant breeders efficiently achieved an increased yield of several major crop staples, such as wheat or rice. The potato, however, has not seen a comparable increase, and attempts to propagate new varieties with increased yields have largely remained a failure until today.
The cause for this is straightforward but has proven challenging to handle: rather than inheriting one copy of each chromosome from both the father and mother (just like in humans) potatoes inherit two copies of each chromosome from each parent, which make them a species that have four copies of each chromosome (also known as tetraploid).
Four copies of each chromosome also imply that there are four copies of each gene, thereby, making it highly difficult and time-consuming to produce new varieties that have a required combination of individual properties. On top of it, several copies of each chromosome also lead to the reconstruction of the potato genome, which is a far higher technical challenge than it was for the human genome.
The scientists have resolved this long-awaited challenge with an easy yet graceful trick. Rather than trying to differentiate the four chromosome copies from each other, which are often very similar, Korbinian Schneeberger and his co-worker Hequan Sun along with other colleagues overcome this issue by sequencing the DNA of huge numbers of individual pollen cells.
Unlike all other cells, every pollen cell comprises only two random copies of each chromosome. This enabled the entire genome sequence’s reconstruction.
An outline of the full DNA sequence of the potatoes grown has the capacity of largely enabling breeding. It has been a goal of both researchers and plant breeders for several years already. With this data handy, researchers can now more seamlessly detect whether gene variants are responsible for desirable or undesirable.
Sun, H., et al., (2022) Chromosome-scale and haplotype-resolved genome assembly of a tetraploid potato cultivar. Nature Genetics. doi.org/10.1038/s41588-022-01015-0.