Chinese scientists have made a new breakthrough in hybrid potato breeding by using evolutionary genomics to identify deleterious mutations, which may help shorten the breeding process and generate more, and better, potato varieties.

The breakthrough, made by a research team from the Agricultural Genomics Institute in Shenzhen, associated with the Chinese Academy of Agricultural Sciences, was published online in the latest issue of the scientific journal Cell.

Potato is the most important tuber food crop, and one of the world's staple crops. Compared with other staple crops, potato needs less water and can be planted in a wide range of areas, says Wu Yaoyao, a key member of the research team.

"But breeding a new potato variety takes too long. The potato variety used for McDonald's fries was bred over 120 years ago," Wu says.

The main reason is that potato is a tetraploid, which means it has four sets of genomes, and depends on asexual propagation through tubers.

It has a long breeding cycle and low reproduction efficiency, while the tubers are also easily infected with diseases and prone to pests, Wu says.

The research team launched a "Ubiquitous Potato Project", aiming to transform potato reproduction from asexual to sexual, and from reliance on tubers to reliance on seeds, and guide potato breeding by using genomics and synthetic biology.

In order to breed consistent high-quality potato varieties, scientists need to obtain high homozygous inbred lines by continuous self-fertilization, so that hybrid commercial lines can be produced with consistent properties, Wu explains.

However, during the long-term asexual reproduction history of the potato, a large number of hidden deleterious mutations have accumulated. Once self-fertilized, these previously "invisible" mutations will unveil their adverse impact on the plants, such as reduced viability, sterility, lowered disease resistance and yield. This phenomenon, known as inbreeding depression, represents a major hurdle in hybrid potato breeding.