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AsianScientist (Jul. 11, 2011) – Researchers in China, India, and New Zealand have joined a global consortium of scientists to sequence and analyze the genome of the potato (Solanum tuberosum L.) for the first time.

Potato is the world’s most important non-grain food crop and is essential to global food security. China and India are currently the world’s largest and third largest producers of potato, respectively, together accounting for almost a third of the world’s total production.

However, crop yield in China and India is relatively low compared to the U.S. and Europe: potato crop yield in the U.S. (44 metric tons per hectare) was almost three times higher than in China (15 metric ton per hectare), according to 2008 figures from the U.S. Department of Agriculture.

The lower crop yield in China and India has been attributed to low quality of seed potatoes: less than 20 percent of China’s potato acreage is covered by virus-free seed potatoes. As a result, there is enormous potential for increasing potato crop yields in Asia through genetic improvement.

The cultivation of new disease-resistant and high-yielding potato varieties is now made easier thanks to the decoding of the potato genome sequence by the Potato Genome Sequencing Consortium (PGSC), which has just published its findings in Nature.

Potato has been notoriously difficult to work with because of its tetraploid genome: four copies of each chromosome are present in each cell, making it difficult to breed improved varieties of potato. Furthermore, there is considerable variation among the four copies of each gene.

Despite decades of improvement work, the crop remains susceptible to pests, pathogens and inbreeding depression (where new potato lines are weaker than their parents).

Sequencing of the potato genome faced the same problem: work proceeded slowly as scientists were not able to piece together small fragments of the genome which they had sequenced due to the complexity of the potato genome.

The PGSC scientists overcame this obstacle by creating a simplified model of the potato genome: they used a variety of S. tuberosum which has only two chromosomes and derived a potato genome (referred to as DM) that had only two identical copies of the same chromosome (called a doubled monoploid).

In late 2009, the PGSC released a high quality draft sequence of the DM genome online. Since then, the PGSC has been refining the genome assembly while performing analysis and interpretation of the data. The genome assembly now covers 95 percent of the approximately 39,000 genes in potato, and was facilitated by new software developed by the BGI, one of the Chinese partners in the PGSC.

The most significant finding of the analysis is the identification of more than 800 disease-resistance genes, each of which has potential for use in fighting diseases such as the potato blight pathogen Phytophthora infestans, famous for causing the Irish potato famine of the 1840s.

“It will take researchers awhile to use the genome information to improve its agronomic traits, such as improved quality, yield, drought tolerance and disease resistance. But our most recent research will accelerate efforts to improve potato varieties and help close the gap in bringing a better potato to the farmer,” says Robin Buell, a plant biologist at Michigan State University, one of three co-leaders of the potato genome project.

The article can be found at: The Potato Genome Sequence Consortium (2011) Genome Sequence And Analysis Of The Tuber Crop Potato.

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Sources: Michigan State University, and The Potato Genome Sequencing Consortium.
Disclaimer: This article does not necessarily reflect the views of AsianScientist or its staff.