Draft potato genome based on unique potato variety

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The Potato Genome Sequencing Consortium (PGSC), an international team of scientists from industry and academia in 14 countries, has released a draft sequence of the potato genome with the help of a Virginia Tech researcher. Richard Veilleux, professor of horticulture in the College of Agriculture and Life Sciences (www.cals.vt.edu/), contributed a unique phureja type of potato variety that accelerated the development of a blueprint for one of the world's most important food crops. Widely anticipated to assist scientists in improving the yield, quality, nutritional value, and disease resistance of potato varieties, the genome sequence will reduce the 10-12 years plant breeders need to develop new varieties today.

"The potato genome sequence will allow you to locate genes for any type of trait you want," Veilleux said.

Each copy of the potato genome consists of a dozen chromosomes and has a length of approximately 840 million base pairs, making it a medium-sized plant genome. Most lines of potato, such as the widely cultivated Solanum tuberosum, have four slightly different copies of the genome that can be traced to parents and grandparents, with some recombination occurring during sexual cycles. Although the PGSC began sequencing a potato species with such a complex genome, researchers turned to Veilleux for a unique line with only one copy of the genome (known as a "monoploid") to simplify and complement their work.

Veilleux has spent more than 25 years of his career investigating homozygous varieties of potatoes to create hybrid lines. An organism is homozygous when identical alleles of each gene are present in both chromosomes that pair during cell division. Homozygous organisms have less genetic information to analyze during the genome sequencing process, and they pass biological traits to all subsequent generations, making them "true-breeding organisms." On the other hand, most potato species are heterozygous – i.e., different alleles occupy the same gene position.

"The consortium turned to me for a homozygous line of potato," Veilleux explained. "Because potato suffers from 'inbreeding depression,' the weaker homozygous lines of potato are relatively rare and not cultivated in most parts of the world."

Thanks to a new computer program developed by the Beijing Genomics Institute, the potato genome assembly, which is publicly available on the PGSC website (www.potatogenome.net/), covers 95 percent of potato genes. Over the next six months, PGSC members will update the genome with an annotation of the genes, an analysis of when and where they are switched on and off, and a review of specific suites of genes critical to potato production. Research teams around the world are working to complete genome sequences for other plants in the Solanaceae family, which includes tomato, eggplant, petunia, tobacco, and pepper.

Suzanne Piovano, a lab specialist in the Department of Horticulture, has worked with Veilleux for the duration of his potato breeding research at Virginia Tech. Under Veilleux's supervision, 21 graduate students have earned their degrees based on some aspect of potato genetics.

Source: Virginia Tech