Simple Little Spud Helps Scientists Crack Potato's Mighty Genome

The Potato Genome Sequencing Consortium (PGSC), a team of scientists from institutions worldwide, including Virginia Tech, has published its findings in the Sunday July 10 online issue of the journal Nature. The successful sequencing of the genome of the world's third most important crop began when Richard Veilleux, who is the Julian and Margaret Gary Professor of Horticulture in the College of Agriculture and Life Sciences at Virginia Tech, wondered if the then new applications of plant tissue culture could be used to develop parent lines for hybrid potatoes. The concept was developed from his doctoral research, completed in 1981 at the University of Minnesota.

Most modern crop varieties are hybrids because hybrids are usually more vigorous than either parent. For example, with corn, a variety with desirable characteristics is self-pollinated for many generations, and the resulting seed is grown and crossbred with another similarly developed line with a different genetic background.

Since potatoes do not self-pollinate, Veilleux engineered inbred lines from immature pollen extracted from flower buds by using plant tissue culture. The result, potato plants with half the chromosomes of the parent, was completely sterile. "Their chromosomes have to be doubled, up to 24, which results in plants with completely identical pairs of chromosomes – a homozygous inbred line," said Veilleux. "In one cycle, you have accomplished what it takes five generations to do to create a maize inbred line the old-fashioned way."

Since that initial success, he has conducted years of basic research to improve these lines as building blocks for hybrid potato seed, supported by the U.S. Department of Agriculture through Hatch grants, among other funding. Over the years, he reported at international meetings on his progress toward developing a vigorous homozygous inbred line with desirable traits for hybrid parenthood.

By 2006, when an international team formed the Potato Genome Sequencing Consortium to attempt to sequence the genome of the potato, Veilleux's simple little spuds were poised for fame as the first potato to have its genome sequenced.

But first, the consortium, made up of groups at institutions from 14 countries, wanted to sequence a more popular and productive tuber, more resembling what is found on dinner tables worldwide. The consortium was working with a diploid variety that, like Veilleux's potato, has only 24 chromosomes. However, the pairs of chromosomes of the selected line are not identical; they carry variations of similar genes, resulting in thousands of differences in the base pairs – or rungs on the DNA ladder-- between chromosome pairs.