Newly mapped tomato genome could yield tastier, hardier fruit

You might think you know all you need to know about the humble tomato, but now, you can truly get a look at what this fleshy fruit is made of thanks to the work of about 300 scientists from around the world who have identified almost all of the genesthat make up one commonvariety.

The consortium of scientists behind the International Tomato Genome Sequencing Projectannounced this week that it has sequenced almost all the genetic information ofa domesticated variety of tomato known as Heinz 1706, or Solanum lycopersicum.

Itsresultsare published in the journalNatureand on a specialwebsitecreated for the project, where the full genome can be more closely examined and analysed.

The consortium, which included scientists from the U.S., Germany, Japan, Spain Britain and nine other countries,said it sequenced more than 80 per centof the genome and managed to identify more than 90 per cent ofthe genes within it.

"For any characteristic of the tomato, whether it's taste, natural pest resistance or nutritional content, we've captured virtually all those genes," said James Giovannoni, who led the sequencing team.

Giovanni isscientist at thethe U.S. Department of Agriculture and at theBoyce Thompson Institute for Plant Research, basedat Cornell University in New York State, one of several institutions that participated in the sequencing project, which took eight years and cost millions of dollars.

New methods ofcultivation

An organism's genome is the complete set of itsinherited traits. In the Heinz 1706 tomato, the 35,000 genes that have been identified are arranged around a set of 12 chromosomes.

Theprecise identification of the genes that determine the fundamental traits ofthe tomato could enable scientists to change some ofthese traits in order to breed better-tasting, more pest-resistant tomatoes that produce higher yields.

"The sequencing and publication of the genomic sequence of this tomato establishes the molecular basis to study this species and to explore methods of cultivation to promote resistance to pests and water scarcity, and to facilitate growing this species in poorer and more arid regions," said the Institute for Research and Biomedicine in Barcelona, which worked on the genome,in a press release.

Breeding of other species in theSolanaceae family to which the Heinz 1706 belongs, such as eggplants and peppers, could also benefit from tomato's genetic information.

When comparing the genome of the domestic tomatoto that of a wild variety of tomato and to potatoes and grapes, the researchers found that on two occasions throughout itsmore than 100million years of evolution, the tomato genome had replicated itself in triplicate. This process allowed some of the genes to eventually take on new functions and likely affected the tomato's colour and texture.

A key crop

The tomato genome also holds clues to the genetic makeup of similar fruits that share some traits with the tomato, such as melons, bananas and strawberries, and will make the future sequencing of these fruits easier and cheaper.

So, why did the researchers choose to examine the tomato and not another fruit?

"Tomatoes are one of the most important fruit crops in the world," Graham Seymour, a professor of biotechnology at Nottingham University and a member of the consortium, told the Reuters news agency. "Both in terms of the volume that we eat and the vitamins, minerals and other phytochemicals that both fresh and processed tomato products provide to our diets."

In Canada, tomatoes are the most important greenhouse vegetable crop, withmore than200,000 tonnes of greenhouse tomatoesand about 500,000 tonnes of field tomatoesproducedeach year. The industry is worth about $500 million, as of 2004.