Canadian scientists have created a plant that can grow in very salty conditions.

The researchers say the development could prove to be a major advance for world agriculture.

They believe the genetic modification (GM) technology could be used to engineer a variety of salt-resistant crops.

With one-third of the world's irrigated land contaminated by prohibitive levels of salt, this could dramatically increase global food production.

It is the sodium in salt that kills plants. In order for a plant to become salt-tolerant, it must either keep sodium ions from infiltrating its cells or find a place to store these ions where they cannot interfere with the plant's metabolism.

Salt-tolerant plants that use the second option "hide" the excess ions in a large space inside their cells called vacuoles.

Maris Apse and his colleagues from the University of Toronto engineered a plant called Arabidopsis thaliana to increase its uptake of sodium ions into these storage spaces.

Model organism

The results of the experiments, reported in the journal Science, show that the modified plant can thrive even when salt levels are twice the amount that would kill a normal crop of corn.

Arabidopsis thaliana was used because it is a standard laboratory workhorse. It is a member of the Brassicaceae, or Mustard family, which includes broccoli and cauliflower.

Like mice and flies, it is considered to be a "model" organism because it is easy to grow, has a short life cycle and makes lots of seeds. It also has a small genome compared to other higher plants like maize or wheat.

These features make it easier for scientists to see the success or failure of the changes they have introduced.

About 10m hectares of crops are lost each year because of the high level of salts in the water used for irrigation. Large areas of North and South America, Australia, Asia and Europe have experienced a serious decline in crop productivity this century as a result of this problem.

The researchers are confident that their methods can be used on other plants. Eventually they hope to see crops worldwide grown on land which was previously thought difficult or even impossible to farm.