Plant biologists at the University of California, Davis, and the University of Toronto say the plant, which flourishes in salty irrigation water, offers hope that other crops can also be genetically modified for planting in many areas of the world that have salty irrigation water and salt-damaged soils.

Salty irrigation water upsets plants’ ability to take in water through their root cells, with highly saline conditions leading to dehydration as water is drawn out of the cells. To counter this effect, the researchers genetically engineered tomato plants that produce higher levels of a naturally occurring protein known as a ‘transport protein’ from arabidopsis, a relative of the cabbage.

The transport protein uses energy available in the cells to move salt into cell compartments called vacuoles, where it becomes isolated from the rest of the cell and unable to interfere with the plant’s normal biochemical activity. The genetically engineered tomato plants actually remove salt from the soil, and because their salt-storing activity occurs only in the leaves, the quality of the fruit is maintained.

The researchers say that the tomato plants grow and produce fruit in irrigation water that is up to about 50 times saltier than normal. In experiments the plants were irrigated with water having a salt concentration of 200 millimolar (Mm) of sodium chloride – more than one third as salty as seawater, with about 530 mM.

Eduardo Blumwald, a leader of the project from the University of California, Davis’ Department of Pomology, predicts that, with proper funding, it would be possible to develop commercially useful salt-tolerant tomato plants within three years. “Since environmental stress due to salinity is one of the most serious factors limiting the productivity of crops, this innovation will have significant implications for agriculture worldwide,” he commented.

According to US Department of Agriculture estimates, worldwide 39,000 square miles (100,000 sq km) – the size of Scotland and Wales combined – of once agriculturally productive land are being lost annually because of irrigation-induced salinity. Irrigation increases the salinity of soils and water by depositing soluble salts such as sodium, calcium, magnesium, potassium, sulphate and chloride that the water has picked up from the soils and rocks it has passed through.

It is estimated that crop production is limited by salinity on 40% of the world’s irrigated land and on 25% of irrigated land in the United States. This progressive loss of arable land is coupled with an expanding global population, which over the next 30 years is expected to require an increase in food production of 20% in developed countries and 60% in developing nations.

Although scientists have been trying to develop salt-tolerant crop varieties using selective breeding techniques throughout the past century, none of those efforts has proven successful until now.

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