Scientists develop salt-resistant trees

The research by Arie Altman of the Institute of Plant Sciences and Genetics in Agriculture of the Hebrew University has special implications for countries like Israel, where farmers are being forced to increasingly salty water for irrigation because fresh-water supplies are already overexploited, the 9 September issue of The New Scientist reported. According to some estimates, more than half of the world’s agricultural land will become saline in the next half-century.

Altman’s team has isolated a protein called BspA that helps trees grow in salty conditions, which was discovered in a common European aspen, Populus tremula, which produces the protein when growing in salty soil. The researchers believe the protein may protect cells from high levels of salt by attracting water molecules and also by binding to other cell proteins, although they are still trying to ascertaining what the exact mechanism involved is.

The researchers managed to increase the aspens’ salt tolerance by giving them more copies of the gene for the protein. While normal aspens shed their leaves about five days after being exposed to very salty conditions, trees with extra BspA genes hang onto them for up to 10 days, Altman says. The team is now transferring the BspA gene to tobacco and tomato plants to see whether it can make these plants more salt-tolerant too.

However, Altman suspects that many plants already have the BspA gene. If so, it may not be necessary to genetically engineer the gene into crops. “Once you have a molecular probe for the gene you can use it also in traditional breeding techniques to speed up selection. By developing molecular tools you can screen out the trees in which the gene is being expressed the most,” he said.

The researchers are also trying to uncover the secrets of a tree that handles salt even better than the aspen. The Euphrates poplar, Populus euphratica, survives in the salty soil near the Avdat spring in Israel. While part of its tolerance may be due to BspA, Altman suspects that other factors are involved.

Altman’s work is significant, says Dorothea Bartels of the Max Planck Institute for Plant Breeding in Cologne and the University of Bonn, because discovering how a tree protects itself against high salt levels is a major advance as most work has focused on other plants.