Around the world, a billion acres of agricultural land lay abandoned. In the United States, 15 million acres of cropland falls under this category. Decades of repeated irrigation and declining water quality have made much of this once-productive land too salty to support plant growth. Among the strategies to put this land back to use is to develop crops that can tolerate high-salinity soils.
Last week, Ceres, a biotechnology company in Thousand Oaks, CA, announced that it had developed a trait that allows several common crops to grow under highly saline conditions, even in seawater. Ceres researchers have tested the trait in Arabidopsis thaliana, rice, and switchgrass, a hardy perennial that’s used as a feedstock for making ethanol and other biofuels. “The fact that we’ve seen this very high-level salt tolerance in three different plant species gives us a high degree of confidence that this trait will recapitulate itself in other energy grasses as well,” says Ceres CEO Richard Hamilton.
The ability to grow energy crops, such as switchgrass, on marginal lands means that they wouldn’t have to compete for the best farmland. “The great opportunity is that we could use land unsuitable for food crops,” says Chris Field, director of the department of global ecology at the Carnegie Institution of Washington in Stanford, CA. But he cautions that there still could be competition for water, depending on where the crops are grown. “It depends on whether your land or the water is the limiting resource,” he says.
Indeed, irrigation is to blame for turning much of the world’s cropland fallow. When a field is irrigated, water evaporates, and salts get left behind in the soil. Over decades, the salts build up and degrade the soil’s quality. “There’s not only salinity now, but it’s getting worse,” says Mark Tester, a plant physiologist at the Australian Centre for Plant Functional Genomics at the University of Adelaide and director of the Australian Plant Phenomics Facility. “It’s inevitable, and this is compounded by the fact that the world’s water supplies are under increasing pressure. The salinity of these systems is being accelerated by the decreasing quality of water.”
Ceres is not revealing the gene used to convey the saline tolerance or its mechanism because it is filing for intellectual property protections on the discovery. But plants that grow in salty conditions generally do so through one of three different mechanisms: they form a barrier to prevent salt from entering the shoot, they actively pump out the salt that gets in, or they store the salt in vacuoles to isolate it from harming the plant cells.
Ceres’s next step is to test the plants in the field. “We have not observed at this point any increase in water requirements for the crop,” Hamilton says. “But before deploying it on a large scale, we have more testing that we want to do.”