Genetically engineered tomato trols increased production of the transport grows in salty water protein was taken from Arabidopsis, a relative Plant biologists at UC Davis and the Univer- of the cabbage that is commonly used in plant sity of Toronto have developed a genetically research. engineered tomato plant that thrives in salty The transport protein uses energy available irrigation water. Their unprecedented feat in the cells to move salt - in the form of so- may help growers worldwide to cope with the dium ions - into compartments within the ancient and eventually devastating dilemma of cells called vacuoles. Once the salt is stashed salt buildup, or salinity, in irrigated soils. inside the vacuoles it is isolated from the rest UC Davis pornologist Eduardo Blumwald of the cell and unable to interfere with the and colleagues have demonstrated that the to- plant’s normal biochemical activity. matoes will grow and produce fruit in irriga- The genetically engineered salt-tolerant tion soil and water about 50 times saltier than plants actually remove salt from the soil. Be- normal. The plants were irrigated with water cause their salt-storing activity occurs only in having a salt concentration of 200 millimole the plants’ leaves, the quality of the tomato (mM) sodium chloride, about one-third as fruit is maintained. Blumwald predicts that it salty as seawater. may be possible to develop commercially use- “Since environmental stress due to salinity ful salt-tolerant tomato plants within 3 years. is one of the most serious factors limiting the productivity of crops, this innovation could have significant implications for agriculture Nearly 25 million acres worldwide,” Blumwald says. The research, of formerly productive much of which was done at the University of agricultural land is lost annually worldwide to Toronto, will continue at UC Davis; the most irrigation-induced recent findings were published in the August salinity. When grown in issue of Nature Biotecltnology. salty water with 200mM concentrations of Irrigation increases the salinity of soils by sodium chloride, wild- depositing soluble salts such as sodium, cal- type tomatoes shrivel up cium, magnesium, potassium, sulfate and and die, top, while a chloride, which the water picks up as it passes genetically engineered salt-tolerant tomato through soils and rocks. Worldwide an esti- plant thrives, bottom. mated 24.7 million acres of once agriculturally productive land - about one- fifth the area of California - are lost annually because of irrigation-induced salinity, ac- cording to the U.S. Department of Agriculture. Crop production is already limited by salinity on 40% of the world’s and 25% of the United States’ irrigated land. Genetically engineered Salty irrigation water upsets the ability of fruit grown in saline plants to take up water through root cells. If conditions, right, is of similar quality to that salt concentrations in the soil are very high, produced under normal water flow into the plant is actually reversed conditions, left. and the plant dehydrates and dies. To counter this effect, Blumwald and Hong- Xia Zhang of University of Toronto genetically engineered tomato plants that produce higher levels of a naturally occurring protein known as a ”transport protein.” The gene that con-

4 CALIFORNIA AGRlCULTlJRE, VOLUME 55, NUMBER 5