Sunflowers—today known for their tasty, crunchy seeds and a healthful salad oil—might tomorrow gain fame as a source of premium rubber. That's the plan of scientists who have joined forces to improve the quality and quantity of latex from sunflower plants.
Latex is made up of rubber particles surrounded by water and other plant compounds. It is a higher value product than solid rubber. As rubber factories of the future, lanky sunflowers would reduce America's dependence on imported natural rubber and on synthetic rubber made from petroleum. The United States imported about 1.2 million tons of natural rubber—worth about $1 billion—in 2000. Although synthetic rubber can be substituted in some instances for natural rubber, high-performance products such as airplane tires require natural rubber.
"More than 2,500 species of plants produce natural latex," says ARS plant physiologist Katrina Cornish at Albany, California. "But few of them have the traits we want. In particular, most are small, grow too slowly, or aren't suitable for being cultivated in uniform stands—or monocultures. And they don't produce enough latex, or the latex they produce is not high quality.
"In contrast, sunflowers grow large rapidly and do well in monocultures. Although the quantity and quality of latex from sunflowers is not yet good enough for commercial use, we expect to improve it further through genetic engineering," Cornish adds. She is part of the ARS Crop Improvement and Utilization Research Unit of the Western Regional Research Center in Albany.
Cornish and colleagues are experimenting with several different types or lines of sunflowers. "We are especially interested in lines that produce the highest amounts of latex in stems and leaves—as opposed to flower heads," Cornish points out. "That's because it's impractical to separate latex in the flower head from oil and other components. We're also focusing on lines that flourish in northern, temperate climates, where most of the U.S. sunflower crop is grown."
At Albany, Cornish is delineating the physical characteristics of sunflower candidates' latex and comparing them to those of latex taken from two other natural sources—the Brazilian rubber tree and a desert shrub, guayule. (See Agricultural Research, May 1999 and April 2002.)
Cornish will insert laboratory-built genes for latex production into sunflower tissue. Next, she will test the tissue to determine whether the new genes are working inside the sunflower's cells. Later, greenhouse and field tests will identify the gene-engineered plants that produce the highest amounts of the best quality latex. In experiments after harvest, Cornish and co-researchers will determine how to preserve sunflower latex while it's in storage, awaiting processing.
Cornish is a world authority on how plants produce rubber. She is doing the sunflower project with colleagues from Colorado State University and Oregon State University.—By Marcia Wood, Agricultural Research Service Information Staff.
This research is part of Quality and Utilization of Agricultural Products, an ARS National Program (#306) described on the World Wide Web at http://www.nps.ars.usda.gov.
"Sunflower Rubber?" was published in the June 2002 issue of Agricultural Research magazine.