Crunching New Data on Walnut Genes

Many things make a walnut wonderful—its rich taste, smooth texture, and, of course, its heart-healthy compounds. Now, ARS scientist Mallikarjuna Aradhya and his University of California-Davis colleagues have embarked on a 4-year study to identify walnut seedlings that have about a half-dozen traits valued highly by those who grow—and those who eat—walnuts. Those traits range from the plumpness of the kernel to the time of year the tree comes into leaf—a feature useful for avoiding frost damage and some diseases.

The scientists intend to home in on the traits via genetic markers, called “single nucleotide polymorphisms” or SNPs, that they will create.

Ideally, walnut breeders will use the markers in what’s known as “marker-assisted breeding.” The approach enables them to identify superstars while those trees are still very young. That’s a huge advantage when breeding English walnuts—America’s favorite. This species takes several years to begin bearing marketable nuts.

The collaboration will also yield several different kinds of genetic maps and, in all, is expected to provide the most comprehensive picture ever offered of walnut’s little-known genetics. More than 600 trees are being grown especially for the research, which is sponsored by ARS, the Folsom, California-based Walnut Marketing Board, and the university.

Aradhya says the markers will be invaluable for profiling the genetic makeup of the 1,680 walnut trees in the nation’s official walnut collection, located just outside of Sacramento, California. He’s a geneticist for this splendid array of the planet’s wild and domesticated walnuts, officially known as the ARS National Clonal Germplasm Repository for Tree Fruit and Nut Crops and Grapes.—By Marcia Wood, Agricultural Research Service Information Staff.

Mallikarjuna Aradhya is with the USDA-ARS National Clonal Germplasm Repository for Tree Fruit and Nut Crops and Grapes, 3201 Straloch Rd., Davis, CA 95616; phone (530) 752-9392, fax (530) 752-5974.

"Crunching New Data on Walnut Genes" was published in the September 2008 issue of Agricultural Research magazine.