New Waxy Spring Wheats Available

By Jan Suszkiw
January 30, 2003

Nineteen germplasm lines of waxy spring wheat jointly developed by Agricultural Research Service and university scientists are now available for breeding commercial cultivars with traits for high-amylopectin (HA) starch.

Starch rich in this glucose polymer has excellent water retention, digestibility, gelatinization and stickiness, features that make it useful as a sauce thickener, emulsifier and shelf-life extender. Most HA starch now comes from waxy corn and rice varieties. But waxy wheat starch also shows promise, especially as a flour blending ingredient. Ongoing research suggests it helps bread stay fresh and imparts desirable softness to certain Asian wet noodles, like Udon noodles.

The problem is that there are no existing commercial waxy spring wheats, only experimental ones, and these are poorly adapted to U.S. growing regions, according to plant geneticist Robert Graybosch, with ARS' Wheat, Sorghum and Forage Research Unit in Lincoln, Neb.

Graybosch teamed with ARS and state agricultural experiment station collaborators in Nebraska, North Dakota and Idaho to overcome the problem by crossbreeding Asian waxy wheat mutants with American spring wheats. The 19 lines resulting from their efforts each carry three copies of a gene mutation that inhibits the enzyme known as granule bound starch synthase. Without it, no amylose is produced.

Wheat starch is normally 75 percent amylopectin and 25 percent amylose, another type of glucose polymer. But amylose production in the 19 germplasm lines is all but suppressed, so the starch is virtually 100 percent amylopectin.

Sixteen of the new lines are classified as "hard" and three as "soft," based on kernel evaluation scores. Fifteen have red-colored grains, while the remaining four have either red or white grains. In field tests, the wheat lines' average grain yields ranged from a high of about 54 bushels per acre to a low of 39 bushels per acre. This compares to 51, 55, and 42 bushels per acre respectively for three commercial lines, Express, WPB926, and Klassic. The tests also reveal varying degrees of resistance to leaf and stem rust, two common fungal diseases.

ARS is the U.S. Department of Agriculture's chief scientific agency.