Greenbug-Resistant Wheat Now Available

Greenbug resistance, bred into a new, hard red winter wheat germplasm line, is now available for use in developing new varieties of the crop.

Germplasm line N96L9970 should provide wheat breeders with a source of genes conferring resistance to five greenbug biotypes: B, C, E, G, and I, notes Robert Graybosch, a plant geneticist taking seed requests at the Agricultural Research Service's Wheat, Sorghum and Forage Research Unit in Lincoln, Neb.

The biotypes are different genetic subgroups of the aphid species Schizaphis graminum Rondani, which plagues cereal crops in both the northern and southern Great Plains. There, attacks by the tiny, sap-sucking pest cost wheat farmers $250 million annually in crop losses and pesticide expenses.

Resistant wheat is a cornerstone of integrated approaches to fighting the greenbug. But new cultivars are always needed because new biotypes of the pest can emerge to overcome them, according to Graybosch, who developed N96L9970 along with ARS scientist Dave Porter; James Peterson, formerly with ARS; and Jai-Heon Lee, a former doctoral scientist at the Nebraska Agricultural Experiment Station. The new wheat's broad-spectrum greenbug resistance comes from crosses of two earlier releases, GRS1201 and TAM202.

Based on 1997-98 tests at six sites in Texas and Nebraska, the new wheat's average grain yield was 50 bushels per acre versus about 38 bushels for GRS1201 and 56 for TAM202. In 2000 tests in five additional states, the new wheat averaged 40 bushels per acre versus 43 for Trego, 37 for Arapahoe, and 32 for Prowers–all used as commercial checks.

N96L9970's bread-making properties, dough strength, and protein content are similar to its "parents," GRS1201 and TAM202. The new wheat is adapted to conditions in the Great Plains region, is relatively tolerant of acidic soils, and has winter-hardiness similar to the commercial cultivar, TAM107, according to Graybosch.

Although susceptible to prevalent races of the leaf and stem rust fungus, N96L9970 has some resistance to wheat soilborne mosaic virus.

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