New Sunflower Lines Resist Fungal Disease

Three new germplasm lines are nowavailable for breeding elite sunflower hybrids that will resist downy mildewand produce oil rich in oleic fatty acid.

Agricultural Research Service (ARS)and North Dakota Agricultural Experiment Station (NDAES) scientists in Fargojointly developed, tested and released the new sunflower lines, dubbed HA 458,HA 459 and HA 460. Besides resistance to the fungus Plasmoparahalstedii, which causes downy mildew, the sunflower lines are beingreleased for their high levels of oleic fatty acid, which imparts desirableflavor, frying characteristics and other traits to oil.

The downy mildew fungus attacks sunflowers as both seedlings and matureplants, causing white cottony growths in the young plants, and large, clublikeroots and stunted growth in the older ones.

Until recently, sunflower growers kept mildew in check by planting seedtreated with metalaxyl, but the fungus has become resistant to this fungicide.Seed company breeders scrambled to develop downy-mildew-resistant hybrids,making these new germplasm releases invaluable. The emergence of virulent newdowny mildew races—from two before 2003 to 15 currently—has spurredthe need for hybrids with new sources of disease resistance, notesTomGulya. He's a plant pathologist in the ARS Sunflower Research Unit (SRU)at Fargo.

Gulya assisted SRU geneticist Jerry Miller, now retired, in developing HA458, HA 459 and HA 460 by crossing elite sunflower lines with wild sunflowerscollected from Idaho and Texas by SRU botanistGeraldSeiler over the past 20 years. Jack Rasmussen of NDAES collaborated withthem.

In repeated field and greenhouse tests at Fargo, all three lines resistedthe most virulent races of downy mildew fungus found in North America. HA 458and HA 460 also withstood a French race not yet found in America. Oil extractedfrom HA 458 and HA 459 averaged 86.5 percent and 87.3 percent oleic acid,respectively. Oil from HA 460 had 88.8 percent oleic acid.

SRU research leaderBradyVick is filling seed requests.

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