New Sunflower Lines Resist Fungal Disease
By Jan Suszkiw
August 3, 2007 Three new germplasm lines are now
available for breeding elite sunflower hybrids that will resist downy mildew
and produce oil rich in oleic fatty acid.
Agricultural Research Service (ARS)
and North Dakota Agricultural Experiment Station (NDAES) scientists in Fargo
jointly developed, tested and released the new sunflower lines, dubbed HA 458,
HA 459 and HA 460. Besides resistance to the fungus Plasmopara
halstedii, which causes downy mildew, the sunflower lines are being
released for their high levels of oleic fatty acid, which imparts desirable
flavor, frying characteristics and other traits to oil.
The downy mildew fungus attacks sunflowers as both seedlings and mature
plants, causing white cottony growths in the young plants, and large, clublike
roots and stunted growth in the older ones.
Until recently, sunflower growers kept mildew in check by planting seed
treated 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 new
downy mildew races—from two before 2003 to 15 currently—has spurred
the need for hybrids with new sources of disease resistance, notes
Tom
Gulya. He's a plant pathologist in the ARS Sunflower Research Unit (SRU)
at Fargo.
Gulya assisted SRU geneticist Jerry Miller, now retired, in developing HA
458, HA 459 and HA 460 by crossing elite sunflower lines with wild sunflowers
collected from Idaho and Texas by SRU botanist
Gerald
Seiler over the past 20 years. Jack Rasmussen of NDAES collaborated with
them.
In repeated field and greenhouse tests at Fargo, all three lines resisted
the most virulent races of downy mildew fungus found in North America. HA 458
and HA 460 also withstood a French race not yet found in America. Oil extracted
from 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 leader
Brady
Vick is filling seed requests.
ARS is the U.S. Department of
Agriculture's chief scientific research agency.
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