Sunflowers to Resist Parasitic
By Ben Hardin
June 6, 2000
An exotic weed, broomrape, so far
hasnt threatened U.S. sunflowers. But if quarantine efforts ever fail to
keep out the weed, scientists with USDAs
Agricultural Research Service are
tapping into genetically diverse sunflower relatives for backup protection.
Broomrape, Orobanche cumana, ranges from pink, orange-red,
purple to tan depending on its environment. Its a parasitic plant that
has no chlorophyll of its own, meaning it cant capture the suns
energy and make its own food. Instead, it steals nourishment from sunflower
roots, stunting or killing its host. Presently, it infests sunflower crops in
China and countries bordering the Mediterranean and Black Seas.
As new broomrape races evolve, international researchers, in customary
treadmill fashion, develop new sunflower lines with resistance genes. But ARS
scientists at Fargo, N.D., and their colleagues in el
Agricultura Sostenible CSIC, in Cordoba, Spain, have developed technology
called interspecific hybridization for sunflowers to avoid such
treadmills. Interspecific hybrids are crosses between cultivated
sunflowers and their distant relatives that were until now difficult--if even
possible--to cross. Some, nearly ready for release to the seed industry, are
not just resistant but immune to the broomrape race F, the newest race.
Broomrape became a progressively worse problem in Spain in the early 1990's.
Yields of sunflowers that were susceptible to races E and F often fell by 40 to
50 percent. Urgently, ARS and Spanish scientists conventionally derived seven
new resistant sunflower germplasms by crossing between
USDA lines and race E-resistant lines from
Russia, Romania and Turkey. New conventional hybrids from these lines are being
grown in Spain where they suffer yield losses of only 10 to 15 percent. And
researchers are finding that some individual plants from the seven parental
lines are resistant to race F.
ARS is USDA's chief research agency.
Scientific contact: Chao C. Jan and Jerry F. Miller, ARS Oilseeds
Research, Red River Valley
Agricultural Research Center, Fargo, ND, phone (701) 239-1319 (Jan), (701)
239-1321 (Miller); fax (701) 239-1349, firstname.lastname@example.org,