New Lettuces Shrug Off Verticillium Wilt
By Marcia Wood
May 4, 2007
Fresh, crunchy iceberg lettuces sometimes
collapse like a deflated ball before they have a chance to form their familiar
firm, nicely rounded heads.
The cause? A disease known as verticillium wilt, which results from attack
by a soil-dwelling, root-rotting fungus called Verticillium dahliae. But
Agricultural Research Service (ARS)
scientists at Salinas, Calif., have teamed with
University of California-Davis
colleagues to produce the first-ever parent iceberg lettuces resistant to this
Lettuce is one of America's top five most popular vegetables. Iceberg
lettuce outsells all other kinds of this versatile leafy green.
Hayes, a research plant geneticist with the
U.S. Agricultural Research Station in Salinas, plant pathologist Krishna
Subbarao at UC-Davis, and their colleagues made seeds of the three new parent
lettuces available to researchers and plant breeders for the first time this
April. They published additional details about Verticillium wilt resistance in
a recent issue of Plant
Disease, a scientific journal.
More than a half dozen companies that produce vegetable seeds have requested
seed samples, according to Hayes. He noted that the parent lines are meant for
crossing with consumer-ready lettuces to boost the commercially grown lettuces'
resistance to verticillium wilt.
Breeding lettuces with natural resistance remains the most environmentally
friendly, economical and sustainable option for combating the fungus.
Verticillium wilt first showed up in some coastal California lettuce fields
in 1995. Researchers invested more than a decade in scrutinizing promising
lettuces in greenhouse and field tests before determining that the new parent
lines were ready for plant breeders everywhere to use.
The V. dahliae fungus infects roots of vulnerable plants, moving into
leaves and causing them to discolor, then to eventually wilt and die. The
fungus can also infect and kill hundreds of other kinds of plants, including
strawberries and tomatoes.
The California Lettuce
Research Board at Salinas, the California
State Department of Food and Agriculture at Sacramento, and others helped
fund the research.
ARS is the U.S. Department of
Agriculture's chief scientific research agency.