Watermelons Screened To Find Those That
Resist Two Major Diseases By
February 1, 2001
Watermelon lovers may someday have a lot to thank Amnon Levi
for: a better melon with built-in disease resistance.
Over the last two years, the Agricultural Research Service geneticist,
colleagues at the ARS
Vegetable Laboratory in Charleston, S.C., and researchers at
North Carolina State and
Clemson universities screened watermelons
to find those that are disease- and pest-resistant.
Fusarium wilt and gummy stem blight are the most
destructive watermelon diseases. The researchers are evaluating plant
introduction accessions stored at the U.S. Department of Agriculture
Collection Center in Griffin, Ga. They have also checked the cultivars for
resistance to silverleaf whiteflies that infest watermelon fields, damage the
crop and introduce plant viruses.
The value of the U.S. watermelon crop in 1999 was more than $268
million. In some wet years, Fusarium and gummy stem blight can cause up
to 15 percent yield loss to this high-value fruit.
The teams goal is to evaluate the genetic diversity of
watermelon germplasm and to develop watermelons with enhanced disease and pest
resistance. The scientists are constructing a genetic linkage map of watermelon
genes. The map will be useful in breeding programs, locating genes that confer
disease resistance and genes that affect fruit qualities like fruit shape and
size, flesh color and sugar content.
Watermelons are grown on 2 percent of the world area devoted to
the production of vegetables. Although many watermelon varieties have been
developed worldwide during the past two centuries, there is still an ongoing
need to improve watermelon fruit qualities and better meet market demands.
So far, the team has found wild watermelon accessions that are
resistant to whiteflies but not to gummy stem blight. The scientists are
continuing to screen the plants for resistance to Fusarium and gummy
stem blight diseases.
ARS is the chief scientific research agency of
Scientific contact: Amnon Levi, ARS, U.S. Vegetable
Laboratory, Charleston, S.C., phone (843) 556-0840, fax (843) 763-7013,