Superior Lettuces Fend Off Two Destructive Viruses
Wood February 12, 2007
Iceberg lettuce ranks as one of America's top-five favorite veggies.
However, this delicately flavored, slightly sweet crisphead and its
relativesthe romaine of Caesar salads, the softer textured leaf lettuces,
or the creamy butterheads like Boston and bibbare vulnerable to attack by
an impressive array of stealthy viruses and other natural enemies.
But five kinds of superior iceberg lettuces, developed several years
ago by Edward J. Ryder of the Agricultural Research Service (ARS), are today still holding their own
against attack by two of these daunting villains: big vein virus and lettuce
mosaic virus. A world-renowned lettuce breeder, Ryder, now retired, did the
work while based at the
Crop Improvement and Protection Research Unit in Salinas, Calif.
In 2004, the plants became the first publicly available iceberg
lettuces to boast resistance to both diseases. That's why lettuce breeders and
seed companies in California and elsewhere were quick to request samples of the
tiny black seeds.
Dual-resistance enhances survival because a lettuce field can easily
be besieged by both viruses at once. That's according to research
D. McCreight, who is in charge of ARS research at Salinas.
Equipping lettuce plants with genes that enable strong, natural
resistance is still the most economical, eco-friendly way to defend vulnerable
plants from the viral diseases.
ARS technician Bert J. Robinson (left) and plant
geneticist Edward J. Ryder (retired) harvest seeds of Lactuca
virosaa wild relative of cultivated lettucefor greenhouse and
field tests. Click the image for more information about it.
Lettuce big vein gets its name from the unhealthy, enlarged appearance
of veins in infected lettuce leaves. These lettuces may be bushy-looking or
The likely culprit? Mirafiori lettuce big vein virus, which makes its
way to lettuce roots via a soil-dwelling, funguslike microbe.
Lettuce mosaic, caused by a virus of the same name, results in
stunting and unattractive mottling. Green peach aphids can spread the virus as
they move about a lettuce field, sipping plant juices.
more about the research in the February 2007 issue of Agricultural
ARS is the U.S. Department of
Agriculture's chief scientific research agency.