New Green Leaf Lettuce Leaves Leafminers in the
Lurch By Marcia
Wood December 1, 2008
Green leaf lettuces bring the rich color and pleasing texture of
their crinkly leaves to any garden salad. Besides being a favorite with salad
lovers, this kind of lettuce is also a top choice for destructive insects known
as leafminers, or Liriomyza langei.
To combat leafminers, Agricultural
Research Service (ARS) plant geneticists
Ryder (now retired) developed the world's first leafminer-resistant green
Adult leafminers, which are shiny black flies with a yellow triangle
on their backs, ruin leaves when they puncture them to feed on sap. Females add
to the damage when they lay tiny oval eggs inside the leaves. Wormlike larvae
hatch from the little eggs and, as they feed, create the mine-like tunnels for
which the pest is named.
In addition to its leafminer resistance, the attractive, robust new
lettuce can shrug off attacks by the virus that causes lettuce mosaic. This
disease, spread by green peach aphids (Myzus persicae), gives leaves a
sickly mottled or mosaic appearance, rendering the lettuce unmarketable.
Mou and Ryder, based at the
Crop Improvement and Protection Research Unit in Salinas, Calif., screened
more than 100 kinds of lettuce from ARS' Pullman, Wash.-based world collection
of lettuces, and from elsewhere, before selecting ARS' own "Salinas 88" lettuce
and a red leaf lettuce as parents for the new green leaf offspring. They put it
through seven years of laboratory, greenhouse and field tests, then made it
available to plant breeders and researchers earlier this year.
The lettuce, known as MU06-857, is the newest in a series of
first-rate iceberg, romaine, and leaf lettuces--and spinach--from the
internationally known plant-breeding program at Salinas. The lab's crisp,
crunchy iceberg lettuces, for example, have made iceberg the best-selling
lettuce in America. Nearly every iceberg lettuce grown in the United States
today owes at least some of its parentage to ARS' lettuce-breeding research.
ARS is a scientific research agency of the
U.S. Department of Agriculture.