ARS News Service
Agricultural Research Service, USDA
Erin Kendrick-Peabody, (301) 504-1624, ekpeabody[at]ars.usda.gov
December 22, 2003
To spot early
signs of Cercospora leaf spot disease in sugar beets, an Agricultural Research
Service scientist has developed a method to detect the culprit fungus,
Cercospora beticola, early on--even in plants lacking any symptoms.
These symptoms include ash-colored spots and dark blotches. When these symptoms
appear on the leaves of a sugar beet plant, beet farmers suspect Cercospora leaf
spot. The fungus behind this foliar disease reduces both
yield and sugar content in sugar beets, the plants that provide the United
States with about half of its sugar supply.
But the fungal pathogen doesn't always announce itself, especially as it moves
from the soil to the beets' leaves.
Plant pathologist Robert T. Lartey, along with three ARS colleagues, created the
pathogen-detecting protocol. It uses real-time polymerase chain reaction (PCR),
a technique for rapidly producing many copies of a fragment of DNA so that
specific genes can be identified. ARS' John J. Weiland, TheCan Caesar-TonThat
and Sarah Bucklin-Comiskey assisted Lartey, who is at the agency's Northern
Plains Agricultural Research Laboratory in Sidney, Mont.
The new protocol drastically reduces the time needed to isolate and subculture
the pathogen and to purify the DNA for amplification, from a task traditionally
requiring up to two weeks to one that can be accomplished in a single day.
The technique relies on a kit developed and sold by Sigma-Aldrich, a St.
Louis-based biotech company. The PCR method can be used to determine how
early in the growing season C. beticola may infect nearby plants, and from there
spread to sugar beets. Early detection provides a better forecasting of the
disease and allows for more precise fungicide applications.
Lartey anticipates the use of the new protocol for disease management in a range
of plant pathogen applications. While PCR is widely used to detect fungal,
bacterial and viral diseases of crops, for many pathogens there still is no
rapid and sensitive test. Scientists are already interested in the technique for
identifying diseases in wheat.
ARS is the U.S. Department of Agriculture's chief scientific research agency.
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