
Genetic Sleuthing To Track Microscopic Weed WarriorsBy Jan Suszkiw September 15, 2000Certain fungi and other microbes that attack invasive weeds offer
an environmentally friendly method of controlling the pesky plants without
resorting to traditional chemical herbicides. Now,
Agricultural Research Service scientists
have developed molecular sleuthing techniques to monitor these biocontrol
agents once released into the environment. ARS plant physiologist
Doug Luster says
their approach can both detect and identify a weed pathogens unique
genetic fingerprint using polymerase chain reaction (PCR),
amplified fragment length poymorphism (AFLP), DNA sequencing, molecular
marking, and other sensitive technologies. This has already resulted in DNA fingerprints for several
isolates, or types, of Myrothecium verucarria, a soil fungus that
kills morning glories. Morning glory is a weed that plagues sugarcane and other
crops. In field studies, spraying redroot- and smallflower-morning
glories with an oil-based carrier containing Myrothecium spores proved
as lethal to these weeds as the herbicide atrazine. Luster conducted the study
with ARS plant pathologist Dana Berner and agronomist Rex Millhollon. Though used in the lab, DNA fingerprinting is intended to help
scientists keep close tabs on the spore growth and spread, host range and
effectiveness of biocontrol pathogens like Myrothecium once theyve
been released to control weeds. The technology also allows researchers to
pinpoint and analyze particular DNA regions that can differentiate strains of
the same fungal family, such as Puccinia carduorum and P. jacea,
which attack musk thistle and yellow starthistle, respectively. In weed-infested crop fields or pastures, for example, scientists
hand-collect spore samples to identify weed pathogens and their whereabouts.
They also examine the spores under a microscope, subject them to biochemical
tests, and scrutinize infected plants for tell-tale disease symptoms. But the
results can be ambiguous. DNA fingerprinting offers genetic evidence linking a specific
microbial release to a specific disease seen in target weeds. It also reveals
the spread of biocontrol microbes and demonstrates their effectiveness in
reducing invasive weed populations. ARS is the U.S. Department of Agriculture's principal
research agency. Scientific contacts: Douglas G. Lusterand Dana K. Berner, ARS Foreign Diseases-Weed Science
Research Unit, Fort Detrick, Md., phone (301) 619-7344 [Luster], (301)
619-7339 [Berner], fax (301) 619- 2880, [email protected]; and Rex W. Millhollon,
ARS Sugarcane
Research Unit, Houma, La., phone (504) 853-3174, fax (504) 868-8369,
[email protected].
Story contacts Sugarcane Research Dana K Berner Jan R Suszkiw U.S. Department of Agriculture |