story to find out more.
JLynn Howell (right) homogenizes hydrilla samples while plant
physiologist Franck Dayan observes the presence of carotenoids (the yellow
layer in the test tube) that indicate the plant is herbicide resistant.
Click the image for more information about it.
Hydrilla's Resistance to Herbicide Gives
Scientists a New Challenge By
Luis Pons November 1, 2005
Scientists with the Agricultural Research Service (ARS) and a private firm have encountered a
troubling turn of events in the fight against an invasive weed that's choking
many waterways in the southeastern United States.
The researchers--at ARS'
Products Utilization Research Unit in Oxford, Miss., and with
SePRO Corp., a Carmel, Ind.-based
plant-protection management firm--found that a form of hydrilla (Hydrilla
verticillata) has developed resistance to fluridone, the most effective
herbicide against it.
They've pegged the resistance to a gene mutation in the dioecious,
female form of hydrilla. So far, this mutation has been found only in hydrilla
inhabiting several Florida lakes. A monoecious hydrilla--a form that has both
male and female flowers on the same plant--that first appeared in the middle
Atlantic states has, to date, not shown resistance to the herbicide.
The ARS studies in Oxford were conducted by plant physiologist
Dayan and molecular biologists
Scheffler and Albrecht Michel. Scheffler now leads ARS' Mid-South Area
Genomics Laboratory in Stoneville, Miss., while Michel is no longer with ARS.
Hydrilla's ability to thrive even in adverse conditions has led
researchers to dub it "the perfect aquatic weed." Rooted in bottom sediments,
it grows long, thin stems that rapidly reach the water's surface and form a
thick mat. It was introduced to the United States from Southeast Asia in the
1950s near Tampa, Fla.
According to Dayan, the resistant hydrilla has increased treatment
costs for affected lakes.
The new discoveries have spurred government and SePRO scientists and
aquatic systems managers to seek additional environmentally friendly ways to
combat the weed. Biological agents being studied for controlling hydrilla
include some insects and the fungal pathogen Mycoleptodiscus terrestris,
which when used with fluridone seems to increase hydrilla's susceptibility to
more about this research in the November 2005 issue of Agricultural
ARS is the U.S. Department of
Agriculture's chief in-house scientific research agency.