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Title: SOMATIC MUTATION-MEDIATED EVOLUTION OF HERBICIDE RESISTANCE IN THE NONINDIGENOUS INVASIVE PLANT HYDRILLA (HYDRILLA VERTICILLATA)

Author
item MICHEL, ALBRECHT - FORMERLY WITH USDA-NPURU
item Arias De Ares, Renee
item Scheffler, Brian
item Duke, Stephen
item NETHERLAND, MICHAEL - SEPRO CORPORATION
item Dayan, Franck

Submitted to: Molecular Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/7/2004
Publication Date: 8/8/2004
Citation: Michel, A., Arias De Ares, R.S., Scheffler, B.E., Duke, S.O., Netherland, M., Dayan, F.E. 2004. Somatic mutation-mediated evolution of herbicide resistance in the nonindigenous invasive plant hydrilla (Hydrilla verticillata). Molecular Ecology. 13:3229-3237.

Interpretive Summary: Hydrilla is a submersed invasive aquatic weed that was first introduced in Florida in the 1950's. This weed has had a major economic and ecological impact on lakes and waterways in the southern and pacific coastal states of the U.S. The primary method of control of hydrilla relies on the use of fluridone. The only herbicide available for systemic treatments of lakes. It was discovered that hydrilla has become resistant to the herbicide. Three different mutations have been identified in hydrilla, each providing a certain level of resistance to fluridone. The growth of this new strain of hydrilla is not affected by normal herbicide treatment.

Technical Abstract: Hydrilla (Hydrilla verticillata L.f. Royle), a nonindigenous submersed invasive aquatic weed, has had a major economic and ecological impact on lakes and waterways in the southern and pacific coastal states of the U.S., displacing native beneficial species and dramatically altering the ecosystems. Control of this weed is achieved primarily with nanomolar concentrations of the aquatic herbicide fluridone (Sonar®), a phytoene desaturase (PDS) inhibitor. Although considered unlikely to occur and never reported before in higher plants lacking sexual reproduction, distinct herbicide-resistant hydrilla populations have emerged in several locations. Three separate and independent somatic single-point mutations in the Arg304 codon of PDS have introduced Ser, Cys or His amino acid substitutions. Strikingly, all three single mutational events yielded herbicide-resistant PDS enzymes that maintained high catalytic activities. Thus, the ecological fitness of these hydrilla plants is apparently unaltered, enabling the rapid establishment of the resistant biotypes as dominant populations via the numerous means of vegetative propagation available to this aggressive weed. The lack of an environmentally acceptable alternative to fluridone for selective hydrilla management portends a widespread dissemination of these highly undesirable herbicide-resistant populations throughout aquatic ecosystems of the southern and pacific coastal states of the U.S.