title: Somatic mutation-mediated evolution of herbicide resistance in the nonindigenous invasive plant hydrilla (Hydrilla verticillata).
abstract: Hydrilla (Hydrilla verticillata L.f. Royle) was introduced to the surface water of Florida in the 1950s and is today one of the most serious aquatic weed problems in the USA. As a result of concerns associated with the applications of pesticides to aquatic systems, fluridone is the only USEPA-approved chemical that provides systemic control of hydrilla. After a decrease in fluridone's efficacy at controlling hydrilla, 200 Florida water bodies were sampled to determine the extent of the problem and the biological basis for the reduced efficacy. Our studies revealed that hydrilla phenotypes with two- to six-fold higher fluridone resistance were present in 20 water bodies. Since fluridone is an inhibitor of the enzyme phytoene desaturase (PDS), the gene for PDS (pds) was cloned from herbicide-susceptible and -resistant hydrilla plants. We report for the first time in higher plants three independent herbicide-resistant hydrilla biotypes arising from the selection of somatic mutations at the arginine 304 codon of pds. The three PDS variants had specific activities similar to the wild-type enzyme but were two to five times less sensitive to fluridone. In vitro activity levels of the enzymes correlated with in vivo resistance of the corresponding biotypes. As hydrilla spread rapidly to lakes across the southern United States in the past, the expansion of resistant biotypes is likely to pose significant environmental challenges in the future.
authors.affiliation: USDA/ARS, Natural Products Utilization Research Unit, PO Box 8048, University, Mississippi 38677, USA.
authors.forename: Albrecht
authors.initials: A
authors.lastname: Michel
authors.forename: Renee S
authors.initials: RS
authors.lastname: Arias
authors.forename: Brian E
authors.initials: BE
authors.lastname: Scheffler
authors.forename: Stephen O
authors.initials: SO
authors.lastname: Duke
authors.forename: Michael
authors.initials: M
authors.lastname: Netherland
authors.forename: Franck E
authors.initials: FE
authors.lastname: Dayan
mesh_terms: D001483:Base Sequence; D015153:Blotting, Western; D017931:DNA Primers; D004351:Drug Resistance / Q000235:genetics*; D019143:Evolution, Molecular; D005431:Florida; D005618:Fresh Water; D006540:Herbicides / Q000378:metabolism*; D031321:Hydrocharitaceae / Q000201:enzymology / Q000235:genetics*; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D010088:Oxidoreductases / Q000037:antagonists & inhibitors / Q000235:genetics*; D010641:Phenotype; D011728:Pyridones / Q000378:metabolism*; D017422:Sequence Analysis, DNA
chemical_list: D017931:DNA Primers; D006540:Herbicides; D011728:Pyridones; C013351:fluridone; D010088:Oxidoreductases; C022398:phytoene dehydrogenase