title: Physiological and biochemical characterization of quinclorac resistance in a false cleavers (Galium spurium L.) biotype.
abstract: The physiological and biochemical basis for quinclorac resistance in a false cleavers (Galium spurium L.) biotype was investigated. There was no difference between herbicide resistant (R) and susceptible (S) false cleavers biotypes in response to 2,4-D, clopyralid, glyphosate, glufosinate-ammonium, or bentazon. On the basis of GR(50) (growth reduction of 50%) or LD(50) (lethal dose to 50% of tested plants) values, the R biotype was highly resistant to the acetolactate synthase (ALS) inhibitor, thifensulfuron-methyl (GR(50) resistance ratio R/S = 57), and quinolinecarboxylic acids (quinclorac R/S = 46), resistant to MCPA (R/S = 12), and moderately resistant to the auxinic herbicides picloram (R/S = 3), dicamba (R/S = 3), fluroxypyr (R/S = 3), and triclopyr (R/S = 2). The mechanism of quinclorac resistance was not due to differences in [(14)C]quinclorac absorption, translocation, root exudation, or metabolism. Seventy-two hours after root application of quinclorac, ethylene increased ca. 3-fold in S but not R plants when compared to controls, while ABA increased ca. 14-fold in S as opposed to ca. 3-fold in R plants suggesting an alteration in the auxin signal transduction pathway, or altered target site causes resistance in false cleavers. The R false cleavers biotype may be an excellent model system to further examine the auxin signal transduction pathway and the mechanism of quinclorac and auxinic herbicide action.
authors.affiliation: Department of Environmental Biology, University of Guelph, Guelph, Ontario, N1G 2W1 Canada.
authors.forename: Laura L
authors.initials: LL
authors.lastname: Van Eerd
authors.forename: Gerald R
authors.initials: GR
authors.lastname: Stephenson
authors.forename: Jacek
authors.initials: J
authors.lastname: Kwiatkowski
authors.forename: Klaus
authors.initials: K
authors.lastname: Grossmann
authors.forename: J Christopher
authors.initials: JC
authors.lastname: Hall
mesh_terms: D000040:Abscisic Acid / Q000096:biosynthesis; D002250:Carbon Radioisotopes; D002851:Chromatography, High Pressure Liquid; D004305:Dose-Response Relationship, Drug; D004351:Drug Resistance; D005030:Ethylenes / Q000096:biosynthesis / Q000494:pharmacology; D032061:Galium / Q000187:drug effects* / Q000502:physiology; D006540:Herbicides / Q000378:metabolism / Q000494:pharmacology; D011804:Quinolines / Q000378:metabolism / Q000494:pharmacology
chemical_list: D002250:Carbon Radioisotopes; D005030:Ethylenes; D006540:Herbicides; D011804:Quinolines; C489048:quinclorac; D000040:Abscisic Acid; C036216:ethylene