title: Ethylmethanesulfonate saturation mutagenesis in Arabidopsis to determine frequency of herbicide resistance.
abstract: Plant resistance to glyphosate has been reported far less frequently than resistance to sulfonylurea and imidazolinone herbicides. However, these studies tend to be anecdotal, without side by side comparisons for a single species or natural isolate. In this study, we tested the frequencies of resistance of three herbicides in a controlled ethylmethanesulfonate (EMS) saturation mutagenesis experiment, allowing a direct comparison of the frequencies at which resistant mutant plants arise. The 100% growth inhibition dose rates of glyphosate, chlorsulfuron (a sulfonylurea herbicide), and imazethapyr (an imidazolinone herbicide) were determined for Arabidopsis. Populations of EMS-mutagenized M(2) seedlings were sprayed with twice the 100% growth inhibition dose of glyphosate, chlorsulfuron, or imazethapyr, and herbicide-resistant mutants were identified. Although there were no glyphosate-resistant mutants among M(2) progeny of 125,000 Columbia and 125,000 Landsberg erecta M(1) lines, chlorsulfuron resistance and imazethapyr resistance each appeared at frequencies of 3.2 x 10(-5). Given the observed frequency of herbicide resistance mutations, we calculate that there are at least 700 mutations in each EMS-mutagenized Arabidopsis line and that fewer than 50,000 M(1) lines are needed to have a 95% chance of finding a mutation in any given G:C base pair in the genome. As part of this study, two previously unreported Arabidopsis mutations conferring resistance to imidazolinone herbicides, csr1-5 (Ala-122-Thr) and csr1-6 (Ala-205-Val), were discovered. Neither of these mutations caused enhanced resistance to chlorsulfuron in Arabidopsis.
authors.affiliation: Cereon Genomics, Cambridge, Massachusetts, USA. gj32@cornell.edu
authors.forename: Georg
authors.initials: G
authors.lastname: Jander
authors.forename: Scott R
authors.initials: SR
authors.lastname: Baerson
authors.forename: Jebecka A
authors.initials: JA
authors.lastname: Hudak
authors.forename: Kathleen A
authors.initials: KA
authors.lastname: Gonzalez
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Gruys
authors.forename: Robert L
authors.initials: RL
authors.lastname: Last
mesh_terms: D017360:Arabidopsis / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development; D004351:Drug Resistance / Q000235:genetics; D005020:Ethyl Methanesulfonate / Q000494:pharmacology*; D005998:Glycine / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000378:metabolism; D006540:Herbicides / Q000008:administration & dosage / Q000378:metabolism*; D016296:Mutagenesis; D009154:Mutation; D009539:Nicotinic Acids / Q000008:administration & dosage / Q000378:metabolism; D013449:Sulfonamides; D014227:Triazines / Q000008:administration & dosage / Q000378:metabolism; D000097797:Glyphosate
chemical_list: D005020:Ethyl Methanesulfonate; D005998:Glycine; D006540:Herbicides; D009539:Nicotinic Acids; D013449:Sulfonamides; D014227:Triazines; D000097797:Glyphosate; C093630:imazethapyr; C037137:chlorsulfuron