Ethylmethanesulfonate saturation mutagenesis in Arabidopsis to determine frequency of herbicide resistance |
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Authors: | Jander Georg Baerson Scott R Hudak Jebecka A Gonzalez Kathleen A Gruys Kenneth J Last Robert L |
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Institution: | Cereon Genomics, Cambridge, Massachusetts, USA. gj32@cornell.edu |
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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. |
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