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Molecular Mechanisms of Flufenacet Resistance in Grass Weeds

dc.contributor.advisorvon Tiedemann, Andreas Prof. Dr.
dc.contributor.authorDücker, Rebecka
dc.titleMolecular Mechanisms of Flufenacet Resistance in Grass Weedsde
dc.contributor.refereevon Tiedemann, Andreas Prof. Dr.
dc.description.abstractengThis study aimed to elucidate the resistance mechanisms behind flufenacet resistance in Alopecurus myosuroides and Lolium spp. field populations. In a first step field populations of both species were screened in greenhouse bioassays and suitable biological material was selected for the investigation of the further studies using analytical and biochemical techniques as well as an RNA-Seq approach. In a screening with 50 A. myosuroides populations shifts in efficacy with resistance factors up to 7 were estimated and six populations from the Northern German Marshes were controlled by less than 90% with the field rate registered in Europe. The efficacy of several pre-emergence herbicides of different modes of action on sensitive populations and Northern German A. myosuroides populations with shift in flufenacet sensitivity was explored. While none of the herbicides registered in Europe were more effective on those populations than flufenacet, it was shown that particularly three-way-mixtures including flufenacet and the PDS inhibitor diflufenican increased the control of those populations significantly. The observed shift in flufenacet efficacy in A. myosuroides populations was comparably low, whereas resistance factors up to 61 were observed in a screening with 22 Lolium spp. field populations. For the first time, field relevant levels of flufenacet resistance were described in Lolium populations from France and the United Kingdom, but also in populations from the USA and the commercially available population VLR69 originating from Australia. The level of resistance correlated in case of both, A. myosuroides and Lolium populations with flufenacet degradation rates determined by HPLC. Similar detoxification pathways with glutathione conjugation as a first rate-limiting step were elaborated for both species based on metabolites identified by LC-MS/MS. The pathways suggest enhanced glutathione transferase activity as a main driver of the resistance observed in both species tested. The large differences in flufenacet resistance observed in Lolium population allowed the selection of biological material for an RNA-Seq study. By differential gene expression analysis of the transcriptomes of three sensitive and three flufenacet resistant Lolium populations, 11 differentially upregulated GSTs were identified. These findings were validated with four recombinant GST isoforms in vitro. The ability to detoxify flufenacet was confirmed with one tau class GST showing a high flufenacet turnover rate and one phi class GST with high sequence similarity to LrGSTF1 and a lower flufenacet turnover rate. These results suggest that flufenacet resistance in Lolium populations is caused by upregulation of at least one GST with high substrate-specificity to flufenacet in combination with a cumulative effect with at least one other GST with lower substrate-specificity to flufenacet. 84 Finally, none of the recombinant enzymes were able to degrade diflufenican and the ALS inhibitor mesosulfuron-methyl, suggesting that these herbicides are suitable for a combination with flufenacet in resistance management program, as no cross-resistance between these herbicides is
dc.contributor.coRefereeKarlovsky, Petr Prof. Dr.
dc.contributor.thirdRefereeGaines, Todd Prof. Dr.
dc.subject.engHerbicide resistancede
dc.subject.engEnhanced metabolismde
dc.affiliation.instituteFakultät für Agrarwissenschaftende
dc.subject.gokfullLand- und Forstwirtschaft (PPN621302791)de

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