title: A novel P106L mutation in EPSPS and an unknown mechanism(s) act additively to confer resistance to glyphosate in a South African Lolium rigidum population.
abstract: Glyphosate resistance evolution in weeds is a growing problem in world agriculture. Here, we have investigated the mechanism(s) of glyphosate resistance in a Lolium rigidum population (DAG1) from South Africa. Nucleotide sequencing revealed the existence of at least three EPSPS homologues in the L. rigidum genome and identified a novel proline 106 to leucine substitution (P106L) in 52% DAG1 individuals. This mutation conferred a 1.7-fold resistance increase to glyphosate at the whole plant level. Additionally, a 3.1-fold resistance increase, not linked to metabolism or translocation, was estimated between wild-type P106-DAG1 and P106-STDS sensitive plants. Point accepted mutation analysis suggested that other amino acid substitutions at EPSPS position 106 are likely to be found in nature besides the P106/S/A/T/L point mutations reported to date. This study highlights the importance of minor mechanisms acting additively to confer significant levels of resistance to commercial field rates of glyphosate in weed populations subjected to high selection pressure.
authors.affiliation: Jealott's Hill International Research Centre, Syngenta, Bracknell, Berkshire RG42 6EY, United Kingdom. deepak.kaundun@syngenta.com
authors.forename: Shiv S
authors.initials: SS
authors.lastname: Kaundun
authors.forename: Richard P
authors.initials: RP
authors.lastname: Dale
authors.forename: Ian A
authors.initials: IA
authors.lastname: Zelaya
authors.forename: Giovanni
authors.initials: G
authors.lastname: Dinelli
authors.forename: Ilaria
authors.initials: I
authors.lastname: Marotti
authors.forename: Eddie
authors.initials: E
authors.lastname: McIndoe
authors.forename: Andrew
authors.initials: A
authors.lastname: Cairns
mesh_terms: D051229:3-Phosphoshikimate 1-Carboxyvinyltransferase / Q000235:genetics*; D005838:Genotype; D005998:Glycine / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D053209:Herbicide Resistance / Q000235:genetics*; D006540:Herbicides / Q000378:metabolism / Q000494:pharmacology; D008129:Lolium / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics; D009154:Mutation; D013019:South Africa; D000097797:Glyphosate
chemical_list: D051229:3-Phosphoshikimate 1-Carboxyvinyltransferase; D005998:Glycine; D006540:Herbicides; D000097797:Glyphosate