A new amino acid substitution (Ala-205-Phe) in acetolactate synthase (ALS) confers broad spectrum resistance to ALS-inhibiting herbicides.

James T Brosnan,Gregory K Breeden,Jose J Vargas,Stefan Tresch,Martin Laforest,Raphael A Aponte,Logan Grier

doi:10.1007/s00425-015-2399-9

Abstract

Main ConclusionThis is a first report of an Ala-205-Phe substitution in acetolactate synthase conferring resistance to imidazolinone, sulfonylurea, triazolopyrimidines, sulfonylamino-carbonyl-triazolinones, and pyrimidinyl (thio) benzoate herbicides.Resistance to acetolactate synthase (ALS) and photosystem II inhibiting herbicides was confirmed in a population of allotetraploid annual bluegrass (Poa annua L.; POAAN-R3) selected from golf course turf in Tennessee. Genetic sequencing revealed that seven of eight POAAN-R3 plants had a point mutation in the psbA gene resulting in a known Ser-264-Gly substitution on the D1 protein. Whole plant testing confirmed that this substitution conferred resistance to simazine in POAAN-R3. Two homeologous forms of the ALS gene (ALSa and ALSb) were detected and expressed in all POAAN-R3 plants sequenced. The seven plants possessing the Ser-264-Gly mutation conferring resistance to simazine also had a homozygous Ala-205-Phe substitution on ALSb, caused by two nucleic acid substitutions in one codon. In vitro ALS activity assays with recombinant protein and whole plant testing confirmed that this Ala-205-Phe substitution conferred resistance to imidazolinone, sulfonylurea, triazolopyrimidines, sulfonylamino-carbonyl- triazolinones, and pyrimidinyl (thio) benzoate herbicides. This is the first report of Ala-205-Phe mutation conferring wide spectrum resistance to ALS inhibiting herbicides.Electronic supplementary materialThe online version of this article (doi:10.1007/s00425-015-2399-9) contains supplementary material, which is available to authorized users.

Highlights

Resistance to acetolactate synthase (ALS) and photosystem II inhibiting herbicides was confirmed in a population of allotetraploid annual bluegrass (Poa annua L.; POAANR3) selected from golf course turf in Tennessee
Annual bluegrass populations resistant to photosystem II (PSII) inhibiting herbicides such as simazine and amicarbazone often have a point mutation on the psbA gene that codes for a Ser-264-Gly mutation on the D1 protein targeted by PSII inhibiting herbicides (Kelly et al 1999; Perry et al 2012)
Two gene isoforms encoding for ALS were detected within individual annual bluegrass plants in the POAAN-R3 population, both of which were expressed and contributed to ALS activity

Summary

Introduction

Resistance to acetolactate synthase (ALS) and photosystem II inhibiting herbicides was confirmed in a population of allotetraploid annual bluegrass (Poa annua L.; POAANR3) selected from golf course turf in Tennessee. Genetic sequencing revealed that seven of eight POAAN-R3 plants had a point mutation in the psbA gene resulting in a known Ser-264-Gly substitution on the D1 protein. St-Jean-sur-Richelieu, QC, Canada protein and whole plant testing confirmed that this Ala205-Phe substitution conferred resistance to imidazolinone, sulfonylurea, triazolopyrimidines, sulfonylamino-carbonyltriazolinones, and pyrimidinyl (thio) benzoate herbicides. This is the first report of Ala-205-Phe mutation conferring wide spectrum resistance to ALS inhibiting herbicides. Five other mutations on the psbA gene have been linked with weed resistance to PSII inhibiting herbicides (Beckie and Tardif 2012)

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Conclusion