Group 4 Resistance and the North American Kochia Action Committee

Todd Gaines

28 February 2018

Herbicide Resistance Summit

CSU Weed Science

Sorgoleone secretion Natural Phytotoxins

Biochemistry

Herbicide resistance Weed Genomics

Dr. Todd Gaines Dr. Franck Dayan

Dr. Phil Westra

Dr. Scott Nissen

Aquatic weeds Radio-labeled herbicides

Field crops Kochia management

Group 4/O: Synthetic Auxins

Global use 2014

Reviewed by Busi et al 2018, Pest Manage Sci

Group 4/O: Synthetic Auxins

162 mil ha 50 mil ha

Reviewed by Busi et al 2018, Pest Manage Sci

Global use 2014

evolution

Occurrence of resistance to Group 4 was initially slower Increasing recently What about agronomic impact?

Reviewed by Busi et al 2018, Pest Manage Sci

Major Group 4 Resistant Weeds • Kochia, US, Canada (Kochia scoparia): dicamba • Waterhemp, US (Amaranthus tuberculatus): 2,4-D • Wild radish, Australia (Raphanus raphanistrum): 2,4-D • Prickly lettuce, US (Lactuca serriola): 2,4-D • Corn poppy, Europe (Papavar rhoeas): 2,4-D • Smooth pigweed, Argentina (Amaranthus hybridus): 2,4-D,

dicamba • Others in Canada: spotted knapweed (clopyralid, picloram);

hempnettle (dicamba, fluroxypyr, MCPA); false cleavers (quinclorac); wild mustard (2,4-D, dicamba)

How can a plant be resistant to Group 4?

Metabolism

Transport

Target-site 1) TIR1/AFB 2) Aux/IAA

Roundup Ready Xtend Dicamba metabolism Enlist 2,4-D metabolism

How auxins work

Group 4 herbicides turn on plant growth pathways Lose regulation of growth à plant death Critical pathway – resistance may be rare

Reviewed by Busi et al 2018, Pest Manage Sci

Wild radish work at UWA (Goggin et al) shows reduced 2,4-D translocation

Mechanisms largely unknown

Target-SiteDicambaResistanceinKochiascoparia

Eric Patterson1, Dean Pettinga1, Sherry LeClere2, Junjun Ou3, Mithila Jugulam3, Doug Sammons2, Phil Westra1, Todd Gaines1

1BioagriculturalScienceandPestManagement,ColoradoStateUniversity,FortCollins,CO2Monsanto,St.Louis,MO

3Agronomy,KansasStateUniversity,Manha&an,KS

Dicamba: 3,6-dichloro-2-methoxybenzoic acid

Dicamba•  Synthe2cauxinherbicideintroducedin1967•  Resistancefirstdocumentedin1990

•  8unique,documentedcasesofK.scoparia(14total;Heap,2016)•  Usedinchemicalfallowrota2ons•  Transgenicdicamba-resistantcrops

•  RoundUpReadyXtend

Indole-3-Ace2cAcid(IAA)

2,4-Dichlorophenoxyacetic acid (2,4-D)

3,6-dichloro-2-methoxybenzoicacid(Dicamba)

Kochia scoparia •  Annualdicottumbleweed•  Earlyemergence•  Prolificseedproduc2on•  Outcrossing–highgene2cdiversity•  Herbicide-resistant

•  ALSinhibitors•  Atrazine•  Glyphosate•  Synthe4cAuxins(dicamba)

•  Varanasietal.(2015)PestManagSci

Eric Patterson, PhD student

Dicamba Insensi@vity in CO-R

DicambaInducedEthyleneproduc2oninthesensi2velinePe_ngaetal.(2018)PestManagSci.

TranscribedbyknownARFtranscrip2onfactor

Target Site Muta@on in an Aux/IAA

The“degron”

Sherry LeClere, Monsanto

Aux/IAA16s interac@ons with AFBs and TIR1

Sherry LeClere, Monsanto

Mutation à dicamba does not turn on growth pathways

KASP Assay for the Aux/IAA Muta@on SNP_posi4on Primer_ID Sequence:SNP=(Allele1/Allele2)

379and380 KsAUX_IAA379+380 AATTGTTTGTTCTTCAGGACACAAGTTGTA(GG/AA)TGGCCACCCGTTAGAGGGTTCAGGAAGAACATCGTCGCGGCCACAAGAAGACGTCCGATGATCAAACTGATCAGAAGGCTTCT

0%

20%

40%

60%

80%

100%

0% 20% 40% 60% 80% 100%

Fam(Suscep2

ble)

Hex(Resistant)

CO-SCO-RNTC

0%

20%

40%

60%

80%

100%

0% 20% 40% 60% 80% 100%

Fam(Suscep2

ble)

Hex(Resistant)

CO-SCO-RM32J6J25J27NTC

0%

20%

40%

60%

80%

100%

0% 20% 40% 60% 80% 100%

Fam(Suscep2

ble)

Hex(Resistant)

NTCCO-SCO-RKS-SKS-R

OriginalColoradoPopula2ons Addi2onalColoradoPopula2ons KansasPopula2ons

Some dicamba-R populations have mutation Others don’t have it – multiple mechanisms

Dicamba resistance in kochia

•  Target-site mutation in kochia Aux/IAA16 •  Prevents dicamba binding

•  Fitness cost shown for this mutation – fewer seeds, slower growth •  Outcompeted by S kochia in absence of dicamba

• Mutation not in all Dicamba-R populations à Likely at least two different mechanisms

•  Surveys in Colorado - ~30% of populations are dicamba resistant

Cytochrome P450 Modulates 2,4-D Metabolic Resistance in Waterhemp

(Amaranthus tuberculatus) Marcelo Figueiredo, Anita Kuepper, Darci Giacomini, Greg Kruger, Patrick Tranel, Phil Westra, Franck Dayan, Scott Nissen, Todd Gaines

COLORADO STATE UNIVERSITY THE COLLEGE OF AGRICULTURAL SCIENCES Bioagricultural Sciences and Pest Management Department

Herbicide Metabolism • Many herbicides naturally selective in crops due to metabolism

• Some insecticides (e.g., malathion) inhibit herbicide metabolism •  Co-application can result in crop injury

• Malathion inhibits cytochrome P450 •  Enzyme that can oxidize some herbicides

Malathion and 2,4-D on waterhemp

R R Mal

S S Mal

Estimated effective dose: 50% Estimate (g ai ha-1) Std. Error

R 192 44 R Mal 24 8 S 21 5 S Mal 23 3 g a i ha-1 – 28 Days After Treatment

Time (min) Time (min)

Malathion and 2,4-D metabolism

A – COLUMNS a – lines

Time (min) Time (min)

2,4-D rapidly metabolized to inactive form

Malathion prevents metabolism à P450

Summary of Synthetic Auxin Resistance •  Target-site resistance: Aux/IAA mutation in Kochia scoparia for

dicamba resistance •  Fitness cost – S kochia outcompetes R in absence of dicamba

• Non-target-site resistance: Enhanced 2,4-D metabolism in Amaranthus tuberculatus, likely P450 mediated

•  Fitness cost?

•  Increasing use of 2,4-D and dicamba in USA and soon S. America

•  Very important herbicides – resistance management is critical

North American Kochia Action Committee • University, government, and industry scientists • USA and Canada • Develop and coordinate a strategy for herbicide-resistant kochia

research (including funding mechanisms) • Facilitate industry/ government/ university collaborations • Communication and Extension • Stewardship guidelines, technical bulletins and best

management practices • Assist in integrated management of HR kochia and in sustaining

existing management tools

Funding and Acknowledgements

Steve Bowe John Frihauf Leo Charvat

DeanPe_nga,EricPa&erson:RNA-SeqandMolecularBiology

JunjunOu,MithilaJugulam:Transloca2onandphysiology

SherryLeClere,DougSammons:SNPdiscoveryandyeast2hybrid

Marcelo Figueiredo CnPQ, Brazil

Phil Westra