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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