Confirmation of Glyphosate-Resistant Kochia (Kochia scoparia) from Sugar Beet Fields in Idaho and Oregon

Abstract Glyphosate-resistant (GR) kochia is an increasing management concern in major cropping systems of the northwestern US. In 2014, we investigated four putative GR kochia accessions (designated as ALA, VAL, WIL, DB) collected from sugar beet fields in eastern Oregon and southwestern Idaho to characterize the level of evolved glyphosate resistance and determine the relationship between the 5-enol-pyruvylshikimate-3-phospate synthase (EPSPS) gene copy number and level of glyphosate resistance. The EPSPS gene copy number was used as a molecular marker to detect GR kochia in subsequent surveys in 2015 and 2016. Based on LD50 values from a whole-plant dose-response study, the four putative GR kochia populations were 2.0- to 9.6-fold more resistant to glyphosate than the glyphosate-susceptible (GS) accession. In an in vivo leafdisk shikimate assay, leaf disks of GS kochia plants treated with 100-µM glyphosate accumulated 2.4- to 4.0-fold higher amounts of shikimate than the GR plants. The four GR accessions had 2.7 to 9.1 relative EPSPS gene copies compared with the GS accession (<1 EPSPS gene copies), and there was a linear relationship between EPSPS gene copy number and glyphosate resistance level (LD50 values). The 2015 and 2016 GR kochia survey results indicated that about half of the collected populations from sugar beet fields in eastern Oregon had developed resistance to glyphosate whereas only one population from the Idaho collection was confirmed glyphosate resistant. This is the first confirmation of GR kochia in sugar beet fields in eastern Oregon and southwestern Idaho. Diversified weed control programs will be required to prevent further development and spread of GR kochia in sugar beet-based rotations in this region. Nomenclature: Glyphosate; kochia, Kochia scoparia (L.) Schrad.; sugar beet, Beta vulgaris L.

[1]  Eric L. Patterson,et al.  EPSPS Gene Copy Number and Whole-Plant Glyphosate Resistance Level in Kochia scoparia , 2016, PloS one.

[2]  H. Beckie,et al.  Pollen- and Seed-Mediated Gene Flow in Kochia (Kochia scoparia) , 2016, Weed Science.

[3]  P. Jha,et al.  Correction: Growth and Reproduction of Glyphosate-Resistant and Susceptible Populations of Kochia scoparia , 2016, PloS one.

[4]  Florent Baty,et al.  Dose-Response Analysis Using R , 2015, PLoS ONE.

[5]  P. Jha,et al.  Growth and Reproduction of Glyphosate-Resistant and Susceptible Populations of Kochia scoparia , 2015, PloS one.

[6]  P. Jha,et al.  Molecular Basis of Evolved Resistance to Glyphosate and Acetolactate Synthase-Inhibitor Herbicides in Kochia (Kochia scoparia) Accessions from Montana , 2015, Weed Science.

[7]  P. Jha,et al.  Influence of glyphosate timing on Kochia scoparia demographics in glyphosate-resistant sugar beet , 2015 .

[8]  M. Jugulam,et al.  Field-evolved resistance to four modes of action of herbicides in a single kochia (Kochia scoparia L. Schrad.) population. , 2015, Pest management science.

[9]  J. Dille,et al.  Glyphosate-Resistant Kochia (Kochia scoparia) in Kansas: EPSPS Gene Copy Number in Relation to Resistance Levels , 2015 .

[10]  J. Leach,et al.  Gene amplification of 5-enol-pyruvylshikimate-3-phosphate synthase in glyphosate-resistant Kochia scoparia , 2014, Planta.

[11]  P. Westra,et al.  Tandem Amplification of a Chromosomal Segment Harboring 5-Enolpyruvylshikimate-3-Phosphate Synthase Locus Confers Glyphosate Resistance in Kochia scoparia1[W][OPEN] , 2014, Plant Physiology.

[12]  P. Jha,et al.  Occurrence and Characterization of Kochia (Kochia scoparia) Accessions with Resistance to Glyphosate in Montana , 2014, Weed Technology.

[13]  H. Beckie,et al.  Glyphosate- and Acetolactate Synthase Inhibitor–Resistant Kochia (Kochia scoparia) in Western Canada , 2013, Weed Science.

[14]  Cynthia S. Brown,et al.  Tumbling: Use of Diffuse Knapweed (Centaurea diffusa) to Examine an Understudied Dispersal Mechanism , 2010, Invasive Plant Science and Management.

[15]  A. Kniss.  Comparison of conventional and glyphosate-resistant sugarbeet the year of commercial introduction in Wyoming. , 2010 .

[16]  K. Renner,et al.  Weed Management in Glyphosate- and Glufosinate-Resistant Sugar Beet , 2009, Weed Technology.

[17]  Hugh J. Beckie,et al.  The biology of Canadian weeds. 138. Kochia scoparia (L.) Schrad. , 2009 .

[18]  T. Schwinghamer,et al.  Emergence Timing and Persistence of Kochia (Kochia Scoparia) , 2008, Weed Science.

[19]  W. Brien Henry,et al.  A rapid in vivo shikimate accumulation assay with excised leaf discs , 2005, Weed Science.

[20]  C. Messersmith,et al.  Genetic diversity of kochia , 2002, Weed Science.

[21]  John A. Smith,et al.  Influence of Glyphosate and Glufosinate on Weed Control and Sugarbeet (Beta vulgaris) Yield in Herbicide-Tolerant Sugarbeet1 , 2002, Weed Technology.

[22]  I. Heap.  International survey of herbicide-resistant weeds , 1997 .

[23]  P. Westra,et al.  Growth analysis of sulfonylurea-resistant and -susceptible kochia (Kochia scoparia) , 1997, Weed Science.

[24]  J. E. Jensen,et al.  Log-Logistic Analysis of Herbicide Dose-Response Relationships , 1995, Weed Technology.

[25]  C. Mallory-Smith,et al.  Pollen-Mediated Gene Flow of Sulfonylurea-Resistant Kochia (Kochia scoparia) , 1995, Weed Science.

[26]  R. Turkington,et al.  The biology of Canadian weeds , 1978 .

[27]  E. Schweizer,et al.  Predicting Sugarbeet Root Losses Based on Kochia Densities , 1973, Weed Science.

[28]  E. Schweizer,et al.  Competition Between Kochia and Sugarbeets , 1969, Weed Science.