Monsanto (Canada)

Acyl CoA:diacylgycerol acyltransferase (EC; DGAT) catalyzes the final step in the production of triacylglycerol. Two polypeptides, which co-purified with DGAT activity, were isolated from the lipid bodies of the oleaginous fungus Mortierella ramanniana with a procedure consisting of dye affinity, hydroxyapatite affinity, and heparin chromatography. The two enzymes had molecular masses of 36 and 36.5 kDa, as estimated by gel electrophoresis, and showed a broad activity maximum between pH 6 and 8. Based on partial peptide sequence information, polymerase chain reaction techniques were used to obtain full-length cDNA sequences encoding the purified proteins. Expression of the cDNAs in insect cells conferred high levels of DGAT activity on the membranes isolated from these cells. The two proteins share 54% homology with each other but are unrelated to the previously identified DGAT gene family (designated DGAT1), which is related to the acyl CoA:cholesterol acyltransferase gene family, or to any other gene family with ascribed function. This report identifies a new gene family, including members in fungi, plants and animals, which encode enzymes with DGAT function. To distinguish the two unrelated families we designate this new class DGAT2 and refer to the M. ramanniana genes as MrDGAT2A and MrDGAT2B.

Active sensor reflectance assessments of corn ( Zea mays L.) canopy N status are advocated to direct variable N applications and improve N use efficiency (NUE). Our goals were to determine: (i) growth stage and (ii) sensor vegetation index with greatest sensitivity in assessing N status and grain yield. Variable crop N was generated by supplying N at different amounts and times in three field studies. Chlorophyll meter (CM) and sensor data were gathered at two vegetative (V11 and V15) and two reproductive (R1 and R3) growth stages, using the Crop Circle sensor that measures reflectance in visible (590 nm) and near infrared (NIR) (880 nm) bands. Sensor data were converted to the normalized difference vegetation index (NDVI 590 ) and chlorophyll index (CI 590 ) values. Grain yields were also determined. Sensor indices were more highly correlated with CM readings for vegetative vs. reproductive growth ( r 2 of 0.85 vs. 0.55). The CM vs. CI 590 slope was over twice the NDVI 590 slope value, indicating CI 590 was more sensitive than NDVI 590 in assessing canopy greenness. Indices did not differ in ability to distinguish yield variation. Results indicate sensor CI 590 values collected during vegetative growth are best suited to direct variable N applications.

BACKGROUND: Identification of QTL with large phenotypic effects conserved across genetic backgrounds and environments is one of the prerequisites for crop improvement using marker assisted selection (MAS). The objectives of this study were to identify meta-QTL (mQTL) for grain yield (GY) and anthesis silking interval (ASI) across 18 bi-parental maize populations evaluated in the same conditions across 2-4 managed water stressed and 3-4 well watered environments. RESULTS: The meta-analyses identified 68 mQTL (9 QTL specific to ASI, 15 specific to GY, and 44 for both GY and ASI). Mean phenotypic variance explained by each mQTL varied from 1.2 to 13.1% and the overall average was 6.5%. Few QTL were detected under both environmental treatments and/or multiple (>4 populations) genetic backgrounds. The number and 95% genetic and physical confidence intervals of the mQTL were highly reduced compared to the QTL identified in the original studies. Each physical interval of the mQTL consisted of 5 to 926 candidate genes. CONCLUSIONS: Meta-analyses reduced the number of QTL by 68% and narrowed the confidence intervals up to 12-fold. At least the 4 mQTL (mQTL2.2, mQTL6.1, mQTL7.5 and mQTL9.2) associated with GY under both water-stressed and well-watered environments and detected up to 6 populations may be considered for fine mapping and validation to confirm effects in different genetic backgrounds and pyramid them into new drought resistant breeding lines. This is the first extensive report on meta-analysis of data from over 3100 individuals genotyped using the same SNP platform and evaluated in the same conditions across a wide range of managed water-stressed and well-watered environments.

Stem canker of oilseed rape (canola, Brassica napus ) is associated with a species complex of two closely related fungal species, Leptosphaeria maculans and L. biglobosa . Of these, L. maculans is the most damaging and develops gene‐for‐gene relationships with the host . Here, a wide scale analysis of the L. maculans ‐ L. biglobosa species complex was performed throughout the American continent (23 locations from Chile to Canada) plus several locations in Western Australia for comparison purposes, based on a collection of 1132 isolates from infected tissues of a susceptible cultivar. Fungal species were discriminated on the basis of morphological, phytopathological and molecular criteria and showed that L. biglobosa was closely associated with L. maculans in most of the locations. Multiple gene phylogeny using sequences of ITS, actin and β‐tubulin confirmed the prevalence of the L. biglobosa ‘canadensis’ sub‐clade in Canada, whereas up to three different sub‐clades of L. biglobosa were found in Georgia (USA). Race structure of L. maculans was investigated using a combination of pathogenicity tests and PCR amplification of avirulence alleles AvrLm1 , AvrLm4 and AvrLm6 . Three contrasting situations were observed: (i) race structure in Ontario, Chile and Georgia was related to that of European and Western Australian populations, with a low race diversity; (ii) only one race was found in Mexico, and not found outside of this country; (iii) a large diversity of races was observed in central Canada (Manitoba, Alberta and Saskatchewan) with very specific features including maintenance of avirulence alleles absent from Europe, absence of the AvrLm7 allele common in Europe (or eastern Canada) and wide location‐to‐location variability.

BACKGROUND & AIMS: Barrett's esophagus (BE) increases the risk of esophageal adenocarcinoma (EAC). We found the risk to be BE has been associated with single nucleotide polymorphisms (SNPs) on chromosome 6p21 (within the HLA region) and on 16q23, where the closest protein-coding gene is FOXF1. Subsequently, the Barrett's and Esophageal Adenocarcinoma Consortium (BEACON) identified risk loci for BE and esophageal adenocarcinoma near CRTC1 and BARX1, and within 100 kb of FOXP1. We aimed to identify further SNPs that increased BE risk and to validate previously reported associations. METHODS: We performed a genome-wide association study (GWAS) to identify variants associated with BE and further analyzed promising variants identified by BEACON by genotyping 10,158 patients with BE and 21,062 controls. RESULTS: We identified 2 SNPs not previously associated with BE: rs3072 (2p24.1; odds ratio [OR] = 1.14; 95% CI: 1.09-1.18; P = 1.8 × 10(-11)) and rs2701108 (12q24.21; OR = 0.90; 95% CI: 0.86-0.93; P = 7.5 × 10(-9)). The closest protein-coding genes were respectively GDF7 (rs3072), which encodes a ligand in the bone morphogenetic protein pathway, and TBX5 (rs2701108), which encodes a transcription factor that regulates esophageal and cardiac development. Our data also supported in BE cases 3 risk SNPs identified by BEACON (rs2687201, rs11789015, and rs10423674). Meta-analysis of all data identified another SNP associated with BE and esophageal adenocarcinoma: rs3784262, within ALDH1A2 (OR = 0.90; 95% CI: 0.87-0.93; P = 3.72 × 10(-9)). CONCLUSIONS: We identified 2 loci associated with risk of BE and provided data to support a further locus. The genes we found to be associated with risk for BE encode transcription factors involved in thoracic, diaphragmatic, and esophageal development or proteins involved in the inflammatory response.

ABSTRACT In marker‐assisted recurrent selection (MARS), a subset of molecular markers significantly associated with target traits of interest are used to predict the breeding value of individual plants, followed by rapid recombination and selfing. This study estimated genetic gains in grain yield (GY) using MARS in 10 biparental tropical maize ( Zea may L.) populations. In each population, 148 to 184 F 2:3 (defined as C 0 ) progenies were derived, crossed with a single‐cross tester, and evaluated under water‐stressed (WS) and well‐watered (WW) environments in sub‐Saharan Africa (SSA). The C 0 populations were genotyped with 190 to 225 single‐nucleotide polymorphism (SNP) markers. A selection index based on marker data and phenotypic data was used for selecting the best C 0 families for recombination. Individual plants from selected families were genotyped using 55 to 87 SNPs tagging specific quantitative trait loci (QTL), and the best individuals from each cycle were either intercrossed (to form C 1 ) or selfed (to form C 1 S 1 and C 1 S 2 ). A genetic gain study was conducted using test crosses of lines from the different cycles F 1 and founder parents. Test crosses, along with five commercial hybrid checks were evaluated under four WS and four WW environments. The overall gain for GY using MARS across the 10 populations was 105 kg ha −1 yr −1 under WW and 51 kg ha −1 yr −1 under WS. Across WW environments, GY of C 1 S 2 –derived hybrids were 8.7, 5.9, and 16.2% significantly greater than those of C 0 , founder parents, and commercial checks, respectively. Results demonstrate the potential of MARS for increasing genetic gain under both drought and optimum environments in SSA.

BACKGROUND: The importance of engaging key stakeholders, and patients in particular, in determining research priorities has been recognized. We sought to identify the top 10 research priorities for patients with non-dialysis chronic kidney disease (CKD), their caregivers, and the clinicians and policy-makers involved in their care. METHODS: We used the four-step James Lind Alliance process to establish the top 10 research priorities. A national survey of patients with non-dialysis CKD (estimated glomerular filtration rate <45 mL/min/1.73 m 2 ), their caregivers, and the clinicians and policy-makers involved in their care was conducted to identify research uncertainties. A Steering Group of patients, caregivers, clinicians and researchers combined and reduced these uncertainties to 30 through a series of iterations. Finally, a workshop with participants from across Canada (12 patients, 6 caregivers, 3 physicians, 2 nurses, 1 pharmacist and 1 policy-maker) was held to determine the top 10 research priorities, using a nominal group technique. RESULTS: Overall, 439 individuals responded to the survey and identified 1811 uncertainties, from which the steering group determined the top 30 uncertainties to be considered at the workshop. The top 10 research uncertainties prioritized at the workshop included questions about treatments to prevent progression of kidney disease (including diet) and to treat symptoms of CKD, provider- and patient-targeted strategies for managing CKD, the impact of lifestyle on disease progression, harmful effects of medications on disease progression, optimal strategies for treatment of cardiovascular disease in CKD and for early identification of kidney disease, and strategies for equitable access to care for patients with CKD. CONCLUSIONS: We identified the top 10 research priorities for patients with CKD that can be used to guide researchers, as well as inform funders of health-care research.

Apoptosis contributes to the development of diabetic nephropathy (DN), but the mechanisms that lead to diabetes-induced cell death are not fully understood. Here, we combined a functional genomics screen for cDNAs that induce apoptosis in vitro with transcriptional profiling of renal biopsies from patients with DN. Twelve of the 138 full-length cDNAs that induced cell death in human embryonic kidney cells matched upregulated mRNA transcripts in tissue from human DN. Confirmatory screens identified induction of BASP1 in tubular cross sections of human DN tissue. In vitro, apoptosis-inducing conditions such as serum deprivation, high concentrations of glucose, and proinflammatory cytokines increased BASP1 mRNA and protein in human tubular epithelial cells. In normal cells, BASP1 localized to the cytoplasm, but in apoptotic cells, it colocalized with actin in the periphery. Overexpression of BASP1 induced cell death with features of apoptosis; conversely, small interfering RNA (siRNA)-mediated knockdown of BASP1 protected tubular cells from apoptosis. Supporting possible involvement of BASP1 in renal disease other than DN, we also observed significant upregulation of renal BASP1 in spontaneously hypertensive rats and a trend toward increased tubulointerstitial BASP1 mRNA in human hypertensive nephropathy. In summary, a combined functional genomics approach identified BASP1 as a proapoptotic factor in DN and possibly also in hypertensive nephropathy.

After menopause, blood pressure increases in women. However, the underlying mechanisms responsible for postmenopausal hypertension are not completely understood. This study was conducted to determine the role that the renin-angiotensin system (RAS) plays in post-menopausal hypertension. Post-estrous cycling (postmenopausal) spontaneously hypertensive rats or young female controls were treated with losartan, an angiotensin (Ang) II type 1 receptor blocker, for 25 days. Mean arterial pressure was recorded continuously by radiotelemetry. Losartan significantly decreased blood pressure in postmenopausal rats and young female controls but failed to normalize blood pressure in postmenopausal rats to levels found in young controls. Plasma renin activity and plasma angiotensinogen were significantly elevated, and intrarenal Ang II type 1 receptor and renin mRNA expression were significantly downregulated in postmenopausal rats. Therefore, RAS only partially contributes to hypertension in postcycling spontaneously hypertensive rats, whereas hypertension in young females is mediated mainly by the RAS. The data suggest that other mechanisms besides activation of the RAS are likely involved in postmenopausal hypertension.

Insulin-like growth factor (IGF-I) is a single chain, 70-amino acid, peptide hormone, which is essential to the process of growth and differentiation in higher vertebrates. IGF-I exhibits a very high degree of conservation throughout vertebrate evolution, and recent studies in fish have shown improved rates of growth in salmonids treated with exogenous recombinant mammalian IGF-I, implying a role for this hormone in fish similar to that in mammals. This paper reports the identification and sequencing of four different liver-derived cDNAs encoding IGF-I from chinook salmon, Oncorhynchus tshawytscha. The different cDNAs all contain sequences that encode an identical mature IGF-I protein. The differences between the four cDNAs are of two types: 1) single basepair changes and 2) additional blocks of sequence occurring at one site within the E-domain regions of three of the four cDNAs. The sequence data indicate that each of the cDNAs identified was transcribed from a different IGF-I gene, and analysis of the chinook salmon genome by Southern blotting supports the existence of four distinct IGF-I genes and suggests that there are at least two IGF-I loci in salmon. Although, analysis of total RNA from salmonid liver identifies only a single major transcript of 4200 nucleotides, polymerase chain reaction analysis suggests the presence of two structurally different salmonid IGF-I genes with the potential for multiple splicing alternatives of the IGF-I transcript.

Herbicide-resistant crops, such as glyphosate-resistant (GR) soybean, allow for broad-spectrum, flexible weed control with minimal crop injury; however, the development of GR weeds, such as horseweed, has forced reliance on alternative herbicides for control of these weeds. While preplant (PP) herbicides provide excellent control of GR-horseweed, there are currently no POST herbicide control options within soybean. The objective of this study was to evaluate the efficacy of dicamba for the control of GR-horseweed when applied PP, POST, and sequentially in dicamba-resistant soybean. Dicamba applied PP at 600 g a.e. ha −1 provided 90 to 100% control of GR-horseweed 8 wk after application (WAA) across three field trials conducted in Ontario in 2011 and 2012. Similarly, sequential applications provided 91 to 100% control. This technology provides a much-needed POST option of dicamba to be applied as a rescue treatment to control weed escapes caused by late emergence or poor initial control following a PP herbicide application.

ABSTRACT Laird No. 1 lentils micronized (high‐intensity infrared heat) to give internal temperatures of 138 and 170 °C were compared to unprocessed lentils stored at room temperature. Micronized lentils, which had been tempered to 33% moisture for 16 h, required less force to compress after cooking and contained increased levels of gelatinized starch and pectic substances but decreased levels of soluble protein, phytic acid, and neutral detergent fiber compared to the unprocessed lentils. Cell walls in the micronized lentil were less susceptible to fracture, and the microstructure was more open. Properties of the micronized lentils were better when the internal temperature reached 138 °C. When micronized to an internal temperature of 170 °C, cooked lentils were harder, possibly due to greater moisture losses and a change in the neutral detergent fiber. Micronization resulted in a slight darkening of the lentils, and this was accentuated at 170 °C.

Brown stem rot (BSR) of soybean [ Glycine max (L.) Merr.] is caused by the fungal pathogen Phialophora gregata (Allington &amp; D.W. Chamberlain) W. Gams and occurs in soybean production areas around the world. Brown stem rot resistance genes Rbs 1 , Rbs 2 , and Rbs 3 have been identified in soybean germplasm and plant introductions through traditional genetic analyses. Resistance to BSR has been shown to reduce yield losses in soybean, but selection for this trait is laborious and confounded by environmental variation. The objectives of this study were to identify molecular markers linked to BSR resistance genes Rbs 1 and Rbs 2 , and map these genes in the soybean genome. Genetic families of populations segregating for Rbs 1 and Rbs 2 were evaluated in the greenhouse for BSR phenotypic reaction and identified as resistant, segregating, or susceptible. Leaf tissue collected from members of F 2:3 families was bulked and DNA simple sequence repeat (SSR) marker analysis was used to identify markers that cosegregated with BSR reaction phenotypes. Five pairs of Rbs 2 near‐isogenic lines were subjected to a similar analysis to verify results obtained from marker analysis conducted on the population segregating for Rbs 2 Results of marker analyses indicated that SSR markers Satt215 and Satt431 were linked to Rbs 1 and that Satt244 and Satt431 were linked to Rbs 2 Marker‐assisted selection in the Rbs 1 (using Satt431) and Rbs 2 (using Satt244) populations would have correctly predicted 88 and 82%, respectively, of the BSR reaction phenotypes. The Rbs 1 and Rbs 2 loci map to Molecular Linkage Group J and lie in a region known to contain Rbs 3 This region also contains loci conditioning resistance to taxonomically diverse fungal pathogens and a locus affecting nodulation in response to a bacterial symbiont.

BACKGROUND: The glyphosate-resistant rapid response (GR RR) resistance mechanism in Ambrosia trifida is not due to target-site resistance (TSR) mechanisms. This study explores the physiology of the rapid response and the possibility of reduced translocation and vacuolar sequestration as non-target-site resistance (NTSR) mechanisms. RESULTS: GR RR leaf discs accumulated hydrogen peroxide within minutes of glyphosate exposure, but only in mature leaf tissue. The rapid response required energy either as light or exogenous sucrose. The combination of phenylalanine and tyrosine inhibited the rapid response in a dose-dependent manner. Reduced glyphosate translocation was observed in GR RR, but only when associated with tissue death caused by the rapid response. Nuclear magnetic resonance studies indicated that glyphosate enters the cytoplasm and reaches chloroplasts, and it is not moved into the vacuole of GR RR, GR non-rapid response or glyphosate-susceptible A. trifida. CONCLUSION: The GR RR mechanism of resistance is not associated with vacuole sequestration of glyphosate, and the observed reduced translocation is likely a consequence of rapid tissue death. Rapid cell death was inhibited by exogenous application of aromatic amino acids phenylalanine and tyrosine. The mechanism by which these amino acids inhibit rapid cell death in the GR RR phenotype remains unknown, and it could involve glyphosate phytotoxicity or other agents generating reactive oxygen species. Implications of these findings are discussed. The GR RR mechanism is distinct from the currently described glyphosate TSR or NTSR mechanisms in other species. © 2017 Society of Chemical Industry.

The extent of pollen‐mediated gene flow (PMGF) in wheat ( Triticum spp. L.) as a function of distance from a pollinator source has been measured in recent field studies. Wheat is primarily self‐pollinated; however, some cross‐pollination can occur depending on biological, agronomic, and environmental factors. The complexity of these interactions restricts attempts to develop a workable mechanistic model; therefore, we pursued an entirely empirical modeling approach. We fit a simple empirical regression model to all available observed data and then used it to make general predictions about the effects of field size, blending at harvest, and isolation distances on PMGF in wheat. The empirical model was derived by fitting a least squares regression line to the gene flow data when plotted as the logarithm of PMGF versus the square root distance from the edge of the source field. Linear behavior was observed when either the maximum or mean PMGF was plotted in this manner. A “General Wheat Model” (GWM) of this same mathematical form is given which provides a conservative (“high‐end”) prediction of PMGF in the general case: , where PMGF is the percent gene flow at a particular point in the field (without blending), and x is the distance (m) from the edge of the source field. The GWM was used to show that the effect of source field size is minimal for sources of 10 ha or larger, where asymptotic levels of PMGF are obtained. The model was also applied to show that harvest‐blending produces PMGF at the field level 10 to 50 times lower than the highest level observed at the edge of the receptor field. Significantly, isolation buffers of 0 to 10 m were predicted by the GWM to have only a minimal impact on harvest‐blended PMGF, when the receptor field had an overall width of 100 m or greater. Without any isolation buffers, the harvest‐blended PMGF between neighboring commercial‐sized (&gt;10 ha) fields was less than 0.1% (well below commercial thresholds for foreign material in wheat seed and grain). This is also well below any existing standards for labeling the presence of approved biotech traits in food or seed distributed or sold as conventional.

One of the major breeding objectives for watermelon ( Citrullus lanatus [Thumb.] Matsum &amp; Nakai) is improved fruit yield. High yielding genotypes have been identified, so we measured their stability for fruit yield and yield components over diverse environments. The objectives of this study were to (i) evaluate the yield of watermelon genotypes over years and locations, (ii) identify genotypes with high stability for yield, and (iii) measure the correlations among univariate and multivariate stability statistics. A diverse set of 40 genotypes was evaluated over 3 yr (2009, 2010, and 2011) and eight locations across the southern United States in replicated trials. Yield traits were evaluated over multiple harvests, and measured as marketable yield, fruit count, percentage cull fruit, percentage early fruit, and fruit size. There were strong effects of environment as well as genotype × environment interaction (G×E) on watermelon yield traits. Based on multiple stability measures, genotypes were classified as stable or unstable for yield. There was an advantage of hybrids over inbreds for yield components in both performance and responsiveness to favorable environments. Cultivars Big Crimson and Legacy are inbred lines with high yield and stability. A significant ( P &lt; 0.001) and positive correlation was measured for Shukla's stability variance (σ i 2 ), Shukla's squared hat ( ŝ i 2 ), Wricke's ecovalence ( W i ), and deviation from regression ( S 2 d ) for all the traits evaluated in this study.

Clubroot disease is devastating to Brassica crop production when susceptible cultivars are planted in infected fields. European turnips are the most resistant sources and their resistance genes have been introduced into other crops such oilseed rape (Brassica napus L.), Chinese cabbage and other Brassica vegetables. The European clubroot differential (ECD) set contains four turnip accessions (ECD1 to ECD4). These ECD turnips exhibited high levels of resistance to clubroot when they were tested under controlled environmental conditions with Canadian field isolates. Gene mapping of the clubroot resistance genes in ECD1 to ECD4 were performed and three independent dominant resistance loci were identified. Two resistance loci were mapped on chromosome A03 and the third on chromosome A08. Each ECD turnip accession contained two of these three resistance loci. Some resistance loci were homozygous in ECD accessions while others showed heterozygosity based on the segregation of clubroot resistance in 20 BC1 families derived from ECD1 to ECD4.

Glyphosate-resistant (GR) giant ragweed has been confirmed in Ontario, Canada. Giant ragweed is an extremely competitive weed and lack of control in soybean will lead to significant yield losses. Seed companies have developed new herbicide-resistant (HR) crop cultivars and hybrids that stack multiple HR traits. The objective of this research was to evaluate the efficacy of glyphosate and glyphosate plus dicamba tank mixes for the control of GR giant ragweed under Ontario environmental conditions in dicamba-tolerant (DT) soybean. Three field trials were established over a 2-yr period (2010 and 2011) on farms near Windsor and Belle River, ON. Treatments included glyphosate (900 g ae ha −1 ), dicamba (300 g ae ha −1 ), and dicamba (600 g ha −1 ) applied preplant (PP), POST, or sequentially in various combinations. Glyphosate applied PP, POST, or sequentially provided 22 to 68%, 40 to 47%, and 59 to 95% control of GR giant ragweed and reduced shoot dry weight 26 to 80%, 16 to 50%, and 72 to 98%, respectively. Glyphosate plus dicamba applied PP followed by glyphosate plus dicamba applied POST consistently provided 100% control of GR giant ragweed. DT soybean yield correlated with GR giant ragweed control. This is the first report in Canada of weed control in DT soybean, specifically for the control of GR giant ragweed. Results indicate that the use of dicamba in DT soybean will provide an effective option for the control of GR giant ragweed in Ontario.

Byker, H. P., Soltani, N., Robinson, D. E., Tardif, F. J., Lawton, M. B. and Sikkema, P. H. 2013. Occurrence of glyphosate and cloransulam resistant Canada fleabane ( Conyza canadensis L. Cronq.) in Ontario. Can. J. Plant Sci. 93: 851–855. Canada fleabane is the second documented glyphosate-resistant (GR) weed species in Ontario, Canada. In 2010, the first eight GR Canada fleabane populations were identified in Essex County. In 2011 and 2012, an expanded survey was conducted to identify the occurrence of GR and cloransulam-resistant populations in Ontario. Seed was collected from field weed escapes in the early fall and sprayed in the greenhouse with 900 g a.e. ha −1 of glyphosate at the 10-cm rosette stage. Ninety-three and 54 additional sites were confirmed in 2011 and 2012, respectively. There are now 155 sites with confirmed GR Canada fleabane in Ontario in the counties of Elgin, Essex, Haldimand, Huron, Kent, Lambton, Middlesex, and Niagara region. Twelve and seven sites were identified with multiple resistant Canada fleabane (glyphosate and cloransulam) in 2011 and 2012, respectively in Elgin, Essex, Kent, Lambton, and Middlesex counties. This is the first survey documenting the occurrence of glyphosate-resistant and multiple resistant (glyphosate and cloransulam) Canada fleabane in Ontario and its distribution.

BACKGROUND: Glyphosate-resistant (GR) Ambrosia trifida is now present in the midwestern United States and in southwestern Ontario, Canada. Two distinct GR phenotypes are known, including a rapid response (GR RR) phenotype, which exhibits cell death within hours after treatment, and a non-rapid response (GR NRR) phenotype. The mechanisms of resistance in both GR RR and GR NRR remain unknown. Here, we present a description of the RR phenotype and an investigation of target-site mechanisms on multiple A. trifida accessions. RESULTS: Glyphosate resistance was confirmed in several accessions, and whole-plant levels of resistance ranged from 2.3- to 7.5-fold compared with glyphosate-susceptible (GS) accessions. The two GR phenotypes displayed similar levels of resistance, despite having dramatically different phenotypic responses to glyphosate. Glyphosate resistance was not associated with mutations in EPSPS sequence, increased EPSPS copy number, EPSPS quantity, or EPSPS activity. CONCLUSION: These encompassing results suggest that resistance to glyphosate in these GR RR A. trifida accessions is not conferred by a target-site resistance mechanism. © 2017 Society of Chemical Industry.