Hyperspectral Analysis for Discriminating Herbicide Site of Action: A Novel Approach for Accelerating Herbicide Research.

In agricultural weed management, herbicides are indispensable, yet innovation in their modes of action (MOA)-the general mechanisms affecting plant processes-has slowed. A finer classification within MOA is the site of action (SOA), the specific biochemical pathway in plants targeted by herbicides. The primary objectives of this study were to evaluate the efficacy of hyperspectral imaging in the early detection of herbicide stress and to assess its potential in accelerating the herbicide development process by identifying unique herbicide sites of action (SOA). Employing a novel SOA classification method, eight herbicides with unique SOAs were examined via an automated, high-throughput imaging system equipped with a conveyor-based plant transportation at Purdue University. This is one of the earliest trials to test hyperspectral imaging on a large number of herbicides, and the study aimed to explore the earliest herbicide stress detection/classification date and accelerate the speed of herbicide development. The final models, trained on a dataset with nine treatments with 320 samples in two rounds, achieved an overall accuracy of 81.5% 1 day after treatment. With the high-precision models and rapid screening of numerous compounds in only 7 days, the study results suggest that hyperspectral technology combined with machine learning can contribute to the discovery of new herbicide MOA and help address the challenges associated with herbicide resistance. Although no public research to date has used hyperspectral technology to classify herbicide SOA, the successful evaluation of herbicide damage to crops provides hope to accelerate the progress of herbicide development.

Impact of volatility reduction agents on dicamba and glyphosate spray solution pH, droplet dynamics, and weed control.

BACKGROUND: Regulations in 2021 required the addition of a volatility reduction agent (VRA) to dicamba spray mixtures for postemergence weed control. Understanding the impact of VRAs on weed control, droplet dynamics, and spray pH is essential. RESULTS: Adding glyphosate to dicamba decreased the solution pH by 0.63 to 1.85 units. Across locations, potassium carbonate increased the tank-mixture pH by 0.85 to 1.65 units while potassium acetate raised the pH by 0.46 to 0.53 units. Glyphosate and dicamba in tank-mixture reduced Palmer amaranth control by 14 percentage points compared to dicamba alone and decreased barnyardgrass control by 12 percentage points compared to glyphosate alone 4 weeks after application (WAA). VRAs resulted in a 5-percentage point reduction in barnyardgrass control 4 WAA. Common ragweed, common lambsquarters, and giant ragweed control were unaffected by herbicide solution 4 WAA. Dicamba alone produced a larger average droplet size and had the fewest driftable fines (% volume < 200 µm). Potassium acetate produced a larger droplet size than potassium carbonate for Dv0.1 and Dv0.5 . The addition of glyphosate to dicamba decreased droplet size from the entire spray droplet spectrum (Dv0.1 , Dv0.5 , Dv0.9 ). CONCLUSION: A reduction in spray pH, droplet size, and weed control was observed from mixing dicamba and glyphosate. It may be advisable to avoid tank-mixtures of these herbicides and instead, apply them sequentially to maximize effectiveness. VRAs differed in their impacts on spray solution pH and droplet dynamics, but resulted in a minimal negative to no impact on weed control. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Confirmation of herbicide resistance mutations Trp574Leu, ΔG210, and EPSPS gene amplification and control of multiple herbicide-resistant Palmer amaranth (Amaranthus palmeri) with chlorimuron-ethyl, fomesafen, and glyphosate.

Herbicide-resistant weeds, especially Palmer amaranth (Amaranthus palmeri S. Watson), are problematic in row-crop producing areas of the United States. The objectives of this study were to determine if chlorimuron-ethyl, fomesafen, and glyphosate applied separately and in mixtures control A. palmeri and confirm the presence of various genotypes surviving two- and three-way herbicide mixtures. Fifteen percent of A. palmeri treated with the three-way herbicide mixture survived. Mixing fomesafen with chlorimuron-ethyl or fomesafen with glyphosate to create a two-way mixture reduced A. palmeri survival 22 to 24% and 60 to 62% more than glyphosate and chlorimuron-ethyl alone, respectively. Previously characterized mutations associated with A. palmeri survival to chlorimuron-ethyl, fomesafen, and glyphosate Trp574Leu, a missing glycine codon at position 210 of the PPX2L gene (ΔG210), and 5-enolpyruvylshikimate-3-phosphase synthase (EPSPS) gene amplification; respectively, were present in surviving plants. However, 37% of plants treated with chlorimuron-ethyl did not contain heterozygous or homozygous alleles for the Trp574Leu mutation, suggesting alternative genotypes contributed to plant survival. All surviving A. palmeri treated with fomesafen or glyphosate possessed genotypes previously documented to confer resistance. Indiana soybean [Glycine max (L.) Merr] fields infested with A. palmeri possessed diverse genotypes and herbicide surviving plants are likely to produce seed and spread if alternative control measures are not implemented.

Nursing Gender Pay Differentials in the New Millennium.

BACKGROUND: The gender pay gap in the United States is an ongoing issue, affecting women in nearly all occupations. Jobs traditionally associated with men tend to pay better than traditionally female-dominated jobs, and there is evidence to suggest within-occupation gender pay differences as well. PURPOSE: We compared and contrasted gender wage disparities for registered nurses (RNs), relative to gender wage disparities for another female-dominated occupation, teachers, while controlling for sociodemographic factors. METHODS: Using data in the American Community Survey, we analyzed the largest U.S. random representative sample of self-identified RNs and primary or secondary school teachers from 2000 to 2013 using fixed-effects regression analysis. RESULTS: There is greater disparity between nurse pay by gender than in teacher pay by gender. In addition, the net return in wages for additional education is higher for school teachers (21.7%) than for RNs (4.7%). CONCLUSIONS: Findings support preferential wages for men in nursing, more so than for men in teaching. CLINICAL RELEVANCE: The substantial gender disparities are an indirect measure of the misallocation of resources in effective patient care.

Glyphosate resistance in Ambrosia trifida: Part 1. Novel rapid cell death response to glyphosate.

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.

Glyphosate resistance in Ambrosia trifida: Part 2. Rapid response physiology and non-target-site resistance.

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.

Who will have Sustainable Employment After a Back Injury? The Development of a Clinical Prediction Model in a Cohort of Injured Workers.

Purpose Our objective was to develop a clinical prediction model to identify workers with sustainable employment following an episode of work-related low back pain (LBP). Methods We used data from a cohort study of injured workers with incident LBP claims in the USA to predict employment patterns 1 and 6 months following a workers' compensation claim. We developed three sequential models to determine the contribution of three domains of variables: (1) basic demographic/clinical variables; (2) health-related variables; and (3) work-related factors. Multivariable logistic regression was used to develop the predictive models. We constructed receiver operator curves and used the c-index to measure predictive accuracy. Results Seventy-nine percent and 77 % of workers had sustainable employment at 1 and 6 months, respectively. Sustainable employment at 1 month was predicted by initial back pain intensity, mental health-related quality of life, claim litigation and employer type (c-index = 0.77). At 6 months, sustainable employment was predicted by physical and mental health-related quality of life, claim litigation and employer type (c-index = 0.77). Adding health-related and work-related variables to models improved predictive accuracy by 8.5 and 10 % at 1 and 6 months respectively. Conclusion We developed clinically-relevant models to predict sustainable employment in injured workers who made a workers' compensation claim for LBP. Inquiring about back pain intensity, physical and mental health-related quality of life, claim litigation and employer type may be beneficial in developing programs of care. Our models need to be validated in other populations.

Rating the digital help: electronic medical records, software providers, and physicians.

To separate the effects of physicians' characteristics on the perceived productivity of EMRs from the effects of limitations on usability inherent in EMR design, a multivariate regression model is used to estimate the factors influencing physicians' rankings of five attributes of their EMRs, namely; ease of use and reliability; the EMRs effect on physician and staff productivity and the EMRs performance vs. vendor's promises. We divide the factors influencing the rankings into three groups: physician characteristics, EMR characteristics and practice characteristics (type of practice, size, and location). The data are from approximately 1800 practicing physicians in Arizona. Physician's characteristics influence perceived ease of use and physicians' productivity, but not staff productivity, reliability or vendors' promised performance. Practice type and EMR characteristics affect perceived productivity, reliability and performance versus vendors' promises. Vendor-specific effects are highly correlated across all five attributes and are always jointly significant. EMR characteristics are the most significant influence on physicians' perceptions of the EMRs effect on their productivity and that of their staff. Physicians' characteristics (particularly age) have a small but significant influence on perceived productivity.

Management of pain in chronic pancreatitis with emphasis on exogenous pancreatic enzymes.

One of the most challenging issues arising in patients with chronic pancreatitis is the management of abdominal pain. Many competing theories exist to explain pancreatic pain including ductal hypertension from strictures and stones, increased interstitial pressure from glandular fibrosis, pancreatic neuritis, and ischemia. This clinical problem is superimposed on a background of reduced enzyme secretion and altered feedback mechanisms. Throughout history, investigators have used these theories to devise methods to combat chronic pancreatic pain including: Lifestyle measures, antioxidants, analgesics, administration of exogenous pancreatic enzymes, endoscopic drainage procedures, and surgical drainage and resection procedures. While the value of each modality has been debated over the years, pancreatic enzyme therapy remains a viable option. Enzyme therapy restores active enzymes to the small bowel and targets the altered feedback mechanism that lead to increased pancreatic ductal and tissue pressures, ischemia, and pain. Here, we review the mechanisms and treatments for chronic pancreatic pain with a specific focus on pancreatic enzyme replacement therapy. We also discuss different approaches to overcoming a lack of clinical response update ideas for studies needed to improve the clinical use of pancreatic enzymes to ameliorate pancreatic pain.

Registered Nurses: The Curious Case of a Persistent Shortage.

PURPOSE: To better understand the apparent persistent shortage of registered nurses (RNs), including both aggregate trends and cyclical responses. DESIGN: We examine the employment of RNs over variations in economic activity, employing national aggregate and unique micro-population data on nurses in Arizona. METHODS: These data, including our unique, ongoing survey of nurses in Arizona, enable a systematic examination of the cyclical demand for hospital care and institutional responses to that demand in the nursing market by employing multivariate regressions. FINDINGS: Demand for hospital nursing care increases rapidly during the early years of recessions, moderating as the economy improves. Hospitals initially employ more temporary nurses, then reduce temporary hires by shifting employed RNs from part time to full time while also adding RNs not previously employed in hospitals. The substitution of regularly employed RNs for temporary nurses reflects the need to reduce staffing costs to offset increases in uncompensated care. CONCLUSIONS: The increased supply of nurses came from delayed retirements, higher relative hospital wages (inducing nurses in other sectors to return to hospitals), and added-worker effects. Additional nursing hours were drawn from a pool of RNs who were not employed in health care. CLINICAL RELEVANCE: These results strongly suggest that correctly aligned incentives could reduce RN shortages without waiting for another recession.

Cabergoline in the Treatment of Male Orgasmic Disorder-A Retrospective Pilot Analysis.

INTRODUCTION: Male orgasmic disorder is common, with few treatment options. Cabergoline is a dopamine agonist that acts centrally to normalize serum prolactin that could improve orgasmic dysfunction. AIMS: To determine whether cabergoline increases the potential for orgasm in men with orgasmic disorder. METHODS: A retrospective chart review of men treated in a single andrology clinic for delayed orgasm or anorgasmia in a pilot study using cabergoline 0.5 mg twice weekly was performed. Duration of treatment and response were noted. Medical records were examined for other factors including history of prostatectomy and concomitant androgen supplementation. MAIN OUTCOME MEASURES: Subjective improvement in orgasmic function resulting from cabergoline treatment. RESULTS: Of 131 men treated with cabergoline for orgasmic disorder, 87 (66.4%) reported subjective improvement in orgasm and 44 (33.6%) reported no change in orgasm. Duration of therapy (P = .03) and concomitant testosterone therapy (P = .02) were associated with a significant positive response to cabergoline treatment. No differences were found between injectable and non-injectable testosterone formulations (P = .90), and neither age (P = .90) nor prior prostatectomy (P = .41) influenced the outcome of cabergoline treatment. Serum testosterone levels before (P = .26) and after (P = .81) treatment were not significantly different in responders vs non-responders. CONCLUSION: Cabergoline is a potentially effective and easy-to-administer treatment for male orgasmic disorder, the efficacy of which appears to be independent of patient age or orgasmic disorder etiology. Prospective randomized trials are needed to determine the true role of cabergoline in the treatment of this disorder.

Perceptions of overweight in US and global cultures.

We explored the hypothesis that perceptions of overweight vary in accord with the prevalence of overweight in specific populations. The present study investigated this relationship in samples from diverse groups in the US and four other countries. The perceptual threshold for overweight is the scalar point at which individuals determine the transition from normal to overweight. Perceptual thresholds for overweight were obtained from 812 adults in Korea, Mexico, Ukraine, Tanzania, and the US (Black, Hispanic, White and college student samples). A linear relationship was observed between the perceptual threshold for overweight and the population prevalence (r=0.52, adjusted R(2)=0.22, F (1/15)=5.24, p<.05), and this relationship was considerably stronger in the non-US samples. This finding links with the results of other studies documenting the influence of the social environment on both weight perception and weight transmission. Together, they suggest that the socio-cultural milieu and weight norms are components of the obesogenic environment and argue for the inclusion of weight norm interventions in weight management programs and public health initiatives.

Elevated Dihydrotestosterone is Associated with Testosterone Induced Erythrocytosis.

PURPOSE: Erythrocytosis is the most common dose limiting adverse effect of testosterone therapy but the mechanisms of testosterone mediated erythropoiesis remain unclear. In this study we examine risk factors for erythrocytosis associated with testosterone therapy. MATERIALS AND METHODS: A retrospective review was performed of 179 hypogonadal men on testosterone therapy at a single andrology clinic. Demographic data, testosterone therapy formulation and duration of treatment, and 5α-reductase inhibitor use were assessed. Serum dihydrotestosterone, total testosterone, free testosterone, follicle-stimulating hormone, luteinizing hormone, hematocrit and lipid levels were extracted, and changes during treatment were determined. Spearman's rank correlation was used to identify relationships between change in hematocrit and study variables. RESULTS: Of 179 patients 49 (27%) experienced a 10% or greater change in hematocrit and erythrocytosis (hematocrit 50% or greater) developed in 36 (20.1%) at a median followup of 7 months. Topical gels were used by 41.3% of patients, injectable testosterone by 52.5% and subcutaneous pellets by 6.1%. More men who experienced a change in hematocrit of 10% or greater used injectable testosterone than men with a change in hematocrit of less than 10% (65% vs 48%, p=0.035), and were less likely to be on a 5α-reductase inhibitor (2% vs 15%, p=0.017). Men with a change in hematocrit of 10% or greater had higher posttreatment dihydrotestosterone levels (605.0 vs 436.0 ng/dl, p=0.017) and lower luteinizing hormone and follicle-stimulating hormone levels than men with a change in hematocrit of less than 10%. Spearman's rank correlations yielded relationships between change in hematocrit and posttreatment dihydrotestosterone ρ=0.258, p=0.001) and total testosterone (ρ=0.171, p=0.023). CONCLUSIONS: Dihydrotestosterone may have a role in testosterone therapy related erythrocytosis and monitoring dihydrotestosterone levels during testosterone therapy should be considered. In men in whom erythrocytosis develops, 5α-reductase inhibitors may be therapeutic.

Comparative Effectiveness Research: A Roadmap for Physical Activity and Lifestyle.

PURPOSE: Comparative effectiveness research (CER) is designed to support informed decision making at both the individual, population, and policy levels. The American College of Sports Medicine and partners convened a conference with the focus of building an agenda for CER within the context of physical activity and nonpharmacological lifestyle approaches in the prevention and treatment of chronic disease. This report summarizes the conference content and consensus recommendations that culminated in a CER roadmap for physical activity and lifestyle approaches to reducing the risk of chronic disease. METHODS: This conference focused on presentations and discussion around the following topic areas: 1) defining CER, 2) identifying the current funding climate to support CER, 3) summarizing methods for conducting CER, and 4) identifying CER opportunities for physical activity. RESULTS: This conference resulted in consensus recommendations to adopt a CER roadmap for physical activity and lifestyle approaches to reducing the risk of chronic disease. In general, this roadmap provides a systematic framework by which CER for physical activity can move from a planning phase to a phase of engagement in CER related to lifestyle factors with particular emphasis on physical activity to a societal change phase that results in changes in policy, practice, and health. CONCLUSIONS: It is recommended that physical activity researchers and health care providers use the roadmap developed from this conference as a method to systematically engage in and apply CER to the promotion of physical activity as a key lifestyle behavior that can be effective at making an impact on a variety of health-related outcomes.

The effect of nitrogen rate on transgenic corn Cry3Bb1 protein expression.

BACKGROUND: Combining herbicide-resistant and Bacillus thuringiensis (Bt) traits in corn (Zea mays L.) hybrids may affect insect resistance management owing to volunteer corn. Some Bt toxins may be expressed at lower levels by nitrogen-deficient corn roots. Corn plants with sublethal levels of Bt expression could accelerate the evolution of Bt resistance in target insects. The present objective was to quantify the concentration of Bt (Cry3Bb1) in corn root tissue with varying tissue nitrogen concentrations. RESULTS: Expression of Cry3Bb1 toxin in root tissue was highly variable, but there were no differences in the overall concentration of Cry3Bb1 expressed between roots taken from Cry3Bb1-positive volunteer and hybrid corn plants. The nitrogen rate did affect Cry3Bb1 expression in the greenhouse, less nitrogen resulted in decreased Cry3Bb1 expression, yet this result was not documented in the field. CONCLUSION: A positive linear relationship of plant nitrogen status on Cry3Bb1 toxin expression was documented. Also, high variability in Cry3Bb1 expression is potentially problematic from an insect resistance management perspective. This variability could create a mosaic of toxin doses in the field, which does not fit into the high-dose refuge strategy and could alter predictions about the speed of evolution of resistance to Cry3Bb1 in western corn rootworm Diabrotica virgifera virgifera LeConte.

Are low income patients receiving the benefits of electronic health records? A statewide survey.

There are concerns that physicians serving low-income, Medicaid patients, in the United States are less likely to adopt electronic health records and, if so, that Medicaid patients will be denied the benefits from electronic health record use. This study seeks to determine whether physicians treating Medicaid patients were less likely to have adopted electronic health records. Physician surveys completed during physicians' license renewal process in Arizona were merged with the physician licensing data and Medicaid administrative claims data. Survey responses were received from 50.7 percent (6,780 out of 13,380) of all physicians practicing in Arizona. Physician survey responses were used to identify whether the physician used electronic health records and the degree to which the physician exchanged electronic health records with other health-care providers. Medicaid claims data were used to identify which physicians provided health care to Medicaid beneficiaries. The primary outcome of interest was whether Medicaid providers were more or less likely to have adopted electronic health records. Logistic regression analysis was used to estimate average marginal effects. In multivariate analysis, physicians with 20 or more Medicaid patients during the survey cycle were 4.1 percent more likely to use an electronic health record and 5.2 percent more likely to be able to transmit electronic health records to at least one health-care provider outside of their practice. These effects increase in magnitude when the analysis is restricted to solo practice physicians This is the first study to find a pro-Medicaid gap in electronic health record adoption suggesting that the low income patients served by Arizona's Health Care Cost Containment System are not at a disadvantage with regard to electronic health record access and that Arizona's model of promoting electronic health record adoption merits further study.

The perceptual threshold for overweight.

Normative, global overweight may play a prominent role in perpetuating the obesity epidemic via its contribution to weight-related norms that describe what is customary in a social environment. These weight-related norms include a perceptual standard determining where body weight shifts from normal to overweight. We introduce the construct of a perceptual threshold for overweight to identify this transition point. The perceptual threshold is measured on 0-100mm scales positioned below adult and child figures. This report presents three studies that evaluate the psychometric properties of this variable. Study 1explored its independence from BMI and body image in factor analyses with diverse samples (Ukrainian, Mexican and US Black, White, and Hispanic). Study 2 was a replication of this factor structure, and Study 3 investigated the reliability of the perceptual threshold using classical test (CT) and generalizability methods (GT). In Studies 1 and 2, two factors were identified (Perceptual Threshold for Overweight and Body Image/BMI) with almost identical factor structures in six analyses. In Study 3 the CT and GT procedures demonstrated adequate reliability. These results indicate that the psychometric properties of the perceptual threshold are sound, and support its use in exploring the social transmission of weight and evaluating obesity prevention and intervention programs.

A modified measure of health care disparities applied to birth weight disparities and subsequent mortality.

We describe how a modified Gini index serves as an improved method of estimating health care disparities. The method, although general, is applied to an example of birth weight disparities and to their effect on subsequent mortality. The method provides the between-group results obtainable from current methods (i.e. how Hispanics generally fare relative to non-Hispanic Whites) but adds measures of within-group disparities (i.e. which specific Hispanics experience the greatest disparate treatment). Our application to birth weights and receipt of prenatal care, which may provide an upper bound because of omitted variables, shows that the time-of-birth disparities are associated with increased infant mortality within the first year of life.

Cross-resistance of horseweed (Conyza canadensis) populations with three different ALS mutations.

BACKGROUND: Horseweed is a weed commonly found in agronomic crops, waste areas and roadsides. Resistance to ALS-inhibiting herbicides in horseweed was first reported in 1993 in a population from Israel. Resistance to ALS-inhibiting herbicides in horseweed is now widespread, but, as of now, the resistance mechanism has not been reported. RESULTS: Two of three populations evaluated (P116 and P13) were found to be uniform for resistance (>98% of individuals survived 8.8 g AI ha(-1) of cloransulam), whereas a third population, P525, contained about 85% resistant individuals. Cross-resistance to cloransulam, chlorimuron, imazethapyr and bispyribac was observed in the P116 population. P525 and P13 were both sensitive to imazethapyr but resistant to chlorimuron, imazethapyr and bispyribac. Enzyme activity assays indicated that resistance in P13 was due to an altered target site. Southern blot analysis indicated that the ALS target site is encoded by a single copy gene. Overlapping ALS gene regions were amplified and sequenced from each population. Amino acid substitutions of Ser for Pro at position 197 (P197S) was detected from P13, Ala for Pro (P197A) was identified from P525 and substitution of Glu for Asp (D376E) at position 376 was found in P116. Molecular markers were developed to differentiate between wild-type and resistant codons at positions 197 and 376 of horseweed ALS. CONCLUSION: Resistance to ALS-inhibiting herbicides in horseweed is conferred by target-site mutations that have also been identified in other weed species. Identification of the mutations within horseweed ALS gene sequence enables molecular assays for rapid detection and resistance diagnosis.

Benchmark study on glyphosate-resistant cropping systems in the United States. Part 4: Weed management practices and effects on weed populations and soil seedbanks.

BACKGROUND: Weed management in glyphosate-resistant (GR) maize, cotton and soybean in the United States relies almost exclusively on glyphosate, which raises criticism for facilitating shifts in weed populations. In 2006, the benchmark study, a field-scale investigation, was initiated in three different GR cropping systems to characterize academic recommendations for weed management and to determine the level to which these recommendations would reduce weed population shifts. RESULTS: A majority of growers used glyphosate as the only herbicide for weed management, as opposed to 98% of the academic recommendations implementing at least two herbicide active ingredients and modes of action. The additional herbicides were applied with glyphosate and as soil residual treatments. The greater herbicide diversity with academic recommendations reduced weed population densities before and after post-emergence herbicide applications in 2006 and 2007, particularly in continuous GR crops. CONCLUSION: Diversifying herbicides reduces weed population densities and lowers the risk of weed population shifts and the associated potential for the evolution of glyphosate-resistant weeds in continuous GR crops. Altered weed management practices (e.g. herbicides or tillage) enabled by rotating crops, whether GR or non-GR, improves weed management and thus minimizes the effectiveness of only using chemical tactics to mitigate weed population shifts.