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de Souza Rodrigues J, Shilling D, Tishchenko V, Bowen S, Deng S, Hall DB, Grey TL. Early growth, development and allometry of glyphosate-resistant and susceptible Amaranthus palmeri in response to current and elevated temperature and CO 2. Sci Rep 2023; 13:14427. [PMID: 37660074 PMCID: PMC10475059 DOI: 10.1038/s41598-023-41121-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2023] [Accepted: 08/22/2023] [Indexed: 09/04/2023] Open
Abstract
This study aimed to evaluate the influence of CO2 and temperature on glyphosate-resistant and susceptible biotypes of Amaranthus palmeri (Palmer amaranth) in terms of morphological development. Height (cm), stem diameter (cm), leaf area (cm2), number of leaves, leaf, stem, and root dry matter, plant volume (m3), as well as shoot-to-root allometry were evaluated. The Palmer amaranth biotypes were grown under four different scenarios: 1-low temperature (23/33 °C) and CO2 (410 ± 25 ppm); 2-low temperature (23/33 °C) and high CO2 (750 ± 25 ppm); 3-high temperature (26/36 °C) and low CO2 (410 ± 25 ppm); and 4-high temperature (26/36 °C) and CO2 (750 ± 25 ppm). Between CO2 and temperature, the majority of differences observed were driven by CO2 levels. Palmer amaranth grown under 750 ppm of CO2 was 15.5% taller, displayed 10% more leaf area (cm2), 18% more stem dry matter, and had a 28.4% increase in volume (m3) compared to 410 ppm of CO2. GA2017 and GA2020 were 18% and 15.5% shorter, respectively. The number of leaves was 27% greater for GA2005. Plant volume decreased in GA2017 (35.6%) and GA2020 (23.8%). The shoot-to-root ratio was isomeric, except at 14 and 21 DAT, where an allometric growth towards shoot development was significant. Palmer amaranth biotypes responded differently to elevated CO2, and the impacts of temperature need further investigation on weed physiology. Thus, environmental and genetic background may affect the response of glyphosate-resistant and susceptible populations to climate change scenarios.
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Affiliation(s)
- Juliana de Souza Rodrigues
- Department of Crop and Soil Sciences, University of Georgia, 2360 Rainwater Road, Tifton, GA, 31793, USA.
| | - Donn Shilling
- Department of Crop and Soil Sciences, University of Georgia, 120 Carlton Street, Athens, GA, 30602, USA
| | - Viktor Tishchenko
- Department of Crop and Soil Sciences, University of Georgia, 1109 Experiment Street, Griffin, GA, 30223, USA
| | - Samantha Bowen
- Department of Crop and Soil Sciences, University of Georgia, 2360 Rainwater Road, Tifton, GA, 31793, USA
| | - Shiyuan Deng
- Department of Statistics, University of Georgia, 310 Herty Drive, Athens, GA, 30602, USA
| | - Daniel B Hall
- Department of Statistics, University of Georgia, 310 Herty Drive, Athens, GA, 30602, USA
| | - Timothy L Grey
- Department of Crop and Soil Sciences, University of Georgia, 2360 Rainwater Road, Tifton, GA, 31793, USA
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Kaur N, Snider JL, Paterson AH, Grey TL, Li C, Virk G, Parkash V. Variation in thermotolerance of photosystem II energy trapping, intersystem electron transport, and photosystem I electron acceptor reduction for diverse cotton genotypes. Plant Physiol Biochem 2023; 201:107868. [PMID: 37459803 DOI: 10.1016/j.plaphy.2023.107868] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Revised: 06/21/2023] [Accepted: 06/26/2023] [Indexed: 08/13/2023]
Abstract
Cotton breeding programs have focused on agronomically-desirable traits. Without targeted selection for tolerance to high temperature extremes, cotton will likely be more vulnerable to environment-induced yield loss. Recently-developed methods that couple chlorophyll fluorescence induction measurements with temperature response experiments could be used to identify genotypic variation in photosynthetic thermotolerance of specific photosynthetic processes for field-grown plants. It was hypothesized that diverse cotton genotypes would differ significantly in photosynthetic thermotolerance, specific thylakoid processes would exhibit differential sensitivities to high temperature, and that the most heat tolerant process would exhibit substantial genotypic variation in thermotolerance plasticity. A two-year field experiment was conducted at Tifton and Athens, Georgia, USA. Experiments included 10 genotypes in 2020 and 11 in 2021. Photosynthetic thermotolerance for field-collected leaf samples was assessed by determining the high temperature threshold resulting in a 15% decline in photosynthetic efficiency (T15) for energy trapping by photosystem II (ΦPo), intersystem electron transport (ΦEo), and photosystem I end electron acceptor reduction (ΦRo). Significant genotypic variation in photosynthetic thermotolerance was observed, but the response was dependent on location and photosynthetic parameter assessed. ΦEo was substantially more heat sensitive than ΦPo or ΦRo. Significant genotypic variation in thermotolerance plasticity of ΦEo was also observed. Identifying the weakest link in photosynthetic tolerance to high temperature will facilitate future selection efforts by focusing on the most heat-susceptible processes. Given the genotypic differences in environmental plasticity observed here, future research should evaluate genotypic variation in acclimation potential in controlled environments.
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Affiliation(s)
- Navneet Kaur
- Department of Crop and Soil Sciences, University of Georgia, Tifton, GA, 31794, USA.
| | - John L Snider
- Department of Crop and Soil Sciences, University of Georgia, Tifton, GA, 31794, USA
| | - Andrew H Paterson
- Department of Genetics, University of Georgia, Athens, GA, 30602, USA
| | - Timothy L Grey
- Department of Crop and Soil Sciences, University of Georgia, Tifton, GA, 31794, USA
| | - Changying Li
- School of Electrical and Computer Engineering, University of Georgia, Athens, GA, 30602, USA
| | - Gurpreet Virk
- Department of Crop and Soil Sciences, University of Georgia, Tifton, GA, 31794, USA
| | - Ved Parkash
- Department of Crop and Soil Sciences, University of Georgia, Tifton, GA, 31794, USA
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Johnston CR, Malladi A, Vencill WK, Grey TL, Culpepper AS, Henry G, Czarnota MA, Randell TM. Investigation of physiological and molecular mechanisms conferring diurnal variation in auxinic herbicide efficacy. PLoS One 2020; 15:e0238144. [PMID: 32857790 PMCID: PMC7454982 DOI: 10.1371/journal.pone.0238144] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Accepted: 08/10/2020] [Indexed: 11/18/2022] Open
Abstract
The efficacy of auxinic herbicides, a valuable weed control tool for growers worldwide, has been shown to vary with the time of day in which applications are made. However, little is known about the mechanisms causing this phenomenon. Investigating the differential in planta behavior of these herbicides across different times of application may grant an ability to advise which properties of auxinic herbicides are desirable when applications must be made around the clock. Radiolabeled herbicide experiments demonstrated a likely increase in ATP-binding cassette subfamily B (ABCB)-mediated 2,4-D and dicamba transport in Palmer amaranth (Amaranthus palmeri S. Watson) at simulated dawn compared to mid-day, as dose response models indicated that many orders of magnitude higher concentrations of N-1-naphthylphthalamic acid (NPA) and verapamil, respectively, are required to inhibit translocation by 50% at simulated sunrise compared to mid-day. Gas chromatographic analysis displayed that ethylene evolution in A. palmeri was higher when dicamba was applied during mid-day compared to sunrise. Furthermore, it was found that inhibition of translocation via 2,3,5-triiodobenzoic acid (TIBA) resulted in an increased amount of 2,4-D-induced ethylene evolution at sunrise, and the inhibition of dicamba translocation via NPA reversed the difference in ethylene evolution across time of application. Dawn applications of these herbicides were associated with increased expression of a putative 9-cis-epoxycarotenoid dioxygenase biosynthesis gene NCED1, while there was a notable lack of trends observed across times of day and across herbicides with ACS1, encoding 1-aminocyclopropane-1-carboxylic acid synthase. Overall, this research indicates that translocation is differentially regulated via specific protein-level mechanisms across times of application, and that ethylene release, a chief phytotoxic process involved in the response to auxinic herbicides, is related to translocation. Furthermore, transcriptional regulation of abscisic acid involvement in phytotoxicity and/or translocation are suggested.
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Affiliation(s)
- Christopher R. Johnston
- Department of Crop & Soil Sciences, University of Georgia, Athens, GA, United States of America
| | - Anish Malladi
- Department of Horticulture, University of Georgia, Athens, GA, United States of America
| | - William K. Vencill
- Department of Crop & Soil Sciences, University of Georgia, Athens, GA, United States of America
| | - Timothy L. Grey
- Department of Crop & Soil Sciences, University of Georgia, Tifton, GA, United States of America
| | - A. Stanley Culpepper
- Department of Crop & Soil Sciences, University of Georgia, Tifton, GA, United States of America
| | - Gerald Henry
- Department of Crop & Soil Sciences, University of Georgia, Athens, GA, United States of America
| | - Mark A. Czarnota
- Department of Horticulture, University of Georgia, Griffin, GA, United States of America
| | - Taylor M. Randell
- Department of Crop & Soil Sciences, University of Georgia, Tifton, GA, United States of America
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Grey TL, Eason KM, Wells L, Basinger NT. Effects of Temperature on Seed Germination of Plantago lanceolata and Management in Carya illinoinensis Production. Plants (Basel) 2019; 8:plants8090308. [PMID: 31466301 PMCID: PMC6784207 DOI: 10.3390/plants8090308] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/03/2019] [Revised: 08/21/2019] [Accepted: 08/23/2019] [Indexed: 11/17/2022]
Abstract
Plantago lanceolata L. (buckhorn plantain) is an encroaching winter weed described as one of the most successful noncultivated colonizing species around the world. Control of P. lanceolata in southeastern USA Carya illinoinensis (Wangenh.) K. Koch production has not been studied, nor has the role of temperature on germination using a thermal gradient table. Seed of P. lanceolata collected from a Georgia C. illinoinensis grove were tested for the effects of temperature over time to establish differences in effects on germination using a thermal gradient table. Temperatures ranged from 13.5 to 30.5 °C for 288 h. Cumulative P. lanceolata seed germination was 66% occurring at 17.8 °C at 242 h. Over the 288 h experiment, maximum P. lanceolata germination was 27% occurring at 17.0 °C, 187 h after initiation. Control of P. lanceolata with residual herbicides, or in combination with 2,4-dichlorophenoxyacetic acid (2,4-D) was evaluated in the interrow of C. illinoinensis groves containing Trifolium repens L., and in greenhouse experiments. Pre- and post-emergent herbicides included indaziflam, halosulfuron-methyl, and simazine applied alone, or in combination with 2,4-D in late autumn after P. lanceolata emergence in a C. illinoinensis grove. Indaziflam in combination with 2,4-D controlled P. lanceolata greater than 90% when applied in C. illinoinensis groves and greenhouse experiments. Halosulfuron-methyl and simazine applied alone, or in combination with 2,4-D, provided 67% or less P. lanceolata control in the grove experiments, and 83% or less in greenhouse experiments. Results suggested that herbicide applications should be made during the time when diurnal temperatures are between 15 and 30 °C, while abiding pre-harvest interval restrictions. Post- and pre-emergent herbicides may aid in controlling emerged weeds and reducing further weed emergence during the autumn of that year.
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Affiliation(s)
- Timothy L Grey
- College of Agriculture and Environmental Sciences, Department of Crop and Soil Sciences, University of Georgia, Tifton, GA 31793, USA.
| | - Kayla M Eason
- College of Agriculture and Environmental Sciences, Department of Crop and Soil Sciences, University of Georgia, Tifton, GA 31793, USA
| | - Lenny Wells
- College of Agriculture and Environmental Sciences, Horticulture Department, University of Georgia, Tifton, GA 31793, USA
| | - Nicholas T Basinger
- College of Agriculture and Environmental Sciences, Department of Crop and Soil Sciences, University of Georgia, Athens, GA 30602, USA
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Morris KA, Li X, Langston DB, Davis RF, Timper P, Grey TL. Fluensulfone sorption and mobility as affected by soil type. Pest Manag Sci 2018; 74:430-437. [PMID: 28869328 DOI: 10.1002/ps.4724] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/2016] [Revised: 07/24/2017] [Accepted: 08/26/2017] [Indexed: 06/07/2023]
Abstract
BACKGROUND Fluensulfone is a fluoroalkenyl chemical with activity against multiple genera of plant-parasitic nematodes. The adsorption, desorption, and mobility of fluensulfone were evaluated on multiple soils from the USA in laboratory and column experiments. RESULTS Adsorption data regressed to the logarithmic Freundlich equation resulted in isotherm values of 1.24 to 3.28. Soil adsorption of fluensulfone correlated positively with organic matter (0.67) and clay (0.34), but negatively with sand (-0.54). Fluensulfone soil desorption correlated to pH (0.38) and cation exchange capacity (0.44). Fluensulfone desorption from Arredondo sand soil was 26%, and from other soils ranged from 43 to 70%. In mobility experiments, fluensulfone in the leachate peaked at 3 h, gradually declining and becoming undetectable after 9 h. Recovery from leachate was 45% of the initial fluensulfone applied to the soil surface. In separate experiments, 30-cm-long soil columns were saturated with 1 L of water, and then segregated into three 10-cm sections. Fluensulfone recovery was 41, 34, 29, and 13% in Chualar sandy loam, Arredondo sand, Greenville sandy clay loam, and Tifton loamy sand, respectively, in the top 10-cm section. CONCLUSION Data indicated that soil organic matter and clay contents will affect sorption, mobility, and dissipation of fluensulfone. © 2017 Society of Chemical Industry.
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Affiliation(s)
| | - Xiao Li
- Crop, Soil and Environmental Sciences Department, Auburn University, AL, USA
| | - David B Langston
- Tidewater Agricultural Research and Extension Center, Suffolk, VA, USA
| | - Richard F Davis
- USDA-ARS, Crop Protection and Management Research Unit, Tifton, GA, USA
| | - Patricia Timper
- USDA-ARS, Crop Protection and Management Research Unit, Tifton, GA, USA
| | - Timothy L Grey
- Department of Crop and Soil Sciences, University of Georgia, Tifton, GA, USA
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Qu T, Grey TL, Csinos AS, Ji P. Translocation of Oxathiapiprolin in Bell Pepper Plants and Systemic Protection of Plants Against Phytophthora Blight. Plant Dis 2016; 100:1931-1936. [PMID: 30682987 DOI: 10.1094/pdis-03-16-0370-re] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Production of bell pepper is seriously affected by Phytophthora capsici, the causal agent of Phytophthora blight. Limited approaches are available for effective management of the disease. Oxathiapiprolin is a fungicide recently registered in the United States that suppressed P. capsici and reduced Phytophthora blight on bell pepper significantly in our previous studies. It is unknown whether oxathiapiprolin translocates in bell pepper plants systemically after application. Experiments were conducted to determine uptake of oxathiapiprolin by bell pepper plants and its systemic movement in the plant. Quantification of oxathiapiprolin in plant tissues was conducted by high-performance liquid chromatography (HPLC) that detected the compound sensitively and selectively. Percentage of recovery of oxathiapiprolin from plant tissues was calculated by comparing the quantities in plant tissues determined by HPLC with known quantities of the compound added to the plant tissues. Recovery rates of oxathiapiprolin from pepper plant tissues ranged from 87.0 to 119.3%. When oxathiapiprolin was applied to roots of bell pepper plants grown in hydroculture, the compound was detected in the root within 4 h and in the cotyledon, first true leaf, and second true leaf within 8 h. It was detectable in the top new leaf 48 h after application to the root. In greenhouse studies with bell pepper plants grown in pots, oxathiapiprolin was applied as a soil drench at 100 and 400 μg/ml. The compound was detected in the root within 3 days and in the stem and first true leaf within 6 days when applied at 100 μg/ml. It was detected in the root, stem, first true leaf, and top new leaf within 3 days when applied at 400 μg/ml. Phytophthora blight on pepper foliage was significantly reduced when oxathiapiprolin was applied as a soil drench at 100 or 400 μg/ml under greenhouse conditions. This is the first report indicating systemic movement of oxathiapiprolin in pepper plants that provides useful information for designing fungicide application programs for effective management of the disease.
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Affiliation(s)
- Tianli Qu
- Chemistry and Pharmacy College, Qingdao Agricultural University, Shandong 266109, China; and Department of Plant Pathology, University of Georgia, Tifton 31794
| | - Timothy L Grey
- Department of Crop and Soil Sciences, University of Georgia
| | | | - Pingsheng Ji
- Department of Plant Pathology, University of Georgia, Tifton 31794
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Chastain DR, Snider JL, Choinski JS, Collins GD, Perry CD, Whitaker J, Grey TL, Sorensen RB, van Iersel M, Byrd SA, Porter W. Leaf ontogeny strongly influences photosynthetic tolerance to drought and high temperature in Gossypium hirsutum. J Plant Physiol 2016; 199:18-28. [PMID: 27302003 DOI: 10.1016/j.jplph.2016.05.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2016] [Revised: 05/02/2016] [Accepted: 05/09/2016] [Indexed: 06/06/2023]
Abstract
Temperature and drought are major abiotic limitations to crop productivity worldwide. While abiotic stress physiology research has focused primarily on fully expanded leaves, no studies have investigated photosynthetic tolerance to concurrent drought and high temperature during leaf ontogeny. To address this, Gossypium hirsutum plants were exposed to five irrigation treatments, and two different leaf stages were sampled on three dates during an abnormally dry summer. Early in the growing season, ontogenic PSII heat tolerance differences were observed. Photosystem II was more thermotolerant in young leaves than mature leaves. Later in the growing season, no decline in young leaf net photosynthesis (PN) was observed as leaf temperature increased from 31 to 37°C, as average midday leaf water potential (ΨMD) declined from -1.25 to -2.03MPa. In contrast, mature leaf PN declined 66% under the same conditions. Stomatal conductance (gs) accounted for 84-98% of variability in leaf temperature, and gs was strongly associated with ΨMD in mature leaves but not in young leaves. We conclude that young leaves are more photosynthetically tolerant to heat and drought than mature leaves. Elucidating the mechanisms causing these ontogenic differences will likely help mitigate the negative impacts of abiotic stress in the future.
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Affiliation(s)
- Daryl R Chastain
- Delta Research and Extension Center, Plant and Soil Sciences, Mississippi State University, P.O. Box 197, Stoneville, MS 38776, USA.
| | - John L Snider
- Department of Crop and Soil Sciences, University of Georgia, 115 Coastal Way, Tifton, GA 31794, USA
| | - John S Choinski
- Department of Biology, University of Central Arkansas, 201 Donaghey, Conway, AR 72035, USA
| | - Guy D Collins
- Department of Crop Science, North Carolina State University, Upper Coastal Plains Research Station, 2811 Nobles Mill Pond Road, Rocky Mount, NC 27801, USA
| | - Calvin D Perry
- College of Agriculture and Environmental Sciences, University of Georgia, 8207 Georgia 37, Camilla, GA 31730, USA
| | - Jared Whitaker
- Department of Crop and Soil Sciences, University of Georgia, P.O. Box 8112, GSU Statesboro, GA 30460, USA
| | - Timothy L Grey
- Department of Crop and Soil Sciences, University of Georgia, 115 Coastal Way, Tifton, GA 31794, USA
| | - Ronald B Sorensen
- United States Department of Agriculture, Agricultural Research Service, National Peanut Research Laboratory, P.O. Box 509, Dawson, GA 39842, USA
| | - Marc van Iersel
- Department of Horticulture, University of Georgia, Athens, GA 30602, USA
| | - Seth A Byrd
- Texas A&M AgriLife Extension, Lubbock, TX 79403, USA
| | - Wesley Porter
- Department of Crop and Soil Sciences, University of Georgia, 115 Coastal Way, Tifton, GA 31794, USA
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Gaines TA, Zhang W, Wang D, Bukun B, Chisholm ST, Shaner DL, Nissen SJ, Patzoldt WL, Tranel PJ, Culpepper AS, Grey TL, Webster TM, Vencill WK, Sammons RD, Jiang J, Preston C, Leach JE, Westra P. Gene amplification confers glyphosate resistance in Amaranthus palmeri. Proc Natl Acad Sci U S A 2010; 107:1029-34. [PMID: 20018685 PMCID: PMC2824275 DOI: 10.1073/pnas.0906649107] [Citation(s) in RCA: 324] [Impact Index Per Article: 23.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The herbicide glyphosate became widely used in the United States and other parts of the world after the commercialization of glyphosate-resistant crops. These crops have constitutive overexpression of a glyphosate-insensitive form of the herbicide target site gene, 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS). Increased use of glyphosate over multiple years imposes selective genetic pressure on weed populations. We investigated recently discovered glyphosate-resistant Amaranthus palmeri populations from Georgia, in comparison with normally sensitive populations. EPSPS enzyme activity from resistant and susceptible plants was equally inhibited by glyphosate, which led us to use quantitative PCR to measure relative copy numbers of the EPSPS gene. Genomes of resistant plants contained from 5-fold to more than 160-fold more copies of the EPSPS gene than did genomes of susceptible plants. Quantitative RT-PCR on cDNA revealed that EPSPS expression was positively correlated with genomic EPSPS relative copy number. Immunoblot analyses showed that increased EPSPS protein level also correlated with EPSPS genomic copy number. EPSPS gene amplification was heritable, correlated with resistance in pseudo-F(2) populations, and is proposed to be the molecular basis of glyphosate resistance. FISH revealed that EPSPS genes were present on every chromosome and, therefore, gene amplification was likely not caused by unequal chromosome crossing over. This occurrence of gene amplification as an herbicide resistance mechanism in a naturally occurring weed population is particularly significant because it could threaten the sustainable use of glyphosate-resistant crop technology.
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Affiliation(s)
- Todd A. Gaines
- Department of Bioagricultural Sciences and Pest Management, Colorado State University, Fort Collins, CO 80523
| | - Wenli Zhang
- Department of Horticulture, University of Wisconsin, Madison, WI 53706
| | - Dafu Wang
- Monsanto Company, St. Louis, MO 63167
| | - Bekir Bukun
- Department of Bioagricultural Sciences and Pest Management, Colorado State University, Fort Collins, CO 80523
| | - Stephen T. Chisholm
- Department of Bioagricultural Sciences and Pest Management, Colorado State University, Fort Collins, CO 80523
| | - Dale L. Shaner
- Water Management Research Unit, US Department of Agriculture Agricultural Research Service (USDA-ARS), Fort Collins, CO 80526
| | - Scott J. Nissen
- Department of Bioagricultural Sciences and Pest Management, Colorado State University, Fort Collins, CO 80523
| | | | - Patrick J. Tranel
- Department of Crop Sciences, University of Illinois, Urbana, IL 61801
| | | | - Timothy L. Grey
- Crop and Soil Science Department, University of Georgia, Tifton, GA 31794
| | | | - William K. Vencill
- Crop and Soil Science Department, University of Georgia, Athens, GA 30602
| | | | - Jiming Jiang
- Department of Horticulture, University of Wisconsin, Madison, WI 53706
| | - Christopher Preston
- School of Agriculture, Food and Wine, University of Adelaide, Glen Osmond, SA 5064, Australia
| | - Jan E. Leach
- Department of Bioagricultural Sciences and Pest Management, Colorado State University, Fort Collins, CO 80523
| | - Philip Westra
- Department of Bioagricultural Sciences and Pest Management, Colorado State University, Fort Collins, CO 80523
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Ferrell JA, Vencill WK, Xia K, Grey TL. Sorption and desorption of flumioxazin to soil, clay minerals and ion-exchange resin. Pest Manag Sci 2005; 61:40-46. [PMID: 15593072 DOI: 10.1002/ps.956] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Flumioxazin adsorption kinetics were described using a Greenville sandy clay loam soil. Adsorption kinetics experiments showed that 72% of total herbicide was absorbed after 1 h of continuous shaking and continued to increase to 78% after 72 h. Flumioxazin adsorption was then tested on seven agriculturally important soils throughout the southern USA. Adsorption isotherms for all soils had K(f) (Freundlich distribution coefficient) values that ranged from 8.8 to 0.4, with many near 1.5. Soil organic matter content was the parameter most highly correlated with flumioxazin adsorption (r(2) = 0.95, P < 0.001). Sorption to clay minerals had K(f) values ranging from 50 for bentonite to 4.7 for kaolinite. However, normalizing K(f) for sorbent surface area revealed that aluminum hydroxide (gibbsite) possessed the greatest flumioxazin sorption per unit area. Sorption to anionic exchange resin (K(f) 676) was greater than cationic exchange resin (K(f) 42). Molecular model calculations were performed to elucidate why sorption was greater to anionic exchangers. These calculations indicated that a region of dense electronegativity exists on the 3-dione moiety of the molecule. This would lead to greater flumioxazin sorption by positively charged surface sites. Desorption isotherms from soil exhibited no effect of hysteresis. Desorption from clay minerals was very rapid and flumioxazin in solution was undetectable after three desorption steps. From these data it was concluded that flumioxazin can become readily available in soil solution with increase in soil water content.
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Affiliation(s)
- Jason A Ferrell
- Department of Agronomy, University of Florida, Gainesville, FL 32611, USA
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Abstract
To determine the degradation rates and degradation products of the herbicide flumioxazin in aqueous buffer solutions (pH 5, 7 and 9), its hydrolysis and photolysis were investigated at 30 degrees C in the dark, and in a growth chamber fitted with fluorescent lamps simulating the UV output of sunlight. The rate of hydrolysis of flumioxazin was accelerated by increasing pH. The t(1/2) values at pH 5, 7 and 9 were 16.4, 9.1 and 0.25 h, respectively. Two degradation products were detected and their structural assignments were made on the basis of LC-MS data. Degradation product I was detected in all buffer solutions while degradation product II was detected in acidic buffer only. Both degradation products appeared to be stable to further hydrolysis. After correcting for the effects of hydrolysis, the photolytic degradation rate also increased as a function of pH and was approximately 10 times higher at pH 7 than that at pH 5, showing t(1/2) values of 4.9 and 41.5 h, respectively. Degradation products formed by photolysis were the same as those formed by hydrolysis. Flumioxazin was degraded more extensively at high pH and should degrade in surface water.
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Affiliation(s)
- Jeong-Wook Kwon
- Mississippi State Chemical Laboratory, Mississippi State University, PO Box CR, Mississippi State, MS 39762-5622, USA
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Troy BS, Cooper RA, Robertson RN, Grey TL. An analysis of work postures of manual wheelchair users in the office environment. J Rehabil Res Dev 1997; 34:151-61. [PMID: 9108342] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The goal of this project was to examine the difficulties manual wheelchair users experience in office activities and ascertain whether such problems may be due to poor relationships between the equipment and the users. Sixty adult manual wheelchair users completed a questionnaire about problems encountered in office activities. Filing and writing were the most problematic activities for this group. Phase II of this study consisted of videotaping four subjects performing each activity in their personal office environments, and having them complete a second questionnaire on body-specific locations of discomfort. Videotaped postures and reports of discomfort were matched to determine the existence of poor equipment-user relationships. In filing, low back pain may have been due to bending forward to access lower drawers while seated. For writing, an inappropriate desk-wheelchair relationship that required subjects to bend forward with their arms on a surface that was too high may have caused back, shoulder, and neck discomfort.
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Affiliation(s)
- B S Troy
- Department of Biomedical Engineering, California State University, Sacramento 95819-6019, USA
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