Prevalence and Mechanism of Atrazine Resistance in Waterhemp (Amaranthus tuberculatus) from Nebraska

Weed Science ◽  
2018 ◽  
Vol 66 (5) ◽  
pp. 595-602 ◽  
Author(s):  
Amaranatha Reddy Vennapusa ◽  
Felipe Faleco ◽  
Bruno Vieira ◽  
Spencer Samuelson ◽  
Greg R. Kruger ◽  
...  
Keyword(s):  
Integrated Management ◽  
Management Strategies ◽  
Point Mutations ◽  
D1 Protein ◽  
Target Site ◽  
Site Mutation ◽  
Protoporphyrinogen Oxidase ◽  
Atrazine Resistance ◽  
Gene Coding ◽  
Amaranthus Tuberculatus

AbstractResistance to atrazine (a photosystem II [PSII] inhibitor) is prevalent in waterhemp [Amaranthus tuberculatus(Moq.) J. D. Sauer] across the U.S. Midwest. Previous research suggests that target-site mutation or rapid metabolism of atrazine mediated by glutathioneS-transferase (GST) conjugation confers resistance inA. tuberculatusfrom Illinois. The distribution and mechanism of resistance to atrazine inA. tuberculatuspopulations from Nebraska (NE) are unknown. In this research we (1) evaluated the response and frequency of resistance in NEA. tuberculatusto soil-applied PSII (metribuzin and atrazine) and protoporphyrinogen oxidase (sulfentrazone) inhibitors, as well as POST-applied atrazine; and (2) determined the mechanism of atrazine resistance in NEA. tuberculatus. The chloroplasticpsbAgene, coding for a D1 protein (the target site of atrazine) was sequenced in 85 plants representing 27 populations ofA. tuberculatus. Furthermore, 24 plants selected randomly from four atrazine-resistant (AR) populations were used to determine the metabolism of atrazine via GST conjugation. Results from the soil-applied herbicide evaluation suggest that metribuzin (0.56 kg ai ha−1) and sulfentrazone (0.28 kg ai ha−1) were effective onA. tuberculatusmanagement. PRE and POST screenings against atrazine in the greenhouse indicate that atrazine (1.345 kg ai ha−1) was not effective on 39% and 73% of theA. tuberculatuspopulations evaluated (total of 109 and 85 populations, respectively), suggesting the prevalence of atrazine resistance inA. tuberculatusin NE. Sequence analysis of thepsbAgene found no known point mutations conferring atrazine resistance. However, the AR plants conjugated atrazine via GST activity faster than the known atrazine-susceptibleA. tuberculatus. Overall, the outcome of this study demonstrates the predominance of metabolism-based resistance to atrazine inA. tuberculatusfrom NE, which may predispose this species to evolve resistance to other herbicides. The use of integrated management strategies forA. tuberculatusis crucial for the control of this troublesome species.

scholarly journals Multiple-Herbicide Resistance in a 2,4-D–Resistant Waterhemp (Amaranthus tuberculatus) Population from Nebraska

Weed Science ◽  
2017 ◽  
Vol 65 (6) ◽  
pp. 743-754 ◽  
Author(s):  
Roberto J. Crespo ◽  
Ana B. Wingeyer ◽  
Greg R. Kruger ◽  
Chance W. Riggins ◽  
Patrick J. Tranel ◽  
...  
Keyword(s):  
D1 Protein ◽  
Acetolactate Synthase ◽  
Mechanisms Of Action ◽  
Target Site ◽  
Site Mutation ◽  
Auxin Receptor ◽  
Application Rates ◽  
Chlorimuron Ethyl ◽  
Als Inhibitors ◽  
Susceptible Populations

A 2,4-D-resistant tall waterhemp population (FS) from Nebraska was evaluated for resistance to other TIR1 auxin receptor herbicides and to herbicides having alternative mechanisms of action using greenhouse bioassays and genetic markers. Atrazine, imazethapyr, lactofen, mesotrione, glufosinate, and glyphosate were applied in a single-dose bioassay, and tissue was collected from marked plants for genetic analysis. The FS population was not injured by atrazine or by imazethapyr. Approximately 50% of the plants survived lactofen and were actively growing 28 d after treatment. The population was susceptible to mesotrione, glufosinate, and glyphosate. Ametryn, chlorimuron-ethyl, 2,4-D, aminocyclopyraclor, aminopyralid, and picloram were applied in dose–response studies. The FS population was sensitive to ametryn, and the Ser-264-Gly substitution in the D1 protein was not detected, suggesting the lack of response to atrazine is not due to a target-site mutation. The FS population exhibited less than 50% injury to chlorimuron-ethyl at application rates 20 times the labeled use rate. The Ser-653-Asn acetolactate synthase (ALS) substitution, which confers resistance to imidazolinone herbicides, was present in the FS population. However, this does not explain the lack of response to the sulfonylurea herbicide, chlorimuron-ethyl. Sequencing of a portion of thePPX2Lgene did not show the ΔG210 mutation that confers resistance to protoporphyrinogen oxidase–inhibiting herbicides, suggesting that other factors were responsible for waterhemp survival after lactofen application. The FS population was confirmed to be at least 30-fold resistant to 2,4-D relative to the susceptible populations. In addition, it was at least 3-fold less sensitive to aminopyralid and picloram, two other TIR1 auxin receptor herbicides, than the 2,4-D-susceptible populations were. These data indicated that the FS population contains both target and non–target site mechanisms conferring resistance to herbicides spanning at least three mechanisms of action: TIR1 auxin receptors, ALS inhibitors, and photosystem II inhibitors.

Distribution of the ΔG210 Protoporphyrinogen Oxidase Mutation in Illinois Waterhemp (Amaranthus tuberculatus) and an Improved Molecular Method for Detection

Weed Science ◽  
2015 ◽  
Vol 63 (4) ◽  
pp. 839-845 ◽  
Author(s):  
R. Joseph Wuerffel ◽  
Julie M. Young ◽  
Ryan M. Lee ◽  
Patrick J. Tranel ◽  
David A. Lightfoot ◽  
...  
Keyword(s):  
Amino Acid Position ◽  
Molecular Method ◽  
Site Mutation ◽  
Protoporphyrinogen Oxidase ◽  
Phenotypic Resistance ◽  
Detection Techniques ◽  
Specific Pcr ◽  
Allele Specific ◽  
Amaranthus Tuberculatus ◽  
Inhibitor Resistance

Molecular assays are often implemented by weed scientists for detection of herbicide-resistant individuals; however, the utility of these assays can be limited if multiple mechanisms of evolved resistance exist. Waterhemp resistant to protoporphyrinogen oxidase (PPO)– inhibiting herbicides is conferred by a target-site mutation in PPX2L (a gene coding for PPO), resulting in the loss of a glycine at position 210 (ΔG210). This ΔG210 mutation of PPX2L is the only known mechanism responsible for PPO-inhibitor resistance (PPO-R) in waterhemp from five states (Illinois, Indiana, Iowa, Kansas, and Missouri); however, a limited number of populations have been tested, especially in Illinois. To verify the ubiquity of the ΔG210 in PPO-R waterhemp populations in Illinois, a previously published allele-specific PCR (asPCR) was used for the detection of the ΔG210 mutation to associate this mutation with phenotypic resistance in 94 Illinois waterhemp populations. The ΔG210 mutation was detected in all populations displaying phenotypic resistance to lactofen (220 g ai ha−1), indicating the deletion is likely the only mechanism of resistance. With evidence that the ΔG210 mutation dominates PPO-R waterhemp biotypes, molecular detection techniques have considerable utility. Unfortunately, the previously published asPCR is time consuming, very sensitive to PCR conditions, and requires additional steps to eliminate the possibility of false negatives. To overcome these limitations, a streamlined molecular method using the TaqMan® technique was developed, utilizing allele-specific, fluorescent probes for high-throughput, robust discrimination of each allele (resistant and susceptible) at the 210th amino acid position of PPX2L.

scholarly journals Effect of Row Spacing and Seeding Rate on Russian Thistle (Salsola tragus) in Spring Barley and Spring Wheat

Plants ◽  
2021 ◽  
Vol 10 (1) ◽  
pp. 126
Author(s):  
Judit Barroso ◽  
Nicholas G. Genna
Keyword(s):  
Seed Production ◽  
Crop Yield ◽  
Spring Wheat ◽  
Plant Biomass ◽  
Integrated Management ◽  
Spring Barley ◽  
Management Strategies ◽  
Crop Productivity ◽  
Row Spacing ◽  
Seeding Rate

Russian thistle (Salsola tragus L.) is a persistent post-harvest issue in the Pacific Northwest (PNW). Farmers need more integrated management strategies to control it. Russian thistle emergence, mortality, plant biomass, seed production, and crop yield were evaluated in spring wheat and spring barley planted in 18- or 36-cm row spacing and seeded at 73 or 140 kg ha−1 in Pendleton and Moro, Oregon, during 2018 and 2019. Russian thistle emergence was lower and mortality was higher in spring barley than in spring wheat. However, little to no effect of row spacing or seeding rate was observed on Russian thistle emergence or mortality. Russian thistle seed production and plant biomass followed crop productivity; higher crop yield produced higher Russian thistle biomass and seed production and lower crop yield produced lower weed biomass and seed production. Crop yield with Russian thistle pressure was improved in 2018 with 18-cm rows or by seeding at 140 kg ha−1 while no effect was observed in 2019. Increasing seeding rates or planting spring crops in narrow rows may be effective at increasing yield in low rainfall years of the PNW, such as in 2018. No effect may be observed in years with higher rainfall than normal, such as in 2019.

scholarly journals Biological control agents in the integrated nematode management of potato in Egypt

2020 ◽  
Vol 30 (1) ◽  
Author(s):  
Mahfouz M. M. Abd-Elgawad
Keyword(s):  
Biological Control ◽  
Crop Yields ◽  
Integrated Management ◽  
Management Strategies ◽  
Economic Value ◽  
Potato Production ◽  
Parasitic Nematodes ◽  
Main Body ◽  
Biological Control Agents ◽  
Economic Significance

Abstract Background Potato represents Egypt’s largest vegetable export crop. Many plant-parasitic nematodes (PPNs) are globally inflicting damage to potato plants. In Egypt, their economic significance considerably varies according to PPN distribution, population levels, and pathogenicity. Main body This review article highlights the biology, ecology, and economic value of the PPN control viewpoint. The integration of biological control agents (BCAs), as sound and safe potato production practice, with other phytosanitary measures to manage PPNs is presented for sustainable agriculture. A few cases of BCA integration with such other options as synergistic/additive PPN management measures to upgrade crop yields are reviewed. Yet, various attributes of BCAs should better be grasped so that they can fit in at the emerging and/or existing integrated management strategies of potato pests. Conclusion A few inexpensive biocontrol products, for PPNs control on potato, versus their corresponding costly chemical nematicides are gathered and listed for consideration. Hence, raising awareness of farmers for making these biologicals familiar and easy to use will promote their wider application while offering safe and increased potato yield.

scholarly journals Altered toxicity of the prion protein peptide PrP106–126 carrying the Ala117→Val mutation

2000 ◽  
Vol 346 (3) ◽  
pp. 785-791 ◽  
Author(s):  
David R. BROWN
Keyword(s):  
Point Mutation ◽  
Prion Protein ◽  
Prion Diseases ◽  
Point Mutations ◽  
Human Sequence ◽  
Gene Coding ◽  
Normal Human ◽  
Microtubule Formation ◽  
Β Sheet ◽  
Prion Protein Peptide

The inherited prion diseases such as Gerstmann-Sträussler-Scheinker syndrome (GSS) are linked to point mutations in the gene coding for the cellular isoform of the prion protein (PrPC). One particular point mutation A117V (Ala117 → Val) is linked to a variable pathology that usually includes deposition of neurofibrillary tangles. A prion protein peptide carrying this point mutation [PrP106-126(117V)] was generated and compared with a peptide based on the normal human sequence [PrP106-126(117A)]. The inclusion of this point mutation increased the toxicity of PrP106-126 which could be linked to an increased β-sheet content. An assay of microtubule formation in the presence of tau indicated that PrP106-126 decreased the rate of microtubule formation that could be related to the displacement of tau. PrP106-126 carrying the 117 mutation was more efficient at inhibiting microtubule formation. These results suggest a possible mechanism of toxicity for protein carrying this mutation via destabilization of the cytoskeleton and deposition of tau in filaments, as observed in GSS.

scholarly journals Factors affecting Cyperus difformis seed germination and seedling emergence

2013 ◽  
Vol 31 (4) ◽  
pp. 823-832 ◽  
Author(s):  
A. Derakhshan ◽  
J. Gherekhloo
Keyword(s):  
Seed Germination ◽  
Integrated Management ◽  
Germination Rate ◽  
Seedling Emergence ◽  
Management Strategies ◽  
Soil Surface ◽  
Weed Species ◽  
Factors Affecting ◽  
Cyperus Difformis ◽  
Emergence Patterns

Specific knowledge about the dormancy, germination, and emergence patterns of weed species aids the development of integrated management strategies. Laboratory studies were conducted to determine the effect of several environmental factors on seed germination and seedling emergence of Cyperus difformis. Germination of freshly harvested seeds was inhibited by darkness; however, when seeds were subsequently transferred to complete light they germinated readily. Our results showed that 2 wk of cold stratification overcome the light requirement for germination. Seeds of C. difformis were able to germinate over a broad range of temperatures (25/15, 30/20, 35/25, and 40/30 ºC day/night). The response of germination rate to temperature was described as a non-linear function. Based on model outputs, the base, the optimum and the ceiling temperatures were estimated as 14.81, 37.72 and 45 ºC, respectively. A temperature of 120 ºC for a 5 min was required to inhibit 50% of maximum germination. The osmotic potential and salinity required for 50% inhibition of maximum germination were -0.47 MPa and 135.57 mM, respectively. High percentage of seed germination (89%) was observed at pH=6 and decreased to 12% at alkaline medium (pH 9) pH. Seeds sown on the soil surface gave the greatest percentage of seedling emergence, and no seedlings emerged from seeds buried in soil at depths of 1 cm.

Spider mites of agricultural importance in China, with focus on species composition during the last decade (2008–2017) 

2018 ◽  
Vol 23 (11) ◽  
pp. 2087 ◽  
Author(s):  
Peng-Yu Jin ◽  
Lu Tian ◽  
Lei Chen ◽  
Xiao-Yue Hong
Keyword(s):  
Species Composition ◽  
Dominant Species ◽  
Integrated Management ◽  
Management Strategies ◽  
Spider Mites ◽  
Management Program ◽  
Pest Species ◽  
Panonychus Citri ◽  
Important Species ◽  
River Region

Understanding pest species composition and their geographic distribution of important spider mites is fundamental and indispensable to establish an integrated pest management program. From a long-term survey during 2008–2017 in mainland China, we found that Tetranychus truncatus was the most frequently sampled Tetranychus spider mite (48.5%), followed by T. pueraricola (21.2%), T. kanzawai (12.5%), T. urticae (red) (5.7%) and T. urticae (green) (4.5%). Among them, T. truncatus was the major mite pest in the north of China. T. kanzawai was the dominant species in the Middle and Lower Reaches of the Yangtze River Region and T. pueraricola was the most important species in the southwest region. Other common and serious pests include Amphitetranychus viennensis (6.8%) and Panonychus citri (3.8%). This pattern was largely different from that in 2002–2004, when T. urticae (green and red) was believed to be the most serious mite pest. The factors involved in the change of species composition are not clear and need more exploration. We suggested that the increasing corn planting range may be partly responsible for the conversion of dominant species from other spider mites to T. truncatus. Further research on the mechanisms underlying the change of dominant species will help develop integrated management strategies.

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