Glyphosate Resistance in Amaranthus viridis in Brazilian Citrus Orchards

Glyphosate is the main tool for weed management in Brazilian citrus orchards, where weeds, such as Conyza bonariensis and Digitaria insularis, have been found with resistance to this herbicide. Field prospections have allowed the identification of a possible new case of glyphosate resistance. In this work, the susceptibility levels to glyphosate on three Amaranthus viridis L. populations, with suspected resistance (R1, R2, and R-IAC), collected in citrus orchards from the São Paulo State, Brazil, as well as their accumulation rates of shikimic acid, were determined. The fresh weight of the susceptible population (S) was reduced by 50% (GR50) with ~30 g ea ha−1 glyphosate, while the GR50 values of the R populations were between 5.4 and 11.3 times higher than that for S population. The LD50 (herbicide dose to kill 50% of individuals of a weed population) values of the S population were ≤150 g ea ha−1 glyphosate, while the LD50 of the R populations ranged from 600 to 920 g ea ha−1. Based on the reduction of fresh weight and the survival rate, the R1 population showed the highest level of glyphosate resistance, which had GR50 and LD50 values of 248 and 918 g ea ha−1 glyphosate, respectively. The S population accumulated 240 µg shikimic acid at 1000 µM glyphosate, while the R1, R2, and R-IAC populations accumulated only 16, 43, and 33 µg shikimic acid, respectively (between 5.6 to 15 times less than the S population). Enzyme activity assays suggested that at least one target site-type mechanism was involved in resistance. This result revealed the first report of glyphosate resistance in A. viridis reported in the world.

Download Full-text

New Case of False-Star-Grass (Chloris distichophylla) Population Evolving Glyphosate Resistance

Agronomy ◽

10.3390/agronomy10030377 ◽

2020 ◽

Vol 10 (3) ◽

pp. 377 ◽

Cited By ~ 2

Author(s):

José G. Vázquez-García ◽

Sajedeh Golmohammadzadeh ◽

Candelario Palma-Bautista ◽

Antonia M. Rojano-Delgado ◽

José A. Domínguez-Valenzuela ◽

...

Keyword(s):

Weed Management ◽

Chemical Control ◽

Shikimic Acid ◽

Dry Weight ◽

Glyphosate Resistance ◽

Integrated Weed Management ◽

Resistance Level ◽

Susceptible Population ◽

First Case

Chloris distichophylla, suspected of glyphosate resistance (GR), was collected from areas of soybean cultivation in Rio Grande do Sul, Brazil. A comparison was made with a susceptible population (GS) to evaluate the resistance level, mechanisms involved, and control alternatives. Glyphosate doses required to reduce the dry weight (GR50) or cause a mortality rate of 50% (LD50) were around 5.1–3 times greater in the GR population than in the GS population. The shikimic acid accumulation was around 6.2-fold greater in GS plants than in GR plants. No metabolized glyphosate was found in either GR or GS plants. Both populations did not differ in the enzyme 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) basal activity or in vitro inhibition of EPSPS activity by glyphosate (I50). The maximum glyphosate absorption was observed at 96 hours after treatment (HAT), which was twofold higher in the GS plants than in the GR plants. This confirms the first case of glyphosate resistance in C. distichophylla. In addition, at 96 HAT, the GS plants translocated more 14C-glyphosate than the GR ones. The best options for the chemical control of both C. distichophylla populations were clethodim, quizalofop, paraquat, glufosinate, tembotrione, diuron, and atrazine. The first case of glyphosate resistance in C. distichophylla was due to impaired uptake and translocation. Chemical control using multiple herbicides with different modes of action (MOA) could be a tool used for integrated weed management (IWM) programs.

Download Full-text

Identification of glyphosate resistance in Lolium rigidum Gaudin

Pesticidi i fitomedicina ◽

10.2298/pif1104393p ◽

2011 ◽

Vol 26 (4) ◽

pp. 393-399 ◽

Cited By ~ 2

Author(s):

Danijela Pavlovic ◽

Charlie Reinhardt ◽

Igor Elezovic ◽

Sava Vrbnicanin

Keyword(s):

Shikimic Acid ◽

Glyphosate Resistance ◽

The Other ◽

Population Difference ◽

Lolium Rigidum ◽

Susceptible Population ◽

Dry Biomass ◽

Rigid Ryegrass ◽

Susceptible Populations ◽

Two Populations

Glyphosate resistance was found in Lolium rigidum Gaudin (Rigid ryegrass, LOLRI) in South Africa. Suspected glyphosate-resistant L. rigidum populations were collected and grown under greenhouse conditions. The plants were sprayed with a range of doses of glyphosate 35 days after planting and shoot dry biomass was determined 17 days after herbicide treatment. Based on the dose-response experiment conducted in the greenhouse, one population of L. rigidum suspected to be resistant to glyphosate was approximately 5.3 fold more resistant than susceptible population. The other population was 2.8 fold more resistant than susceptible population. Difference between the two suspected resistant populations was 1.9 fold. All plants were treated with glyphosate (1000 g a.i. ha-1) and shikimic acid was extracted 2, 4 and 6 days after treatment. The plants of susceptible populations accumulated more shikimic acid than other two populations.

Download Full-text

Glyphosate Resistance Confirmation and Field Management of Red Brome (Bromus rubens L.) in Perennial Crops Grown in Southern Spain

Agronomy ◽

10.3390/agronomy11030535 ◽

2021 ◽

Vol 11 (3) ◽

pp. 535

Author(s):

José G. Vázquez-García ◽

Patricia Castro ◽

Hugo E. Cruz-Hipólito ◽

Teresa Millan ◽

Candelario Palma-Bautista ◽

...

Keyword(s):

Weed Management ◽

Shikimic Acid ◽

Southern Spain ◽

Integrated Weed Management ◽

Fresh Weight ◽

Perennial Crops ◽

Resistance Factors ◽

Bromus Rubens ◽

Scientific Report ◽

Postemergence Herbicides

The excessive use of the herbicide glyphosate on annual and perennial crops grown in Southern Spain has caused an increase in resistant weed populations. Bromus rubens has begun to spread through olive and almond cultivars due to low glyphosate control over these species, whereas previously it had been well controlled with field dose (1080 g ae ha−1). Characterization using Simple Sequence Repeat (SSR) markers confirmed the presence of B. rubens collected in Andalusia. A rapid shikimic acid accumulation screening showed 17 resistant (R) populations with values between 300 and 700 µg shikimate g−1 fresh weight and three susceptible (S) populations with values between 1200 and 1700 µg shikimate g−1 fresh weight. In dose–response experiments the GR50 values agreed with previous results and the resistance factors (RFs: GR50 R/GR50 S (Br1)) were between 4.35 (Br9) and 7.61 (Br19). Foliar retention assays shown no differences in glyphosate retention in both R and S populations. The tests carried out in a resistant field (Br10) demonstrated the control efficacy of pre-emergence herbicides since flazasulfuron in the tank mix with glyphosate had up to 80% control 15 to 120 days after application (DAA) and grass weed postemergence herbicides, such as propaquizafop + glyphosate and quizalofop + glyphosate, had up to 90% control 15 to 90 DAA. Results confirm the first scientific report of glyphosate-resistant B. rubens worldwide; however, the use of herbicides with another mode of action (MOA) is the best tool for integrated weed management.

Download Full-text

Stressful Conditions Affect Seed Quality in Glyphosate Resistant Conyza bonariensis (L.)

Agronomy ◽

10.3390/agronomy10111706 ◽

2020 ◽

Vol 10 (11) ◽

pp. 1706

Author(s):

Gabriel da Silva Amaral ◽

Ricardo Alcántara-de la Cruz ◽

Flávia Regina da Costa ◽

Cileide Maria Medeiros Coelho ◽

Rafael De Prado ◽

...

Keyword(s):

Seed Quality ◽

Shikimic Acid ◽

Seed Viability ◽

Accelerated Aging ◽

Glyphosate Resistance ◽

Cold Test ◽

High Temperature Stress ◽

Stress Tests ◽

Germination Potential ◽

Conyza Bonariensis

Conyza bonariensis (L.) Cronquist is one of the main glyphosate-resistant weeds in no-till fields in Brazil. Here, the seed quality of glyphosate-resistant (R) and -susceptible (S) C. bonariensis biotypes, collected from different sites, was evaluated under stressful conditions by different seed tests. Glyphosate resistance was confirmed by dose-response and shikimate accumulation assays. The resistance factors were 6.9 (R1/S1), 4.5 (R2/S2), and 5.8 (R3/S3). Biotypes S1, S2, and S3 accumulated 2.7, 2.4, and 2.8 times more shikimic acid than biotypes R1, R2, and R3, respectively. Stress-free seed viability and germination potential ranged from 39% to 57% and from 37% to 57%, respectively, with no difference between R and S biotypes within each collection site. Seed incubation at 8 °C over 7 days (cold test) promoted greater germination in S biotypes (54% to 79%) compared to R ones (28% to 39%). In the accelerated aging tests (incubation at 42 °C over 48 hours), the germination decreased in both S (11% to 27%) and R (6% to 16%) biotypes. In the high-temperature stress tests, there were no differences in germination within biotypes at 35 and 45 °C; however, at 60 °C, the germination of the S1, R1, S2, R2, S3, and R3 biotypes was reduced by approximately 51%, 54%, 63%, 59%, 40%, and 30%, respectively. Under non-stressful conditions, germination potential and seed viability were similar in R and S biotypes; however, under cold or heat stress conditions, R biotypes reduced their germination rates, revealing that glyphosate resistance causes a fitness penalty in C. bonariensis at the seed level. However, because seed viability was not determined after experiments, it cannot be stated that such reduction in germination was due to the death or only a dormant phase of the seeds.

Download Full-text

Environmental cues affecting horseweed (Conyza canadensis) growth type and their sensitivity to glyphosate

Weed Science ◽

10.1017/wsc.2021.27 ◽

2021 ◽

pp. 1-35

Author(s):

John A. Schramski ◽

Christy L. Sprague ◽

Eric L. Patterson

Keyword(s):

Soil Moisture ◽

Glyphosate Resistance ◽

Single Parent ◽

Environmental Cues ◽

Conyza Canadensis ◽

Growth Type ◽

Susceptible Population ◽

Water Imbibition ◽

Growth Types ◽

Winter Annual

Abstract Horseweed [Conyza canadensis (L.) Cronquist] is a facultative winter annual weed that can emerge from March to November in Michigan. Fall emerging C. canadensis overwinters as a rosette, while spring emerging C. canadensis skips the rosette stage and immediately grows upright upon emergence. In Michigan, primary emergence recently shifted from fall to spring/summer and therefore from a rosette to an upright growth type. Growth chamber experiments were conducted to determine 1) whether both C. canadensis growth types could originate from a single parent and 2) if common environmental cues can influence growth type. Variations in temperature, photoperiod, competition, shading, and soil moisture only resulted in the rosette growth type in four C. canadensis populations originating from seed collected from a single parent of the upright growth type. However, a vernalization period of four weeks following water imbibition, but prior to germination, resulted in the upright growth type. Dose-response experiments were conducted to determine whether glyphosate sensitivity differed between C. canadensis growth types generated from a single parent of the upright growth type. Upright type C. canadensis from known glyphosate-resistant populations ISB-18 and MSU-18 were four and three-fold less sensitive to glyphosate than their rosette siblings, respectively. Interestingly, differences in glyphosate sensitivity was not observed between growth types from the susceptible population. These results suggest that while C. canadensis populations shift from winter to summer annual lifecycles, concurrent increases in glyphosate resistance could occur.

Download Full-text

Maize MAIZE YIELD AS AFFECTED BY METHODS OF TILLAGE AND WEED MANAGEMEMNT

JOURNAL OF WEED SCIENCE RESEARCH ◽

10.28941/pjwsr.v27i1.892 ◽

2021 ◽

Vol 27 (1) ◽

pp. 51-66

Author(s):

Haseeb Ahmad

Keyword(s):

Grain Yield ◽

Weed Control ◽

Weed Management ◽

Management Practices ◽

Block Design ◽

Dry Weight ◽

Maize Yield ◽

Control Methods ◽

Fresh Weight ◽

Maize Crop

An experiment entitled: Maize yield as affected by methods of tillage and weed control methods was conducted at Agronomy Research Farms, The University of Agriculture Peshawar during summer 2016. The study was conducted in randomized complete block design (RCBD) with split plot arrangement having four replications. Tillage practices 1) Chisel plough + rotavator 2) Mouldboard plough + rotavator 3) Cultivator + rotavator and 4) Rotavator were assigned to main plots. Weed management practices included 1) Control, 2) Hoeing 15 days after sowing 3) Hoeing 15 and 30 days after sowing 4) Hoeing 15, 30 and 45 days after sowing, and 4) Herbicide (nicosulfuron) were kept into the subplots. The results revealed that chisel plough + rotavator has significantly reduced weeds m-2 (122, 101 and 125 weeds m-2), weeds fresh weight (19.73 g m-2, 116.35 g m-2 and 252.56 g m-2) and weeds dry weight (6.83 g m-2, 38.69 g m-2 and 80.61 g m-2) at 30, 45 and 60 days after sowing, respectively. The operation of chisel plough + rotavator has produced tallest plants (221.22 cm) with maximum grain rows ear-1 (16), grain yield (3586 kg ha-1) and shelling percentage (78.14%). Among weed control methods, hoeing 15, 30 and 45 days after sowing revealed maximum plant height (226.41 cm), grain rows ear-1 (16), grain yield (3604 kg ha-1) and shelling percentage (79.11%). All weed control methods have showed significant reduction in weeds m-2, weeds fresh weight and weeds dry weight. Interaction was also found significant for weeds m-2 at 60 DAS and grain yield of maize. Lowest weeds (56 weeds m-2) at 60 DAS and highest grain yield (4569 kg ha-1) was recorded when seedbed was prepared with chisel plough + rotavator with 3 hoeings (hoeing 15, 30 and 45 days after sowing). It is concluded that treatment of chisel plough + rotavator and hoeing 15, 30 and 45 days after sowing has significantly produced maximum grain yield of maize crop.

Download Full-text

Postemergence Weed Management Systems for Peanuts (Arachis hypogaea)

Weed Technology ◽

10.1017/s0890037x00025331 ◽

1990 ◽

Vol 4 (2) ◽

pp. 239-244 ◽

Cited By ~ 8

Author(s):

John W. Wilcut ◽

Glenn R. Wehtje ◽

T. Vint Hicks ◽

Tracy A. Cole

Keyword(s):

Arachis Hypogaea ◽

Weed Management ◽

Field Studies ◽

Management Systems ◽

Fresh Weight ◽

Net Returns ◽

Pitted Morningglory

Field studies were conducted from 1985 to 1987 to evaluate postemergence herbicide systems with preemergence systems to control Texas panicum, Florida beggarweed, sicklepod, and pitted morningglory in peanuts. Adding paraquat at 0.14 kg ai/ha to postemergence herbicide systems reduced fresh weight of Florida beggarweed 92% (18% increase over the same systems without paraquat), sicklepod 95% (21% increase), and pitted morningglory 95% (11% increase). Herbicide systems containing paraquat improved peanut yields by 230 kg/ha and net returns by $52/ha over herbicide systems not containing paraquat. Fluazifop-P and sethoxydim systems reduced Texas panicum fresh weight (at least 96%) more than a preemergence system (92% reduction) that used benefin applied preplant incorporated and alachlor plus naptalam and dinoseb applied at cracking (GC) or a postemergence system that used alachlor and naptalam plus dinoseb GC and paraquat applied early postemergence (86% reduction). Systems containing fluazifop-P provided greater yields (4190 kg/ha) and net returns ($383/ha) than systems containing sethoxydim (4010 kg/ha, $305/ha) when averaged across all rates of application.

Download Full-text

Growth ofKochia scoparia, Salsola iberica, andTriticum aestivumvaries with temperature

Weed Science ◽

10.1017/s0043174500092043 ◽

1999 ◽

Vol 47 (4) ◽

pp. 435-439 ◽

Cited By ~ 3

Author(s):

Cathy A. Nord ◽

Calvin G. Messersmith ◽

John D. Nalewaja

Keyword(s):

Weed Management ◽

Growth Response ◽

Management Practices ◽

Fresh Weight ◽

Herbicide Application ◽

Kochia Scoparia ◽

Optimum Time ◽

Influence Of Temperature On ◽

Response To Temperature ◽

Salsola Iberica

Information on the influence of temperature on growth of springTriticum aestivumL. (wheat) relative toKochia scoparia(L.) Schrad. (kochia) andSalsola ibericaSennen and Pau (Russian thistle) could lead to more efficient weed management practices. An experiment was conducted to determine the growth of springT. aestivum, K. scoparia, andS. ibericaat 15, 23, and 30 C in growth chambers. Fresh weight at 15 C was greater for springT. aestivumthan forK. scopariaandS. iberica.Conversely, fresh weights at 23 or 30 C were greater forK. scopariaandS. ibericathan for springT. aestivum.Growth response to temperature is consistent with the physiological characteristics for photosynthesis of springT. aestivum, a C3plant, andK. scopariaandS. iberica, which are C4plants. The results indicate that cool temperatures that usually occur for early-seeded springT. aestivumwould give springT. aestivumthe competitive advantage overK. scopariaorS. iberica.Additionally, growing degree day (GDD) equations for height development ofK. scopariaandS. ibericawere determined and could be used to determine the optimum time for postemergence herbicide application.

Download Full-text

Modeling the Evolution of Glyphosate Resistance in Barnyardgrass (Echinochloa crus-galli) in Cotton-Based Production Systems of the Midsouthern United States

Weed Technology ◽

10.1614/wt-d-13-00013.1 ◽

2013 ◽

Vol 27 (3) ◽

pp. 475-487 ◽

Cited By ~ 19

Author(s):

Muthukumar V. Bagavathiannan ◽

Jason K. Norsworthy ◽

Kenneth L. Smith ◽

Paul Neve

Keyword(s):

United States ◽

Weed Management ◽

Production Systems ◽

Relative Effectiveness ◽

Glyphosate Resistance ◽

Case Scenario ◽

Management Options ◽

Worst Case ◽

Resistance Evolution ◽

Initial Frequency

Glyphosate-resistant (GR) weeds have been a prime challenge to the sustainability of GR cotton-based production systems of the midsouthern United States. Barnyardgrass is known to be a high-risk species for evolving herbicide resistance, and a simulation model was developed for understanding the likelihood of glyphosate resistance evolution in this species in cotton-based systems. Under a worst-case scenario of five glyphosate applications in monoculture GR cotton, the model predicts resistance evolution in about 9 yr of continuous glyphosate use, with about 47% risk by year 15. A unique insight from this model is that management in response to GR Palmer amaranth in this system (a reactive response) provided a proactive means to greatly reduce the risks of glyphosate resistance evolution in barnyardgrass. Subsequent model analysis revealed that the risk of resistance is high in fields characterized by high barnyardgrass seedbank levels, seedling emergence, and seed production per square meter, whereas the risk is low in fields with high levels of postdispersal seed loss and annual seedbank loss. The initial frequency of resistance alleles was a high determinant of resistance evolution (e.g., 47% risk at year 15 at an initial frequency of 5e−8vs. 4% risk at 5e−10). Monte Carlo simulations were performed to understand the influence of various glyphosate use patterns and production practices in reducing the rate and risk of glyphosate resistance evolution in barnyardgrass. Early planting and interrow cultivation are useful tools. Crop rotation is effective, but the diversity of weed management options practiced in the rotational crop is more important. Diversifying weed management options is the key, yet application timing and the choice of management option is critical. Model analyses illustrate the relative effectiveness of a number of diversified glyphosate use strategies in preventing resistance evolution and preserving the long-term utility of glyphosate in midsouthern U.S. cotton-based production systems.

Download Full-text

Interference of Selected Palmer Amaranth (Amaranthus palmeri) Biotypes in Soybean (Glycine max)

International Journal of Agronomy ◽

10.1155/2012/168267 ◽

2012 ◽

Vol 2012 ◽

pp. 1-7 ◽

Cited By ~ 3

Author(s):

Aman Chandi ◽

David L. Jordan ◽

Alan C. York ◽

Susana R. Milla-Lewis ◽

James D. Burton ◽

...

Keyword(s):

Glycine Max ◽

Acetolactate Synthase ◽

Dry Weight ◽

Glyphosate Resistance ◽

Palmer Amaranth ◽

Amaranthus Palmeri ◽

Fresh Weight ◽

Row Crops ◽

Soybean Yield ◽

Competitive Disadvantage

Palmer amaranth (Amaranthus palmeriS. Wats.) has become difficult to control in row crops due to selection for biotypes that are no longer controlled by acetolactate synthase inhibiting herbicides and/or glyphosate. Early season interference in soybean [Glycine max(L.) Merr.] for 40 days after emergence by three glyphosate-resistant (GR) and three glyphosate-susceptible (GS) Palmer amaranth biotypes from Georgia and North Carolina was compared in the greenhouse. A field experiment over 2 years compared season-long interference of these biotypes in soybean. The six Palmer amaranth biotypes reduced soybean height similarly in the greenhouse but did not affect soybean height in the field. Reduction in soybean fresh weight and dry weight in the greenhouse; and soybean yield in the field varied by Palmer amaranth biotypes. Soybean yield was reduced 21% by Palmer amaranth at the established field density of 0.37 plant m−2. When Palmer amaranth biotypes were grouped by response to glyphosate, the GS group reduced fresh weight, dry weight, and yield of soybean more than the GR group. The results indicate a possible small competitive disadvantage associated with glyphosate resistance, but observed differences among biotypes might also be associated with characteristics within and among biotypes other than glyphosate resistance.

Download Full-text