<b>HRAC Group 5</b> <font size='2'> (Legacy C1 C2) </font> resistant Conyza bonariensis from Spain

INTERNATIONAL HERBICIDE-RESISTANT WEED DATABASE

HRAC GROUP 5 (LEGACY C1 C2) RESISTANT HAIRY FLEABANE
(Conyza bonariensis)

PSII inhibitors - Serine 264 Binders HRAC Group 5 (Legacy C1 C2)

Spain

INTRODUCTION		HAIRY FLEABANE
Hairy Fleabane (Conyza bonariensis) is a dicot weed in the Asteraceae family. In Spain this weed first evolved resistance to Group 5 (Legacy C1 C2) herbicides in 1987 and infests Orchards. Group 5 (Legacy C1 C2) herbicides are known as PSII inhibitors - Serine 264 Binders (Inhbition of Photosynthesis at PSll - Serine 264 Binders ). Research has shown that these particular biotypes are resistant to simazine and they may be cross-resistant to other Group 5 (Legacy C1 C2) herbicides. The 'Group' letters/numbers that you see throughout this web site refer to the classification of herbicides by their site of action. To see a full list of herbicides and HRAC herbicide classifications click here.

QUIK STATS (last updated Nov 18, 2000 )
Common Name	Hairy Fleabane
Species	Conyza bonariensis
Group	PSII inhibitors - Serine 264 Binders HRAC Group 5 (Legacy C1 C2)
Herbicides	simazine
Location	Spain
Year	1987
Situation(s)	Orchards
Contributors - (Alphabetically)	Rafael De Prado
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NOTES ABOUT THIS BIOTYPE

GENERAL

Rafael De Prado

Target site resistance.

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ACADEMIC ASPECTS

Confirmation Tests

Field, Greenhouse, and Laboratory trials comparing a known susceptible Hairy Fleabane biotype with this Hairy Fleabane biotype have been used to confirm resistance. For further information on the tests conducted please contact the local weed scientists that provided this information.

Genetics

Genetic studies on HRAC Group 5 resistant Hairy Fleabane have not been reported to the site. There may be a note below or an article discussing the genetics of this biotype in the Fact Sheets and Other Literature

Mechanism of Resistance

Studies on the mechanism of resistance of Group 5 (Legacy C1 C2) resistant Hairy Fleabane from Spain indicate that resistance is due to an altered target site. There may be a note below or an article discussing the mechanism of resistance in the Fact Sheets and Other Literature

Relative Fitness

There is no record of differences in fitness or competitiveness of these resistant biotypes when compared to that of normal susceptible biotypes. If you have any information pertaining to the fitness of Group 5 (Legacy C1 C2) resistant Hairy Fleabane from Spain please update the database.

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CONTRIBUTING WEED SCIENTISTS

RAFAEL DE PRADO

Universidad De Cordoba Qvimica Agricola Y Edafologa E T S Ingenieros Agronomos PO Box 119 Cordoba, E-14080, Andalusia Spain Email Rafael De Prado

ACKNOWLEDGEMENTS
The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in Spain have been instrumental in providing you this information. Particular thanks is given to Rafael De Prado for providing detailed information.

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Herbicide Resistant Hairy Fleabane Globally
(Conyza bonariensis)

Country

FirstYear

Situation

Active Ingredients

Site of Action

Argentina

2012

Soybean

glyphosate

Inhibition of Enolpyruvyl Shikimate Phosphate Synthase ( HRAC Group 9 (Legacy G)

Australia (New South Wales )

2010

Industrial sites, and Roadsides

glyphosate

Inhibition of Enolpyruvyl Shikimate Phosphate Synthase ( HRAC Group 9 (Legacy G)

Australia (Queensland)

2011

Roadsides

glyphosate

Inhibition of Enolpyruvyl Shikimate Phosphate Synthase ( HRAC Group 9 (Legacy G)

Australia (South Australia)

2011

Roadsides

glyphosate

Inhibition of Enolpyruvyl Shikimate Phosphate Synthase ( HRAC Group 9 (Legacy G)

Australia (New South Wales )

2016

Grapes

paraquat

PS I Electron Diversion ( HRAC Group 22 (Legacy D)

Brazil

2005

Corn (maize), Fruit, Soybean, and Wheat

glyphosate

Inhibition of Enolpyruvyl Shikimate Phosphate Synthase ( HRAC Group 9 (Legacy G)

Colombia

2006

Coffee

glyphosate

Inhibition of Enolpyruvyl Shikimate Phosphate Synthase ( HRAC Group 9 (Legacy G)

Egypt

1989

Unspecified

paraquat

PS I Electron Diversion ( HRAC Group 22 (Legacy D)

Greece

2010

Grapes, Olive, and Orchards

glyphosate

Inhibition of Enolpyruvyl Shikimate Phosphate Synthase ( HRAC Group 9 (Legacy G)

Israel

1993

Forests, and Industrial sites

atrazine, and simazine

PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)

Israel

1993

Forests, and Industrial sites

chlorsulfuron

Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)

Israel

2005

Roadsides

glyphosate

Inhibition of Enolpyruvyl Shikimate Phosphate Synthase ( HRAC Group 9 (Legacy G)

Japan

1989

Roadsides

diquat, and paraquat

PS I Electron Diversion ( HRAC Group 22 (Legacy D)

Jordan

2022

Palm oil

oxadiazon, oxyfluorfen, and paraquat

Multiple Resistance: 2 Sites of Action
PS I Electron Diversion ( HRAC Group 22 (Legacy D)
Inhibition of Protoporphyrinogen Oxidase ( HRAC Group 14 (Legacy E)

Portugal

2010

Orchards

glyphosate

Inhibition of Enolpyruvyl Shikimate Phosphate Synthase ( HRAC Group 9 (Legacy G)

South Africa

2003

Grapes, and Orchards

paraquat

PS I Electron Diversion ( HRAC Group 22 (Legacy D)

South Africa

2003

Grapes, and Orchards

glyphosate

Inhibition of Enolpyruvyl Shikimate Phosphate Synthase ( HRAC Group 9 (Legacy G)

Spain

1987

Orchards

simazine

PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)

Spain

2004

Orchards

glyphosate

Inhibition of Enolpyruvyl Shikimate Phosphate Synthase ( HRAC Group 9 (Legacy G)

Switzerland

2020

Grapes

glyphosate

Inhibition of Enolpyruvyl Shikimate Phosphate Synthase ( HRAC Group 9 (Legacy G)

United States (California)

2007

Roadsides

glyphosate

Inhibition of Enolpyruvyl Shikimate Phosphate Synthase ( HRAC Group 9 (Legacy G)

United States (California)

2009

Corn (maize), Grapes, Orchards, and Roadsides

glyphosate, and paraquat

Multiple Resistance: 2 Sites of Action
PS I Electron Diversion ( HRAC Group 22 (Legacy D)
Inhibition of Enolpyruvyl Shikimate Phosphate Synthase ( HRAC Group 9 (Legacy G)

United States (Oregon)

2023

Fallow, and Wheat

glyphosate

Inhibition of Enolpyruvyl Shikimate Phosphate Synthase ( HRAC Group 9 (Legacy G)

Literature about Similar Cases

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Matzrafi, M., T. W. Lazar, M. Sibony, and B. Rubin. 2015. Conyza species: distribution and evolution of multiple target-site herbicide resistances. Planta 242 : 259 - 267.

Conyza canadensis (CC) and Conyza bonariensis (CB) are troublesome weeds around the world. Extensive use of herbicides has led to the evolution of numerous Conyza spp. herbicide-resistant populations. Seeds of 91 CC and CB populations were collected across Israel. They were mostly found (86 %) in roadsides and urban habitats, two disturbed habitats that had been dramatically impacted by human activities, thus we classify these species as anthropogenic. Although pyrithiobac-sodium was only used in cotton fields, 90 % of Conyza spp. populations were identified as pyrithiobac-sodium resistant, suggesting possible natural resistance to pyrithiobac-sodium. CC21 and CC17 C. canadensis populations were highly resistant to all tested ALS inhibitors due to a substitution in the ALS gene from Trp574 to Leu. They were also atrazine resistant due to a substitution in the psbA gene from Ser264 to Gly. The high level of imazapyr and pyrithiobac-sodium resistance observed in the CC10 population was due to an Ala205 to Val substitution. However, high resistance to sulfometuron methyl and pyrithiobac-sodium in population CC6 was due to a point mutation at Pro197 to Ser. All resistant plants of CC21 population showed both psbA (Ser264 to Gly) and ALS (Trp574 to Leu) substitutions, leading us to the conclusion that the attempt to overcome resistance to one mode of action by overuse of another will most likely lead to multiple herbicide resistance. Furthermore, we concluded that only individuals that carry both mutations could survive the shift between the two modes of action and overcome the fitness cost associated with the PSII resistance..

Fernando Machado dos Santos , Leandro Vargas , Pedro Jacob Christoffoleti , Franciele Mariani. 2013. Evaluation of horseweed (Conyza sumatrensis) resistance to glyphosate in Rio Grande do Sul – Brazil. Abstract from Doctorate Dissertation : .

(Conyza bonariensisandConyza canadensis) recorded in Rio Grande do Sul State, however resistance ofConyza sumatrensisto glyphosate is registered only in Paraná State. This report has the objective of stating the presence ofConyza sumatrensisresistant to glyphosate biotypes in Rio Grande do Sul State Brazil. To support this report, researches to evaluate the occurrence of glyphosate resistance in horseweed biotypes, in Rio Grande do Sul State, and for that, seed samples were collected in soybean areas with unsatisfactory control, 25 biotypes. These biotypes were preliminary evaluated for resistance to glyphosate, applying a dose of 720 g/ha. Seeds from this first test of two selected biotypes of horseweed, which were not controlled in the first trial, with contrasting degree of susceptibility, were chosen to develop the second trial. The selected biotypes were grown after herbicide application (first trial) to seed production. It was also made, from these biotypes, herbarium specimens, which were sent to the Department of Biology of the Federal University of Santa Maria, where it was cataloged and classified by Dr. Thais Scotti Canto Dorow, plant systematic specialist, asConyza sumatrensis(Retz.) E. Walker (TELES; BORGES; HEIDEN, 2013) and subsequently deposited in the herbarium, SMDM under numbers SMDM 13950, 13951, 13952 and 13953. The biotypes selected, derived from seeds produced were evaluated by dose-response curves, using eight herbicide doses (0, 45, 90, 180, 360, 720, 1,440 and 2,880 g/ha) applied at growth stage of 3 to 4 leaves and/or 0.5 to 1.0 inch height. The experiments were conducted in a greenhouse in a completely randomized arrangement of treatments with four replications. The results indicate that the susceptible biotype to glyphosate has reduced 50 % of dry matter when used dose of 34.3 g/ha, compared with the resistant biotype, that requires 143.6 g/ha for the same control. The dose that provides 50% control of the susceptible population was 172 g/ha, compared with the resistant biotype that needs 2,028 g/ha for the same control, showing a resistance factor of 11.8..

Galon, L. ; Ferreira, E. A. ; Concenço, G. ; Silva, A. A. ; Silva, D. V. ; Silva, A. F. ; Aspiazú, I. ; Vargas, L.. 2013. Physiological characteristics of Conyza bonariensis biotypes resistant to glyphosate cultivated under competition. Planta Daninha 31 : 859 - 866.

The resistance of weeds to herbicides is related to metabolic, enzymatic, physiological and anatomical changes. Coupled with these changes, plants can increase or decrease their physiological activities, which can affect their growth and development. Thus, resistant biotypes may have a higher ecological adaptation in these environments and become predominant due to the elimination of sensitive plants. Under natural selection conditions, biotypes with greater ecological adaptation show higher production than less adapted biotypes. Thus, the aim of this work was to assess the effect of competition on the physiological characteristics of Conyza bonariensis biotypes susceptible and resistant to the herbicide glyphosate. The treatments consisted of plants of two biotypes of C. bonariensis - one proven to be resistant and one susceptible to glyphosate. In the center of the experimental unit, three seeds of the C. bonariensis biotype considered for treatment - resistant (R) or susceptible (S) - were sown, with the plant being surrounded by 0 (no competition), 1, 2, 3, 4, or 5 plants of the opposite biotype. The susceptible biotype presented a higher tolerance to competition with plants of the opposite biotype regarding the physiological characteristics evaluated. The resistant biotype of C. bonariensis has a physiological disadvantage compared to the susceptible one and, therefore, less potential for adaptability in the absence of the selection factor - the herbicide glyphosate..

Werth, J. ; Boucher, L. ; Thornby, D. ; Walker, S. ; Charles, G.. 2013. Changes in weed species since the introduction of glyphosate-resistant cotton. Crop & Pasture Science 64 : 791 - 798.

Weed management practices in cotton systems that were based on frequent cultivation, residual herbicides, and some post-emergent herbicides have changed. The ability to use glyphosate as a knockdown before planting, in shielded sprayers, and now over-the-top in glyphosate-tolerant cotton has seen a significant reduction in the use of residual herbicides and cultivation. Glyphosate is now the dominant herbicide in both crop and fallow. This reliance increases the risk of shifts to glyphosate-tolerant species and the evolution of glyphosate-resistant weeds. Four surveys were undertaken in the 2008-09 and 2010-11 seasons. Surveys were conducted at the start of the summer cropping season (November-December) and at the end of the same season (March-April). Fifty fields previously surveyed in irrigated and non-irrigated cotton systems were re-surveyed. A major species shift towards Conyza bonariensis was observed. There was also a minor increase in the prevalence of Sonchus oleraceus. Several species were still present at the end of the season, indicating either poor control and/or late-season germinations. These included C. bonariensis, S. oleraceus, Hibiscus verdcourtii and Hibiscus tridactylites, Echinochloa colona, Convolvulus sp., Ipomea lonchophylla, Chamaesyce drummondii, Cullen sp., Amaranthus macrocarpus, and Chloris virgata. These species, with the exception of E. colona, H. verdcourtii, and H. tridactylites, have tolerance to glyphosate and therefore are likely candidates to either remain or increase in dominance in a glyphosate-based system..

Trezzi, M. M. ; Balbinot Júnior, A. A. ; Benin, G. ; Debastiani, F. ; Patel, F. ; Miotto Júniorr, E.. 2013. Competitive ability of soybean cultivars with horseweed (Conyza bonariensis). Planta Daninha 31 : 543 - 550.

The existence of large areas infested with populations of Conyza spp. resistant to glyphosate in Brazil demands appropriate and integrated management strategies. This experiment aimed to identify soybean cultivars with greater competitive ability with horseweed plants and to determine plant characteristics associated with this ability. The experiment was arranged in a randomized complete block design with split plots. Seven soybean cultivars (CD 225 RR, BRS 232, CD 226 RR, NK 7054 RR, BMX Apollo RR, BRS 245 RR and BRS 255 RR) were allocated in the plots, and two interference situations (absence and 13.3 plants of Conyza m^-2, transplanted seven days before soybean planting) in the subplots. The average yield loss due to competition with horseweed was 25%. Cultivar CD 226 RR showed no significant grain yield loss due to competition, compared to the control without infestation, but showed the lowest average grain yield. The BRS 232 genotype showed loss of grain yield of only 14%, and presented positive plant height and leaf mass at 20 DAE, as well as dry matter of stems+branches in all evaluations, features related to its higher performance and greater ability to withstand competition with horseweed plants..

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