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

INTERNATIONAL HERBICIDE-RESISTANT WEED DATABASE

HRAC GROUP 5 (LEGACY C1 C2) RESISTANT PROSTRATE PIGWEED
(Amaranthus blitoides)

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

Spain

INTRODUCTION		PROSTRATE PIGWEED
Prostrate Pigweed (Amaranthus blitoides) is a dicot weed in the Amaranthaceae family. In Spain this weed first evolved resistance to Group 5 (Legacy C1 C2) herbicides in 1986 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	Prostrate Pigweed
Species	Amaranthus blitoides
Group	PSII inhibitors - Serine 264 Binders HRAC Group 5 (Legacy C1 C2)
Herbicides	simazine
Location	Spain
Year	1986
Situation(s)	Orchards
Contributors - (Alphabetically)	Rafael De Prado
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NOTES ABOUT THIS BIOTYPE

GENERAL

Rafael De Prado

Target site mechanism of resistance.

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ACADEMIC ASPECTS

Confirmation Tests

Field, Greenhouse, and Laboratory trials comparing a known susceptible Prostrate Pigweed biotype with this Prostrate Pigweed 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 Prostrate Pigweed 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 Prostrate Pigweed 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 Prostrate Pigweed 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 Prostrate Pigweed Globally
(Amaranthus blitoides)

Country

FirstYear

Situation

Active Ingredients

Site of Action

Israel

1983

Cropland, and Roadsides

atrazine, and simazine

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

Israel

1991

Forests, and Roadsides

atrazine, chlorsulfuron, and simazine

Multiple Resistance: 2 Sites of Action
Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)

Spain

1986

Orchards

simazine

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

United States (Michigan)

2012

Mint

terbacil

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

Specific Papers about this Case

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Dominguez, C. ; Tena, M. ; Prado, R. de. 1994. Physiological and biochemical characteristics in triazine resistant biotypes of four Amaranthus species. Journal of Plant Physiology 143 : 632 - 636.

A comparative study was made of the photosynthetic activity, growth and productivity of triazine-resistant (R) and -susceptible (S) biotypes of A. albus, A. blitoides, A. hybridus and A. retroflexus collected from various areas in Spain. Fluorescence assays showed that herbicide treatment totally inhibited electron transport in S plants but not in R counterparts. Electron flow from Q_A to Q_B was lower in R plants, but no difference was observed for the electron flow rate through PSII + PSI nor for photosynthetic activity at different light intensities. Growth studies revealed that S biotypes were more vigorous than R biotypes in A. hybridus and A. retroflexus; R and S were similar in A. albus, but S biotypes of A. blitoides showed greater growth at the first development stage (3-week-old plants), although R and S plants were not significantly different at 5 and 6 weeks. No uniformity in productivity was observed across the 4 species..

Dominguez, C. ; Tena, M. ; Rodriguez, I. ; Prado, R. de. 1994. Lipid composition and chloroplast ultrastructure in triazine resistant biotypes of Amaranthus species. Journal of Plant Physiology 143 : 637 - 642.

A study was conducted of thylakoid membrane polar lipid composition and of chloroplast ultrastructure in triazine-resistant (R) and -susceptible (S) biotypes of four Amaranthus species (A. albus, A. blitoides, A. hybridus and A. retroflexus). R biotypes showed higher values for MGDG/DGDG (monogalactosyl-diacylglyceride/digalactosyl-diacylglyceride) and MGDG/PL (monogalactosyl-diacylglyceride/phospholipid) ratios. For fatty acid composition, when R were compared with S biotypes, they showed higher trans-hexadecenoic acid content in the PL fraction, higher linolenic acid content in TL, MGDG and DGDG, and lower linoleic acid content in TL, MGDG and DGDG. Studies of chloroplast ultrastructure revealed no appreciable difference between R and S biotypes with regard to the chlorophyll a/b ratio or the extent of thylakoid appression..

Prado, R. de ; Dominguez, C. ; Tena, M.. 1993. Triazine resistance in biotypes of Solanum nigrum and four Amaranthus species found in Spain. Weed Research (Oxford) 33 : 17 - 24.

Triazine-resistant (R) biotypes of Amaranthus albus, A. blitoides, A. hybridus, A. retroflexus and Solanum nigrum were found in Spain (A. retroflexus near Zaragoza and the others near Córdoba). The former 2 R biotypes were found in simazine-treated, non-tilled olive orchards, whereas the latter 3 came from atrazine-treated maize crops. All R biotypes survived rates of up to 5 kg/ha soil-incorporated atrazine or simazine, whereas their susceptible (S) or wild type counterparts were completely controlled by 0.25 kg (A. hybridus, A. retroflexus and S. nigrum) or 2.5 kg (A. albus and A. blitoides) atrazine. The higher tolerance to triazines of these latter S biotypes appeared to be attributable to herbicide detoxification. Photosynthetic electron transport in R biotypes was little affected by atrazine and simazine, but was inhibited by diuron, as shown by fluorescence induction measurements in whole leaves. In Hill reaction assays, the R biotypes showed a high level of resistance to atrazine and simazine (resistance factors in the range 350-900), and very slight resistance to diuron (resistance factors in the range 1.1-1.6). It is concluded that the R biotypes of the species studied have evolved a chloroplastic mode of resistance similar to that previously described for other triazine-resistant weed biotypes..

De Prado, R. ; Dominguez, C. ; Tena, M.. 1989. Triazine-resistant weeds found in Spain. : 67 - 79.

Resistant biotypes of Amaranthus albus, A. blitoides and Conyza bonariensis from simazine treated olive orchards and of A. hybridus, A. retroflexus, Chenopodium album, Setaria glauca [S. pumila] and Solanum nigrum from atrazine treated maize fields have been found in Córdoba, Andalucía and Zaragoza, Aragón, Spain. Growth in the presence of 0.25-0.5 kg/ha atrazine or simazine, chlorophyll fluorescence induction curves of leaves treated with 100 µM of atrazine, simazine or diuron, I₅₀ values for herbicide inhibition of PSII activity in isolated chloroplasts, the activity of various parts of the chloroplast electron chain and photosynthetic activity in intact leaves at various light intensities were all compared in resistant and susceptible biotypes. It was concluded that resistant biotypes have a chloroplast mode of resistance similar to other triazine-resistant weeds..

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Literature about Similar Cases

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Partovi, M. ; Zand, E. ; Alizadeh, H. M. ; Atri, A.. 2008. Investigation of herbicide resistance in pigweed (Amaranthus sp.) to chloridazon, desmedipham and mixture of these herbicides in some sugar beet fields of Iran. Applied Entomology and Phytopathology 75 : 88 (Pe).

In order to study the possibility of resistance in Amaranthus retroflexus L. and Amaranthus blitoides S. Wats biotypes to Chloridazon, Desmedipham and mixture of these two herbicides in sugar beet fields of West Azarbayejan, Isfahan, Pars, Khorasan and Khoozestan provinces, two experiments were conducted at greenhouse of Weed Research Department of Iranian Research Institute of Plant Protection during 2003 and 2004. The experimental design was completely randomized design using a factorial approach (27 biotypes of pigweed by 3 herbicides in greenhouse experiments and 6 biotypes of pigweed by one herbicide in bioassay trial) with 4 replications. The seeds that were suspected to be resistant at the recommended rates of herbicides were collected from the fields of these provinces and the susceptible seeds that had never been treated with herbicides were used in these experiments. In the greenhouse experiment for screening the suspected and susceptible biotypes, the percent dry weight and visual control were compared with untreated control biotypes. Any biotype was considered to be possibly resistant if the mean dry weight of the survivors was at least 50% of the untreated control plants. Six biotypes with inadequate control from greenhouse trial were selected and treated with six doses (0, 0.5, 1, 1.5, 2, 2.5, 3 g/l) of Chloridazon in bioassay test using petri-dish. For assessment of biotypes the root length were measured. The greenhouse experiments indicated that none of the biotypes were resistant to these herbicides, but the biotypes showed different responses to the herbicides and the biotypes such as FR(Am)1 and MR(Am.bl)5 were not completely controlled by Chloridazon. The biotypes such as ER(Am)2 and MR(Am.re)1 were less controlled by Desmedipham and also biotypes such as ER(Am)1, ER(Am)3 and MR(Am.bl)6 were inadequately controlled by mixture of two herbicides. Although the biotypes did not show resistance to the herbicides, the repeated use of PS II herbicides can lead to the emergence of resistant weed population. Results in bioassay test showed that with increasing dose of Chloridazon, the percent root length of all biotypes was decreased and herbicide resistance did not observe..

Calha, Im; Rocha, F; Ruiz-Santaella, Jr; Cruz-Hipolito, He. 2008. Two decades of herbicide resistance in the Iberian Peninsula. Journal Of Plant Diseases And Protection : 79 - 84.

About 20 years ago the first case of herbicide resistance in the Iberian Peninsula was reported: Amaranthus spp. R to atrazine in Spanish orchards. Since then, herbicide resistance has evolved in many weed species. Changes on agricultural practices namely new tillage systems, new rotational programmes, combined with the increased use of herbicides led to the selection of weed biotypes resistant to a wide range of herbicides. Nowadays such a problem affects the most important crops of this Peninsula (maize, wheat, rice, citrus and olive orchards), a spectrum of 26 weed species (14 dicotyledonous and 12 monocotyledonous) with biotypes resistant to several herbicides, namely to ALS inhibitors (Alisma plantago-aquatica, Cyperus difformis, Conyza albida, Aster squamatus, Avena sterilis and Papaver rhoeas), to ACCase inhibitors (Lolium rigidum), to PS II inhibitors (Amaranthus albus, A. blitoides, A. cruentus, A. hybridus, A. retroflexus, Bromus tectorum, Chenopodium album, Conyza bonariensis, C. canadensis, Echinochloa crus-galli, Polygonum lapathifolium, Setaria faberi, S. glauca, S. verticillata, S. viridis and Solanum nigrum), to ureas and amides (B. tectorum and Alopecurus myosuroides), to synthetic auxins (E. crus-galli) and more recently to the herbicide glyphosate (C. bonariensis; L. rigidum and L. multiflorum). Diversity of resistance mechanisms responsible for resistance in this Region involved target site resistance, enhanced rates of herbicide metabolism and multiple resistance. This paper reviews the actual situation in Iberian Peninsula and gives a perspective of adequate strategies for weed management considering the resistance mechanism, the availability of alternative herbicides and other cultural practices.

Costea, M. ; Tardif, F. J.. 2003. The biology of Canadian weeds. 126. Amaranthus albus L., A. blitoides S. Watson and A. blitum L. Canadian Journal of Plant Science 83 : 1039 - 1066.

A review of biological information is provided for three species of the genus Amaranthus: A. albus, A. blitoides and A. blitum. The last species has been revised taxonomically and a new subspecies for Canada is presented - A. blitum subsp. emarginatus subsp. nov. Amaranthus albus and A. blitoides are native to the USA and introduced to Canada. Both species are annual ruderal and agrestal weeds. During the past 100 years, the two species have spread across most provinces of Canada, but the greatest frequency and abundance have been recorded in Saskatchewan. Originating from Europe, Asia and North Africa, A. blitum was initially considered a non-persistent species. The present study shows that A. blitum especially, subsp. emarginatus, has continued to spread in Québec. The three species are alternate hosts to many insects, nematodes, viruses, bacteria and fungi that affect cultivated plants. In other areas (USA, Europe and Asia), the three species have developed multiple resistance to triazine and acetolactate-synthase-inhibiting herbicides..

Sibony, M. ; Rubin, B.. 2003. Molecular basis for multiple resistance to acetolactate synthase-inhibiting herbicides and atrazine in Amaranthus blitoides (prostrate pigweed). Planta 216 : 1022 - 1027.

Amaranthus blitoides S. Watson (prostrate pigweed) populations resistant to acetolactate synthase (ALS; EC 4.1.3.18)-inhibiting herbicides and triazines (SuR/TR) were found in Israel. The Ganot population was 6- to 790-fold more resistant to ALS inhibitors than the wild type due to an altered target site. Molecular analyses showed that the Ganot population was a mixture of two biotypes: (i) SuRA/TR in which domain A of the als gene differed in one nucleotide, resulting in substitution of Pro by Ser 188; (ii) SuRB/TR in which a mutation in domain B led to a substitution of Trp by Leu 569. The mutation in domain A resulted in resistance to all ALS inhibitors except imidazolinones, whereas the mutation in domain B led to resistance to all ALS inhibitors tested. SuRA/TR and SuRB/TR are multiple-resistant with an additional single mutation in the plastidic psbA gene that changes Ser 264 to Gly in the D1 protein, leading to triazine resistance. It is evident that plants within a population exposed to a similar selection pressure may show different patterns of cross-resistance due to three different point mutations. This unique phenomenon renders planning of rational weed management difficult or even impossible..

Sibony, M. ; Rubin, B.. 2003. The ecological fitness of ALS-resistant Amaranthus retroflexus and multiple-resistant Amaranthus blitoides. Weed Research (Oxford) 43 : 40 - 47.

Field studies were conducted to evaluate the ecological fitness of Amaranthus spp. biotypes that evolved resistance to either acetolactate synthase (ALS) inhibitors (A. retroflexus, SuR), to triazine herbicides (A. blitoides, SuS/TR), or to both (A. blitoides, SuR/TR), and estimate their ecological fitness under competitive conditions. The plants were grown in monoculture and in replacement series experiments. The examined mixtures were 100%S, 75%S/25%R, 50%S/50%R, 25%S/75%R and 100%R, at a constant stand of 400 plants m^-2. The SuR and SuS A. retroflexus biotypes attained similar shoot dry biomass per plant, biomass per plot and relative yield total (RYT)=1. In monoculture, the final shoot biomass of A. blitoides biotypes SuS/TS plants was higher than that of SuR/TR and SuS/TR. A negative effect of association was observed, amensalism, when SuS/TS was grown in mixture with SuR/TR, in favour of the wild type. However, SuR/TR and SuS/TR biomass was not influenced by the presence of the competitor. These data support the hypothesis that the ALS-resistance trait in A. retroflexus and A. blitoides is not associated with growth penalty and did not incur ecological cost in the field. We suggest that the cause of the observed reduction in growth rendering the SuS/TR and SuR/TR less fit than the wild type is due to the triazine resistance, and may facilitate their dissipation..

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