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

INTERNATIONAL HERBICIDE-RESISTANT WEED DATABASE

HRAC GROUP 5 (LEGACY C1 C2) RESISTANT RED AMARANTH
(Amaranthus cruentus)

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

Spain

INTRODUCTION		RED AMARANTH
Red Amaranth (Amaranthus cruentus) is a dicot weed in the Amaranthaceae family. In Spain this weed first evolved resistance to Group 5 (Legacy C1 C2) herbicides in 1989 and infests Corn (maize). 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 atrazine 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 Sep 15, 2000 )
Common Name	Red Amaranth
Species	Amaranthus cruentus
Group	PSII inhibitors - Serine 264 Binders HRAC Group 5 (Legacy C1 C2)
Herbicides	atrazine
Location	Spain
Year	1989
Situation(s)	Corn (maize)
Contributors - (Alphabetically)	Rafael De Prado
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NOTES ABOUT THIS BIOTYPE

GENERAL

Rafael De Prado

Mechanism of resistance is target site.

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ACADEMIC ASPECTS

Confirmation Tests

Field, Greenhouse, and Laboratory trials comparing a known susceptible Red Amaranth biotype with this Red Amaranth 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 Red Amaranth 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

The mechanism of resistance for this biotype is either unknown or has not been entered in the database. If you know anything about the mechanism of resistance for this biotype then please update the database.

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 Red Amaranth 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 Red Amaranth Globally
(Amaranthus cruentus)

Country

FirstYear

Situation

Active Ingredients

Site of Action

Spain

1989

Corn (maize)

atrazine

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

Literature about Similar Cases

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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.

Sattin, M. ; Zanin, G.. 2003. The situation of herbicide resistant weeds in Italy. Informatore Fitopatologico 53 : 24 - 27.

In Italy, 12 weed species (Amaranthus cruentus, Solanum nigrum, Chenopodium album, Avena sterilis subsp. ludoviciana, Alisma plantago-aquatica, Schoenoplectus mucronatus, Lolium spp., Papaver rhoeas, Phalaris paradoxa, Amaranthus retroflexus, Cyperus difformis and Echinochloa crus-galli) have evolved populations resistant to herbicides, although to date, the areas involved are quite limited. The cropping systems where resistance has developed are mainly monocultures (e.g. rice and durum wheat) or where short crop rotations are used. The herbicides involved are acetyl-CoA carboxylase inhibitors, acetolactate synthase inhibitors and PSII inhibitors. A brief history of herbicide resistance in Italy is presented and the major resistance management techniques for preventing its appearance and spread are outlined. Integrated weed management appears to be the best solution..

Prado, R. de ; Sanchez, M. ; Jorrin, J. ; Domínguez, C.. 1992. Negative cross-resistance to bentazone and pyridate in atrazine-resistant Amaranthus cruentus and Amaranthus hybridus biotypes. Pesticide Science 35 : 131 - 136.

Herbicide-resistant biotypes of A. cruentus and A. hybridus, collected from maize fields in NE Spain, survived rates of 5 kg/ha atrazine and 2-4 kg cyanazine but were controlled by lower doses of bentazone and pyridate than were susceptible biotypes. Such a negative cross-resistance was not found for chloroacetamides and MCPA. Chlorophyll fluorescence studies revealed that 10 mg/litre atrazine, bentazone, cyanazine and pyridate resulted in inhibition of photosynthetic electron transport in susceptible leaves, whereas in resistant plants, atrazine and cyanazine had no effect. Conversely, bentazone and pyridate inhibited photosynthesis to a greater extent in resistant than in susceptible biotypes. Isolated chloroplast membranes from resistant biotypes showed resistance factors of 366 and 501 to atrazine and 39 and 60 to cyanazine for A. hybridus and A. cruentus, resp. Bentazone and pyridate were found to be more effective in chloroplasts of the resistant biotypes than in those of susceptible plants. It is suggested that enhanced susceptibility to bentazone and pyridate in triazine-resistant A. cruentus and A. hybridus biotypes may be associated with the alteration of the D-1 polypeptide subunit of PS II, as found in triazine-resistant plants..

Prado, R. de ; Sanchez, M. ; Dominguez, C.. 1991. Resistance to s-triazines in Amaranthus cruentus and A. hybridus. I. Cross-resistance to herbicides. Mededelingen van de Faculteit Landbouwwetenschappen, Rijksuniversiteit Gent 56 : 799 - 805.

Atrazine- and cyanazine-resistance has been found in plants of A. hybridus and A. cruentus from 17 maize fields in NE Spain. Resistant biotypes of both species had survived atrazine at 5 kg/ha and cyanazine at 2-4 kg. Bentazone and pyridate were more effective against resistant than susceptible biotypes. At 10 ppm, atrazine, cyanazine, bentazone and pyridate inhibited photosynthetic electron transport in susceptible leaves. However, in resistant plants, the triazines did not block photosynthesis, while bentazone and pyridate inhibited it more strongly than in susceptible biotypes. Isolated chloroplast membranes from resistant biotypes showed resistance factors of 366 and 501 to atrazine and 39 and 60 to cyanazine for A. hybridus and A. cruentus, resp. Bentazone and pyridate were more effective in the chloroplasts of resistant biotypes than in those of susceptible plants. It was concluded that the changes causing resistance to triazines result in a negative resistance of bentazone and pyridate in A. hybridus and A. cruentus biotypes..

Zanin, G. ; Molle, I. ; Vazzana, C.. 1984. Distribution and spread of atrazine-resistant broadleaved weeds in Italy. : 273 - 280.

Atrazine-resistant broadleaved weeds were first recorded in Italy in 1978 and have since been spreading in Friuli, Trentino, Venezia, Lombardy and Piedmont, all N. of the Po. The most widespread spp. are Amaranthus cruentus, Solanum nigrum and Chenopodium album. Conditions which appear to favour the development and spread of resistant strains include high rainfall and light calcareous soils with subalkaline pH; these are found in marginal maize-growing areas where monoculture is not practised. There is a tendency for the resistant strains to spread southwards. The possible influence of a different weed flora in maize monoculture and of the need to combat annual grasses is discussed..

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