<b>HRAC Group 2</b> <font size='2'> (Legacy B) </font> resistant Sagittaria montevidensis from Australia, New South Wales

International Survey of Herbicide-Resistant Weeds

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Tuesday, April 16, 2024

HRAC GROUP 2 (LEGACY B) RESISTANT CALIFORNIA ARROWHEAD
(Sagittaria montevidensis)

Inhibition of Acetolactate Synthase HRAC Group 2 (Legacy B)

Australia, New South Wales

INTRODUCTION		CALIFORNIA ARROWHEAD
California Arrowhead (Sagittaria montevidensis) is a monocot weed in the Alismataceae family. In New South Wales this weed first evolved resistance to Group 2 (Legacy B) herbicides in 1994 and infests Rice. Group 2 (Legacy B) herbicides are known as Inhibition of Acetolactate Synthase (Inhibition of Acetolactate Synthase ). Research has shown that these particular biotypes are resistant to bensulfuron-methyl and they may be cross-resistant to other Group 2 (Legacy B) 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 Jun 06, 2004 )
Common Name	California Arrowhead
Species	Sagittaria montevidensis
Group	Inhibition of Acetolactate Synthase HRAC Group 2 (Legacy B)
Herbicides	bensulfuron-methyl
Location	Australia, New South Wales
Year	1994
Situation(s)	Rice
Contributors - (Alphabetically)	Jim Pratley
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NOTES ABOUT THIS BIOTYPE

AREAS FOUND

Jim Pratley

Irrigation areas of southern NSW.

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GENERAL

Jim Pratley

Little scope for chemical control of Arrowhead after bensulfuron is gone.

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ACADEMIC ASPECTS

Confirmation Tests

Greenhouse trials comparing a known susceptible California Arrowhead biotype with this California Arrowhead 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 2 resistant California Arrowhead 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 2 (Legacy B) resistant California Arrowhead from New South Wales please update the database.

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CONTRIBUTING WEED SCIENTISTS

JIM PRATLEY

Dean, Faculty Of Science & Agriculture Charles Sturt University School Of Agriculture Dept of Crop& Soil Sciences PO Box 646420, Wagga Wagga, 2678, New South Wales Australia Email Jim Pratley

ACKNOWLEDGEMENTS
The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in New South Wales have been instrumental in providing you this information. Particular thanks is given to Jim Pratley for providing detailed information.

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Herbicide Resistant California Arrowhead Globally
(Sagittaria montevidensis)

Country

FirstYear

Situation

Active Ingredients

Site of Action

Australia (New South Wales )

1994

Rice

bensulfuron-methyl

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

Brazil

1999

Rice

bispyribac-sodium, cyclosulfamuron, ethoxysulfuron, metsulfuron-methyl, and pyrazosulfuron-ethyl

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

Brazil

2009

Rice

bentazon, bispyribac-sodium, ethoxysulfuron, imazethapyr, metsulfuron-methyl, penoxsulam, and pyrazosulfuron-ethyl

Multiple Resistance: 2 Sites of Action
Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
PSII inhibitors - Histidine 215 Binders ( HRAC Group 6 (Legacy C3)

Brazil

2023

Rice

florpyrauxifen

Auxin Mimics ( HRAC Group 4 (Legacy O)

China

2003

Rice

bensulfuron-methyl, and pyrazosulfuron-ethyl

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

United States (California)

1993

Rice

bensulfuron-methyl

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

Literature about Similar Cases

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Domingos S. Eberhardt, José A. Noldin. 2011. Multiple Herbicide-Resistant Sagittaria montevidensis Population in Santa Catarina State (Brazil) Rice Fields. WSSA Abstracts : .

Sagittaria montevidensis (SAGMO) is a troublesome weed in irrigated rice areas in Santa Catarina. In the 1990’s, this weed was already disseminated in the rice fields and easily controlled with acetolactate synthase (ALS) inhibitors herbicides. The first case of SAGMO resistant to ALS herbicide was reported in 1999 and the best control option for these populations was bentazon, a photosystem II (PS II) inhibitor herbicide. In the last decade, bentazon became the main and almost the only option to control SAGMO and was used in more than 80% of the paddy rice areas. In 2008, a rice farmer from Ilhota County in the Itajai Valey, firstly reported problems to control SAGMO with bentazon, even using high rates. Field experiments were carried out in the 2008/09 and 2009/10 crop seasons at the farmer rice area to evaluate the sensitivity of the local SAGMO population to bentazon as well as to find alternatives to control these populations. Two experiments were also carried out under controlled conditions in 2009 and 2010 to confirm the multiple resistance of SAGMO populations to ALS and PS II herbicides (bentazon). In both experiments the herbicides (penoxsulam, pyrazosulfuron-ethyl, imazapic+imazethapyr and bentazon were evaluated at 0.5, 1, 2, 4 and 8 times the label rate. In the first field study (2008/09), the maximum control level with bentazon was 50% and 75%, respectively at 1 and 2X the label rate. The tank mixture of bentazon with other herbicides did not improve the efficacy. In the second field experiment (2009/10), bentazon applied at 4X rate controlled 78% (maximum) of SAGMO population, showing resistance of the population to bentazon. The maximum SAGMO control percentage using ALS inhibitors at 4X rate was 43%. The experiments carried out under controlled conditions also resulted in poor control of SAGMO populations. In 2009, SAGMO control with ALS inhibitors was lower than 50% for all herbicides and rates. Bentazon at 1, 4 or 8X rate resulted in 26%, 10% and 1% of surviving plants. In 2010, the percentage of SAGMO surviving plants was 83%, 96%, 71% and 51%, respectively for herbicides penoxsulam, pyrazosulfuron-ethyl, (imazapic+imazethapyr) and bentazon, applied at maximum rate (8X). The higher SAGMO surviving percentages in 2010 was due to the origin of the seeds. In 2009, SAGMO plants were obtained from the seed bank of the farmer area and in 2010, seedlings were established using seeds collected from surviving plants sprayed with bentazon in the year before. The data from these studies confirm the occurrence of SAGMO population cross-resistance to ALS and multiple-resistant to ALS and PS II (bentazon) in rice fields in Santa Catarina, Brazil.

Merotto Junior, A. ; Kupas, V. ; Nunes, A. L. ; Goulart, I. C. G. dos R.. 2010. Isolation of the ALS gene and investigation of the mechanism of herbicide resistance in Sagittaria montevidensis. Ciência Rural 40 : 2381 - 2384.

California arrowhead (Sagittaria montevidensis Cham. & Schlecht) is an aquatic weed often found in rice paddy fields. Several biotypes of California arrowhead resistant to ALS-inhibiting herbicides were found in Brazil and in several rice fields worldwide. The objective of this study was to sequence the ALS gene of California arrowhead and to identify the occurrence of mutations related to target site insensitivity as the mechanism of herbicide resistance. The plant material consisted of seeds collected in rice paddy fields located in the state of Santa Catarina, Brazil. Nine pairs of primers were designed for the amplification of the domains C, A and D of the ALS gene. PCR reactions with four pairs of primers resulted in amplification of fragments with size close to expected, ranging from 360 to 393 nucleotides. These sequences showed high homology to the standard ALS gene Arabdopsis thaliana and rice having only three point mutations. One of these mutations was Pro₁₉₇Phe that is related with herbicide resistance in several weeds. The sequences obtained indicated that the ALS gene evaluated was heterozygous. These results suggest the occurrence of insensitivity of the site of action as the mechanism of resistance to ALS-inhibitors herbicides in California arrowhead. The prevention and control of resistance to ALS-inhibitors in California arrowhead should be based on the rotation of herbicides with different mechanisms of action..

Concenço, G. ; Noldin, J. A. ; Lopes, N. F. ; Comiotto, A.. 2007. Aspects of Sagittaria montevidensis resistance to the ALS-inhibiting herbicide pirazosulfuron-ethyl. Planta Daninha 25 : 187 - 194.

Results are presented of an experiment conducted to evaluate the aspects related to the level and main absorption mechanism of pyrazosulfuron-ethyl to determine the resistance mechanism of an acetolactate synthase-resistant Sagittaria montevidensis ecotype..

Noldin, J. A. ; Eberhardt, D. S. ; Zunino, J. ; Rampelotti, F. T. ; Vieira, J.. 2005. Monitoring and management of herbicide resistant weeds in paddy rice in Santa Catarina state, southern Brazil. : 328 - 337.

The intensive use of herbicides for weed management in Santa Catarina state, southern Brazil, resulted in the selection of weed populations resistant to herbicides. Sagittaria montevidensis Cham. & Schlecht. was the first rice weed reported to be cross-resistant to ALS herbicides, including sulfonylureas, pyrimidinyloxybenzoic and imidazolinones, in Brazil. Nowadays, most of the rice área in Santa Catarina is infested with Sagittaria montevidensis resistant to ALS inhibitor herbicides. Echinochloa crus-galli (L.) Beauv. and E. crus-pavonis (H.B.K.) Schultes populations, resistant to quinclorac, were also detected in several fields. Weed resistance monitoring tests also showed Cyperus difformis L. cross-resistant to ALS inhibitors and Fimbristylis miliacea L. Vahl resistant to sulfonylureas. Bentazon and carfentrazone control Sagittaria montevidensis resistant to ALS inhibitor herbicides. Cyperus difformis and Fimbristylis miliacea populations, resistant to ALS inhibitors, can be controlled by bentazon, propanil or triclopyr. Propanil, bispiribac-sodium and ACCase inhibitors effectively control populations of Echinochloa crus-galli and E. crus-pavonis, resistant to quinclorac..

Eberhardt, D. S. ; Noldin, J. A. ; Stuker, H.. 2005. Only at different rates and application timing associated with water management in water-seeded clearfield rice. : 64 - 72.

Clearfield rice production is based on using an imidazolinone resistant cultivar. This technology represents a new alternative to control red rice (Oryza sativa L.) and other weeds infesting paddy rice fields in southern Brazil. A study was established to evaluate the efficacy of Only (imazethapyr+imazapic), at different rates and application timing, for weed control, under two water management systems and two rice genotypes. The study was carried out at Epagri, Itajaí Experimental Station, Santa Catarina state, southern Brazil, in the 2004/05 crop season. The experimental model was a split-splitplot design, using two water managements (main plot), ten herbicide treatments (splitplot) and two rice genotypes (split-splitplot) with three replications. Clearfield system efficacy depends on having rice cultivars well adapted to the rice crop system, good herbicide tolerance and/or good recovery from herbicide injury. Sequential application of Only at 1,5 L ha^-1 resulted in good weed control, including red rice. Flooding the rice field after the first herbicide application, improved weed control. Only did not control Sagittaria montevidensis Cham. & Schlecht., resistant to ALS inhibitor herbicides..

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