Molecular Basis of Evolved Resistance to Glyphosate and Acetolactate Synthase-Inhibitor Herbicides in Kochia (Kochia scoparia) Accessions from Montana

The rapid evolution and spread of glyphosate-resistant (GR) kochia in the Northern Great Plains is an increasing threat to GR cropping systems and conservation tillage practices common in this region. GR kochia accessions with 4.6- to 11-fold levels of resistance to glyphosate have recently been reported in Montana. Those GR kochia accessions were also suspected to be resistant to acetolactate synthase (ALS) inhibitors, i.e., multiple herbicide-resistant (MHR) kochia. In this research, the level of resistance to the ALS-inhibitor herbicides (sulfonylureas) and the molecular mechanisms conferring resistance to glyphosate and ALS-inhibitor herbicides in MHR kochia was investigated. On the basis of whole-plant dose–response assays, MHR kochia accessions (GIL01, JOP01, and CHES01) were 9.3- to 30-fold more resistant to premixed thifensulfuron methyl + tribenuron methyl + metsulfuron methyl than the susceptible (SUS) accession. In an in vivo leaf-disk shikimate assay, MHR plants accumulated less shikimate than the SUS plants at a discriminate dose of 100 μM glyphosate. Sequencing of the conserved region ofEPSPSrevealed no target-site mutation at Thr102or Pro106residue. MHR kochia accessions had increased relativeEPSPSgene copies (~ 4 to 10) compared with the SUS accession (single copy). Furthermore, MHR kochia accumulated higher EPSPS protein compared with the SUS plants. Resistance to the ALS-inhibitor herbicides was conferred by Pro197amino acid substitution (proline to glutamine).EPSPSgene amplification and a single target-site mutation at Pro197inALSgene confer resistance to glyphosate and ALS-inhibitor herbicides, respectively, in MHR kochia accessions from Montana. This is the first confirmation of occurrence of MHR kochia in Montana.

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Investigating the resistance levels and mechanisms to penoxsulam and cyhalofop-butyl in barnyardgrass (Echinochloa crus-galli) from Ningxia province, China

Weed Science ◽

10.1017/wsc.2021.37 ◽

2021 ◽

pp. 1-25

Author(s):

Qian Yang ◽

Xia Yang ◽

Zichang Zhang ◽

Jieping Wang ◽

Weiguo Fu ◽

...

Keyword(s):

Herbicide Resistance ◽

Molecular Mechanisms ◽

Acetolactate Synthase ◽

Rice Fields ◽

Target Site ◽

Herbicide Resistant ◽

Susceptible Populations ◽

High Level ◽

Als Inhibitor ◽

Encoding Genes

Abstract Barnyardgrass (Echinochloa crus-galli) is a noxious grass weed which infests rice fields and causes huge crop yield losses. In this study, we collected twelve E. crus-galli populations from rice ﬁelds of Ningxia province in China and investigated the resistance levels to acetolactate synthase (ALS) inhibitor penoxsulam and acetyl-CoA carboxylase (ACCase) inhibitor cyhalofop-butyl. The results showed that eight populations exhibited resistance to penoxsulam and four populations evolved resistance to cyhalofop-butyl. Moreover, all of the four cyhalofop-butyl-resistant populations (NX3, NX4, NX6 and NX7) displayed multiple-herbicide-resistance (MHR) to both penoxsulam and cyhalofop-butyl. The alternative herbicides bispyribac-sodium, metamifop and fenoxaprop-P-ethyl cannot effectively control the MHR plants. To characterize the molecular mechanisms of resistance, we ampliﬁed and sequenced the target-site encoding genes in resistant and susceptible populations. Partial sequences of three ALS genes and six ACCase genes were examined. A Trp-574-Leu mutation was detected in EcALS1 and EcALS3 in two high-level (65.84- and 59.30-fold) penoxsulam-resistant populations NX2 and NX10, respectively. In addition, one copy (EcACC4) of ACCase genes encodes a truncated aberrant protein due to a frameshift mutation in E. crus-galli populations. None of amino acid substitutions that are known to confer herbicide resistance were detected in ALS and ACCase genes of MHR populations. Our study reveals the widespread of multiple-herbicide resistant E. crus-galli populations at Ningxia province of China that exhibit resistance to several ALS and ACCase inhibitors. Non-target-site based mechanisms are likely to be involved in E. crus-galli resistance to the herbicides, at least in four MHR populations.

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Basis for Herbicide Resistance in Canadian Populations of Wild Oat (Avena fatua)

Weed Science ◽

10.1614/ws-d-11-00110.1 ◽

2012 ◽

Vol 60 (1) ◽

pp. 10-18 ◽

Cited By ~ 72

Author(s):

Hugh J. Beckie ◽

Suzanne I. Warwick ◽

Connie A. Sauder

Keyword(s):

Herbicide Resistance ◽

Economic Effects ◽

Target Site ◽

Northern Great Plains ◽

Western Canada ◽

Wild Oat ◽

Site Mutation ◽

P450 Monooxygenase ◽

Als Inhibitors ◽

Als Inhibitor

Wild oat is the second-most abundant, but most economically important, weed across the Canadian Prairies of western Canada. Despite the serious economic effects of resistance to acetyl-CoA carboxylase (ACC) or acetolactate synthase (ALS) inhibitors or both in this weed throughout the Northern Great Plains of North America, little research has examined the basis for herbicide resistance. We investigated target-site and nontarget-site mechanisms conferring ACC- and ALS-inhibitor resistance in 16 wild oat populations from across western Canada (four ACC-inhibitor resistant, four ALS-inhibitor resistant, and eight ACC- and ALS-inhibitor resistant). TheACC1mutations were found in 8 of the 12 ACC inhibitor-resistant populations. The Ile1781Leu mutation was detected in three populations, the Trp2027Cys and Asp2078Gly mutations were in two populations each, and the Trp1999Cys, Ile2041Asn, Cys2088Arg, and Gly2096Ser substitutions were in one population each. Three populations had twoACC1mutations. Only 2 of the 12 ALS inhibitor-resistant populations had anALStarget-site mutation—Ser653Thr and Ser653Asn substitutions. This is the first global report ofALStarget-site mutations inAvenaspp. and four previously undocumentedACC1mutations in wild oat. Based on these molecular analyses, seedlings of five ACC + ALS inhibitor-resistant populations (one with anACC1mutation; four with noACCorALSmutations) were treated with malathion, a known cytochrome P450 monooxygenase inhibitor, followed by application of one of four ACC- or ALS-inhibiting herbicides. Malathion treatment often resulted in control or suppression of these populations, suggesting involvement of this enzyme system in contributing to resistance to both ACC and ALS inhibitors.

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Acetolactate synthase inhibitor-resistant stinkweed (Thlaspi arvense L.) in Alberta

Canadian Journal of Plant Science ◽

10.4141/cjps06019 ◽

2007 ◽

Vol 87 (4) ◽

pp. 965-972 ◽

Cited By ~ 14

Author(s):

H. J. Beckie ◽

L. M. Hall ◽

F. J. Tardif ◽

G. Séguin-Swartz

Keyword(s):

Herbicide Resistance ◽

Dominant Gene ◽

Acetolactate Synthase ◽

Target Site ◽

Cross Resistance ◽

Resistance Pattern ◽

Site Mutation ◽

Thlaspi Arvense ◽

Synthase Inhibitor ◽

Als Inhibitor

Two stinkweed populations from southern and central Alberta were not controlled by acetolactate synthase (ALS)-inhibiting herbicides in 2000. This study reports on their cross-resistance to ALS-inhibiting herbicides, molecular basis of resistance, and inheritance of resistance. Both putative herbicide-resistant biotypes responded similarly to increasing doses of the herbicides. The biotypes were highly resistant to ethametsulfuron and exhibited a low level of resistance to metsulfuron and imazethapyr. However, both biotypes were not resistant to florasulam, a triazolopyrimidine ALS inhibitor, or sulfometuron, a non-selective sulfonylurea ALS inhibitor. The cross-resistance pattern was consistent with the confirmed target-site mutation. Sequence analysis of the ALS gene detected a Pro197Leu mutation in both biotypes. Similar to many other ALS inhibitor-resistant weed biotypes, resistance was conferred by a single dominant gene. This study confirms the first global occurrence of herbicide resistance in this species. Key words: ALS-inhibitor resistance, ALS sequence, herbicide resistance, target-site mutation

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Molecular Basis of Resistance to Herbicides Inhibiting Acetolactate Synthase in Two Rigid Ryegrass (Lolium rigidum) Populations from Australia

Weed Science ◽

10.1614/ws-d-11-00147.1 ◽

2012 ◽

Vol 60 (2) ◽

pp. 172-178 ◽

Cited By ~ 9

Author(s):

Shiv S. Kaundun ◽

Richard P. Dale ◽

Géraldine C. Bailly

Keyword(s):

Molecular Basis ◽

Molecular Mechanisms ◽

Codon Position ◽

Acetolactate Synthase ◽

Target Site ◽

Weed Species ◽

Site Mutation ◽

Sulfometuron Methyl ◽

Whole Plant ◽

Field Samples

Acetolactate Synthase- (ALS) inhibiting herbicides are important components for the control of ryegrass species infesting cereal-cropping systems worldwide. Although resistance to ALS herbicides in ryegrasses has evolved more than 25 yr ago, few studies have been dedicated to elucidate the molecular mechanisms involved. To this end, we have investigated the molecular basis of chlorsulfuron, sulfometuron-methyl, and imazapyr resistance in AUS5 and AUS23, two ryegrass populations from Australia. Comparison between whole-plant herbicide assays and DNA sequencing results showed that resistance to the nonmetabolizable herbicide sulfometuron-methyl was associated with four different proline mutations at ALS codon position 197 (P197) in AUS23. In addition to three P197 amino acid changes impacting on the efficacies of the two sulfonylurea herbicides, the tryptophan to leucine target-site mutation at ALS codon position 574 (W574L) was present in AUS5, conferring resistance to both sulfometuron-methyl and imazapyr. The samples were also characterized by non target-site-based resistance impacting on the metabolizable herbicide chlorsulfuron only. Interestingly, compound mutant heterozygotes threonine/serine at ALS position 197, and plants with double mutations at positions 197 and 574 were detected, thus reflecting the ability of this outcrossing species to accumulate mutant alleles. Whole-plant dose-response assays conducted on predetermined wild-type and mutant genotypes originating from the same populations allowed for a more precise estimation of the dominant and very high levels of resistance associated with the proline to serine target-site mutation at ALS codon position 197 (P197S) and W574L mutations. The two highly efficient polymerase chain reaction- (PCR) based derived cleaved amplified polymorphic sequence (dCAPS) markers developed here will allow for quick confirmation of 197 and 574 ALS target-site resistance in ryegrass species field samples and also contribute to identify populations characterized by other likely resistance mechanisms in this important weed species.

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Glyphosate- and acetolactate synthase inhibitor-resistant kochia (Bassia scoparia) control in field pea

Canadian Journal of Plant Science ◽

10.1139/cjps-2021-0178 ◽

2021 ◽

Author(s):

Alysha T Torbiak ◽

Robert Blackshaw ◽

Randall N Brandt ◽

Bill Hamman ◽

Charles M. Geddes

Keyword(s):

Great Plains ◽

Field Experiments ◽

Rapid Evolution ◽

Acetolactate Synthase ◽

Field Pea ◽

Visible Injury ◽

Crop Harvest ◽

Selection For ◽

Synthase Inhibitor ◽

Als Inhibitor

Kochia [Bassia scoparia (L.) A.J. Scott] is an invasive C4 tumbleweed in the Great Plains of North America, where it impedes crop harvest and causes significant crop yield losses. Rapid evolution and spread of glyphosate- and acetolactate synthase (ALS) inhibitor-resistant kochia in western Canada limit the herbicide options available for control of these biotypes in field pea (Pisum sativum L.); one of the predominant pulse crops grown in this region. Field experiments were conducted near Lethbridge, Alberta in 2013-2015 and Coalhurst, Alberta in 2013-2014 to determine which herbicide options effectively control glyphosate- and ALS inhibitor-resistant kochia in field pea. Visible injury of field pea was minor (0-4%) in all environments except for Lethbridge 2013, where pre-plant (PP) flumioxazin and all treatments containing post-emergence (POST) imazamox/bentazon resulted in unacceptable (14-23%) pea visible injury. Herbicide impacts on pea yield were minor overall. Carfentrazone + sulfentrazone PP and saflufenacil PP followed by imazamox/bentazon POST resulted in ≥80% visible control of kochia in all environments, while POST imazamox/bentazon alone resulted in ≥80% reduction in kochia biomass in all environments compared with the untreated control (albeit absent of statistical difference in Coalhurst 2014). These results suggest that layering the protoporhyrinogen oxidase-inhibiting herbicides saflufenacil or carfentrazone + sulfentrazone PP with the ALS- and photosystem II-inhibiting herbicide combination imazamox/bentazon POST can effectively control glyphosate- and ALS inhibitor-resistant kochia in field pea while also mitigating further selection for herbicide resistance through the use of multiple effective herbicide modes-of-action.

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Multiple herbicide resistance in California Italian ryegrass (Lolium perenne ssp. multiflorum): characterization of ALS-inhibiting herbicide resistance

Weed Science ◽

10.1017/wsc.2019.1 ◽

2019 ◽

Vol 67 (3) ◽

pp. 273-280 ◽

Cited By ~ 4

Author(s):

Parsa Tehranchian ◽

Vijay K. Nandula ◽

Maor Matzrafi ◽

Marie Jasieniuk

Keyword(s):

Lolium Perenne ◽

Herbicide Resistance ◽

Resistance Mechanism ◽

Acetolactate Synthase ◽

Target Site ◽

Italian Ryegrass ◽

Resistance Level ◽

Als Inhibitors ◽

Inhibitor Resistance ◽

Als Inhibitor

AbstractMultiple resistance to glyphosate, sethoxydim, and paraquat was previously confirmed in two Italian ryegrass [Lolium perenne L. ssp. multiflorum (Lam.) Husnot] populations, MR1 and MR2, in northern California. Preliminary greenhouse studies revealed that both populations were also resistant to imazamox and mesosulfuron, both of which are acetolactate synthase (ALS)-inhibiting herbicides. In this study, three subpopulations, MR1-A (from seed of MR1 plants that survived a 16X rate of sethoxydim), MR1-P (from seed of MR1 plants that survived a 2X rate of paraquat), and MR2 (from seed of MR2 plants that survived a 16X rate of sethoxydim), were investigated to determine the resistance level to imazamox and mesosulfuron, evaluate other herbicide options for the control of these multiple resistant L. perenne ssp. multiflorum, and characterize the underlying ALS-inhibitor resistance mechanism(s). Based on LD50 values, the MR1-A, MR1-P, and MR2 subpopulations were 38-, 29-, 8-fold and 36-, 64-, and 3-fold less sensitive to imazamox and mesosulfuron, respectively, relative to the susceptible (Sus) population. Only MR1-P and MR2 plants were cross-resistant to rimsulfuron, whereas both MR1 subpopulations were cross-resistant to imazethapyr. Pinoxaden (ACCase inhibitor [phenylpyrazoline 'DEN']) only controlled MR2 and Sus plants at the labeled field rate. However, all plants were effectively controlled (>99%) with the labeled field rate of glufosinate. Based on I50 values, MR1-A, MR-P, and MR2 plants were 712-, 1,104-, and 3-fold and 10-, 18-, and 5-fold less responsive to mesosulfuron and imazamox, respectively, than the Sus plants. Sequence alignment of the ALS gene of resistant plants revealed a missense single-nucleotide polymorphism resulting in a Trp-574-Leu substitution in MR1-A and MR1-P plants, heterozygous in both, but not in the MR2 plants. An additional homozygous substitution, Asp-376-Glu, was identified in the MR1-A plants. Addition of malathion or piperonyl butoxide did not alter the efficacy of mesosulfuron on MR2 plants. In addition, the presence of 2,4-D had no effect on the response of mesosulfuron on the MR2 and Sus. These results suggest an altered target site is the mechanism of resistance to ALS inhibitors in MR1-A and MR1-P plants, whereas a non–target site based resistance apparatus is present in the MR2 plants.

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Multiple-Herbicide Resistance in a 2,4-D–Resistant Waterhemp (Amaranthus tuberculatus) Population from Nebraska

Weed Science ◽

10.1017/wsc.2017.39 ◽

2017 ◽

Vol 65 (6) ◽

pp. 743-754 ◽

Cited By ~ 7

Author(s):

Roberto J. Crespo ◽

Ana B. Wingeyer ◽

Greg R. Kruger ◽

Chance W. Riggins ◽

Patrick J. Tranel ◽

...

Keyword(s):

D1 Protein ◽

Acetolactate Synthase ◽

Mechanisms Of Action ◽

Target Site ◽

Site Mutation ◽

Auxin Receptor ◽

Application Rates ◽

Chlorimuron Ethyl ◽

Als Inhibitors ◽

Susceptible Populations

A 2,4-D-resistant tall waterhemp population (FS) from Nebraska was evaluated for resistance to other TIR1 auxin receptor herbicides and to herbicides having alternative mechanisms of action using greenhouse bioassays and genetic markers. Atrazine, imazethapyr, lactofen, mesotrione, glufosinate, and glyphosate were applied in a single-dose bioassay, and tissue was collected from marked plants for genetic analysis. The FS population was not injured by atrazine or by imazethapyr. Approximately 50% of the plants survived lactofen and were actively growing 28 d after treatment. The population was susceptible to mesotrione, glufosinate, and glyphosate. Ametryn, chlorimuron-ethyl, 2,4-D, aminocyclopyraclor, aminopyralid, and picloram were applied in dose–response studies. The FS population was sensitive to ametryn, and the Ser-264-Gly substitution in the D1 protein was not detected, suggesting the lack of response to atrazine is not due to a target-site mutation. The FS population exhibited less than 50% injury to chlorimuron-ethyl at application rates 20 times the labeled use rate. The Ser-653-Asn acetolactate synthase (ALS) substitution, which confers resistance to imidazolinone herbicides, was present in the FS population. However, this does not explain the lack of response to the sulfonylurea herbicide, chlorimuron-ethyl. Sequencing of a portion of thePPX2Lgene did not show the ΔG210 mutation that confers resistance to protoporphyrinogen oxidase–inhibiting herbicides, suggesting that other factors were responsible for waterhemp survival after lactofen application. The FS population was confirmed to be at least 30-fold resistant to 2,4-D relative to the susceptible populations. In addition, it was at least 3-fold less sensitive to aminopyralid and picloram, two other TIR1 auxin receptor herbicides, than the 2,4-D-susceptible populations were. These data indicated that the FS population contains both target and non–target site mechanisms conferring resistance to herbicides spanning at least three mechanisms of action: TIR1 auxin receptors, ALS inhibitors, and photosystem II inhibitors.

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Acetolactate Synthase (ALS) Target-Site Mutations in ALS Inhibitor-Resistant Russian Thistle (Salsola tragus)

Weed Science ◽

10.1614/ws-d-09-00083.1 ◽

2010 ◽

Vol 58 (3) ◽

pp. 244-251 ◽

Cited By ~ 26

Author(s):

Suzanne I. Warwick ◽

Connie A. Sauder ◽

Hugh J. Beckie

Keyword(s):

Molecular Basis ◽

Genome Structure ◽

Acetolactate Synthase ◽

Molecular Techniques ◽

Target Site ◽

Weed Species ◽

Single Nucleotide ◽

Herbicide Resistant ◽

Inhibitor Resistance ◽

Als Inhibitor

ALS inhibitor-resistant biotypes are the fastest growing class of herbicide-resistant (HR) weeds. A Canadian ALS inhibitor-resistant biotype of Russian thistle was first reported in 1989. The molecular basis for ALS-inhibitor resistance is unknown for Canadian populations of this polyploid weed species, and was determined in this study for one Alberta and two Saskatchewan HR Russian thistle populations. HR plants survived spray application of the ALS-inhibitor mixture thifensulfuron : tribenuron in the greenhouse. All three HR Russian thistle populations were heterogeneous and contained both HR and herbicide-susceptible (HS) individuals. The molecular basis for resistance was determined by sequencing theALSgene and/or conducting a TaqMan genotyping assay for single nucleotide polymorphism (SNP) for the Trp574Leu mutation. Two target-site mutations were observed: Trp574Leu in all three biotypes (554 individuals) and Pro197Gln in one biotype (one individual), suggesting multiple-founding events for Russian thistle HR populations in western Canada. Segregation patterns among F1 and F2 progeny arrays of HR lines sprayed under greenhouse conditions varied; some segregated (i.e., had HR and HS progeny), whereas other lines were exclusively HR. In contrast, no segregation of molecular types, i.e., Trp574, Trp/Leu574and Leu574, as would be expected with heterozygosity at a single locus Trp/Leu574, was observed. Such lack of segregation is consistent with the polyploid genome structure of Russian thistle and the presence of two copies of theALSgene. The presence of more than oneALSgene confounded the ability of the molecular techniques to accurately identify “true” heterozygotes in this study.

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Nature, Occurrence, and Cost of Herbicide-Resistant Wild Oat (Avena fatua) in Small-Grain Production Areas

Weed Technology ◽

10.1017/s0890037x00046297 ◽

1999 ◽

Vol 13 (3) ◽

pp. 612-625 ◽

Cited By ~ 46

Author(s):

Hugh J. Beckie ◽

A. Gordon Thomas ◽

Anne Légère ◽

David J. Kelner ◽

Rene C. van Acker ◽

...

Keyword(s):

Great Plains ◽

Cropping Systems ◽

Acetolactate Synthase ◽

Avena Fatua ◽

Northern Great Plains ◽

Wild Oat ◽

Herbicide Resistant ◽

Multiple Group ◽

Production Areas ◽

Group 1

Surveys were conducted across the northern Great Plains of Canada in 1996 and 1997 to determine the nature and occurrence of herbicide-resistant (HR) biotypes of wild oat (Avena fatua). The surveys indicated that resistance to acetyl-CoA carboxylase (ACCase) inhibitors (Group 1) occurred most frequently relative to other herbicide groups. Group 1-HR wild oat occurred in over one-half of fields surveyed in each of the three prairie provinces. Of particular concern was the relatively high incidence of multiple-group resistance in wild oat in Saskatchewan and Manitoba. In Saskatchewan, 18% of Group 1-HR populations were also resistant to acetolactate synthase inhibitors (imidazolinones), even though these herbicides were not frequently used. In Manitoba, 27% of fields surveyed had wild oat resistant to herbicides from more than one group. Four populations were resistant to all herbicides registered for use in wheat (Triticum aestivum). Depending on the nature of resistance in wild oat, alternative herbicides available for their control may substantially increase costs to the grower. The cost to growers of managing HR wild oat in Saskatchewan and Manitoba using alternative herbicides is estimated at over $4 million annually. For some HR biotypes, alternative herbicides either are not available or all have the same site of action, which restricts crop or herbicide rotation options and threatens the future sustainability of small-grain annual cropping systems where these infestations occur.

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Target site as the main mechanism of resistance to imazamox in a Euphorbia heterophylla biotype

Scientific Reports ◽

10.1038/s41598-019-51682-z ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 9

Author(s):

Antonia M. Rojano-Delgado ◽

João M. Portugal ◽

Candelario Palma-Bautista ◽

Ricardo Alcántara-de la Cruz ◽

Joel Torra ◽

...

Keyword(s):

Enzyme Activity ◽

Root Exudation ◽

Acetolactate Synthase ◽

Target Site ◽

Southern Brazil ◽

Fresh Weight ◽

Weed Species ◽

Site Mutation ◽

Principal Mechanism ◽

Continuous Use

Abstract Euphorbia heterophylla is a weed species that invades extensive crop areas in subtropical regions of Brazil. This species was previously controlled by imazamox, but the continuous use of this herbicide has selected for resistant biotypes. Two biotypes of E. heterophylla from southern Brazil, one resistant (R) and one susceptible (S) to imazamox, were compared. The resistance of the R biotype was confirmed by dose-response assays since it required 1250.2 g ai ha−1 to reduce the fresh weight by 50% versus 7.4 g ai ha−1 for the S biotype. The acetolactate synthase (ALS) enzyme activity was studied using ALS-inhibiting herbicides from five different chemical families. The R biotype required the highest concentrations to reduce this enzyme activity by 50%. A Ser653Asn mutation was found in the ALS gene of the R biotype. The experiments carried out showed that imazamox absorption and metabolism were not involved in resistance. However, greater 14C-imazamox root exudation was found in the R biotype (~70% of the total absorbed imazamox). Target site mutation in the ALS gene is the principal mechanism that explains the imazamox resistance of the R biotype, but root exudation seems to also contribute to the resistance of this biotype.

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