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1.
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2.
Summary A biotype of Conyza albida resistant to imazapyr was discovered on a farm in the province of Seville, Spain, on land that had been continuously treated with this herbicide. This is the first reported occurrence of target site resistance to acetolactate synthase (ALS)-inhibiting herbicides in C. albida . In order to characterize this resistant biotype, dose–response experiments, absorption and translocation assays, metabolism studies, ALS activity assays and control with alternative herbicides were performed. Dose–response experiments revealed a marked difference between resistant (R) and susceptible (S) biotypes with a resistance factor [ED50(R)/ED50(S)] of 300. Cross-resistance existed with amidosulfuron, imazethapyr and nicosulfuron. Control of both biotypes using alternative herbicides was good using chlorsulfuron, triasulfuron, diuron, simazine, glyphosate and glufosinate. The rest of the herbicides tested did not provide good control for either biotype. There were no differences in absorption and translocation between the two biotypes, the maximum absorption reached about 15%, and most of the radioactivity taken up remained in the treated leaf. The metabolism pattern was similar and revealed that both biotypes may form polar metabolites with similar retention time (Rf). The effect of several ALS inhibitors on ALS (target site) activity measured in leaf extracts from both biotypes was investigated. Only with imazapyr and imazethapyr did the R biotype show a higher level of resistance than the S biotype [I50 (R)/I50(S) value of 4.0 and 3.7 respectively]. These data suggest that the resistance to imazapyr found in the R biotype of C. albida results primarily from an altered target site.  相似文献   

3.
Glyphosate‐resistant Palmer amaranth from Georgia (GA), USA, possesses multiple copies of the gene that encodes 5‐enolpyruvylshikimate‐3‐phosphate synthase (EPSPS), the enzyme target site of this herbicide. The cloned plants of glyphosate‐resistant and glyphosate‐susceptible Palmer amaranth biotypes from Mississippi (MS), USA, and GA were evaluated for glyphosate injury (digital imaging) in leaf disc bioassays. Four groups (three resistant groups: two from MS [G and R] and one from GA [C7]; one susceptible group from GA [C3]) were chosen for cloning to facilitate long‐term studies. After exposure to glyphosate (1.0 mmol L–1, 144 h), the level of injury (mean value) was low in the resistant groups, while a higher level of injury was found in the susceptible group. However, the individual injury values within all groups varied widely. The mean EPSPS gene copy number of these groups was G ≥ R > C7 >>> C3. However, a higher copy number did not always convey increased resistance in these bioassays. When the copy number was high (>20), 81.5% of the bioassayed plants exhibited little or no injury and only ～20% were significantly injured, while 50% of the plants with a low copy number (<20) remained healthy. Overall, no strong statistical correlation of the copy number versus injury occurred in these cloned plants and no statistical relationship of resistance and copy number with the sex of the MS plants was observed. The results suggest that although an elevated copy number of the EPSPS gene can instill resistance, other mechanisms might contribute to the overall glyphosate resistance of Palmer amaranth in these plants.  相似文献   

4.
Glyphosate is one of the most commonly used broad‐spectrum herbicides over the last 40 years. Due to the widespread adoption of glyphosate‐resistant (GR) crop technology, especially corn, cotton and soybean, several weed species have evolved resistance to this herbicide. Research was conducted to confirm and characterize the magnitude and mechanism of glyphosate resistance in two GR common ragweed ( A mbrosia artemisiifolia L.) biotypes from Mississippi, USA. A glyphosate‐susceptible (GS) biotype was included for comparison. The effective glyphosate dose to reduce the growth of the treated plants by 50% for the GR1, GR2 and GS biotypes was 0.58, 0.46 and 0.11 kg ae ha?1, respectively, indicating that the level of resistance was five and fourfold that of the GS biotype for GR1 and GR2, respectively. Studies using 14 C‐glyphosate have not indicated any difference in its absorption between the biotypes, but the GR1 and GR2 biotypes translocated more 14 C‐glyphosate, compared to the GS biotype. This difference in translocation within resistant biotypes is unique. There was no amino acid substitution at codon 106 that was detected by the 5‐enolpyruvylshikimate‐3‐phosphate synthase gene sequence analysis of the resistant and susceptible biotypes. Therefore, the mechanism of resistance to glyphosate in common ragweed biotypes from Mississippi is not related to a target site mutation or reduced absorption and/or translocation of glyphosate.  相似文献   

5.
In Shizuoka Prefecture, Japan, glyphosate‐resistant Lolium multiflorum is a serious problem on the levees of rice paddies and in wheat fields. The mechanism of resistance of this biotype was analyzed. Based on LD50, the resistant population was 2.8–5.0 times more resistant to glyphosate than the susceptible population. The 5‐enolpyruvyl‐shikimate‐3‐phosphate synthase (EPSPS) gene sequence of the resistant biotype did not show a non‐synonymous substitution at Pro106, and amplification of the gene was not observed in the resistant biotype. The metabolism and translocation of glyphosate were examined 4 days after application through the direct detection of glyphosate and its metabolite aminomethylphosphonic acid (AMPA) using liquid chromatograph‐tandem mass spectrometer (LC‐MS/MS). AMPA was not detected in either biotype in glyphosate‐treated leaves or the other plant parts. The respective absorption rates of the susceptible and resistant biotypes were 37.90 ± 3.63% and 41.09 ± 3.36%, respectively, which were not significantly different. The resistant biotype retained more glyphosate in a glyphosate‐treated leaf (91.36 ± 1.56% of absorbed glyphosate) and less in the untreated parts of shoots (5.90 ± 1.17%) and roots (2.76 ± 0.44%) compared with the susceptible biotype, 79.58 ± 3.73%, 15.77 ± 3.06% and 4.65 ± 0.89%, respectively. The results indicate that the resistance mechanism is neither the acquisition of a metabolic system nor limiting the absorption of glyphosate but limited translocation of the herbicide in the resistant biotype of L. multiflorum in Shizuoka Prefecture.  相似文献   

6.
Recent reports of weed‐control failures after the use of glyphosate led to suspicion about the selection of resistant biotypes of Conyza at locations in west and north Paraná, Brazil. Plants were collected, identified as Conyza sumatrensis and subsequently evaluated for possible resistance to glyphosate in four stages of weed development. The experiments were carried out in a greenhouse by combining biotypes, stages of development and a range of glyphosate doses. All the suspected biotypes were collected from locations in Cascavel, Toledo, Assis Chateaubriand, Tupãssi and Campo Mourão with a history of glyphosate use in burndown and in glyphosate‐resistant soybean for at least the four previous years and were compared to a susceptible biotype (São Jorge do Ivaí) with no previous history of herbicide use. The doses of glyphosate ranged from 0 to 5760 g ae ha?1. The biotypes were considered as resistant if two combined criteria were present (resistance factor > 1 and the rate required to achieve 80% control is >720 g ha?1). The results provided evidence that there is a marked difference in the level of control of older plants and also confirmed the presence of some resistant biotypes. For applications at the first stage of development, two biotypes that were resistant to glyphosate were identified (Cascavel‐1 and Tupãssi‐6). For applications in the second stage of development, beyond the biotypes that were found in the first stage, three other biotypes were considered as resistant: Toledo‐5, Assis Chateaubriand‐7 and Floresta‐10. However, for applications at the third and fourth stages, all the biotypes were considered as resistant.  相似文献   

7.
Two Alisma plantago‐aquatica biotypes resistant to bensulfuron‐methyl were detected in rice paddy fields in Portugal’s Mondego (biotype T) and Tagus and Sorraia (biotype Q) River valleys. The fields had been treated with bensulfuron‐methyl‐based herbicide mixtures for 4–6 years. In order to characterize the resistant (R) biotypes, dose–response experiments, absorption and translocation assays, metabolism studies and acetolactate synthase (ALS) activity assays were performed. There were marked differences between R and susceptible (S) biotypes, with a resistance index (ED50R/S) of 500 and 6.25 for biotypes Q and T respectively. Cross‐resistance to azimsulfuron, cinosulfuron and ethoxysulfuron, but not to metsulfuron‐methyl, imazethapyr, bentazone, propanil and MCPA was demonstrated. No differences in the absorption and translocation of 14C‐bensulfuron‐methyl were found between the biotypes studied. Maximum absorption attained 1.12, 2.02 and 2.56 nmol g−1 dry weight after 96 h incubation with herbicide, for S, Q and T biotypes respectively. Most of the radioactivity taken up by the roots was translocated to shoots. Bensulfuron‐methyl metabolism in shoots was similar in all biotypes. The R biotypes displayed a higher level of ALS activity than the S biotype, both in the presence and absence of herbicide and the resistance indices (IC50R/S) were 20 197 and 10 for biotypes Q and T respectively. These data confirm for the first time that resistance to bensulfuron‐methyl in A. plantago‐aquatica is target‐site‐based. In practice, to control target site R biotypes, it would be preferable to use mixtures of ALS inhibitors with herbicides with other modes of action.  相似文献   

8.
牛筋草是一年生禾本科恶性杂草, 在我国黄淮海流域及长江以南地区的农田危害严重。草甘膦是一种优良的非选择性除草剂, 随着生物育种产业化的推进, 草甘膦会逐步在玉米、大豆等作物田登记应用。育种基地抗草甘膦杂草的产生是其快速传播的潜在因素。为明确三亚一育种基地牛筋草种群对草甘膦的敏感性, 本研究利用生物测定、分子生物学等方法检测了待测种群的抗性水平, 并分析了可能的分子机制。结果发现, 草甘膦对牛筋草种群的生长抑制中量为2 053.0 g/hm2(有效成分用量), 抗性指数(RI)为5.0; 靶标基因EPSPS的保守区域无突变, 但相对表达量是敏感种群的47.4倍; 抗性植株中EPSPS蛋白的浓度是敏感植株的17.1倍。以上结果表明, 该牛筋草种群对草甘膦产生了中等水平抗性, 靶标基因过量表达是其抗性机制之一。  相似文献   

9.
A biotype of Aster squamatus (Sprengel) Hieronymus with suspected resistance to the ALS-inhibiting herbicide imazapyr was detected in a chicken farm in the province of Seville, Spain, which had been treated once a year with imazapyr for 10 years. Resistance to imazapyr in this biotype was studied using dose-response experiments, absorption and translocation assays, metabolism studies and ALS activity assays. The rate of imazapyr required to inhibit A squamatus growth by 50% (ED50) was 15 times higher for the R (resistant) than for the S (susceptible) biotype. Cross-resistance existed for the ALS-inhibitors imazamox, imazethapyr, amidosulfuron, nicosulfuron, rimsulfuron, triasulfuron and tribenuron, but not for bensulfuron. Control of A squamatus using alternative herbicides was poor with clopyralid, intermediate with quinclorac, amitrole and MCPA, and excellent with 2,4-D, glufosinate and glyphosate. Absorption of [14C]imazapyr increased over time for both the R and S biotypes, and translocation from the treated leaf to shoots and roots was similar in both biotypes, with most of the radioactivity remaining in the treated leaf. No metabolites of imazapyr were detected in either biotype. Sensitivity of the ALS enzyme (target site) to imazapyr was lower for the R biotype (I50(R) = 4.28 x I50(S)). The mechanism of imazapyr resistance in this R biotype appears to be an altered ALS conferring decreased sensitivity to imazapyr at the whole-plant level.  相似文献   

10.
Field resistance of Echinochloa spp. to propanil has been previously reported in Costa Rica, Colombia and Arkansas (USA). In this study, the mechanism of resistance was investigated in three resistant (R) and three susceptible (S) biotypes. The shoot fresh weight reduction in pot-grown plants from a post-emergence spray of propanil at 2.44 kg a.i. ha−1 on biotypes R/S from Costa Rica, Colombia and Arkansas was 35/98%, 25/79% and 20/82% respectively. In vitro chlorophyll fluorescence data from leaf tissue incubated in propanil showed that photosynthesis was inhibited in all biotypes, indicating that the propanil-binding site and enzyme were not altered. After transfer to herbicide-free solution, photosynthesis recovered only in resistant biotypes, indicating that the mechanism of resistance was caused by enhanced metabolism of the herbicide. Simultaneous treatment with fenitrothion, an aryl acylamidase inhibitor, prevented the recovery of photosynthesis in leaf tissue in two resistant biotypes. In contrast, the cytochrome P450 mono-oxygenase inhibitor, 1-aminobenzotriazole, did not prevent recovery from propanil in leaf tissue. Application of 14C-propanil to the second leaf of intact Echinochloa plants showed that c . 90% of the radioactivity remained in the treated leaf for up to 72 h after application. No major differences in translocation between R and S biotype plants were found. TLC analysis of tissue extracts from the treated leaves showed substantially less radioactivity associated with propanil, present after 72 h in rice or in the three R biotypes, compared with S biotypes.  相似文献   

11.
BACKGROUND: In a large cropping area of northern Argentina, Sorghum halepense (Johnsongrass) has evolved towards glyphosate resistance. This study aimed to determine the molecular and biochemical basis conferring glyphosate resistance in this species. Experiments were conducted to assess target EPSPS gene sequences and 14C‐glyphosate leaf absorption and translocation to meristematic tissues. RESULTS: Individuals of all resistant (R) accessions exhibited significantly less glyphosate translocation to root (11% versus 29%) and stem (9% versus 26%) meristems when compared with susceptible (S) plants. A notably higher proportion of the applied glyphosate remained in the treated leaves of R plants (63%) than in the treated leaves of S plants (27%). In addition, individuals of S. halepense accession R2 consistently showed lower glyphosate absorption rates in both adaxial (10–20%) and abaxial (20–25%) leaf surfaces compared with S plants. No glyphosate resistance endowing mutations in the EPSPS gene at Pro‐101–106 residues were found in any of the evaluated R accessions. CONCLUSION: The results of the present investigation indicate that reduced glyphosate translocation to meristems is the primary mechanism endowing glyphosate resistance in S. halepense from cropping fields in Argentina. To a lesser extent, reduced glyphosate leaf uptake has also been shown to be involved in glyphosate‐resistant S. halepense . Copyright © 2011 Society of Chemical Industry  相似文献   

12.
We have selected an upland cotton (Gossypium hirsutum L.) cell line (R1098) that is highly tolerant to glyphosate. This cell line was developed by in vitro selection with gradually increasing glyphosate concentrations, and its mechanisms conferring glyphosate tolerance were studied. Based on a whole-plant dose–response bioassay, R1098 plants were tolerant to glyphosate at a concentration of 1500 g ae ha−1 glyphosate (1.5× the recommended field rate) whereas the control plants (Coker 312) were unable to survive at 150 g ae ha−1 glyphosate. Coker 312 accumulated 13.1 times more shikimate in leaves at 5 days after glyphosate treatment (1500 g ae ha−1) than that of R1098. Two distinct cDNAs for 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), EPSPS-1 and EPSPS-2, were isolated from R1098. Both cDNAs were 97.7% identical within the common protein-coding region and the predicted sequences of the mature proteins were greater than 83% identical with EPSPS proteins from other known higher plants. In comparison to the glyphosate-susceptible cotton Coker 312, sequence analysis of the EPSPS-1 gene indicated that R1098 has an alanine insertion at nucleotide position 1216 resulting in frameshift. It leads to two copy functional EPSPS genes in R1098. There was no difference between R1098 and Coker 312 in EPSPS mRNA levels before glyphosate treatment. However, its treatment caused a 2–4 times increase in the basal EPSPS mRNA level in R1098.  相似文献   

13.
Summary Two Sonchus asper (spiny annual sow-thistle) biotypes, suspected of being resistant to the sulfonylurea herbicide metsulfuron-methyl, were collected in 1996 from two barley ( Hordeum vulgare ) fields in central Alberta, Canada. Both fields had received at least six applications of acetolactate synthase (ALS)-inhibiting herbicide(s). The responses of the two resistant (R) biotypes and two susceptible (S) biotypes to several sulfonylurea herbicides, and to herbicides and herbicide mixtures with other mechanisms of action, were compared. Both R biotypes were highly resistant to all sulfonylurea herbicides, but their control with other herbicides and mixtures was effective and comparable to that of the S biotypes. ALS extracted from an R biotype was about 440 times more resistant to metsulfuron-methyl than that of an S biotype, indicating that resistance was conferred by an ALS enzyme that was less sensitive to inhibition by the herbicide. Competitiveness and seed production of S. asper varied among biotypes, but the differences were probably the result of ecotype differences rather than resistance or susceptibility to sulfonylurea herbicides. This is the first reported occurrence of target site-based S. asper resistance to ALS-inhibiting herbicides.  相似文献   

14.
The mechanism of resistance to diclofop-methyl in three Italian populations of Lolium spp. (two resistant and one susceptible) was investigated. The major proportion of R-1 (Tuscania 1997) and R-2 (Roma 1994) plants (approximately 80%) survived after herbicide treatment by emitting new tillers from the crown. Both resistant (R-1 and R-2) and susceptible (Vetralla 1994) Lolium spp. populations were target-site sensitive. No difference in diclofop-methyl absorption by shoots of resistant and susceptible biotypes was observed. At the dose corresponding to 1× the recommended field rate, a relatively higher metabolism was found in R-2 biotype. In contrast, at the doses 2× and 10× the field rate no difference in herbicide metabolism between susceptible and resistant biotypes was observed. At all the three herbicide doses (1×, 2×, and 10× the field rate) 48 h after the treatment (HAT), the total amount of metabolites produced by wheat was more than three times higher than that produced by resistant and susceptible ryegrass biotypes. At the doses 1× and 2× the field rate, the herbicide translocation was different in the susceptible biotypes compared to resistant biotypes. The total amount of the radiolabel found 48 HAT in culm and root was approximately twice in susceptible biotype than in resistant biotypes. Susceptible and resistant ryegrass biotypes differed in the capability of their roots to acidify the external medium. Susceptible biotype acidified the external solution at approximately 6 times the rates of the resistant biotypes. In the present study, the mechanism responsible for resistance in the investigated resistant biotypes was not univocally identified. Indirect evidence supports the possible involvement of herbicide sequestration or immobilization.  相似文献   

15.
BACKGROUND: Trifluralin‐resistant biotypes of water foxtail (Alopecurus aequalis) have been identified in wheat fields from northern Kyushu, Japan. Water foxtail is a winter‐annual grassy weed, causing substantial crop losses. This study reports on mutation in α‐tubulin (TUA) genes from water foxtail, the site of action of trifluralin. RESULTS: Two trifluralin‐sensitive (S) Chikugo and Ukiha biotypes and four trifluralin‐resistant (R) Asakura‐1, Asakura‐2, Tamana and Tosu biotypes of water foxtail were used for herbicide resistance analysis. R biotypes showed 5.7–30.7‐fold trifluralin resistance compared with the S biotypes. No differences in the uptake and translocation of 14C‐trifluralin were observed between Chikugo (S) biotype and Asakura‐1 (R) biotype. Most of the 14C detected in the plant material was in the root tissue, and no substantial increases were noted in shoot tissues. Comparative TUA sequence analysis revealed two independent single amino acid changes: change of Val into Phe at position 202 in TUA1 and change of Leu into Met at position 125 in TUA3 in Asakura‐1 biotype. In the Tamana (R) biotype, two amino acid changes of Leu to Phe at position 136 and Val to Phe at position 202 were observed in the predicted amino acid sequence of TUA1, compared with Chikugo (S) biotype. CONCLUSION: The results provide preliminary molecular explanation for the resistance of water foxtail to trifluralin, a phenomenon that has arisen as a result of repeated exposure to this class of herbicide. This is the first report of α‐tubulin mutation in water foxtail and for any Alopecurus species reported in the literature. Copyright © 2011 Society of Chemical Industry  相似文献   

16.
Response to paraquat was investigated in two Hordeum glaucum Steud. (wall barley) biotypes grown at warm (30^C) and cool (15^C) temperatures. Paraquat-resistant (R) plants were nearly seven-fold more tolerant when grown at 15^C than when grown at 3CPC. In contrast, there was a tendency for susceptible (S) plants to be more tolerant when grown at the higher temperature. The difference in response between the two biotypes grown at 30^ and 15^C increased from 3- to >40-fold. Forty-eight hours after foliar application, 62% less radiolabelled paraquat had translocated basipetally in the R compared with the S biotype. In addition, 26% more herbicide was retained within the treated zone of R compared with S plants. Thus, paraquat movement was restricted in the R biotype. It has been postulated that reduced mobility of the herbicide in the R plants is due to enhanced apoplasmic binding. In this study, paraquat binding to the cell walls and its release into the external solution was investigated in roots of R and S biotypes of H. glaucum grown under warm or cool conditions. No significant differences between the two biotypes were measured at either growth temperature. We propose that the mechanism of resistance to paraquat may involve a temperature-dependent alteration in symplasmic transport of the herbicide.  相似文献   

17.
Uptake and metabolism of propanil were measured in both susceptible (S) and resistant (R) biotypes of Jungle-rice, Echinochloa colona (L.) link at different growth stages. Results showed that there was no significant difference in uptake between S and R biotypes of E. colona at any given growth stage, but that uptake was significantly reduced at older plant growth stages in all biotypes studied. Metabolism of propanil was more rapid in R biotypes than in S biotypes at all growth stages studied. Specific and total aryl acylamidase activity, responsible for the first stage of propanil metabolism, was higher in R biotypes than in S at all growth stages, but declined to about 50% of the maximum at older growth stages, confirming the importance of this enzyme in conferring resistance to this herbicide. The area of necrosis that developed around a single drop of propanil deposited on the adaxial leaf surface was used to assess the degree of propanil resistance; it was found that resistance increased at older E. colona growth stages in contrast to the rate of propanil metabolism and amidase activity. Treatment of leaves with the amidase inhibitors, carbaryl or piperophos, simultaneously with propanil, caused a decrease in resistance at growth stages where amidase activity was greatest. This treatment was less effective at older growth stages. These results show that, in E. colona, propanil metabolism is important for conferring resistance in younger plants (four-six-leaf stage). It is suggested that restricted uptake confers resistance in older plants.  相似文献   

18.
Resistance to glyphosate from altered herbicide translocation patterns   总被引：3，自引：0，他引：3  
Glyphosate-resistant weeds have evolved as a result of the intensive use of glyphosate for weed control. An alteration in the way glyphosate is translocated within the plant has been identified as a mechanism of glyphosate resistance in populations of Lolium rigidum Gaud., L. multiflorum Lam. and Conyza canadensis (L.) Cronq. In these resistant plants, glyphosate becomes concentrated in the leaves rather than being translocating throughout the plant. This type of resistance is inherited as a single dominant or semi-dominant allele. Resistance due to reduced translocation appears to be a common mechanism of resistance in L. rigidum and C. canadensis, probably because it provides a greater level of resistance than other mechanisms. This type of glyphosate resistance also appears to reduce the fitness of plants that carry it. This may influence how glyphosate resistance can be managed.  相似文献   

19.
抗草甘膦杂草及其抗性机制研究进展   总被引：11，自引：1，他引：10  
介绍了迄今为止全球发现的13种抗草甘膦杂草的发生、发展,并从草甘膦的吸收、输导和分布,5-烯醇丙酮莽草酸-3-磷酸合成酶(EPSPS)的活性以及抗药性遗传等方面对其抗性机制进行了讨论,指出了中国在未来出现抗草甘膦杂草的潜在风险性,并提出了延缓杂草对草甘膦抗性发生的策略。  相似文献   

20.
BACKGROUND: Glyphosate‐resistant (GR) weed species are now found with increasing frequency and threaten the critically important GR weed management system. RESULTS: The reported 31P NMR experiments on glyphosate‐sensitive (S) and glyphosate‐resistant (R) horseweed, Conyza canadensis (L.) Cronq., show significantly more accumulation of glyphosate within the R biotype vacuole. CONCLUSIONS: Selective sequestration of glyphosate into the vacuole confers the observed horseweed resistance to glyphosate. This observation represents the first clear evidence for the glyphosate resistance mechanism in C. canadensis. Copyright © 2010 Society of Chemical Industry  相似文献   

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