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1.
BACKGROUND: Hordeum populations are becoming increasingly difficult to control in cropping fields. Two herbicide‐resistant H. leporinum populations were identified during a random crop survey after herbicides were applied. The study aimed to determine the herbicide resistance profile of these H. leporinum biotypes to a range of herbicides used for their control. RESULTS: Based on dose–response studies, one H. leporinum population was very highly resistant to sulfosulfuron and sulfometuron (both sulfonylurea herbicides) and also displayed low‐level resistance to imazamox (an imidazolinone herbicide). Reduced sensitivity of the ALS enzyme was identified with in vitro activity assays. Gene sequence analysis revealed a proline‐to‐threonine substitution at amino acid position 197 of ALS, which is likely to be the molecular basis for resistance in this population. Herbicide screening also revealed a different H. leporinum population with resistance to the bipyridyl herbicide paraquat. CONCLUSION: This study established the first cases of (1) sulfonylurea‐to‐imidazolinone cross‐resistance and (2) field‐evolved paraquat resistance in a Hordeum species in Western Australia. Copyright © 2012 Society of Chemical Industry 相似文献
2.
BACKGROUND: In the important grass weed Lolium rigidum (Gaud.), resistance to ALS‐inhibiting herbicides has evolved widely in Australia. The authors have previously characterised the biochemical basis of ALS herbicide resistance in a number of L. rigidum biotypes and established that resistance can be due to a resistant ALS and/or enhanced herbicide metabolism. The purpose of this study was to identify specific resistance‐endowing ALS gene mutation(s) in four resistant populations and to develop PCR‐based molecular markers. RESULTS: Six resistance‐conferring ALS mutations were identified: Pro‐197‐Ala, Pro‐197‐Arg, Pro‐197‐Gln, Pro‐197‐Leu, Pro‐197‐Ser and Trp‐574‐Leu. All six mutations were found in one population (WLR1). Each Pro‐197 mutation conferred resistance to the sulfonylurea (SU) herbicide sulfometuron, whereas the Trp‐574‐Leu mutation conferred resistance to both sulfometuron and the imidazolinone (IMS) herbicide imazapyr. A derived cleaved amplified polymorphic sequences (dCAPS) marker was developed for detecting resistance mutations at Pro‐197. Furthermore, cleaved amplified polymorphic sequences (CAPS) markers were developed for detecting each of the six mutant resistant alleles. Using these markers, the authors revealed diverse ALS‐resistant alleles and genotypes in these populations and related them directly to phenotypic resistance to ALS‐inhibiting herbicides. CONCLUSION: This study established the existence of a diversity of ALS gene mutations endowing resistance in L. rigidum populations: 1–6 different mutations were found within single populations. At field herbicide rates, resistance profiles were determined more by the specific mutation than by whether plants were homo‐ or heterozygous for the mutation. Copyright © 2008 Society of Chemical Industry 相似文献
3.
Physiological and molecular basis for ALS inhibitor resistance in Bromus tectorum biotypes 总被引：2，自引：0，他引：2
Primisulfuron‐resistant (AR and MR) and ‐susceptible (AS and MS) Bromus tectorum biotypes were collected from a Poa pratensis field at Athena, Oregon, and in research plots at Madras, Oregon. Studies were conducted to characterize the resistance of the B. tectorum biotypes. Whole plant bioassay and acetolactate synthase (ALS) enzyme assay revealed that the AR biotype was highly resistant to the sulfonylurea (SU) herbicides, primisulfuron and sulfosulfuron and to a sulfonylaminocarbonyltriazolinone (SCT) herbicide, propoxycarbazone‐sodium. However, the AR biotype was not resistant to imazamox, an imidazolinone (IMI) herbicide. Results of the whole plant bioassay studies showed that the MR biotype was moderately resistant to all ALS inhibitors tested. However, there were no differences in ALS sensitivities between the MR and MS biotypes. The nucleotide and amino acid sequence analysis of the als gene demonstrated a single‐point mutation from C to T, conferring the exchange of the amino acid proline to serine at position 197 in the AR biotype. However, this mutation was not found in the MR biotype. Results of this research indicate that: the resistance of the AR biotype to SU and SCT herbicides is based on an altered target site due to a single‐point mutation; resistance in the MR biotype is not due to a target site mutation. 相似文献
4.
BACKGROUND: Wild radish, a problem weed worldwide, is a severe dicotyledonous weed in crops. In Australia, sustained reliance on ALS‐inhibiting herbicides to control this species has led to the evolution of many resistant populations endowed by any of several ALS mutations. The molecular basis of ALS‐inhibiting herbicide resistance in a novel resistant population was studied. RESULTS: ALS gene sequencing revealed a previously unreported substitution of Tyr for Ala at amino acid position 122 in resistant individuals of a wild radish population (WARR30). A purified subpopulation individually homozygous for the Ala‐122‐Tyr mutation was generated and characterised in terms of its response to the different chemical classes of ALS‐inhibiting herbicides. Whole‐plant dose‐response studies showed that the purified subpopulation was highly resistant to chlorsulfuron, metosulam and imazamox, with LD50 or GR50 R/S ratio of > 1024, > 512 and > 137 respectively. The resistance to imazypyr was found to be relatively moderate (but still substantial), with LD50 and GR50 R/S ratios of > 16 and > 7.8 respectively. In vitro ALS activity assays showed that Ala‐122‐Tyr ALS was highly resistant to all tested ALS‐inhibiting herbicides. CONCLUSION: The molecular basis of ALS‐inhibiting herbicide resistance in wild radish population WARR30 was identified to be due to an Ala‐122‐Tyr mutation in the ALS gene. This is the first report of an amino acid substitution at Ala‐122 in the plant ALS that confers high‐level and broad‐spectrum resistance to ALS‐inhibiting herbicides, a remarkable contrast to the known mutation Ala‐122‐Thr endowing resistance to imidazolinone herbicide. Copyright © 2012 Society of Chemical Industry 相似文献
5.
BACKGROUND: Bromus rigidus is a common weed species that has increased in cropping fields owing to limited control options. During a random field survey in Western Australia, six B. rigidus populations that had survived in‐crop weed control programmes were collected. The study aimed to determine the resistance profile of these six populations. RESULTS: Based on dose–response studies, all six B. rigidus populations had a low‐level resistance to sulfosulfuron and sulfometuron (both sulfonylurea herbicides) while remaining susceptible to herbicides with other modes of action. ALS in vitro activity assays revealed no differences in enzyme sensitivity between susceptible and resistant populations, while the use of malathion (a cytochrome P450 inhibitor) in combination with sulfosulfuron caused the resistant populations to behave like the susceptible population. CONCLUSION: This study established that these six B. rigidus populations have a low‐level resistance to the ALS‐inhibiting sulfonylurea herbicides, but are able to be controlled by other herbicide modes of action. The low‐level, malathion‐reversible resistance, together with a sensitive ALS, strongly suggest that a non‐target‐site enhanced metabolism is the mechanism of resistance. Copyright © 2012 Society of Chemical Industry 相似文献
6.
Acetolactate synthase (ALS) from one susceptible and two chlorsulfuronresistant biotypes of Stellaria media(L.) Vill. was assayed in the presence of eight known ALS inhibitors. As expected, ALS from the chlorsulfuronresistant biotypes (R1 and R2) showed reduced sensitivity to chlorsulfuron and other sulfonylurea herbicides. The patterns of cross-resistance varied, however, indicating that the alteration in ALS that confers chlorsulfuron resistance does not confer the same level of resistance to other sulfonylurea herbicides. The resistant biotypes were highly cross-resistant to sulfometuron-methyl and DPX-A7H81, but less cross-resistant to triasulfuron. Both R1 and R2 were highly cross-resistant to DTPS (N-[2,6-dichlorophenyl]-5,7-dimethyl-1,2,4-iriazolo[1,5a]pyrimidine-2-siilfoiiamide), but only slightly cross-resistant to imazamethahenz, an imidazolinone herbicide. The differences in the patterns of cross-resistance observed presumably reflect differences in the binding affinity of the herbicides for the altered ALS. The data presented suggest, but do not confirm, that R1 and R2 contain the same ALS mutation. 相似文献
7.
Sulfonylurea resistance in Stellaria media [L.] Vill. 总被引：1，自引：1，他引：1
A sulfonylurea resistant biotype of common chickweed (Stellaria media L. Vill.) was found in a field treated with chlorsulfuron or metsulfuron for eight consecutive years. In pot experiments the biotype was resistant to postemergence treatments with the following acetolactate synthase (ALS) inhibitors: chlorsulfuron, metsulfuron, tribenuron, triasulfuron, rimsulfuron, sulfometuron, flumetsulam and imazapyr. The level of resistance to chlorsulfuron and sulfometuron was higher than to the other sulfonylurea herbicides. Whereas the level of cross resistance to the triazolopyrimidine herbicide, flumetsulam was comparable to that of metsulfuron, that of imazapyr was significantly lower. In contrast to imazapyr the biotype was not resistant to imazethapyr, an other imidazolinone herbicide. ALS in vitro assays revealed that resistance was due to an ALS enzyme that was less sensitive to ALS inhibiting herbicides. Herbicides with different modes of action were equally effective on the susceptible and resistant biotypes. 相似文献
8.
A Rashid J C Newman J T O'Donovan† D Robinson‡ D Maurice§ &D Poisson§ & L M Hall¶ 《Weed Research》2003,43(3):214-220
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
9.
Three Australian Sisymbrium orientale and one Brassica tournefortii biotypes are resistant to acetolactate synthase (ALS)-inhibiting herbicides due to their possession of an ALS enzyme with decreased sensitivity to these herbicides. Enzyme kinetic studies revealed no interbiotypic differences within species in Km (pyruvate) (the substrate concentration at which the reaction rate is half maximal) but a greater Vmax (the rate when the enzyme is fully saturated with substrate) for two of the resistant S orientale biotypes over susceptible levels. F1 hybrids from reciprocal crosses between resistant and susceptible biotypes of S orientale showed an intermediate response to chlorsulfuron compared to the parental plants. ALS herbicide resistance in S orientale segregated in a 3:1 (resistant:susceptible) ratio in F2 plants with a single rate of chlorsulfuron, indicating that resistance is inherited as a single, incompletely dominant nuclear gene. Two regions of the ALS structural gene known to vary in ALS-resistant biotypes were amplified and sequenced. Resistant S orientale biotypes NS01 and SS03 contained a single nucleotide substitution in Domain B, predicting a Trp (in susceptible) to Leu (in resistant) amino acid change. Two adjacent nucleotide substitutions (CC T to AT T) predicting a Pro (in susceptible) to Ile (in resistant) change in the primary amino acid sequence were identified in Domain A of resistant S orientale biotype SS01. Likewise, a single nucleotide substitution at the same site in the resistant B tournefortii biotype predicts a Pro (in susceptible) to Ala (in resistant) substitution. No other interbiotypic nucleotide differences predicted amino acid changes in the sequenced regions, suggesting that the amino acid substitutions reported above are responsible for resistance to ALS-inhibiting herbicides in the respective biotypes. © 1999 Society of Chemical Industry 相似文献
10.
近年来长江下游地区稻田耳叶水苋Ammannia arenaria H.B.K.危害十分严重。采用盆栽法首次测定了耳叶水苋对苄嘧磺隆等药剂的抗性水平,同时分析了其抗性和敏感种群间乙酰乳酸合成酶(ALS)基因的DNA序列及其RNA表达差异。结果表明:采自浙江嘉兴(JX110)、江苏苏州(JS039)、浙江宁波(NB0143-05)和安徽广德(AH014)的耳叶水苋生物型对苄嘧磺隆的抗性指数(RI)分别为67.90、17.59、44.63和8.37,对苄嘧磺隆表现出中高水平抗性的生物型对五氟磺草胺、双草醚及咪唑乙烟酸也产生了低水平的抗性。获得了耳叶水苋ALS基因全长核苷酸序列2235 bp,编码667个氨基酸,仅发现NB0143-05等3种抗性生物型ALS酶的氨基酸序列非保守区第93位的亮氨酸被脯氨酸取代。然而,NB0143-05的ALS酶对ALS抑制剂的敏感性大幅度降低(RI 37.04),且在苄嘧磺隆处理后4 d的ALS基因表达量是敏感生物型(HZ001)的1.86倍。这表明,ALS酶对药剂的敏感性降低以及被苄嘧磺隆诱导后ALS基因表达量显著增加,很可能是耳叶水苋生物型NB0143-05对ALS抑制剂产生抗性的原因。 相似文献
11.
为明确水稻田杂草多花水苋Ammannia multiflora对乙酰乳酸合成酶 (ALS) 抑制剂类除草剂苄嘧磺隆的抗性水平和抗性分子机制,采用整株水平测定法,测定了采自江苏省扬州市田间的多花水苋疑似抗性种群 (YZ-R) 对苄嘧磺隆的抗性指数,并分析了YZ-R种群和相对敏感种群 (YZ-S)多花水苋ALS酶对苄嘧磺隆的敏感性差异,同时比较了YZ-R和YZ-S种群ALS基因的核苷酸序列差异。结果表明:YZ-R种群多花水苋对苄嘧磺隆已表现出高水平抗性,其抗性指数 (RI) 为40.6;苄嘧磺隆对YZ-R种群ALS酶活性的抑制中浓度 (I50) 为0.087 μmol/L,对YZ-S种群的I50值为0.0028 μmol/L,其抗性指数为31.1。通过PCR扩增获得了多花水苋ALS基因的部分序列,该序列包含了已报道的8个氨基酸突变位点。ALS基因序列比对分析发现,YZ-R种群多花水苋植株ALS基因第197 位氨基酸由脯氨酸 (CCT) 突变为丝氨酸 (TCT)。研究表明,ALS基因发生脯氨酸 (Pro)-197-丝氨酸 (Ser) 的突变,导致多花水苋ALS酶对苄嘧磺隆的敏感性下降,是多花水苋YZ-R种群对苄嘧磺隆产生高水平抗性的主要原因。 相似文献
12.
Lemma W Mengistu George W Mueller‐Warrant Aaron Liston Reed E Barker 《Pest management science》2000,56(3):209-217
The herbicide‐binding region of the chloroplast psbA gene from a total of 20 biotypes of Poa annua L resistant and susceptible to metribuzin and diuron was selectively amplified using PCR. Sequence analysis of the fragment from six herbicide‐resistant biotypes of P annua exhibited a substitution from valine to isoleucine at position 219 of the D1 protein encoded by the psbA gene. This is the same mutation as reported for Chlamydomonas and Synechococcus through site‐directed mutagenesis and in cell cultures of Chenopodium rubrum L. To our knowledge this is the first report of a higher plant exhibiting resistance in the field to photosystem II inhibitors due to a psbA mutation other than at position 264. The existence of additional biotypes of P annua resistant to diuron or metribuzin but lacking mutation in the herbicide‐binding region indicates that resistance to these herbicides can also be attained by other mechanisms. © 2000 Society of Chemical Industry 相似文献
13.
AKIRA UCHINO SHIGERU OGATA HIROSHI KOHARA SHUICHI YOSHIDA TOSHIHITO YOSHIOKA HIROAKI WATANABE 《Weed Biology and Management》2007,7(2):89-96
Sulfonylurea-resistant biotypes of Schoenoplectus juncoides were collected from Nakafurano, Shiwa, Matsuyama, and Yurihonjyo in Japan. All of the four biotypes showed resistance to bensulfuron-methyl and thifensulfuron-methyl in whole-plant experiments. The growth of the Nakafurano, Shiwa, and Matsuyama biotypes was inhibited by imazaquin-ammonium and bispyribac-sodium, whereas the Yurihonjyo biotype grew normally after treatment with these herbicides. The herbicide concentration required to inhibit the acetolactate synthase (ALS) enzyme by 50% (I50), obtained using in vivo ALS assays, indicated that the four biotypes were > 10-fold more resistant to thifensulfuron-methyl than a susceptible biotype. The Nakafurano, Shiwa, and Matsuyama biotypes exhibited no or little resistance to imazaquin-ammonium, whereas the Yurihonjyo biotype exhibited 6700-fold resistance to the herbicide. The Nakafurano and Shiwa biotypes exhibited no resistance to bispyribac-sodium, but the Matsuyama biotype exhibited 21-fold resistance and the Yurihonjyo biotype exhibited 260-fold resistance to the herbicide. Two S. juncoides ALS genes (ALS1 and ALS2) were isolated and each was found to contain one intron and to encode an ALS protein of 645 amino acids. Sequencing of the ALS genes revealed an amino acid substitution at Pro197 in either encoded protein (ALS1 or ALS2) in the biotypes from Nakafurano (Pro197 → Ser197), Shiwa (Pro197 → His197), and Matsuyama (Pro197 → Leu197). The ALS2 of the biotype from Yurihonjyo was found to contain a Trp574 → Leu574 substitution. The relationships between the responses to ALS-inhibiting herbicides and the amino acid substitutions, which are consistent with previous reports in other plants, indicate that the substitutions at Pro197 and Trp574 are the basis of the resistance to sulfonylureas in these S. juncoides biotypes. 相似文献
14.
杂草对AHAS抑制剂的抗药性分子机理研究进展 总被引：3，自引：1，他引：2
除草剂在田间的重复及不合理使用,导致了杂草抗药性的发生和发展。其中AHAS抑制剂由于靶标单一,抗性发展十分迅速。截至2009年,已有103种杂草对AHAS抑制剂产生了抗药性,占19类化学除草剂总抗药性杂草生物型的近1/3。从AHAS基因突变位点及种类与杂草抗药性水平的关系、AHAS基因突变与AHAS酶活性的关系、AHAS基因拷贝数与杂草抗药性的关系以及AHAS酶与除草剂结合前后的三维结构等方面,综述了杂草对AHAS抑制剂产生抗药性的机理,旨在为AHAS抑制剂抗性研究提供参考。并对自然种群目标基因的等位基因检测技术(ECOTILLING)和衍生型酶切扩增多态性序列(dCAPS)两种通过检测等位基因多态性的手段快速诊断抗药性杂草的新技术进行了介绍,讨论了延缓杂草抗药性发生和发展的策略。 相似文献
15.
16.
Weitang Liu Yaling Bi Lingxu Li Guohui Yuan Long Du Jinxin Wang 《Pesticide biochemistry and physiology》2013
Water chickweed is a widespread and competitive winter annual or biennial weed of wheat in China. One Water chickweed population (HN02) resistant to several acetolactate synthase (ALS) inhibitors was found in Henan province of China. Whole-plant bioassays showed that HN02 was high resistance to tribenuron (292.05-flod). In vitro ALS assays revealed that resistance was due to reduced sensitivity of the ALS enzyme to tribenuron. The I50 value for HN02 was 85.53 times greater respectively than that of susceptible population (SD05). This altered ALS sensitivity in the resistant population was due to a mutation in the ALS gene resulting in a Pro197 to Ser substitution. Cross-resistance experiments indicated that HN02 exhibited various resistance patterns to pyrithiobac-sodium, florasulam and pyroxsulam, without resistance to imazethapyr. This is the first report of tribenuron-resistant Water chickweed in Henan province of China, target-site based resistance was established as being due to an insensitive form of ALS, resulting from a Pro to Ser substitution at amino acid position 197 in the ALS gene. 相似文献
17.
Biology and mechanisms of sulfonylurea resistance in Schoenoplectiella juncoides,a noxious sedge in the rice paddy fields of Japan 
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下载免费PDF全文 Schoenoplectiella juncoides is a noxious sedge weed in rice paddy fields that has evolved resistance to sulfonylurea (SU) herbicides. The molecular basis of resistance is amino acid substitutions at Pro197, Trp574 or Asp376 in the acetolactate synthase (ALS) enzyme, which is the target of SUs. Schoenoplectiella juncoides has two ALS genes and resistant plants have point mutations that cause amino acid substitutions in either encoded protein. Single‐nucleotide substitutions at the codon for Pro197 in the ALS genes can cause six types of amino acid substitutions and all of these substitutions have been found in both ALS genes among Japanese SU‐resistant biotypes. Whole‐plant herbicide responses differ among the amino acid substitution types. Furthermore, analyses of ALS activity in plant extracts show that the extracts’ responses to herbicides differ, depending on which ALS gene is mutated. The activity responses of the ALS extracts to the SU, imazosulfuron, showed double‐sigmoid curves with plateaus of ~30% inhibition for Pro197 substitutions in ALS1 and ~70% for Pro197 substitutions in ALS2. This indicates that ALS1 and ALS2 contribute to the responses with a proportion of 7:3. The double‐sigmoid curves can be reconstructed to show the responses of the resistant and susceptible enzymes separately by regression analysis. The resistance levels of the separate ALS1 or ALS2 mutated enzyme are highly correlated with the whole‐plant responses, with a relationship that the former is the square of the latter. This could provide a quantitative insight into the physiological basis of resistance. 相似文献
18.
The development of acetolactate synthase (ALS) tolerant sugar beet provides new opportunities for weed control in sugar beet cultivation. The system consists of an ALS?inhibiting herbicide (foramsulfuron + thiencarbazone‐methyl) and a herbicide‐tolerant sugar beet variety. Previously, the use of ALS‐inhibitors in sugar beet was limited due to the susceptibility of the crop to active ingredients from this mode of action. The postulated benefits of cultivation of the ALS‐tolerant sugar beet are associated with potential risks. Up to now, with no relevant proportion of herbicide‐tolerant crops in Germany, ALS‐inhibitors are used in many different crops. An additional use in sugar beet cultivation could increase the selection pressure for ALS‐resistant weeds. To evaluate the impact of varying intensity of ALS‐inhibitor use on two weed species (Alopecurus myosuroides and Tripleurospermum perforatum) in a crop rotation, field trials were conducted in Germany in two locations from 2014 to 2017. Weed densities, genetic resistance background and crop yields were annually assessed. The results indicate that it is possible to control ALS‐resistant weeds with an adapted herbicide strategy in a crop rotation including herbicide‐tolerant sugar beet. According to the weed density and species, the herbicide strategy must be extended to graminicide treatment in sugar beet, and a residual herbicide must be used in winter wheat. The spread of resistant biotypes in our experiments could not be attributed to the integration of herbicide‐tolerant cultivars, although the application of ALS‐inhibitors promoted the development of resistant weed populations. Annual use of ALS‐inhibitors resulted in significant high weed densities and caused seriously yield losses. Genetic analysis of surviving weed plants confirmed the selection of ALS‐resistant biotypes. 相似文献
19.
Herbicide resistance in Lolium rigidum is widespread across much of the agricultural land in Australia. As the incidence of herbicide resistance has increased, so has the incidence of multiple herbicide resistance. This reduces the herbicide options available for control of this weed. This study reports on the successful amplification and sequencing of the acetolactate synthase (ALS) gene of L. rigidum using primers designed from sequence information of related taxa. This enables, for the first time, the successful determination of a mutation in the ALS gene of this species that provides resistance to ALS‐inhibiting herbicides. This mutation causes amino acid substitution at Trp574 (numbering standardised to Arabidopsis thaliana) to Leu which had been reported to confer a high level of resistance against all classes of ALS inhibitor herbicides. In addition, multiple resistance to ALS‐inhibiting and acetyl‐coenzyme A carboxylase‐inhibiting herbicides is acquired through the independent accumulation of mutant alleles for the target sites. This may thus explain some of the irregular, mosaic resistance patterns that occur in this predominantly outcrossing species. 相似文献
20.
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