Properties of acetolactate synthase from sulfonylurea-resistant Scirpus juncoides Roxb. var. ohwianus T. Koyama

Properties of acetolactate synthase (EC 4.1.3.18; ALS) from sulfonylurea-resistant (SUR) Scirpus juncoides Roxb. var. ohwianus T. Koyama were studied biochemically and physiologically in comparison with those from sulfonylurea-susceptible weed (SUS). GR₅₀ values for growth inhibition and I₅₀ values for ALS inhibition by imazosulfuron were determined for both SUR and SUS. Imazosulfuron controlled the SUS above 80% at the dosage more than 10 g a.i./ha but did not control the SUR at the even great dosage of 1000 g a.i./ha. The rates required for 50% growth inhibition of the SUR relative to the SUS (R/S ratio) were 271-fold. The I₅₀ value for inhibition of ALS from the SUS was 15 nM, compared to I₅₀ of >3000 nM for inhibition of ALS from the SUR. These results suggest that a resistance may due to an altered ALS that is insensitive to imazosulfuron. The K_m (pyruvate) value of ALS from the SUR was similar to the K_m for ALS from the SUS, suggesting that a mutation resulting in resistance does not change the affinity of the enzyme for pyruvate. The specific activity of the SUR ALS was similar to that of the SUS ALS, which indicates that resistance is not an over-expression of the enzyme. ALS activity from both biotypes was inhibited by isoleucine, valine, and leucine in this order. However, the SUR ALS was less sensitive to inhibition by valine than the SUS ALS.     

Varied occurrence of diverse sulfonylurea‐resistant biotypes of Schoenoplectus juncoides [Roxb.] Palla in Japan,as classified by an acetolactate synthase gene mutation

Suspected sulfonylurea (SU)‐resistant Schoenoplectus juncoides plants were collected from rice paddy fields at 24 sites in Japan in order to discover the occurrence pattern of target‐site substitutions on a nationwide scale and at a local field scale. A genetic analysis of the two acetolactate synthase (ALS) genes, ALS1 and ALS2, of the collected plants confirmed that a single‐nucleotide mutation at the Pro₁₉₇, Asp₃₇₆ or Trp₅₇₄ site of either ALS1 or ALS2 existed in each suspected SU‐resistant plant. On a nationwide scale, it was shown that the ALS1 mutations and the ALS2 mutations occurred at a similar frequency, that the P197S and the P197L substitutions were found most frequently among all the substitutions, and that the W574L substitutions (known as global resistance to any ALS‐inhibiting herbicide) were found at a relatively low frequency but in a geographically wide range. In the local field‐scale survey, which was conducted at two sites in Hyogo Prefecture, it was shown that the substitutions were less diverse, compared to on a nationwide scale, probably because the investigation involved a limited number of local fields, and that several substitutions and a susceptible biotype were found in single fields suggesting that a number of collections is required in order to understand the local SU‐resistant status of S. juncoides. In addition, this study reported new findings, that of the P197R, P197T and D376E substitutions in S. juncoides. This set of diverse substitutions in a weed species can be used for further research purposes.     

Characterization of acetolactate synthase from sulfonylurea herbicide‐resistant Schoenoplectus juncoides

Ten accessions of sulfonylurea‐resistant Schoenoplectus juncoides were collected from paddy fields in Japan. In order to characterize acetolactate synthase from sulfonylurea‐resistant S. juncoides, acetolactate synthase amino acid substitutions, whole‐plant growth inhibition and acetolactate synthase enzyme inhibition were examined. Schoenoplectus juncoides has two acetolactate synthase genes (ALS1 and ALS2). The sulfonylurea‐resistant accessions harbored amino acid substitutions at Pro197 or Trp574 in either ALS1 or ALS2 (the amino acid number is standardized to the Arabidopsis thaliana sequence). The whole plants of all the sulfonylurea‐resistant accessions showed resistance to imazosulfuron. The resistance level depended on the altered amino acid residues in acetolactate synthase. The acetolactate synthase enzyme that was partially purified from all the sulfonylurea‐resistant accessions was less sensitive to imazosulfuron, compared to the susceptible accession, suggesting that the resistance is related to the altered acetolactate synthase enzyme. In addition, the concentration–response inhibition of acetolactate synthase activity by imazosulfuron in the sulfonylurea‐resistant accessions was remarkably different with the presence of an amino acid substitution in either ALS1 or ALS2. Furthermore, the concentration–response inhibition of acetolactate synthase activity in the sulfonylurea‐resistant accessions with a P197S, P197T or W574L mutation showed a double‐sigmoid curve. The regression analysis of enzyme inhibition suggested that the abundance ratio of ALS1 to ALS2 enzymes was approximately 70:30%, with a range of ±15%. Taken together, these results suggest that the resistance of sulfonylurea‐resistant accessions of S. juncoides is related to altered acetolactate synthase in either ALS1 or ALS2, although the abundance of the altered acetolactate synthase in the plants is different among the sulfonylurea‐resistant accessions.     

Resistance levels of sulfonylurea‐resistant Schoenoplectus juncoides (Roxb.) Palla with various Pro197 mutations in acetolactate synthase to imazosulfuron,bensulfuron‐methyl,metsulfuron‐methyl and imazaquin‐ammonium

An investigation, using herbicidal pot tests in a greenhouse condition, was conducted to determine the whole‐plant dose–response relationships to several acetolactate synthase (ALS)‐inhibiting herbicides of sulfonylurea (SU)‐resistant Schoenoplectus juncoides with various Pro₁₉₇ mutations in ALS that was collected from Japanese rice paddy fields. All the tested SU‐resistant accessions with a Pro₁₉₇ mutation were highly resistant to two commonly used SU herbicides (imazosulfuron and bensulfuron‐methyl), but were much less resistant to another SU herbicide, metsulfuron‐methyl, and were substantially not resistant to imazaquin‐ammonium. These cross‐resistance patterns have been known previously in fragments of S. juncoides and other weed species and were comprehensively confirmed in this study with a whole set of Pro₁₉₇ mutations. The analyses of resistance levels, based on ED₉₀ values, newly showed that different accessions with a common amino acid substitution in ALS1 showed similar responses to these herbicides (confirmed with four amino acid substitutions), that the rankings of resistance levels that were conferred by various Pro₁₉₇ mutations in ALS1 differed among the SU herbicides and that the resistance levels of the ALS2‐mutated accessions were higher than, lower than or similar to those of the corresponding ALS1‐mutated accessions, depending on the compared pair, but the deviation patterns were generally similar among the SU herbicides in each compared pair. The final finding might suggest that the abundance of ALS2 is not as stable as that of ALS1. In addition, as a result of these new findings, together with expected further research, a suggested possibility is that substituting amino acids at Pro₁₉₇ generally could be estimated by plotting each accession's ED₉₀ values of imazosulfuron and bensulfuron‐methyl in a two‐dimensional graph.     

Biology and mechanisms of sulfonylurea resistance in Schoenoplectiella juncoides,a noxious sedge in the rice paddy fields of Japan

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.     

Evaluation of novel sulfonylurea derivatives with a fused heterocyclic moiety as paddy herbicides that control sulfonylurea‐resistant weeds

Herbicidal activity and acetolactate synthase (ALS) inhibition of sulfonylurea derivatives with a fused heterocyclic moiety bonded to a sulfonyl group were investigated. Some compounds that had an imidazo[1,2‐b]pyridazine moiety substituted at the 2‐position by chlorine or methyl controlled sulfonylurea‐resistant (SU‐R) weeds and showed inhibitory activity to ALS prepared from SU‐R Schoenoplectus juncoides shoot. There was a correlation between in vitro and whole‐plant herbicidal activity of the compounds mentioned above against SU‐R Schoenoplectus juncoides. Among them 1‐(2‐chloro‐6‐propylimidazo[1,2‐b]pyridazin‐3‐ylsulfonyl)‐3‐(4,6‐dimethoxypyrimidin‐2‐yl)urea, propyrisulfuron, was selected for further evaluation. Propyrisulfuron effectively controlled paddy weeds at doses of 70 and 140 g a.i. ha^?1 with good rice selectivity in a field trial.     

Transformation a mutant Monochoria vaginalis acetolactate synthase (ALS) gene renders Arabidopsis thaliana resistant to ALS inhibitors

Acetolactate synthase (ALS) genes from Monochoria vaginalis resistant (R) and susceptible (S) biotypes against ALS inhibitors found in Korea revealed a single amino acid substitution of Proline (CCT), at 169th position based on the M. vaginalis ALS sequence numbering, to serine (TCT) in conserved domain A of the gene (equal to the proline 197 in Arabidopsis thaliana ALS gene sequence). A. thaliana plants transformed with the single mutated (Pro₁₆₉ to Ser) M. vaginalis ALS gene (including transit signal peptide) showed cross-resistance patterns to ALS-inhibiting herbicides, like as sulfonylurea-herbicide bensulfuron methyl (R/S factor of 9.5), imidazolinone-herbicide imazapyr (R/S factor of 5.1), and triazolopyrimidine-herbicide flumetsulam (R/S factor of 17.6) when measuring hypocotyls’ length of A. thaliana. The ALS activity from the transgenic A. thaliana plants confirmed the cross-resistance pattern to these herbicides like as R/S factor of 8.3 to bensulfuron methyl, 2.3 to imazapyr, and 13.2 to flumetsulam.     

Effects of triazophos on biochemical substances of transgenic Bt rice and its nontarget pest Nilaparvata lugens Stål under elevated CO2

The brown planthopper (BPH), Nilaparvata lugens Stål, is a serious rice pest throughout Asia. Recent outbreaks of N. lugens populations were mainly associated with the overuse of pesticides and resistance to insecticides. Warmer global temperatures that are associated with anthropogenic climate change are likely to have marked ecological effects on terrestrial ecosystems. However, the effects of elevated CO₂ concentrations on the biochemical, physiological and nutrient quality of transgenic Bt rice that has been treated with pesticides and on the control efficacy of the pesticides are not understood. The present study investigated changes in soluble sugar content, free amino acid levels, oxalic acid levels, flavonoids levels, and triazophos residues in transgenic Bt rice (TT51) and the control efficacy of triazophos for N. lugens following triazophos foliar spray under conditions of elevated CO₂ (eCO₂). Our findings showed that the soluble sugar content of TT51 treated with triazophos under eCO₂ was significantly higher than that under ambient CO₂ (aCO₂) and also higher than that of the non-transgenic parent (MH63) under aCO₂. However, the results for free amino acid levels were the opposite of those for soluble sugar levels. The oxalic acid and flavonoid contents of rice plants significantly decreased with increases in triazophos concentration, CO₂ concentration, and days after treatment (DAT). The oxalic acid and flavonoid contents of TT51 treated with triazophos under eCO₂ were significantly lower than those under aCO₂ and also lower than those of MH63 under aCO₂. The residue concentration of triazophos varied with CO₂ concentration, rice variety, and DAT. The residues in TT51 treated with 80 ppm of trizaopos under eCO₂ were significantly lower than those under aCO₂ and those in MH63 under aCO₂. The survival rate of nymphs N. lugens in TT51 under eCO₂ was significantly higher than that under aCO₂ and that in MH63 under aCO₂ at 1 DAT or 15 DAT after the release of 2nd instars nymphs. These findings indicated that (1) for TT51, triazophos reduced the resistance of rice plants to N. lugens with an elevated CO₂ concentration, as N. lugens consumed more phloem sap on TT51 plants; (2) triazophos dissipation in TT51 under eCO₂ was significantly faster than that under aCO₂ and that in MH63 under aCO₂; (3) the control efficacy of triazophos for N. lugens significantly decreased under eCO₂. The present findings provide important information for integrated pest management among transgenic varieties.     

Rapid diagnosis of sulfonylurea‐resistant Schoenoplectus juncoides [Roxb.] Palla using polymerase chain reaction–restriction fragment length polymorphism and isogene‐specific direct sequencing

Rapid diagnostic methods to detect known mutations in acetolactate synthase (ALS) genes that confer sulfonylurea (SU) resistance to Schoenoplectus juncoides were developed in this study. By using 11 SU‐resistant accessions (nine accessions with a Pro₁₉₇ substitution in ALS1 or ALS2, one accession with an Asp₃₇₆Glu substitution in ALS2 and one accession with a Trp₅₇₄Leu substitution in ALS2), polymerase chain reaction–restriction fragment length polymorphism (PCR–RFLP) analysis for DNA fragments that were amplified simultaneously from genomic ALS1 and ALS2 and PCR–RFLP analysis for DNA fragments that were amplified from either of the genomic ALS1 or ALS2 were carried out. In each of the two PCR–RFLP analyses, a common PCR product was digested separately with the restriction enzymes, BspLI, MboI and MunI, in order to detect Pro₁₉₇ substitutions, an Asp₃₇₆Glu substitution and a Trp₅₇₄Leu substitution, respectively. In each of the lanes where the detection of SU‐resistant substitutions was aimed, a specific band to suggest the existence of the said substitutions was observed in theoretically assumable ways. Separately, a direct sequencing method also was established, which was able to selectively sequence ALS1 or ALS2 from common templates containing both ALS1 and ALS2 by the isogene‐selective primers that were designed to anneal either of the ALS genes. It is expected that these methods could be used for the genetic analysis of SU‐resistant S. juncoides by providing rapid and accurate diagnosis.     

茶皂素、生石灰等防治稻田福寿螺的效果评估

福寿螺已成为我国南方局部稻区严重危害水稻的有害生物,为解决常用的化学杀螺剂污染环境和农产品的问题,分别在室内和大田环境下研究了生石灰、碳酸氢铵、茶麸和茶皂素4种替代物质防治福寿螺的效果。茶皂素、茶麸和生石灰对稻田福寿螺有很好的防治作用。在室内试验中40 mg/L和50 mg/L茶皂素处理在48 h 即达到了100%的防效;在大田试验中茶皂素6.0 g/m²的处理在第4天、1.5 g/m²的处理在第16天均达到了100%的防治效果,且速效性和持效性也显著优于其它物质。30 g/m²和45 g/m²的茶麸处理以及45 g/m²的生石灰处理在大田试验第16天的防治效果也在80%以上。这3种物质对稻田稗草还有很好的抑制作用。碳酸氢铵对福寿螺防治效果较差,且能促进稻田稗草的发生。研究结果表明,茶皂素、茶麸和生石灰可作为化学杀螺剂的替代物质在大田中推广应用。     

不同稻田生态系统中稻纵卷叶螟、稻飞虱及其天敌密度的差异

研究了施用化学农药防治害虫的常规管理稻田和充分发挥天敌自然控害作用为主要防治害虫措施的稻田生态系统内稻纵卷叶螟、稻飞虱及其天敌的发生消长动态,以明确不同稻田生态系统对稻区内主要害虫及其天敌的影响.结果显示,生态调控区稻田内稻纵卷叶螟和稻飞虱最大高峰期虫量仅分别为常规管理区的0.51倍和0.63倍;生态调控区稻周植被上稻纵卷叶螟和稻飞虱发生数量几乎为0,而常规管理区最大高峰期虫量分别达到 23.61头/10网和82.03头/10网.生态调控措施还可以显著增加天敌数量,生态调控区稻田内最大高峰期天敌数量为常规管理区的3.72倍,其稻周杂草上最大高峰期天敌数量为常规管理区的5倍以上;同时,天敌与稻纵卷叶螟和稻飞虱发生高峰期吻合度远高于常规管理区.说明生态调控措施能充分发挥稻田及周边非稻田生境的保益控害功能.     

山东省部分市县麦田杂草麦家公Lithospermum arvense对苯磺隆的抗药性

采用温室盆栽法和培养皿法测定了山东省部分市县冬小麦田杂草麦家公Lithospermum arvense L.对苯磺隆的抗药性水平,以及其抗药性生物型乙酰乳酸合成酶(ALS)对苯磺隆的敏感性。温室盆栽结果显示,供试杂草对苯磺隆产生了不同程度的抗药性,其中胶州麦家公生物型抗性水平最高,抗性倍数为12.8倍;培养皿法测定结果也显示胶州麦家公生物型抗性水平最高,但抗性倍数为3.89倍。交互抗性测定结果表明,胶州抗性麦家公生物型对其他ALS抑制剂噻吩磺隆和苄嘧磺隆已产生不同程度的交互抗性,其中对噻吩磺隆的抗性倍数达到3.11倍。离体条件下,与敏感生物型ALS活力的抑制中浓度(IC50)相比较,胶州抗性麦家公生物型的IC50值是敏感麦家公的 2.65倍。表明ALS敏感性降低可能是山东部分市县麦家公对苯磺隆产生抗药性的重要原因之一。     

Differential morphological and physiological responses of two oilseed Brassica species to a new herbicide ZJ0273 used in rapeseed fields

Weeds are considered as a major threat to the production of oilseed Brassica crops. The use of herbicides that are safe for crops and effective in controlling weeds is crucial for the agronomists and farmers. Propyl 4-(2-(4,6-dimethoxypyrimidin-2-yloxy)benzylamino)benzoate (ZJ0273), a derivative of 2-pyrimidinyloxy-N-aryl benzoate, is a new herbicide used in the rapeseed field. To evaluate the tolerance of Brassica species against this new herbicide, two cultivars of rapeseed Brassica napus cv. ZS 758 and Brassica rapa cv. Xiaoyoucai were tested by a foliar spray of ZJ0273 at the rate of 100, 500 and 1000 mg/L and a currently used ALS (acetolactate synthase)-inhibiting herbicide bispyribac-sodium (BS) at the rate of 100 mg/L. The results showed that both the cultivars of Brassica were less affected by ZJ0273 as compared to BS. Increasing level of ZJ0273 herbicide from 100 to 1000 mg/L increased the stress for the plants of both the cultivars as indicated by enhanced accumulation of malondialdehyde content. The activities of ALS and antioxidant enzymes (superoxide dismutase and peroxidase), soluble protein and sugar contents, photosynthetic system (SPAD value, photosynthetic rate and chlorophyll fluorescence) as well as the agronomic characters also declined consistently with each successive increase in ZJ0273 concentration. In general, the plants treated with 100 mg/L ZJ0273 recovered from the herbicide stress after 28 days. B. napus showed more tolerance than B. rapa to the new herbicide. Nevertheless, BS application at 100 mg/L did not allow the plants of both the cultivars to recover from the herbicidal stress.     

Molecular basis of diverse responses to acetolactate synthase-inhibiting herbicides in sulfonylurea-resistant biotypes of Schoenoplectus juncoides

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.     

Spontaneous ultraweak photon emission from rice (Oryza sativa L.) and paddy weeds treated with a sulfonylurea herbicide

All living organisms spontaneously generate ultraweak photon emissions, which originate from biochemical reactions in cells. Current research uses the ultraweak photon emissions from organisms as a novel tool to investigate the physiological states of plants. In this study, we found ultraweak photon emissions from leaf segments of rice and several paddy weed species treated with a sulfonylurea herbicide. There is a definite difference in photon emissions among plant species, and rice (Oryza sativa), barnyardgrass (Echinochloa crus-galli) and Cyperus serotinus showed extremely strong enhancement of photon emissions. Photon emissions from these three species treated with sulfonylurea herbicide were suppressed when the leaf segments were treated with the cytochrome P450 monooxygenase (P450) inhibitors, piperonyl butoxide and malathion. These results suggest that P450 inhibitors affect the ultraweak photon emissions from plants.     

N-3型无人直升机施药方式对稻飞虱和稻纵卷叶螟防治效果的影响

为了阐明喷洒药械N-3型无人直升机(N-3 UAV)对稻飞虱和稻纵卷叶螟的防治效果及应用前景,进行了飞机不同作业高度和不同喷洒浓度的田间药效试验.结果表明,在水稻分蘖后期,飞机每公顷喷洒48％毒死蜱·锐劲特EC 432 g(有效成分,下同),施药后3、5、10d对稻飞虱的防治效果为96.93％、92.21％、88.12％,对稻纵卷叶螟的保叶效果为63.29％、54.00％、58.33％,均优于传统担架式喷雾机喷洒防治效果.在水稻孕穗期,无人机在3m和5m的作业高度下,每公顷喷洒25％吡蚜酮SC 75 g,施药后10 d对稻飞虱的防治效果与每公顷喷洒60 g和52.5 g时防治效果无显著差异;每公顷施用40％二嗪·辛硫磷EC 480 g和384 g防治稻纵卷叶螟,施药后10d,3m作业高度下的杀虫效果均达90.90％,优于5m和7m的杀虫效果.     

Toxicity and selective mechanism of imazamox by weedy rice and imidazolinone-resistant rice in China

Weedy rice (Oryza spp.) is a notorious weed in direct-seeding paddy fields. Because it has anatomical and physiological traits similar to those of cultivated rice, no selective herbicide is effective in controlling weedy rice growing among conventional rice cultivars. Imidazolinone (IMI)-resistant rice lines JD372 and JJ818 have been planted with imazamox to control weedy rice in Jiangsu and Shanghai, China. Whole-plant dose–response analysis showed that imazamox exhibited high efficacy against three populations of weedy rice. The ED₉₀ of weedy rice populations FN-5, GY-8, and HY-3 were 46.87, 61.43, and 52.17 g a.i. ha⁻¹, respectively, close to the recommended field dose (50 g a.i. ha⁻¹) of imazamox. Conversely, the ED₁₀ values of JD372 and JJ818 were slightly lower than 50 g a.i. ha⁻¹. These findings indicate that imazamox can control weedy rice production in JD372 and JJ818 fields. The acetolactate synthase (ALS) sensitivity of JD372 in vitro was 1714.89-fold lower to imazamox than was that of FN-5. ALS gene sequencing revealed a Ser653Asn point mutation—a common mutation that confers resistance to IMI herbicides in JD372. In addition, higher ALS expression levels in JD372 were found at 24 and 72 h after imazamox treatment. ALS overexpression might partially compensate for the ALS activity of JD372 that was suppressed by imazamox.     

新疆地区棉铃虫自然种群对Bt棉的抗性频率监测

为监测新疆棉区棉铃虫Helicoverpa armigera(Hübner)田间种群对Bt棉的抗性频率,在2010年和2011年分别采集石河子和喀什地区莎车的棉铃虫单雌系,以Cry1Ac毒蛋白作为人工饲料,用单雌系F1/F2代法进行棉铃虫种群抗性个体检测。2010年筛选了123个石河子的棉铃虫单雌系,2 011年筛选了152个莎车的棉铃虫单雌系。两地的棉铃虫种群均没有筛选到相对平均发育级别≥0.8的抗Bt棉个体,估算出石河子和莎车的棉铃虫种群的抗性频率低于10-3。莎车F2单雌系与其对应的F1单雌系相对平均发育级别有明显差异。研究表明新疆石河子地区田间棉铃虫种群仍保持敏感状态,喀什地区田间棉铃虫种群对Bt棉的耐受性增高。