萘二甲酸酐减轻胺苯磺隆对水稻药害的作用机制

通过在离体和活体条件下萘二甲酸酐（NA）对水稻乙酰乳酸合成酶（ALS）活力的影响,进行NA减轻胺苯磺隆对水稻药害作用机制研究。离体条件下,NA对水稻幼苗ALS的活力影响很小,且未能产奋勇安苯磺隆对ALS活性的抑制作用。活体条件下,NA提高幼苗ALS活力达40％,且抵消胺苯磺隆对ALS活力的抑制作用,说明NA减轻胺苯磺隆对水稻药害的作用机制是NA间接激活靶标酶ALS。     

不同玉米品种对氯吡嘧磺隆的耐药性差异及其机制

为科学评价氯吡嘧磺隆对玉米的安全性,采用室内盆栽法和酶活力测定法探讨不同玉米品种对氯吡嘧磺隆的耐药性差异及其机制。不同玉米品种对氯吡嘧磺隆的耐药性有较大差异,其中甜玉米耐药性最差,IC10仅为94.87g/hm2(有效成分,余同)。花糯1号、鲁单981、五岳97-1等品种表现出中等耐药性,耐药性倍数为1.51～1.97;五岳21、郑单958、强盛16等耐药性较强,耐药性倍数为2.05～2.43。强盛16、鲁单981和甜玉米对氯吡嘧磺隆的耐药性差异显著,但其靶标酶乙酰乳酸合成酶(ALS)在离体条件下对该药剂的敏感性差异不显著;在活体条件下,三者ALS活力均可很快恢复,且耐药性品种恢复能力较强。与甜玉米相比,经氯吡嘧磺隆处理后强盛16的谷胱甘肽-S-转移酶(GSTs)对氯吡嘧磺隆的反应幅度较大和反应时间较短,第72h相对活力就达到4.2的峰值,而甜玉米变化幅度相对较小,第96 h才达到2.6的峰值。研究表明,不同玉米品种对氯吡嘧磺隆耐药性的差异源于GSTs对氯吡嘧磺隆的代谢差异,而与靶标酶ALS对氯吡嘧磺隆的敏感程度无关。     

甲基二磺隆及吡唑解草酯对不同品种小麦ALS酶的影响

采用温室盆栽茎叶喷雾处理,研究了3%甲基二磺隆油悬浮剂以及安全剂吡唑解草酯对不同品种小麦的耐药性及其对靶标酶乙酰乳酸合成酶(ALS)的影响。结果表明,甲基二磺隆对敏18号小麦株高抑制程度明显高于抗6号。离体ALS酶含量和活力测定结果表明,抗6号ALS含量高于敏18号,在200和400 μmol/L的吡唑解草酯溶液中黑暗培养7 d,抗6号小麦ALS比活力比对照分别增加1.29和1.58倍,敏18号比对照分别增加0.25和0.15倍。抗6号小麦品种对甲基二磺隆耐药性较强。小麦自身ALS含量和比活力差异以及安全剂吡唑解草酯对它们的诱导差异可能是小麦品种对甲基二磺隆耐药性不同的原因之一。     

不同小麦品种对双氟磺草胺的耐药性差异及机理

室内采用平皿法和酶活力测定法探讨了不同小麦品种对双氟磺草胺的耐药性差异及其机理。结果表明,不同小麦品种根对双氟磺草胺的耐药性差异较大,其中济宁13对该药剂最为敏感,IC50值仅为0.221 2 μg/mL,烟农15、枣20-28、济南17与之相当(耐药性倍数为1.09~1.99),泰山9818、山农6号和潍麦8号耐药性较强(耐药性倍数为10.33~13.92)。酶活力测定结果表明:虽然耐药型品种潍麦8号和敏感型品种济南17对双氟磺草胺的耐药性差异显著,但其靶标酶乙酰乳酸合成酶(ALS)在离体条件下对该药剂的敏感性却无显著差异;在活体条件下,二者ALS活力均可很快恢复,其中潍麦8号恢复较快。经双氟磺草胺处理后,与济南17相比,潍麦8号的代谢酶谷胱甘肽- S -转移酶(GSTs)相对活力变化幅度较大且反应时间较短,在第2 d即可达到峰值1.460,而济南17在第3 d才达到峰值1.398。研究表明,不同小麦品种对双氟磺草胺的耐药性存在差异 的原因之一可能是由于GSTs对双氟磺草胺的代谢差异,而与靶标酶ALS对药剂的敏感程度无关。     

不同棉花品种对三氟啶磺隆的耐药性差异及机制

为评价三氟啶磺隆对棉花的安全性,采用温室盆栽法测定了22种棉花对三氟啶磺隆的耐药性差异及其机制。结果显示,三氟啶磺隆45 g/hm² （有效成分,余同）处理对不同棉花品种苗期鲜重及株高抑制作用差异显著,其中对鲁棉研40、银兴4、K638、创鲁1、德利农5的鲜重和株高抑制率相对较低,分别为8.60%~13.11%和10.26%~11.84%,而对鲁H498、鲁棉研36、鲁棉研28的鲜重和株高抑制率相对较高,分别为32.21%~38.26%和20.68%~22.66%。乙酰乳酸合成酶（ALS）活性测定表明,鲁棉研40、鲁H498离体ALS对三氟啶磺隆的敏感性无显著差异;在活体条件下,两棉花ALS相对活性先减小,后逐渐恢复,且鲁棉研40恢复能力强。经三氟啶磺隆处理后,鲁棉研40谷胱甘肽-S-转移酶（GSTs）变化幅度较鲁H498大且反应时间短,鲁棉研40在处理后3 d达到最大值1.53,鲁H498在处理后5 d达到最大值1.45。研究表明,不同棉花品种对三氟啶磺隆耐药性的差异源于GSTs对三氟啶磺隆的代谢差异,与靶标酶ALS对三氟啶磺隆的敏感程度无关。     

麦田抗性生物型荠菜对苯磺隆的抗性机制研究

为明确抗性生物型荠菜对苯磺隆的抗性机制,分别测定了苯磺隆对抗性和敏感生物型荠菜体内乙酰乳酸合成酶(ALS)、谷胱甘肽-S-转移酶(GSTs)、超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)的影响。结果表明:离体条件下,抗性生物型荠菜体内ALS对苯磺隆的敏感性明显降低,苯磺隆对荠菜抗性和敏感生物型ALS的抑制中浓度(I50)分别为0.722 8和0.052 1 μmol/L,抗性与敏感生物型I50的比值为13.87;活体条件下,施用苯磺隆后,抗性和敏感生物型荠菜ALS活性均受到一定程度的抑制,但抗性生物型ALS活性受到抑制后能逐渐恢复,而敏感生物型则不能恢复;经苯磺隆处理后,抗性生物型GSTs相对活力明显高于敏感生物型,而抗性和敏感生物型体内POD、SOD和CAT相对活力无明显差异。研究表明,抗性生物型荠菜体内ALS对苯磺隆敏感性降低是其抗药性产生的原因之一,而GSTs对苯磺隆代谢能力的差异也可能与荠菜对苯磺隆的抗性有关。     

不同水稻品种或组合对甲磺隆的耐药性差异研究

选用水稻株高作为测量指标,室内测定了48个水稻品种或组合对甲磺隆的耐药性,结果表明,不同水稻品种或组合对甲磺隆的耐药性存在明显差异,IC50值为0.0194-2.7644mg.L^-1,其中5个品种（约占10％）IL50＞1.0mg.L^-1,27个品种或组合（约占56％）IC50为0.1-1.0mg.L^-1,16个品种（约占33％）IC50＜0.1mg.L^-1。在分析甲磺隆对水稻株高IC50值的基础上,探索性地提出了水稻对甲横隆的耐药性分级标准,与生产实际较为吻合,在实践中具有重要指导意义。     

天然芸苔素内酯缓解胺苯磺隆对后茬水稻药害的作用机理初探

通过测定天然芸苔素内酯对水稻幼苗谷胱甘肽(GSH)含量、谷胱甘肽-S-转移酶(GST)活性以及在离体和活体条件下对水稻幼苗乙酰乳酸合成酶(ALS)活力的影响,研究天然芸苔素内酯减轻胺苯磺隆对水稻药害的作用机理。结果表明,其作用机理与水稻幼苗GSH含量、GST活性变化没有太大相关性,可能与其能间接激活水稻幼苗ALS活力有较大相关。     

麦田不同杂草对苯磺隆敏感性差异的分子机制

为了探讨麦田常见杂草对苯磺隆敏感性差异的分子机制,测定了苯磺隆对4种杂草活性及对杂草体内靶标酶(ALS)和代谢酶(GSTs)的影响差异。结果表明,泽漆对苯磺隆的敏感性最低,IC50为123.16gai/hm2;猪殃殃和荠菜次之,分别为8.47、1.07gai/hm2;播娘蒿最敏感,为0.29gai/hm2。离体条件下,苯磺隆对播娘蒿、泽漆ALS的IC50值分别为6.40、54.90mgai/L。活体条件下,苯磺隆处理后,播娘蒿体内ALS活力低于对照,第9天降为对照的31.20%,而敏感性低的泽漆处理后1～2天ALS活力虽略有下降,但第3天明显提高,第4天达到峰值,为对照的2.90倍,此后逐渐恢复至对照水平。4种杂草本身所含GSTs活性存在较大差异,泽漆GSTs活性最高。经苯磺隆处理后,泽漆与猪殃殃GSTs活性明显提高,第4天时达到峰值,相对活性分别为1.23和1.25,并持续在较高水平;而荠菜、播娘蒿GSTs活性虽分别在第3、5天达到峰值,但多数时间相对活性低于1。结果表明,麦田不同杂草体内ALS的敏感性差异和GSTs的代谢差异是对苯磺隆敏感性不同的两个重要原因。     

不同小麦品种对苯磺隆耐药性差异及其机理

室内用砂培法测定11种小麦品种对苯磺隆的相对敏感性,其敏感性有较大差异.碧玛4号、维麦8号对苯磺隆有很强的耐药性,IC50可分别达到502.6和409.3aiμg/kg,济1 3号为156.9aiμg/kg,鲁麦22号、黄县大粒对苯磺隆较为敏感,IC50低于45.0 aiμg/kg.以上5种小麦离体ALS对苯磺隆的敏感性没有明显差异,敏感品种黄县大粒IC50为154.2nmol/L,甚至较维麦8号149.3nmol/L略高.ALS活体试验表明,小麦可以很快恢复苯磺隆对ALS活性的抑制,且耐药型品种恢复能力较强,碧玛4号、维麦8号ALS恢复活性只需1.5天,敏感品种需3天.碧玛4号、维麦8号除草剂解毒酶系GSTs相对于敏感品种对苯磺隆有较大的反应幅度和较短的反应时间,第2天就分别达到1.46、1.42的峰值,而济13号、鲁麦22号、黄县大粒变化幅度较小,第3天才达到峰值,活性分别为1.39、1.33和1.32.研究表明,小麦各品种对苯磺隆的耐药能力产生差异的主要原因之一是小麦GSTs对苯磺隆的代谢所致,而与小麦ALS对苯磺隆的敏感程度无关.     

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.     

Tolerance to acetolactate synthase and acetyl-coenzyme A carboxylase inhibiting herbicides in Vulpia bromoides is conferred by two co-existing resistance mechanisms

Vulpia bromoides is a grass species naturally tolerant to acetolactate synthase (ALS) and acetyl-coenzyme A carboxylase (ACCase) inhibiting herbicides. The mechanism of tolerance to ALS herbicides was determined as cytochrome P450-monooxygenase mediated metabolic detoxification. The ALS enzyme extract partially purified from V. bromoides shoot tissue was found to be as sensitive as that of herbicide susceptible Lolium rigidum to ALS-inhibiting sulfonylurea (SU), triazolopyrimidine (TP), and imidazolinone (IM) herbicides. Furthermore, phytotoxicity of the wheat-selective SU herbicide chlorsulfuron was significantly enhanced in vivo in the presence of the known P450 inhibitor malathion. In contract, the biochemical basis of tolerance to ACCase inhibiting herbicides was established as an insensitive ACCase. In vitro ACCase inhibition assays showed that, compared to a herbicide susceptible L. rigidum, the V. bromoides ACCase was moderately (4.5- to 9.5-fold) insensitive to the aryloxyphenoxypropionate (APP) herbicides diclofop, fluazifop, and haloxyfop and highly insensitive (20- to >71-fold) to the cyclohexanedione (CHD) herbicides sethoxydim and tralkoxydim. No differential absorption or de-esterification of fluazifop-P-butyl was observed between the two species at 48 h after herbicide application, and furthermore V. bromoides did not detoxify fluazifop acid as rapidly as susceptible L. rigidum. It is concluded that two co-existing resistance mechanisms, i.e., an enhanced metabolism of ALS herbicides and an insensitive target ACCase, endow natural tolerance to ALS and ACCase inhibiting herbicides in V. bromoides.     

Sulfonylurea resistance in Stellaria media [L.] Vill.

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.     

Mechanism of resistance to bensulfuron-methyl in Alisma plantago-aquatica biotypes from Portuguese rice paddy fields

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.     

三种ALS抑制剂对四类植物ALS的抑制差异

用乙酰乳酸合成酶(ALS)活性测定方法研究了双草醚、KIH-15127、苄嘧磺隆3种ALS抑制剂对水稻、稗草和油菜ALS活性的抑制差异性。体外测定结果表明，不同植物ALS对双草醚和KIH-15127的敏感性差异较大，粳稻、稗草和油菜ALS的敏感性强于籼稻，而这些植物ALS对苄嘧磺隆的敏感性差异很小。体内结果显示，双草醚和KIH-15127对稗草和油菜ALS的抑制作用较强，对粳稻ALS的抑制作用可以恢复；苄嘧磺隆对油菜ALS的抑制作用也较强，但对稗草、水稻ALS基本无抑制作用；3种ALS抑制剂对籼稻ALS抑制作用均较弱。结果表明，不同植物对ALS抑制剂的敏感性存在差异。     

Isolation and antifungal activity of lignans from Myristica fragrans against various plant pathogenic fungi

BACKGROUND: In a search for plant extracts with potent in vivo antifungal activity against various plant diseases, we found that treatment with a methanol extract of Myristica fragrans Houttyn (nutmeg) seeds reduced the development of various plant diseases. The objectives of the present study were to isolate and determine antifungal substances from My. fragrans and to evaluate their antifungal activities. RESULTS: Three antifungal lignans were isolated from the methanol extract of My. fragrans seeds and identified as erythro-austrobailignan-6 (EA6), meso-dihydroguaiaretic acid (MDA) and nectandrin-B (NB). In vitro antimicrobial activity of the three lignans varied according to compound and target species. Alternaria alternata, Colletotrichum coccodes, C. gloeosporioides, Magnaporthe grisea, Agrobacterium tumefaciens, Acidovorax konjaci and Burkholderia glumae were relatively sensitive to the three lignans. In vivo, all three compounds effectively suppressed the development of rice blast and wheat leaf rust. In addition, EA6 and NB were highly active against the development of barley powdery mildew and tomato late blight, respectively. Both MDA and NB also moderately inhibited the development of rice sheath blight. CONCLUSION: This is the first study to demonstrate the in vitro and in vivo antifungal activities of the three lignans from My. fragrans against plant pathogenic fungi.