A standardised in vivo and in vitro test method for evaluating tick repellents

The threat of transmission of Lyme borelliosis and tick-borne encephalitis by ixodid ticks has resulted in an increasing number of tick repellents coming onto the market. To allow proper evaluation of the efficacy of different types of compounds and their formulations, there is a need for standardised methods for testing ticks repellents. Ticks show a marked negative geotactic response following contact with a potential host, i.e., they climb up in order to locate attachment and feeding sites, whereas exposing ticks to repellents induces positive geotaxis, i.e., ticks walk downwards or drop off the treated host or substrate. We describe here complementary tests that employ these geotactic responses to evaluate repellents: one in vitro on a warm glass plate and the other on the lower human leg (shin). The compounds tested were DEET, EBAAP, icaridin, capric acid, lauric acid, geraniol, citriodiol, citronella essential oil and lavender essential oil, all non-proprietary ingredients of widely distributed tick repellent formulations.     

Chirality index, molecular overlay and biological activity of diastereoisomeric mosquito repellents

Both 1-methylisopropyl 2-(2-hydroxyethyl)piperidine-1-carboxylate, (Picaridin((R))) and cyclohex-3-enyl 2-methylpiperidin-1-yl ketone (AI3-37220; 220) have two asymmetric centers, and the four diastereoisomers of each compound are known to have differing degrees of mosquito-repellent activity according to quantitative behavioral assays conducted at the United States Department of Agriculture. Computational chemistry was used to identify the structural and configurational basis for repellent activity. Molecular overlay of the optimized geometries of the lowest energy conformers of the diastereoisomers was investigated to elucidate the role of chiral centers in 220 and Picaridin. It was found that the presence of a chiral carbon alpha to the nitrogen with the S configuration in the piperidine ring is essential to the three-dimensional arrangement of the atoms of the pharmacophore for effective repellent activity.     

棉花抗旱品种筛选鉴定及抗旱性综合评价方法

从甘肃敦煌、新疆的棉花栽培品种和国内外引进材料中选出76个遗传来源不同的棉花品种(系)作为参试材料,在年降雨量不足40 mm的甘肃省敦煌市设置了干旱胁迫和正常灌水两个处理,筛选出与棉花抗旱性密切相关的10个农艺性状和产量指标,采用综合抗旱系数(CDC)、综合抗旱指数(CDI)、综合隶属函数值(CDM)、抗旱性综合评价值(D)等四种综合评价方法对76份种质材料进行抗旱性评价。结果显示,四种综合评价方法两两之间的Pearson相关系数都在0.88以上,相关性均达到了极显著水平;再利用四种抗旱评价体系得分值对76个受试棉花品种(系)进行K-means划分聚类,最终将76个品种分为高抗(Ⅰ类,5个品种)、抗(Ⅱ类,9个品种)、中等(Ⅲ类,17个品种)、敏感(Ⅳ类,31个品种)、高敏(Ⅴ类,14个品种)5个抗旱等级。为进一步方便育种家简单准确地评价选育材料的抗旱性,利用筛选出的10个农艺性状指标的抗旱系数作为自变量,四种抗旱性综合评价体系得分值为因变量,采用逐步回归的方式建立了棉花抗旱性预测模型回归方程。     

茶毛虫核型多角体病毒和Bt混剂的配比筛选及药效评价

在室内条件下采用浸叶法测定了茶毛虫核型多角体病毒(Euproctis pseudoconspersa nucleopolyhedrovirus,EpNPV)和苏云金杆菌(Bacillus thuringiensis,Bt)及其不同配比对茶毛虫的毒力,结果表明,EpNPV和Bt 5种比例混用均表现出不同程度的增效作用,共毒系数在177.3~221.7之间。其中以1.0×104PIB/μL EpNPV+2 000IU/μL Bt混用增效最明显,其毒效是Bt单剂的2.54倍。田间小区试验表明,EpNPV-Bt混剂(1.0×104PIB/μL EpNPV+2 000IU/μLBt)对茶毛虫幼虫有优良的防效,显著优于Bt单剂和EpNPV单剂(p0.05)。     

辣椒嫁接抗病砧木筛选及嫁接栽培技术

共选取8个砧木品种,通过生长势观察、抗病性调查、亲和力观测等试验, 筛选出综合性状突出的砧木ZM608,进行了抗性测定,接菌后7、15、30 d的死株率为0、0、2.5%,而本地主栽品种陇椒2号分别为2.5%、21.25%、37.5%。经较大面积嫁接示范推广,辣椒疫病死株率控制在6%以内。     

抑制植物病原细菌的植物筛选

以3种重要的植物病原细菌—辣椒青枯病菌(Ralstonia solanacearum)、柑橘溃疡病菌(Xanthomonas citri)和大白菜软腐病菌(Erwinia carotovorapv.carotovora)为供试菌,对43种植物甲醇提取物进行离体抑菌活性测定。研究结果表明,漆树对辣椒青枯病菌抑菌活性最强,其次是金秀清明茶;抑制柑橘溃疡病菌活性最高的植物有漆树和十大功劳;对大白菜软腐病菌没有筛选到抑菌活性较好的植物;垫状卷柏、七叶一枝花、少花龙葵、水半夏和豆瓣菜粗提物对3种植物病原细菌均无抑制作用。     

Esterase inhibitors as synergists for (+)-trans-chrysanthemate insecticide chemicals

Four synergists are used to evaluate the relative contribution of esterases and oxidases in the metabolism of four pyrethroids, the (+)-trans- and (+)-cis-isomers of resmethrin and tetramethrin, by five insect species and by mice. Three of these compounds are known pyrethroid synergists, S,S,S-tributyl phosphorotrithioate acting as an esterase inhibitor and piperonyl butoxide and O-(2-methylpropyl) O-(2-propynyl) phenylphosphonate acting as oxidase inhibitors. The fourth synergist, 1-naphthyl N-propylcarbamate, is an esterase inhibitor selected by screening 65 candidate esterase and oxidase inhibitors for maximal potency in synergizing the toxicity of trans-resmethrin to milkweed bugs. Naphthyl propylcarbamate synergizes the toxicity of trans-resmethrin and -tetramethrin to milkweed bugs, cockroaches, houseflies, cabbage loopers, and mealworms but not to mice. The persistence of trans-resmethrin in milkweed bugs treated by injection is increased by the esterase inhibitors while that of cis-resmethrin is increased by the oxidase inhibitors. The optimal synergist varies with the species and the pyrethoid, being related to both the nature of the pyrethroid alcohol moiety and the trans- or cis-configuration of the acid moiety. This probably results from species variations in the relative significance of esterases and oxidases in pyrethroid detoxification.     

防治葡萄溃疡病的杀菌剂筛选与评价

采用菌丝生长速率法和孢子萌发法测定了7种杀菌剂对可可毛色二孢CSS-01s的室内生物活性,筛选出3种抑制效果较好的杀菌剂;通过对离体葡萄绿枝条及盆栽葡萄幼苗新梢进行人工接种病原菌,进一步评价杀菌剂的防治效果。结果表明,7种杀菌剂对可可毛色二孢菌丝生长和孢子萌发表现出不同的抑制活性,其中戊唑醇、氯氟醚菌唑、啶酰菌胺和氟啶胺对菌丝生长的抑制作用较强,EC₅₀分别为0.116、0.137、0.109μg/mL和0.119μg/mL;戊唑醇、氯氟醚菌唑、氟啶胺对孢子萌发的抑制作用较强,EC₅₀分别为0.420、0.595μg/mL和1.885μg/mL。CSS-01s接种离体葡萄绿枝条试验中,戊唑醇100、200 mg/L,氯氟醚菌唑100、300 mg/L和氟啶胺100、200 mg/L的防治效果无显著差异,在57.81%～65.31%;CSS-01s接种葡萄幼苗新梢试验中,氟啶胺200 mg/L的防治效果最好,为77.56%,与氟啶胺100 mg/L、氯氟醚菌唑100、300 mg/L和戊唑醇200 mg/L之间无显著差异,但显著高于戊唑醇100...     

密执安棒形杆菌的DNA条形码基因筛选与评价

密执安棒形杆菌是一种重要的植物病原细菌,其包含了能引起不同植物病害的5个亚种。近年来迅速发展起的DNA条形码技术给植物病原细菌快速准确的检测鉴定提供了新思路,本文对棒形杆菌属的4条候选DNA条形码基因进行PCR扩增测序,并从扩增及测序成功率、种内及种间遗传距离、barcoding gap及NJ树等几个方面进行比较,结果表明gyr B基因最适合进行该属内种及亚种的区分,cpn60基因可作为该属分类鉴定的有效补充。     

昆虫病原真菌抗紫外保护剂的筛选和评价

在室内检测了17种紫外保护剂和4种组合对3种昆虫病原真菌即球孢白僵菌Beauveria bassiana、金龟子绿僵菌Metarhizium anisopliae、蜡蚧轮枝孢Verticillium lacani分生孢子的保护作用.结果表明,苯并三唑类2#的紫外保护作用最好,用紫外杀菌灯照射30 min,苯并三唑类2#对3种菌株孢子的保护效率均达90%以上;苯并三唑类3#、苯甲酮类2#、荧光黄钠、刚果红的保护效率可达60%.组合使用紫外保护剂并不能增强保护效果.选用苯并三唑类2#时,适宜的溶剂是花生油加正己烷(1:1,v/v),使用浓度应大于0.75%.用254、312、365 nm波长紫外灯照射40 min内,1%苯并三唑类2#对3种菌株孢子的保护效率可保持90%,照射180 min后,保护效率在56%～77%.     

小麦全蚀病菌拮抗细菌的筛选及生防效果

为筛选小麦全蚀病菌Gaeumannomyces tritici的拮抗细菌,从健康小麦根际土壤中分离和筛选拮抗细菌,采用对峙培养法和室内盆栽试验测定拮抗细菌对小麦全蚀病菌的抑制活性及生防效果,通过形态学特征观察、生理生化特性测定和保守序列分析确定其分类地位。结果表明,从小麦根际土壤中分离并筛选获得2株具有较好拮抗效果的菌株XJ-3和XJ-4,对小麦全蚀病菌菌丝生长的抑制率分别为64.31%和65.25%。基于菌株XJ-3和XJ-4的形态学特征、生理生化特性和gyrB基因系统进化分析结果,将其均鉴定为贝莱斯芽胞杆菌Bacillus velezensis。菌株XJ-3和XJ-4的发酵液中均含有一类具抗真菌活性、耐热性的非蛋白类次生代谢产物;经菌株XJ-3和XJ-4发酵液处理小麦幼苗后,株高较对照分别显著增加了6.48%和13.12%,干重较对照分别增加了1.30%和14.29%,其中菌株XJ-4的促生效果相对较好;对小麦全蚀病的盆栽防效分别达到51.29%和52.46%。表明筛选得到的贝莱斯芽胞杆菌XJ-3和XJ-4可用于小麦全蚀病的生物防治,具有开发为生防制剂的潜力。     

Screening of 170 Peruvian plant species for allelopathic activity by using the Sandwich Method

Peru is one of the 20 botanically extremely diverse countries in the world, with >17 000 flowering plants, of which 30% are endemic. So far, no systematic research has been conducted on the screening of the allelopathic plants. In this study, the allelopathic activity of 170 species from 61 families of Peruvian plants that were collected from the three main regions of Peru – the Costa (Pacific coastline), the Sierra (Andean mountains), and the Selva (Amazonian rainforest) – was evaluated. The allelopathic activity was determined by the Sandwich Method, which can evaluate the activity of leaf leachates. The species that were found to be highly inhibitory in this screening, under the criterion of >90% inhibition of the radicle of lettuce (Lactuca sativa) seedlings, were Aristeguietia ballii and Diplostephium foliosissimum (Asteraceae) and Spondias mombin (Anacardiaceae). All of these species are native plants from Peru. This study gives a strong clue regarding the potential of isolating potent allelochemicals from these plants in the future.     

An evaluation of sand-culture techniques for studying the tolerance of fruit crops to soil-acting herbicides

Sand-culture techniques for determining the tolerance of fruit crops to herbicides applied to the roots were investigated. Of the methods examined, a single application to pots with a closed drainage system was the most useful provided they were protected from rain. A semi-automatic system for applying herbicides was developed for use where repeated treatment was required. Visual scoring of plant condition was the most informative method of assessing response and was reliable. Results correlated well with weight measurements of leaves, shoots or whole plants. For each herbicide ED50 values were derived from dose-response curves and used to express relative tolerance. The slopes of these curves provided an indication of the rate of change of response with dose. The relative tolerance of a range of fruit crops to simazine corresponded to known relative tolerance in field conditions in the U.K. It is concluded that sand-culture techniques can be used as a preliminary screen to find new soil-acting herbicides for perennial crops and to detect differences in tolerance between cultivars. They also enable the direct influence of plant and seasonal factors on response to root-applied herbicides to be studied. Large numbers of treatments can be tested in a small area with the certainty of obtaining positive results. Evaluation des techniques de culture sur sable pour l'étude de la résistance des cultures fruitières aux herbicides agissant par le sol Les auteurs ont étudiè les techniques de culture sur sable pour déterminer la résistance des cultures fruitiéres aux herbicides racinaires, Parmi les méthiodes examinées, celle comportant une seule application, avec un systéme clos de drainage, s'est révélée la plus pratique, à condition qu'elle comporte une protection contre la pluie. Un systéme semi-automatique pour l'application des herbicides a été mis au point pour les cas où des traitements répétés sont nécessaires. L'observation visuelle du comportement de la plante s'est montreée la méthode la plus instructive pour apprécier les réactions; c'est aussi une méthode súre. Les résultats ont montré une bonne concordance avec les mesures pondérales des feuilles, des pousses, ou des plantes entiéres. Pour chaque herbicide, les valeurs de la E.D. 50 ont ét? déduites des courbes de réaction en fonction de la dose et utilisées pour exprimer la résistance relative. La pente de ces courbes a fourni une indication sur le taux de modification de la réaction en fonction de la dose. La résistance relative d'une série de cultures fruitiéres ? la simazine a correspondu ? la résistance relative constatée au champ dans les conditions du Royaume-Uni. Il en est conclu que les techniques de culture sur sable peuvent être utilisées comme tests de sélection primaire pour découvrir de nouveaux herbicides agissant par le sol pour le désherbage des cultures pérennes, ainsi que pour déceler les différences de résistance entre cultivars. Ces techniques rendent ègalement possible l'étude de l'influence directe de la plante et des facteurs saisonniers sur les réactions aux herbicides racinaires. De nombreux traitments peuvent ètre étudiés sur une surface réduite avec la certitude d'obtenir des résultats positifs. Beurteilung von Sandkulture-Techniken für die Untersuchung von Obstgewächsen aufihre Toleranz gegenüber Bodenherbiziden Es wurden Sandkultur-Techniken zur Bestimmung der Toleranz von Obstgewächsen gegenüber bodenapplizierten Herbiziden geprüft. Von den geprüften Methoden war die einmalige Herbizidgabe zu Gefässen mit einem geschlossenen Drainage-system das brauchbarste Verfahren, unter der Voraussetzung. daß die Gefässe vor Regen geschützt waren. Für die Fälle, in denen eine mehrmalige Herbizidapplikation zu erfolgen hat, wurde ein halbautomatisches System entwickelt. Das informativste und zuverlässigste Auswertungsverfahren war die visuelle Bonitur. Die Ergebnisse waren mit Messungen des Gewichts, der Blätter, Sprosse oder der ganzen Pflanzen gut korreliert. Für jedes Herbizid wurden mit Hilfe von Dosis-Wirkungskurven ED₅₀-Werte ermittelt und als Maß der relativen Toleranz benutzt. Die Steigung der Dosis-Wirkungskurven ermöglichten es. die Abhängigkeit von Aufwandmenge und Reaktion zu erfassen. Bei einer Reihe von Obstgewächsen entsprach die relative Toleranz den Werten. die in Großbritannien unter Feld-bedingungen ermittelt wurden. Die Ergebnisse lassen den Schluss zu, dass Sandkultur-Techniken als erster Schritt bei der Suche nach neuen Bodenherbiziden in mehrjährigen Kulturen verwendet werden können, womit auch Toleranzunterschiede zwischen Sorten erfasst werden können. Derartige Verfahren ermöglichen es auch, den Einfluss von Pflanzen und Klimafaktoren auf die herbizidwirkung zu studieren. Mit diesen Techniken können auf kleiner Fläche brauchbare Ergebnisse erzielt werden.     

Influence of chlorine substituents on biological activity of chemicals: a review

A number of well known polychlorinated chemicals are toxicologically and environmentally unsafe. Because of their persistence they are in the focus of public discussions against chlorine chemistry. However, chlorinated organic chemicals in the molecular weight range between 200 and 600 constitute an important and indispensable segment in the arsenal of existing biologically active chemicals used as pharmaceuticals or crop‐protection agents. Over the course of time it has been found empirically that the introduction of a chlorine atom into one or more specific positions of a biologically active molecule may substantially improve the intrinsic biological activity. In some cases the presence of a chlorine atom is crucial for significant activity in compounds derived both from nature and chemical synthesis. But in other cases chlorination diminishes or abolishes biological activity, as shown for chlordane homologues. Thus a chlorine atom, like any other substituent, is a modulator of activity. Almost all non‐reactive chlorinated chemicals and chlorine‐free chemicals are devoid of any biological activity at the highest concentration typically used in primary screening tests for discovery of useful biological properties. The influence of a substituent such as chlorine on the biological activity of a potential drug or crop protection agent still has to be established empirically in biological experiments designed to detect desired activity or toxicological properties. Sometimes chlorine does prove to be the optimum for improvement of activity. Long‐term rigorous investigations of several hundred chlorinated compounds, registered by the authorities as pharmaceutical drugs or crop‐protection agents, show that the generalisation ‘all chlorinated chemicals are dangerous’, deduced from the negative toxicological properties of a hundred chlorinated and reactive compounds of low molecular weight that are relevant in terms of safe working conditions in the chemical industry and for ecological safety, is not justified. Chlorinated compounds are not necessarily toxic or dangerous. Highly reactive chemicals or polychlorinated compounds cannot be compared with regard to toxicological properties with unreactive compounds having a low degree of chlorination. The chlorine atom, as one of many possible substituents used in synthetic organic chemistry, will remain in the future one of the important tools for probing structure–activity relationships in life science research and as a molecular component in commercialised compounds, in order to provide safer, more selective and more environmentally compatible products with higher activity for medicine and agriculture. © 1999 WILEY‐VCH Verlag GmbH     

The application of computer-based techniques in the evaluation of pesticide products

Computer based techniques that have been developed to assist the evaluation of pesticides against veterinary parasites and for the control of public health and stored products pests, are considered. Emphasis is placed on probit regression analysis, tracing the development from a single line assay through various stages to the routine use of multiple assays arranged in a block pattern to give relative potencies of a series of compounds and on the use of Standard Population Base (SPB). SPB involves the generation of sufficient data to build a mathematical model of the interactions between the knockdown component, the kill component and the synergist needed for flykiller aerosols. The model may be interrogated on-line to give comparisons of performance.     

Extended summaries pesticides group symposium natural products as a source for new agricultural chemicals

The following are extended abstracts of six of the papers presented at the above meeting and, as so presented, they are entirely the responsibility of the authors and do not reflect the views of the Editorial Board of Pesticide Science.     

靶向水稻脂氧合酶OsRCI-1的活性小分子化合物筛选体系的建立

为明确虫害诱导水稻脂氧合酶OsRCI-1的生化特性,通过构建水稻脂氧合酶OsRCI-1重组蛋白原核表达体系,对重组蛋白催化条件进行优化,并研究小分子化合物对OsRCI-1活性的影响。结果表明,缓冲液pH和反应温度都能影响水稻OsRCI-1蛋白的催化活性,当缓冲液pH为7.0时催化活性最佳,为169.9 mol·mg~(-1)·min~(-1);在检测的20~50℃反应温度范围内,在25℃和45℃时出现2个催化活性高峰,分别为68.2 mol·mg~(-1)·min~(-1)和70.4 mol·mg~(-1)·min~(-1)。利用建立的OsRCI-1活性检测体系筛选出4种小分子化合物,即水杨苷异羟肟酸、水杨酸、叔丁基对二苯酚和茉莉酸,均对水稻OsRCI-1活性具有调控作用,抑制中浓度依次为0.12、418.67、232.84、2 747.19μmol/L。表明本试验所建立的靶向水稻脂氧合酶活性化合物鉴定体系可用于活性小分子化合物的快速、高通量筛选。