Insecticidal activity of menthol derivatives against mosquitoes

BACKGROUND: The insecticidal activity of essential oil of Mentha piperita L. emend. Huds. against local mosquitoes as disease vectors was recognized and found to be due to the presence of menthol, which is the major aroma compound of the oil. The minor compounds of the oil, i.e. menthone, beta-caryophyllene, menthyl acetate, limonene, alpha-pinene and pulegone, showed either less or no activity against the mosquitoes tested. L-Menthol derivatives were synthesized and their knockdown effect and mortality were evaluated against local mosquitoes of Culex quinquefasciatus Say, Aedes aegypti L. and Anopheles tessellatus Theobald as disease vectors. This is the first report of mosquitocidal activity of menthol and its derivatives against Cx. quinquefasciatus, Ae. aegypti and An. tessellatus. RESULTS: Derivative synthesis followed by structure-activity relationship studies identified several derivatives, i.e. menthyl chloroacetate, menthyl dichloroacetate, menthyl cinnamate, menthone glyceryl acetal, thymol, alpha-terpineol and mugetanol, with enhanced mosquitocidal activity against Cx. quinquefasciatus, Ae. aegypti and An. tessellatus relative to the parent compound L-menthone. CONCLUSION: In ester derivatives of L-menthol the optimum activity is dependent on the size and shape of the ester group and the presence of chlorine atoms in the ester group. In structurally related derivatives of L-menthol the optimum activity is dependent on the aromaticity, the degree of unsaturation, the position of the hydroxy group and the type of functional group.     

有机磷酸酯类化合物定量结构-色谱保留关系及稳健性分析

以分子拓扑指数作为结构描述符,采用最佳子集回归方法,建立了35种有机磷酸酯类化合物在3种不同极性固定相上的定量结构-色谱保留关系(QSRR)模型。3个QSRR模型均具有良好的拟合能力,对QSRR模型分别进行了交叉验证及外部数据集验证,结果表明各模型具有较强的预测能力。对QSRR模型的系数、标准误差及相关系数均进行了蒙特卡洛模拟,结果证实蒙特卡洛方法可用于QSRR模型的稳健性分析。     

不同花型牡丹品种亲缘关系的SRAP分析

为了从分子水平上揭示牡丹品种间的遗传差异,本研究用SRAP-PCR技术对20个牡丹品种进行基因组DNA多态性分析,并用UPGMA法构建系统发育树,结果表明,20对引物扩增出131条清晰、稳定的DNA条带,其中90条谱带表现多态性,多态性检测率为68.7%,表明受试牡丹品种之间含较丰富的遗传多态性。UPGMA聚类结果表明,部分花型相同的品种相聚,但部分花型不同的品种亦相聚。说明聚类结果与牡丹品种的花型间可能有一定的相关性,但并未有完全一致的关系。     

沙冬青根瘤菌固氮酶基因nifH PCR-RFLP分析

利用固氮基因nifH PCR扩增,nifH PCR-RFLP及扩增产物序列分析方法对分离自宁夏和内蒙古部分地区的沙冬青根瘤菌代表菌株的nifH 进行了遗传多样性和系统发育分析.结果表明,在80%相似水平上42株根瘤菌nifH PCR-RFLP基因图谱中有5个基因型聚类群.对不同基因型代表菌株的nifH PCR产物进行序列测定和系统发育关系分析,测试菌株在系统发育地位上与中慢生根瘤菌和中华根瘤菌相近,测试菌株与温带中慢生根瘤菌(Mesorhizobium temperatum isolate HAMBI 2583)序列相似性范围为95.6%～96.9%,与草木樨中华根瘤菌(Sinorhizobium meliloti strain CCBAU10062)基因序列相似性范围为99.8%～100%,基因序列同源性较高.本研究中nifH基因所揭示的沙冬青根瘤菌遗传多样性和系统发育关系说明沙冬青根瘤菌受染色体基因背景、地理环境以及菌株个体的进化而存在一定的差异.     

东北黑蜂（Apis mellifera ssp.）亲缘关系的分析

 【目的】从分子水平揭示东北黑蜂与欧洲黑蜂、意大利蜜蜂、卡尼鄂拉蜂、喀尔巴阡蜂、安拉托利亚蜂、高加索蜂以及非洲类型的西方蜜蜂的亲缘关系,为东北黑蜂分类地位的正确认识及其合理保护提供参考。【方法】对来自东北黑蜂国家级自然保护区内9个乡镇的东北黑蜂与上述西方蜜蜂的线粒体DNA（mtDNA）tRNAleu～COⅡ序列进行PCR扩增;同时取部分PCR产物进行DraⅠ酶切分析;并根据酶切类型对相应的PCR产物经纯化、克隆和测序后进行序列分析,并构建Neighbor-Joining(NJ)聚类图。【结果】东北黑蜂mtDNA tRNAleu～COⅡ序列长度为526 bp,P序列缺失,Q序列有5个位点出现碱基转换（4T?C、1A?G）,1个碱基颠换（1A?T）;只有一种DraⅠ酶切类型,其酶切片段长度分别为422、64、47和41 bp,同DNAMAN软件分析的酶切位点一致;其序列特征和酶切类型同西方蜜蜂线粒体C、O分支相似,而与A分支的非洲蜜蜂、M分支的欧洲黑蜂存在较大差异;根据NJ聚类图,东北黑蜂属于线粒体O分支。MtDNA tRNAleu～COⅡ的序列特征和DraⅠ酶切分析表明,东北黑蜂属于线粒体O分支,与同一分支的高加索蜂、安拉托利亚蜂亲缘关系最近,与C分支的意大利蜜蜂、卡尼鄂拉蜂、喀尔巴阡蜂亲缘关系次之,而与M分支的欧洲黑蜂和A分支的非洲蜜蜂亲缘关系较远。【结论】根据NJ聚类图,东北黑蜂处于安拉托利亚蜂和高加索蜂之间,东北黑蜂是否是这两个地理亚种的混合种群,或能否算一个新的地理亚种,还有待进一步的研究。     

西藏色季拉山冷杉林下优势种群种间关联

运用2×2列联表、Х^2检验、Ochiai关联指数、Pearson相关系数和Spearman秩相关系数分析了西藏色季拉山冷杉林下16个灌木优势种和14个草本优势种的种间关系。结果表明：植物对海拔、坡向等环境因子的响应是导致该群落物种分布和种间关联格局的主要原因,呈显著正关联的种对多是由于相似的生活习性,或一种植物为另一种植物创造了适宜的小生境。冷杉林下植被群落种间多呈不显著关联,正负显著关联比远远大于1,可以判定色季拉山冷杉林下植被群落处于较为稳定的演替状态;以基于2×2列联表分析的Х^2检验和基于重要值数量数据的Spearman秩相关分析为主要依据,以Pearson相关系数和Ochjai指数作为对照和补充,所得结果较为理想,将30个优势种群划分为5个生态种组,与现实情况吻合较好。     

分子标记法和形态学特征对杏仁栽培种及野生种基因型的遗传关系构建的辨别

应用23个形态学特征,19个扩增片段长度多态性(AFLP)引物组合,80个随机扩增多态DNA(RAPD)引物和32个简单序列重复(SSR)引物对,比较三种分子标记法在29个杏仁栽培种和3个野生种遗传关系构建中的信息景和效率.根据预期杂合度的评价,与AFLPs和RAPDs相比,SSRs具有较高水平的多态性和较大的信息量.AFLPs预期朵合度值最低,但其辨别效率值最高,因为AFLPs能揭示每个反应中的大量条带,导致各种类型的多样性指数均较高.三种分子标记法对杏仁基因型的辨别效率均较高,只是SSRs无法辨别‘Monagha'和‘Sefied'杏仁基因型.三种分子标记法基因型相似性相关系数统计上显著,但SSR数据要低于RAPDs和AFLPs的值.尽管三种分子标记法树形图拓扑结构存在一些差异,但相似性水平均较高.SSRs、RAPDs和AFLPs的系统树图及其综合数据都能依据地理散布反映大多数栽培种的关系.AMOVA检测到每个地理组中栽培种和野生种的变异.辅助程序分析表明,实验所应用的标记物数量足以保证基因相似性估计的可靠性和标记法间的比较是有意义的.     

稻株挥发物在调节褐飞虱、白背飞虱种内种间关系中的作用

以TN1为供试水稻品种,研究了稻株挥发物在褐飞虱、白背飞虱寻找寄主及调节两种飞虱种内种间关系中的作用。结果表明健康稻株挥发物对褐飞虱、白背飞虱具有明显的引诱作用。当稻株被一种飞虱为害12 h后,其所释放的挥发物对另一种飞虱有明显的引诱作用,但对同种飞虱则无显著的吸引或驱避作用。随着为害程度的加重（为害1 d以上）,两种飞虱均避开虫害株而趋向健康稻株。     

Structure–Activity Relationships of Herbicidal Aryltriazolinones

A series of substituted aryltriazolinones, known to inhibit protoporphyrinogen oxidase, were prepared and their structure–activity requirements at positions 4 and 5 of the aromatic ring investigated. A QSAR equation obtained for substituents at the 5 position identified the hydrophobicity term π and the Sterimol minimum width B₁ as the two parameters affecting in-vitro biological activity. Greenhouse pre-emergence activity correlated with in-vitro activity and the hydrophobicity term π of the substituent at that position. It was found that the phenoxy-4-oxyacetate group at aromatic position 5 was an outlier and had to be considered separately. SAR analysis of substituents at aromatic position 4 revealed that two different models were required to explain all observed substituent effects. In the first model, where the 5 position was occupied by hydrogen, the 4-chlorobenzyloxy group at aromatic position 4 gave the best compound. The second model, where the 5 position of the aromatic ring was occupied by a group other than hydrogen, resulted in a QSAR equation, previously derived, which links substituent effects at position 4 with π and with the electronic para inductive term F_p. In this model the chloro group provides optimum biological activity. The need to separate the aryltriazolinone herbicides into several different classes in order to explain their substituent effects at aromatic positions 4 and 5 could be rationalized if more than one binding conformation, within the same binding site, is possible. © 1997 SCI     

Better land husbandry in Honduras: towards the new paradigm in conserving soil,water and productivity

Land shortages are forcing more smallholder farmers to cultivate tropical steeplands. Resulting accelerated soil erosion is being countered by the promotion of soil conservation (SC) technologies, such as cross‐slope barriers, which aim to reduce soil loss and preserve land productivity. However, farmer adoption rates tend to be low. This is often attributed to the farmers' conservatism or lack of education. Research in Honduras's steeplands demonstrates that farmers value SC, provided that it promotes agricultural production. Field research from 1995–98, involving farmed test plots on slopes greater than 35 per cent (19 degrees), demonstrates that at least one typical SC technology—live barriers of Vetiveria zizanioides (vetiver grass)—has little or no impact on maize yield. This means that farmers see little benefit from their investment in the SC method. They find that erratic rainfall, pests and diseases and a lack of economic resources are far greater threats to their livelihoods than soil erosion. Consequently, SC has a low priority. Keeping soil in place avoids major off‐farm disbenefits. However, the SC technique tested here made no discernible difference to slope foot sediment yields during the life of this study. In sum, a new approach is needed. Promoting ‘Better Land Husbandry’ strategies, which seek to combine farmers' concerns about productivity with conservationists' concerns about reducing soil erosion—often via cover‐management—seem to be the best way forward. Copyright © 2002 John Wiley & Sons, Ltd.