Effects of mutations in Drosophila nicotinic acetylcholine receptor subunits on sensitivity to insecticides targeting nicotinic acetylcholine receptors

Several strains of Drosophila melanogaster possess mutant alleles in nicotinic acetylcholine receptor (nAChR) subunits, Dα1 and Dβ2 that confer resistance to neonicotinoids such as imidacloprid and nitenpyram, and Dα6, that confers resistance to spinosyns. These mutant strains were bioassayed with a selected set of nAChR active insecticides including neonicotinoids, spinosad, and sulfoxaflor, a new sulfoximine insecticide. All of the neonicotinoids examined, except dinotefuran showed reduced insecticidal efficacy on larvae of the Dα1 mutant, suggesting that this subunit may be important in the action of these insecticides. All of the neonicotinoids, including dinotefuran, showed reduced insecticidal efficacy on larvae possessing the Dβ2 mutation. A similar pattern of broad neonicotinoid resistance to that of Dβ2 alone was also observed for larvae with both the mutations (Dα1 + Dβ2). The Dβ2 mutation exhibited a lower level of cross-resistance to sulfoxaflor (<3-fold) than to any of the neonicotinoids (>13-fold). In contrast, there was no cross-resistance for any of the neonicotinoids or sulfoxaflor in adult flies with the Dα6 mutation, which confers high levels of resistance to spinosad. Thus in the D. melanogaster strains studied, target site resistance observed for the neonicotinoids and the spinosyns does not translate directly to resistance towards sulfoxaflor.     

草地贪夜蛾对Bt玉米的抗性与治理对策思考

Bt玉米已在美洲广泛种植20多年,成功控制了欧洲玉米螟Ostrinia nubilalis、草地贪夜蛾Spodoptera frugiperda等玉米重大害虫为害。然而,近年来相继报道在波多黎各、巴西、阿根廷因草地贪夜蛾产生抗性而导致一些Bt玉米抗虫性丧失。尤其是在热带和亚热带地区,多数Bt玉米品种商业化种植仅3年就丧失了对草地贪夜蛾的抗性。本文分析了草地贪夜蛾的生物学和生态学、对Bt杀虫蛋白抗性遗传特征和交互抗性特性、种群抗性基因频率等内因对抗性演化的影响,以及Bt玉米种植的生态环境、耕作栽培制度、Bt玉米种类、抗性治理策略实施情况等外部环境因素对抗性演化的影响。根据我国玉米种植的生态格局,提出了"整体布局,源头治理"的抗性治理对策。即在草地贪夜蛾周年繁殖区要谨慎种植Bt玉米,尤其是避免种植表达Cry1Ab杀虫蛋白的Bt玉米,以避免源头产生抗性而危及温带玉米主产区。遵循差异化(不同杀虫作用机理)选择Bt玉米品种原则,制定精准抗性监测计划,以高剂量-庇护所为抗性治理基本策略,在Bt玉米资源有限的情况下,落实好庇护所尤为重要。     

VA菌根菌与宿主植物之间的相互作用

综述了VA菌根菌与宿主植物这一共生体系之间在生理、分子水平上的相互作用.     

农牧交错带草-畜-田耦合的IRM模拟分析

通过模拟农牧交错带的农牧业生产情况,运用综合速率法(IRM)结合草-畜-田耦合的概念模型进行系统分析,以期预测农牧交错带张家口地区的结构和功能。结果表明:模拟当前的生产模式,到2015年,预测粮食年产量可达到1.88×10⁹kg,畜产品达到0.75×10⁹kg,草产品达到近2.00×10⁹kg;子系统之间耦合后,畜产品产量大幅提升,年增长量达到0.08×10⁹kg,是耦合前的5.76倍,而耦合后粮食产量的增幅不大,年增长量仅比耦合前增加0.01×10⁷kg。综合速率法结合草-畜-田耦合的概念模型对系统的能物流模拟,实现了对耦合系统的数量化、指标化的研究,宏观与微观相结合,具有独到优势,在研究方法论上具有示范意义。     

基于IRM探索深圳都市农业信息资源共享模式

基于IRM理论,以深圳为例,探讨如何有效发挥我国都市农业的信息资源,以期为我国全范围共享农业资源信息的示范性辐射提供借鉴。     

东北羊草草原土壤微生物生长动态模型的研究

研究东北羊草草原杂草土壤微生物生物量、呼吸速率以及土壤环境因子的季节动态。结果表明,杂草土壤微生物生物量、呼吸速率具有明显的季节变化规律,最大值出现在 8月(12.78×10^-3g·g^-1干土,16.24×10^-3g·g^-1干土·d^-1),呈单峰曲线变化趋势。主要与土壤营养成分、水热条件有密切关系。建立了杂草土壤微生物生长模型--IBM模型:Mt+△t=Mto[1+(0.38rn- RDR△t] 。杂草土壤环境因子综合作用指数 rn 变化范围在0.1475-0.4032之间,具有重要的生态学意义。     

Use of imiquimod 5% cream (Aldara™) in cats with multicentric squamous cell carcinoma in situ: 12 cases (2002–2005)*

Multicentric squamous cell carcinoma in situ (MSCCIS) is a variant of squamous cell carcinoma in cats, commonly referred to as Bowen’s‐like disease. Imiquimod 5% cream (Aldara?) is a novel immune response modifier (IRM) that has been reported as a successful treatment for Bowen’s disease in humans. The purpose of this study was to describe clinical findings, treatment protocols and survival in cats with MSCCIS treated with imiquimod 5% cream and to examine the effects of imiquimod 5% cream in cats with MSCCIS. The expression of papillomavirus group‐specific antigen in the study population was also determined. From review of medical records, 12 cats were identified with a histologic diagnosis of MSCCIS and treatment with imiquimod 5% cream. Initial lesions responded to imiquimod 5% cream in all cats. Most cats (75%) developed new lesions. New lesions also responded to imiquimod 5% cream in all cats treated. Five cats (41%) had side effects suspected to be associated with the use of imiquimod 5% cream, including local erythema (25%), increased liver enzymes and neutropenia (8%), and partial anorexia and vomiting (8%). Kaplan–Meier median treatment duration and median survival time probabilities for cats in this study were 1189 days, respectively. A time to failure model was generated as many cats were censored from analysis well before the aforementioned projected median. This model resulted in a shorter median survival time of 243 days. No patient‐related, tumour‐related or treatment‐related prognostic variables were identified. No expression for papilloma group‐specific antigen was found. Imiquimod 5% cream appears to be well tolerated in the majority of cats, and further studies are warranted to further examine its usefulness in cats with this disease.     

Insecticide discovery: An evaluation and analysis

There is an on-going need for the discovery and development of new insecticides due to the loss of existing products through the development of resistance, the desire for products with more favorable environmental and toxicological profiles, shifting pest spectrums, and changing agricultural practices. Since 1960, the number of research-based companies in the US and Europe involved in the discovery of new insecticidal chemistries has been declining. In part this is a reflection of the increasing costs of the discovery and development of new pesticides. Likewise, the number of compounds that need to be screened for every product developed has, until recently, been climbing. In the past two decades the agrochemical industry has been able to develop a range of new products that have more favorable mammalian vs. insect selectivity. This review provides an analysis of the time required for the discovery, or more correctly the building process, for a wide range of insecticides developed during the last 60 years. An examination of the data around the time requirements for the discovery of products based on external patents, prior internal products, or entirely new chemistry provides some unexpected observations. In light of the increasing costs of discovery and development, coupled with fewer companies willing or able to make the investment, insecticide resistance management takes on greater importance as a means to preserve existing and new insecticides.     

Feeding disruption tests for monitoring the frequency of larval lepidopteran resistance to Cry1Ac, Cry1F and Cry1Ab

An alternative to traditional larval lepidopteran resistance-monitoring bioassays was developed. Feeding disruption tests were developed for detecting insects resistant to three Bacillus thuringiensis (Bt) proteins: Cry1Ac, Cry1F and Cry1Ab. The assays rely on a diagnostic dose of Bt toxin in 100-μl hydratable meal pads of artificial diet containing blue indicator dye. The assay was formatted as a portable (palm-sized) plastic plate containing an array of 16 test wells, each containing a single hydratable meal pad with one insect added per well. The diagnostic dose was the concentration of Bt in meal pad rehydration solution that reduced 24 h dyed fecal production of Bt-susceptible neonates to ≤2 fecal pellets per larva. Bt-resistant neonates were able to consume the diagnostic dose of the insecticidal protein and produce >2 blue fecal pellets. The feces were distinctly visible on the white background of the feeding disruption test plate. Diagnostic doses were determined with lab-strain Bt-susceptible Heliothis virescens and Helicoverpa zea. For H. virescens, the diagnostic doses were 10, 20 and 15 μg/ml for Cry1Ac, Cry1F and Cry1Ab, respectively. For H. zea, the diagnostic doses were 40, 200 and 500 μg/ml, respectively. The assays were validated against a lab-strain of Bt-resistant H. virescens and with susceptible larval H. virescens collected as eggs from field-grown tobacco in North Carolina.     

Sequential sampling plan for assessing corn rootworm (Coleoptera: Chrysomelidae) larval injury to Bt maize

In-field product performance assessments are an essential component of corn rootworm (Diabrotica spp.; CRW) resistance management plans for transgenic maize (Zea mays L.) products expressing proteins derived from the bacterium Bacillus thuringiensis (Bt). The goal of a successful field sampling program is to accurately characterize in-field product performance while also minimizing resource demand, as collection of maize root samples to evaluate CRW injury can present resource challenges such as labor intensiveness, potential safety issues, and a limited time window available for sampling. A resource-efficient sequential sampling plan was developed that utilizes data-driven root injury threshold values derived from benchmark product performance data for both single and pyramided Bt maize traits for CRW control. This sequential sampling methodology incorporates unbiased sampling and controlled false positive and false negative error rates, enabling accurate assessment decisions to be made with efficient resource use. Our proposed approach enables systematic and effective classification of in-field Bt maize product performance, with applications to other CRW control technologies besides Bt maize products.