害虫Bt抗性机制研究新方向：昆虫体液免疫系统

作为最成功的生物农药,苏云金芽孢杆菌Bacillus thuringiensis (Bt)杀虫剂已在农业生产中应用了约80年。Bt由于其特异性强、安全高效的特点而得到广泛、成功的应用,极大减少了化学农药的用量,为环境保护作出了巨大贡献。然而,由于长期使用,一些靶标害虫逐渐对Bt产生抗性。本文对昆虫体液免疫及昆虫Bt抗性机制的研究成果进行了总结,已有研究认为害虫对Bt产生抗性的主要原因是毒素激活受阻及(或)毒素受体突变或减少。然而近年越来越多的研究表明,昆虫的Bt抗性还与其免疫系统,特别是与Toll, IMD和proPO-AS等体液免疫通路有关。由此,本文对昆虫体液免疫系统参与昆虫Bt抗性形成的主要通路进行了归纳和推论。IMD免疫通路可能通过MAPK信号通路参与调节昆虫Bt抗性,或可能通过多种免疫反应对抗因中肠组织被Bt破坏而引起的败血症,并通过JNK信号通路促使中肠组织愈合,进而提高其对Bt的抗性。从体液免疫系统切入研究,可能成为深入探索昆虫Bt抗性机制的新方向。     

Managing resistance with multiple pesticide tactics: theory, evidence, and recommendations

Sequences, mixtures, rotations, and mosaics are potential strategies for using more than one pesticide to manage pest populations and for slowing the evolution of pesticide resistance. Results from theoretical models suggest that, under certain conditions, mixtures might be especially effective for resistance management. The assumptions of such models, however, are probably not widely applicable. Potential disadvantages associated with mixtures that are usually not considered in modeling studies include disruption of biological control, promotion of resistance in secondary pests, and intense selection for cross-resistance. Results from limited experimental work suggest that pesticide combinations do not consistently suppress resistance development. More thorough evaluation of tactics that seek to optimize benefits of more than one insecticide will require rigorous experiments with the particular pest and pesticide combinations. Because of the difficulty in generalizing results across systems and the potential negative effects of multiple insecticide use, emphasis on minimizing insecticide use is recommended.     

Strain improvement of fungal insecticides for controlling insect pests and vector-borne diseases

Insect pathogenic fungi play an important natural role in controlling insect pests. However, few have been successfully commercialized due to low virulence and sensitivity to abiotic stresses that produce inconsistent results in field applications. These limitations are inherent in most naturally occurring biological control agents but development of recombinant DNA techniques has made it possible to significantly improve the insecticidal efficacy of fungi and their tolerance to adverse conditions, including UV. These advances have been achieved by combining new knowledge derived from basic studies of the molecular biology of these pathogens, technical developments that enable very precise regulation of gene expression, and genes encoding insecticidal proteins from other organisms, particularly spiders and scorpions. Recent coverage of genomes is helping determine the identity, origin, and evolution of traits needed for diverse lifestyles and host switching. In future, such knowledge combined with the precision and malleability of molecular techniques will allow design of multiple pathogens with different strategies and host ranges to be used for different ecosystems, and that will avoid the possibility of the host developing resistance. With increasing public concern over the continued use of synthetic chemical insecticides, these new types of biological insecticides offer a range of environmental-friendly options for cost-effective control of insect pests.     

The evolution of insecticide resistance: Have the insects won?

While insecticides have greatly improved human health and agricultural production worldwide, their utility has been limited by the evolution of resistance in many major pests, including some that became pests only as a result of insecticide use. Insecticide resistance is both an interesting example of the adaptability of insect pests, and, in the design of resistance management programmes, a useful application of evolutionary biology. Pest susceptibility is a valuable natural resource that has been squandered; at the same time, it is becoming increasingly expensive to develop new insecticides. Pest control tactics should therefore take account of the possibility of resistance evolution. One of the best ways to retard resistance evolution is to use insecticides only when control by natural enemies fails to limit economic damage. This review summarizes the recent literature on insecticide resistance as an example of adaptation, and demonstrates how population genetics and ecology can be used to manage the resistance problem.     

Molecular genetic improvement of cereals: transgenic wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.)

Only modest progress has been made in the molecular genetic improvement of wheat following the production of the first transgenic plants in 1992, made possible by the development of efficient, long-term regenerable embryogenic cultures derived from immature embryos and use of the biolistics method for the direct delivery of DNA into regenerable cells. Transgenic lines expressing genes that confer resistance to environmentally friendly non-selective herbicides, and pests and pathogens have been produced, in addition to lines with improved bread-making and nutritional qualities; some of these are ready for commercial production. Reduction of losses caused by weeds, pests and pathogens in such plants not only indirectly increases available arable land and fresh water supplies, but also conserves energy and natural resources. Nevertheless, the work carried out thus far can be considered only the beginning, as many difficult tasks lie ahead and much remains to be done. The challenge now is to produce higher-yielding varieties that are more nutritious, and are resistant or tolerant to a wide variety of biotic as well as abiotic stresses (especially drought, salinity, heavy metal toxicity) that currently cause substantial losses in productivity. How well we will meet this challenge for wheat, and indeed for other cereal and non-cereal crops, will depend largely on establishing collaborative partnerships between breeders, molecular biologists, biotechnologists and industry, and on how effectively they make use of the knowledge and insights gained from basic studies in plant biology and genetics, the sequencing of plant/cereal genomes, the discovery of synteny in cereals, and the availability of DNA-based markers and increasingly detailed chromosomal maps.     

Myths, models and mitigation of resistance to pesticides

Resistance to pesticides in arthropod pests is a significant economic, ecological and public health problem. Although extensive research has been conducted on diverse aspects of pesticide resistance and we have learned a great deal during the past 50 years, to some degree the discussion about ''resistance management'' has been based on ''myths''. One myth involves the belief that we can manage resistance. I will maintain that we can only attempt to mitigate resistance because resistance is a natural evolutionary response to environmental stresses. As such, resistance will remain an ongoing dilemma in pest management and we can only delay the onset of resistance to pesticides. ''Resistance management'' models and tactics have been much discussed but have been tested and deployed in practical pest management programmes with only limited success. Yet the myth persists that better models will provide a ''solution'' to the problem. The reality is that success in using mitigation models is limited because these models are applied to inappropriate situations in which the critical genetic, ecological, biological or logistic assumptions cannot be met. It is difficult to predict in advance which model is appropriate to a particular situation; if the model assumptions cannot be met, applying the model sometimes can increase the rate of resistance development rather than slow it down. Are there any solutions? I believe we already have one. Unfortunately, it is not a simple or easy one to deploy. It involves employing effective agronomic practices to develop and maintain a healthy crop, monitoring pest densities, evaluating economic injury levels so that pesticides are applied only when necessary, deploying and conserving biological control agents, using host-plant resistance, cultural controls of the pest, biorational pest controls, and genetic control methods. As a part of a truly multi-tactic strategy, it is crucial to evaluate the effect of pesticides on natural enemies in order to preserve them in the cropping system. Sometimes, pesticide-resistant natural enemies are effective components of this resistance mitigation programme. Another name for this resistance mitigation model is integrated pest management (IPM). This complex model was outlined in some detail nearly 40 years ago by V. M. Stern and colleagues. To deploy the IPM resistance mitigation model, we must admit that pest management and resistance mitigation programmes are not sustainable if based on a single-tactic strategy. Delaying resistance, whether to traditional pesticides or to transgenic plants containing toxin genes from Bacillus thuringiensis, will require that we develop multi-tactic pest management programmes that incorporate all appropriate pest management approaches. Because pesticides are limited resources, and their loss can result in significant social and economic costs, they should be reserved for situations where they are truly needed--as tools to subdue an unexpected pest population outbreak. Effective multi-tactic IPM programmes delay resistance (= mitigation) because the number and rates of pesticide applications will be reduced.     

Biological control and sustainable food production

The use of biological control for the management of pest insects pre-dates the modern pesticide era. The first major successes in biological control occurred with exotic pests controlled by natural enemy species collected from the country or area of origin of the pest (classical control). Augmentative control has been successfully applied against a range of open-field and greenhouse pests, and conservation biological control schemes have been developed with indigenous predators and parasitoids. The cost-benefit ratio for classical biological control is highly favourable (1:250) and for augmentative control is similar to that of insecticides (1:2-1:5), with much lower development costs. Over the past 120 years, more than 5000 introductions of approximately 2000 non-native control agents have been made against arthropod pests in 196 countries or islands with remarkably few environmental problems. Biological control is a key component of a 'systems approach' to integrated pest management, to counteract insecticide-resistant pests, withdrawal of chemicals and minimize the usage of pesticides. Current studies indicate that genetically modified insect-resistant Bt crops may have no adverse effects on the activity or function of predators or parasitoids used in biological control. The introduction of rational approaches for the environmental risk assessment of non-native control agents is an essential step in the wider application of biological control, but future success is strongly dependent on a greater level of investment in research and development by governments and related organizations that are committed to a reduced reliance on chemical control.     

Bt杀虫基因与Bt转基因抗虫植物研究进展

苏云金杆菌是一类非常重要的昆虫病原体,它能产生特异性的杀虫结晶蛋白,对农业上和生物医学上的许多有害的昆虫有毒杀作用,这些害虫包括鳞翅目、双翅目、鞘翅目、膜翅目、螨类和线虫。近三十年来,以苏云金杆菌为基础的生物杀虫剂已在世界范围内商业化用于防治重要经济作物的害虫。近年来有关Bt基因的遗传、分子生物学和基因工程已取得显著进展。本文对苏云金杆菌杀虫晶体蛋白基因的分类和杀虫机理及用该类基因构建的工程转基因植物研究状况作一简要综述,同时对Bt基因工程存在的潜在问题和解决途径作了简单的探讨。     

Bt杀虫基因与Bt转基因抗虫植物研究进展

苏云金杆菌是一类非常重要的昆虫病原体,它能产生特异性的杀虫结晶蛋白,对农业上和生物医学上的许多有害的昆虫有毒杀作用,这些害虫包括鳞翅目、双翅目、鞘翅目、膜翅目、螨类和线虫。近三十年来,以苏云金杆菌为基础的生物杀虫剂已在世界范围内商业化用于防治重要经济作物的害虫。近年来有关Ｂｔ基因的遗传、分子生物学和基因工程已取得显著进展。本文对苏云金杆菌杀虫晶体蛋白基因的分类和杀虫机理及用该类基因构建的工程转基因植物研究状况作一简要综述,同时对Ｂｔ基因工程存在的潜在问题和解决途径作了简单的探讨。     

Conserving the efficacy of insecticides against Plutella xylostella (L.) (Lep., Plutellidae)

Abstract:  The diamondback moth (DBM), Plutella xylostella (L.) (Lep., Plutellidae), is one of the most destructive insect pests of crucifers worldwide. It was the first crop insect reported to be resistant to DDT and now in many crucifer-producing regions it has shown significant resistance to almost every insecticide applied in field including biopesticides such as crystal toxins from Bacillus thuringiensis and spinosyns from Saccharopolyspora spinosa . In certain parts of the world, economical production of crucifers has become almost impossible because of its resistance to insecticides and resulting control failure. A coordinated resistance management program needs to be implemented with the involvement of pesticide industry, local pesticide regulatory authorities, scientists and farmers. The judicious use of chemicals in conjunction with other control measures (e.g. biological control agents, resistant varieties, proper fertilization rates) is the best way to manage DBM and other pests of cruciferous crops. Introduction of glucosinolate-sulphatase inhibitors as plant-incorporated-products or sprayable material may also lead to a novel pest management strategy.     

Biology, ecology and control of the Penthaleus species complex (Acari: Penthaleidae)

Blue oat mites, Penthaleus spp. (Acari: Penthaleidae), are major agricultural pests in southern Australia and other parts of the world, attacking various pasture, vegetable and crop plants. Management of these mites has been complicated by the recent discovery of three cryptic pest species of Penthaleus, whereas prior research had assumed a single species. The taxonomy, population genetics, ecology, biology and control of the Penthaleus spp. complex are reviewed. Adult Penthaleus have a dark blue-black body approximately 1 mm in length, and eight red-orange legs. Within Australia, they are winter pests completing two or three generations a season, depending on conditions. The summer is passed as diapausing eggs, when long-distance dispersal is thought to occur. The Penthaleus spp. reproduce by thelytokous parthenogenesis, with populations comprising clones that differ ecologically. The three pest Penthaleus spp. differ markedly in their distributions, plant hosts, timing of diapause egg production and response to pesticides, highlighting the need to develop control strategies that consider each species separately. Chemicals are the main weapons used in current control programs, however research continues into alternative more sustainable management options. Host plant resistance, crop rotations, conservation of natural enemies, and improved timing of pesticide application would improve the management of these pests. The most cost-effective and environmentally acceptable means of control will result from the integration of these practices combined with the development of a simple field-based kit to distinguish the different mite species.     

Baculovirus-based strategies for the management of insect pests: a focus on development and application in South Africa

There is growing concern among governments, scientists, agricultural practitioners and the general public regarding the negative implications of widespread synthetic chemical pesticide application for the control of crop pests. As a result, baculovirus biopesticides are gaining popularity as components of integrated pest management (IPM) programmes in many countries despite several disadvantages related to slow speed of kill, limited host range and complex large scale production. In South Africa, baculoviruses are incorporated into IPM programmes for the control of crop pests in the field, and recent bioprospecting has led to the characterisation of several novel isolates with the potential to be formulated as commercial products. This contribution will provide an overview of the use of baculoviruses against insect pests in South Africa, as well as research and development efforts aimed at broadening their application as biocontrol agents. Challenges faced by researchers in developmental projects as well as potential users of baculoviruses as biopesticides in the field are also discussed.     

Viral biocontrol of invasive vertebrates: Lessons from the past applied to cyprinid herpesvirus-3 and carp (Cyprinus carpio) control in Australia

This paper reviews successful and, briefly, unsuccessful viral biocontrol programs for invasive vertebrate pests to provide lessons for future programs, especially the potential use of cyprinid herpesvirus-3 to control carp in Australia. There have only been three major programs where viral pathogens have been used successfully against invasive vertebrate pests. Myxoma and rabbit hemorrhagic disease viruses were used to control rabbits in Australia, and feline panleukopenia virus helped eliminate cats from sub-Antarctic Marion Island. These programs have shown us that successful viral biocontrol programs for invasive species must include: a thorough understanding of the biology of the target species, and of the viral epidemiology; an integrated pest management program involving both the virus and other control methods; and, a post-release assessment of the ecological benefits of the program. The most important practical lessons identified in this review are: the greatest impact of viruses as biocontrol agents is in the first years following release; unsuspected cross-reactive viruses may confer protection on the target species; and, there may be age- or temperature-related resistance to the virus in the target species.     

Protease inhibitors:recent advancement in its usage as a potential biocontrol agent for insect pest management

Plant derived protease inhibitors(PIs)are a promising defensin for crop im-provement and insect pest management.Although agronomist made significant efforts in utilizing PIs for managing insect pests.the potentials of PIs are still obscured.Insect ability to compensate nutrient starvation induced by dietary PI feeding using different strategies,that is,overexpression of PI-sensitive protease,expression of PI-insensitive proteases,degradation of PI,has made this innumerable collection of PIs worthless.A practical challenge for agronomist is to identify potent PI candidates,to limit insect compensatory responses and to elucidate insect compensatory and resistance mechanisms activated upon herbivory.This knowledge could be further efficiently utilized to identify potential targets for RNAi-mediated pest control.These vital genes of insects could be functionally anno-tated using the advanced gene-editing technique,CRISPR/Cas9.Contemporary research is exploiting different in silico and modern molecular biology techniques to utilize PIs in controlling insect pests efficiently.This review is structured to update recent advancements in this field,along with is chronological background.     

茶树诱导抗虫性的研究进展

为了抵御植食性昆虫的为害,植物在进化过程中形成了包括组成抗性和诱导抗性在内的复杂防御体系.在通过受体识别茶树害虫为害后,茶树会启动早期信号事件,继而激活茉莉酸、水杨酸、乙烯和赤霉素等植物激素信号通路,从而引起次生代谢物的积累,最终对害虫产生直接和间接抗性.基于近年来茶树害虫为害诱导的茶树防御反应及其相关调控机理的研究进...     

Farmers' management of cabbage and cauliflower pests in India and their approaches to crop protection

Cabbage (Brassica olearaceae var. capitata) and cauliflower (Brassica oleracea var. botrytis) are two major vegetables produced and consumed in India. Over the years, they have been cultivated more intensively. This has resulted in higher rates of pest infestation, especially by the diamondback moth (Plutella xylostella) and higher pesticide use. This, in turn, has contributed to insecticide resistance, environmental degradation, and human health impacts, which have triggered a growing interest in alternative management techniques. There is a dearth of knowledge on current pest management practices in cabbage and crucifer. Knowledge about pest management practices is necessary to develop appropriate strategies such as Integrated Pest Management. The main purpose of this study was to obtain comprehensive information on pest management practices among farmers growing cabbage and cauliflower in India.A survey was conducted in the states of Gujarat, West Bengal, and Karnataka from October 2006 through January 2007. Three hundred farmers were interviewed to obtain information on pesticide use in cabbage and cauliflower production, the cost of pesticide use, and socioeconomic characters that influence cabbage and cauliflower production.Farmers relied on pesticides as the major and often exclusive crop protection strategy. Ten of the active ingredients (16.4% of all pesticides reported by all farmers in this survey) were listed as extremely or highly hazardous (classes Ia and Ib) by the World Health Organization. The results confirmed that pesticide use differs between states of India, but that location alone does not determine pesticide spraying pattern. A regression model was used to identify determinants of pesticide application frequency and pesticide cost per hectare. After controlling for location, individual level variables, such as age, education and experience, had significant effects on how often farmers sprayed. Farmers also spent more for pesticides, and sprayed more frequently on cauliflower than on cabbage and on open-pollinated varieties than on hybrid varieties.Our findings highlight the excessive use of pesticides in cabbage and cauliflower, and the reliance on pesticides as the only pest management strategy. The results confirm the need for alternative management strategies. Bt vegetables may be one of these alternative strategies. However, it is questionable whether cultivation of Bt vegetables will reduce the strong reliance on pesticides. Small-scale farmers will need training in the identification of pests, natural enemies, basic ecology, and integrated pest management strategies to ensure sustainable and safe vegetable production.     

农药对捕食性天敌的影响研究进展

捕食性天敌在害虫的自然控制方面起着重要作用。当害虫大发生时,需使用化学农药来进行有效控害,但化学农药会对捕食性天敌的生存造成影响。因此,了解农药对捕食性天敌的影响有利于协调化学防治和生物防治的关系。大部分农药对捕食性天敌的生长发育和繁殖表现为抑制作用,但有的为促进作用。在农药的干扰下,多数捕食性天敌的信息识别能力会降低,少部分会通过提高雄虫接收性信息素的能力或增加雌虫性信息素的释放来诱导求偶行为、增加交配频率。有的杀虫剂会影响捕食性天敌的捕食行为及捕食功能,部分杀虫剂会直接使其捕食功能模型由Holling-Ⅱ型转变为Holling-Ⅰ型。在农药胁迫下,捕食性天敌会产生抗药性,其解毒酶活性升高、保护酶活性改变及靶标部位敏感性下降可能是抗药性产生的机理。农药对捕食性天敌的影响研究在协调害虫化学防治和生物防治中有着重要的理论和现实意义,可以有效地推进捕食性天敌在害虫综合治理中的应用。