Increased nutrient availability decreases insect resistance in cranberry

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Newly discovered insect RNA viruses in China

Insects are a group of arthropods and the largest group of animals on Earth,with over one million species described to date.Like other life forms,insects suffer from viruses that cause disease and death.Viruses that are pathogenic to beneficial insects cause dramatic economic losses on agriculture.In contrast,viruses that are pathogenic to insect pests can be exploited as attractive biological control agents.All of these factors have led to an explosion in the amount of research into insect viruses in recent years,generating impressive quantities of information on the molecular and cellular biology of these viruses.Due to the wide variety of insect viruses,a better understanding of these viruses will expand our overall knowledge of their virology.Here,we review studies of several newly discovered RNA insect viruses in China.     

Molecular strategies of plant defense and insect counter-defense

The prediction of human population growth worldwide indicates there will be a need to substantially increase food production in order to meet the demand on food supply.This can be achieved in part by the effective management of insect pests. Since plants have co-evolved with herbivorous insects for millions of years, they have developed an array of defense genes to protect themselves against a wide variety of chewing and sucking insects.Using these naturally-occurring genes via genetic engineering represents an environmentally friendly insect pest-control measure. Insects, however, have been actively evolving adaptive mechanisms to evade natural plant defenses. Such evolved adaptability undoubtedly has helped insects during the last century to rapidly overcome a great many humanimposed management practices and agents, including chemical insecticides and genetically engineered plants. Thus, better understanding of the molecular and genetic basis of plant defense and insect counter-defense mechanisms is imperative, not only from a basic science perspective, but also for biotechnology-based pest control practice. In this review, we emphasize the recent advance and understanding of molecular strategies of attack-counterattack and defense-counter-defense between plants and their herbivores.     

Genetic approaches to reducing losses of stored grain to insects and diseases

Insects and diseases devour or damage a fifth or more of stored food grains each year in many parts of the world. Modern breeding and genomics promise progress in characterizing the resistance to the pests responsible for these losses that is present in the vast and diverse gene pool of cereals, as well as advances in incorporating this resistance into productive and acceptable crop varieties. The impact of such varieties could be dramatic in developing countries, where grain infestations are most common and harmful, and where surging populations require affordable food.     

Can biological control benefit from genetically‐modified crops? Tritrophic interactions on insect‐resistant transgenic plants

Abstract. The use of recombinant DNA technology to develop genetically‐modified crops is considered as a major breakthrough for agriculture by many scientists. However, some scientists, and an even larger proportion of the general public, are sceptical about the advantages and are even more concerned about the potential risk of this new technology. To evaluate this novel technology, cost‐benefit analyses are needed in which the real risks are measured and judged against the benefits. A tiered risk assessment scheme is described herein. This allows comparisons to be made with other insect‐control technologies (e.g. insecticides) and risks to be determined, rather than only hazards being identified. Recombinant DNA technology could allow plants to be designed that are well suited for use alongside biological control programmes. Unfortunately, plant breeders have continued to attempt to breed for total resistance, and biocontrol specialists have ignored the role of the plant in ensuring successful foraging behaviour by insect natural enemies. Although some scientists have highlighted the need to consider both the bottom‐up (plant defence) and top‐down (biocontrol) control of insect pests, there have been few serious attempts to combine these approaches. As more is understood about the proximate and ultimate causes of direct and indirect defences, the potential exists for engineering plants that combine both strategies. This new possibility for controlling insect pests, which will combine both ‘nature’s' own defences with man's ingenuity, may stack the odds in our favour in the continual struggle against insect pests.     

Insect pests and natural enemies in two varieties of quinua (Chenopodium quinoa) at Cusco, Peru

Abstract:  The abundance of insect pests and natural enemies in two varieties of quinua, Chenopodium quinoa (Blanca de Junín and Amarilla de Maranganí) throughout the growing season in the Southern Peruvian Andes is described. The quinua varieties differ, among other traits, in their content of saponins (secondary metabolites associated to plant resistance) late in the season. Whereas Agromyzidae and Cicadellidae were abundant only in the early season, both Chrysomelidae and Aphididae populations showed fluctuations. Likewise, Araneae and Braconidae showed fluctuating numbers during the season. The abundance of Coccinellidae peaked at mid-season whereas that of Syrphidae was high only in the late season. Although the overall abundance of insects was very similar in both varieties of quinua, there were different patterns depending on the season. In the early season there was a tendency towards greater insect numbers on Blanca, but in contrast, in the late season Amarilla (the high-saponin variety) had a higher load of insect pests. This suggests that saponins do not play a major role in quinua resistance against insects. In the early season, no significant relationship between pests and natural enemies held across quinua varieties. In the late season, Aphididae and Coccinellidae were negatively and significantly correlated in both varieties. The temporal population dynamics of Aphididae and both Coccinellidae and Braconidae resembled the traditional predator–prey dynamics.     

Talisia esculenta lectin and larval development of Callosobruchus maculatus and Zabrotes subfasciatus (Coleoptera: Bruchidae)

Bruchid larvae cause major losses in grain legume crops throughout the world. Some bruchid species, such as the cowpea weevil and the Mexican bean weevil, are pests that damage stored seeds. Plant lectins have been implicated as antibiosis factors against insects, particularly the cowpea weevil, Callosobruchus maculatus. Talisia esculenta lectin (TEL) was tested for anti-insect activity against C. maculatus and Zabrotes subfasciatus larvae. TEL produced ca. 90% mortality to these bruchids when incorporated in an artificial diet at a level of 2% (w/w). The LD(50) and ED(50) for TEL was ca. 1% (w/w) for both insects. TEL was not digested by midgut preparations of C. maculatus and Z. subfasciatus. The transformation of the genes coding for this lectin could be useful in the development of insect resistance in important agricultural crops.     

昆虫钠离子通道基因突变及其与杀虫剂抗性关系的研究进展

昆虫电压门控钠离子通道(voltage-gated sodium channel)存在于所有可兴奋细胞的细胞膜上,在动作电位的产生和传导上起重要作用,是有机氯和拟除虫菊酯杀虫剂的靶标位点。在农业和医学害虫控制过程中,由于有机氯和拟除虫菊酯杀虫剂的广泛使用,抗药性问题日益突出。其中,由于钠离子通道基因突变,降低了钠离子通道对有机氯和拟除虫菊酯类杀虫剂的亲和性,从而产生击倒抗性(knock-down resistance, kdr),已成为抗性产生的重要机制之一。本文综述了昆虫钠离子通道的跨膜拓扑结构、功能、进化及其基因的克隆;更重要的是总结了已报道的40多种昆虫40个钠离子通道基因非同义突变,以及钠离子通道基因选择性mRNA剪接和编辑,以及它们与杀虫剂抗性的关系;也评述了钠离子通道基因突变引起蛋白质结构的改变,从而对杀虫剂抗性的影响机制。这些研究对于进一步鉴定与杀虫剂抗性相关的突变及抗性机制,开发有机氯和拟除虫菊酯类杀虫剂抗性分子监测方法具有重要意义。     

Practical importance for conservation of insect diversity in China

Insects are one of the most important groups in the natural world. They affect the life and welfare of humans in many different ways. While some insects are referred to as pests, others are beneficial to humans. For example, they may serve a function as pollinators of many cultivated plants, as natural enemies of harmful species, or as producers of valuable materials such as honey and silk. Several insect species, however, are not currently known as being harmful or beneficial. Nevertheless they are extremely important as essential components of both natural and modified ecosystems. In China, only 1% of insect species described are major pests. The majority of insects are either neutral or beneficial to humans. China, with its vast territory, diverse climate and ecosystems, is amongst the richest countries in insect diversity. However, as a result of the economic and population growth and development, Chinas insect diversity is now faced with habitat degradation, species extinction, and a decline in the natural enemies of harmful pests. These problems are due to the expansion of agriculture, urbanization, industrialization, pollution, mining, tourism, introduced species, hunting, and the illegal trade in endangered species. In order to exploit the beneficial components of insects as biological resources and to effectively control their harmful aspects, many national strategies, legal actions and capacity-building activities have been developed and implemented. These efforts work towards the goal of insect diversity conservation in China.     

Non-specific resistance in brown planthopper resistant indica rice varieties against Plodia interpunctella (Lepidoptera: Phycitidae)

Mechanisms of host plant resistance against insect pests can be manifold. Resistance screenings generally use single target insect pests, but the resistance thus screened may not always be specific to the target insect species. We conducted a test for non‐specific resistance in indica rice varieties with resistance genes against brown planthopper (BPH), by using the Indian meal moth, Plodia interpunctella. The test system was very simple, and only required the non‐pest moth to be reared on rice flour. We compared the survival rate, developmental period and adult weight of the moth on three rice varieties: ‘Nipponbare’, a BPH‐susceptible japonica variety, and ‘Thai Collection 11’ and ‘Pokkali’, two resistant indica varieties. Our results were straightforward and demonstrate that resistance in the two resistant rice varieties is not BPH specific, because development of the moth was retarded and adult body weight was reduced.     

High basal defense gene expression determines sorghum resistance to the whorl‐feeding insect southwestern corn borer

Southwestern corn borer (SWCB, Diatraea grandiosella) and fall armyworm (FAW, Spodoptera frugiperda) are major pests of sorghum in the southern United States. Host plant resistance is a desirable means for reducing plant damage and yield losses from both insects. In this study, we evaluated 12 sorghum lines for whorl‐stage resistance to leaf‐feeding SWCB and FAW in greenhouse and laboratory bioassays. Differential plant responses were detected against the two insects. Among 12 lines tested, CM1821, Della and PI196583 were resistant to both insects, while BTx2752 was largely susceptible. Line R.09110 was resistant to SWCB, but susceptible to FAW, whereas Redbine‐60 was susceptible to SWCB, but not to FAW. In addition, we quantified various chemical components in the plants and determined their association with insect resistance. Tannin and chlorophyll in leaves did not show any significant correlation with resistance to either insects, but contents of soluble protein in general were negatively correlated with resistance to both insects. Endogenous soluble sugar and dhurrin were only positively correlated with resistance to SWCB, but not with FAW resistance. To gain some molecular insight into resistance mechanism of sorghum to SWCB, we performed qPCR reactions for key genes encoding enzymes involved in dhurrin and jasmonic acid (JA) biosynthesis on selected resistant or susceptible lines. Although these genes were rapidly and strongly induced by insect feeding in all lines, the observed resistance is likely explained by higher constitutive dhurrin contents in some resistant lines and higher basal JA biosynthesis in others. Our results suggest that sorghum utilizes multiple strategies to defend itself against SWCB.     

抗寒类蛋白与冷驯化诱发昆虫耐寒性研究进展

昆虫是变温动物,温度对其生长发育、基本行为及进化途径都会产生很大的影响,种群的繁衍面临如何安全度过漫长而寒冷的冬季的挑战。通过长时间的进化,昆虫获得一系列完整的耐寒策略。绝大多数的昆虫都是耐寒昆虫,在陆地寒冷温度刺激下,昆虫受抗寒基因的调控,体内产生大量抗寒物质,如海藻糖、甘油、山梨醇、抗冻蛋白、热激蛋白等,提高昆虫的耐寒能力,使其得以在低温寒冷的条件下成功越冬。同样,经过冷驯化后的昆虫能显著提高昆虫的耐寒力。近年来,关于昆虫耐寒性、抗寒类蛋白的研究不断开展,研究内容涉及昆虫的耐寒性、抗寒基因HSPs和AFPs的调控、冷驯化诱导抗寒等方面。本文综述了昆虫耐寒性、主要耐寒策略及冷驯化诱发昆虫耐寒性增强等研究内容。有助于全面认识昆虫耐寒性及其作用机制,为天敌昆虫低温储存和提高生物防治等应用打下坚实的基础。     

Towards the genetic control of insect vectors: An overview

Insects are responsible for the transmission of major infectious diseases. Recent advances in insect genomics and transformation technology provide new strategies for the control of insect borne pathogen transmission and insect pest management. One such strategy is the genetic modification of insects with genes that block pathogen development. Another is to suppress insect populations by releasing either sterile males or males carrying female‐specific dominant lethal genes into the environment. Although significant progress has been made in the laboratory, further research is needed to extend these approaches to the field. These insect control strategies offer several advantages over conventional insecticide‐based strategies. However, the release of genetically modified insects into the environment should proceed with great caution, after ensuring its safety, and acceptance by the target populations.     

Decreased losses of woody plant foliage to insects in large urban areas are explained by bird predation

Despite the increasing rate of urbanization, the consequences of this process on biotic interactions remain insufficiently studied. Our aims were to identify the general pattern of urbanization impact on background insect herbivory, to explore variations in this impact related to characteristics of both urban areas and insect–plant systems, and to uncover the factors governing urbanization impacts on insect herbivory. We compared the foliar damage inflicted on the most common trees by defoliating, leafmining and gall‐forming insects in rural and urban habitats associated with 16 European cities. In two of these cities, we explored quality of birch foliage for herbivorous insects, mortality of leafmining insects due to predators and parasitoids and bird predation on artificial plasticine larvae. On average, the foliage losses to insects were 16.5% lower in urban than in rural habitats. The magnitude of the overall adverse effect of urbanization on herbivory was independent of the latitude of the locality and was similar in all 11 studied tree species, but increased with an increase in the size of the urban area: it was significant in large cities (city population 1–5 million) but not significant in medium‐sized and small towns. Quality of birch foliage for herbivorous insects was slightly higher in urban habitats than in rural habitats. At the same time, leafminer mortality due to ants and birds and the bird attack intensity on dummy larvae were higher in large cities than in rural habitats, which at least partially explained the decline in insect herbivory observed in response to urbanization. Our findings underscore the importance of top‐down forces in mediating impacts of urbanization on plant‐feeding insects: factors favouring predators may override the positive effects of temperature elevation on insects and thus reduce plant damage.     

论我国昆虫多样性的保护与利用

本文论述了保护昆虫多样性的意义、我国昆虫多样性的基本特点及面临的问题、昆虫多样性的保护战略和利用对策。文中强调指出,昆虫是生物界的一个主要类群,在我国,需要防治的害虫大约只占全部昆虫种类数的1%,其余种类对人类都是有益或者是中性的,它们不仅可以作为显花植物的传粉者、为人类提供食物和各种工业原料,而且可以作为许多害虫或杂草的天敌,以及用于环境净化和科学研究。我国由于地域辽阔,生境复杂,因此,昆虫种类极为丰富,珍稀物种及有益昆虫较多。然而,由于受到人类活动的干扰,我国昆虫多样性面临着生境遭到破坏,物种濒于灭绝,天敌大量减少等问题。为了有效地保护和利用我国的昆虫资源,作者提出了一些战略和对策。     

Sorghum insect problems and management

Sorghum (Sorghum bicolor) has high levels of starch, sugar, and fiber and is one of the most important energy crops in the world. Insect damage is one of the challenges that impacts sorghum biomass production. There are at least 150 insect species that can infest sorghum varieties worldwide. These insects can complete several generations within a growing season, they target various parts of sorghum plants at developmental stages, and they cause significant biomass losses. Genetic research has revealed the existence of resistant genetics in sorghum and insect tolerant sorghum varieties have been identified. Various control methods have been developed, yet more effective management is needed for increasing sorghum biomass production. Although there are no transgenic sorghum products on the market yet, biotechnology has been recognized as an important tool for controlling insect pests and increasing sorghum production.     

General esterases of Bemisia tabaci (Hemiptera: Aleyrodidae) change in response to feed on cotton varieties

The esterase enzymes are a major component of insect detoxification systems and play a crucial role in hydrolyzing lots of xenobiotic compounds. Among insect, generalist herbivores can exhibit developed biochemical defences as a result of exposing to a wide range of plant chemical compounds. To overcome this ability, host plants may affect the level of hydrolases in herbivore insects feeding on. To examine this hypothesis, in the present study total esterase activity was investigated in a highly polyphagous whitefly, Bemisia tabaci, reared on six different varieties of cotton, Gossypium hirsutum. Results showed significant differences in esterase activity of B. tabaci feeding on the host plant varieties. The highest esterase activities were detected in whiteflies feeding on Sk-Tb and Siokra varieties, whereas those whiteflies that feed on Hopicala variety exhibited the least esterase activities. Our findings highlight the important role of host plants in detoxification ability of herbivore insects. The importance of these findings in biology of insect pests and their applications in integrated pest management programmes of B. tabaci have been discussed in detail.     

视觉信号在昆虫检测植物寄主中的作用

植物为数十万种昆虫提供各种资源,如食物、交配、产卵和躲避天敌的场所。目前对昆虫检测植物寄主的研究主要关注昆虫嗅觉系统和植物寄主挥发物之间的相互作用,对昆虫视觉系统发挥的作用关注较少。近年来,对昆虫视觉器官、光行为反应及分子生物学的研究表明,昆虫具有优异的视觉能力,能够辨别植物寄主的颜色、大小和轮廓,应该将视觉纳入昆虫检测植物寄主的研究中。昆虫能够利用视觉信号准确检测寄主,远距离时,主要依靠植物寄主轮廓检测寄主,近距离时,寄主的大小、颜色和形状发挥重要作用。利用昆虫视觉识别寄主的专一性研制诱捕装置,可为害虫的监测和防治提供一定的理论基础。