Advance of entomopathogenic nematodes

This paper summarized the history and present condition of studying and utilizing entomopathogenic nematodes at home and abroad, expounded its taxonomy, life cycle and the mechanism with symbiotic bacteria killing host insect. Taxonomy, mycelial form, pathogenic function and anti-bacteria function of symbiotic bacteria were introduced. Production and utilization of entomopathogenic nematodes, the characteristic genetic improvement by use of biological engineering technology, as well as the existing problem and applying foreground were also discussed.

Interactions between Entomopathogenic Nematodes and Entomophagous Insects

The objective of this review article is to clarify the different interactions between entomopathogenic nematodes, as bio-control agents, against other bio-control agents (parasitoids and predators) proposed by the researchers. Thus, it gives clear information concerning the potential of combining them as a part of Integrated Pest Management (IPM) programs against insect pests. Some laboratory studies showed that the treatment of predacious insects by entomopathogenic nematodes (EPNs) at different concentrations can infect and kill the treated larva, nymphs and adults of predators. The percentages of mortality were found to be high (up to 100%), moderate (15% - 35%) or low (3% - 7%). Other studies revealed the resistant of treated predators to nematode-infection. Some predators that were offered infected prey avoid feeding on such prey and, in contrast, the soil predators (ants and mites) consumed the offered cadavers as well as the infective juvenile of the nematodes and did not show any detrimental effects. Mostly, parasitoids cannot complete their development inside or on nematode-infected hosts if parasitism occurs before or early after infection. The parasitoid females may avoid laying eggs in the infected hosts or cannot discriminate between healthy and infected hosts. A field study demonstrated that applying EPNs combined with the predator, Labidura riparia significantly reduced the population of the target pest compared to the nematode or the predator alone. Also, two field experiments indicated that the combination of parasitoids and nematodes can be successful for insect pest management.

Susceptibility of Economic Dipteran Fruit Flies to Entomopathogenic Nematodes

The present review article demonstrates laboratory and field evaluations of entomopathogenic nematodes(EPNs)against different developmental stages of fruit flies.The virulence of the EPNs differed clearly even on the same insect species and/or by the same nematode species.Such differences might be attributed to some reasons such as the method of treatment as well as the concentrations of the tested nematodes.Fruit flies are among the most important insect pests infesting vegetables and fruits causing considerable losses in the yields worldwide.In laboratory studies,the tested nematodes proved to be highly virulent to larvae as percentage of mortality may reach 100%.As for treated pupae,at different ages,the results are variable and controversially;some studies revealed their moderate or high susceptibility to nematode infection and others indicated low susceptibility or resistance to infection.Treated adults,or those emerged from treated larvae or pupae,are also susceptible to infection.In semi-field and field trials,EPNs proved to be successful for reducing the populations of some fruit flies with up to 85%at concentrations not less than 100 infective juveniles(IJs)/cm^2 of soil.However,the field applications of commercial EPNs have been recommended to be 2.5-5 x 10^9 IJs/ha(25-50 IJs/cm^2 of soil).

Biocontrol potential of entomopathogenic nematode,Heterorhabditis indica against pink bollworm,Pectinophora gossypiella(Saunders)(Lepidoptera:Gelechiidae)

Background The emergence of pink bollworm(PBW),Pectinophora gossypiella(Saunders)(Lepidoptera:Gelechiidae),in cotton due to Bt resistance and concealed feeding habit has created a need for alternative,eco-friendly,and cost-effective control methods.This study aimed to evaluate the bio-efficacy and reproductive potential of two native strains of entomopathogenic nematodes(EPNs),Heterorhabditis indica,namely CICR-HI-CL and CICR-HI-MN,against PBW larvae and pupae under in-vitro conditions.Results The larval assay revealed that strain CICR-HI-CL exhibited higher potency than strain CICR-HI-MN against 2nd,3rd,and 4thinstar larvae,with median lethal dose(LD50)values of 5.45,4.45,and 4.60 infective juveniles(IJs)per larva,respectively.In case of pupal bioassay,both EPN strains demonstrated greater virulence when applied directly(LD50values:29.65 and 73.88 IJs per pupa for strains CICR-HI-CL and CICR-HI-MN,respectively)compared to soil application(147.84 and 272.38 IJs per pupa).Both EPN strains successfully penetrated and reproduced on 4thinstar larvae,resulting in maximum production of 19.28 and 20.85 lakh IJs per larva in the next generation when inoculated at 30 IJs per larva.Conclusion The present study has generated useful information on the virulence and reproductive potential of two strains of EPN H.indica(CICR-HI-CL and CICR-HI-MN)against PBW,a dreaded pest of cotton.Higher virulence and reproductive potential of EPN strains demonstrated their ability to multiply,sustain and perpetuate on larval and pupal stages of PBW.The knowledge generated will help formulate effective management strategies for PBW with the inclusion of EPN as a potential biological control candidate.The soil-dwelling life stages viz.,last instar hibernating larvae and pupae of PBW can be the ideal weak links to make a successful use of H.indica for sustainable management of PBW in the cotton ecosystem.However,before taking these EPN strains to field for managing PBW,detailed studies investigating their biocontrol potential against PBW under field conditions are needed.

对铜绿丽金龟具有高致病力的昆虫病原线虫的筛选

为筛选对铜绿丽金龟Anomala corpulenta幼虫具有生防潜力的昆虫病原线虫品系,测定了9个昆虫病原线虫品系对铜绿丽金龟1龄幼虫的致病力,以及不同施用剂量、环境温度及土壤相对湿度条件对线虫致病力的影响。生测结果表明,樱桃异小杆线虫品系Heterorhabditis beicherriana D26-6对铜绿丽金龟幼虫致病力最高,处理11 d后的校正死亡率达到了98.3%;对线虫D26-6致病力的单因子测定发现,侵染铜绿丽金龟幼虫的最佳剂量为150 IJs/头、最佳温度范围为20~30℃、最佳土壤湿度为18%,有较好的开发应用潜力。

昆虫病原线虫对红火蚁的致病力及田间防控效果

红火蚁Solenopsis invicta Buren是一种国际重大外来入侵生物,严重危害农林生产、生命健康、公共安全和生态环境。本研究在室内条件下测定了小卷蛾斯氏线虫Steinernema carpocapsae All品系、长尾斯氏线虫S.longicaudum X-7品系和芫菁夜蛾斯氏线虫S.feltiae SN品系对红火蚁的致病力,并筛选出高致病力品系及其对红火蚁的田间防控效果。结果表明,不同昆虫病原线虫对红火蚁不同虫态的致病力存在显著差异。3种线虫对红火蚁幼虫具有较高的致病力,处理3 d后,幼虫的累计校正致死率均为100%。3种线虫对工蚁的致病力均较弱,处理10 d后的校正死亡率均小于30%。与芫菁夜蛾斯氏线虫SN品系相比,长尾斯氏线虫X-7品系和小卷蛾斯氏线虫All品系对蛹和生殖蚁具有较强的致病能力,10 d后累计校正死亡率均达到90%以上。田间试验表明,施用小卷蛾斯氏线虫All品系对红火蚁工蚁的防控效果最高可达63.7%,且不会增加红火蚁的迁巢风险。综上所述,小卷蛾斯氏线虫All品系和长尾斯氏线虫X-7品系为红火蚁的高致病品系,田间施用小卷蛾斯氏线虫All品系对红火蚁工蚁具有显著的控制作用,可推荐用于红火蚁的生物防治。

昆虫病原线虫共生菌及代谢产物对根结线虫的防治作用

为探讨不同种昆虫病原线虫(EPN)共生菌对根结线虫病的防治效果,开展了温室盆栽定量接种试验;为明确EPN共生菌的代谢产物对根结线虫卵孵化和二龄幼虫活性的影响,进行了室内生测试验。结果表明,Meloidogyne incognita(M.incognita)在中蔬4号番茄上接种剂量为1000、2000和5000个卵·株^(−1)时,昆虫病原线虫共生菌Xb-IGA和Pl-IGA对M.incognita卵的繁殖均有较好的抑制效果,抑制效果为59.4%~73.9%。Meloidogyne hapla(M.hapla)在VFNT番茄上接种剂量为2000个卵·株^(−1)时,昆虫病原线虫共生菌Pl-IGA对M.hapla卵的繁殖抑制效果最好,可达74.5%,与常规药剂阿维菌素(82.2%)差异不显著。4种EPN共生菌均能有效降低M.incognita和M.hapla侵染后的发病程度,对番茄根部生长有不同程度的促进作用。在生测试验7 d时,4种昆虫病原线虫共生菌代谢产物的2倍稀释液和5倍稀释液对M.incognita和M.hapla卵孵化抑制率为55.1%~94.8%,对M.incognita二龄幼虫校正死亡率为34.2%~47.8%,对M.hapla二龄幼虫校正死亡率为59.6%~79.9%。因此,昆虫病原线虫共生菌及其代谢产物对根结线虫是非常有潜力的生物杀线虫资源。

昆虫病原线虫人工培养技术研究与应用进展

昆虫病原线虫是昆虫的专化性寄生天敌,可自主搜寻寄主、杀虫速度快、对环境友好安全,是一类重要的害虫生物防治因子,在害虫可持续治理中具有应用潜力。目前,昆虫病原线虫作为商品化的新型生物杀虫制剂在全球生产销售。然而,昆虫病原线虫的商品化需要高效的人工培养技术。由于昆虫病原线虫的专化性较强,一种成熟的商业化昆虫病原线虫人工培养技术需要根据线虫种类优化。除了优化现有技术,还需研发新的人工培养技术。本文综述了国内外昆虫病原线虫人工培养技术研究和应用的历史和现状,详细介绍了活体培养技术和离体培养技术,讨论了影响昆虫病原线虫产量的主要因素,强调了优化人工培养技术并降低培养成本的必要性。未来,随着人工培养技术的不断优化,在丰富了昆虫病原线虫商品化种类的同时,还可降低农业生产的经济损失,改良土壤环境,具有重要的经济和社会价值。

绿原酸对昆虫病原线虫卡森斯氏线虫寿命及抗氧化活性的调控

为观察绿原酸(CGA)对昆虫病原线虫寿命及抗氧化活性的影响,探究绿原酸对线虫生命活动的调控机制,本文以卡森斯氏线虫作为抗衰老模型,用不同浓度的绿原酸(0、50、100、500、1000μmol/L)处理,探究其对卡森斯氏线虫寿命、抗氧化活性、脂褐素水平、相关基因m RNA表达水平的调控作用,初步探讨绿原酸的潜在作用机理。结果表明,与空白对照组相比,用100μmol/L绿原酸刺激线虫后使处理组最长寿命增加了36.36%,显著抑制体内脂褐素的积累;且该浓度刺激线虫体内的SOD和CAT酶活力,分别提高了1.97倍和2.47倍;此外,q RT-PCR结果显示,100μmol/L CGA喂养线虫后,daf-16、gst-4基因转录水平相比对照分别提高了1.78、3.51,而daf-2基因转录水平呈下降的趋势,降低了0.13。综上可知,绿原酸通过胰岛素/IGF-1信号通路提高昆虫病原线虫卡森斯氏线虫机体的抗氧化能力并延长昆虫病原线虫的寿命。

胰岛素对昆虫病原线虫卡森斯氏线虫0657L生长发育及其共生细菌伯氏致病杆菌0657L的影响

【目的】为探讨胰岛素对昆虫病原线虫卡森斯氏线虫Steinernema kraussei 0657L生长发育及其共生细菌的影响。【方法】吸取1.5 mL 3000头/mL的卡森斯氏线虫0657L悬浮液侵染大蜡螟Galleria mellonella 3龄幼虫,25℃培养24 h后分离卡森斯氏线虫0657L的共生细菌伯氏致病杆菌Xenorhabdus bovenii 0657L;分别用1∶500胰岛素和1∶5000胰岛素处理伯氏致病杆菌0657L后饲喂卡森斯氏线虫0657L,借助体视显微镜观测伯氏致病杆菌0657L在胰岛素处理1~6 d时的菌落直径并计算生长速率,计算卡森斯氏线虫0657L寿命、存活率、每30 s头部摆动次数和每30 s吞咽次数,评价其平均寿命、运动能力及吞咽能力。【结果】与空白对照组相比,1∶5000胰岛素和1∶500胰岛素处理组伯氏致病杆菌0657L的菌落直径在对数生长期(处理2 d时)可分别增大77.2%和54.0%,生长速率可由空白对照组的68.0μm/d分别提高至120.4和104.7μm/d;卡森斯氏线虫0657L寿命分别延长27.3%和45.5%;卡森斯氏线虫0657L 3龄幼虫每30 s头部摆动次数分别提高56.3%和74.7%,3和4龄幼虫及成虫每30 s吞咽次数分别提高50.9%和65.5%,26.8%和35.2%及23.7%和21.1%。【结论】胰岛素可以显著促进卡森斯氏线虫0657L共生细菌伯氏致病杆菌0657L单菌落的生长和提高其生长速率,能够通过伯氏致病杆菌0657L间接延长卡森斯氏线虫0657L的寿命,提高昆虫病原线虫的运动和吞咽能力。本研究结果可以为延长昆虫病原线虫商品货架期提供科学依据,为昆虫病原线虫的高效生物防治提供理论基础。

昆虫和线虫胰岛素/胰岛素样生长因子的生理功能研究进展

胰岛素是由胰岛素细胞分泌的一种分子量较小的蛋白质激素,通过细胞信号转导通路控制调节糖、脂肪和蛋白质代谢,进而对生命有机体产生影响。昆虫和线虫体内均存在胰岛素信号通路,调控其代谢、生长发育和寿命,且均与脊椎动物高度同源。模式生物黑腹果蝇Drosophila melanogaster和秀丽隐杆线虫Caenorhabditis elegans的胰岛素信号通路研究,作为一根探针,为人类胰岛素相关疾病研究提供试验模型,对生命科学的研究具有重要意义,因此有关线虫和昆虫的胰岛素研究较为深入。昆虫病原线虫(entomopathogenic nematode,EPN)作为一种重要的生物防治因子,其生命周期既包括在寄主昆虫内的寄生阶段,又包括在自然界当中的自由生活阶段。在寄生阶段,线虫体内携带的共生细菌主要通过对寄主昆虫的血液循环系统起作用,从而造成寄主昆虫的死亡,因此,EPN与寄主昆虫的血液系统有着密切的关系。综上,探讨胰岛素对EPN的影响,必须同时关注胰岛素对线虫和寄主昆虫的影响。为了能科学系统地展开胰岛素对EPN的影响并进行深入探讨,本文就昆虫和线虫胰岛素/胰岛素样生长因子的生理功能展开综述,以期为研究胰岛素对EPN影响及EPN的应用中胰岛素的干预应用提供思路及理论基础。

日本生物农药及其登记概况

生物农药是日本实施“绿色食品体系战略”的重要工具之一。本文阐述了日本生物农药的定义和范畴,对日本生物农药的登记情况进行分类介绍,以期为其他国家生物农药的研发与应用提供参考。

昆虫病原线虫对昆虫致病机制的研究进展

本文综述了近年来昆虫病原线虫及其他共生菌对宿主昆虫致病机制的研究进展,从昆虫病原线虫对宿主组织、血淋巴、毒素和次生代谢的影响角度分别阐述,以期为研究新型的相关害虫防治方法及可持续开发利用昆虫病原线虫提供参考依据。

昆虫病原线虫防治小白菜黄曲条跳甲的田间效果

为探索防治小白菜黄曲条跳甲的绿色防控方法,本试验比较了昆虫病原线虫、昆虫病原线虫混用化学农药及单用化学农药3种方式对小白菜黄曲条跳甲的田间效果试验。试验结果表明,每667 m^(2)采用昆虫病原线虫3亿尾防治效果好,可有效避免化学药剂安全间隔要求,确保叶菜质量安全。

Microbial control of diamondback moth, Plutella xylostella L. （Lepidoptera： Yponomeutidae） using bacteria （Xenorhabdus nematophila） and its metabolites from the entomopathogenic nematode Steinernema carpocapsae

Cells and cell-free solutions of the culture filtrate of the bacterial symbiont, Xenorhabdus nematophila taken from the entomopathogenic nematode Steinernema carpocapsae in aqueous broth suspensions were lethal to larvae of the diamondback moth Plutella xylostella. Their application on leaves of Chinese cabbage indicated that the cells can penetrate into the insects in the absence of the nematode vector. Cell-free solutions containing metabolites were also proved as effective as bacterial cells suspension. The application of aqueous suspensions of cells of X.nematophila or solutions containing its toxic metabolites to the leaves represents a possible new strategy for controlling insect pests on foliage.

Pathogenicity of bacterium, Xenorhabdus nematophila isolated from entomopathogenic nematode (Steinernema carpocapsae) and its secretion against Galleria mellonella larvae

The entomopathogenic bacterium, Xenorhabdus nematophila was isolated from the hemolymph of Galleria mel- lonella infected with Steinernema carpocapsae. The bacterial cells and its metabolic secretions have been found lethal to the Galleria larvae. Toxic secretion in broth caused 95% mortality within 4 d of application whereas the bacterial cells caused 93% mortality after 6 d. When filter and sand substrates were compared, the later one was observed as appropriate. Similarly, bacterial cells and secretion in broth were more effective at 14% moisture and 25 °C temperature treatments. Maximum insect mortality (100%) was observed when bacterial concentration of 4×106 cells/ml was used. Similarly, maximum bacterial cells in broth (95%) were penetrated into the insect body within 2 h of their application. However, when stored bacterial toxic secretion was applied to the insects its efficacy declined. On the other hand, when the same toxic secretion was dried and then dissolved either in broth or water was proved to be effective. The present study showed that the bacterium, X. nematophila or its toxic secretion can be used as an important component of integrated pest management against Galleria.

A comparative analysis of entomoparasitic nematodes <i>Heterorhabditis bacteriophora</i>and <i>Steinernema carpocapsae</i>

Heterorhabditis bacteriophora and Steinernema carpocapsae are microscopic entomoparasitic nematodes (EPNs) that are attractive, organic alternatives for controlling a wide range of crop insect pests. EPNs evolved with parasitic adaptations that enable them to “feast” upon insect hosts. The infective juvenile, a non-feeding, developmentally arrested nematode stage, is destined to seek out insect hosts and initiates parasitism. After an insect host is located, EPNs enter the insect body through natural openings or by cuticle penetration. Upon access to the insect hemolymph, bacterial symbionts (Photorhabdus luminescens for H. bacteriophora and Xenorhabdus nematophila for S. carpocapsae) are regurgitated from the nematode gut and rapidly proliferate. During population growth, bacterial symbionts secrete numerous toxins and degradative enzymes that exterminate and bioconvert the host insect. During development and reproduction, EPNs obtain their nutrition by feeding upon both the bioconverted host and proliferated symbiont. Throughout the EPN life cycle, similar characteristics are seen. In general, EPNs are analogous to each other by the fact that their life cycle consists of five stages of development. Furthermore, reproduction is much more complex and varies between genera and species. In other words, infective juveniles of S. carpocapsae are destined to become males and females, whereas H. bacteriophora develop into hermaphrodites that produce subsequent generations of males and females. Other differences include insect host range, population growth rates, specificity of bacterial phase variants, etc. This review attempts to compare EPNs, their bacterial counterparts and symbiotic relationships for further enhancement of mass producing EPNs in liquid media.

我国作物病虫害生物防治研究与应用最新进展

本文总结了近5年来我国在作物病虫害生物防治研究和应用方面的最新进展,包括作物害虫、病害(真菌、细菌和病毒病)和线虫的生物防治、植物免疫和昆虫性信息素的研究和应用,以及新方法和新技术在作物病虫控制中的应用。同时,与国外的研究进展进行了比较,指出了存在的主要问题、发展趋势与对策建议。

昆虫病原线虫防治烟草小地老虎技术优化研究

小地老虎Agrotis ipsilon是烟草Nicotiana tabacum移栽期主要的切根害虫,严重危害烟草生产。为研判烟草生产中符合双减(减肥、减药)要求的生物和生态防控技术,集成适合推广的虫害综合治理模式,本研究在云南玉溪华宁县以昆虫病原线虫(EPN)Steinernema carpocapsae All粉剂和化学药剂敌杀死(溴氰菊酯)处理,配合2种幼虫食诱方法(传统引诱剂、人工引诱剂)以及2种增效助剂(激健1、2)组合,调查移栽后烟草幼苗受小地老虎危害死亡率,评价生物药剂、食诱剂和助剂对烟草幼苗的保护效果。结果表明,无论是否存在食诱剂,移栽4 d各施药处理均能显著降低烟草幼苗死亡率,随时间的推移,所有处理的烟草幼苗死亡率均显著上升;无食诱剂情况下,EPN+激健1和敌杀死于移栽7 d仍具显著保苗效果;传统的糖醋酒液食诱法本身具备一定保苗效果,配合施药,初期效果最好,4 d时,烟草幼苗危害率最低达0.83%±0.008%(传统食诱剂+昆虫病原线虫);人工食诱剂持效性最好,移栽10 d时配合EPN、EPN+激健2和敌杀死仍具明显保苗效果。施用化学药剂时,食诱剂本身对保苗效果无显著贡献;使用EPN时,传统食诱法较空白具有显著保苗效果,但与人工食诱法间差异不显著。移栽4 d时,EPN+激健1较单独施放EPN具显著保苗效果,之后调查中添加助剂小区与EPN小区无显著差异。综上所述,EPN粉剂配合人工食诱剂和激健助剂,可长期较好地抑制小地老虎对烟草幼苗危害,为集成烟草全程绿色生态治理模式提供了有效参考。

三种昆虫病原线虫非生物胁迫耐受特性及其共生菌抑菌作用

【目的】研究三种6株系不同昆虫病原线虫对温度、盐浓度耐受特性,筛选出对非生物胁迫耐受性较好的株系,并测定其对大蜡螟幼虫的致病力,分析其共生细菌对金黄色葡萄球菌、沙门氏菌和大肠杆菌的抑制效果,为拮抗病原微生物提供更多新型拮抗菌资源。【方法】采用稀释法统计线虫总数量,分析不同线虫的繁殖能力;分别运用水浴加热法和盐浓度梯度法分析线虫的耐热性、耐盐性;利用梯度稀释法测定其不同剂量对大蜡螟幼虫的致病力;通过涂布法和打孔法测定不同时间段共生菌上清液对病原菌的抑制作用。【结果】从6种线虫中筛选得到一株繁殖和耐受性综合能力较强的菌株小卷蛾斯氏线虫(Steinernema-carpocapsae)XJ-94,每条大蜡螟体内产出的线虫数量为4.96×10^(4)IJs/larva,大蜡螟幼虫产出线虫数量平均为1.24×10^(4)IJs/g;40℃下,处理5 h后,线虫XJ-94存活率为33%,其余株系线虫均已死亡;在17%盐浓度下,处理3 h后,仍有68%的线虫存活。该线虫对大蜡螟幼虫具有较高的致病力,在48 h时,线虫剂量为160 IJs/larva和200 IJs/larva的校正死亡率达到100%。嗜线虫致病杆菌(Xenorhabdus nematophila)XJ-94共生菌发酵上清液在48 h时的抑菌效果最好,对大肠杆菌(E.coli)和金黄色葡萄球菌(S.aureus)的抑制作用显著高于沙门氏菌(Salmonella)。【结论】筛选得到一株繁殖能力和非生物胁迫耐受性较好的昆虫病原线虫株系,该线虫对大蜡螟幼虫具有较高的致病力,其共生菌对大肠杆菌和金黄色葡萄球菌的抑制作用较好。