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本文利用紫外照射、温度、pH、盐度诱导五株溶源性共生菌株Xenorhabdus和Photorhabdus,同时测定斯氏和异小杆属线虫Steinernema carpocapsae A24,S.carpocapsae AIL,S.feltiae English,S.feltiae SN,Heterorbabditis bacterophora H06在体外培养过程中是否存在感染共生细菌的噬菌体.结果未发现噬菌斑,说明实验菌株在实验诱导条件下以及昆虫病原线虫固体培养系统中不可能诱发噬菌体的危害. 相似文献
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昆虫病原线虫共生菌杀虫毒素研究进展 总被引:7,自引:0,他引:7
对昆虫病原线虫共生菌杀虫毒素的种类、与口服毒性有关的杀虫毒素以及口服毒性与杀虫毒素基因的关系等研究进展进行了综述,并对未来的研究方向提出了作者的见解。 相似文献
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嗜线虫致病杆菌属Xenorhabdus和发光杆菌属Photorhabdus细菌隶属肠杆菌科Enterobacteriaceae,对多种害虫致病能力强,分别与斯氏属Steinernema和异小杆属Heterorhabditis昆虫病原线虫互惠共生。该两属共生细菌既存在对昆虫寄主的病原性,又存在与线虫寄主的共生性。共生细菌与其线虫寄主的共生性主要表现以下4方面:(1)细菌产生食物信号诱导滞育不取食的感染期线虫恢复;(2)细菌为线虫生长与繁殖提供营养;(3)细菌能于感染期线虫的肠道定殖与生长;(4)细菌产生杀线虫毒素杀死非共生线虫。本文综述了共生菌以上4方面的共生性及其相关的分子机制。 相似文献
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Comparative study of the entomopathogenic nematode, Steinernema carpocapsae, reared on mutant and wild-type Xenorhabdus nematophila 总被引:2,自引:0,他引:2
The symbiotic interaction between Steinernema carpocapsae and Xenorhabdus nematophila was investigated by comparing the reproduction, morphology, longevity, behavior, and efficacy of the infective juvenile (IJ) from nematodes reared on mutant or wild-type bacterium. Nematodes reared on the mutant X. nematophila HGB151, in which an insertion of the bacterial gene, rpoS, eliminates the retention of the bacterium in the intestinal vesicle of the nematode, produced IJs without their symbiotic bacterium. Nematodes reared on the wild-type bacterium (HGB007) produced IJs with their symbiotic bacterium. One or the other bacterial strain injected into Galleria mellonella larvae followed by exposing the larvae to IJs that were initially symbiotic bacterium free produced progeny IJs with or without their Xenorhabdus-symbiotic bacterium. The two bacterial strains were not significantly different in their effect on IJ production, sex ratio, or IJ morphology. IJ longevity in storage was not influenced by the presence or absence of the bacterial symbiont at 5 and 15 °C, but IJs without their bacterium had greater longevity than IJs with their bacterium at 25 and 30 °C, suggesting that there was a negative cost to the nematode for maintaining the bacterial symbiont at these temperatures. IJs with or without their symbiotic bacterium were equally infectious to Spodoptera exigua larvae in laboratory and greenhouse and across a range of soil moistures, but the absence of the bacterial symbiont inhibited nematodes from producing IJ progeny within the host cadavers. In some situations, such as where no establishment of an alien entomopathogenic nematode is desired in the environment, the use of S. carpocapsae IJs without their symbiotic bacterium may be used to control some soil insect pests. 相似文献
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Entomopathogenic Nematode Production and Application Technology 总被引:1,自引:0,他引:1
Production and application technology is critical for the success of entomopathogenic nematodes (EPNs) in biological control. Production approaches include in vivo, and in vitro methods (solid or liquid fermentation). For laboratory use and small scale field experiments, in vivo production of EPNs appears to be the appropriate method. In vivo production is also appropriate for niche markets and small growers where a lack of capital, scientific expertise or infrastructure cannot justify large investments into in vitro culture technology. In vitro technology is used when large scale production is needed at reasonable quality and cost. Infective juveniles of entomopathogenic nematodes are usually applied using various spray equipment and standard irrigation systems. Enhanced efficacy in EPN applications can be facilitated through improved delivery mechanisms (e.g., cadaver application) or optimization of spray equipment. Substantial progress has been made in recent years in developing EPN formulations, particularly for above ground applications, e.g., mixing EPNs with surfactants or polymers or with sprayable gels. Bait formulations and insect host cadavers can enhance EPN persistence and reduce the quantity of nematodes required per unit area. This review provides a summary and analysis of factors that affect production and application of EPNs and offers insights for their future in biological insect suppression. 相似文献
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Entomopathogenic nematodes: natural enemies of root-feeding caterpillars on bush lupine 总被引:3,自引:1,他引:3
D. R. Strong H. K. Kaya A. V. Whipple A. L. Child S. Kraig M. Bondonno K. Dyer J. L. Maron 《Oecologia》1996,108(1):167-173
A new species of soil-dwelling entomopathogenic nematode Heterorhabditis hepialus killed up to 100% (mean=72%) of root-boring caterpillars of a ghost moth Hepialus californicus in coastal shrub lands. When unchecked, ghost moth caterpillars killed bush lupine, Lupinus arboreus. Here we describe this strange food chain. Although unappreciated by ecologists, entomopathogenic nematodes are widespread and probably one of the most important groups of natural enemies for underground insects. The free-living infective juvenile (IJ) of entomopathogenic nematodes searches for host insects in the soil. A single IJ can kill a host, although several often invade together. After entering the host through a spiracle or other orifice, the IJ regurgitates its symbiotic bacterium, Photorhabdus luminescens, which kills the host within 48 h. The bacteria digest the cadaver and provide food for the exponentially growing nematode population inside. The bacteria produce antibiotics and other noxious substances that protect the host cadaver from other microbes in the soil. When the cadaver is exhausted of resources, IJs break the host integument and can disperse. As many as 420,000 IJs can be produced within a large ghost moth caterpillar. Surface soil of the lupine rhizosphere is the primary habitat of IJs of H. hepialus. Attracted to waste gases emitted by insects, the 0.5-mm-long IJs can move 6 cm/day through moist soil. Prevalences of H. hepialus ranged from as high as 78% of rhizospheres in some lupine stands to almost zero in others, but it was absent from no stand at our study site. Field intensities ranged from 0.003 IJs/cm3 of soil to 7.5 IJs/cm3, and correlated roughly with prevalences among sites. Few ghost moth caterpillars (mean=6.7) succeeded in entering lupine roots where prevalence of H. hepialus was highest, and this stand had lowest mortality (0.02) of mature bush lupine. In the three stands with lowest prevalence (mean = 2%) of this nematode, many caterpillars (mean = 38.5) entered roots, and lupine mortality was high (range = 0.41–1.0). Old aerial photographs indicate that the stands with highest recent nematode prevalence have had little or no mass die-off of lupine over the past 40 years. The photos depict repeated die-offs of lupine during the past four decades in stands with lowest recent prevalence of the nematode. This pattern leads us to entertain the hypothesis that the nematode affects vegetation dynamics indirectly through a trophic cascade. Dispersal of entomopathogenic nematodes is little understood. We found that air drying of soil extirpates H. hepialus and speculate that this nematode is dispersed during the wet season in moist soil bits on the exterior of fossorial insects and mammals. H. hepialus colonized some previously unoccupied lupine rhizospheres during the wet winter-spring season and, obversely, became extinct from some rhizosperes as soil dried in summer. Root-feeding insects have only recently been recognized as a force in communities, and the regulation of these important herbivores is still largely an ecological terra incognita. All evidence indicates that entomopathogenic nematodes are found throughout terrestril ecosystems, and we propose that trophic chains similar to those described in this report should not be uncommon. 相似文献
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Ke Y. Zhang Xiu H. Liu Jin Tan Ying Wang Lei Qiao Gabriel Yedid Chen S. Dai Ru L. Qiu Xiu W. Yan Hao W. Tan Zhen Y. Su Ren Lai Guo F. Gao 《Journal of nematology》2012,44(4):348-360
A novel entomopathogenic nematode species, Heterorhabditidoides rugaoensis n. sp. RG081015, collected from Rugao, China, is described. The new species is morphologically very similar to H. chongmingensis but can be distinguished from it on the basis of some morphological characteristics, combined with molecular data and a cross-hybridization test. Males of the new species can be recognized on the basis of body length averaging 1396.2 μm; lateral field with one ridge; metastome isoglottoid with one hemispherical swellings comprised of two to three well-developed warts; asymmetric spicules; peloderan bursa. In IJs, EP = 134.5 μm; ES = 149.3 μm; tail length = 82.5 μm; and a = 20.5. Hermaphroditic females have four to five lateral ridges. The 18S rDNA and ITS sequences of the two nematodes share 99% and 98% identity, respectively. Phylogenetic trees of 18S rDNA and ITS indicate that the new species is most closely related to H. chongmingensis; thus, the two nematodes belong to the same genus. Failure of cross-hybridization between them indicates that nematode strain RG081015 is a novel species and is described herein as H. rugaoensis n. sp. The LC50 of the novel species against Galleria mellonella were 24.35 IJs / ml within 48 hours of infection. Morphological characteristics, genetic similarity analyses, and phylogenetic relationships provide strong evidence that some species of Oscheius/Insectivora-group should be reassigned to the genus Heterorhabditidoides. 相似文献
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Meloidogyne partityla is a parasite of pecan and walnut. Our objective was to determine interactions between the entomopathogenic nematode-bacterium complex and M. partityla. Specifically, we investigated suppressive effects of Steinernema feltiae (strain SN) and S. riobrave (strain 7–12) applied as infective juveniles and in infected host insects, as well as application of S. feltiae''s bacterial symbiont Xenorhabdus bovienii on M. partityla. In two separate greenhouse trials, the treatments were applied to pecan seedlings that were simultaneously infested with M. partityla eggs; controls received only water and M. partityla eggs. Additionally, all treatment applications were re-applied (without M. partityla eggs) two months later. Four months after initial treatment, plants were assessed for number of galls per root system, number of egg masses per root system, number of eggs per root system, number of eggs per egg mass, number of eggs per gram dry root weight, dry shoot weight, and final population density of M. partityla second-stage juveniles (J2). In the first trial, the number of egg masses per plant was lower in the S. riobrave-infected host treatment than in the control (by approximately 18%). In the second trial, dry root weight was higher in the S. feltiae-infected host treatment than in the control (approximately 80% increase). No other treatment effects were detected. The marginal and inconsistent effects observed in our experiments indicate that the treatments we applied are not sufficient for controlling M. partityla. 相似文献