Costs and benefits of host feeding in the parasitoid wasp Trichogramma turkestanica

Females of the parasitoid wasp Trichogramma turkestanica Meyer (Hymenoptera: Trichogrammatidae) generally host feed after ovipositing on the first egg of Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) they encounter. We measured the impact of host feeding on the fecundity and longevity of females, in absence of host or food, and on the fitness of their progeny. We also determined if the frequency of host feeding is influenced by the humidity level at which T. turkestanica females developed. Host feeding increased egg production by 70% but decreased female longevity. This impact of host feeding on the longevity of females is probably due to the allocation of carbohydrates to egg production at the expense of somatic maintenance. Humidity did not influence the occurrence or duration of host feeding. The size of individuals developing in eggs on which females host fed was smaller, indicating that their fitness was affected.     

Influence of postzygotic reproductive isolation on the interspecific transmission of the paternal sex ratio chromosome in Trichogramma

The paternal sex ratio (PSR) chromosome is a supernumerary chromosome that causes the destruction of the paternal chromosome set in the first mitosis in a fertilized egg. It is known from parasitoid wasps in the genera Nasonia and Trichogramma (Hymenoptera). In these haplodiploids, the egg fertilized by sperm carrying PSR matures as a haploid male that again carries, and is capable of transmitting, the PSR chromosome. Because of its unique transmission behavior, the PSR chromosome may be easily transmitted between species. This study tests whether the interspecific transmission of PSR between Trichogramma kaykai Pinto and Stouthamer and Trichogramma deion Pinto and Oatman (Hymenoptera: Trichogrammatidae) is affected by two types of postzygotic reproductive isolation, i.e., hybrid inviability and hybrid sterility. The results show that PSR can rescue fertilized eggs that would normally be inviable in the interspecific cross and the rescued eggs develop into male offspring that carry PSR. The results suggest that the two types of postzygotic reproductive isolation have no effect on the transmission of PSR between the two Trichogramma species.     

Wolbachia在玉米螟赤眼蜂内的三重感染

Wolbachia是一类广泛存在于节肢动物体内的共生菌。玉米螟赤眼蜂Trichogramma ostriniae是我国玉米田间的优势赤眼蜂种, 据报道, 赤眼蜂种内有Wolbachia感染。本文利用Wolbachia的16s rDNA和wsp基因引物通过PCR方法对玉米螟赤眼蜂的野生种群进行了调查, 发现以wsp基因为鉴定依据, 检测的所有个体都感染了3种Wolbachia ［wOstGDAa (GenBank accession no. EU157103), wOstGDAb (GenBank accession no. EU157104) 和 wOstGDB (GenBank accession no. EU157105)］。本文首次报道了野生赤眼蜂种群内Wolbachia的三重感染率几乎为100%。根据本研究的结果, 可以推测当不同种赤眼蜂寄生同一寄主时, Wolbachia可能会在不同赤眼蜂种间进行横向传播。     

Wolbachia感染对拟澳洲赤眼蜂寿命、生殖力和嗅觉反应的影响

研究了通过共享同一寄主卵,短管赤眼蜂Trichogramma pretiosum体内共生的Wolbachia被水平传递到拟澳洲赤眼蜂T. confusum体内后,Wolbachia对新宿主拟澳洲赤眼蜂的影响。结果表明： Wolbachia的侵染能使拟澳洲赤眼蜂进行不完全的产雌孤雌生殖,增加拟澳洲赤眼蜂子代雌性比例,但却导致了雌蜂寿命缩短和繁殖力降低的生理损失。Wolbachia感染的当代处女蜂及其建立的种群连续5代(F₁～F₅),其子代雌蜂百分率分别为79.17%、76.60%、68.66%、72.58%、68.15%和64.06%,基本上呈现出逐代降低的趋势,并越来越接近对照的63.85%。处女蜂及F₁～F₅代雌蜂的平均寿命分别为4.33、5.50、5.60、6.68、7.32和7.50天,而未感染交配雌蜂寿命为7.59 天;处女蜂及F₁～F₅代雌蜂平均产卵量分别为11.33、70.00、86.41、93.90、102.92和124.38粒/雌,除F₅代外,均显著低于未感染交配雌蜂的产卵量134.81粒/雌。用四臂嗅觉仪测定了Wolbachia新宿主拟澳洲赤眼蜂对寄主小菜蛾的嗅觉反应,结果表明Wolbachia的侵染具轻微干扰拟澳洲赤眼蜂嗅觉反应的负面影响。未感染Wolbachia的拟澳洲赤眼蜂及Wolbachia供体短管赤眼蜂对寄主小菜蛾具较强的嗅觉反应,其雌蜂在小菜蛾腹部鳞片正己烷提取液和小菜蛾卵表正己烷提取液处理区内滞留时间显著或极显著长于对照区。而感染Wolbachia的拟澳洲赤眼蜂F₂代和F₃代雌蜂,尽管在小菜蛾腹部鳞片正己烷提取液处理区内滞留时间比对照区长,但没有达到显著水平;其F₂代雌蜂在小菜蛾卵表正己烷提取液处理区内滞留时间与对照区相比,也没有达到显著水平。随Wolbachia在拟澳洲赤眼蜂种群中垂直感染代数的增加,拟澳洲赤眼蜂对寄主小菜蛾的嗅觉反应恢复正常,在Wolbachia感染后的 F₄～F₆代,雌蜂在两种提取液处理区内的滞留时间均显著或极显著长于对照区。     

The origin of a selfish B chromosome triggering paternal sex ratio in the parasitoid wasp Trichogramma kaykai

This study uses molecular and cytogenetic methods to determine the origin of a B chromosome in some males of the wasp Trichogramma kaykai. This so-called paternal sex ratio (PSR) chromosome transmits only through sperm and shortly after fertilization triggers degeneration of the paternal genome, while keeping itself intact. The resulting embryos develop into haploid B-chromosome-carrying males. Another PSR chromosome with a very similar mode of action is found in the distantly related wasp Nasonia vitripennis and its origin was traced by transposon similarity to the genus Trichomalopsis, which is closely related to Nasonia. To determine whether both PSR chromosomes have a similar origin we aimed to reveal the origin of the Trichogramma PSR chromosome. Using fluorescent in situ hybridization, we discovered a major satellite repeat on the PSR chromosome, the 45S ribosomal DNA. Analysis of the internal transcribed spacer 2 (ITS2) of this repeat showed the presence of multiple ITS2 sequences on the PSR chromosome resembling either the ITS2 of T. oleae or of T. kaykai. We therefore conclude that the Trichogramma PSR chromosome originates from T. oleae or a T. oleae-like species. Our results are consistent with different origins for the PSR chromosomes in Trichogramma and Nasonia.     

The mechanism by which the parasitoid wasp Trichogramma minutum responds to host clusters

Optimal strategies for utilizing a resource require the ability to assess the quantity available. To allocate its progeny appropriately, the parasitic wasp Trichogramma minutum Riley (Hymenoptera: Chalcidoidea: Trichogrammatidae) must respond not only to the size but also to the number of its insect egg hosts which are locally available.By allowing the wasps to oviposit into different clustered arrangements of hosts, it is shown that progeny allocation per host depends on the host number and position of contacting neighbours. In particular, hosts with more neighbours, and thus reduced exposed surface area, are allocated fewer progeny. It is argued that exposed surface area may be the cue used by the wasp to adjust its progeny allocation to the number of local hosts. This discrimination occurs in the absence of superparasitism. A simple model is described which accounts for previously reported counting responses.Observation of examination paths on glass bead models arranged in clusters showed that the frequency and number of edge turns change significantly with the number of neighbours. Changes in these parameters could be used to mediate the wasp's response to the number of local neighbours.The significance of host clustering effects in the use and rearing of Trichogramma for biological control is discussed briefly.

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Der mechanismus, mit dem Trichogramma minutum auf gruppen des wirtes reagiert

Zusammenfassung Optimale Strategien zur Nützung einer Reserve erfordern die Fähigkeit, die verfügbare Menge zu messen. Um die Nachkommen angemessen zu verteilen, muss die parasitische Wespe Trichogramma minutum Riley (Hymenoptera: Chalcidoidea: Trichogrammatidae) sowohl zur Größe, als auch zur Anzahl von Insekten Wirtseiern reagieren können.Die Wespen legten ihre Eier in verschiedene Gruppierungen von Wirtseiern. Es wurde gezeigt, dass die Anzahl der zugewiesenen Nachkommen von der Menge angrenzender Nachbarn und deren räumlicher Verteilung abhängt. Insbesondere werden Wirten mit mehreren Nachbarn, und demzufolge kleinerer freier Oberfläche, weniger Nachkommen zugewiesen. Auf Grund dieser Beobachtung wird die freie Oberfläche als Schlüssel für die Bestimmung der Menge von vorhandenen Wirten vorgeschlagen. Ein einfaches Modell zur Erklärung des vorher beschriebenen Zählverhaltens wird beschrieben. Es wurden Experimente mit Glaskugeln gemacht, die in unterschiedlichen Gruppen angeordnet waren. Es wurde gezeigt, dass einige Parameter des Weges bei der Wirtsuntersuchung (u.a. Häufigkeit und Anzahl der Richtungsänderungen) direkt von der Anzahl der Nachbarn abhängen. Änderungen in diesen Parametern könnten der Reaktion auf die Anzahl angrenzenden Nachbarn zugrunde liegen.Die Bedeutung des Einflusses von Wirtsgruppierung auf die Zucht und die Anwendung der Trichogramma bei der Schädlingsbekämpfung wird kurz diskutiert.

     

孤雌产雌生殖品系松毛虫赤眼蜂产卵强度对Wolbachia诱导的其生殖表型的影响

[目的]松毛虫赤眼蜂Trichogramma dendrolimi是一种用于鳞翅目害虫生物防治的重要卵期寄生蜂.本研究旨在明确孤雌产雌生殖品系松毛虫赤眼蜂的产卵强度对其体内Wolbachia滴度及Wolbachia诱导的孤雌产雌生殖表型的影响.[方法]在室内调查了3个处理组松毛虫赤眼蜂雌蜂不同产卵强度(每日仅1 h供寄...     

Ecology,Wolbachia infection frequency and mode of reproduction in the parasitoid wasp Tetrastichus coeruleus (Hymenoptera: Eulophidae)

Whereas sexual reproduction may facilitate adaptation to complex environments with many biotic interactions, simplified environments are expected to favour asexual reproduction. In agreement with this, recent studies on invertebrates have shown a prevalence of asexual species in agricultural (simplified) but not in natural (complex) environments. We investigated whether the same correlation between reproductive mode and habitat can be found in different populations within one species. The parasitoid wasp Tetrastichus coeruleus forms an ideal model to test this question, since it occurs both in natural and agricultural environments. Further, we investigated whether Wolbachia infection caused parthenogenesis in female‐biased populations. In contrast to the general pattern, in Dutch and French natural areas, we found Wolbachia‐infected, highly female‐biased populations that reproduce parthenogenetically. In contrast, populations on Dutch agricultural fields were not infected with Wolbachia, showed higher frequencies of males and reproduced sexually. However, we also found a female‐only, Wolbachia‐infected population on agricultural fields in north‐eastern United States. All Wolbachia‐infected populations were infected with the same Wolbachia strain. At this moment, we do not have a convincing explanation for this deviation from the general pattern of ecology and reproductive mode. It may be that asparagus agricultural fields differ from other crop fields in ways that favour sexual reproduction. Alternatively, Wolbachia may manipulate life history traits in its host, resulting in different fitness pay‐offs in different habitats. The fixation of Wolbachia in the United States populations (where the species was introduced) may be due to founder effect and lack of uninfected, sexual source populations.     

The influence of previous host age on current host acceptance in Trichogramma

Trichogramma principium Sug. & Sor. females were sequentially offered two portions of the grain moth (Sitotroga cerealella Oliv.) eggs, either young (1-day old) or old (eggs that had developed 6 days at a temperature of 20 °C). The probability of host acceptance depended not only on current host age, but also on the age of the previously offered host. Particularly, Trichogramma females more often oviposited in old host eggs when previously offered young eggs (35–45% of Trichogramma females laid eggs) compared to females which were sequentially offered two portions of old eggs (15–20% of Trichogramma females laid eggs). In other words, parasitization by Trichogramma was stable even when transferred from young (preferred) to old (usually rejected) eggs. Dissections showed that refusing females had significantly more mature eggs than ovipositing females, independent of host age. Among ovipositing females, wasps provided with young hosts had fewer mature ovarial eggs than wasps provided with old hosts. Supposedly, Trichogramma females offered old hosts require a higher motivation to oviposit and have a correspondingly higher egg load than females offered young (preferred) hosts.     

Genetic diversity and Wolbachia infection of the Drosophila parasitoid Leptopilina clavipes in western Europe

Wolbachia are maternally transmitted bacteria that alter their arthropod hosts' reproduction in various ways, including parthenogenesis induction (PI). Wolbachia-induced parthenogenesis can have drastic effects on the genetic structure of its host because it potentially reduces populations to clones without genetic exchange. However, Wolbachia-induced parthenogenesis does not inevitably result in a reduction of genetic variation of infected populations vs. uninfected populations, because the parthenogenetic populations are initially derived from uninfected populations and can thus show similar genetic variation. Here we investigate these issues in infected and uninfected populations of the Drosophila parasitoid Leptopilina clavipes in western Europe. Wasps from 19 sites in the Netherlands, France and northern Spain were screened for Wolbachia and analysed using amplified fragment length polymorphism (AFLP) markers. All the populations from the Netherlands and mid-France were infected with the same two strains of Wolbachia, whereas populations from the Pyrenees were not infected. The infected and uninfected populations show identical levels of genetic variation, but have clearly diverged genetically, indicating the presence of a barrier that prevents gene flow. Within the infected wasps two distinct genotypes were found at multiple localities, indicating the coexistence of multiple clones. The conditions promoting clonal coexistence in L. clavipes are discussed.     

In vitro cultivation of parthenogenesis-inducing Wolbachia in an Aedes albopictus cell line

Parthenogenesis‐inducing (PI) Wolbachia, infecting the parasitoid wasp Trichogramma kaykai Pinto and Stouthamer (Hymenoptera: Trichogrammatidae), were successfully maintained and cultivated in a mosquito, Aedes albopictus (Skuse) (Diptera: Culicidae), cell line, NIAS‐AeAl‐2. A parthenogenesis‐inducing (PI) Wolbachia strains with wasp ovaries were introduced into flasks with cultures of the cell line. The PI Wolbachia proliferated in NIAS‐AeAl‐2 as confirmed using a quantitative polymerase chain reaction method. Our final goal is to induce parthenogenesis in other hymenopteran species of commercial interest through the artificial transfer of PI Wolbachia. As a step towards this goal, we microinjected pupae of Trichogramma with PI Wolbachia culture in NIAS‐AeAl‐2 cells and PI Wolbachia was detected from recipient by PCR with Wolbachia specific primers (wsp gene).     

Oviposition and offspring survival within eggs of European corn borer: discrimination of the host embryo by female Trichogramma nubilale

Oviposition preference and offspring survival relative to the location of the host embryo was tested in the egg parasitoid Trichogramma nubilale on European corn borer host eggs. Females preferentially oviposited near to the embryo on hosts about 24 h old. Survival of Trichogramma was lower when females oviposited far from the embryo, and a higher proportion of host embryos hatched. Females did not show preferences for drilling or oviposition within very young hosts relative to where the embryo would develop, and these eggs did not produce wasps or host larvae. Female behavior was apparently adaptive in day-old hosts, not to very young hosts.     

Host color preferences and short-range searching behavior of the egg parasitoid Trichogramma ostriniae

The color of lepidopteran eggs often varies by species or egg condition, and parasitoids that attack lepidopteran eggs could therefore potentially use color to obtain information about host identity or quality. The objective of our study was to determine whether females of the egg parasitoid Trichogramma ostriniae Pang & Chen (Hymenoptera: Trichogrammatidae) showed differential responses to egg color when searching for hosts over short distances and when evaluating the suitability of encountered eggs. We examined the wasps’ host‐selection behavior in a Petri dish arena using white, yellow, green, and black clay beads as egg models presented against a green background (to mimic leaf color). In no‐choice tests, bead color had a significant effect on the proportion of tested wasps that accepted a bead for further examination, on the time it took wasps to find and begin examining a bead, and on the time that wasps spent examining the beads. However, bead color had only a marginally significant effect on the proportion of wasps attempting to drill into a bead with their ovipositors, and no significant effect on the amount of time they spent drilling. The wasps also showed significant color preferences when given a choice between two adjacent beads of different colors. The results of the no‐choice and choice trials taken together indicated a color preference ranking of yellow > white > green > black. The wasps’ higher preference for the yellow and white egg models generally corresponds to the white or yellowish‐white egg color of T. ostriniae's target host, the European corn borer moth, Ostrinia nubilalis Hübner (Lepidoptera: Crambidae). The wasps’ strong rejection of black egg models is likely to be an adaptive response that reflects the fact that eggs that are wholly or partially black are often unsuitable for parasitization due to advanced caterpillar development, damage to the egg, or previous parasitization.     

高温冲击对沃尔巴克氏体(Wolbachia)诱导孤雌产雌的丽蚜小蜂(Encarsia formosa)生殖和发育的影响

研究了持续高温(31℃恒温)和高适温交替(白天31℃/夜间25℃变温)条件对感染沃尔巴克氏体(Wolbachia)的丽蚜小蜂生殖和发育的影响.结果发现在持续高温条件下,丽蚜小蜂的生殖力和羽化率降低、寿命缩短、后代雄性比例增加,丽蚜小蜂从F1代开始产生雄性后代,且雄性比例在45%以上,F2代雄性比例达到最高值,表明高温冲击会对丽蚜小蜂的控害潜能产生不利的影响,因此在丽蚜小蜂的商业生产和田间应用中要注意环境温度,避免因高温带来的损失.在31℃恒温条件下连续培养3代或6代再转入25℃培养,丽蚜小蜂雄性后代比例和沃尔巴克氏体在丽蚜小蜂雌性群体中的感染率都能够很快恢复到高温处理前的水平.说明沃尔巴克氏体对环境变化有一个自动调节和适应的过程.变温条件下丽蚜小蜂从F2代开始产生雄性后代,但雄性后代比例较低(13%),表明短期高温冲击对丽蚜小蜂的生殖方式影响不大,但是短期高温冲击如果持续作用就会产生积累效应,影响丽蚜小蜂的后代性别.     

四环素对孤雌产雌松毛虫赤眼蜂生殖表型及适合度的影响

共生菌Wolbachia能够诱导许多节肢动物发生产雌孤雌生殖现象。由于该菌无法在宿主细胞外离体培养,人们常采用抗生素处理获得Wolbachia去除或滴度降低的宿主种群,用以研究Wolbachia对宿主的调控作用,但抗生素可能会对宿主产生附加效应。前人研究主要集中在抗生素处理是否可以恢复感染寄生蜂的两性生殖,较少关注抗生素对宿主适合度的影响。本研究利用不同浓度四环素(0、5 mg/mL、15 mg/mL和25 mg/mL)连续饲喂5代来明确四环素对产雌孤雌生殖的松毛虫赤眼蜂Trichogramma dendrolimi适合度的影响。研究结果如下:(1)随各浓度四环素处理世代的增加,雌蜂的繁殖力先降低后升高。在F_1代、F_2代和F_5代中,雌蜂繁殖力随四环素浓度的增加而显著下降,但在F_3代和F_4代中,抗生素浓度对雌蜂繁殖力无显著差异;(2)在四环素不同浓度处理下,F_1代和F_3代的羽化率与对照无显著差异,在F_2代、F_4代和F_5代中,四环素对羽化率存在负面影响;(3)经四环素处理的松毛虫赤眼蜂子代雄性比显著高于对照组。在5 mg/mL的四环素处理条件下,松毛虫赤眼蜂子代雄性比随处理世代的增加而升高,但在25 mg/mL的四环素处理条件下随世代的增加先升高后下降。结果表明:四环素能够使孤雌产雌松毛虫赤眼蜂恢复两性生殖,但对松毛虫赤眼蜂的适合度存在不利影响。此外,随着四环素处理世代的增加,松毛虫赤眼蜂对抗生素产生了一定的适应能力。     

Manipulation of oviposition choice of the parasitoid wasp, Encarsia pergandiella, by the endosymbiotic bacterium Cardinium

Reproductive manipulations of hosts by maternally inherited bacterial endosymbionts often result in an increase in the proportion of infected female hosts in the population. When this involves the conversion of incipient males to genetic or functional females, it presents unique difficulties for symbionts invading hosts with sex-specific reproductive behaviours, such as the autoparasitic Encarsia pergandiella. In sexual forms of this species, female eggs are laid in whitefly nymphs and male eggs are laid in conspecific or heterospecific parasitoids developing within the whitefly cuticle. Further, eggs laid in the 'wrong' host do not ordinarily complete development. This study explored the role of a bacterial symbiont, Cardinium, in manipulating oviposition behaviour in a thelytokous population of E. pergandiella. Oviposition choice was measured by the number and location of eggs deposited by both infected and uninfected adult waSPS in arenas containing equal numbers of hosts suitable for the development of male and female waSPS. Uninfected waSPS included antibiotic-treated female waSPS and (untreated) daughters of antibiotic-treated female waSPS. The choices of waSPS in the thelytokous population treatments were compared with those of a conspecific sexual population. We found that offspring of antibiotic-cured thelytokous waSPS reverted to the behaviour of unmated sexual waSPS, laying their few eggs almost exclusively in hosts appropriate for male eggs. Infected thelytokous waSPS distributed their eggs approximately evenly between host types, much like mated sexual female waSPS. The antibiotic-treated female waSPS exhibited choices intermediate to waSPS in the other two treatments. The change in the observed behaviour appears sufficient to allow invasion and persistence of Cardinium in sexual populations. Lastly, our results suggest a reduction in host discrimination as a possible mechanism by which Cardinium influences this change.     

两种抗生素对携带Wolbachia的短管赤眼蜂生殖模式的影响

携带有Wolbachia的短管赤眼蜂为完全的产雌孤雌生殖。前期的实验表明,利用四环素对携带有Wolbachia的短管赤眼蜂进行除菌处理,但结果并不能获得100%恢复孤雌产雄。本实验拟用环丙沙星与磺胺嘧啶这两种抗生素对携带有Wolbachia的短管赤眼蜂进行除菌效果筛选。实验分3组药剂处理,分别为使用环丙沙星、磺胺嘧啶及环丙沙星与磺胺嘧啶1:1混配液进行除菌处理。各组实验分别进行浓度为0.1 mg/mL、1.0 mg/mL和10.0 mg/mL 3个浓度处理。以无抗生素蜂蜜水处理作为实验对照组。分别检测、记录各处理的F0 - F1代的寄生卵量,F1 - F2代羽化个体数、雌雄个体数,雌雄相嵌体的个体数。结果表明：磺胺嘧啶对短管赤眼蜂的F0代产卵量降低,但F1代恢复产卵量;仅有0.1 mg/mL环丙沙星与磺胺嘧啶1:1混配液对短管赤眼蜂F2代的卵羽化率具有抑制作用,其它的处理与对照组结果无差异。环丙沙星处理后的携带Wolbachia的短管赤眼蜂没出现雄性后代,浓度为0.1 mg/mL环丙沙星与磺胺嘧啶1:1混配液处理在F2代出现了雌雄相嵌体。浓度为1.0 mg/mL和10 mg/mL的环丙沙星与磺胺嘧啶1:1混配液处理和磺胺嘧啶处理在F2代出现了完全雄性后代。使用磺胺嘧啶处理携带Wolbachia的短管赤眼蜂,可更方便快捷获得100%雄性后代。     

Wolbachia在我国广赤眼蜂种群内的感染

Wolbachia是广泛分布于节肢动物生殖组织内的一类细胞内共生菌,它属于原细菌的α亚类,能够通过调控寄主的生殖活动而促进其在寄主种群中的扩散。通过对wsp 基因的克隆及PCR-RFLP分析确定了Wolbachia在我国广赤眼蜂种群内的存在,并发现有2种Wolbachia 菌系的感染,命名为wEvaA和wEvaB。经过克隆分离得到了这2种Wolbachia的wsp基因序列,在GenBank的登录号为AY390279和 AY390280 ,并由基于wsp基因的聚类树中发现,这两种Wolbachia菌系均属于A组。     

卷蛾赤眼蜂体内共生菌Wolbachia对寄主产雌孤雌生殖行为的影响

在30℃的条件下,连续饲养卷蛾赤眼蜂Trichogramma cacoeciaeMarchall10代,观察每代蜂的生物学特性,并进行Wolbachia的wsp基因的分子检测,以研究卷蛾赤眼蜂产雌孤雌生殖行为与其体内共生菌Wolbachia的关系。结果表明,高温下卷蛾赤眼蜂体内的Wolbachia被抑制,4代以后wsp基因的PCR检测结果变为阴性;同时赤眼蜂的产雌孤雌生殖行为的改变程度也随着世代的增加呈递增趋势。这显示卷蛾赤眼蜂的产雌孤雌生殖行为与其体内的共生菌Wolbachia具有一定程度的相关性。     

Using parthenogenesis‐inducing Wolbachia for the selection of optimal lines of the egg parasitoid Trichogramma pretiosum for use in biocontrol

Trichogramma wasps (Hymenoptera: Trichogrammatidae) are egg parasitoids commonly employed in augmentative biological control releases against a variety of mainly lepidopteran pests. By exploiting the mechanism by which the endosymbiotic bacterium Wolbachia induces parthenogenesis in this genus, we created a set of completely homozygous Wolbachia‐infected recombinant isofemale lines (RILs), each consisting of a different combination of the genome of two well‐characterized lines of Trichogramma pretiosum Riley. We subsequently use 16 of these RILs to investigate the effect of genetic variation on various measures associated with offspring production under laboratory conditions. Unsurprisingly, substantial differences were found between the RILs in their propensity to parasitize hosts, the number of hosts they parasitize, and the levels of mortality in their offspring. Such measures can be used to choose an optimal line for biological control purposes. A method was also developed to characterize the 16 RILs using their allelic state at five loci. Essentially, this binary system uses high‐resolution melt analysis to resolve identity at each locus, with alleles originating from either the grandmaternal or grandpaternal line, and is such that each RIL can be distinguished from each other RIL by their allelic state at one or more loci. The method facilitates the easy diagnosis of line origin when two or more lines are competing with each other in competition assays, allowing for the design of more complicated tests of parasitoid quality. Future field experiments will determine which genetic line performs best under more realistic biological control conditions. The fact that these lines are infected with parthenogenesis‐inducing Wolbachia will allow for prolonged rearing without appreciable change in their genetic makeup, which should lead to a predictable biological control performance.