Cotesia Plutellae Research Articles

Identification and characterization of defensin genes from the endoparasitoid wasp Cotesia vestalis (Hymenoptera: Braconidae)

Defensins are members of a large and diverse family of antimicrobial peptides (AMPs) containing three or four intramolecular disulfide bonds. They are widely distributed from vertebrates to invertebrates, and serve as critical defense molecules protecting the host from the invasion of pathogens or protozoan parasites. Cotesia vestalis is a small endoparasitoid wasp that lays eggs in larvae of Plutella xylostella, a cosmopolitan pest of cruciferous crops. We identified and characterized three full-length cDNAs encoding putative defensin-like peptides from C. vestalis, named CvDef1, CvDef2 and CvDef3. Phylogenetic analyses of these sequences showed that they are present in two clades, CITDs and PITDs, indicating a diversity of defensins in C. vestalis. We analyzed their expression patterns in larvae, pupae and adults by semi-quantitative RT-PCR. The results showed that CvDef1 mRNA was expressed from the end stage of the second instar larva, CvDef3 mRNA from the early stage of the second instar larva, and CvDef2 mRNA was expressed in all developmental stages of C. vestalis. Furthermore, CvDef1 showed antimicrobial activity against gram-positive and gram-negative bacteria. Growth kinetics of Staphylococcus aureus indicated that CvDef1 had much better antimicrobial ability than ampicillin, making it a potential candidate for practical use. Transmission electron microscopic (TEM) examination of CvDef1-treated S. aureus cells showed extensive damage to the cell membranes. Our results revealed the basic properties of three defensins in C. vestalis for the first time, which may pave the way for further study of the functions of defensins in parasitism and innate immunity of C. vestalis.

Suitability of a Novel Diet for a Parasitic Wasp,Cotesia plutellae

The braconid Cotesia plutellae (Kurdjumov) (Hymenoptera: Braconidae) is a major solitary, larval endoparasitoid of the diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae). The impact of dietary protein was investigated in the laboratory by comparing performance of C. plutellae on honey, which is commonly used to rear the parasitoid, to that on a novel diet made of honey and protein-rich beebread. Cotesia plutellae was highly stimulated by honey and honey-beebread, with a feeding response exceeding 95%, a level that is comparable with its responses to fructose, glucose, and sucrose. The ability of honey-beebread to support host-parasitoid colonies was also comparable with that of honey. However, parasitoids raised on honey-beebread suppressed diamondback moths in rearing cages 3 weeks before the honey-fed wasps. The development time of C. plutellae reared on honey with or without beebread showed no significant difference, but adult wasps lived longer on honey-beebread. Mean developmental periods from oviposition to pupation and from pupation to adult emergence were 8 and 6 days, respectively. Adult wasps raised on honey-beebread outlived their conspecifics that were raised on honey by at least 4 days. Honey-beebread showed potential as a good food for rearing C. plutellae in the laboratory, and its benefit in parasitoid production is discussed.

A Simple Method for Estimating Instantaneous Levels of Endoparasitism ofPlutellaxylostella(Linnaeus) (Lepidoptera: Plutellidae) by Hymenoptera in the Field

Although endoparasitoids are widely used for biological control of Plutella xylostella (Linnaeus) (Lepidoptera: Plutellidae) throughout the world, current methods do not allow for easy estimation of parasitism levels. I investigated the potential of using ratios of parasitoid cocoons to infestations to develop a simple and practical method of estimating parasitism levels in the field. Crop infestations by the pest and densities of its endoparasitoids' cocoons were recorded at weekly intervals over six consecutive years on unsprayed cabbage. In order to establish if there was a relationship between parasitism levels and ratios of parasitoid cocoons to infestations, samples of host larvae and pupae were collected every week during scouting for rearing in the laboratory. The majority of parasitoid cocoons belonged to the larval endoparasitoid Cotesia vestalis (Haliday) (Hymenoptera: Braconidae), which was the major mortality factor of P. xylostella. Total parasitism levels were positively related to ratios of parasitoid cocoons to infestations. Crop infestation by P. xylostella was low during periods of high parasitism (≥50 %) than during low parasitism (< 50 %), and 50 % parasitism corresponded with 20 % ratio of parasitoid cocoons to infestations. This study shows that ratios of parasitoid cocoons to infestations can be used to estimate background parasitism levels.

Natural parasitism of the diamondback moth, Plutella xylostella (L.) (Lep.: Plutellidae) by a larval parasitoid wasp, Diadegma anurum on different cauliflower cultivars

The diamondback moth (DBM), Plutella xylostella (L.) (Lepidoptera: Yponomeutidae), is the most serious pest of cauliflower fields in central Iran and its control is primarily based on pesticide sprays. Over the past years, a number of new pesticide compounds were introduced onto the market and some of them may cause adverse effects on natural populations of parasitoids associated with DBM. Excessive use of insecticides against the pest did not produce satisfactory results but has caused concerns about environmental pollution and increased pest resistance to chemicals. This research aims to study natural parasitism of pest on different cauliflower cultivars in the fields of south of Tehran. Dominant species of parasitoids include Diadegma anurum, Cotesia plutellae and Oomyzus sokolowskii. The highest parasitism rate was observed by D. anurum that was recorded on Buris cultivar (19.92 ± 1.06) and White cloud cultivar (16.20 ± 1.49) and the lowest parasitism rate was observed on Snow crown cultivar (3.42) and SG cultivar (5.00) during the season.

A copy of cystatin from the diamondback moth Plutella xylostella is encoded in the polydnavirus Cotesia plutellae bracovirus

Cystatins (CSTs) are reversible and competitive inhibitors of cysteine proteases. Some polydnaviruses encode viral CSTs that have been speculated to play a crucial role in viral pathology. Four CSTs have been reported in the episomal genome of a polydnavirus, Cotesia plutellae (synonymous with C. vestalis) bracovirus (CpBV). These 4 CSTs share high sequence homologies with other bracoviral CSTs. Further sequence analysis showed that 2 of the CpBV-CSTs are identical. The remaining 3 CSTs have been designated CpBV-CST1, CpBV-CST2, and CpBV-CST3. Expression analysis indicated that CpBV-CST2 was not expressed in any stage of Plutella xylostella, either parasitized or non-parasitized by C. plutellae. However, both CpBV-CST1 and CpBV-CST3 were expressed in all stages of P. xylostella. Interestingly, these 2 genes were also expressed in non-parasitized P. xylostella in all developmental stages. A CST sequence from the non-parasitized larva was 100% identical with that of CpBV-CST1 for the entire open reading frame (ORF). To understand the role of CpBV-CST1 in viral pathology, the ORF was cloned into a eukaryotic expression vector and transiently expressed in non-parasitized larvae. The in vivo transient expression lasted for at least 4days. Under this condition, the treated larvae suffered significant suppression in immune responses and in development. These results suggest that CpBV-CSTs play a crucial role in parasitism, altering host immune and developmental processes by interrupting normal interactions between CSTs and cysteine proteases in P. xylostella.

Teratocyte-secreting proteins of an endoparasitoid wasp, Cotesia plutellae, prevent host metamorphosis by altering endocrine signals

An endoparasitoid wasp, Cotesia plutellae, parasitizes young larvae of the diamondback moth, Plutella xylostella, with its parasitic factors of polydnavirus, venom, ovarian proteins, and teratocytes (TCs). TCs are originated from embryonic serosal membrane at hatch of C. plutellae egg. Injection of in vitro cultured TCs significantly prolonged a larval period of nonparasitized P. xylostella and impaired a larva-to-pupa metamorphosis. This developmental alteration was also induced by injection of TC-cultured medium (TCM). However, heat-treated TCM significantly lost the inhibitory activity against larval development of P. xylostella. Larvae treated with TC or TCM appeared to undergo abnormal endocrine conditions. Juvenile hormone esterase activity was significantly suppressed at early last instar by injection of TC or TCM. In addition, expression of ecdysone receptor at final instar was lost, but that of insulin receptor was maintained until the end of the larval period in TC or TCM treatment. A proteomic analysis of TCM predicted several teratocyte-secreting proteins (TSPs). The inhibitory effect of host development by TCs was significantly enhanced by an addition of another parasitic factor, C. plutellae bracovirus. These results suggest that C. plutellae TC plays a crucial role in alteration of host development by secreting TSPs.

The relationship between the diamondback moth, climatic factors, cabbage crops and natural enemies in a tropical area

ABSTRACT The impact of abiotic and biotic factors (rainfall, temperature, host plant and natural enemies) on population dynamics of the Plutella xylostella L. diamondback moth was investigated. The experiments were conducted during the rainy and dry seasons for two years (June 2009-April 2011) on unsprayed cabbage plots in Malika (Senegal). Every 10 days, 10 cabbages were randomly selected. Plutella xylostella larvae, pupae and parasitoid cocoons were recorded on each plant. Before each sampling, the diameters and ages of plants were recorded. Temperature and rainfall were also recorded during this study. Larvae and pupae of P. xylstella were higher for the dry season than the rainy season. There was a negative correlation between temperature and P. xylostella populations, and a strong relationship between P. xylostella populations and the age of cabbages. Females oviposited on young cabbages where the presence of young larvae was important, whereas older immature stages were mainly found in older cabbage plants. Parasitoid populations were higher for the dry season than the rainy season. High temperatures did not increase the pest populations and parasitism rate. There was no effect found on pest, plants and natural enemies due to rainfall. There was a positive correlation between pest populations and parasitism. Four Hymenoptera species were found: Oomyzus sokolowskii, Apanteles litae, Cotesia plutellae and Brachymeria citrae, but they were not efficient to control the P. xylostella populations. These results are important for understanding the factors that promote or inhibit pest populations and their natural enemies, and therefore essential for effective crop protection.

English

&nbsp; &nbsp; Seasonal incidences of&nbsp;Plutella xylostella,&nbsp;diamondback moth (DBM) and its associated natural enemies were investigated in two agro-ecological zones of the major crucifer growing areas of Kenya in 2005 and 2006. DBM larvae and pupae were collected from the cabbage and kale crops grown in farmers&rsquo; field and maintained in the laboratory for the emergence of parasitoid or DBM. Four larval, one larval-pupal and one pupal parasitoid species were recorded from DBM. The parasitoids recovered wereDiadegma semiclausum,&nbsp;Diadegma&nbsp;mollipla, Itoplectis&nbsp;spp.,&nbsp;Cotesia plutellae, Apanteles&nbsp;spp.,&nbsp;Oomyzus sokolowskii&nbsp;and&nbsp;Brachymeria&nbsp;species.&nbsp;D. semiclausum&nbsp;was the most dominant species throughout with highest parasitism rates of over 70% recorded in the highlands.&nbsp;C. plutellae,&nbsp;Apanteles&nbsp;and&nbsp;Brachymeria&nbsp;were recovered from mid-altitude semi-arid areas. Generally, parasitism was significantly higher onBrassica oleracea&nbsp;var.&nbsp;capitata.&nbsp;D. semiclausum&nbsp;displaced the indigenous parasitoids from&nbsp;B. oleracea&nbsp;var.&nbsp;capitata. &nbsp; Key words:&nbsp;Brassica oleracea, parasitoids, diamondback moth, seasons, agro-ecological zones. &nbsp;

A viral factor, CpBV15α, interacts with a translation initiation factor, eIF2, to suppress host gene expression at a post-transcriptional level

An endoparasitoid wasp, Cotesia plutellae, possesses its specific symbiotic virus called C. plutellae bracovirus (CpBV) and parasitizes young larvae of Plutella xylostella. CpBV encodes CpBV15α, which was previously shown to interfere with host protein translation. In vivo transient expression of CpBV15α induced a significant decrease in a storage protein level without its transcriptional level change. In vitro translation assay using rabbit reticulocyte lysate showed that CpBV15α suppressed translation efficiency of mRNAs extracted from fat body of P. xylostella. Transient expression of CpBV15α in nonparasitized P. xylostella suppressed humoral immunity and development to pupal and adult stages. Immunoprecipitation (IP) of CpBV15α co-precipitated eIF2 and eIF2B (a guanine nucleotide exchange factor of eIF2) in parasitized P. xylostella. Additionally, IP of eIF2 co-precipitated CpBV15α as well as eIF2B and eIF5 in parasitized larvae. IP with eIF5 antibody showed that relative amount of eIF2 bound to eIF5 was much decreased in parasitized larvae, while significant amount of eIF2 was bound to CpBV15α. These results suggest that CpBV15α inhibits some host mRNA translation by sequestering eIF2.

Protein tyrosine phosphatase encoded in Cotesia plutellae bracovirus suppresses a larva-to-pupa metamorphosis of the diamondback moth, Plutella xylostella

Parasitization by an endoparasitoid wasp, Cotesia plutellae, inhibits a larva-to-pupa metamorphosis of the diamondback moth, Plutella xylostella. This study tested an inhibitory effect of C. plutellae bracovirus (CpBV) on the metamorphosis of P. xylostella. Parasitized P. xylostella exhibited significantly reduced prothoracic gland (PTG) development at the last instar compared to nonparasitized larvae. Expression of the ecdysone receptor (EcR) was markedly suppressed during the last instar larvae parasitized by C. plutellae. By contrast, expression of the insulin receptor (InR) significantly increased in the parasitized larvae. Microinjection of CpBV significantly inhibited the larva-to-pupa metamorphosis of nonparasitized larvae in a dose-dependent manner. Injection of CpBV also inhibited the expression of the EcR and increased the expression of the InR. Individual CpBV segments were transiently expressed in its encoded genes in nonparasitized larvae and screened to determine antimetamorphic viral gene(s). Out of 21 CpBV segments, two viral segments (CpBV-S22 and CpBV-S27) were proved to inhibit larva-to-pupa metamorphosis by transient expression assay. RNA interference of each gene encoded in the viral segments was applied to determine antimetamorphic gene(s). Protein tyrosine phosphatase, early expressed gene, and four hypothetical genes were selected to be associated with the antimetamorphic activity of CpBV. These results suggest that antimetamorphosis of P. xylostella parasitized by C. plutellae is induced by inhibiting PTG development and subsequent ecdysteroid signaling with viral factors of CpBV.

Demonstration of Cytotoxicity against Wasps by Pierisin-1: A Possible Defense Factor in the Cabbage White Butterfly

The cabbage white butterfly, Pieris rapae, produces pierisin-1, a protein inducing apoptosis of mammalian cells. In the present study, the biological activity of pierisin-1 as a protective agent against parasitic wasps for P. rapae was examined. Pierisin-1 caused detrimental effects on eggs and larvae of non-habitual parasitoids for P. rapae, Glyptapanteles pallipes, Cotesia kariyai and Cotesia plutellae at 1–100 µg/ml, levels essentially equivalent to those found in P. rapae larvae. In contrast, eggs and larvae of the natural parasitoid of P. rapae, Cotesia glomerata proved resistant to the toxicity of pierisin-1 through inhibition of pierisin-1 penetration of the surface layer. The expression level of pierisin-1 mRNA in the larvae of P. rapae was increased by parasitization by C. plutellae, whereas it was decreased by C. glomerata. In addition, C. plutellae was associated with elevation of activated pierisin-1 in the hemolymph. From these observations, it is suggested that pierisin-1 could contribute as a defense factor against parasitization by some type of wasps in P. rapae.

Parasitic wasp females are attracted to blends of host-induced plant volatiles: do qualitative and quantitative differences in the blend matter?

Naïve Cotesia vestalis wasps, parasitoids of diamondback moth (DBM) larvae, are attracted to a synthetic blend (Blend A) of host-induced plant volatiles composed of sabinene, n-heptanal, α-pinene, and ( Z)-3-hexenyl acetate, in a ratio of 1.8:1.3:2.0:3.0. We studied whether qualitative (adding ( R)-limonene: Blend B) or quantitative changes (changing ratios: Blend C) to Blend A affected the olfactory response of C. vestalis in the background of intact komatsuna plant volatiles. Naïve wasps showed equal preference to Blends A and B and Blends A and C in two-choice tests. Wasps with oviposition experience in the presence of Blend B preferred Blend B over Blend A, while wasps that had oviposited without a volatile blend showed no preference between the two. Likewise, wasps that had starvation experience in the presence of Blend B preferred Blend A over Blend B, while wasps that had starved without a volatile blend showed no preference between the two. Wasps that had oviposition experience either with or without Blend A showed equal preferences between Blends C and A. However, wasps that had starvation experience in the presence of Blend A preferred Blend C over Blend A, while those that starved without a volatile blend showed equal preferences between the two. By manipulating quality and quantity of the synthetic attractants, we showed to what extent C. vestalis could discriminate/learn slight differences between blends that were all, in principle, attractive.

FOUR SERINE PROTEASE cDNAS FROM THE MIDGUT OF Plutella xylostella AND THEIR PROTEINASE ACTIVITY ARE INFLUENCED BY THE ENDOPARASITOID, Cotesia vestalis

Serine proteinases, which include trypsins and chymotrypsins, play numerous roles in lepidopteran larvae, such as digestion, zymogen activation, and immune defense. Studies of lepidopteran serine proteinases could increase understanding of their feeding preference (polyphagous and monophagous) and facilitate identification of protease inhibitors, which can be engineered for pest management. In this paper, four full-length cDNAs encoding one chymotrypsin and three trypsins were cloned from larval midguts of the diamondback moth, Plutella xylostella. Real-time quantitative polymerase chain reaction (PCR) analysis showed all four serine protease genes were downregulated after P. xylostella was parasitized by the parasitoid wasp Cotesia vestalis. Trypsin and chymotrypsin enzymatic activities within the midgut of nonparasitized and C. vestalis-parasitized P. xylostella larvae were examined using N-a-benzoyl-arg p-nitroanilide and N-succinyl-ala-ala-pro-phe p-nitroanilide as substrates. Trypsin and chymotrypsin activities were decreased in parasitized larvae as compared to untreated larvae, with the effect being more pronounced over time. Chymotrypsin activity in particular exhibited a significant decrease in activity. The correlation of decreased enzymatic activity and transcript abundance suggests parasitization induced downregulation of serine proteinase gene transcripts.

Four heat shock protein genes of the endoparasitoid wasp, Cotesia vestalis, and their transcriptional profiles in relation to developmental stages and temperature.

Heat shock proteins (Hsps) play important roles in the environmental adaptation of various organisms. To explore the functions of Hsps in relation to heat stress and development in Cotesia vestalis, a solitary larval endoparasitoid of Plutella xylostella, four heat shock protein genes, CvHsp40, CvHsc70, CvHsp70 and CvHsp90, were cloned and sequenced from C. vestalis by real-time quantitative PCR and RACE. The cDNA sequence of CvHsp40, CvHsc70, CvHsp70 and CvHsp90 were 1473 bp, 2316 bp, 2279 bp and 2663 bp long, which encode proteins with calculated molecular weights (MW) of 39.1 kDa, 71.2 kDa, 70.1 kDa and 83.3 kDa, respectively. Furthermore, the analysis of genomic DNA confirmed that no introns existed in CvHsp40, CvHsp70 and CvHsp90 while two introns were present in CvHsc70. The amino acid sequence analysis of CvHsps indicated that CvHsp40 is a Type II Hsp40 homolog, CvHsp70 and CvHsc70 are the eukaryotic cytoplasmic Hsp70s, and CvHsp90 is the β-isoform of Hsp90. The divergent transcriptional patterns of CvHsp40, CvHsp70 and CvHsp90 in the different developmental stages suggested that CvHsp transcripts were under different mechanisms of regulation during the development of parasitoid larvae. The dramatic increase of transcripts of CvHsp70 at the third-instar larva coincided with its developmental change in this stage, that is, from inside host to outside host. CvHsp40, CvHsc70 and CvHsp70 showed a trend of sex-specific differences of transcript abundance in the adult stage. All CvHsp transcripts in different developmental stages were significantly induced by heat stress, and the lowest transcript abundances appeared around the temperature 27°C, which probably suggest that this is the most favorable temperature for the development of C. vestalis. Our results suggest that the expression of heat shock proteins reflects to some extent the developmental changes and environmental requirements of insects.

Juvenile hormone regulates an expression of a late gene encoded in a polydnavirus, Cotesia plutellae bracovirus

An endoparasitoid wasp Cotesia plutellae encodes two host translation inhibitory factors (HTIFs) that are expressed in late larval stage of Plutella xylostella parasitized by C. plutellae. The late expressions of HTIFs seemed to be associated with decreasing titer of juvenile hormone (JH) at the last larval instar because an addition of pyriproxyfen (PYR, a JH analog) inhibited the late expression pattern of two HTIF genes. To understand their late expression control, promoter region of an HTIF gene called CpBV15α was cloned by inverse PCR. The cloned HTIF upstream region (1113bp) possessed a putative JH response element (JHRE) and other promoter elements. The putative promoter region was rejoined with an open reading frame of enhanced green fluorescence protein (EGFP). When the recombinant vector construct was injected into early third instar larvae of nonparasitized P. xylostella, it was expressed in fourth larval instar at 72h after injection, compared to relatively early expression in 24h after injection of control construct containing a baculovirus immediate-early promoter. However, recombinant EGFP construct lost the late expression pattern when its promoter region was incomplete by truncating JHRE region. PYR application inhibited EGFP expression of the recombinant construct, but gave little influence on truncated constructs. Interestingly, when the complete promoter construct was injected to pupal stage, its late expression pattern was lost and showed early expression pattern. However, an addition of PYR to pupae, which had been injected with the complete promoter construct, inhibited the reporter gene expression. These results suggest that late expression of a HTIF (CpBV15α) is controlled by its promoter, which is sensitive to host JH titer.

Zamorano y sus Contribuciones a la Agricultura Sostenible a Través del Control Biológico de Plagas

El Centro para el Control Biológico en Centro América (CCBCA) fue creado en 1989 por la Escuela Agrícola Panamericana, financiado por la United States Agency for International Development (USAID) en Honduras. El CCBCA se enfocó en el control biológico clásico, el aumento y la conservación de enemigos naturales. En el 2000 cambió el nombre de Laboratorio de Control Biológico y se enfocó en el aprender haciendo de los estudiantes de la Escuela Agrícola Panamericana y la producción y comercialización de enemigos naturales de plagas agrícolas. El único parasitoide conocido que ataca al picudo de las bromelias (Metamasius quadrilineatus), fue encontrado en las investigaciones del CCBCA; resultó una especie nueva nombrada Lixadmontia franki que fue liberada en Florida en el 2007 para el control biológico del picudo mejicano de las bromelias (Metamasius callizona). Se determinaron los organismos parasíticos de las plagas Plutella xylostella, Mocis latipes, Spodoptera frugiperda, Leptophobia aripa y Liriomyza spp. Cuatro especies de avispas parasíticas exóticas, un baculovirus, un hongo y tres picudos fueron introducidos a Honduras para control biológico clásico: Cotesia plutellae (parasitoide asiático de P. xylostella); Diadromus collaris (parasitoide pupal de P. xylostella); Telenomus remus (parasitoide que ataca a los huevos de 30 especies de lepidópteros); una especie de Eretmocerus (originaria de India, para controlar Bemisia tabaci); los picudos Neochetina bruchi y Neochetina eichhorniae y el hongo Cercospora piaropi (para el control de la maleza acuática lirio de agua (Eichhornia crassipes); y el picudo Neohydronomous affinis (controlador biológico de la maleza acuática lechuga de agua (Pistia stratiotes). En el 2000, Zamorano cambió la estrategia del uso de control biológico y empezó a incursionar en la producción comercial de microrganismos para el control de plagas, debido a una demanda no satisfecha. Los controladores biológicos que ha producido son el hongo antagonista Trichoderma harzianum (Trichozam™) para combatir hongos en el suelo, Beauveria bassiana (Bazam™) para controlar lepidópteros y coleópteros, Lecanicillium lecanii (Verzam™) para el control de áfidos y mosca blanca, Metarhizium anisopliae (Metazam™) para el control de salivazo (Aeneolamia spp.) y larvas de coleópteros en caña de azúcar, y Purpureocillium lilacinum (Pazam™) para controlar nematodos. Además, ha reproducido y vendido la chinche depredadora Orius insidiosus para el control de trips, áfidos y mosca blanca, el ácaro depredador Neoseiulus longispinosus para el control de la arañita roja (Tetranychus spp.) y el nematodo entomófago Heterorhabditis bacteriophora para el control de insectos del suelo, especialmente contra Phyllophaga spp., Cosmopolitus sordidus, larvas de lepidóptera, picudo del camote (Cylas formicarius) y termitas en el suelo. Posiblemente, el mayor aporte es en la enseñanza de las técnicas y tecnologías del control biológico de plagas que se han distribuido por América Latina a través de los graduados de Zamorano que estudiaron y fueron entrenados en Zamorano.DOI: http://dx.doi.org/10.5377/ceiba.v52i1.966

Parasitic wasp females are attracted to blends of host-induced plant volatiles: do qualitative and quantitative differences in the blend matter?

Naïve Cotesia vestalis wasps, parasitoids of diamondback moth (DBM) larvae, are attracted to a synthetic blend (Blend A) of host-induced plant volatiles composed of sabinene, n-heptanal, α-pinene, and ( Z)-3-hexenyl acetate, in a ratio of 1.8:1.3:2.0:3.0. We studied whether qualitative (adding ( R)-limonene: Blend B) or quantitative changes (changing ratios: Blend C) to Blend A affected the olfactory response of C. vestalis in the background of intact komatsuna plant volatiles. Naïve wasps showed equal preference to Blends A and B and Blends A and C in two-choice tests. Wasps with oviposition experience in the presence of Blend B preferred Blend B over Blend A, while wasps that had oviposited without a volatile blend showed no preference between the two. Likewise, wasps that had starvation experience in the presence of Blend B preferred Blend A over Blend B, while wasps that had starved without a volatile blend showed no preference between the two. Wasps that had oviposition experience either with or without Blend A showed equal preferences between Blends C and A. However, wasps that had starvation experience in the presence of Blend A preferred Blend C over Blend A, while those that starved without a volatile blend showed equal preferences between the two. By manipulating quality and quantity of the synthetic attractants, we showed to what extent C. vestalis could discriminate/learn slight differences between blends that were all, in principle, attractive.

배추좀나방에 대한 프루텔고치벌과 미생물농약의 통합생물방제

국내 배추좀나방(Plutella xylostella) 집단은 피레스로이드 농약에 대해서 저항성을 보이며, 이는 이 살충제의 작용점인 소듐이온채널 유전자의 돌연변이에 기인된다. 더욱이 배추좀나방은 대부분 상용화된 살충제에 대해서 저항성을 발달시킬 수 있다. 본 연구는 배추좀나방을 효과적으로 방제하기 위해 내부기생성 천적인 프루텔고치벌(Cotesia plutellae)과 미생물농약인 Bacillus thuringiensis의 혼합처리 기술을 개발하기 위해 수행되었다. 프루텔고치벌이 감수성과 저항성 배추좀나방에 대한 기생 선호성에 차등이 있는 지 조사하기 위해 다섯 개 서로 다른 집단에 대해서 살충제 감수성과 프루텔고치벌 기생성 차이를 비교하였다. 이들 배추좀나방 집단들은 피레스로이드, 유기인계, 네오니코틴계 및 곤충성장조절제를 포함하는 세 종류의 상용 살충제에 대한 약제 감수성에서 뚜렷한 차이를 보였다. 그러나 이들 집단들은 프루텔고치벌에 의한 기생률에서는 차이를 보이지 않았다. 더욱이 기생된 배추좀나방은 B. thuringiensis에 대해서 감수성이 증가되었다. 프루텔고치벌이 갖는 면역억제인자 가운데 바이러스 유래 ankyrin 유전자(vankyrin)를 비기생된 배추좀나방에 발현시켰다. Vankyrin의 발현은 배추좀나방 3령충의 B. thuringiensis에 대한 감수성을 현격하게 증가시켰다. 즉, 프루텔고치벌에 의해 야기된 면역저하가 B. thuringiensis의 살충력을 증가시켰다. 이러한 결과들은 프루텔고치벌과 미생물농약인 B. thuringiensis의 혼합처리가 살충제 저항성 배추좀나방을 효과적으로 방제할 수 있다고 제시하고 있다. All tested Korean populations of the diamondback moth, Plutella xylostella, are known to be resistant especially against pyrethroid insecticides by mutation in its molecular target, para-sodium channel. Moreover, P. xylostella is able to develop resistance against most commercial insecticides. This study was performed to develop an efficient control technique against P. xylostella by a combined treatment of an endoparasitoid wasp, Cotesia plutellae, and a microbial insecticide, Bacillus thuringiensis. To investigate any parasitism preference of C. plutellae against susceptible and resistant P. xylostella, five different populations of P. xylostella were compared in insecticide susceptibilities and parasitism by C. plutellae. These five P. xylostella populations showed a significant variation against three commercial insecticides including pyrethroid, organophosphate, neonicotinoid, and insect growth regulator. However, there were no significant differences among five P. xylostella populations in their parasitic rates by C. plutellae. Moreover, parasitized larvae of P. xylostella showed significantly higher susceptibility to B. thuringiensis. As an immunosuppressive agent, viral ankyrin genes (vankyrins) encoded in C. plutellae were transiently expressed in nonparasitized larvae. Expression of vankyrins significantly enhanced the efficacy of B. thuringiensis against the third instar larvae of P. xylostella. Thus an immunosuppression induced by C. plutellae enhanced the insecticidal efficacy of B. thuringiensis. These results suggest that a combined treatment of C. plutellae and B. thuringiensis may effectively control the insecticide-resistant populations of P. xylostella.

Parasitic wasp females are attracted to blends of host-induced plant volatiles: do qualitative and quantitative differences in the blend matter?

Na&iuml;ve Cotesia vestalis wasps, parasitoids of diamondback moth (DBM) larvae, are attracted to a synthetic blend (Blend A) of host-induced plant volatiles composed of sabinene, n -heptanal, α-pinene, and ( Z )-3-hexenyl acetate, in a ratio of 1.8:1.3:2.0:3.0. We studied whether qualitative (adding ( R )-limonene: Blend B) or quantitative changes (changing ratios: Blend C) to Blend A affected the olfactory response of C. vestalis in the background of intact komatsuna plant volatiles. Na&iuml;ve wasps showed equal preference to Blends A and B and Blends A and C in two-choice tests. Wasps with oviposition experience in the presence of Blend B preferred Blend B over Blend A, while wasps that had oviposited without a volatile blend showed no preference between the two. Likewise, wasps that had starvation experience in the presence of Blend B preferred Blend A over Blend B, while wasps that had starved without a volatile blend showed no preference between the two. Wasps that had oviposition experience either with or without Blend A showed equal preferences between Blends C and A. However, wasps that had starvation experience in the presence of Blend A preferred Blend C over Blend A, while those that starved without a volatile blend showed equal preferences between the two. By manipulating quality and quantity of the synthetic attractants, we showed to what extent C. vestalis could discriminate/learn slight differences between blends that were all, in principle, attractive.

Parasitic wasp females are attracted to blends of host-induced plant volatiles: do qualitative and quantitative differences in the blend matter?

Na&iuml;ve Cotesia vestalis wasps, parasitoids of diamondback moth (DBM) larvae, are attracted to a synthetic blend (Blend A) of host-induced plant volatiles composed of sabinene, n -heptanal, α-pinene, and ( Z )-3-hexenyl acetate, in a ratio of 1.8:1.3:2.0:3.0. We studied whether qualitative (adding ( R )-limonene: Blend B) or quantitative changes (changing ratios: Blend C) to Blend A affected the olfactory response of C. vestalis in the background of intact komatsuna plant volatiles. Na&iuml;ve wasps showed equal preference to Blends A and B and Blends A and C in two-choice tests. Wasps with oviposition experience in the presence of Blend B preferred Blend B over Blend A, while wasps that had oviposited without a volatile blend showed no preference between the two. Likewise, wasps that had starvation experience in the presence of Blend B preferred Blend A over Blend B, while wasps that had starved without a volatile blend showed no preference between the two. Wasps that had oviposition experience either with or without Blend A showed equal preferences between Blends C and A. However, wasps that had starvation experience in the presence of Blend A preferred Blend C over Blend A, while those that starved without a volatile blend showed equal preferences between the two. By manipulating quality and quantity of the synthetic attractants, we showed to what extent C. vestalis could discriminate/learn slight differences between blends that were all, in principle, attractive.