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William A Overholt - One of the best experts on this subject based on the ideXlab platform.
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Physiological suitability of six West African gramineous borers (Lepidoptera: Noctuidae, Pyralidae) for development of Cotesia species complex (Hymenoptera: Braconidae)
International Journal of Tropical Insect Science, 2009Co-Authors: Y. Hailemichael, Fritz Schulthess, J. W. Smith, William A OverholtAbstract:Three gregarious, endoparasitic braconids, a Kenyan strain of Cotesia sesamiae, and the exotic Cotesia flavipes and Cotesia chilonis were imported into Benin as candidates for biological control of stem- and cob borers of maize and stemborers of millet. Host acceptability and host suitability of six gramineous borers occurring in western Africa, the noctuids Sesamia calamistis, Sesamia poephaga, Busseola fusca, the crambid Coniesta ignefusalis, and the pyralids Eldana saccharina and Mussidia nigrivenella, to these parasitoids were evaluated to test the hypothesis that new associations were superior over old association parasitoid-host relationships. All hosts were accepted by all Cotesia spp., except M. nigrivenella, which was not attacked by C. chilonis. Parasitoid progeny developed successfully in S. calamistis, S. poephaga and C. ignefusalis. S. calamistis was the most suitable host in terms of duration of developmental time, brood size and mortality of parasitoid progeny. It was concluded that because of its host specificity, the old association parasitoid C. sesamiae would have the highest chance of establishment in cereal systems in West Africa.
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Resource allocation and bionomics of indigenous and exotic Cotesia (Hymenoptera: Braconidae) species reared on Sesamia calamistis.
Bulletin of Entomological Research, 2008Co-Authors: Y. Hailemichael, William A Overholt, Fritz Schulthess, J.j.w. Smith, A. Chabi-olayeAbstract:The braconid larval parasitoids Cotesia chilonis (Matsumura), C.flavipes Cameron and a strain of Cotesia sesamiae (Cameron) from coastal Kenya, reared at the International Centre of Insect Ecology and Physiology, were introduced at the International Institute of Tropical Agriculture in the Republic of Benin for suitability testing on West African stemborers prior to release. C. chilonis was originally collected in Japan while C. flavipes was imported into Kenya from Pakistan. The host species used was the noctuid Sesamia calamistis (Hampson), the most important noctuid maize pest in the region. All three Cotesia species attacked and successfully developed in 2nd to 6th larval instar of S. calamistis but parasitoid-induced mortality was highest on second instars. On most instars, C. sesamiae and C. flavipes produced larger broods than C. chilonis. Larvae parasitized by C. sesamiae developed to the 6th instar and attained an average larval weight of 353 mg, while larvae parasitized by C. chilonis only molted to the 4th instar and attained a maximum weight of 107 mg. The lower developmental threshold estimated from the non-linear regression of temperature on developmental rate was 15.9, 15.9 and 14.9°C for C. chilonis, C. sesamiae and C. flavipes, respectively, while the maximum temperature was 34.2, 35.2 and 33.8°C, respectively. A maximum of four ovipositions were observed per female during a life span ranging from 1.3 days for C. chilonis and C. flavipes to 1.6 days for C. sesamiae. The largest adult progeny, intrinsic rate of increase and net reproductive rates were recorded at 28°C for all species. However, across temperatures, C. flavipes yielded the highest number of offspring, followed by C. sesamiae and C. chilonis. The sex ratios did not vary significantly with species and temperature. Thus, the reproductive potentials of C. sesamiae and C. flavipes were greater than that of C. chilonis.
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Cotesia flavipes Cameron and Cotesia sesamiae (Cameron) (Hymenoptera : Braconidae) do not exhibit complementary sex determination : Evidence from field populations
Applied Entomology and Zoology, 2004Co-Authors: Emmanuel I. Niyibigira, William A Overholt, Richard StouthamerAbstract:Diploid males are expected to occur in populations of some Hymenoptera because of the single-locus complementary sex determination (sl-CSD) mechanism. If sl-CSD is found in a species that produces gregarious broods and sib mates at a high frequency, a fraction of these sib-matings (matched mating) produces diploid male offspring. We developed models to predict the matched mating frequency in populations with different frequencies of sib mating and egg fertilization. The predictions of these models are used to determine if we can use the distributions of brood sex ratio and brood size to determine if a species has sl-CSD. The models show that sl-CSD can be detected from these brood sex ratios if the diploid male offspring survives. We applied our models to Cotesia sesamiae and its exotic congener Cotesia flavipes (Hymenoptera: Braconidae), to determine if sl-CSD occurs in these species. Parasitoids were reared from stemborer larvae sampled from maize fields in Kenya between 1992 and 1999. We found no evidence for the presence of sl-CSD with survival of diploid males in both braconid species, but we cannot exclude the possibility that sl-CSD with diploid male mortality takes place in these species.
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Near-infrared Spectroscopic Method to Identify Cotesia flavipes and Cotesia sesamiae (Hymenoptera: Braconidae)
Annals of The Entomological Society of America, 2003Co-Authors: T. J. Cole, William A Overholt, C. O. Omwega, Floyd E. Dowell, Sonny B. RamaswamyAbstract:Parasitoids of the Cotesia flavipes complex (C. flavipes and Cotesia sesamiae) are natural enemies of stemboring lepidopteran pests in sub-Saharan Africa. The two species are difÞcult to differentiate using morphological markers, and a quick, reliable test was sought for their correct identiÞcation. After numerous, unsuccessful attempts at developing species-speciÞc monoclonal antibodies that could differentiate between the two species, we were successful in using near-infrared spectroscopy to distinguish the cocoons of the two species with an accuracy of better than 85%. Calibrations were established using partial least squares analysis, enabling identiÞcation of cocoons of known species, cocoons from an alternative host, as well as in blind tests. This technology would greatly expedite identiÞcation of Þeld-caught insects used to determine ecological parameters and parasitization rates of an individual species.
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Intraspecific and Interspecific Competition Between Cotesia flavipes and Cotesia sesamiae (Hymenoptera: Braconidae), Gregarious Larval Endoparasitoids of Lepidopteran Stemborers
Biocontrol Science and Technology, 2002Co-Authors: Mohamed N. Sallam, William A Overholt, Eunice KairuAbstract:Super and multiple parasitism of Chilo partellus (Lepidoptera: Pyralidae) and Sesamia calamistis (Lepidoptera: Noctuidae) by Cotesia flavipes Cameron and Cotesia sesamiae (Cameron) (Hymenoptera: Braconidae) were investigated in the laboratory. Progeny production of Co. flavipes increased as a result of increasing the number of ovipositions, from one to three per one Ch. partellus host larva, then decreased as a result of four and five ovipositions per larva. Cocoon weight, sex ratio and emergence of the parasitoid progeny were not affected by superparasitism. Low progeny production of Co. sesamiae and poor survival of Ch. partellus host larvae were found as a result of superparasitism. When S. calamistis was the host, the duration of immature stages of Co. flavipes , parasitoid emergence, progeny production and sex ratio were not affected by superparasitism, but cocoon weight, adult longevity and the potential fecundity of adult females decreased. Superparasitism of S. calamistis by Co. sesamiae did not a...
Mark R Shaw - One of the best experts on this subject based on the ideXlab platform.
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a review of unusual species of Cotesia hymenoptera braconidae microgastrinae with the first tergite narrowing at midlength
ZooKeys, 2016Co-Authors: Ankita Gupta, Mark R Shaw, Sophie Cardinal, Jose FernandeztrianaAbstract:The unusual species of Cotesia (Hymenoptera, Braconidae, Microgastrinae) with the first tergite narrowing at midlength are reviewed. One new species, Cotesia trabalae sp. n. is described from India and compared with Cotesia pistrinariae (Wilkinson) from Africa, the only other species sharing the same character of all the described species worldwide. The generic placement of these two species, based on molecular and morphological analyses as well as parasitoid biology is discussed.
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First report of Cotesia vanessae (Hymenoptera: Braconidae) in North America
Canadian Entomologist, 2014Co-Authors: Vincent A. D. Hervet, Mark R Shaw, Jose Fernandez-triana, H. Murillo, Robert A. Laird, Kevin D. FloateAbstract:We report for the first time the occurrence of the well-known Eurasian and north African parasitoid Cotesia vanessae (Reinhard) (Hymenoptera: Braconidae) in North America. Specimens were reared from Chrysodeixis chalcites (Esper) and Trichoplusia ni (Hubner) (Lepidoptera: Noctuidae) recovered from several locations in southwestern Ontario, Canada, and detected by DNA sequencing from one Autographa californica (Speyer) (Lepidoptera: Noctuidae) in southern Alberta, Canada. Resume—Nous rapportons pour la premiere fois la presence du parasitoide Cotesia vanessae (Reinhard) (Hymenoptera: Braconidae) en Amerique du Nord. Des specimens ont ete eleves a partir de Chrysodeixis chalcites (Esper) et Trichoplusia ni (Hubner) (Lepidoptera: Noctuidae) collectes a plusieurs localites au sud-est de l'Ontario, Canada, et detecte par une sequence d'ADN provenant d'un Autographa californica (Speyer) (Lepidoptera: Noctuidae) collecte a une localite au sud de l'Alberta, Canada. Ce parasitoide n'a ete reporte auparavant qu'en Europe, Asie et Afrique.
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host specialization by Cotesia wasps hymenoptera braconidae parasitizing species rich melitaeini lepidoptera nymphalidae communities in north eastern spain
Biological Journal of The Linnean Society, 2005Co-Authors: Maaria Kankare, Constanti Stefanescu, Saskya Van Nouhuys, Mark R ShawAbstract:In order to investigate parasitoids of the genus Cotesia (Hymenoptera: Braconidae), larvae of a speciose group of butterflies, the tribe Melitaeini (Lepidoptera: Nymphalidae), were collected from several sites in Catalonia, northern Spain, a region that harbours ten out of the 20 European species of Melitaeini. New information on the natural history of the butterflies is presented, and the structure of their communities and patterns of larval parasitism are described. On the basis of mtDNA sequence data (COI gene), microsatellite data (ten loci) and behavioural experiments, we recognize seven biologically distinct species of Cotesia parasitizing the Melitaeini communities within this relatively small geographical area. In particular, the notional species C. melitaearum and C. acuminata each represents a series of cryptic species with narrow host associations. The possibility of direct competition among the parasitoids and/or indirect interactions between butterflies mediated by Cotesia parasitoids is explored.
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molecular phylogeny of Cotesia cameron 1891 insecta hymenoptera braconidae microgastrinae parasitoids associated with melitaeini butterflies insecta lepidoptera nymphalidae melitaeini
Molecular Phylogenetics and Evolution, 2004Co-Authors: Maaria Kankare, Mark R ShawAbstract:Phylogenetic relationships among Cotesia Cameron (Braconidae) species parasitising Melitaeini butterflies were examined using DNA sequence data (mitochondrial cytochrome oxidase subunit I and NADH1 dehydrogenase genes, nuclear ribosomal DNA internal transcribed spacer region) as well as 12 microsatellite loci. Molecular data were available from ostensibly six species of Cotesia from 16 host butterfly species in Europe, Asia, and North America. Analysis of the combined sequence data using both maximum parsimony and maximum likelihood revealed two distinct Cotesia clades. In one clade (C. acuminata (Reinhard); C. bignellii (Marshall)) host ranges are apparently narrow and, although Euphydryas (s. lato) is well-utilised, permeation of Melitaea (s. lato) has been slight. In the other clade (C. melitaearum (Wilkinson); C. lycophron (Nixon); C. cynthiae (Nixon)) host utilization across the Melitaeini as a whole is more extensive and the data are consistent with more recent, or active, speciation processes. Neighbour-joining trees calculated separately for the two main clades based on chord distance (DCE) of microsatellite allele frequencies were consistent with phylogenetic trees obtained from the sequence data. Our analysis strongly suggests the presence of several additional, previously unrecognised, Cotesia species parasitising this group of butterflies.
Bruno Le Ru - One of the best experts on this subject based on the ideXlab platform.
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ongoing ecological speciation in Cotesia sesamiae a biological control agent of cereal stem borers
Evolutionary Applications, 2015Co-Authors: Bruno Le Ru, Laure Kaiser, Ferial Kaoula, Corentin Paillusson, Claire Capdevielledulac, Julius Obonyo, Elisabeth A Herniou, Severine JancekAbstract:To develop efficient and safe biological control, we need to reliably identify natural enemy species, determine their host range, and understand the mechanisms that drive host range evolution. We investigated these points in Cotesia sesamiae, an African parasitic wasp of cereal stem borers. Phylogenetic analyses of 74 individual wasps, based on six mitochondrial and nuclear genes, revealed three lineages. We then investigated the ecological status (host plant and host insect ranges in the field, and host insect suitability tests) and the biological status (cross-mating tests) of the three lineages. We found that one highly supported lineage showed all the hallmarks of a cryptic species. It is associated with one host insect, Sesamia nonagrioides, and is reproductively isolated from the other two lineages by pre- and postmating barriers. The other two lineages had a more variable phylogenetic support, depending on the set of genes; they exhibited an overlapping and diversified range of host species and are not reproductively isolated from one another. We discuss the ecological conditions and mechanisms that likely generated this ongoing speciation and the relevance of this new specialist taxon in the genus Cotesia for biological control.
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sensilla on antennae ovipositor and tarsi of the larval parasitoids Cotesia sesamiae cameron 1906 and Cotesia flavipes cameron 1891 hymenoptera braconidae a comparative scanning electron microscopy study
Annales De La Societe Entomologique De France, 2011Co-Authors: Meshack Obonyo, Jean-françois Silvain, F Schulthess, M Chimtawi, Gerard Mascarel, Peter Ahuya, Bruno Le Ru, Johann Van Den Berg, Paul-andré CalatayudAbstract:Abstract Two braconid parasitoids of cereal stemborers in eastern Africa, Cotesia sesamiae and Cotesia flavipes, have been shown to display a similar hierarchy of behavioural events during host recognition and acceptance. In order to understand the mechanisms underlying host recognition and acceptance, the morphology of antennal sensilla on the last antennomeres, on the ovipositor, and on the fifth tarsomere and pretarsus of the prothoracic legs tarsi were studied using scanning electron microscopy followed by selective silver nitrate staining. It appeared that female C. sesamiae and C. flavipes shared the same types and distribution of sensory receptors, which enable them to detect volatiles and contact chemical stimuli from their hosts. In both parasitoids, four types of sensilla were identified on the three terminal antennomeres: (i) non-porous sensilla trichodea likely to be involved in mechanoreception, (ii) uniporous sensilla chaetica with porous tips that have gustatory functions, (iii) multiporous...
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importance of contact chemical cues in host recognition and acceptance by the braconid larval endoparasitoids Cotesia sesamiae and Cotesia flavipes
Biological Control, 2010Co-Authors: Jean-françois Silvain, Meshack Obonyo, F Schulthess, Bruno Le Ru, Johnnie Van Den Berg, Paul-andré CalatayudAbstract:The ability of the congeneric braconid parasitoids Cotesia sesamiae (Cameron) and Cotesia flavipes Cameron to discriminate between stemborer larval cues upon contact was studied using their natural hosts, namely the noctuid Busseola fusca (Fuller) and the crambid Chilo partellus (Swinhoe), respectively, and the pyralid non-host Eldana saccharina (Walker). When the natural host larvae were washed in distilled water, parasitoid behavior was similar to that displayed when in contact with E. saccharina, characterized by the absence of ovipositor insertion. When washed host or non-host larvae were bathed with water extracts of their natural host, the parasitoids showed a significant increase in ovipositor insertions. However, the water extracts of host-larvae deposited on cotton wool balls did not induce ovipositor insertion in either C. sesamiae or C. flavipes. Nevertheless, the extracts enabled the parasitoids to discriminate between natural and non-hosts as indicated by the intensive antennating of the former. For both parasitoids, frass was found to be important in short-range host recognition as indicated by differences in the time spent on antennating between frass sources. In addition, the regurgitants of B. fusca and C. partellus induced ovipositor insertion in C. flavipes only. These results indicated that C. sesamiae and C. flavipes used different chemical cues for acceptation and oviposition in a stemborer larva, and that B. fusca and C. partellus shared the same chemical cues to induce oviposition in C. flavipes.
Jean-françois Silvain - One of the best experts on this subject based on the ideXlab platform.
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sensilla on antennae ovipositor and tarsi of the larval parasitoids Cotesia sesamiae cameron 1906 and Cotesia flavipes cameron 1891 hymenoptera braconidae a comparative scanning electron microscopy study
Annales De La Societe Entomologique De France, 2011Co-Authors: Meshack Obonyo, Jean-françois Silvain, F Schulthess, M Chimtawi, Gerard Mascarel, Peter Ahuya, Bruno Le Ru, Johann Van Den Berg, Paul-andré CalatayudAbstract:Abstract Two braconid parasitoids of cereal stemborers in eastern Africa, Cotesia sesamiae and Cotesia flavipes, have been shown to display a similar hierarchy of behavioural events during host recognition and acceptance. In order to understand the mechanisms underlying host recognition and acceptance, the morphology of antennal sensilla on the last antennomeres, on the ovipositor, and on the fifth tarsomere and pretarsus of the prothoracic legs tarsi were studied using scanning electron microscopy followed by selective silver nitrate staining. It appeared that female C. sesamiae and C. flavipes shared the same types and distribution of sensory receptors, which enable them to detect volatiles and contact chemical stimuli from their hosts. In both parasitoids, four types of sensilla were identified on the three terminal antennomeres: (i) non-porous sensilla trichodea likely to be involved in mechanoreception, (ii) uniporous sensilla chaetica with porous tips that have gustatory functions, (iii) multiporous...
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importance of contact chemical cues in host recognition and acceptance by the braconid larval endoparasitoids Cotesia sesamiae and Cotesia flavipes
Biological Control, 2010Co-Authors: Jean-françois Silvain, Meshack Obonyo, F Schulthess, Bruno Le Ru, Johnnie Van Den Berg, Paul-andré CalatayudAbstract:The ability of the congeneric braconid parasitoids Cotesia sesamiae (Cameron) and Cotesia flavipes Cameron to discriminate between stemborer larval cues upon contact was studied using their natural hosts, namely the noctuid Busseola fusca (Fuller) and the crambid Chilo partellus (Swinhoe), respectively, and the pyralid non-host Eldana saccharina (Walker). When the natural host larvae were washed in distilled water, parasitoid behavior was similar to that displayed when in contact with E. saccharina, characterized by the absence of ovipositor insertion. When washed host or non-host larvae were bathed with water extracts of their natural host, the parasitoids showed a significant increase in ovipositor insertions. However, the water extracts of host-larvae deposited on cotton wool balls did not induce ovipositor insertion in either C. sesamiae or C. flavipes. Nevertheless, the extracts enabled the parasitoids to discriminate between natural and non-hosts as indicated by the intensive antennating of the former. For both parasitoids, frass was found to be important in short-range host recognition as indicated by differences in the time spent on antennating between frass sources. In addition, the regurgitants of B. fusca and C. partellus induced ovipositor insertion in C. flavipes only. These results indicated that C. sesamiae and C. flavipes used different chemical cues for acceptation and oviposition in a stemborer larva, and that B. fusca and C. partellus shared the same chemical cues to induce oviposition in C. flavipes.
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Single-step PCR differentiation of Cotesia sesamiae (Cameron) and Cotesia flavipes Cameron (Hymenoptera: Braconidae) using polydnavirus markers
Annales De La Societe Entomologique De France, 2006Co-Authors: Stéphane Dupas, Catherine W. Gitau, Jean-françois SilvainAbstract:Abstract Cotesia sesamiae (Cameron) and Cotesia flavipes Cameron (Hymenoptera: Braconidae) are the main larval parasitoids of cereal stemborers in sub-Saharan Africa. Cotesia sesamiae is endemic to eastern and southern Africa, while C. flavipes was introduced into the region for biological control against the exotic lepidopteran Chilo partellus (Swinhoe) (Lepidoptera: Crambidae). The two are sibling parasitoids, difficult to distinguish morphologically. The introduced insect could potentially lead its African biotype to extinction because of their similar ecological niche. In order to distinguish the two species, multiplex primer-specific and PCR-RFLP tests were developed. Rapid identification of the two species was possible using primer-specific tests on DNA extracts as well as on pieces of tissue in a single PCR step followed by gel electrophoresis. The CRV1 gene of the polydnavirus, a symbiont to the wasps, was used as the marker. The results show that the morphological identifications, validated by mo...
Stéphane Dupas - One of the best experts on this subject based on the ideXlab platform.
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Genetic footprints of adaptive divergence in the bracovirus of Cotesia sesamiae identified by targeted resequencing
Molecular Ecology, 2018Co-Authors: Jérémy Gauthier, Stéphane Dupas, Laure Kaiser, Severine Jancek, Philippe Gayral, Gabor Gyapay, Elisabeth A HerniouAbstract:The African parasitoid wasp Cotesia sesamiae is a generalist species structured in locally adapted populations showing differences in host range. The recent discovery of Cotesia typhae, a specialist, sister species to C. sesamiae, provides a good framework to study the genetic determinants of parasitoid host range. To investigate the genomic bases of divergence between these populations and species, we used a targeted sequencing approach on 24 samples. We targeted the bracovirus genomic region encoding virulence genes involved in the interaction with the lepidopteran hosts of the wasps. High sequencing coverage was obtained for all samples, allowing the study of genetic variation between wasp populations and species. By combining population genetic estimations, such as nucleotide diversity (π), relative differentiation (FST ) and absolute divergence (dxy ), with branch-site dN/dS measures, we identified six of 98 bracovirus genes showing significant divergence and evidence of positive selection. These genes, belonging to different gene families, are potentially involved in host adaptation and in the specialization process. Fine-scale analyses of genetic variation also revealed mutations and large deletions in certain genes inducing pseudogenization and loss of function. The image emerging from these results is that adaptation mediated by bracovirus genes happens through selection of particularly adaptive alleles and loss of nonadaptive genes. These results highlight the central role of the bracovirus in the molecular interactions between the wasps and their hosts and in the evolutionary processes of specialization.
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Variability in the reproductive biology and in resistance against Cotesia sesamiae among two Busseola fusca populations
Journal of Applied Entomology, 2010Co-Authors: Paul-andré Calatayud, Stéphane Dupas, Catherine W. Gitau, Sabine Calatayud, J.-f. SilvainAbstract:Two mitotypes of Busseola fusca (Fuller) (Lepidoptera: Noctuidae) named KI and KII, co-exist in Kenya. Individuals of KII are more widely distributed than those of KI. The present study assessed whether this was due to differences in their reproductive potential and/or in their resistance to the braconid Cotesia sesamiae Cameron, which is the most common larval parasitoid of B. fusca in the region. Two populations of the parasitoid, one from the coastal and one from the inland regions of Kenya, which differ in their ability to develop in B. fusca, were tested. Virgin KII females started to call sooner during the night than KI females. Female fecundity and egg viability were significantly lower for the heterogamous than the homogamous crosses. Cotesia sesamiae from the inland produced larger progeny in KI than in KII host. Cotesia sesamiae from the coast did not develop in either host. Despite their long time co-existence in the same geographical area, KII and KI conserved biological differences in terms of time of calling, fecundity, fertility and resistance against the larval parasitoid, C. sesamiae. This might explain the wider distribution of KII as compared to KI in Kenya.
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Geographic distribution, host range and perennation of Cotesia sesamiae and Cotesia flavipes Cameron in cultivated and natural habitats in Kenya.
Biological Control, 2010Co-Authors: Duna Madu Mailafiya, Eunice Waitherero Kairu, Paul-andré Calatayud, Stéphane DupasAbstract:Abstract Field surveys were carried out in four agroecological zones to assess the geographic distribution, host range and perennation of Cotesia sesamiae and Cotesia flavipes in cultivated and natural habitats in Kenya. The distribution of the two Cotesia species in different ecological regions was most affected by the suitability of the local stem borer species for parasitoid development, and temperature, as both species were found in localities dominated by their suitable host(s) where temperature favoured their occurrence. Fourteen years after its release, C. flavipes has maintained a high level of specificity to its target host Chilo partellus on maize and sorghum in cultivated habitats and on Sorghum arundinaceum in natural habitats. Cotesia flavipes appeared to be an appropriate biological control agent against C. partellus in eastern Africa, with minimal or no effects on non-target hosts in different habitats. Conversely, C. sesamiae lacked host specificity in different habitats, as its stem borers or host plants varied with both locality and habitat type. Perennation by both Cotesia species occurred mainly in cultivated habitats. Furthermore, natural habitats played a role in sustaining some individuals of C. flavipes during both rainy and dry seasons. These areas acted as refuges for C. flavipes, but not for C. sesamiae, because its hosts were scarce on natural host plants. The availability of these Cotesia species across seasons was mainly influenced by the presence of actively feeding stem borers on cereal plants during different seasons, as well as the duration of the dry season in different localities.
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differential expression of the crv1 haemocyte inactivation associated polydnavirus gene in the african maize stem borer busseola fusca fuller parasitized by two biotypes of the endoparasitoid Cotesia sesamiae cameron
Journal of Insect Physiology, 2007Co-Authors: D Gundersenrindal, Catherine Gitau, M Pedroni, P J Mbugi, Stéphane DupasAbstract:Abstract Polydnaviruses are rarely studied for their natural variation in immune suppressive abilities. The polydnavirus harboring braconid Cotesia sesamiae, a widespread endoparasitoid of Busseola fusca and Sesamia calamistis in sub-Saharan Africa exists as two biotypes. In Kenya, the western biotype completes development in B. fusca larvae. However, eggs of the coastal C. sesamiae are encapsulated in this host and ultimately, no parasitoids emerge from parasitized B. fusca larvae. Both biotypes develop successfully in S. calamistis larvae. Encapsulation activity by B. fusca larvae towards eggs of the avirulent C. sesamiae was detectable six hours post-parasitization. The differences in encapsulation of virulent and avirulent strains were associated with differences in nucleotide sequences and expression of a CrV1 polydnavirus (PDV) gene, which is associated with haemocyte inactivation in the Cotesia rubecula/Pieris rapae system. CrV1 expression was faint or absent in fat body and haemolymph samples from B. fusca parasitized by the avirulent C. sesamiae, which exhibited encapsulation of eggs. Expression was high in fat body and haemolymph samples from both B. fusca and S. calamistis larvae parasitized by the virulent C. sesamiae, encapsulation in the former peaking at the same time points as CrV1 expression in the latter. Non synonymous difference in CrV1 gene sequences between virulent and avirulent wasp suggests that variations in B. fusca parasitism by C. sesamiae may be due to qualitative differences in CrV1-haemocyte interactions.
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Single-step PCR differentiation of Cotesia sesamiae (Cameron) and Cotesia flavipes Cameron (Hymenoptera: Braconidae) using polydnavirus markers
Annales De La Societe Entomologique De France, 2006Co-Authors: Stéphane Dupas, Catherine W. Gitau, Jean-françois SilvainAbstract:Abstract Cotesia sesamiae (Cameron) and Cotesia flavipes Cameron (Hymenoptera: Braconidae) are the main larval parasitoids of cereal stemborers in sub-Saharan Africa. Cotesia sesamiae is endemic to eastern and southern Africa, while C. flavipes was introduced into the region for biological control against the exotic lepidopteran Chilo partellus (Swinhoe) (Lepidoptera: Crambidae). The two are sibling parasitoids, difficult to distinguish morphologically. The introduced insect could potentially lead its African biotype to extinction because of their similar ecological niche. In order to distinguish the two species, multiplex primer-specific and PCR-RFLP tests were developed. Rapid identification of the two species was possible using primer-specific tests on DNA extracts as well as on pieces of tissue in a single PCR step followed by gel electrophoresis. The CRV1 gene of the polydnavirus, a symbiont to the wasps, was used as the marker. The results show that the morphological identifications, validated by mo...
