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      Molecular markers for lygus parasitoids to assess host specificity of candidate entomophagous biological control agents

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      GariepyETDrev.pdf (4.560Mb)
      Date
      2007-04-24
      Author
      Gariepy, Tara Dawne
      Type
      Thesis
      Degree Level
      Doctoral
      Metadata
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      Abstract
      Lygus Hahn (Hemiptera: Miridae) are serious pests of economically important field, fruit, vegetable, and greenhouse crops in Canada. The release of European Peristenus Förster (Hymenoptera: Braconidae) in the USA has resulted in significant suppression of this pest and has renewed interest in the release of European Peristenus spp. in Canada. Prior to the release of exotic Peristenus spp., ecological host range studies need to be conducted to define their habitat and host associations. These associations can be difficult to study using conventional methods. Morphological similarity of related parasitoids prevents species-level identification by dissection. Host rearing is time-consuming and can result in high levels of host and parasitoid mortality. To facilitate identification of immature Peristenus spp. in their hosts, a multiplex PCR assay was developed. This assay provided a specific and sensitive tool to screen individual insects for three parasitoid species simultaneously. To validate the utility of the multiplex PCR assay in ecological host range studies, parasitism and parasitoid species composition obtained using conventional and molecular techniques were compared. Molecular methods compared favorably with conventional methods; however, more complete species composition information was available with the multiplex assay. To improve the quality of risk assessment studies and extract the most accurate ecological host range data, molecular methods were used to evaluate host-parasitoid associations in mirid populations collected in two ecoregions. Several new host-parasitoid associations were recorded for P. digoneutis and P. relictus, but parasitism of non-target mirids was low. Parasitism of the target host collected from different plant species was evaluated to help clarify Peristenus – host-plant associations. Despite the investigation of three different host plant species, no difference was observed in the parasitism level or parasitoid species composition in L. rugulipennis. The post-release utility of the multiplex assay was investigated in Canada, where Lygus parasitoids may have dispersed following release in the USA. To confirm establishment, samples were analyzed using the multiplex PCR assay, and P. digoneutis was detected for the first time in southern Ontario.
      Degree
      Doctor of Philosophy (Ph.D.)
      Department
      Biology
      Program
      Biology
      Supervisor
      Gillott, Cedric; Erlandson, Martin
      Committee
      Kuhlmann, Ulrich; Davis, Arthur R.; Messier, François
      Copyright Date
      April 2007
      URI
      http://hdl.handle.net/10388/etd-04132007-115125
      Subject
      molecular diagnostics
      biological control
      multiplex PCR
      Peristenus
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