Bibliography: leaves 109-126.

Thesis (Ph. D.)--University of Adelaide, Dept. of Crop Protection, 1997. / Includes bibliographical references (leaves 109-126).

Thesis (Ph.D.)--University of Adelaide, Dept. of Applied & Molecular Ecology, 2002. / Bibliography: leaves 133-148.

Bibliography: leaves 109-126. / xii, 126, [44] leaves, [34] leaves of plates : ill. (chiefly col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Crop Protection, 1997

Title page, table of contents and abstract only. The complete thesis in print form is available from the University of Adelaide Library. / The hymenopteran endoparasitoid, Cotesia rubecula, employs integrated forms of active and passive immune-suppression in overcoming the defences of its host, Pieris rapae, a cosmopolitan pest of cruciferous crops. The immune-suppressive activity arises from a complex of maternally secreted proteins and polydnavirus (PDV) particles, which are injected in a host larva with the parasitoid egg at oviposition. The PDV associated with C. rubecula (CrBV) is unusual in that only four main viral genes (CrV1-CrV4) are expressed in P. rapae tissues and that expression is transient, remaining at high levels only in the period between four and eight hours postparasitisation (hpp). Previously, CrV1 was characterised and found to inactivate host haemocytes by causing disruption of their cytoskeleton, leading to abrogation of immune-associated processes such as spreading. In this study, a cDNA library was constructed from parasitised P. rapae larvae and screened with total CrBV DNA, leading to isolation of CrV2 and CrV3. The open reading frame of each gene was cloned in a bacterial expression vector and the resultant recombinant proteins were used to produce antibodies against CrV2 and CrV3. CrV2 has an open reading frame of 960 bp (with no introns) and encodes a glycoprotein of = 40 kDa, which is secreted from infected haemocytes and fat body. Comparison of CrV2 deduced amino acid sequence with other known sequences revealed no significant homologies. CrV2 protein was detected in host larvae at 6 hpp, remaining in large amounts for at least a day and was declining by 48 hpp. A putative coiled-coil region at the C-terminus of CrV2 is suspected of involvement in formation of CrV2 trimers that were detected under non-denaturing conditions. CrV2 was visualised within haemocytes in large endosomes at 24 hpp. Although the function of CrV2 remains unclear, it appears to interact with host haemocytes presumably to suppress their immune function. The CrV3 gene contained and intron and was found to encode a C-type lectin (CTL) homologue, which is secreted from infected host haemocytes and fat body into haemolymph. Two CrV3 monomers (of = 14 and 17 kDa) were detected in parasitised larvae with the larger monomer being an N-glycosylated form of the smaller monomer. CrV3 dimers and tetramers were also detected in vivo. Recombinant CrV3 forms larger complexes and was shown to agglutinate ovine blood cells, an activity that was Mn²⁺- and Mg²⁺-dependent but was independent of Ca²⁺. CrV3-mediated hemagglutination was inhibited by EDTA but not biological concentrations of 29 potential ligands tested. Interestingly, CrV3 is similar to invertebrate CTLs associated with humoral defence but not with previously isolated viral lectins. Further, CrV3 homologues were recently detected in bracoviruses from C. ruficrus and C. karyai, indicating that a novel CTL family is expressed by some Cotesia-associated PDVs CrV3 probably interacts with a soluble host haemolymph component associated with host humoral immune defences. CrVl and Crp32 (an immune-suppressive C. rubecula calyx protein) were used to produce recombinant Autographa californica mutiple nucleopolyhedrosis viruses (AcMNPVs), pathogens with putatively enhanced virulence in P. rapae. Bioassays were undertaken to investigate the pathogencity of wild-type AcMNPV iu P. rapae (previously unreported) and the effect of insertion of Crp32. Although the proportion of larval deaths due to wild-type AcMNPV was significant, the slow rate of mortality indicated that P. rapae is only semi-permissive to AcMNPV. Crp32 insertion proved insignificant in terms of the proportion and rate of larval mortality. Given the semi-permissive nature of P. rapae, recombinant AcMNPVs expressing immune-suppressive and appropriate reporter genes may be useful for elucidating mechanisms of insect immunity and more specifically, how CrBV acts to subvert these mechanisms in P. rapae. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1109473 / Thesis (Ph.D.) -- University of Adelaide, School of Agriculture and Wine, 2004

Title page, table of contents and abstract only. The complete thesis in print form is available from the University of Adelaide Library. / The hymenopteran endoparasitoid, Cotesia rubecula, employs integrated forms of active and passive immune-suppression in overcoming the defences of its host, Pieris rapae, a cosmopolitan pest of cruciferous crops. The immune-suppressive activity arises from a complex of maternally secreted proteins and polydnavirus (PDV) particles, which are injected in a host larva with the parasitoid egg at oviposition. The PDV associated with C. rubecula (CrBV) is unusual in that only four main viral genes (CrV1-CrV4) are expressed in P. rapae tissues and that expression is transient, remaining at high levels only in the period between four and eight hours postparasitisation (hpp). Previously, CrV1 was characterised and found to inactivate host haemocytes by causing disruption of their cytoskeleton, leading to abrogation of immune-associated processes such as spreading. In this study, a cDNA library was constructed from parasitised P. rapae larvae and screened with total CrBV DNA, leading to isolation of CrV2 and CrV3. The open reading frame of each gene was cloned in a bacterial expression vector and the resultant recombinant proteins were used to produce antibodies against CrV2 and CrV3. CrV2 has an open reading frame of 960 bp (with no introns) and encodes a glycoprotein of = 40 kDa, which is secreted from infected haemocytes and fat body. Comparison of CrV2 deduced amino acid sequence with other known sequences revealed no significant homologies. CrV2 protein was detected in host larvae at 6 hpp, remaining in large amounts for at least a day and was declining by 48 hpp. A putative coiled-coil region at the C-terminus of CrV2 is suspected of involvement in formation of CrV2 trimers that were detected under non-denaturing conditions. CrV2 was visualised within haemocytes in large endosomes at 24 hpp. Although the function of CrV2 remains unclear, it appears to interact with host haemocytes presumably to suppress their immune function. The CrV3 gene contained and intron and was found to encode a C-type lectin (CTL) homologue, which is secreted from infected host haemocytes and fat body into haemolymph. Two CrV3 monomers (of = 14 and 17 kDa) were detected in parasitised larvae with the larger monomer being an N-glycosylated form of the smaller monomer. CrV3 dimers and tetramers were also detected in vivo. Recombinant CrV3 forms larger complexes and was shown to agglutinate ovine blood cells, an activity that was Mn²⁺- and Mg²⁺-dependent but was independent of Ca²⁺. CrV3-mediated hemagglutination was inhibited by EDTA but not biological concentrations of 29 potential ligands tested. Interestingly, CrV3 is similar to invertebrate CTLs associated with humoral defence but not with previously isolated viral lectins. Further, CrV3 homologues were recently detected in bracoviruses from C. ruficrus and C. karyai, indicating that a novel CTL family is expressed by some Cotesia-associated PDVs CrV3 probably interacts with a soluble host haemolymph component associated with host humoral immune defences. CrVl and Crp32 (an immune-suppressive C. rubecula calyx protein) were used to produce recombinant Autographa californica mutiple nucleopolyhedrosis viruses (AcMNPVs), pathogens with putatively enhanced virulence in P. rapae. Bioassays were undertaken to investigate the pathogencity of wild-type AcMNPV iu P. rapae (previously unreported) and the effect of insertion of Crp32. Although the proportion of larval deaths due to wild-type AcMNPV was significant, the slow rate of mortality indicated that P. rapae is only semi-permissive to AcMNPV. Crp32 insertion proved insignificant in terms of the proportion and rate of larval mortality. Given the semi-permissive nature of P. rapae, recombinant AcMNPVs expressing immune-suppressive and appropriate reporter genes may be useful for elucidating mechanisms of insect immunity and more specifically, how CrBV acts to subvert these mechanisms in P. rapae. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1109473 / Thesis (Ph.D.) -- University of Adelaide, School of Agriculture and Wine, 2004

Bibliography: leaves 133-148. Examines sugar foraging in the field by adult female parasitoid wasp, Cotesia rubecula (Hymenoptera, Braconidae), to determine its effect on fecundity and lifespan. In the field, the area in which wasps search for sugar is likely to depend on the degree of association of hosts with nectar or honeydew, supporting the hypothesis that sugar encounters in the field happen opportunistically during host foraging activities. The survival gained by sugar feeding my often be severely limited by quality and quantity of sugary food and extrinsic mortality factors such as adverse weather conditions and predation, so the need for food must be studied in relation to a species' adaptation to its environment. Concentrations of sugar sources may distract wasps from host-foraging when the density of hosts is low. This has implications for flower propagation in agro-ecosystems with a view to supporting natural enemies of insect pests.

Bibliography: leaves 133-148. / xii, 148 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Examines sugar foraging in the field by adult female parasitoid wasp, Cotesia rubecula (Hymenoptera, Braconidae), to determine its effect on fecundity and lifespan. In the field, the area in which wasps search for sugar is likely to depend on the degree of association of hosts with nectar or honeydew, supporting the hypothesis that sugar encounters in the field happen opportunistically during host foraging activities. The survival gained by sugar feeding my often be severely limited by quality and quantity of sugary food and extrinsic mortality factors such as adverse weather conditions and predation, so the need for food must be studied in relation to a species' adaptation to its environment. Concentrations of sugar sources may distract wasps from host-foraging when the density of hosts is low. This has implications for flower propagation in agro-ecosystems with a view to supporting natural enemies of insect pests. / Thesis (Ph.D.)--University of Adelaide, Dept. of Applied & Molecular Ecology, 2002

Bibliography: leaves 133-148. / xii, 148 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Examines sugar foraging in the field by adult female parasitoid wasp, Cotesia rubecula (Hymenoptera, Braconidae), to determine its effect on fecundity and lifespan. In the field, the area in which wasps search for sugar is likely to depend on the degree of association of hosts with nectar or honeydew, supporting the hypothesis that sugar encounters in the field happen opportunistically during host foraging activities. The survival gained by sugar feeding my often be severely limited by quality and quantity of sugary food and extrinsic mortality factors such as adverse weather conditions and predation, so the need for food must be studied in relation to a species' adaptation to its environment. Concentrations of sugar sources may distract wasps from host-foraging when the density of hosts is low. This has implications for flower propagation in agro-ecosystems with a view to supporting natural enemies of insect pests. / Thesis (Ph.D.)--University of Adelaide, Dept. of Applied & Molecular Ecology, 2002

Conura torvina (Cresson) (Hymenoptera: Chalcididae) is a solitary pupal endoparasite of numerous insect species. In Brassica crops it acts as a parasite of Plutella xylostella (L.) (Lepidoptera: Plutellidae) and was found as a hyperparasite of Cotesia rubecula (Marshall) (Hymenoptera: Braconidae) and several other parasitoid species. Cotesia rubecula was introduced into Virginia in 1987 as a biological control agent for Pieris rapae (L.) (Lepidoptera: Pieridae), and because C. torvina was thought to have eliminated this population of C. rubecula, studies of C. torvina's reproductive biology and behavior were initiated. A study using plants laden with "trap hosts" to detect C. torvina activity in the spring indicated no activity until late June, but proved trap host sampling to be an efficient and effective method of monitoring C. torvina activity. Studies of C. torvina's ability to reproduce in C. rubecula pupae of different ages indicated that C. torvina can successfully parasitize pupae at all stages of development, but was most successful in young to middle aged pupae. Studies of C. torvina's host species preference indicated the larger host species such as P. xylostella were preferred. Equal numbers of P. xylostella and C. rubecula were parasitized, but a greater proportion of fertile eggs were laid in P. xylostella. Smaller host species were often ignored. Host dissection studies indicated that caged C. torvina were inefficient at host finding and oviposition. Superparasitism was common, but declined as the females gained oviposition experience. Experienced C. torvina produced an average of 8.25 progenies per day for a period of 12 days when provided with 13 P. xylostella hosts each day. Conura torvina produced up to 14 progenies a day when provided 3 26 hosts. Dissection of C. torvina ovaries indicated three ovarioles per ovary with a mean of 9.2 and maximum of 15 mature eggs per female. Host dissection indicated that a mean of 18 and maximum of 30 eggs could be laid per day. New eggs were produced as oviposition occurred. Significantly larger eggs were laid in P. xylostella than in C. rubecula, and significantly more eggs were laid in C. rubecula than in P. xylostella. From these data and data from earlier studies I concluded that C. torvina has a poor reproductive ability and its impact as a hyperparasite is limited to the summer months. This makes C. torvina an unlikely cause of C. rubecula's disappearance. / Ph. D.