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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Initial frequencies of alleles for resistance to Bacillus thuringiensis toxins in field populations of Plutella xylostella and Helicoverpa armigera

Ahmad, Mahmood. January 1999 (has links) (PDF)
Leaves 101-104 are misnumbered. Bibliography: leaves 155-215. In this study thirteen populations of P. xylostella from crucifer growing areas of Queensland, Victoria, Tasmania, South Australia and Western Australia were surveyed for resistance to Bt (Bacillus thuringiensis) toxins using a leaf-dip bioassay method.
2

Initial frequencies of alleles for resistance to Bacillus thuringiensis toxins in field populations of Plutella xylostella and Helicoverpa armigera / by Mahmood Ahmad.

Ahmad, Mahmood January 1999 (has links)
Leaves 101-104 are misnumbered. / Bibliography: leaves 155-215. / xiii, 215 leaves : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / In this study thirteen populations of P. xylostella from crucifer growing areas of Queensland, Victoria, Tasmania, South Australia and Western Australia were surveyed for resistance to Bt (Bacillus thuringiensis) toxins using a leaf-dip bioassay method. / Thesis (Ph.D.)--University of Adelaide, Dept. of Applied and Molecular Ecology, 2000
3

Initial frequencies of alleles for resistance to Bacillus thuringiensis toxins in field populations of Plutella xylostella and Helicoverpa armigera / by Mahmood Ahmad.

Ahmad, Mahmood January 1999 (has links)
Leaves 101-104 are misnumbered. / Bibliography: leaves 155-215. / xiii, 215 leaves : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / In this study thirteen populations of P. xylostella from crucifer growing areas of Queensland, Victoria, Tasmania, South Australia and Western Australia were surveyed for resistance to Bt (Bacillus thuringiensis) toxins using a leaf-dip bioassay method. / Thesis (Ph.D.)--University of Adelaide, Dept. of Applied and Molecular Ecology, 2000
4

Biological control of turfgrass pests by fungal endophytes /

Nobel, Jennifer 01 January 1992 (has links)
No description available.
5

Enhancement of biological control with beneficial insectary plantings

Colley, Micaela Ruth 30 March 1998 (has links)
Five field experiments were conducted to evaluate the relative attractiveness of potential beneficial insectary plants to aphidophagous hover flies and parasitic Hymenoptera and the effectiveness of interplanting selected flowering plants in a broccoli field to enhance biocontrol of the cabbage aphid and green peach aphid. In 1996 we established a preliminary screening trial to begin development of our sampling methods and evaluations of the attractiveness of selected flowering plants to hover flies and parasitic Hymenoptera. In 1997, we conducted a field experiment at the Oregon State University Vegetable Research Farm near Corvallis, OR to assess the relative attractiveness of 11 selected flowering plants to hover flies and parasitic Hymenoptera. Six of these plants were also evaluated for attractiveness to aphidophagous hover flies in two on-farm trials. The experimental design was a complete randomized block design, with four replications at the OSU site, and three replications at the two on-farm sites. Attractiveness of flowering plants to hover flies was assessed by conducting weekly timed observations of feeding frequencies. Associations of parasitic Hymenoptera were assessed by weekly timed vacuum sampling from a fixed area in plots of flowering plants. Attractiveness differed by dates and sites. Among early-season flowering species, Coriandrum sativa (cilantro) was highly attractive to aphidophagous hover flies and Brassica juncea (mustard), Fagopyrum esculentum (buckwheat) and Agastache rugosa (Korean licorice mint) were most attractive to parasitic Hymenoptera. Among late-season flowers, Achillea millefolium (yarrow), Foeniculum vulgare (fennel) and Agastache rugosa (Korean licorice mint) were most attractive to hover flies, but attractiveness to parasitic Hymenoptera did not differ. An on-farm trial was conducted in 1997 at Stahlbush Island Farm near Corvallis, OR. The objective of this trial was to test the hypothesis that interplanting either alyssum (Lobularia maritima), or cilantro (Coriandrum sativa), with broccoli (Brassica oleracea) would attract aphidophagous hover fly adults and parasitic Hymenoptera, enhance oviposition in the adjacent crop, and increase larval predation and parasitism in the adjacent crop, resulting in suppressed cabbage aphid (Brevicoryne brassicae) and green peach aphid (Myzus persicae) populations in the broccoli crop. The predominate hover fly species present were Toxomerus occidentalis and T. marginatus. More adult female T. occidentalis were caught in pan traps in plots with alyssum than in cilantro or control plots. More hover fly eggs were found on broccoli leaves and a higher percent of the aphids present were parasitized by Hymenoptera in plots with alyssum than in cilantro or control plots. However, no differences in aphid intensities were found between treatment and control plots. A comparison between the mean number of hover fly eggs found per broccoli leaf and the mean number of aphid counted per broccoli leaf suggests there is an association between the two. There appears to be an aphid density threshold below which few hover fly eggs are laid. Gravid females were present in the crop from the first sampling date on, yet hover fly eggs were not found in the crop until the second to last sampling date. Our results indicate that the presence of alyssum enhanced hover fly activity, but did not result in increased larval predation on aphids in the crop. In 1997 a survey of hover flies was conducted at each of the four experimental sites. Hover flies were captured with sweep nets. Representative specimens were identified to species by Christian Kassebeer, University of Kiel, Germany and subsequent identifications were made from reference specimens and with taxonomic keys. Twenty species were identified, 16 of which are aphidophagous. At the OSU site and the two on-farm sites, where the relative attractiveness of flowering plants was assessed, the six most common aphidophagous species, collected at all three sites, were: Meliscaeva cinctella, Toxomerus marginatus, T. occidentalis, Sphaerophoria sulphuripes, S. pyrrhina, and Scaeva pyrastri. / Graduation date: 1998
6

Effects of temperature on the egg-larval parasitoid, Chelonus insularis (Hymenoptera: Braconidae)

Glogoza, Phillip Andrew January 1981 (has links)
No description available.
7

Genomics of entomopathogenic bacterial endosymbiont species associated with desiccation tolerant entomopathogenic nematode

Mothupi, Boipelo January 2016 (has links)
A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science. Year: 2016. / Entomopathogenic nematodes in the genera Heterorhabditis and Steinernema have emerged excellent as non-chemical alternatives for control of insect pest population. They have a specific mutualistic symbioses with bacterial symbionts in the genera Photorhabdus and Xenorhabdus, respectively. Native EPN species that are able to tolerate environmental stress including desiccation are of great interest for application. The aim of this study was to isolate indigenous EPN species from soil samples collected from Brits, North West province in South Africa, and to investigate their ability to tolerate desiccation stress. The second aim was to isolate the bacterial symbiont and sequence, assemble and annotate its whole genomic DNA. Insect baiting technique and White trap method proved useful in the recovery of nematodes from collected soil samples and infected cadaver, respectively. Molecular identification based on the amplification of the 18S rDNA and phylogenetic relationships revealed high affinity of the unknown EPN isolate 10 to Steinernema species and due to variation in evolutionary divergence distance, the unknown isolate was identified as Steinernema spp. isolate 10 . Isolates 35 and 42 revealed high similarity to Heterorhabditis zealandica strain Bartow (accession number: GU174009.1), Heterorhabditis zealandica strain NZH3 (accession number: EF530041.1) and the South African isolate Heterorhabditis zealandica strain SF41 (EU699436.1). Both Steinernema spp. isolate 10 and Heterorhabditis species could tolerate desiccation. Steinernema spp. isolate 10 was tolerant up to 11 days of desiccation exposure in loamy sand and up to 9 days of exposure in river sand, causing 26, 6% and 13, 4% cumulative larval mortality after 96 hours, post resuscitation by rehydration, respectively. Heterorhabditis spp. could tolerate desiccation up to 13 days of exposure and induced 26.6% cumulative larval mortality on both loamy and river sand after 96 hours post resuscitation. Swarming, aggregation, coiling and clumping behavioural characteristics were observed when Steinernema spp. isolate 10 was exposed to desiccation and Heterorhabditis species displayed no similar behavioural characteristics associated with desiccation tolerance. Morphological characteristics of the unknown Steinernema spp. isolate 10 have been described, and the thick cuticle and sheath which are both associated with tolerance to desiccation stress have been noted. The bacterial symbiont was isolated from larval hosts infected with Steinernema spp. isolate 10 and molecular identification through NCBI Blastn based on the 16S rDNA revealed high affinity to Xenorhabdus bacterial species. Phylogenetic relationships and evolutionary divergence estimates 16 revealed genetic variation and the species was identified as Xenorhabdus bacterial isolate. The genome assembly of Xenorhabdus bacterial isolate using CLC Bio revealed a total length of 4, 183, 779 bp with 231 contigs (>=400bp), GC content of 44.7% and N50 of 57,901 bp. Annotation of the assembled genome through NCBI PGAAP annotation pipeline revealed 3,950 genes (3,601 protein coding sequences (CDS) and 266 pseudogenes), 12 rRNAs and 70 tRNAs. RAST annotation revealed 55 of virulence, disease and defense subsystem features which are involved in the pathogenicity of Xenorhabdus bacterial isolate. The ability of EPNs to tolerate environmental stress is highly crucial and one of the determining factors for biocontrol potential and successful application, thus the indigenous desiccation tolerant EPN isolate, Steinernema spp. isolate 10 holds great potential as a biological control agent. The genome sequencing and annotation reveals insight to behavioural and physiological attributes of bacterial symbionts and this study will contribute to the understanding of pathogenicity and evolution of the bacteria–nematode complex. / GR 2016
8

Cloning of genes encoding larvicidal proteins from Bacillus thuringiensis subsp. israelensis into the cyanobacterial hybrid vector, pTNTV

Helvering, Leah M. January 1989 (has links)
Bacillus thuringiensis subsp. isrealensis (B.t.i.) produces a crystalline endotoxin specific for some larvae of mosquitoes that are vectors of the malaria parasite and other infectious diseases. Fragments were obtained from the 108 kb plasmid from B.t.i. strain 4Q2 which encodes several proteins comprising the delta-endotoxin. These DNA fragments were inserted into the hybrid cyanobacterial cloning vector, pTNTV, downstream from its powerful lambda promoter, and the chimaeras were transformed into Escherichia coli. Ampicillin resistant transformants were screened with radioactively labelled oligonucleotides whose sequences were determined from the published sequences of the B.t.i. 130 kDa polypeptide. Clones showing hybridization were used in bioassays to determine their level of toxicity to the fourth instar larvae of the Aedes aegypti mosquito. Twelve clones were found that demonstrated toxicity which was statistically significantly greater than that observed in controls. Plasmid DNA from some of these clones was isolated, cut with restriction endonucleases, and viewed through agarose gel electrophoresis to confirm that B.t.i. fragments had been inserted into the vector. Future work will investigate the expression of these cloned toxin genes in transformable cyanobacteria and will determine their subsequent activity against the fourth instar larvae of Aedes aegypti and Anopheles quadrimaculatus. / Department of Biology
9

Collection and evaluation of bacteria for the biological control of late blight of celery : (Septoria apiicola Speg.)

Lovering, Nancy January 1995 (has links)
Late blight, caused by Septoria apiicola Speg., is the most important disease affecting celery in Quebec. Biological control was investigated as an alternative to conventional chemical control of late blight. Two hundred and four bacterial isolates were collected from celery leaves, and muck and mineral soils of celery fields in south-western Quebec. Two experiments were conducted to screen the bacteria for antagonism toward Septoria apiicola: one on agar to test for inhibition of pycnidial formation, and the other on leaf disks to test for inhibition of germination of conidia. From these two experiments, 18 isolates were selected that prevented pycnidial formation in an inhibition zone $ ge$1.0 cm wide and reduced germination to below 30% of the control. These isolates were re-evaluated for inhibition of germination on leaf disks. A bacterial suspension (10$ sp7$ cells/ml) was incubated on leaf disks for 24 hours before a suspension of S. apiicola conidia (150,000 spores/ml) was applied, and the disks were incubated for 25 hours. Four isolates reduced germination to $ le$19% of the control. These isolates were tested on plants in a greenhouse. None of the isolates was able to reduce the number of late blight lesions compared to the control.
10

Factors influencing the efficiency of two parasitoids of the potato tuber moth (PTM) / by Latif Salehi.

Salehi, Latif January 1998 (has links)
Bibliography: leaves 233-263. / xxix, 263, 14 leaves. / 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, 1999

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