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Bertha armyworm, Mamestra configurata (Lepidoptera: Noctuidae), is an important pest of cruciferous oilseed crops in western Canada. A nuclear polyhedrosis virus, MacoNPV, isolated from M. configurata, has demonstrated as high as 95% infection in field populations of bertha armyworm. MacoNPV isolates from different geographic areas differ in terms of their virulence to bertha armyworm. Restriction endonuclease (REN) fragment analyses show that all of the geographic isolates are closely related viruses but with some distinct REN pattern differences. Most of these geographic isolates are heterogenous mixtures of genotypes. The thesis describes the cloning and physical mapping of the 156.9 kbp genome of the MacoNPV-90/2 geographic isolate, including 112 restriction sites for six common REN, BamHI, EcoRI, HindIII, PstI, SmaI and XhoI. Twenty plaque purified strains of MacoNPV were isolated in a cultured Mamestra brassicae (Mbr) insect cell line. The EcoRI restriction patterns of these pick plaque (pp) strains fell into 10 different categories. In order to investigate the difference among these pp strains, and between these strains and the parental geographic isolates in terms of REN patterns, virulence to insect hosts, and their growth rates in insect cell lines, some of these isolates were selected for bioassays in bertha armyworm larvae and in the Mbr cell line.

Lot of attention is paid to biological control agents of plant pathogens as it will reduce the amount of pesticides used in agriculture. Pythium oligandrum oomycete is already used commercially in the form of watering and spraying. In this work the properties of other isolates were characterized, and the metabolic changes were studied in plants of oilseed rape (Brassica napus subsp. Oleifera), whose seeds were treated with preparates based on Pythium oligandrum. In the first part of the thesis the properties of compounds secreted by isolates of Pythium oligandrum were tested. The amount of phenolic substances and the activity of endoglycosidase endo-β-1,3-glucanase, cellulase, chitinase as well as proteases were measured to assess the ability of oomycete Pythium oligandrum mycoparasitically protect the plant. Substances, especially oligandrin, which during interaction with the plant are responsible for "priming", have been observed, enabling the plant to respond rapidly to pathogen infection through systemic plant resistance. Differences between individual isolates also manifested themselves in electrophoretic separation in the protein representation. In the second part of the work, the effect of rapeseed seed treatment with isolates of Pythium oligandrum on plant metabolism was monitored. While...

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv. / Härtill 5 uppsatser.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniversitet, 2006. / Härtill 4 uppsatser.