| 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. |
