Mixed infections of baculoviruses in insect hosts are quite common in nature. This leads to ‘within-host’ and ‘between-host’ competition between virus variants. Because both levels of selection will contribute to overall biological fitness, both must be included in assessments of the fitness of fast-acting recombinant baculoviruses. We investigated baculovirus fitness parameters in single and mixed infection of insect larvae, in single and serial passage experiments in lepidopteran hosts (Helicoverpa armigera, Spodoptera exiqua and Trichoplusia ni) in laboratory, greenhouse and field settings. Median time to death in third instar larvae of H. armigera (Hübner) was lower in insects challenged with a mixture of wild type (HaSNPV-wt) and mutant (?egt, HaSNPV-LM2) Helicoverpa armigera SNPV, than in larvae infected with only HaSNPV-wt. The results from a behavioral study on cotton (greenhouse, field) indicated that the transmission of HaSNPV-LM2 is not modified by the absence of the egt gene, whereas in the case of the HaSNPV-AaIT (?egt, + AaIT) lower virus yield as well as altered caterpillar behavior could compromise virus fitness. Virus transmission in greenhouse and field was not reduced, when HaSNPV-LM2 was used in mixed infections with HaSNPV-wt. However, a reduction of ‘between host’ transmission was recorded when H. armigera larvae were co-infected with HaSNPV-wt and HaSNPV-AaIT. Serial passage experiments with S. exigua and T. ni showed positive selection for wild type SeMNPV and AcMNPV over genetically modified variants (?egt, + AaIT in the case of SeMNPV, and ?egt in the case of AcMNPV) over passages. These findings can help to understand long-term dynamics of virus genotypes in virus-insect-host plant systems. They can also help foresee potential consequences of the introduction of genetically-modified or exotic baculoviruses in agro-ecosystems.
|Title of host publication||Abstract Book of the 42nd Annual Meeting of the Society for Invertebrate Pathology, Park City, Utah, 16 - 20 August, 2009|
|Place of Publication||Park City, Utah|
|Publication status||Published - 2009|
|Event||42nd Annual Meeting of the Society for Invertebrate Pathology, Park City, Utah - |
Duration: 16 Aug 2009 → 20 Aug 2009
|Conference||42nd Annual Meeting of the Society for Invertebrate Pathology, Park City, Utah|
|Period||16/08/09 → 20/08/09|