Stability over passages on genotype frequencies and pathogenicity of CpGV mixed genotype populations

Abstract: Cydia pomonella granulovirs isolate R5 is able to replicate in codling moth larvae susceptible or resistant to the Mexican isolate of CpGV. An experimental virus lineage was constructed by mixing 99 % CpGV-R5 and 1 % CpGV-M. This lineage was replicated for 20 passages on susceptible insects at high multiplicity. The relative proportion of CpGV-M in this lineage increases over passages, becoming predominant after the 10th passage. However, this virus lineage retains its ability to replicate on RGV insects, that are resistant to CpGV-M. It has been previously demonstrated that in genotypic mixtures CpGV-R5 acts as helper of CpGV-M for replication on RGV larvae. The increasing proportion of CpGV-M over passages suggest that a previously undetected selective advantage exists for CpGV-M when replicating in epizootic conditions but reveals also that CpGV-R5 does not disappear quickly from the virus population.