Benoit Graillot, Christine Blachere-López, Samantha Besse, Myriam Siegwart, Miguel López-Ferber
To test the importance of the host genotype in maintaining virus genetic diversity, five experimental populations were constructed by mixing two granulovirus isolates, the Mexican isolate CpGV-M and the CpGV-R5, in ratios of 99% M + 1% R, 95% M + 5% R, 90% M + 10% R, 50% M + 50% R, and 10% M + 90% R. CpGV-M and CpGV-R5 differ in their ability to replicate in codling moth larvae carrying the type I resistance. This ability is associated with a genetic marker located in the virus gene. Six successive cycles of replication were carried out with each virus population on a fully-permissive codling moth colony (CpNPP), as well as on a host colony (R) that carries the type I resistance, and thus blocks CpGV-M replication. The infectivity of offspring viruses was tested on both hosts. Replication on the CpNPP leads to virus lineages preserving the markers characteristic of both isolates, while replication on the R colony drastically reduces the frequency of the CpGV-M marker. Virus progeny obtained after replication on CpNPP show consistently higher pathogenicity than that of progeny viruses obtained by replication on R, independently of the host used for testing.
