Deciphering the genetic and biological plasticity of Cydia pomonella granulovirus (CpGV)

The Cydia pomonella granulovirus (CpGV) is one of the most important biological control agents for codling moth. We performed genome sequencing and phylogenetic analyses of several different CpGV isolates, such as CpGV-M, -I12, -E2, -S, -I07. These analyses showed that the isolates belong to different genome types and differ in single nucleotiude polymorphisms (SNPs) and indel mutation of coding and non-coding genomic regions.10When resistance to CpGV was observed in European orchards, it could be attributed to a single resistance allele which is dominantly inherited on sex-chromosome Z. Several CpGV isolates (CpGV-I12, -S, -E2, MadexPlus) overcome this resistance. From whole genome sequencing, it could be concluded that the observed CpGV resistance is not a resistance in general, but to type A genomes like CpGV-M. Interestingly, a further type of resistance which cannot be overcome by Madex Plus, CpGV-I12 or -S was observed in two German orchards. Crossing experiments between resistant individuals and a susceptible laboratory colony showed that the inheritance of this resistance did not follow the previously described pattern of Z-linked, dominant resistance. The offspring of some crossings was completely resistant to CpGV-M and -S, but in some individuals, CpGV-M caused even higher mortality than the resistance overcoming CpGV-S. On the other hand, another CpGV isolate CpGV-V15 caused high mortality in these populations in both bioassays and in the field. We aim to elucidate this complexity in the interaction of various CpGV and different codling moth population on molecular basis. The molecular mechanisms of interaction of different CpGV isolates in codling moth is of enormous interest in terms of CpGV evolution, and it is of crucial importance for the application of CpGV in the field.