Genotype variation of citrus tristeza virus after passage on different hosts, and changes in the virus genotype populations by the vector Aphis gossypii

Phylogenetic analyses categorize seven genotypes of citrus tristeza virus (CTV). The symptoms caused by this pathogen, their expression and severity are influenced by CTV genotypes, host species, cultivars, and infected host rootstocks. This study aimed to verify how populations of Chilean CTV isolates changed following inoculation from infected sweet orange to Mexican lime trees, and to determine if CTV genotype populations influenced transmission efficiency via Aphis gossypii. Reverse transcription polymerase chain reaction showed variation in genotypes of populations of CTV in Mexican lime, after graft inoculations using infected sweet orange chip-buds. Severe genotypes (VT) were detected after inoculation of mild isolate CTV populations (T30). The T30 donor populations also reduced transmissibility via A. gossypii; however, these results may not be conclusive due to mixture with the VT genotype. There is evidence of high rates of virus acquisition by this aphid species, but also low transmission efficiency, which may partially explain the historical absence of tristeza epidemics in Chile.