The effect of transmission by Aphis gossypii and Aphis spiraecola on Citrus tristeza virus (CTV) population structure was studied by nucleotide sequece analysis of an approximately 500 base pair region in ORF 1a (A region)and a 500 base pair region in the P20 gene. The isolates used were from commercial trees in San Joaquin Valley orchards and subisoalates collected from these trees by aphid transmission. It is compelling that in many of these isolate/aphid species combinations, aphid transmission dramatically narrowed the genetic diversity of the virus population and transmitted genotypes that were not detected in the parent tree. When these subisolates were retested after about one year, the genotype nearly remained stable. These data suggest that aphid transmission serves as a genetic bottleneck for the diverse quasispecies present in CTV populations. Characterization of 30 additional field isolates suggest that a founder effect may occur and these genotypes may then dominate CTV populations.
Species 1: Homoptera Aphididae Aphis gossypii (Melon aphid, Cotton aphid)
Species 2: Homoptera Aphididae Aphis spiraecola (Spirea aphid)
Keywords: virus transmission, founder effect
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