Contribution of uneven distribution of genomic RNA variants of citrus tristeza virus (CTV) within the plant to changes in the viral population following aphid transmission

The population of genomic RNA sequence variants of citrus tristeza virus (C TV) isolates was characterized by single-strand conformation polymorphism ( SSCP) analysis of complementary DNA (cDNA) of the genes p18 and p20. Compar ison of field and aphid-transmitted isolates showed that aphid transmission frequently altered the single-strand conformation polymorphism (SSCP) patt ern of both genes, indicating changes in the population of genomic RNA vari ants. SSCP analysis of the cDNA of RNA extracted from small pieces of tissu e sampled at different sites of the same plant sometimes yielded different patterns, indicating uneven distribution of the genomic RNA variants within the infected plant. Different SSCP patterns were also obtained when the RN A extracted from individual aphids probing in the same infected leaf was us ed as a template. Uneven distribution of the genomic RNA variants within th e infected plant and sorting of some of these variants by individual aphids probably contribute to changes observed in the CTV population following ap hid transmission.