Variability of the progeny of a sequence variant Citrus bent leaf viroid (CBLVd).

A field isolate of CBLVd was previously shown to contain two dominant subpopulations (I and II), which differed by the presence or absence of a Sal I restriction site in the PCR product [10]. Here we demonstrate the infectivity and symptom expression of subpopulation II by inoculating Etrog citron with a single representative haplotype. The resulting progeny was characterised as an heterogeneous population of closely related variants with a new fitness peak represented by an haplotype that was not identified in the original isolate. This demonstrates that CBLVd conforms a "quasispecies" model. The progeny shared features of the two subpopulations of the original isolate indicating that the original isolate probably arose from a single CBLVd ancestor.