Characterisation of two citrus apscaviroids isolated in Spain - Brief report

Sequence variability in the PCR amplified cDNAs from two citrus apscaviroid isolates CVd-Ia and CVd-IIId from Spain, was analysed. CVd-IIId sequence w as shown to be identical to previously described CVd-III sequences and no i mportant variability was encountered within the viroid population. Converse ly, CVd-Ia displayed population heterogeneity as shown by SSCP analysis, Sa l I restriction site polymorphism and sequences of 27 CVd-Ia cloned DNAs. T he CVd-Ia genomic heterogeneity is characterised by two major subpopulation s with the most divergent sequences, and by the presence of individual vari ants, making a sequence continuum between the two major groups. Most sequen ce variations are clustered in the left part of the viroid molecule.