The complete genomic RNA sequences of the tymovirus isolates Hu and Col from potato which originally had been considered to be strains of the same virus species, i.e. Andean potato latent virus (APLV), were determined by siRNA sequencing and assembly, and found to share only c. 65% nt sequence identity. This result together with those of serological tests and comparisons of the coat protein gene sequences of additional tymovirus isolates from potato suggest that the species Andean potato latent virus should be subdivided into two species, i.e. APLV and Andean potato mild mosaic virus (APMMV). Primers were designed for the broad specificity detection of both viruses.