Host preference of the major strains of Plum pox virus -Opinions based on regional and world-wide sequence data

Plum pox virus (PPV) causes sharka - the most serious viral disease of stone fruit trees. PPV is wide spread in Europe and Mediterranean Basin, its incidence has been further approved in Asia and both Americas. Nine PPV strains have been recognized until now (PPV-D, PPV-M, PPV-Rec, PPV-EA, PPV-C, PPV-T, PPV-W, PPV-CR, and PPV-An), forming molecularly distinct entities, however, only partially differentiable by their biological or epidemiological properties. The most strict virus-host linkages under natural conditions have been detected for strains naturally infecting cherries (PPV-C and PPV-CR). However, although less stringent but still clear host preference is observed also for three epidemiologically most important strains (PPV-D/plum/apricot, PPV-M/peach, and PPV-Rec/plum). So far no genetic marker has been mapped in the PPV genome, which responsibility for the host specificity/preference could be explicitly demonstrated. In this review, we focus on the host preference of three major PPV strains as evidenced by analysis of an extensive dataset of PPV isolates of Slovak and world-wide origin. Together, we discuss several performed relevant experiments and further possible research procedures aimed to better understand the genetic determinants and mechanisms of the host preference of this potyvirus.