PEACH LATENT MOSAIC AND POME FRUIT VIROIDS IN NATURALLY INFECTED CULTIVATED PEAR PYRUS COMMUNIS AND WILD PEAR P. AMYGDALIFORMIS: IMPLICATIONS ON POSSIBLE ORIGIN OF THESE VIROIDS IN THE MEDITERRANEAN REGION

Abstract

Peach latent mosaic viroid (PLMVd) and apple scar skin viroid (ASSVd) were detected in naturally infected cultivated pear Pyrus communis in Greece and Italy and wild pear P. amygdaliformis in Greece. Pear blister canker viroid (PBCVd) was also detected in P. communis and pear P. amygdaliformis in Greece. PLMVd, ASSVd, and PBCVd were detected by molecular hybridization analysis in about 37%, 39%, and 62%, respectively, of 48 samples of fruits, leaves, buds, shoots, or twigs of cultivated and wild pear trees in Peloponnesus, Greece. PLMVd variants from the Italian pear cultivar ‘Passacrassana’ and the Greek wild pear both had a chain length of 338 nucleotides and 89-90% identity with the French and Italian PLMVd variants from peach. ASSVd and PLMVd in infected pear cultivar ‘Passacrassana’ were graft transmissible in pear. This is the first report which shows that PLMVd and ASSVd naturally infect cultivated and wild pear in the Mediterranean and that PLMVd naturally infects hosts other than Prunus spp. Our findings suggest that PLMVd, ASSVd, and PBCVd may have originated in the Mediterranean in their host plants, most probably in P. amygdaliformis.