first characterization of apple scar skin viroid from apple and pear cultivars in iran and determination of genetic diversity

apple scar skin viroid (assvd) is one of the most destructive viroid diseases in pome fruits orchards which can cause significant economic losses. symptoms of this viroid including scaring, distortion and dappling were seen in some apple orchards in east-northern of iran. sampling was carried out from apple and pear orchards. the rna was extracted by silica capture method from leaves. assvd was detected by rt-pcr. the purified pcr products were cloned into pgem®-t easy vector and recombinant plasmids were sequenced and sequencing analysis was done. we reported 12 new variants of assvd from apple and pear hosts with variable length between 329 to 334 nucleotides. phylogenetic analysis by the neighbour joining method showed that the iranian isolates were distinct from other isolates of assvd. mutation sites were indicated along the secondary structure of assvd molecule. this study provides the first report of detection and molecular characterization of assvd in apple and pear in iran.