Occurrence of Hop stunt viroid in apple orchards of the Northwest Iran

We investigated the presence of hop stunt viroid (hsvd) in apple samples, showing dappling fruit symptoms, in the maragheh area (northwest iran) by means of rt-pcr. the viroid was detected only in leaves collected from symptomatic trees and a 298bp amplicon (ir-gala) was directly sequenced in both directions. multiple sequence alignment and blast analyzes revealed that ir-gala isolate shares the highest identity with grapevine isolates from brazil and china. amongst iranian isolates of hsvd available in the genbank, this isolate had the highest identity with grapevine isolate of hsvd from maragheh region. in phylogenetic analysis by mrbayes, ir-gala was clustered with grapevine isolates from brazil, china and iran and may suggest that hsvd-apple isolate could be originated from grapevine.