FIRST REPORT OF HOP STUNT VIROID IN LEBANESE FIG TREES

Abstract

In the course of a survey carried out in 2010 in the main fig-growing areas of Lebanon (Bekaa and Mount Lebanon), a total of 100 samples representative of 15 dif- ferent cultivars were collected and tested by RT-PCR for the presence of Hop stunt viroid (HSVd) using viroid-spe- cific primers (Sano et al., 2001). Distinct PCR products of the expected size (303 bp) were amplified from 12 fig trees of cvs Houmairi (6), Bayadi (5) and Sweidi (1), all originat- ing from the Bekaa valley. This result was further con- firmed by dot blot molecular hybridization using a HSVd- specific riboprobe. Only seven infected plants showed symptoms resembling those typical of Fig mosaic disease, the remaining being symptomless. Five of these HSVd iso- lates were sequenced (accession Nos HE662802- HE662806) and compared with the other HSVd isolates from GenBank. In Blast analysis, all the sequenced HSVd isolates showed 99-100% nucleotide identity among them and 94-95% identity with the HSVd type member (X0009). The only exception was the isolate D1, which confirmed the 94% identity with HSVd type but showed a lower identity level (94-95%) with the other HSVd Lebanese fig isolates. In a phylogenetic tree constructed with whole viroidal sequences the Lebanese fig isolates, ex- cept for D1, clustered in a separate group together with fig isolates from Syria and mulberry isolates from Lebanon (Elbeaino et al ., 2012a, 2012b). To our knowledge this is the first report of HSVd in Ficus carica in Lebanon.