Hop stunt viroid (HSVd), belonging to the family Pospiviroidae, was first reported in hop, but infects several plant species, including herbaceous and woody hosts (e.g., grapevine, pear, peach, plum [2], apricot, almond, and pomegranate). In grapevine and apricot, the viroid appears to be latent. However, in other species, the viroid is associated with specific disorders: hop stunt, dapple fruit disease of plum and peach (2), and citrus cachexia. During spring 2000, stunted trees exhibiting delayed budbreak were observed in peach, cv. Redhaven, orchards in Sicily. In the summer of 2000, peach leaves were collected from symptomatic trees, triturated, and used to purify total nucleic acids by phenol extraction followed by CF-11 cellulose-chromatography. Viroid RNAs were detected by sequential polyacrylamide gel electrophoresis (sPAGE) and silver staining. Citrus exocortis viroid (371 nt) and Citrus viroid IIIb (294 nt) were used as standards. Nonradioactive hybridizations with digoxigenin (DIG)-labeled, Peach latent mosaic viroid (PLMVd) and HSVd RNA probes were used in viroid detection and identification. Predicted sizes of the viroid RNAs calculated in sPAGE and DIG probe hybridization demonstrated that ‘Redhaven’ peach trees were infected with PLMVd and HSVd. These results provide the first evidence of the contemporary presence of HSVd and PLMVd in peach trees. To our knowledge, this is the first report of HSVd in peach trees in Italy. Molecular characterization of this HSVd isolate is in progress to determine the nucleotide sequence of some of the variants in the population and to decide to which of the five proposed HSVd groups (1) this isolate should be assigned.
Reference: (1) S. A. Kofalvi et al. J. Gen. Virol. 78:3177, 1997. (2) T. Sano et al. J. Gen. Virol. 70:1311, 1989.
