Molecular characterization of Chinese Hop stunt viroid isolates reveals a new phylogenetic group and possible cross transmission between grapevine and stone fruits

A survey for the incidence of Hop stunt viroid (HSVd) infection in China was conducted using dot-blot hybridization. Out of 553 tested samples, 127 samples of stone fruits (apricot, peach, plum and almond), grapevine and hop were positive for HSVd, giving a mean infection rate of 23 %. Phylogenetic analysis revealed that most of the HSVd variants isolated from stone fruits, grapevine and hop were clustered into known hop and plum groups. However, two grapevine variants, HSVd.g50 and HSVd.g57, could not be clustered into any known groups, indicating a previously unknown phylogenetic group of HSVd isolates. HSVd.g38 was the single grapevine variant that clustered with the plum group isolates, supporting cross transmission between grapevine and stone fruits and the heterogeneity of grapevine isolates.