Cydonia japonica, Pyrus calleryana and P. amygdaliformis: three new ornamental or wild hosts of Apple stem pitting virus.

Japanese quince, ornamental and wild pear symptomless samples were infected with Apple stem pitting virus (ASPV). Identification of ASPV was achieved by different PCR assays that amplified either the RNA polymerase or coat protein gene regions. For further confirmation, 312 bp amplicons within the polymerase gene were sequenced and compared with previously published ASPV sequences and additional sequences of isolates from ancient Italian cultivars. Comparison of the partial sequences isolated from wild/ornamental hosts and from cultivated species revealed significant divergence levels. Among the wild/ornamental isolates, the PCT88 isolate from Pyrus calleryana was the most divergent, having an amino acid deletion and incorporating a unique stretch of amino acids not present in any other isolate. Further to this preliminary partial sequence data, statistical analysis demonstrated that the isolates from wild or ornamental hosts were not more closely related to each other than to isolates from cultivated hosts. These results represent the first report of natural ASPV infection in these novel ornamental and wild Rosaceae hosts.