Characterisation of Pear blister canker viroid isolates from Australian pome fruit orchards

Pear blister canker viroid (PBCVd) was detected in pear (Pyrus sp.), nashi (Pyrus serotina) and quince (Cydonia oblonga) trees from various pome fruit growing regions of Australia using dot-blot hybridisation and RT-PCR techniques. Characteristic symptoms of PBCVd infection were not observed on the infected trees. This is the first report of PBCVd infecting nashi varieties. The 12 Australian PBCVd isolates showed 92–99% nucleotide sequence identity with previously published sequences of PBCVd from other countries. The Australian isolates fell into two distinct groups based on sequence similarity and secondary structures. The possible origin of PBCVd in Australia is discussed.