Characterization of a virus associated with pear stony pit in cv. Wurttemberg

Pear stony pit associated isolate WT, which originated from diseased pear cultivar Wurttemberg, was characterized by biological tests on woody and herbaceous indicator plants, by serological test with polyclonal antisera against apple stem pitting virus (ASPV), as well as by the molecular methods of dsRNA analysis and reverse transcription-polymerase chain reaction (RT-PCR) with ASPV-specific primers. The reactions of indicator plants Jules d'Airolles, Beurre Hardy, Nouveau Poiteau, Pyronia veitchii, seedlings Pyrus communis, Nicotiana occidentalis 37B and Nicotiana occidentalis obliqua infected by WT isolate indicated the relatedness of WT isolate to ASPV. The positive serological reaction of coat protein of the WT isolate with polyclonal antibodies against ASPV in Western blot reaction was obtained. The slowest migrating dsRNA band associated with pear stony pit co-migrated with dsRNA having the highest molecular weight in different ASPV isolates from apple and pear. The dsRNA pattern of WT isolate was identical to dsRNAs associated with quince fruit deformation and sooty ringspot. In RT-PCR, the fragments were obtained of the expected 351 and 291 bp sizes using two sets of ASPV-specific primers from dsRNA templates in the WT isolate, as well as in control ASPV isolates ST and CJ. The results obtained have shown the WT isolate associated with pear stony pit in cv Wurttemberg, to be one of the apple stem pitting isolates.