Symptoms on apple and pear indicators after back-transmission from Nicotiana occidentalis confirm the identity of apple stem pitting virus with pear vein yellows virus

Isolates of apple stem pitting virus (ASPV) from diseased apple trees were maintained in Nicotiana occidentalis then back-transmitted mechanically from the herbaceous host to apple seedlings and indexed by double budding on apple and pear indicators for the following syndromes: apple stem pitting, pear vein yellows, Malus platycarpa dwarf and quince sooty ringspot. Symptoms associated with stem pitting and M. platycarpa dwarf developed on Spy 227 and M. platycarpa apple indicators and symptoms associated with vein yellows on Jules d'Airolles, Le Curè and Nouveau Poiteau pear indicators. A number of indicators were indexed for symptoms on stems. Clear stem pitting symptoms were detected on Virginia Crab, Spy 227, R 2720, C 7/1 and Pyronia veitchii. These results confirm the identity of ASPV and pear vein yellows virus (PVYV) as one virus causing different syndromes in apple and pear. The isolates could be readily detected in N. occidentalis 37B by RT-PCR with ASPV-specific primers.