Back-transmission of a virus associated with apple stem pitting and pear vein yellows from Nicotiana occidentalis to apple and pear indicators

The successful back-transmission of the mechanically transmissible virus associated with apple stem pitting and pear vein yellows, from Nicotiana occidentalis to apple seedlings "Golden Delicious" under greenhouse conditions is reported. This result enabled a field experiment where isolates of apple stem pitting, originating from apple, that were back transmitted from N. occidentalis 37B and N. occidentalis subsp. obliqua to apple seedlings are indexed by double budding on apple and pear indicators. One year after inoculation, symptoms associated with stem pitting and Malus platycarpa dwarf developed on Spy 227 and M. platycarpa apple indicators, together with symptoms associated with vein yellows on "Jules d'Airolles" and "Le Curé" pear indicators. The completion of the field trial will confirm whether or not N. occidentalis can replace the current woody indicators needed for the complete indexing of apple and pear, permitting to reduce dramatically the duration of the tests.