Association of high molecular weight double-stranded RNA with little cherry disease

A double-stranded RNA (dsRNA) with an estimated size of 12.6 kbp was identified in sweet cherry (Prunus avium cv. Lambert) exhibiting symptoms of little cherry disease. DsRNA was isolated from a symptomatic tree and used as the template for cDNA synthesis and cloning. Radiolabelled probes prepared from a resulting recombinant plasmid were used to establish the association of the dsRNA with little Cherry disease in a collection of diseased symptomatic sweet cherry trees and in diseased trees in commercial orchards. Buds from 81 cherry trees in orchards that had a history of little cherry disease in the Kootenay and Okanagan valleys of British Columbia were used to inoculate Lambert cherry trees. Hybridization of the radiolabelled clone occurred to the dsRNA isolated from 48 symptomatic Lambert trees while no hybridization occurred to the dsRNA preparations from 33 Lambert trees that did not express little cherry disease symptoms. This confirms a positive correlation between the presence of the high molecular weight dsRNA and the occurrence of little cherry disease in sweet cherry.