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 i dentified in sweet cherry (Prunus avium cv. Lambert) exhibiting sympto ms of little cherry disease. DsRNA was isolated from a symptomatic tre e and used as the template for cDNA synthesis and cloning. Radiolabell ed probes prepared from a resulting recombinant plasmid were used to e stablish 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 th at had a history of little cherry disease in the Kootenay and Okanagan valleys of British Columbia were used to inoculate Lambert cherry tre es. Hybridization of the radiolabelled clone occurred to the dsRNA iso lated from 48 symptomatic Lambert trees while no hybridization occurre d 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 occurr ence of little cherry disease in sweet cherry.