ANALYSIS OF DOUBLE-STRANDED RNAS FROM CHERRY TREES WITH STEM PITTING IN CALIFORNIA

Five distinct dsRNA species were recovered from Bing sweet cherry (Pru nus avium (L.) L.) trees with stem pitting symptoms. A 4.7-kilobase pa ir (kbp) dsRNA was isolated from mahaleb rootstock (P. mahaleb L.); an unrelated 4.7-kbp dsRNA, always co-purified with a 1.3-kbp dsRNA, and a 9-kbp dsRNA were from Bing cherry. In addition, an 8.5-kbp dsRNA fo und in diseased Shirofugen flowering cherry and in Bing cherry was ide ntified as sour cherry green ring mottle virus (CGRMV). The larger, 8. 5- and 9.0-kbp dsRNA species were graft-transmissible, while the small er ones were non-transmissible and appeared cryptic in nature. Reverse transcription-polymerase chain reaction (RT-PCR) assays were develope d for each dsRNA species by cloning and sequencing cDNA synthesized fr om the dsRNA templates. When several diseased collections were assayed by RT-PCR, approximately 14% reacted positively with primers for the 9.0-kbp dsRNA or CGRMV. Although CGRMV and the 9.0-kbp dsRNA caused wo od-marking symptoms in graft-inoculated Mazzard (I! avium) seedling tr ees, no xylem or canopy symptoms developed in grafted Bing cherry. The causal agent or agents of cherry stem pitting have not been identifie d.