Brief report: genome sequence and construction of an infectious cDNA clone of Ribgrass mosaic virus from Chinese cabbage in Korea.

Ribgrass mosaic virus (RMV) has severely decreased the production and lowered quality of Chinese cabbage co-infected with Turnip mosaic virus (63.4%) in Korea. The complete genome sequence of RMV isolated from Brassica rapa ssp. pekinensis was determined. The full genome consisted of 6,304 nucleotides and showed sequence identities of 91.5-94.2% with the corresponding genome of other RMV strains. Full-length cDNA of RMV-Br was amplified by RT-PCR with a 5'-end primer harboring a T7 promoter sequence and a 3'-end RMV specific primer. Subsequently, the full-length cDNA was cloned into plasmid vectors. Capped transcripts synthesized from the cDNA clone were highly infectious and caused characteristic symptoms in B. rapa ssp. pekinensis and several indicator plants, similar to wild type RMV. Since there has not been found RMV resistant Chinese cabbage yet and the virus has been prevalent already throughout the natural fields of Korea, the identification of full sequence and development of infectious clone would help developing breeding program for RMV resistant crops.