Evidence of root graft transmission of two rose mosaic viruses, Prunus necrotic ringspot virus and Apple mosaic virus in rose rootstocks
D. A. Golino (1), S. T. SIM (1), M. Cunningham (2), A. Rowhani (1)
(1) Department of Plant Pathology, University of California, Davis, CA, U.S.A.; (2) Foundation Plant Services, University of California, Davis, CA, U.S.A.
Phytopathology 101:S62

Rose mosaic disease is often caused by Prunus necrotic ringspot virus (PNRSV) and Apple mosaic virus (ApMV). It is primarily spread by propagation; observations indicate a means of natural spread. Cuttings from two rootstocks, Rosa hybrida ‘Dr. Huey’ and R. multiflora ‘Burr’, with and without virus were rooted and transplanted to pots. Viruses were: ApMV, PNRSV and a natural infection of ApMV + PNRSV. Treatment pots contained one virus-positive and one virus-negative plant in the same pot to permit root grafting. Control pots contained one virus-positive or one virus-negative plant; pots were arranged to allow stem contact. All virus-negative plants had a possibility of becoming infected by pollen or insect transmission. Dr. Huey included 60 virus-negative and 60 virus-positive control pots; and 120 treatment pots. R. multiflora included 20 virus-negative and 20 virus-positive control pots; and 20 treatment pots with ApMV + PNRSV. All plants were ELISA tested for 5 years. All virus-negative plants in control pots tested negative all 5 years. The percent of initially virus-negative plants in treatment pots that tested positive was 0, 5.3, 10.5, 10.5, 10.5 in Dr. Huey and 0, 12.5, 33.3, 46.7 and 46.7 in R. multiflora for years 1 to 5 respectively. All plants that became infected were potted with ApMV + PNRSV plants. Rose mosaic symptoms were observed only in plants with ApMV + PNRSV. This indicates that root grafting plays a role in spread of rose mosaic disease.