First, how do we know RRD is a pathogen rather than the plant reaction to the mite (as stated in the ARS "Consulting Rosarian's Manual") and second, why is it now called "virus like" when in the 1960's and earlier some scientists called it a virus? |
ROSE ROSETTE |
Recently, Ailington et al. (1) reported that they had transmitted rose rosette virus in Nebraska with Phyllocoptes fructiphilus Koch. (The correct name is Phllocoptes fructiphilus Keifer 1940.) In one series of tests, ten P . fructiphilus from infected wild rose were transferred to each of ten healthy Rosa eglanteria. According to the authors, five plants became infected with rose rosette virus. The authors state that several species of Rosa were proved to be infected with rose rosette virus "either by grafting or by mite transmission"; however, they did not specifically state that the virus was graft-transmitted from those test plants to which P. fructiphilus had been transferred. This may only be an error of omission. Unless they graft-transmitted a virus from the plants that received mites, the appearance of symptoms on plants to which P. fructiphilus was transferred could be attributed to a mite-induced toxemia that resembled rose rosette. A definite statement that both types of transmission were accomplished in sequence would greatly substantiate their claim of transmission of a virus by P. fructiphilus. Also, a comparison of the effects on healthy rose plants of populations from infected and healthy roses would further substantiate their case. (Oldfield, 1970) |
Rose Rosette |
Although the identity of the causal agent of rosette is unproven, Gergerich et al. (1983) and Gergerich and Kim (1983) found in the cytoplasm of cells of diseased roses spherical virus-like particles measuring 120-150 nm with a 16 nm thick trilaminar wall, which resemble particles associated with two other eriophyid-bome diseases, fig mosaic and wheat spot. Ailington et al. (1968) reported graft transmission and transmission by the eriophyid mite, Phyllocoptes fructiphilus Keifer, to Rosa eglanteris L., Rosa suffulta Greene, Rosa woodsii Lindley, Rosa multiflora Thunberg ex. J. Murray and Rosa rubrifolia Villars. Recently, Amrine et al. (1988) clarified the role of P. fructiphilus as a vector of the rose rosette pathogen, rather than as an incitant of rose rosette, by demonstrating that symptoms resulting from feeding of the mite on healthy rose after transfer from symptomatic roses persisted and continued to develop after killing the mites with Temik. Mites held 14 days at 4°C (at which temperature they were immobilized) subsequently transmitted the rosette pathogen; single mites were able to transmit. (Oldfield and Proeseler,1996:p.268-269) |