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RMV... What do you do after?
Henry Kuska wrote:
Cass, concerning your suggestion to publish an article on the subject in the American Rose Annual: I assume that the U. Calif. Davis research is nearing completion. I hope that they would then write such an article as they are the "horse's mouth". Henry, I can appreciate your reluctance to survey the literature when such a report is expected shortly. However, the amount of accurate information in a form readily accesssible to even well-informed rosarians is quite limited. I would view a survey as a precursor to the Davis report, which undoubtedly will include several provisos that "more research is needed." That is the perpetual state of knowledge. Additionally, there is an unsatisfying air of "Don't worry, be happy" surrounding the occurrence of rose mosaic virus. Don't we all wonder if we would need fewer fungicides and in certain parts of the country suffer fewer winter losses if there were fewer virused plants foisted on on the public? I was delighted this spring to see Jackson Perkins offering guaranteed virus free plants....for close to $20 each. I "expect" that they are preparing something for the conference covering virus diseases of ornamental plants which is scheduled for 2004. (Often, researchers try to present their results at conferences such as this one in order to assure that the work gets maximum exposure among those working in the field.) Looking at this list of mosaic viri (see? kits are available) http://www.dsmz.de/plvirus/elisa_o.pdf, it is no surprise that roses suffer from mosaic virus. I've seen common weeds in my yard suddenly show up with mosaic or variagation of the foliage. I suspect that the 1 to 4 % contagion rate is low. My experience with both budded new releases and with old roses is not reassuring, more on the order of 25% than 1 %. That experience has bolstered my interest in collecting and propagating own root, healthy old roses from very old homes. I read your information about mosaic symptoms showing up as early as the 1860's. Whatever its rate of transmission then, it could only increase with modern transportation and production techniques. Apart from different rates of contagion for different virii, it seems obvious that different modes of transmission would have different rates of success. Add that to different susceptibility of cultivars, and the landscape gets complicated quickly. But "Don't worry be happy" seems just simple minded and an abandonment of efforts to improve. Transmission by pruning equipment is the most obvious concern of most home gardeners. Not knowing (a) how easily transmissible the viruses are and (b) how many roses suffer from them without showing symptoms, may make all efforts futile. There is no way of assuring the cleanliness of pruners even after washing, dipping and drying, especially with little more more than strings of protein involved. That doesn't mean I will abandon those efforts. Disposable pruners? No pruning? Not likely. Just my thoughts after reviewing your materials. |
#47
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RMV... What do you do after?
One of our daughters and her family was visiting for the week so I
have been busy being "grandpa", but I did have time during their naps to search for literature evidence that related to what Tom Liggett said about rose virus returning to heat treated roses. The first thing is the following link http://groups.google.com/groups?hl=e...395300.XAA2410 1%2540ladder01.news.aol.com%26rnum%3D2 That link states that it was stated at a meeting and that others heard it also. ------------------------------------------------------------------------------------------- The reference that appears to be the most interesting is: Title: Recent Issues raised in the Evaluation of Virus Removal and Inactivation Authors: White, E.M., and Woodward, R.S., Published in Genetic Engineering News, volumn 15, page 6, (1995). (Note, the page number is ambigious in the source that I found this in.) Unfortunately no abstract was given. Can anyone provide look this reference up? -------------------------------------------------------------------------------------------------- A number of German papers (by the same labatory plus other laboratory co-authors) appear to say something which is related to this issue. I purchased one of the most recent of their papers. Title: Phytosanitary Improvement of Fruit Tree Species: Diagnostic Strategies in Virus-Indexing of In Vitro Plants Authors: A. da Camara Machado, D. MendonCa, M.S. Lopes, E. Knapp, V. Hanzer, W. Arthofer, H. Katinger, M. Laimer da Camara Machado Authors affiliation: this was a combined publication from a laboratory in Portugal and a laboratory in Austria. Published in: Acta Hort., volumn 472, pages 511-516, (1998). In the actual paper they say that one of the points of the investigation was: "2) Are virus elimination treatments merely reducing the virus titer, but are they failing to eliminate some viruses entirely. If so, how long does it take for those viruses to reaccumulate to detectable levels?" The above sounds like exactly what we are looking for (but not on roses). In in their Results section, they say: "Furthermore, we tried to understand whether, in some cases, virus elimination treatments merely reduced the virus titer or failed to eliminate some viruses entirely. If so, how long does it take for those viruses to reaccumulate to detectable levels? Depending on this situation, how many tests are necessary to confirm initial negative test results? It is known that elimination treatments may depress the pathogen titer below the threshold level of detection (Fridlund, 1989). In this respect the effects of thermotherapy on the titer of ASGV and ACLSV were investigated in in-vitro-shoots of several apple cultivars. Irrespective of the duration of thermotherapy treatment (depending on heat sensitivity of the plant material), the virus titer of both ASGV and ACLSV initially was decreased dramatically. Shoots that were multiplied in vitro for over 2 years and used as starting material. Before undergoing thermotherapy, they tested 100 % positive for ACLSV, 100 % negative for ApMV and showed values around the threshold level of 36% for ASGV, as shown in Fig. 1 for the Austrian cultivar Maschanzker. After thermotherapy meristems were excised and regenerating shoots submitted to a multiplication step to increase the number of shoots. After 7 months, plantlets were tested again and showed mainly negative values or vahies around the threshold for ApMVand ACLSV, indicating that the elimination success was satisfactory. On the other hand, after 7 months 7% of the samples were postive when tested for ASGV, indicating a different reaction pattern (Fig. 1)...................................... It is a definite fact that plants with a double infection of ASGV and ACLSV are more difficult to- treat. However, we do not know, so far, on which mechanism this synergistic effect may rely. Samples of the different groups were compared (Fig. 2). From the nontreated positive control plants, only ApMV was not detected after this period in vitro. Values around the threshold were obtained from the originally negative plantlets. In other cultivars, from originally negative clones multiplied in vitro, a high number of samples showed ASGV positive results after more than one year of in vitro culture. ------------------------------------- The detection of ASGV by ITP in shoot tips from several potted plants of Maschanzker grown for 2 years in the greenhouse (data not shown) was, however, a concern. Therefore, the need for a more reliable detection system seems evident." The DISCUSSION section contained the following: "As it is still common practice in sanitation programs to carry out in-vitro treatment and ex-vitro re-testing for selection of plant material. The result is a lack of knowledge of the speed of recovery of low pathogen levels under in-vitro conditions (IPGRI/FAO, 1994).......................... Elimination treatments depressed virus titer, as could be shown for a wide range of cultivars. Thermotherapy, however, alters or destroys viral proteins, therefore, serodiagnostics are of little value for reliable early screening. Furthermore, there remain the limitations of current ELISA-based serological tests which might be not sensitive enough to detect very low levels of virus. Also, the time required by the different viruses to recover up to a level of detection from low levels of infection will again be dependent on the pathogenhost combination. ACLSV was readily detected after re-accumulation above the threshold level whereas the well-known problems in reliable diagnosis of ASGV were further encountered even after several tests of in-vitro cultures (Fuchs et at, 1988, Gilles and Verhoyen, 1992). We assume that molecular diagnostics will improve the aforementioned problems. Other methods which, so far, are not used for routine diagnostics, like PCR or immuno-capture-PCR, will be introduced into the sanitation program to improve the system of diagnosis for in-vitro plants." ----------------------------------------------------------------------------------------------------------- There were several Japanese papers which also appeared to be related to our topic. The following is one: Title: Evaluation of virus-free bulblet production by antiviral and or heat treatment in in vitro scale cultures of Lilium longiflorum 'Georgia' and L-X 'Casablanca' Authors: Xu PS, Niimi Y Authors affiliation: Xu PS, Niigata Univ, Fac Agr, Ikarashi 2-8050, Niigata 9502181, Japan Published in: JOURNAL OF THE JAPANESE SOCIETY FOR HORTICULTURAL SCIENCE, volumn 68, pages 640-647, (1999) Abstract: "This study evaluated the effects of chemotherapy (addition of ribavirin or 2-thiouracil to a medium) and/or heat treatment at 35 degrees C on the Production of virus-free bulblets in the scales culture of Lilium longtiflorum 'Georgia' and L. x'Casablanca', infected with lily symptomless virus (LSV), tulip breaking virus-lily (TBV-L), and cucumber mosaic virus (CMV). 1. When scales were cultured on a medium with ribavirin at 50 mu M, ELISA-absorbance values at 405 nm for LSV in the incubated scales decreased as the incubation Lime lengthened, whereas the TBV-L, values of the scales decreased at almost the same rate as those of the control. 2. When scales of L. longiflorum 'Georgia' were cultured on medium with antiviral chemicals, the number of bulblets formed decreased as concentrations of antiviral chemicals increased. Viruses were detected in about 20% of the bulblets at the end of culture when the scales were cultured on medium with ribavirin and 2thiouracil at 50 mu M; however, mo than 44% of the bulblets, which were transplanted into soil and cultivated in the greenhouse for 6 months, showed the positive reaction in viruses. 3. Scales excised from bulblets heat-treated at 35 degrees C for 4 weeks formed fewer bulblets than those of control, especially the scales of 'Georgia'. 4. Chemotherapy in combination with thermotherapy was more effective in decreasing the number of virusinfected bulblets than was the single treatment. When scales, kept at 35 degrees C for 4 weeks, were cultured on medium with 5 mu M ribavirin, viruses were detected in 30% of the bulblets of 'Georgia' and 6% of those in 'Casablanca' at the end of in vitro culture. However, viruses were detected in 100% of the bulblets in 'Georgia' and 44% of those in 'Casablanca' which were transplanted into sail and cultivated in the greenhouse for 6 months." The Ohio State Research Laboratory at Wooster does subscribe to this journal. However, the article is written in Japanese so I cannot add to the abstract. ---------------------------------------------------------------------------------------------- My comment (Henry Kuska): it appears that, at least in some plant systems, treated material may have a virus level below the detection limit of ELISA, and that small amount of undetected virus may then grow to detectable levels. ------------------------------------------------------------------------------------------------ .. The following is a paper which compares ELISA detection of PNRSV to other methods: Title: Comparative analysis of ELISA, nonradioactive molecular hybridization and PCR for the detection of prunus necrotic ringspot virus in herbaceous and Prunus hosts Authors: Sanchez-Navarro, Apancio, Rowhani & Pallas Published in: Plant Pathology, volumn 47, page 780, (1998). Abstract: "Comparative analysis of ELISA, nonradioactive molecular hybridization and PCR for the detection of prunus necrotic ringspot virus in herbaceous and Prunus hosts Three methods were compared for the detection of prunus necrotic ringspot virus in herbaceous and woody plants: DAS-ELISA, nonisotopic dot-blot hybridization and reverse transcriptional polymerase chain reaction (RT-PCR). When purified virus preparations were used, the detection limit of the RT-PCR technique was 1.28 pg mL-1 whereas nonisotopic molecular hybridization and DAS-ELISA allowed detection of 0.8 ng mL-1 and 4 ng mL-1, respectively. Several sample processing procedures were evaluated for virus detection by the nonisotopic molecular hybridization technique. When a very short and simple sample processing method was used, the detection limit of the nonisotopic molecular hybridization technique was 25 times higher than that of DAS-ELISA and 625 times lower than that of RT-PCR. A comparison of the level of virus accumulation in mature fruits and in leaf tissue showed that, on average, 125 times more virus was found in the fruits." |
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