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VIRUSES OF ORCHIDS AND THEIR TRANSMISSION BY RECIRCULATING NUTRIENT VIRUSES OF ORCHIDS AND THEIR TRANSMISSION BY RECIRCULATING NUTRIENT
VIRUSES OF ORCHIDS AND THEIR TRANSMISSION BY RECIRCULATING NUTRIENT SOLUTION C BOTTNER, B PEIN, M FUHRLING Institute of Forest Botany and Tree Physiology, Dept.of Tree Physiology, University of Freiburg, Am Flughafen 17, D-79085 Freiburgi. Br., Germany Background and objectives The investigations on virusinfected orchids demonstrate the transmission and spread of plantviruses by recirculating nutrient solution such as an irrigation ebb-flow-system. This system saves water and nutrition while recycling water, but at the same time it implicates the potential exists for spread of pathogens in reused water. We selected German orchids farms of major importance in orchid production who apply recycled irrigation water. Hundreds of orchids were tested to find the main virus pathogens causing serious yield losses. Studies followed how fast viruses are released from roots of diseased plants while contaminating the irrigation water and infect healthy plants. Materials and methods Four German orchid farms offered healthy and diseased plants for the experiments and provided samples of nutrient solution from tables with diseased and healthy orchids. They allowed to test leaf material from three hundred plants to detect the main causal viruses. Nutrient solution got naturally virus contaminated by growing virus infected orchids. The drained water was regulary tested for viruses as well as healthy orchids which were cultivated in the contaminated solution. All samples were tested by double sandwich ELISA [1]. Results and conclusions Tobacco mosaic virus (TMV), Cucumber mosaic virus (CMV), Tomato ringspot virus (ToRSV), Odontogiossum ringspot virus (ORSV) and Cymbidium mosaic virus (CYMV) were detected in virus diseased orchids and in nutrient solution taken from German farms. The later two pathogens ORSV and CYMV were found as the main viruses causing serious yield losses of orchids and known to spread fast within the culture. We continued the infection experiments with these two pathogens. The detection of ORSV directly from recirculating irrigation water was successfull after thirteen weeks, at the same time it was possible to detect the virus in leaves of all originally healthy plants. CYMV was found in nutrient solution after five weeks and in leaves after two weeks. The studies show that ORSV and CYMV are released from roots of diseased plants while contaminating the irrigation water and infect healthy plants within a short cultivation period. The results confirm the transmission of stable viruses by recirculating irrigation solutions as discussed by previous studies on different cultivars infected by TMV, CMV, TORSV or other viruses [1]. Virus transmission by water is well known and demonstrated by several authors who studied virus spread by environmental waters [2, 3]. References 1. Bilttner C, Marquardt K, Fahrling M, 1995. Acta Horticulturae 396, 265-72 2. Koenig R, 1986. Advances in Virus Research 31, 321-33 3. Buttner C, Nienhaus F, 1989. Eur. J. For. Path. 19, 206-11