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Immunosorbent electron microscopy (ISEMI) was a rapid diagnostic method far cymbidium mosaic virus (CyMV) and odontoglossum ringspot virus (CRSV) by trapping low concentrations of the viruses in crude sap preparations. The virus particles were trapped to increase up to 100∼200 fold by the homologous antibodies. Electron microscopic examinations of crude sap from diseased orchids leaves showed that CyMV was flexuous fiiamentous particles and ORSV was rigid rod-shaped particles. The size of the CyMV particles w as 480 × 13㎚, ORSV was 300 × 18㎚. The average infection rate was estimated to be 59%. Infection rates of Cattleya, Cymbidium, and Odontoglossum spp. were much higher than that of other orchid samples. This survey also showed that ORSV was much more prevalent than CyMV; 47% and 5%, respectively. The symptoms by ORSV on the orchids were mosaic, streaking, and necrotic spot, The symptoms by CyMV were chlorosis and necrosis. Mixed infection by both viruses might cause the necrotic spot and necrosis, No virus was detected on any seedlings from seeds of infected plants. It means that the two viruses might not be transmitted by seed. Neither CyIV nor ORSV was detected in plants of Cymbidium kanran Makino grown from meristem culture. ORSV was more prevalent in imported orchids than in domestic orchids collected from Cheju island in Korea; 27% and 7%, respectively.
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