PRODUCTION OF VIRUS-FREE ORCHIDS VIA TISSUE CULTURE TECHNIQUES

Due to constant handling and vegetative propagation, most commercially cultivated orchid hybrids are systemically infected with cymbidium mosaic virus (CyMV) and/or odontoglossum ringspot virus (ORSV). Two tissue culture techniques were employed in this project to eliminate the viral pathogens from the infected orchid plants: meristem culture and thin section culture with/without chemotherapy. Meristems (0.10 mm to 1.00 mm) were excised from axillary shoots of CyMV and ORSV infected Mokara Char Kuan 'Pink', a monopodial hybrid and CyMV-infected Cattleya Bowbells, a sympodial hybrid. Although the survival rate was very low, two plants were obtained from the larger meristems. However, these plants remained virus-infected. In contrast, thin section culture of both shoot and protocorm-like bodies yielded many virus-free plants regardless of the presence of ribavirin. A highly sensitive diagnostic test for CyMV was also developed based on the polymerase chain reaction. As little as 1 fg of viral RNA (about 200 target copies) or 10 fg of purified virus (approximately 130 viral particles) could be detected. Only 1 mm3 of plant sample was required and the results could be obtained in 5 h.

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