PARTIAL ELIMINATION OF VIRUS FROM DOUBLY INFECTED ORCHIDS BY MERISTEM EXPLANT CULTURE

The problem of virus infections in the cultivated Orchidaceae is an extremely important and continuing challenge for which solutions must be found. The enormous reservoirs of viruses built up, especially of the Cymbidium mosaic virus, which continue to increase in this highly concentrated and rapidly expanding industry can only be viewed with alarm. Surveys in Hawaii show that a substantial number of prized cultivars are already infected and that this number will continue to increase with time. Whether the Cymbidium mosaic virus significantly affects all these cultivars, however, has not been fully established. Where significant symptoms are lacking little loss has been ascribed to this virus and much of the accompanying problem has been ignored. Nevertheless, long-range losses cannot be ignored in the light of the relatively high virus titre found in such infections. The need for producing virus-free plants from such infected cultivars is a pressing problem.

The elimination of viruses by means of meristem culture has been widely used (Hollings, 1965). Since the initial investigations of Morel and Martin (1952), this technique has been successfully applied in producing virus-free plants from infected source plants in a number of cultivated crops.

The literature does not indicate much success in the elimination of virus infections in the Orchidaceae. Morel (1962) was able to free Cymbidium from the Cymbidium mosaic virus. Although much effort apparently has been expended towards attaining this goal, the results have been poor. In light of Morel's results and those obtained for the potato viruses X and Y by Stace-Smith and Mellor (1967), it appears that this technique can be successfully applied to obtain virus-free plants from additional orchid genera infected with virus. This paper reports results of investigation to free such viruses from the Cattleya alliances.