Production of virus-free carnations by means of meristem culture

The carnations which are normally grown are practically all infected with various viruses, and therefore attempts were made to obtain virus-free plants of a number of varieties by means of heat treatment and meristem culture. Incubators were designed in which the plants could be subjected to a heat treatment at a temperature of 37°C and at a high degree of humidity of the air. The ultimate percentage of virus-free plants in 1960 amounted to an average of 1.3%. This is sufficient to obtain a virus-free clone, but not enough to build up a virus-free assortment within a short time. The factors which may affect the percentage of successful isolations are discussed, viz. the effect of the season, of varietal differences and of differences between the material supplied by different growers. When the virus-free plants are propagated in practice it is essential that the material should be closely inspected and tested at regular intervals. The new material was found to possess most favourable qualities. It is sold with a special certificate.