Production of virus-free bulblets from callus induced from scale culture of Lilium longiflorum 'Georgia'

When Lilium longiflorum 'Georgia' callus was induced from bulblet- scales in MS (Murashige and Skoog, 1962) medium supplemented with 5.0 mu M picloram, callus growth was more vigorous in liquid than on a solid medium. When the calli were transplanted to MS medium and 1/2 MS (half strength inorganic elements and full strength MS organic elements), the frequency of shoot formation (percentage of callus regenerating shoot and number shoot per callus) was higher in the solid than in the liquid medium. However, the shoot forming capacity decreased as the number of subculturing was increased. Bulblets regenerated from subcultured calli were stored at 4 degrees C for 8 weeks and then transplanted to soil. After a 6-month cultivation in soil, when scaly leaves were indexed for viruses, the number of infected bulblets decreased in those regenerated from calli subcultured five times. Cucumber mosaic virus (CR IV) was not detected. The addition of antiviral chemicals (DHT, ribavirin) in the regeneration medium (MS medium without growth regulators) had little influence on the rate of shoot regeneration from calli but increased the rate of virus- free bulblets. The addition of 50 mu M DHT eliminated CMV and LSV effectively to reduce infection rate of bulblets to 19% even after 6-months cultivation in a greenhouse.