Propagation of Lilium hybrids. II. Production of plantlets from bulb-scale callus cultures for increased propagation rates

A method has been developed for the large-scale propagation of lilies from callus cultures. Bulb scales, being available at all times, are an ideal source of explants. Callus was induced throughout the annual cycle of all the 12 Oriental hybrid cultivars tested, by treating the bulb scales with a combination of 5 μM BA and 5 μM 2,4-D. Once initiated, this callus grew vigorously on media lacking exogenous growth substances. Callus induction by BA and 2,4-D, and the subsequent growth of such callus in the absence of exogenous growth substances, occurs within a broad range of cultivars and species within the genus. The callus could be maintained on a medium lacking ammonium salts, but the maximum growth rate was obtained at 10 mM NH₄NO₃. At low (0.2 mM) or zero levels of NH₄NO₃, light as compared with darkness was inhibitory to growth.The callus maintained its capacity for organogenesis. Maximum production of plantlets was obtained in continuous light on agar medium with 0.5 μM NAA.Potentially, the successive use of liquid and agar cultures can produce 6 × 10¹² plants per year from 1 g (dry wt.) of callus. Plantlets derived from callus were consistently diploid and could be readily transferred to soil.