Liquid culture as a positive condition to induce and enhance quality and quantity of somatic embryogenesis of Lilium longiflorum

The objective of this study was to establish a simplest and efficient method for high frequency of somatic embryogenesis and plant regeneration of Lilium longiflorum ‘Easter Lily’. Embryogenic cell formation was obtained from friable calli cultured in either agar-solidified or liquid MS media at different volumes containing 1.0 mg l−1 α-naphthaleneacetic acid (NAA) and 0.2 mg l−1 thidiazuron (TDZ). However, the number of somatic embryos derived from embryogenic calli cultured in liquid medium, especially at a volume of 20 ml, were shown to be more than in solidified medium, 170 rather than 28, and the forms of somatic embryos in different developmental steps (globular-, heart- and cotyledon-shaped) were clearly distinguished under microscope. The submerged calli in liquid medium became necrotic due to the loss of respiration while the emerged calli underwent embryogenesis. Mature somatic embryos were transferred onto hormone-free 1/2 MS medium for germinating and developing into plantlets. About 78% of the embryos developed into plantlets with normal radicle and plumule. One-month-old regenerated plantlets were then transplanted in nursery and the survival rate was of 98%. After 6 months, more than 1500 plants originated from somatic embryos were shown to be more vigorous than plants obtained via direct organogenesis.