Plant regeneration through somatic embryogenesis in Taxus wallichiana

We describe an efficient process for regeneration of Taxus wallichiana (Zucc) plants from callus cultures derived from zygotic embryos. Zygotic embryos cultured on half strength Lloyd and McCown's basal medium supplemented with SH vitamin (½ WPMSH), 0.5 mg l⁻¹ 6-benzyladenine (BA) and 1.0–2.0 mg l⁻¹ á-Napthaleneacetic acid (NAA) produced compact yellow (CY) callus after 4 weeks of culture. The 8-week-old CY calli (lines CY-A and CY-B) were initially slow growing but proliferated on transfer to WPM basal medium supplemented with 8.0 mg l⁻¹ 2,4-D, 0.1–0.9 mg l⁻¹ NAA and 0.3–1.0 mg l⁻¹ BA after 4 weeks. Four morphologically distinct calli lines were obtained, of which only two calli lines, CY-B-FW and CY-B-FY were embryogenic. The 12-week-old callus line CY-B-FW developed globular somatic embryos on transfer to secondary medium after 8 weeks and matured in maturation medium after 4 weeks. Only 10% of the mature somatic embryos regenerated into complete plantlets after 4 weeks on conversion medium. Although the frequency of conversion was low, complete regenerated plantlets via somatic embryogenesis were obtained after 7–8 months of initiation of culture. Taxane analysis showed that the paclitaxel accumulation was higher in embryogenic callus than in non-embryogenic callus.