Establishment of Embryogenic Cultures and Efficient Plant Regeneration System from Explants of Forced Softwood Shoots of Teak (Tectona grandis L.)

The present study highlights an efficient plant regeneration system in teak (Tectona grandis L.) using forced softwood shoots as an initial plant material. Forced softwood shoots of teak were cut to prepare shoot tip, nodal and internodal explants and cultured on Murashige and Skoog (MS) medium + NAA (1, 3, 6, 10, and 15 µmol ⋅ L−1) or TDZ (0.001, 0.01, 0.1, 1, 4, 8, 10, 12 µmol ⋅ L−1) for callus induction. Such calluses were further grown on the same levels of TDZ or 0.4, 1, 4, 8, 10 µmol ⋅ L−1 BA + 1 µmol ⋅ L−1 IBA or GA3. Callus induction was the highest with 4.55 cm3 callus volume and 5.75 g dry weight at 0.1 µmol ⋅ L−1 TDZ from shoot tips after 35 days. Embryogenic calluses were then shifted to 6, 8 or 12 µmol ⋅ L−1 TDZ + 2 µmol ⋅ L−1 BA or IBA along with 5 mmol ⋅ L−1 ascorbic acid (AA) for shoot regeneration from embryogenic cultures. The highest embryogenesis (100%) with 36.4 globular and 5.5 heart-shaped embryo-like structures was obtained at 8 µmol ⋅ L−1 TDZ + 2 µmol ⋅ L−1 BA after 63 days. Such cultures when further maintained on the same medium up to 150 days resulted in 100% shoot regeneration with 16.4 mean shoots. Shoots were elongated up to 50 mm on agar medium + 8 µmol ⋅ L−1 BA + 1 µmol ⋅ L−1 GA3. An efficient rooting response (70%) was achieved having 4.50 mean number and 49.10 mm root length at 8 µmol ⋅ L−1 IBA + 8 µmol ⋅ L−1 NAA + 0.1% activated charcoal after 36 days. Rooted shoots were acclimatized in glasshouse, achieving 56.6% plantlet survival.