Influence of plant growth regulators and spermidine on somatic embryogenesis and plant regeneration in four Indian genotypes of finger millet (Eleusine coracana (L.) Gaertn)

Effect of plant growth regulators and spermidine on somatic embryogenesis and regeneration was investigated in finger millet. Mature embryos, and 3 days old seedling-derived shoot apical meristems were cultured on Murashige and Skoog (MS) medium containing picloram, 2,4,5-trichlorophenoxyacetic acid, 2,4-dichlorophenoxyacetic acid (2,4-D) and 1-naphthaleneacetic acid. Improved embryogenesis (84.7 %) was found on MS medium containing 4.0 mg L-1 2,4-D and 0.5 mg L-1 kinetin in both explants. MS medium containing 1.5 mM spermidine along with 4.0 mg L-1 2,4-D and 0.5 mg L-1 kinetin produced highest frequency (90.4 %) of somatic embryogenesis from mature embryo derived callus in genotype 'CO(Ra)-14'. On same medium somatic embryogenesis frequencies of 'GPU-25', 'Try-1' and 'Piyur-2' genotypes were 55.5, 85.3 and 58.7 %, respectively after 4 weeks of incubation in dark. MS medium containing 4.0 mg L-1 6-benzylaminopurine, 0.2 mg L-1 2,4-D and 1.5 mM spermidine was found to be optimum for shoot regeneration or somatic embryos in all four genotypes of finger millet. We also studied the influence of exogenous spermidine (2.0-4.0 mM) on regeneration of 'CO(Ra)-14' mature embryo-derived new and long-term (20-180 days old) calluses. Highest regeneration frequency 93.1 % and mean number of shoots 25.5 were produced on MS medium containing 3.0 mM spermidine, 4.0 mg L-1 BAP and 0.2 mg L-1 2,4-D using 60 days old callus. Regenerated shoots effectively rooted on half-strength MS medium and successfully acclimatized in soil with 100 % survival rate and they grew normally without showing any morphological variation. Genetic variation of in vitro derived plants and control plants were analyzed by RAPD markers.