Direct plant regeneration from in vitro-derived shoot apical meristems of finger millet (Eleusine coracana (L.) Gaertn.)

Abstract

A rapid and reproducible protocol for direct plant regeneration has been established using in vitro-derived, actively growing shoot apical meristems (SAMs) of the genotype 'CO(Ra)-14'. Shoot apical meristems from 3-day-old seedlings of three finger millet genotypes viz, 'CO(Ra)-14', 'Try-1', and 'Paiyur-2' were assessed for the efficiency of direct shoot induction. The regeneration efficiency of 'CO(Ra)-14' surpassed the other two genotypes and produced a mass of green, multiple shoots within 12 d on Murashige and Skoog medium containing 17.6 μM 6-benzylaminopurine (BA), 0.9 μM 2,4-dichlorophenoxyacetic acid in combination with 750 mg L−1 proline, 500 mg L−1 casein enzymatic hydrolysate, and 2 mg L−1 glycine. 'CO(Ra)-14' showed a maximum frequency of multiple shoot regeneration (96%) with an average of 8.3 shoots per explant. The age and size of shoot apical meristems played a crucial role in triggering adventitious shoot bud proliferation. The multiple shoot buds elongated spontaneously upon reducing the concentration of BA (to 11.0 μM) in the shoot induction medium. The in vitro proliferated shoots were rooted best in half-strength MS medium containing 2.8 μM indole-3-acetic acid and successfully acclimated in the field, subsequently developing into fertile plants. Thus, we report a short tenure (45 d) in vitro whole plant regeneration system, which could be effectively utilized for the production of transgenic finger millet plants.