Efficient plant regeneration via somatic embryogenesis in bulbing fennel using immature flowers explants

In order to optimize plant regeneration techniques for bulbing fennel [Foeniculum vulgare Mill. subsp. vulgare var. azoricum (Mill.) Thell] via somatic embryogenesis, three different media were tested on four Sicilian fennel ecotypes derived from seed collections. Plant regeneration was obtained through the use of immature inflorescences as explants. Through comparison of different auxins, naphthoxyacetic acid resulted in high-level induction of embryogenic callus at the lowest concentration (4 mu M), in combination with 6-benzylaminopurine or thidiazuron. After germination of somatic embryos, regenerated plantlets were recovered on medium containing half-strength Murashige and Skoog salts and vitamins in the absence of plant growth regulators. Regenerated plants were successfully acclimatized (70 %) in a growth chamber prior to transplantation into an open field. The plants appeared phenotypically normal, and both genetic stability and uniformity were confirmed by random amplified polymorphism DNA analysis. The results represent a significant advance on previous reports, due to the high embryogenic ability of immature inflorescence from different ecotypes and the high percentage of regenerated plantlets acclimatized in ex vitro conditions.