Rapid in vitro propagation and microtuber production in Ullucus tuberosus (Basellaceae)

A rapid in vitro propagation system leading to the generation of plantlets and microtubers was developed for Ullucus tuberosus. The method consisted of a two phase culture. The first started with nodal sections, each showing 3-4 axillary buds, and was the source of a large number of new shoots (max. 18.3 shoots/ flask) which formed within 15 days. Development of new shoots by axillary-bud sprouting and profuse shoot branching took place after 2-4 days in the presence of MS-media supplemented with various growth regulators including NAA, GA(3), BA or Z (Zeatin). The second phase, taking place after 15 days, consisted in subculturing single shoots to promote the production of roots and microtubers. Single shoots, transferred to a liquid (chromatogram paper-bridges) or jellyfied MS-agar medium in various levels of the indicated plant growth regulators, developed roots forming plantlets with I or more microtubers within 2 months. The highest tuberization yield was obtained in the presence of NAA (0.3 mg 1(-1)), BA (0.1 mg 1(-1)) and GA3 (0.01 mg 1(-1)) resulting in approx. 83 % tuber formation.