Micropropagation of Onion (Allium cepa L.) from Immature Inflorescences

MARINANGELI PABLO

Protocols for Micropropagation of Selected Economically-Important Horticultural Plant

Humana Press - Springer

Lugar: New York; Año: 2013; p. 319 - 328

In vitro plant production by direct organogenesis from immature flower heads is suitable for clonal propagation of onions (Allium cepa L.). This technique ensures genetic stability, offers a high rate of propagation and allows keeping the explant donor plant with advantage over other forms of in vitro regeneration. Onion micropropagation is usually applied in breeding programs, genetic-cytoplasmic male sterile lines maintenance and multiplication for hybrid production, germplasm conservation and as a tool for the application of other biotechniques. For in vitro culture, mature onion bulbs are induced to reproductive phase by vernalization and forced to inflorescence initiation. Immature umbels are dissected from bulbs or cut directly when they appear from the pseudostem among the leaves. Disinfected inflorescences are cultivated in BDS basal medium supplemented with 30 g L-1 sucrose, 0.1 mg L-1 naphtalene acetic acid, 1 mg L-1 N6 benzyladenine, and 8 g L-1 agar, at pH 5.5, under 16 h photoperiod white fluorescent light (PPD : 50-70 mmol s-1 m-2)  for 35 days. Once shoot clumps develop, they can be divided and subcultivated under the same conditions. For bulbification phase, the individual shoots are cultivated in BDS basal medium supplemented with 90 g L-1 sucrose, with no plant growth regulators, at pH 5.5, under 16 h photoperiod. Microbulbs can be directly cultivated ex vitro without any acclimation.