Direct shoot regeneration from leaf and internode explants of aloysia polystachya [[gris.]] mold. (verbenaceae)
2006
BURDYN, L. | LUNA, C. | TARRAGÓÓ, J. | SANSBERRO, P. | DUDIT, N. | GONZÁÁLEZ, A. | MROGINSKI, L.
Adventitious bud regeneration from leaf and internode explants of Aloysia polystachya was achieved. Shoots from nodal segments grown in vitro were cut into pieces and used as sources of explants. Organogenesis was induced from both explants cultured on quarter-strength Murashige and Skoog (MS) semisolid medium (plus sucrose 5 g l⁻⁻¹) containing different combinations of 6-benzyladenine (BA) and αα-naphthaleneacetic acid (NAA) under 116 μμmol m⁻⁻² s⁻⁻¹ photosynthetic photon flux density (PPFD), 14-h photoperiod, and at a temperature of 27 ±± 2°°C. The type of explant markedly influenced organogenesis and growth of the regenerated shoots. The regeneration frequencies were higher with leaf explants, while the number of shoots formed per responsive explant was greater with internode explants. However, the growth of regenerated shoots from internodes was seriously affected by vitrification. The number of shoots produced per responsive leaf explant increased from one to seven as the percentage of leaf explants producing shoots increased from 20 to more than 80%%. NAA at 0.05 μμM in combination with BA at 0.5 μμM induced the highest regeneration rate (87 ±± 8.8%%) after 20 d of culture, yielding 5.9 ±± 0.8 shoots per responsive leaf explant. Histological examination confirmed the occurrence of direct organogenesis. The regenerated shoots from the best induction treatment were transferred to a fresh medium without plant growth regulators for 30 d. Finally, the elongated shoots were rooted by pre-treatment in an aqueous solution of NAA at 500 μμM for 2 h and transferred to 1/4 MS. All plantlets raised in vitro were phenotypically normal and successfully hardened to ex vitro conditions. An experimental field plot with 2-yr-old in vitro-regenerated plants was established.
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