Morfogénesis in vitro de brotes adventicios del pinabete mexicano Pseudotsuga menziesii

Pseudotsuga menziesii is a conifer of ecological and economic importance worldwide. Due to the small size of its native populations in Mexico, natural regeneration in this species is poor, therefore in vitro cultivation is considered as an alternative strategy for its propagation and conservation. The effect of two combinations of auxins and cytokinins in the induction of adventitious shoots was compared. Mature embryos were grown on solid Schenk and Hildebrandt (SH) medium containing 0.53/13.32 μM of 1-naphthalene acetic acid (NAA) / 6-benzyladenine (BA) or 2,4-dichlorophenoxyacetic acid (2,4-D) / kinetin (K). The buds were formed via direct organogenesis in the hypocotyl and cotyledons. After 90 and 130 days of culture, the organogenic capacity was higher in NAA / BA and extended for a longer period than in 2,4-D / K, although the latter the shoots were more vigorous. Histological analysis showed the sequential appearance of distinct promeristemoids and meristemoides on the surface far from the medium, whereas wide meristematic zones and meristematic nodules formed in the tissues in contact with the medium, which gave rise to the outbreaks, was detected in both treatments. Because the buds formed included cells of the epidermis and embryonic subepidermis a multicellular origin is proposed. This work allowed us to better understand the events associated with direct organogenesis that may impact on the consolidation of regeneration protocols and future improvement strategies.