Induction and scale-up of Billbergia zebrina nodule cluster cultures: Implications for mass propagation,improvement and conservation

The Tropical Atlantic Rain Forest is a biome of high diversity and endemism of plant genetic resources. High diversity of bromeliad species occurs in this biome, but part of them is now endangered. Tissue culture based techniques comprise valuable tools for the mass propagation and conservation of endangered bromeliads. In the present work the in vitro regenerative system based on the induction and development of NC from nodal segments of Billbergia zebrina showed different morphogenetic features from those observed in organogenesis and somatic embryogenesis. Different levels of TDZ, NAA, and 2i-P promoted the induction of NC with different morphologies and regenerative potential. NC induced in response to 0.01 μM of TDZ and subcultured on BM free of PGR resulted in high regenerative frequency. NC originated from BM supplemented with TDZ (0.1 μM) when subcultured on BM with NAA (2 μM) and 2-iP (4 μM) resulted in higher mean number of shoots. Elongated shoots were successfully acclimatized in ex vitro conditions and derived plantlets had normal phenotype. Histological analyses revealed the morphogenesis of the NC related to organization of the meristematic zone in the subepidermic region composed by organized layers with small and isodyametric cells followed by the induction of shoot buds. SEM analysis showed that the induction of NC occurred from the basal region of the explants.