Simple protocol for the micropropagation of teak (Tectona grandis Linn.) in semi-solid and liquid media in RITA® bioreactors and ex vitro rooting.
In Latin America the forestry of exotic species such as teak has been increasing in recent decades, due to their advantages in wood quality, rapid growth; and the relative ease of producing clones and their multiplication with respect to native species. Therefore, there is great interest in developing larger-scale propagation strategies that reduce costs and intensive manual labor. Culture in liquid media with temporary immersion and the semi-automation of the system has raised expectations for large-scale micropropagation. We report a protocol for teak, which reuses the primary explants in several culture cycles in semi-solid medium to produce nodal explants for the multiplication phase in temporary immersion bioreactors (RITA®). The control of factors such as cytokinin concentration, explants density, immersion frequencies and culture duration was analyzed. The number of shoots increased with 0.5 mg.l-1 of BA (6-Benzyladenine), alone or in combination with 0.5 mg.l-1 of Kinetin, with 2 daily immersions of 1 minute each; however, these shoots showed a high degree of hyperhydricity. When 0.05 mg.l-1 of BA was used with 1 immersion of 1 minute every 2 days, the hyperhydricity decreased. Although the number of shoots was lower, they showed good length to be used during multiplication and rooting ex vitro. Our results suggest that teak micropropagation can be simplified in two phases in vitro, the establishment and multiplication; followed by rooting ex vitro and acclimatization. This would imply a reduction in production costs, since most of the multiplication would take place in RITA® containers.