Experiments were conducted to establish an efficient protocol of micropropagation of Beaucarnea gracilis and B. recurvata two endemic and endangered Mexican species. Multiple shoots were induced by direct organogenesis from in vitro seedlings and longitudinal sections of seedlings in both species. The highest formation of shoots per explant, both B. gracilis and B. recurvata, was obtained from longitudinal sections of seedlings on Murashige and Skoog (MS) medium supplemented with 22.2 μm 6-benzylaminopurine, induced 8.2 and 11.1 shoots per explant respectively. In vitro rooting was readily achieved on MS medium with 1 g/l activated charcoal without growth regulators. According to initial treatment and depending on where the shoots come from, the rooting rates were 61% to 100% for B. gracilis, and 83% to 100% for B. recurvata. Survival rates in greenhouse conditions for both species were 80% to 100% after 3 months. These results indicate that the micropropagation of these species of Beaucarnea is technically feasible, and that in vitro culture is a useful option for the conservation and propagation of these important endangered species.
María Luisa Osorio-Rosales and Martín Mata-Rosas
María del Carmen Vadillo-Pro, Luis Hernández-Sandoval, Guadalupe Malda-Barrera, María Luisa Osorio-Rosales and Martín Mata-Rosas
The present study establishes an efficient protocol for in vitro propagation from longitudinal sections of seedlings of Beaucarnea purpusii, a threatened and highly appreciated ornamental species. The effect of three cytokinins: N6-benzyladenine (BA), kinetin (Kin), and thidiazuron, 1-phenyl-3-(1,2,3-thiadiazol-5-yl)urea (TDZ), in semisolid media and three different concentrations, as well as the effect of BA and TDZ pulses at higher concentrations in liquid culture medium, were investigated. Adventitious shoot formation by direct organogenesis was observed from all treatments. Additionally, adventitious shoot formation was recorded from the leaves of the new shoots; this particular response was exclusive to treatments supplemented with TDZ. In the experiment using semisolid culture media, the highest means of shoots per explant were obtained from treatments containing TDZ, particularly at a concentration of 0.45 μm (25.8 shoots per explant). For the pulses experiment, the liquid culture media supplemented with TDZ at 22.35 µm for 24 hours and 136.21 µm for 96 hours, induced a mean of 3.9 and 3.3 shoots per explant, respectively. Subculturing individual shoots on MS and half-strength MS (1/2MS) media, both supplemented with activated charcoal at 1 g·L−1, induced rooting in 85% to 95% of shoots. A survival rate of 100% under greenhouse conditions was achieved. The results of this study provide an efficient alternative for mass propagation of B. purpusii and may also contribute to the conservation and sustainable use of this valuable natural resource.