A rapid shoot multiplication protocol was established for the endangered cactus Mammillaria mathildae to reintroduce it to its natural habitat. In vitro-germinated seedlings were used as the source of explants. Three explant sources (apical, lateral, and basal excised from in vitro-germinated seedlings) were tested. Shoot multiplication was induced in Murashige and Skoog (MS) medium supplemented with different 6-benzylaminopurine/indole-3-acetic acid (BA/IAA) combinations (0, 22.19, 44.39 and 0, 1.43, 2.85, 5.71, respectively). Explants developed abundant callus in the presence of any BA/IAA concentration, whereas hormone-free media produced 0.59 ± 0.11 new shoots (with a 41% callus development) from basal explants. Apical and lateral explants produced 1.14 ± 0.07 and 4.09 ± 0.13 new shoots, respectively, without callus generation. Plantlets originating from lateral explants developed a vigorous rooting system after 2 months growing on MS medium supplemented with 30 g·L−1 sucrose. Under greenhouse conditions, 98% of micropropagated M. mathildae survived. Plantlets were reintroduced in an experimental plot near to Juriquilla's wild population of M. mathildae; over 52% of the outplanted M. mathildae lot declined after 5 months. Water availability was associated with the decline of outplanted populations during the first month (43%).
Oscar García-Rubio and Guadalupe Malda-Barrera
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.