The genus Beaucarnea belongs to the family Asparagaceae, subfamily Nolinoideae, and occurs from northeastern Mexico to northern Central America (Bogler, 1998). Mexico harbors 10 of the 11 recognized species, of which eight are catalogued as threatened, one as endangered (B. purpusii), and one under study to determinate its status (Hernández et al., 2012).
The critical situation of most of Beaucarnea species is due to habitat alteration and over-collection of seeds, seedlings, and adult individuals, which are highly appreciated as ornamental plants. These circumstances affect the population size and the sex ratio, causing a low fertilization rate and consequently a reduced seed production (Contreras et al., 2008; Golubov et al., 2007).
B. purpusii occurs in small areas of the Tehuacán-Cuicatlán Biosphere Reserve, Mexico, which encompasses the states of Puebla and Oaxaca in Mexico (Fig. 1A), and the main reasons for this species being endangered are the small size of its populations, its restricted geographic distribution, the lowest growth ratio of the 11 species in the genus, and the local use of the inflorescences and infrutescences as small Christmas trees, leading to a decreasing number of seeds available for natural germination (Hernández et al., 2009). Because of this situation, it is critical to take action to guarantee its continued survival and sustainable use.
For species like B. purpusii, the traditional conservation approach is in situ conservation (Engelmann, 2011); however, it is now recognized that these can be efficiently complemented by ex situ techniques. Actually the latter may represent the only feasible option for conserving certain highly endangered and rare species (Sarasan et al., 2006).
Plant tissue culture has proven to be a valuable technique for propagation, conservation, and sustainable use of many species, specially of those with sexual and asexual reproduction limitations, slow growth rate, low seeds availability, and endangered conservation status (Pence, 2011; Sarasan et al., 2006), all of which is true for most Beaucarnea species (Contreras et al., 2008).
To initiate in vitro propagation, plant growth regulators (PGRs) can be applied to explants following two different methods: 1) traditionally the explants are placed on nutrient medium containing PGRs for 3–4 weeks, transferring them afterward to medium lacking PGRs. 2) Explants can be pulse treated with a concentrated liquid solution of cytokinin and auxin solution for several hours, after which they are placed on medium free of these PGRs, and some studies report improved organogenesis when using the liquid pulse method (Goldfarb et al., 1991; Madhulatha et al., 2004; Ramírez-Malagón et al., 2008).
In spite of the botanical and ornamental interest in Beaucarnea species, studies concerning their in vitro propagation are scarce. There are some reports for Beaucarnea recurvata (Bettaieb et al., 2008; Osorio-Rosales and Mata-Rosas, 2005; Reyes et al., 2013; Sajeva et al., 1994; Samyn, 1997), Beaucarnea gracilis (Osorio-Rosales and Mata-Rosas, 2005), and Beaucarnea inermis (Guillén et al., 2015), but to the best of our knowledge, there are no reports on in vitro propagation of B. purpusii.
In the pursuit of determining an efficient protocol for in vitro propagation of endangered species with low growth rates such as B. purpusii, it is necessary to study the effects of several PGRs at different concentrations on various explant types, with special interest to variables that have not been evaluated previously. Therefore, the present study attempts to provide an efficient protocol for in vitro propagation of B. purpusii from longitudinal sections of seedling using different concentrations of BA, Kin, and TDZ on semisolid media, as well as to evaluate the effects on the shoot formation of explants exposed to pulse treatments of higher concentrations of BA and TDZ.
Avila-FoucatV.S.Pérez-CampuzanoE.2015Municipality socioeconomic characteristics and the probability of occurrence of Wildlife Management Units in MexicoEnviron. Sci. Policy45146153
BairuM.W.StirkW.A.Van StadenJ.2009Factors contributing to in vitro shoot-tip necrosis and their physiological interactionsPlant Cell Tiss. Org. Cult.98239248
BoglerD.1998Nolinaceae p. 392–397. In: K. Kubitzki (ed.). The families and genera of vascular plants Vol. III. Flowering plants. Monocotyledons. Springer Berlin Heidelberg Germany
CassellsA.C.CurryR.F.2001Oxidative stress and physiological, epigenetic and genetic variability in plant tissue culture: Implications for micropropagators and genetic engineersPlant Cell Tiss. Org. Cult.64145157
ContrerasA.OsorioM.EquihuaM.BenítezG.2008Conservación y aprovechamiento de Beaucarnea recurvata especie forestal no maderable. Instituto de Ecología A.C. Cuadernos de Biodiversidad México. 28:3–9
García-MarmolejoG.Escalona-SeguraG.Van Der WalH.2008Multicriteria evaluation of wildlife management units in Campeche, MexicoJ. Wildl. Mgt.72511941202
GeorgeE.HallM.A.De KlerkG.J.2008Plant propagation by tissue culture Vol 1. The background. Springer Basingstoke UK
GoldfarbB.HoweG.BaileyL.StraussS.ZaerrJ.1991A liquid cytokinin pulse induces adventitious shoot formation from Douglas-fir cotyledonsPlant Cell Rpt.10156160
GolubovJ.MandujanoM.C.ArizagaS.Martínez-PalaciosA.KoleffP.2007Inventarios y conservación de Agavaceae y Nolinaceae p. 25–52. In: P. Colunga L. Eguiarte and A. Garcia (eds.). El género Agavaceae y Nolinaceae en México: Una síntesis del esatdo del conocimiento. Centro de Investigaciones Científicas de Yucatán CONACyT UNAM México
GuillénS.Martínez-PalaciosA.MartínezH.Martínez-ÁvalosJ.G.2015Organogénesis y embriogénesis somática de Beaucarnea inermis (Asparagaceae), una especie amenazada del noreste de MéxicoBot. Sci.932110
HernándezL.MartínezM.MaldaG.OsorioM.ContrerasA.OrellanaR.2009Las Patas de Elefante (Beaucarnea spp.) como recurso fitogenético disponible en México. Reporte final de Red Pata de Elefante. Instituto de Ecología A.C. Universidad Autónoma de Querétaro México
HernándezL.Osorio-RosalesM.OrellanaR.MartínezM.PérezM.ContrerasA.MaldaG.EspadasC.AlmanzaK.CastilloH.FélixA.2012Manejo y conservación de las especies con valor comercial de pata de elefante (Beaucarnea). 1st ed. Universidad Autónoma de Querétaro Querétaro México
IvanovaM.Van StadenJ.2011Influence of gelling agent and cytokinins on the control of hyperhydricity in Aloe polyphyllaPlant Cell Tiss. Org. Cult.1041321
KeversC.FranckT.StrasserR.DommesJ.GasparT.2004Hyperhydricity of micropropagated shoots: A typically stress-induced change of physiological statePlant Cell Tiss. Org. Cult.77181191
MadhulathaP.AnbalaganM.JayachandranS.SakthivelN.2004Influence of liquid pulse treatment with growth regulators on in vitro propagation of banana (Musa spp. AAA)Plant Cell Tiss. Org. Cult.76189192
NorizakuT.TanimotoD.HaradaH.1985Effects of wounding on adventitious bud formation in Torenia fournieri stem segments cultured in vitroJ. Expt. Bot.36841847
PelahD.KaushikA.MizrahiY.SitritY.2002Organogenesis in the vine cactus Selenicereus megalanthus using thidiazuronPlant Cell Tiss. Org. Cult.718184
Ramírez-MalagónR.Aguilar-RamírezI.BorodanenkoA.Pérez-MorenoL.Barrera-GuerraH.Núñez-PaleniusN.Ochoa-AlejoN.2008In vitro propagation of three Agave species used for liquor distillation and three for landscapePlant Cell Tiss. Org. Cult.94201207
SamynG.1997Micropropagation of Beaucarnea recurvata Lem. syn. Nolina recurvata (Lem.) Hemsl. (Ponytail Palm) p. 264–275. In: Y.P.S. Bajaj (ed.). High-tech and micropropagation VI Vol. 40. Springer-Verlag Berlin Heidelberg Germany
SarasanV.CrippsR.RamsayM.AthertonC.McMichenM.PrendergastG.RowntreeJ.2006Conservation in vitro of threatened plants—Progress in the past decadeIn Vitro Cell. Dev. Biol. Plant42206214