New Approaches for Micropropagation and Cryopreservation of Agave Peacockii, An Endangered Species

More than 50% of Agave species are endemic to Mexico. Among them, Agave peacockii is listed within the list of threatened species that require special protection. In this work, we aimed at developing new supplementary strategies to achieve micropropagation and perform cryopreservation of in vitro-grown shoot-tips of A. peacockii. For multiplication, the addition of two cytokinins, 6-benzylaminopurine (26.6 μM) and kinetin (27.84 μM) to MS semisolid medium significantly favoured the morphogenetic response and produced the highest shoot generation (87.00±17.18) after 60 d of culture. This interaction was more effective than using the same growth regulators separately. Propagated and rooted plantlets were successfully acclimated with 100% survival and a normal morphological development during greenhouse performance. For cryopreservation, an optimized protocol following droplet-vitrification approach allowed obtaining 98% and 96% regrowth before and after cryopreservation, respectively. Shoot-tips were excised of in vitro-propagated plants, subjected to preculture on MS semisolid medium with 0.3 M sucrose for 1d, loaded in solution with 0.4 M sucrose and 1.6 M glycerol for 20 min, exposed to vitrification solution PVS2 for 15 min, and then, immersed in liquid nitrogen in droplets of PVS2 placed on aluminium foil strips. The vegetative growth of cryo-derived plants and of the in vitro propagated plants was compared under greenhouse culture conditions. No significant differences were detected in most assessed characteristics after 120 d of acclimatization. The results presented here constitute new viable biotechnological approaches for the in vitro propagation and long-term conservation of endangered Agave germplasm.

Greenhouse Culture and Production of Four Ornamental Native Wetland Plants

Wetland restoration is an important way to improve ecosystem services, but many wetland nurseries lack the facilities that are traditionally used to produce large numbers of native plants used in these projects. Our goal was to evaluate growth and performance of four wetland species in a variety of substrates, fertilizer regimes, and irrigation methods under greenhouse conditions. Plants were grown in pots with drainage holes filled with one of four substrates (potting substrate, topsoil, sand, 50/50 mix of topsoil, and sand) amended with 0, 1, 2, or 4 g of 15N–3.9P–10K controlled-release fertilizer per liter of substrate. Irrigation was supplied via an overhead system or subirrigation. After 16 weeks of production, plants were scored for visual quality and plant height before a destructive harvest. Broadleaf sagittaria (Sagittaria latifolia) was mostly unaffected by substrate type but performed best when subirrigated and fertilized with 4 g·L−1 of fertilizer. Growth of skyflower (Hydrolea corymbosa) and cardinal flower (Lobelia cardinalis) was best when fertilized with 2 or 4 g·L−1 of fertilizer and grown using overhead irrigation. String lily (Crinum americanum) was unaffected by substrate type but produced the largest plants when subirrigated. These experiments provide guidance for cultivating these wetland species under greenhouse conditions, which may allow growers to efficiently produce plant material needed for the restoration market.

STORAGE TIME EFFECT ON MINI-CUTTINGS ROOTING IN Tectona grandis LINN F. CLONES

ABSTRACT The study aimed to evaluate the influence of storage length on Tectona grandis mini-cuttings survival and rooting. A factorial arrangement (4 x 7) was utilized, based on four clones (Carapá, Ipê, GU5 and TB7) and seven time intervals from mini-cuttings harvesting until final sowing (0, 1, 2, 4, 8, 12 and 16 hours). A randomized block design with three replicates and 16 mini-cuttings per experimental unit was utilized. Survival and rooting rates were evaluated after greenhouse culture (30 days after sowing) and after shadow house culture (40 days after sowing); as well as height, collar diameter, aerial and root biomass 55 days after sowing. No significant differences were observed in survival and rooting rates among time intervals in teak mini-cuttings preparation from these four clones. However differences among clones were registered for rooting rate, suggesting a genotypic effect. Survival and rooting rates were very high after greenhouse culture (93% and 90% respectively), as well as survival after culture in a shadow-house (88%).