Ex-Situ Conservation of Endangered Succulent Plants Using Cryobiotechnology Tools: The Aloe and Agave Cases

Josette Tin, Taylor La Val, Sean Lahmeyer, John Trager, Raquel Folgado*, The Huntington Library, Art Collections and Botanical Gardens, San Marino, CA., United States, *Speaker

Succulent plants are significant to the horticultural industry, and they are also sources for food, fibers, medicines, and cosmetics. The main threats for the wild population of these often emblematic plants are human activities, such as over-collection in the wild. The Huntington Desert Garden holds one of the largest ex-situ collections of succulent plants. Besides the traditional propagation methods for the field collections and the cryopreservation of seeds, in vitro repositories have been created to assure the preservation of the clonal type plants, which often have historic and botanical value. Experiments of droplet-vitrification based techniques have been used to cryopreserve clonal accessions of aloes and agaves. Apical shoot tips of 1 mm size from 5-week- old in vitro plantlets (aloe or agave) were exposed to loading solution for 20 min at room temperature, dehydrated with Plant Vitrification Solution 2 (PVS2) for different times (from 0 to 90 min) at 0 °C, transferred to aluminum foil strips and directly plunged into liquid nitrogen. For re-warming, aluminum strips were rinsed in unloading solution for 20 min at room temperature. Explants were transferred to regeneration media and kept in the dark for one week. In additional experiments, shoot-tips excised from donor plants pretreated onto a sucrose- enriched medium for two weeks were also submitted to cryoprocedure. The pretreatment with sucrose- supplemented medium improved the regeneration of both aloe and agave cryopreserved explants. The optimized protocols that have been developed for Aloe fievetii and Agave sobria spp frailensis (70 % and 90 % of plants recovered after cryopreservation, respectively) are being tested for other Aloe and Agave species. Regenerated plants were acclimated to ex vitro conditions.

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