The Tip of the Iceberg: Cryopreservation Needs for Meeting the Challenge of Exceptional Plant Conservation

Abstract

Cryopreservation is increasingly important as a conservation tool, particularly for threatened exceptional species. The goal of this study was to investigate the current knowledge of plant cryopreservation through a search of the literature in Web of Science and align that with the 775 species currently identified on the Working List of Exceptional Plants. While there is a good foundation in plant cryopreservation research, particularly with economically important species, there are significant gaps in research on families that contain the largest numbers of currently known exceptional species, including the Dipterocarpaceae, Rhizophoraceae, and Pittosporaceae. Even families well represented in both in the literature and on the List of Exceptional Plants had much less overlap at the level of genus. Tropical trees, a significant portion of exceptional species, were not as well represented in the literature as herbaceous species. Over 70% of all articles dealt with in vitro cryopreservation, with much less emphasis on other methods (seed, embryo, dormant bud, and pollen) that will be more cost-effective for species where they can be applied. While the research on plant cryopreservation to date provides a strong foundation and is being utilized effectively for conserving the diversity of a number of economically important species, this study revealed significant gaps that can help prioritize future research to more effectively conserve the diversity of threatened exceptional species.

Critical Role of Regrowth Conditions in Post-Cryopreservation of In Vitro Plant Germplasm

“…Cryopreservation, i.e., the storage of viable material in liquid nitrogen (LN, −195.8 °C) or its vapor phase (−150~−195 °C), combined with in vitro technologies, offers a valuable option for the long-term conservation of plant species that are vegetatively propagated, with non-orthodox or limitedly available seeds [ 1 , 2 , 3 , 4 ]. In response to the urgent need for secure long-term conservation, collections of cryopreserved plant genetic resources have been established worldwide with capacities ranging from dozens to thousands of samples [ 5 , 6 , 7 , 8 , 9 , 10 ], and an increasing number of genebanks, botanic gardens, and scientific institutes have created cryobanks for their research and practical needs [ 11 ].…”

“…However, in vitro-derived materials are most useful for the cryopreservation of vegetatively propagated staple crops, ornamental varieties, or elite tree genotypes [ 13 , 14 , 24 ]. Cryopreservation of in vitro propagules may also help conserve threatened species without the available seeds for banking or with recalcitrant seeds that cannot be preserved as embryos [ 2 , 3 ]. Moreover, cryopreservation is the only reliable option for the long-term conservation of biotechnological collections of isolated cell and root cultures that exist only in vitro [ 15 , 16 , 25 , 26 ].…”

Cryopreservation of bioflavonoid-rich plant sources and bioflavonoid-microcapsules: emerging technologies for preserving bioactivity and enhancing nutraceutical applications

“…The same is true for sources of bioflavonoids that have been cryopreserved. Furthermore, scientists observed that some bioflavonoids are difficult to encapsulate and preserve because of their poor solubility in aqueous solutions ( 131 ).…”

The potential impacts of climate change on ex situ conservation options for recalcitrant-seeded species

“…Ex situ pollen conservation is a valuable alternative to overcoming the critical limitation of seed banking for safeguarding the germplasm of RS species (Pence and Bruns, 2022). By containing all the information of the haploid genome of the species, it is a way of conserving genes more than genotypes, and in this sense, its use should be thought of as a complementary way to the storage of other plant propagules (Grout and Roberts, 1995;Berthaud, 1997;Ren et al, 2019).…”