Abstract
Conventional dry seed storage is unlikely for about one third of all tree species (and nearly half of evergreen rain forest trees) as they probably produce desiccation sensitive (recalcitrant) seeds. Consequently, international ex situ conservation targets for threatened trees will be difficult to achieve without innovation, especially in cryobiotechnology. We assessed progress in the development of various cryobiotechnology approaches for the preservation of oaks (Quercus), which are keystone species of functioning landscapes, important to the bioeconomy and under increasing threats from the spread of pests and diseases under a changing climate. Various tissues of oaks can be used for banking, from pollen grains to embryo axes. Pollen from five oak species have been shown to be highly desiccation tolerant, making dry pollen storage at low temperatures (including in liquid nitrogen) a valuable technology to support conservation and breeding programs. Somatic embryo (SE) technology and/or shoot tip in vitro technology is available for 39 species, and SE cryopreservation is routinely performed on three commercial species and shoot tips cryopreservation successful in two more species. Seed embryonic axes are the preferred explants for oak ex situ conservation, with tissue survival and regeneration of plants after cryopreservation recorded for 14 and seven species respectively; although differential responses between the shoot and root meristems in the axes are known. Dormant bud preservation seems promising, but is under-researched. Overall, these results indicate the possibility of establishing an integrated platform for the ex situ conservation of oak species based on cryobiotechnology. Challenges of explant choice, optimization of methodologies and large-scale application do remain. However, multiple approaches for the cryopreservation of oak genetic resources are available and implementation programmes should not be delayed, particularly in the centres of species diversity.
Highlights
Trees are anchors of the forest, providing crucial resources for shelter, food and medicines and supporting livelihoods
The conclusions we make about progress on the cryobiotechnology of oaks should help with the development of appropriate strategies for the long-term ex situ conservation of other taxa, those with low or nil representation in ex situ conservation programmes, whether threatened and/or recalcitrant seeded [1,9]
Long term cryopreservation of pollen can play a vital role when resurrecting genotypes that have been lost to disease, as it was the case of Castanea dentata trees, which pollen was stored for over 20 years in liquid nitrogen (LN) and successfully used to produce seeds in extant
Summary
Trees are anchors of the forest, providing crucial resources for shelter, food and medicines and supporting livelihoods. With respect to the preservation of the genetic resource, the different tissues provide various options for the haploid and diploid genome, and the paternal and maternal lines This has made the large-scale long-term ex situ conservation of tree genetic resources a reality for a wide range species with economic and food value, such as fruit trees, and forestry and plantation species [12,14,15,16]. The conclusions we make about progress on the cryobiotechnology of oaks should help with the development of appropriate strategies for the long-term ex situ conservation of other taxa, those with low or nil representation in ex situ conservation programmes, whether threatened and/or recalcitrant seeded [1,9]. Understanding the interspecies variability in the response to hydrated storage at low temperatures may be important to find stress tolerance biomarkers (e.g., ecological, structural, genetic and molecular) that may hold some lessons for the optimization of the design of cryopreservation strategies
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
