Location: Plant Germplasm Preservation ResearchTitle: Preservation of recalcitrant seeds) Author
Submitted to: Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/1/2012
Publication Date: 2/22/2013
Citation: Walters, C.T., Berjak, P., Pammenter, N., Kennedy, K., Raven, P. 2013. Preservation of recalcitrant seeds. Science. 339:915-916. Interpretive Summary: Seed storage behaviors are divided into categories of orthodox, intermediate, and recalcitrant. Recalcitrant seeds, as their label implies, cannot be stored under typical seed banking conditions, because they are killed immediately when placed in the freezer (i.e., conventional storage). Plants that produce seeds in this category are oaks and palms, and many of our favorite tropical fruits such as citrus, avocado, lychee and cacao. Cryogenic principles, routinely applied to many other germplasm forms – plant and animal, alike – are applicable to recalcitrant seeds as well, and permit genebanking of these species, many of which have critical economic or ecological importance and are at risk as a result of spreading diseases. Unlike many seed banks around the world, the USDA-ARS National Center for Genetic Resources Preservation has cryogenic storage capacity, and this infrastructure permits needed ex situ conservation efforts to move forward.
Technical Abstract: Recalcitrant and intermediate seeds are not included in seed banks because of misperceptions that these efforts would be futile. Between 20 and 25% of the Earth’s angiosperm species are estimated to produce recalcitrant or intermediate seeds. These species are more prevalent in the tropics and subtropics compared to temperate climates that tend to have higher proportions of annual species that produce “orthodox” seeds. Orthodox seeds readily survive conventional freezer storage in genebanks and most genebanks were designed to accommodate only this category of seeds. Cryogenic technologies are making it increasingly possible to conserve genetic diversity of species producing non-orthodox seeds. Hence, seed bank infrastructure, rather than seed post-harvest physiology, is the factor most limiting progress towards ex situ conservation in tropical and subtropical regions of the world.