Conserving orthodox seeds of globally threatened plants ex situ in the Millennium Seed Bank, Royal Botanic Gardens, Kew, UK: the status of seed collections

Abstract

We reviewed the status of orthodox seed collections of globally threatened plants conserved in − 20 °C long-term storage at the Millennium Seed Bank, Royal Botanic Gardens, Kew, UK in terms of their geographic and bioclimatic representativeness, taxonomic and genetic diversity, quality and physiological status. The comprehensive dataset used spans over 45 years of worldwide conservation effort across various organisations. The data provides evidence-based results and future directions for the represented globally threatened flora that are of relevance to all plant conservation and seed banking organisations across the globe. The reviewed sample includes 523 collections and represents a wide geographic range, originating from 67 countries, from all nine bio-geographic continents. The majority of collections originated from temperate climates and from habitats with no dry seasons but experiencing warm summer periods. The taxonomic composition of the collections highlighted a substantial diversity, with 303 taxa (four extinct in the wild; 56 critically endangered; 105 endangered; and 138 vulnerable) represented by 297 species, 199 genera and 74 families. Almost four fifths of the collections were harvested from wild habitats. Whilst wild-origin collections can harbour useful genes not available in the cultivated gene pool, for threatened plants both collections and taxa are likely to suffer from low genetic diversity as a low number of individual plants, populations and/or potentially viable or usable seeds were sampled at the original harvest. Large numbers of empty and infested seeds in the original harvest have significantly affected the quality of collections in terms of availability of potentially viable or usable seeds in collections. As a result, just over one third of taxa and one fifth of collections consisted of ≥ 5000 potentially viable or usable seeds. Viable seeds exhibited a sound physiological status in terms of germinability and viability at the initial round of germination tests after storage, but on average, relative germination and viability achieved were below 85%. A decline in germinability during their variable time of storage was evident for 16% of the 78 collections analysed for longevity. According to a set of criteria, suitable germination protocols for propagation of plants from seeds were identified for 165 taxa. Given the apparent differences between wild species, especially those that are rare and threatened, and domesticated crops, the quality and physiological status of reviewed collections are reasonably sound. The characteristics we observed for collections, the challenges we identified for conserving them and the germination protocols we suggested for propagation of plants from seeds have the scope to be noted, integrated and used globally across various conservation activities and policies.

Time‐traveling seeds reveal that plant regeneration and growth traits are responding to climate change

“…Long‐term storage could lead to a reduction in dormancy through time (as seen in Pérez‐García et al 2007 and González‐Benito et al 2011) and this might lead to historic seeds having higher germination. Storage effects could also act to decrease the viability, germination success, or fitness of historic seeds (Liu et al 2020). However, although storage effects could affect the elevation of the amount of change in relation to change in climate, they will not affect the slope of the relationship (Fig.…”

Corrigendum to: A handbook for the standardised sampling of plant functional traits in disturbance-prone ecosystems, with a focus on open ecosystems

“…Germination trails can be conducted using 25-50 seeds replicated five times, using seeds that were produced within the same growing season (less than 6 months old). Seeds should be sown onto 1% aqueous agar in plastic Petri dishes and incubated at a warm temperature of~25 C (savanna seed thermal niches commonly vary between 20 and 35 C) and exposed to a 12 h light-12 h dark photoperiod (Choinski and Tuohy 1991;Baskin and Baskin 1998;Stevens et al 2014;Liu et al 2020). To test whether dormancy is present, compare the germination rates of untreated to treated seeds germinating in agar.…”

A handbook for the standardised sampling of plant functional traits in disturbance-prone ecosystems, with a focus on open ecosystems

“…The most common way to record dormancy is to measure it through the absence of germination (Finch-Savage and Leubner-Metzger 2006). Whereas a full range of dormancy-breaking protocols utilised by the Millenium seedbank are listed and described in Liu et al (2020), for open ecosystems, we propose that treatments associated with drivers of these ecosystems will show how strongly these species can be filtered from the community. Germination trails can be conducted using 25-50 seeds replicated five times, using seeds that were produced within the same growing season (less than 6 months old).…”

“…Germination trails can be conducted using 25-50 seeds replicated five times, using seeds that were produced within the same growing season (less than 6 months old). Seeds should be sown onto 1% aqueous agar in plastic Petri dishes and incubated at a warm temperature of~25 C (savanna seed thermal niches commonly vary between 20 and 35 C) and exposed to a 12 h light-12 h dark photoperiod (Choinski and Tuohy 1991;Baskin and Baskin 1998;Stevens et al 2014;Liu et al 2020). To test whether dormancy is present, compare the germination rates of untreated to treated seeds germinating in agar.…”