Abstract
Endemic plant species are usually more vulnerable to anthropogenic threats and natural changes and, therefore, hold a higher extinction risk. The preservation of these species is a major concern on a worldwide context and in situ protection alone will not guarantee their conservation. Ex situ conservation measures must be undertaken to support the conservation of these species, and seed banking is the more efficient and cost-effective method. However, when seed banking is not an option, alternative approaches should be considered. Biotechnological tools provide new and complementary options for plant conservation including short-, medium-, and long-term strategies, and their application for plant species conservation has increased considerably in the last years. This review provides information about the status of the use biotechnology-based techniques for the conservation of endemic plant species. Particular attention is given to cryopreservation, since is the only long-term ex situ conservation strategy that can complement and support the other conservation measures. The cryopreservation of plant genetic resources is, however, more focused on crop or economically important species and few studies are available for endemic plant species. The plant material used, the cryopreservation methods employed, and the assessment of cryogenic effects are reviewed. The reasons to explain the difficulties in cryopreserving these species are discussed and new strategies are proposed to facilitate and increase the interest on this matter. We expect that further studies on the conservation of endemic plant species will increase in a near future, thus contributing to maintain these valuable genetic resources.
Highlights
Endemic plant species are usually more vulnerable to anthropogenic threats and natural changes and, hold a higher extinction risk
An endemic species can be defined as a species that occurs naturally and exclusively, and it is highly adapted to a specific geographic area [6,7,8,9]
Slow growth storage is a strategy for the medium-term conservation of in vitro plant germplasm with the objective of reducing plant growth and, the number of sub-cultures required without affecting the viability of the explants
Summary
Plants are vital for life on earth and a crucial element in all ecosystems. Despite their importance, all over the world, plant biodiversity is at risk and every year the number of threatened species increases dramatically [1]. The loss of natural populations or even entire species is usually related to the destruction and alteration of their habitats, as a consequence of human overexploitation, and more recently, pollution, and climate changes, leading to the loss of genetic diversity [2,3,4] Many of these species are endemic, unique, and often only a few and small wild populations resist [4,5]. Plants 2020, 9, 345 one or few populations, small population size, declining population size, excessive collection by humans, short reproduction capacity, specific habitat conditions, and necessity of stable and constant environments The more of these characteristics these species display, the more vulnerable they are to extinction [9]. There are others that, even though they can produce seeds, are highly heterozygous For these plant species, the traditional ex situ conservation method is in the form of field collections [14,17]. In addition to traditional conservation methods, it is necessary to implement complementary strategies to augment the chances of survival even for species with orthodox seeds that are preserved in seed banks
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