Germplasm conservation of rare and threatened plant species

摘要

Ex situ conservation techniques are basic elements in a global conservation program. They essentially consist of germplasm storage and propagation operations. Storage is performed through the maintenance of plant collections in botanical gardens andthe establishment of germplasm banks. Among the different types of germplasm banks, seed banks are the simplest and most efficient alternative for the storage of species with orthodox seeds. These seeds can also be stored using cryopreservation techniques. The storage of recalcitrant seeds is more troublesome due to their sensitivity to desiccation and in vitro banks can be an alternative to seed banks when seed storage is not feasible. DNA stocks, pollen banks and bud banks are other possibilities forstorage scarcely used yet. Seed multiplication is the most frequent method of propagation. However, the dormancy displayed by many seeds of wild plant species often reduces the efficiency of this method significantly. When seed propagation is not feasible or there is an interest in the propagation of a particular genotype, conventional techniques of vegetative multiplication or micropropagation techniques can be used. Micropropagation techniques are attractive due to its high multiplication rates and the reduced amount of starting material that is required. Nevertheless, significant problems can arise to reproduce the stored genetic diversity of one species and maintain its genetic integrity.