The function of seed banks is to extract and conserve the biological biodiversity of plants. To carry out this goal, it is important to be very sure of the identification of the material preserved, as well as their quality, too. High quality seeds can be conserved for a long time and they originate more vigorous plantlets.

The interaction of seeds, as a biological material, with the environment, conditions their quality. This quality depends on numerous factors like genetics, age, typology of management on the mother plant, climatic conditions, physiological conditions of the mother plant during its development, maturity at the moment of collecting, collecting method, etc. The description and a thorough knowledge of morphological, anatomical and physiological aspects of the seeds is very important, not only for a correct conservation, but also for a lasting utilization of the present resources in the bank. For this reason, it is essential to characterize the material, that is, to observe it, measure it and document the genetically transmissible features. Data obtained with this type of analysis allows us to identify and classify the accessions, and create, at the same time, a list of the essential descriptors for a knowledge of the collection. (Ferreira, M.E., 2005).

The seed represents a new organism, genetically different from its parents; this diversity is its strong point which enables it to overcome the difficulties of the environment and survive. Photo: seeds and plantlets of Astragalus verrucosus (© 2005 C. Pontecorvo - CCB).

At present, characterization of germplasm is based mainly on:

• Morphological descriptors: size, shape (circular, elliptical, linear, etc.), cross section (circular, compressed, plane, etc.), colour of the teguments, particular ornamentations (granulated, grooved, alveolus,etc.), teguments conformation, number of cotyledons, typology of embryos (peripheral, linear, puddle, etc.), place of accumulation of the reserve substances, etc. The morphological characterization, which is nowadays the method more often used and which presents the advantage of being the most economical since it is based on characters easy to study; it also has limits linked to the polymorphism present in nature, influences of the environment on the phenotipical characters of a species, and the subjectivity of interpretation of the parameters previously mentioned.
• Agronomical descriptors: useful especially for crops of economic importance; this typology of characterization is very expensive, it is not applicable on a large scale and does not yet allow us to proove the present phenotypes of agronomic interest in the accessions of a collection.
• Molecular methodologies: these analyse certain zones of DNA, called “molecular markers”. They are distinguished depending on the markers, from which we study polymorphism. Among the different markers, the micro satellites (SSRs) are normally considered to be the most effective; they allow the semi-automatic genetic location of a great number of accessions and, consequently, a more precise and faster characterization on a large scale of the material preserved in the bank. This technique, nowadays well developed, is revolutionizing the characterization of the germplasm.

The knowledge acquired from the characterization of germplasm allows us, among other things, to highlight evident the optimum strategies from the collecting of representative individuals, to choose the more adapted material for plant reproduction in the seedbed, and to improve the techniques of long term conservation (storage at low temperatures) of collections in the bank.