The human species depends on plants. These constitute the basis for food, supply most of our needs (including clothes and shelter) and are used in industry for manufacturing fuels, medicines, fibres, rubber and other products. However, the number of plants that humans use for food is minimal, compared to the number of species existing in nature. Only 30 crops, the most outstanding of which are rice, wheat and maize, provide 95% of the calories needed in the human diet (Jaramillo & Baena, 2002). However, agricultural biodiversity is in sharp decline due to the effects of modernisation, such as concentration on a few competitive species and changes in diets. Since the beginning of agriculture, the world’s farmers have developed roughly 10 000 plant species for use in food and fodder production. Today, only 150 crops feed most of the world’s population, and just 12 crops provide 80% of dietary energy from plants, with rice, wheat, maize and potato providing 60%. It is estimated that about three quarters of the genetic diversity found in agricultural crops have been lost over the past century, and this genetic erosion continues (EC, 2007).

Humans need to add to their diet those crops of high yield and quality that can adapt to environmental conditions and resist pests and diseases. Advantage must be taken of native and exotic species, with nutritional or industrial potential, or new varieties must be developed. Improving crops, however, requires reserves of genetic materials whose conservation, management and use have barely begun to receive the attention that they deserve. Humans take advantage of plant genetic resources in as much as they are useful to us, which means that we must understand them, and know how to manage, maintain and use them rationally (Jaramillo & Baena, 2002). Information on genetic diversity and relationships within and among crop species and their wild relatives is essential for the efficient utilization of plant genetic resource collections for the efficient explanation of taxonomic relationships (Chan & Sun, 1997; Drzewiecki et al., 2003).