Plant genetic resources describe the variability within plants that comes from human and natural selection over millennia. Their intrinsic value mainly concerns agricultural crops (crop biodiversity). According to the 1983 revised International Undertaking on Plant Genetic Resources for Food and Agriculture of the Food and Agriculture Organization (FAO), plant genetic resources are defined as the entire generative and vegetative reproductive material of species with economical and/or social value, especially for the agriculture of the present and the future, with special emphasis on nutritional plants.