In order to ensure stable or increasing yields, plant breeders continuously strive to develop crops that are resistant against pests and diseases and well-adapted to changing climatic or regional conditions. New varieties occur on the market and old varieties cease to be cultivated. Varieties which are no longer cultivated extensively are threatened by genetic erosion.
In order to give a comprehensive overview of the genetic diversity of our crops, the National Inventory provides information about varieties that have disappeared from cultivation as well as on currently cultivated species and varieties. For all species listed in the Seed Trade Act (SaatG), relevant information is available from the Federal Office of Plant Varieties (even retrospectively for a certain period of time).
In connection with agricultural statistics data on the cultivation of the main crops are collected by means of the main land use survey (re. cultivation areas, a full survey is conducted every 4 years, while in the years in-between, data are based on a sample of 20% of all businesses). These data are stored at the Federal Statistical Office (up to federal state level) or at the statistical offices (up to district level).
Cultivation areas for less important species are not mentioned separately but rather listed in groups (e.g. other oil seed crops). In many cases, region-specific information on the extent of cultivation of varieties is missing. Details on the most widely grown varieties of cereals and potatoes are available from the Special Evaluation of Crops (BEE). Cultivation dispersal within a species (variety level) can be derived indirectly from the registered fields, i.e. seed propagation areas.
Data on varieties cultivated provide information on the genetic diversity of crop rotation. Over a given period of time, changes regarding the diversity within a species (genetic diversity) can be observed.