Within the framework of Bioenergy ERA-NET the project aims at building a sustainable increase in mass yield (yield/space/time) of willow clones used in short rotation coppice (SRC) with rotation periods of 2 to 5 years. The focus is on the breeding of new varieties and the testing of varieties which are not yet registered. In addition to S. viminalis other species like S. phylicifolia, S. fragilis, S. alba, S. caprea, S. dasyclados and S. purpurea as well as hybrids of these species (eg. S. x helix) will become subjects of the investigations. In particular, the techniques of rapid propagation (cloning) of promising clones will be tested, as for field tests under different environmental conditions a large number of plants needs to be examined and planting of 13 to 18,000 cuttings per hectare is a prerequisite for the mechanized management of SRC. Genetic methods in conjunction with the describtion of morphological characters are tested in order to differentiate between species, hybrids and clonal varieties. The working program includes: 1.Evaluation of existing clone collections in Germany - 2. Cooperation with European partners in ERA-Net/BREDNET SRC - 3. Consultance and cooperation with 3-N Niedersachsen regarding field experiments - 4. Development of methods of micropropagation in cooperation with Biotec Oberdorla Ltd. - 5. Genetic characterization of species and clones in cooperation with Univ. Marburg - 6. Collection of flowering twigs and germploasm in natural willow populations. - 7. Breeding (intra- and interspecific crossing) - 8. Reestablishment, enlargement and maintenance of breeding collections, - 9. Establishment of a virtual collection/ data base (clonal description).