We are developing a large population of Fast Neutron Bombardment (FNB)-induced deletion mutants of Medicago truncatula Jemalong A17, in collaboration with Dr. Giles Oldroyd at the John Innes Center, UK. Together, we have generated an M2 population from ~146,000 M1 lines. From mutant screening workshops involving groups from USA and Europe in 2008, 2009 and 2010, we have identified many morphological and symbiotic mutants in the M2 generation. Photographs and phenotypic description of the mutant lines are presented here. Please note that phenotypic characterization and confirmation will be carried out in the M3 generation.