Focus on developing introgression lines, chromosome alien addition lines, chromosome translocation through interspecific hybridization of tetraploid/tetraploid or tetraploid/diploid species. The pipeline for germpalsm enhancement has been set up, including embryo rescuing techniques for 3 DPA hybrid embryos to overcome interspecific incompatibility, cytogenetic and molecular cytogenetic techniques for alien chromosome identification, molecular marker-assistant selection and characterization of alien chromosome segments. So far, Gossypium barbadense-introgression lines have been developed involved in fiber quality, yield and resistances to Verticillium wilt. A complete set of alien chromosome addition lines from Gossypium australe in Gossypium hirsutum were constructed. Several chromosome translocation lines between Gossypium hirsutum and Gossypium australe have been identified. And various new synthetic amphiploids of hexaploid and tetraploid are obtained.