Abstract:Moricandia is the only genus with C3-C4 species within the family of Cruciferae. To provide the basic information of transferring C3-C4 and other important characteristics from Moricandia to Brassica crops, the relationships between Moricandia and Brassica species were studied based on crossability and RFLP fingerprinting. The crossability was very low between the two genera in the experiment. There was no hybrid seed obtained between M. arvensis and B. rapa though 8 000 flowers were crossed. 2 989 cross-pollinated ovaries were cultured and also no hybrid embryo was developed. However, four intergeneric hybrid shoots were generated from 105 cultured ovaries in the combination of M. arvensis x B. napus. The nucleus DNA polymorphism of restriction loci was detected with 23 genic DNA clones of B. napus for the samples of B. napus, B. rapa and B. oleracea, M. arvensis and M. nit, ns. A high homology was found between Moricandia and Brassica species. The similarity between M. nitens and B. rapa was even greater than that between B. rapa and B. napus. The close relationships between Moricandia species and Brassica crops, especially European B. rapa, were also detected with 4 beta mitochondria probes. The intensive homology between Moricandia C3-C4 species and Brassica crops evaluated with the RFLP markers revealed the possibility of transferring some important genes from the C3-C4 species to the domesticated species by sexual hybridization or protoplast fusion followed by recombination of homoeologous chromosomes.