Figure 1.

The U's triangle of Brassica presenting the cytological relationship of the relation species and their subgenome constitution. This picture is cited from Zou et al. (2010), which was modified according to UN (1935). The diploid species with the three basic subgenomes (A,B,C) are presented in the three corner of the triangle, and the derived three tetraploid species are presented in the middle of the three lines. Different subgenomes of different species are noted with the superscript of the first letter of each species (Zou et al., 2010).