The progress of intersubgenomic heterosis studies in Brassica napus

The new nomenclature of Brassica has been suggested in a previous study by same authours where the symbols of A r , A j and A n represented the A genome in the Brassica rapa, Brassica juncea and Brassica napus , B b , B j and B c for the B genome of Brassica nigra (black mustard), B. juncea and Brassica carinata, C o , C n and C c for the C genome of Brassica oleracea, B. napus and B. carinata . Numerous efforts have focused on exploring novel B. napus (A n A n C n C n ) breeding stocks by the hybridization between Brassica species. Thereafter, most interspecific hybrids in Brassicas could be considered as intersubgenomic hybrids. In this review, examples are shown from recent studies on the method for construction of new-typed B. napus with genome composition of A r A r C c C c and A r A r C n C n , the meiosis and embryo sac development of new-typed B. napus, the appearance of intersubgenomic (A n A r C n C c and A r A n C n C n ) heterosis and the mechanism for production of intersubgenomic heterosis were described.