THE POTENTIAL OF INTERSUBGENOMIC HETEROSIS REALIZED WITH NEW-TYPE Brassica napus

¹ National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan 430070, People's Republic of China

In order to distinguish the same genome divergence from different species of Brassica oilseeds, a concept of subgenome was proposed, in which AⁿAⁿCⁿCⁿ, A^rA^r and B^cB^cC^cC^c have been designated for the genome composition of Brassica napus, B. rapa and B. carinata, respectively. After interspecific crosses of such three species and marker-assisted selection, a range of lines of new-type B. napus were developed, in which 53% of Aⁿ or AⁿCⁿ in average were substituted by A^r or A^rC^c subgenomic components. Such new lines were cross-pollinated with a wide range of cultivars of natural B. napus. Strong intersubgenomic heterosis was observed in small block experiments where 60% of intersubgenomic hybrids exceeded the elite cultivar and 25% of tested hybrids surpassed the elite commercial hybrid. The seed yield of intersubgenomic hybrids was positively and highly correlated with the genomic portion of A^r, C^c and A^r+C^c in new-type B. napus. Analysis on A^rAⁿCⁿCⁿ intersubgenomic hybrids shown that the interaction between A^r and Aⁿ subgenomes had a main contribution to the subgenomic heterosis. Further studies will focus on three points: to improve the new-type B. napus by increasing genomic components of A^rA^r or A^rA^rC^cC^c, to investigate the gene expression profile and to commercialize the intersubgenomic hybrids.