Association of RFLP markers and biomass heterosis in trigenomic hybrids of oilseed rape (Brassica napus x B-campestris)

Laboratory screening with DNA-based markers and field measurements of biomass production were carried out on each of the 120 trigenomic hybrids, obtained by interspecific hybridization between Brassica napus (AACC) and Brassica campestris (AW). The objective of this study was to elucidate the relationship between molecular markers and biomass heterosis of the interspecific hybrid between B. napus and B. campestris, which has been explored practically in rapeseed production for many years. The experiment was first carried out on 65 trigenomic hybrids in 1999. The average over-mid-parent heterosis of biomass production was around 30%, and the highest value was 175.4%. In the following year, the observation was expanded to 120 trigenomic hybrids and the best average over-mid-parent heterosis was 93%. A total of 1,477 DNA fragments, generated by Southern hybridization with 50 Brassica cDNA clones and 25 Arabidopsis EST clones, was scored across their parental lines. One hundred and twenty six and 215 fragments were identified as significantly associated with biomass production respectively in the 2 successive years. Using these active markers, a statistical model to resolve the heterosis is proposed and a new way to make use of the subgenomic heterosis is also discussed.