Effectively widening the gene pool of oilseed rape (Brassica napus L.) by using Chinese B-rapa in a 'virtual allopolyploid' approach

P>Brassica rapa (AA), which has a high level of genetic diversity, has been used to widen the genetic base of oilseed rape (B. napus L., AACC). However, the differences in the degree to which the genetic base of oilseed rape can be widened using different forms of B. rapa have not been well characterized. We used a strategy of virtual allopolyploid to investigate the genetic differences between the A subgenome of natural oilseed rape and different ecotypes of B. rapa. In this strategy, the genetic characteristics of the virtual allopolyploid lines are deduced from the genotypes of the parental lines which are established using molecular markers, without the need for interspecific hybridization. Three genotypes of B. oleracea and 56 accessions of B. rapa which originated from Europe, China and India were genotyped using simple sequence repeat markers, together with nine oilseed rape lines representing spring, semi-winter and winter types. The genotypes of 168 virtual allopolyploid lines were derived from those of the parental lines and compared with those of the natural oilseed rape lines. Our data revealed that the virtual allopolyploid lines that were derived from Chinese semi-winter B. rapa showed substantial genetic variation from natural oilseed rape. This indicates that Chinese semi-winter B. rapa can be used effectively to broaden the germplasm of oilseed rape.