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The genetic basis of Brassica napus is narrow because its short evolutionary history,no wild species,poor cytoplasm diversity,monotonous breeding objects,and founders effects due to shared parents from low erucic acid germplasm ORO,low glocosinolates Bronowski.Because of narrow genetic basis and inbreeding effect,the yield of new varieties has stepped into the plateau stage during the last decade in China.In order to enlarge the genetic basis of Brassica napus,B.rapa and B.olearea were utilized to resynthesize B.napus and then a large quantity of recombined inbred lines (R-RILs) were produced through crossing between different resynthesized lines of B.napus,followed by successive self-hybridization.