Pyramiding of multiple genes generates rapeseed introgression lines with clubroot and herbicide resistance, high oleic acid content, and early maturity

Clubroot and herbicide resistance, high oleic acid (OA) content, and early maturity are targets of rapeseed (Brassica napus L.) breeding. The objective of this study was to develop new male-fertility restorer lines by pyramiding favorable genes to improve these traits simultaneously. Seven elite alleles for the four traits were introduced into the restorer line 621R by speed breeding with marker-assisted and phenotypic selection. Six introgression lines (ILs) were developed with four- to seven-gene combinations and crossed with two elite parents to develop hybrids. All ILs and their corresponding hybrids displayed high resistance to both clubroot pathotype 4 and sulfonylurea herbicides. Three ILs and their hybrids showed large increases in OA contents and four showed earlier maturity. These new ILs may be useful in rapeseed hybrid breeding for the target traits.