Broadening the genetic base of the C genome of Brassica napus L. canola is needed for continued improvement of this crop. For this, we developed few hundred canola lines from B. napus × Brassica oleracea L. interspecific crosses involving a B. napus canola line and six B. oleracea accessions belonging to four varieties, viz. vars. alboglabra, botrytis, capitata, and italica, and following two breeding methods [F₂ and BC₁ (F₁ × B. napus) derived lines]. The objective of this study was to understand the genetic structure of this population regarding the alleles introgressed from B. oleracea by using simple sequence repeat markers and to investigate the inheritance of B. oleracea alleles in these reconstituted canola lines. Marker analysis showed that the four B. oleracea varieties were genetically quite distinct. Several canola lines derived from these six crosses tended to group together with their B. oleracea parent demonstrating that the wide diversity of the B. oleracea gene pool can be exploited for broadening the genetic base of the C genome of B. napus canola. Loss of several B. oleracea alleles occurred during the development of these inbred lines. While comparing the two breeding methods for introgression of B. oleracea alleles, significantly greater loss of alleles occurred in the F₂-derived population as compared with the BC₁-derived population. Thus, the knowledge from this study can be used for efficient introgression of exotic alleles from B. oleracea into B. napus for broadening the genetic base of this crop.