Broadening of Genetic Diversity in Spring Canola (Brassica napus L.) By Use of Brassica Rapa L.

Genetic diversity in Canadian spring Brassica napus L. (AACC, 2n = 38) canola has declined in the last years due to intensive breeding carried out within the restricted gene pool. Winter and Chinese semi-winter type B. napus and its parental species B. rapa L. (AA, 2n = 20) and B. oleracea L. (CC, 2n = 18) are genetically distinct from spring type B. napus. Some efforts have been made to broaden genetic diversity and productivity of spring canola by use of winter and Chinese semi-winter types; however, very limited efforts made to utilize genetic diversity of its allied species as interspecific cross often introduce many unwanted alleles and cause meiotic abnormalities in the segregating population. Introgression of these unwanted alleles can be avoided by increasing selection pressure as well as through limited backcross approach. A breeding research was undertaken to broaden the genetic base of the Canadian spring B. napus canola through introgression of distinct alleles from B. rapa. For this, interspecific hybridization between B. napus and B. rapa were done and pedigree breeding was followed to develop canola quality euploid B. napus lines. Agronomic and seed quality traits such as silique length, number of seeds per silique and seed glucosinolates content, and ploidy level of the interspecific crosses derived populations was assessed in different generations. Repeated selection has improved plant fertility and seed quality traits in F₆ generation. Flow cytometric analysis of ploidy level revealed that many F₆ families were similar to B. napus.

Key Words: Brassica napus, Brassica rapa, genetic diversity, interspecific cross, spring canola