**10. Transferring clubroot resistance through molecular marker-assisted selection in canola**

Canola is one of the most important oilseed crops, and clubroot disease becomes a major limiting factor in canola production worldwide [102]. To develop resistant canola cultivars, several resistant sources such as European turnips, Chinese cabbage, and rutabaga cultivars are available and the resistance in these sources are dominant, which makes it easier to transfer clubroot resistance through interspecific and intraspecific hybridization. Rutabaga cultivars have been identified as clubroot-resistant sources [66, 67, 69]. However, the genetics of clubroot resistance in rutabaga is complicated so it is difficult to develop molecular markers that are closely linked to the dominant clubroot resistance genes.

In Chinese cabbage, the dominant clubroot resistance from European turnips has been successfully used to develop clubroot-resistant Chinese cabbage. Since the gene mapping has been performed extensively in Chinese cabbage, molecular markers closely linked to clubroot resistance loci that are used in gene mapping can be easily selected to transfer clubroot resistance genes in the development of Chinese cabbage cultivars through molecular markerassisted selection. Since canola, the amphidiploid *B. napus*, has a very complex genome, most of the molecular markers developed in *B. rapa* may not be polymorphic and cannot be directly used in canola. Additional efforts are required to develop molecular markers in canola when the mapped clubroot resistance loci in Chinese cabbage are transferred into canola. Currently, most clubroot resistance genes in European turnips have not been intensively investigated and mapping and cloning of these clubroot resistance genes in European turnips will allow using these genes effectively and efficiently in canola breeding.


**Table 1.** Clubroot resistance QTL/gene mapped/fine mapped in different Brassica species by different research studies
