• A total of 79, 145 SSR loci were identified from the whole genome of Brassica rapa var. rapa (ECD04), and 52, 471 pair primers of SSR have been successfully designed. • BraSSR45619E4 was identified and located at a genetic distance of 5. 02 cM from the CR gene locus. It is the first-ever identified CR molecular marker located on A09 chromosome in B. rapa. • In the backcross progenies, most of individuals carrying the resistance bands consistently displayed sustained resistance to clubroot disease. BraSSR45619E4 is stable and reliable in marker-assisted breeding. Clubroot disease in cruciferous crops, caused by the obligatory parasite Plasmodiophora brassicae Woronin. Due to the wide and rapid spread of the pathogen, the yield of infected crops has been progressively declining. Simple sequence repeats (SSRs), which are known for their high polymorphism, wide distribution, and easy detection methods, are widely used in plant molecular breeding. In this study, a total of 79, 145 SSR loci were identified from the whole genome of the clubroot resistant germplasm Brassica rapa var. rapa (ECD04), and 52, 471 pairs of primers have been successfully designed. A subset of these primers was tested for their transferability across cruciferous crops. 229 primer pairs were selected to screen the polymorphisms between clubroot-resistant and clubroot-susceptible gene pools. The SSR marker, BraSSR45619E4, closely linked to clubroot resistance (CR), was identified through validation of F 3 generation individual plants. This marker is located on chromosome A09, at a genetic distance of 5. 02 cM from the CR gene locus. Additionally, a cross was performed between Pak choi (B. rapa ssp. chinensis) and clubroot-resistant turnip, followed by seven successive backcrosses. In the backcross progenies, most of individuals carrying the resistance bands consistently displayed sustained resistance to clubroot disease. To the best of our knowledge, BraSSR45619E4 is the first-ever identified clubroot-resistant molecular marker located on A09 chromosome in B. rapa. This novel discovery provides a valuable and efficient tool for marker-assisted selection, for CR in cruciferous Pak choi, and offering an efficient tool for future CR breeding in the future.
Yu et al. (Sun,) studied this question.