Genetic relationship and diversity among some Moroccan and introduced rapeseed (Brassica napus L.) varieties as revealed by molecular markers

Rapeseed (Brassica napus L.) crop can be a lever for the development of oilseed sector in Morocco due to its adaptation to local conditions and its major economic and food importance. Genetic diversity and selection of valuable crossing parents are the key to successful breeding and improvement of this crop. In this regard, genetic variation within the existing germplasm must be explored and characterized. Therefore, the present study was carried out to investigate the genetic diversity among 22 varieties from Morocco as well as other origins, using twenty ISSR primers. The selected primers have generated a total of 319 markers. Polymorphic amplified bands varied from 8 to18, with an average of 13 per primer. The diversity index (PIC value) ranged from 0.295 to 0.509, with a mean value of 0.37 per primer, indicating a good genetic diversity level for the primers used. The average similarity coefficient was 0.31, fluctuating between 0.176 and 0.456, and the pairwise comparison of the studied varieties showed a great discriminating power of primers and a large genetic diversity among accessions. A total of eight ISSR primers could be identified as key to rapeseed varietal determination. Hierarchical classification allowed identifying three groups with some phylogeographic structuring. This is the first report of molecular characterization of rapeseed germplasm in Morocco and Africa. The obtained results have important implications for management of this germplasm to conserve the existing genetic diversity and use it properly in breeding programs in Morocco as well as in other Mediterranean and African countries.