Genetic diversity of Chinese cultivars in Brassica napus revealed by SSR markers

【Objective】 The study was done to reveal genetic diversity of 66 recently registered cultivars in Brassica napus from four winter-type rapeseed regions in China.【Method】 Twenty-four pairs of SSR primer were chosen to analyze 66 B.napus cultivars registered after 1999 and four hybrid combinations in China.Principal component analysis,Shaanon index,Simpson index and Amova analysis were combined to reveal genetic structure of all tested varieties.【Result】 In total,104 fragments were detected with size ranged from 100 to 600 bp and 86 were polymorphism,the polymorphism rate was 84.61%.On average,each primer pair generated 4.3 polymorphic fragments with polymorphic rate ranged from 50% to 100%.The genetic similarity of 70 B.napus accessions ranged from 0.40-0.93,with average of 0.63.Principal component analysis revealed that all varieties scattered well in bi-plot,and accessions from the same geographic origin did not group together.Among four winter-type rapeseed regions,varieties from the middle of Yangtze valley had the highest values of Shaanon index(1.593),Simposon index(0.732),and average number of pairwise differences within population(0.343 1).AMOVA analysis indicated that the components of variation within populations and among populations were 96.74% and 3.26%,respectively.【Conclusion】 There existed considerable variance among recently registered B.napus cultivars in China.The component of variation within populations was dominant among populations.Varieties in middle of Yangtze valley possessed the richest genetic variation in the present investigation.The present investigation indicated that rapeseed genetic resources were extensively exchanged among different rapeseed regions in China.