We have compared the genetic diversity of 24 Chinese weak-winter, Swedish winter and spring Brassica napus accessions by inter-simple sequence repeats (ISSRs). Using cluster analysis (UPGMA) based on 125 polymorphism bands amplified with 20 primers, the 24 accessions were divided into three groups. Six Swedish winter lines and eight Chinese weak-winter lines were in group I and group II consisted of two Chinese weak-winter lines, Xiangyou15 and Bao81. The third group contained eight Swedish spring lines. Principal coordinates (PCO) analysis showed similar groupings to cluster analysis. Results from cluster analysis and PCO analysis showed very clearly that Chinese weak-winter, Swedish spring and winter accessions were distinguished from each other and Chinese weak-winter accessions in this study were genetically closer to Swedish winter accessions than to Swedish spring accessions. The Chinese weak-winter accessions had larger diversity than the Swedish spring or winter accessions. This study indicated that ISSR is a suitable and effective tool to evaluate genetic diversity among rapeseed germplasm.
