Genetic Diversity Analysis and Core Collection Formation in Rapeseed Genetic Resources in Japan

After being introduced into Japan, the rapeseed (Brassica napus) has been widely cultivated all over the country, some breeding programs have been carrying out to meet the different consumer demands. To provide valuable information for these programs, diversity analysis of NARO Genebank accessions and development of a core collection were performed by this study.

The whole rapeseed collection in the NARO Genebank (582 accessions) was analyzed by genotyping with 30 polymorphic SSR markers, which amplified a total of 311 alleles. The whole collection revealed medium levels in He and polymorphic information content values (PIC), averaging 0.57 and 0.52 respectively, the Ho values of the all accessions ranged between 0.01 to 0.34, and averaged 0.05. Population structure analysis divided the whole collection into two main groups: one mainly composed of exotic accessions, the other mainly composed of Japan accessions with lower genetic diversity level. The proportion of genetic differentiation among individuals within the two groups was found to be significant with a F_ST value of 0.30. Analysis of molecular variance showed the main molecular variation in the whole collection was attributed to genetic differentiation among individuals (67.18%). These results indicated that the NARO rapeseed Genebank has a medium level of genetic diversity, and Japanese cultivars may be bred by a limited number of parental germplasms.

Core collection constructed by software PowerCore in this study showed the best representation among four methods, it will be useful for genetic researches and breeding programs in rapeseed.