SSR analysis of genetic diversity among maize inbred lines adapted to cold regions of Japan

Information regarding diversity and relationships among breeding material is necessary for hybrid maize (Zea mays L.) breeding. Simple-sequence repeat (SSR) analysis of the 60 loci distributed uniformly throughout the maize genome was carried out for 65 inbred lines adapted to cold regions of Japan in order to assess genetic diversity among the inbred lines and to assign them to heterotic groups. The mean value (0.69) of the polymorphic-index content (PIC) for the SSR loci provided sufficient discrimination-ability for the assessment of genetic diversity among the inbred lines. The correlation between the genetic-similarity (GS) estimates and the coancestry coefficient was significant (r = 0.70). The average-linkage (UPGMA) cluster analysis and principal-coordinate analysis (PCOA) for a matrix of the GS estimates showed that the Northern flint inbred lines bred in Japan were similar to a Canadian Northern flint inbred line CO12 and a European flint inbred line F283, and that dent inbred lines bred in Japan were similar to BSSS inbred lines such as B73. These associations correspond to the known pedigree records of these inbred lines. The results indicate that SSR analysis is effective for the assessment of genetic diversity among maize inbred lines and for the assignment of inbred lines to heterotic groups.