Analysis Of Genetic Diversity Among Maize Inbred Lines Using SSR Markers

Genetic diversity and heterotic grouping among maize germplasm are fundamentally important in maize breeding. In this study, 119 early-maturity inbred lines, which are most commonly or potentially used in Chinese maize breeding programs, were fingerprinted with 70 SSR markers using 6 domestic and 6 CIMMYT lines as tester. By combining pre-exist dataset, a primary fingerprinting database were established containing 70 SSR primers and 375 maize inbred lines. Furthermore, the genetic structure and diversity among 375 lines were investigated. The results were summarized as follows:1.119 early-maturity lines and 12 tester lines were fingerprinted with 70 SSR markers. A total of 285 alleles were detected. The average alleles per locus were 4.07 with a range from 2 to 8. The mean value of the polymorphism information content (PIC) was 0.58 with a range from 0.18 to 0.81. The genetic-similarity (GS) was estimated with an average value of 0.68, which was from 0.50 to 0.94. The UPGMA method grouped the 119 early-maturity lines into six clusters (i.e.Sipingtou, Luda Red Cob, PA, PB, BSSS and Lancaster), which were consistent with their pedigree information.2. A primary SSR fingerprinting database, containing 70 SSR primers and 375 maize lines combined from different datasets acquired by the lab, was established based on the same tester lines, loci and unified detecting methods. A total of 291 alleles were detected among 375 lines using 70 SSR markers. The average alleles per locus were 4.2 with a range from 2 to 8. The mean value of the polymorphism information content (PIC)was 0.60 with a range from 0.16 to 0.88. The genetic-similarity (GS)were estimated with an average value of 0.64 ranged from 0.30 to 0.98. Using UPGMA analysis, principal coordinate analysis(PCoA), Neighbor-Joining(NJ)and Minimum-Evolution(ME) statistics methods, 375 lines were grouped to six clusters, which were consistent with their known pedigree information. A modal-based approach with the STRUCTUR clustering suggested that 375 lines were grouped into six clusters (i.e. Sipingtou, Luda Red Cob, PA, PB, BSSS and Lancaster). The high genome-wide distribution and extent of LD were found among 70 SSR loci.3. Comparative analysis revealed that at least 40 SSR loci and/or 180 alleles were needed for genetic diversity analyzing infered by the standard error and Mantel correlation among similarity matrices of 375 lines. After comparative analysis among difference data, 12 tester lines were representational and stable, which can be used as the reference lines in genetic diversity studyies.