Comparison of molecular markers and coefficients of parentage for the analysis of genetic diversity among spring bread wheat accessions

The comparison of different methods of estimating genetic diversity could define their usefulness in plant breeding and genetic improvement programs. This study evaluates and compares the genetic diversity of 70 spring wheat accessions representing a broad genetic pool based on molecular markers and parentage relationships. The sample was composed of 32 accessions from the International Maize and Wheat Improvement Center (CIMMYT) and 38 from other breeding programs worldwide. Eight AFLP-primer combinations and 37 pairs of SSR primers were used to characterize the accessions and the Coefficients of Parentage (COP) were calculated from registered pedigrees. The average genealogical (COP) similarity (0.09 with a range of 0.0-1.0) was low in comparison to similarity calculated using SSR markers (0.41 with a range of 0.15-0.88) and AFLP markers (0.70 with a range of 0.33-0.98). Correlation between the genealogical similarity matrix (excluding accessions with COPs = 0) and the matrices of genetic similarity based on molecular markers was 0.34 less than or equal to r less than or equal to 0.46 (p < 0.05). It is concluded that AFLP and SSR markers are generally in agreement with estimates of diversity measured using COPs, especially when complete pedigree data are available. However, markers may provide a more correct estimate due to some unrealistic assumptions made when calculating COPs, such as absence of selection. Furthermore, both COP and marker distances indicate that CIMMYT accessions are different from the worldwide group of accessions.