2008 Joint Annual Meeting (5-9 Oct. 2008): Comparison of Similarity and Dissimilarity Coefficients in Tropical Maize Based on Microsatellite Markers.

This study compared different similarity and dissimilarity coefficients and their influence in maize inbred lines clustering. Ninety maize S_0:1 inbred lines were used and genotyped with 25 microssatellite markers (SSR). The Simple Matching, Rogers and Tanimoto, Russel and Rao, Hamann, Jaccard, Sorensen-Dice, Ochiai and Modified Roger’s Distance coefficients were compared by consensus index, projection efficiency in a two-dimensional space and by Spearman’s correlation. Changes were found in high genetic similarity groupings with different coefficients by the consensus index. Russel and Rao and Jaccard coefficients had the greatest stress values with 75.67% and 40.16% respectively, indicating that these coefficients should not be used. Genotype ranking changed, mainly in the comparation of the Modified Roger’s Distance in relation to some coefficients (r_s=0.75). Russel and Rao’s and Jaccard’s coefficients should be avoided for their low accuracy. Moreover, genotype clustering by different similary coefficientes, without a close consideration about these coefficients could affect the research results.