Analysis of locus estimates of allelic diversity of STR markers in a sample of breeding bulls

Abstract

Genotypes of the 11 DNA microsatellite loci of 84 bulls of seven breeds were used to evaluate 14 indicators of allelic diversity/differentiation. Traditional and multidimensional statistical methods were applied to the data matrices from the original and transformed estimates (11×14). Estimates of heterozygosity had coefficients of variability of 8-14 %, the number of alleles per locus and indicators of differentiation of breeds at the level of 20-26 %, fixation indices – 38-44 %. Statistically significant Kendall correlations (0.8-1.0) between indicators of allelic richness and heterozygosity, fixation indices, and differentiation indicators were established. The variability of the transformed estimates of diversity/differentiation indicators by loci was in the range of 6-32 %. Including by loci Eth3, Tgla122, Eth225, Bm2113 – 6-12 %, loci Inra23, Tgla126, Eth10 – 15-20 %, loci Tgla227, Sps115, Tgla53, Bm1824 – 28-32 %. The nonparametric Mann-Whitney-Wilcoxon test showed statistically significant differences in the medians of the Eth3 locus with the Bm2113 locus, the Tgla126 locus with the Eth3, Inra23, Tgla122, Eth225, Bm2113, Bm1824, Eth10 loci. The principal component analysis (PCA) identified two components with a total information content of 95,2 %. The first one took into account 59.4 % of the total variance, had the highest loads in intra-breed diversity data and was defined as an «alpha component». The second accounted for 35.8 % of the total variance, had the highest loads in inter-breed differentiation data and was defined as a «beta component». 2D-PCA-ordination showed that a characteristic grouping of loci took place for the analyzed breeds (samples), loci and measures of diversity. Loci Tgla227 and Tgla53 formed group A, group B – loci Tgla122, Eth225, Eth10, group C – loci Inra23, Bm2113 and Bm1824. The loci of the conditional group D (Eth3, Tgla126, Sps115) were defined as «untypical». Validation of ordination was confirmed by calculations on reduced data (dimension 11×7) and the method of non-metric multidimensional scaling (nMDS). The consistency of ordinations according to the Procrust test was 96 % (pperm <0.001). A similar classification of loci was obtained by cluster analysis (UPGMA) with butstrap probabilities of cluster: A – 73, B – 100, C – 73, D – 47 %. The distances and similarity indicators (S) between the profiles of loci and the «true» summary estimates for 11 loci were calculated. Loci Tgla126 and Sps115 had S ≈ 40 %, loci Tgla53 and Bm1824 – at the level of 60 %, loci Inra23, Tgla227 and Bm2113 – 70-75 %, loci Eth3, Tgla122, Eth225 and Eth10 – 84-88 %. The average absolute deviation of the estimates of diversity indicators for the four loci with S≥84 % from the «true» estimates was 3.4 %, for the four loci with S≤60 % – 12.4 %. According to component scores, a general diversity index, γLV, was calculated for each locus. Its correlation with the estimates of the Shannon/Sherwin′s γ-diversity with a 95 % probability value was in the range of 0.73-0.98, Kendall's rank correlation was 0.67 (pvalue = 0.005). The conducted research makes a certain contribution to the expansion of tools for processing molecular genetic data in the analysis of allelic diversity in subdivided populations.