ACCURACY OF EVALUATION AND CORRELATION OF ESTIMATED BREEDING VALUES AMONG RELATIVES, WITH EVALUATION BASED ON INFORMATION FROM RELATIVES ORFROM IDENTIFIED LOCI

Deterministic methods were used to calculate the accuracy of evaluatio n, and the correlation of estimated breeding values (EBV) among sibs, when evaluation is based on phenotypic records of the individual and r elatives, or on quantitative-trait-locus (QTL) information. An additiv e infinitesimal genetic model was assumed, with discrete generations o f truncation selection on EBV, and random mating of selected parents i n a hierarchical design. It was shown that the overlap of phenotypic d ata between the evaluations of relatives causes large increases in cor relations of EBV with only modest increases in accuracy. This explains the disproportionate increases in inbreeding observed by other author s. By contrast, the use of major-locus information leads to low correl ations of EBV among relatives, provided that functional loci are direc tly identified or there is complete linkage disequilibrium. Use of inf ormation from QTL should reduce EBV correlations and, hence, inbreedin g, but use of information from markers may not be so useful, since err ors of estimation of association with QTL will be shared by family mem bers, leading to increased correlations of EBV.