Use of covariances between predicted breeding values to assess the genetic correlation between expressions of a trait in 2 environments

Abstract

Procedures to interpret correlation and regression coefficients involving predicted breeding values (BV) calculated for the same animals in different environments have been developed. Observed correlations are a function of the additive genetic correlation between performances in the 2 environments but are also affected by selection of animals that produce data in both environments, the accuracy of BV predictions in each environment, relationships among animals within and across environments and covariances among BV predictions within an environment arising from estimation of fixed effects in best linear unbiased prediction (BLUP) of animal BV. Methods to account for effects of selection and variable accuracy and experimental designs to minimize effects of relationships and covariances among BV predictions from estimation of fixed effects have been described. The regression of predicted BV in environment 2 on predicted BV in environment 1 is generally not affected by selection in environment 1, but both correlation and regression coefficients are sensitive to covariances among breeding value predictions within environments. In general, caution must be exercised in interpreting observed associations between predicted breeding values in different environments. [References: 34]