GENETIC-VARIATION OF TRAITS MEASURED IN SEVERAL ENVIRONMENTS .2. INFERENCE ON BETWEEN-ENVIRONMENT HOMOGENEITY OF INTRA-CLASS CORRELATIONS

This paper describes a further contribution to the problem of testing homogeneity of intra-class correlations among environments in the case of univariate linear models, without making any assumption about the genetic correlation between environments. An iterative generalized exp ectation-maximization (EM) algorithm, as described in Foulley and Quaa s (1994), is presented for computing restricted maximum likelihood (RE ML) estimates of the residual and between-family components of varianc e and covariance. Three different parameterizations (cartesian, polar and spherical coordinates) are proposed to compute EM-REML estimators under the reduced (constant intra-class correlation between environmen ts) model. This procedure is illustrated with the analysis of simulate d data.