[Estimation of the sampling variance of co-heritability]

Formulae for the sampling variances of co-heritability and co-environment are developed from the one-fold and two-fold nested genetic analyses of variance and covariance with balanced and unbalanced data. Some potential roles of the co-heritability in breeding programs and the relationship with genetic correlation have also been investigated. The co-heritability has dual characteristics of both heritability and genetic correlation. Heritability is a special case of co-heritability with co-heritability an extended form of heritability. The use of co-heritability to express the genetic covariation between two characters will give smaller sampling errors than those of the genetic correlation (gamma A).