additive genetic covariance的用法和样例：
- The additive genetic variance of the same character, estimated from the covariance of half sibs, was 0. 9602.
- Only the additive genetic variance is transmissible by seed.
- Only the genetic covariance between PC and the brown rice width (BRW) was positively correlative, whereas all the other pairwise traits were negatively correlative.
- The therotical equation for additive genetic variance of mark gene was established for individual level and seperate population level in linkage equilibrium.