After reading this article we will learn about the estimation of additive and dominance variance.
Additive (D) and dominance (H) genetic variances are easily computed with the help of following formulae. In some nomenclatures additive variance is denoted by A and dominance by H.
where, V = Variance, ½ D = additive genetic variance, 1/4H = dominance variance, and VE
= environmental variance which is calculated as the mean of variance in the non-segregating generations, for example.
Thus, for estimating D and H components, we need to have variances in the parental. F2 and BC1, BC2 generations.
Numerical Example:
It should be noted that the numerical values of 1/2D and 1/4H are to be accepted as such ignoring 1/2 and 1/4 respectively, as these coefficients are the frequencies of the gene. From the above values, heritability in narrow sense and genetic advance can be calculated as follows:
Heritability in Narrow Sense:
= Additive genetic variance/Total phenotypic variance in F2 = 30/50 = 0.60 = 60%
Genetic Advance (Assuming Selection of 5% Plants):
= i σp h2
= 2.06 √50 x .60
= 2.06 x 7.07 x .60 = 8.74