Sampling bias in estimating Design II variance components with S1 families.

The use of several S1 individuals to represent an S0 individual permits the use of a Design II mating scheme for plants with only one pistillate flower per plant. Estimates of additive (V A ) and dominance (V D ) variance from this mating scheme will be biased upwards, when a small number (10) of individuals of each S1 line are used. This bias can be computed, and the additive and dominance estimates can be corrected. Of particular interest is the observation that the additive genetic variance contributes to bias in estimates of V D . When S0 plants are non inbred and their selfedprogeny (S1 lines) are used to represent them in developing families for use in the Design II, [Formula: see text] where m1 is the number of individuals used to represent an S1 line in developing half sib-families and m2 is the number of individuals used to represent the S1 line in making up full sib-families. For example, in a 3×3 Design II, with about 10 individuals used to represent each S1 line in each cross, m2 = 10 and m1 = 30. When m1 = m2 = 1, [Formula: see text] and [Formula: see text].