Genetic variance and drift in selfed and intermated populations derived from backcrossing.

The genetic variance among random-mated lines derived from backcrossing (BCgS1 lines) depends upon the backcross generation (g) and the number (n) of BCgF1 plants crossed in generations 1 through g. There is little effect of n on genetic variance for n > 6. The genetic variance among BCgF2-derived lines is greater than that among BCgS1 lines for all g. If either BCgF2-derived or BCgS1 lines are used as a base population for recurrent selection, 8, 16, 32, and 64 BC1F1, BC2F1, BC3F1, and BC4F1 plants, respectively, should be used to avoid loss of donor alleles to drift.