PROBLEMS WITH INDOGAMIC LINES. IV. COANCESTRY WITHIN LINES AND BETWEEN SISTER LINES

Abstract

Formulae for the calculation of coancestry among individuals of an inbred line and among sib lines (or sublines) of a line are derived for three types of lines: selfed, full-sib, and half-sib lines. In the three cases the result is: 1/4 (1+ 2F_t, x + F_t-1, x) for the inbreeding generation t, and for the regular system of inbreeding x. The relation between the calculated  coancestry and the heterosis of the sib lines is discussed; heterosis increases due to the reduction of the genetic value of the inbred lines, as inbreeding proceeds, rather than by an increase of the average genetic value of the single crosses, which remains constant through the generations of inbreeding of the lines. Possible uses of the coancestry coefficient of the inbred lines are mentioned.