ESTIMATING MIXTURE FRACTION AND MAP DISTANCE IN A MIXED F\u3csub\u3e2\u3c/sub\u3e, BC\u3csub\u3e1\u3c/sub\u3e POPULATION

An F1 interspecific hybrid onion (Allium cepa x A. fistulosum) was backcrossed to the A. cepa parent line under field conditions. The progeny of this cross were shown by electrophoretic protein analysis to be a mixture of BC1 (the desired backcross) and F2 (A. cepa x A. fistulosum) x (A. cepa x A. fistulosum) individuals. This mixture of populations among the progeny render the usual X2 test for independent segregation of loci invalid. F2 is used to denote progeny derived from either selfing of the F1 or from sib-crosses between two F1 individuals. A model for this mixed population has been developed; from this model the mixture fraction and crossover frequencies can be estimated using maximum likelihood