The observed frequencies of introgressed heterospecific alleles transmitted from F
(2) or F
(3) hybrids to backcross progeny in BCIB or BCIF populations. The X-axis indicates the genetic distances (cM) of the LGs in the composite map; the Y-axis indicates the transmission ratio of introgressed heterospecific alleles, the IF174 alleles in the BCIB population and the IB25 alleles in the BCIF population. Frequencies > 0.50 indicate an overrepresentation of heterospecific alleles. Frequencies < 0.50 indicate an overrepresentation of homospecific alleles. The expected frequency is 0.50. Data points above and below the stippled lines indicate significant deviations from 0.50 (α = 0.05).