Reproductive isolation on interspecific backcross of F1 pollen to parental species, Hemerocallis fulva and H. citrina (Hemerocallidaceae).

Reproductive failure of backcross could play important roles in determining the evolutionary outcome of hybridization. However, such studies have been somewhat fewer than those of the F1-producing cross and F1 × F1 cross. We conducted hand-pollination backcross experiments using Hemerocallis fulva, H. citrina, and their F1 hybrids. Seed set per flower of the backcrosses reduced to about 50% of the control cross, irrespective of ovule parent species. This symmetrical seed set reduction on the backcross might be caused by the death of backcross embryo as a result of Dobzhansky–Muller incompatibility by recessive alleles.