Failure of Fertilization Associated with Absence of Zygote Development in the Interspecific Cross of Fagopyrum tataricum × F. esculentum

Abstract

To obtain a desirable hybrid from an interspecific cross between Fagopyrum tataricum and F. esculentum, the early embryo developmental changes were investigated by light microscopy and transmission electron microscopy (TEM). The nature of pre- and post-fertilization barriers in the hybrid embryo was examined at the ultrastructural level. The ovules were excised at 1 to 5 days after pollination (DAP) and fixed for TEM. In comparison with self-pollinated embryo (F. tataricum) or legitimate-pollinated embryo (F. esculentum), the interspecific hybrid embryos showed numerous abnormal ultrastructural pre- and post-fertilization phenomena leading to the abortion of embryo. The main abnormal phenomena were failure of fertilization, no zygotic development with a broken cell wall, dispersed endosperm with absence of ribosomes, and defective embryo sac development such as srunken, small and irregular-shaped embryo sac. The interspecific incompatibility was attributed to the failure of fertilization and the hybrid zygotic embryo showed retardation in cell division, which resulted in cease of development.