Breeding Barriers in Interspecific Hybridization between Fagopyrum esculentum and F. tataricum

Using fluorescent microscopy and Nomarski’s interference microscopy, pollen tube growth, and embryo and endosperm development were observed to elucidate interspecific cross-incompatibility in the genus of Fagopyrum. Interspecific hybrdization between Fagopyrum esculentum and F. tataricum was not successful because of failure of seed set in both crossing directions. Two different breeding barriers to crossibility were found: a pre-zygotic barrier and a post-zygotic barrier. Many abnormalities were observed in pollen-tube development, which severely reduced the percentage of fertilization. Differences in the percentage of fertilization were detected between the two accessions of F. esculentum involved in the interspecific crosses. The interspecific embryo and endosperm nuclei always degenerated at 3-5 days after pollination. The embryo ceased to develop at a globular and early heart stages, which is too early to be used for in vitro embryo rescue.