Controlled Pollination with Sorted Reduced and Unreduced Pollen Grains Reveals Unreduced Embryo Sac Formation in Diospyros kaki Thunb. ‘Fujiwaragosho’

Abstract

This study investigated ploidy levels of endosperm and embryos in seeds of the hexaploid (2n = 6x = 90) Diospyros kaki ‘Fujiwaragosho’ to determine the possible origin of unusual ploidy levels observed in seedlings of this cultivar. Female flowers of ‘Fujiwaragosho’ were pollinated with sorted reduced (3x) and unreduced (6x) pollen grains of ‘Zenjimaru’ in 2004 and 2005. Embryo rescue culture was conducted with normally developing seeds that were excised from immature fruit harvested in August. Ploidy levels of the endosperm and plantlets from the embryos in the seeds were determined by flow cytometry. In some cases, chromosomes of root tip cells of the plantlets were also counted to determine ploidy levels of the embryos. It appeared that seeds obtained with reduced pollen pollination contained a normal hexaploid embryo and nonaploid (9x) endosperm, while those obtained with unreduced pollen pollination mostly contained a dodecaploid (12x) embryo and octadecaploid (18x) endosperm. These results indicated unreduced embryo sac formation in ‘Fujiwaragosho’. We discuss the possible cause of the occurrence of only nonaploid and octadecaploid endosperm, respectively, with reduced and unreduced pollen pollinations.