Abstract
We investigated female and male gamete formation in a pummelo [Citrus maxima (Burm.) Merr.] haploid. During female gamete formation, no embryo-sac mother cell (EMC) was formed in ovules, and consequently no normal embryo sac was observed at anthesis, which was confirmed as the cause of female sterility in the haploid. During male gamete formation, on the other hand, meiosis in the pollen mother cells (PMCs) of the haploid occurred twice, but abnormalities were observed in most dividing cells. In some dividing cells, univalents did not distribute to the opposite poles at anaphase I; instead, they remained near the equatorial plate. The nine univalents then performed mitosis, which distributed equally forward opposite poles. Furthermore, at the tetrad stage, the tetrad comprised 99.3% of the ‘Banpeiyu’ pummelo, whereas sporads from monads to hexads with a relatively high frequency of dyads (24.7%) were produced in the haploid. These results suggest that fertile pollen grains observed in the haploid pummelo were produced by abnormalities in the first meiotic division such as first division restitution (FDR).
