Embryo sac abortion is one of the major reasons for sterility in indica/japonica hybrids in rice. To clarify the causalmechanism of embryo sac abortion, we studied the female gametophyte development in two indica/japonica hybrids viaan eosin B staining procedure for embryo sac scanning using confocal laser scanning microscope. Different types ofabnormalities occurred during megasporogenesis and megagametogenesis were demonstrated. The earliest abnormalitywas observed in the megasporocyte. A lot of the chalazal-most megaspores were degenerated before the mono-nucleateembryo sac stage. Disordered positioning of nucleus and abnormal nucellus tissue were characteristics of the abnormalfemale gametes from the mono-nucleate to four-nucleate embryo sac stages. The abnormalities that occurred from theearly stage of the eight-nucleate embryo sac development to the mature embryo sac stage were characterized by smallersizes and wrinkled antipodals. Asynchronous nuclear migration, abnormal positioning of nucleus, and degeneration ofegg apparatus were also found at the eight-nucleate embryo sac stage. The abnormalities that occurred during femalegametophyte development resulted in five major types of abnormal embryo sacs. These abnormal embryo sacs led toabnormal fertilization. Hand pollination using normal pollens on the spikelets during anthesis showed that normal pollenscould not exclude the effect of abnormal embryo sac on seed setting.
Yu-Xiang Zeng Chao-Yue Hu Yong-Gen Lu Jin-Quan Li Xiang-Dong Liu
