Autotetraploid indica/japonica rice hybrid combines both the advantages of polyploidy and the heterosis between indica and japonica rice. Embryo sac abortion is an important factor influencing spikelet fertility in autotetraploid rice hybrid. To clarify the cytological mechanism of embryo sac abortion, the megasporogenesis and megagametogenesis in an autotetraploid japonica/indica hybrid were examined by the whole-mount eosin B-staining confocal laser scanning microscopy (WE-CLSM) technique. Abnormalities were observed from the megasporocyte stage to the mature embryo sac stage. The degeneration of the tetrad cells and the functional megaspore was the characteristic of abnormalities during megasporogenesis. Abnormal small embryo sacs and disordered number of nuclei were frequently observed during embryo sac development. Some interesting phenomena, such as two functional megaspores, the diplospory-like megasporocyte, and five-nucleate embryo sac were found. The abnormalities that occurred during female gametophyte development resulted in more than five types of abnormal embryo sacs (i.e. embryo sac degeneration, embryo sac without female germ unit, embryo sac without egg apparatus, embryo sac with abnormal polar nuclei and abnormal small embryo sac) in autotetraploid japonica/indica hybrid. Embryo sac fertility was lower in diploid japonica/indica hybrid than in autotetraploid japonica/indica hybrid although many abnormal phenomena were observed in autotetraploid hybrid.
HU Chao-yue, ZENG Yu-xiang, GUO Hai-bin, LU Yong-gen, CHEN Zhi-Muhammad Qasim SHAHID, LIU Xiang-dong
. Megasporogenesis and Megagametogenesis in Autotetraploid Indica/ Japonica Rice Hybrid[J]. Rice Science, 2010
, 17(4)
: 292
-302
.
DOI: 10.1016/S1672-6308(09)60030-5
Cai D T, Yuan L P, Lu X G. 2001. A new strategy of rice breeding in the 21st century: II. Searching a new pathway of rice breeding by utilization of double heterosis of wide cross and polyploidization. Acta Agron Sin, 27: 110–116. (in Chinese with English abstract)
Guo H B, Feng J H, Lu Y G, Liu X D. 2006. Abnormal structure of embryo sac in autotetraploid rice. Rice Sci, 13(4): 257–264.
Hu C Y, Zeng Y X, Lu Y G, Li J Q, Liu X D. 2009. High embryo sac fertility and diversity of abnormal embryo sacs detected in autotetraploid indica/japonica hybrids in rice by whole-mount eosin B-staining confocal laser scanning microscopy. Plant Breeding, 128: 187–192.
Huang B Q, Russell S D. 1992. Female germ unit: Organization, reconstruction and isolation. Int Rev Cytol, 140: 233–293.
Huang Q C, Qin G Y, Xiang M C, Liang F. 2004. Preliminary studies on male-sterile stability in autotetraploid rice with photo- thermal sensitive male-sterility. Acta Agron Sin, 30: 183–185. (in Chinese with English abstract)
Luan L, Tu S B, Long W B, Wang X, Liu Y H, Kong F L, He T, Yan W G, Yu M Q. 2007. Cytogenetic studies on two F1 hybrids of autotetraploid rice varieties showing extremely high level of heterosis. Plant Syst Evol, 267: 205–213.
Song W C, Zhang Y H. 1992. Rice tetraploidy and its effect on agronomic traits and nutritional constituents. Acta Agron Sin, 18: 137–144. (in Chinese with English abstract)
Tu S B, Kong F L, Xu Q F, He T. 2003. Breakthrough in hybrid rice breeding with autotetraploid. CAS Bull, 6: 426–428.
Tu S B, Luan L, Liu Y H, Long W B, Kong F L, He T, Xu Q F, Yan W G, Yu M Q. 2007. Production and heterosis analysis of rice autotetraploid hybrids. Crop Sci, 47: 2356–2363.
Xiao B, Liu X D, Lu Y G, Li J Q, Zhao X J. 2005. Structure and fertilization of embryo sac in intersubspecific hybrids of autotetraploid rice. Acta Agron Sin, 31: 1150–1156. (in Chinese with English abstract)Zeng Y X, Hu C Y, Lu Y G, Li J Q, Liu X D. 2007. Diversity of abnormal embryo sacs in indica/japonica hybrids in rice demonstrated by confocal microscopy of whole ovary. Plant Breeding, 126: 574–580.
Zeng Y X, Hu C Y, Lu Y G, Li J Q, Liu X D. 2009. Abnormalities occurring during female gametophyte development result in the diversity of abnormal embryo sacs and leads to abnormal fertilization in indica/japonica hybrids in rice. J Integr Plant Biol, 51: 3–12.
Zhang H H, Feng J H, Lu Y G, Yang B Y, Liu X D. 2003. Observation on formation and development of autotetraploid rice embryo sac using laser scanning confocal microscope. J Chin Electron Microsc Soc, 22: 380–384. (in Chinese with English abstract)
