| Rice(Oryza sativa L.) is one of the most important food crops in the world and more than half of the world’s population depends on it as the staple food. As the development of society, people has more and more requirement on the yield and quality of rice, improving which has become breeder’s main breeding goal. Oryza glaberrima Steud. owns many valuable genes, such as genes of disease and insect resistance, saline tolerance, drought resistance and high temperature resistance, and there is strong inter-species heterosis between Oryza sativa L. and Oryza glaberrima Steud.. If we could introduce these valuable genes in Oryza glaberrima Steud. into Oryza sativa L. and efficiently make use of the heterosis, it would certainly improve the yield of rice, significantly, and bring a new leap for rice breeding. However, there is serious reproductive isolation, usually exhibiting extreme sterility of F1hybrids, between Oryza sativa L. and Oryza glaberrima Steud., which greatly limites the transferation of valuable genes from Oryza glaberrima Steud. to Oryza sativa L. and the use of inter-species heterosis. So it is very necessary to explore the cytological mechanism of hybrid sterility, find more hybrid sterility genes and illuminate the molecular mechanism of hybrid sterility. This will be much theoretically and practically meaningful for overcoming the inter-specific hybrid sterility and taking full use of valuable genes in Oryza glaberrima Steud. and the inter-species heterosis between Oryza sativa L. and Oryza glaberrima Steud..In this study, we used a Near-isogenic line (NIL) developed using the japonica variety Dianjingyou1as the receptor parent and O. glaberrima Steud. as the donor parent. Half of pollens of DJY1/NIL F1were sterile, which was controlled by one locus named S39. The fine mapping of S39had been finished, which established a solid foundation for cloning S39and better understanding the molecular mechanism of hybrid pollen sterility between Oryza sativa L. and Oryza glaberrima Steud..The main results of this study were as follows: 1. F1pollen fertility of DJY1/NIL exhibited typical semi-sterility and the iodine staining experiment showed that the type of pollen abortion was stained abortive. Carmine acetate dyeing revealed the abortion of pollen happened at the later bicellular pollen stage. Observation of abortive F1pollens using transmission electron microscopy (TEM) and scanning electron microscopy (SEM) showed the abortive pollens in F1hybrid were shrunken and had smaller volume, which had little accumulation of starch granules. Aniline blue staining exhibited that many pollen grains adhered to the stigmas and were able to germinate both in the parental plants and the F1hybrid. Through statistics of the seed setting rate, we found there was no significant difference between the parental plants and the F1hybrid,indicating that the site did not affect the fertility of female gametes.2. Using321individual plants in DJY1/NIL F2group for linkage analysis, the pollen sterility was found to be controlled by S39.The S39was located to the region between the top of Chr.4short arm and marker RM7585, with an interval of228kb.Then utilizing an expanded F2group of22200individuals, S39was finally fine mapped to the region between the top of Chr.4short arm and marker F-28, with a physical distance of101kb. In Nipponbare, the corresponding sequence contained23ORFs. While, in O. glaberrima Steud., the corresponding sequence was152kb, containing36ORFs. With the candidate gene having the function of expression as the premise and according to the view of "one-locus sporo-gametopytic interaction model ",3ORFs were determined as the most likely sterile genes. The construction of corresponding vectors and complementation experiments are underway. |
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