Dissection Of Partial Sterility Of The Indica-Japonica Intersubspecific Hybrids In Rice

The partial sterility of intersubspecific hybrids has been a major barrier for utilization of the strong heterosis expressed in hybrids between Oryza sativa ssp. indica and O. sativa ssp. japonica. Cytological investigation revealed that the intersubspecific sterility caused both by male gamete abortion, female gamete abortion and reduced dehiscence of the anthers. So, the study of hybrid sterility on cytological and genetics level is useful to know how such abnormalities are genetically controlled or to what extent they influence hybrid sterility.In this study we investigated each development stage of female gamete in indica, japonica, WCV and the hybrids and detect what happen in that process. Then a three-way cross population '02428'/'Nanjing11'//'Balilla' was used to construct a genetic map and measure the embryo sac fertility, pollen fertility and spikelet fertility. QTLs for three traits were mapped. The construction of NILs also has been commenced. The main results are summarized as following:1. Several types abnormalities were detected during the process of megasporogenesis, the most often abnormalities were observed at megaspores stage. Pollen sterility also detected in intersubspecific hybrids.2. Whole-stain clearing method was used for evaluating embryo sac fertility and then I₂-KI stain method for pollen fertility. Embryo sac fertility in the three-way cross population varied from a low of 20% to a high of 100%, and showed an apparent bimodal distribution. The distribution of pollen fertility and spikelet fertility exhibited continuously.3. The simple correlation and multiple regression analysis were conducted among embryo sac fertility, pollen fertility and spikelet fertility. Results showed that male and female gamete abortions contributed almost equally to the intersubspecific hybrid sterility.4. A linkage map consisting of 191 loci was constructed using MAPMAKER/EXP at LOD 3.0. The total length of this map was 1,761.4 cM, with an average interval of9.2 cM between adjacent markers. The linear order of makers in this map accorded well with the published map.5. One QTL with major effect was resolved for embryo sac fertility, two QTLs were detected.for pollen fertility and three QTLs were identified for spikelet fertility. The locations of two major QTLs of spikelet fertility corresponded well with the major QTLs for pollen fertility and embryo sac fertility, respectively.6. Except one interaction of small effect between spf5 and spf8, the ANOVA results indicated that most of loci acted independently in determining pollen fertility and spikelet fertility. And the mode of gene action was the same at all the six QTLs identified for the three traits7. Expect few minor loci, the QTL analysis results are similar between composed interval mapping, interval mapping and single marker method. The another hybrid sterility locus detected method depend upon segregation distorted was also discussed.8. A large of digenic interactions was detected for three traits. A major QTL locus, spf5, plays an important role in interactions.9. The function of spJ8 was discussed and we supposed that the heterozygosis at this locus leads the asynchronism of male and female gamete development.10. The S5 locus was verified to govern the embryo sac fertility by analysis of three-way cross population under the background of Nanjing 11.11. The construction of NILs has been commenced.