| Researchs indicate that the heterosis of the F1progenies of reciprocal crosses exist some difference,this phenomenon is cytoplasmic effect.The heterosis of the cross combination of the restorer line with the maintainer line almost is better than that of the cross combination of the restore line with the sterile line in three-line hybrid rice,this phenomenon is the negative effect of sterile cytoplasm.Two-line hybrid rice systems are more advantageous than three-line hybrid rice systems because of the absence of any cytoplasmic restriction on breeding a nuclear sterile line and high-production combinations,howereve,the breeding of two-line hybrid rice all ignore the cytoplasmic effect.In this project,common wild rice,cultivated rices that originate from the Northen America,the Southern America,Japan,the Philippines were used as the cytoplasmic donors.Zhu-1S and ZhunS were used as the nuclear donors. The cytoplasmic donors were used as female parents in crosses with the nuclear donors, as males.The mononuclear-heteroplasmic sterile lines were prepared via15backcrosses using the original male as recurrent parent.The preliminary results indicate that cytoplasm affect the agronomic traits of the mononuclear-heteroplasmic cross combinations which were prepared by crossing the mononuclear-heteroplasmic sterile lines and four male parents.The genome of mononuclear-heteroplasmic sterile lines will be identified by the molecular markers of SSR in this Study.Base on the identity of the nuclei of mononuclear-heteroplasmic sterile lines,effects of cytoplasm on the mononuclear-heteroplasmic sterile lines and the mononuclear-heteroplasmic cross combinations will be studied,the photosynthetic characteristic of the significant difference of biomass yield of the heteroplasmic sterile and heteroplasmic cross combination will be analysed.This study aim to construct a series of special genetic materials for studing the cytoplasmic effects,and promote promote the further development of the theory of cytoplasmic effect,and provide theoretical support for the best combination of nucleu-cytoplasm in two-line hybrid rice.1,Using9cpDNA sequences have established cytoplasmic molecular fingerprint of8cytoplasmic donors and2nuclear donors, the results showed that ten kinds of cytoplasm had varying degrees of genetic difference.2,The genomes of nuclear donors were analysed using inter-simple sequence repeat(ISSR), Sequence-related amplified polymorphism(SRAP) and target region amplification polymorphism(TRAP) molecular markers. The results showed that two nuclear donors had varying degrees of genetic difference,and the molecular fingerprints of nuclear donors had established.3,The mononuclear-heteroplasmic thermo-sensitive genic male sterile (TGMS) lines were confirmed that their nucleus were identical with the donors of nucleu respectively using516pairs of SSR markers. Meanwhile, no segregation of characters was found in BC11F1-BC12F1 generations of the same substitution line in field experiments.4,The effect of C5cytoplasm on area and width of the flag were positive,whereas the effect of C8cytoplasm on area and width of the flag were negative. The plant height of cross combinations with C7cytoplasm were0.4～11.0cm lower than those of controls. The full growth period of cross combinations with C7cytoplasm were2.2～5.2d shorter than those of controls, The full growth period of cross combinations with C3cytoplasm were0.4～3.1d longer than those of controls.5,In two nuclear backgrounds, the effect of C7cytoplasm on panicle length, spikelet No./panicle of TGMS line were negative. The filled-grain of cross combinations with C3cytoplasm were2.0～8.1percentage points lower than those of controls.The effect of C4cytoplasm on panicle No./plant of cross combinations were positive.6,In two nuclear backgrounds, the differences that the content of photosynthetic pigments, AGY, light compensation point, light saturation point, and ETR of among the mononuclear-heteroplasmic lines were not significant. In ZhulS nuclear background,the net photosynthetic rate, Fv'/Fm', PhiPS2, qP of the substitution line with C5cytoplasm are significantly higher than those of Zhu1S, whereas those of the substitution line with C3cytoplasm were significantly lower than the those of Zhu1S.In ZhunS nuclear background, the net photosynthetic rate, Fv'/Fm', PhiPS2, qP of the substitution line with C8cytoplasm were significantly higher than those of Zhu1S, whereas those of the substitution line with C7cytoplasm were significantly lower than those of ZhulS.7,The effect of C2,C4and C5cytoplasms on the dry weights of above-ground of cross combinations were positive. The dry weights of above-ground of late cross combinations with C2cytoplasm were1.8%～7.6%higher than those of controls, the dry weights of above-ground of early cross combinations with C4cytoplasm were1.7%～7.7%higher than those of controls, the dry weights of above-ground of cross combinations with C5cytoplasm were2.3%～16.8%higher than those of controls. But the dry weights of above-ground of cross combinations with C3cytoplasm were6.7%,18.3%lower than those of controls, The dry weights of above-ground of early-season and mid-season cross combinations with C7cytoplasm were3.9%～19.0%lower than those of controls.8,In the Zhu-1S nuclear background, the least stable pollen sterility was observed in the substitution line with C6cytoplasm, and its critical sterility temperature points(CSTP) were above23.5℃. Hence, this cytoplasm were unsuitable in the ecological region in the middle and lower reaches of the Yangtze River. The substitution lines with C3and C2cytoplasms had more stable pollen sterilities than Zhu-1S, but their fecundities were lower than that of Zhu-1S. In the ZhunS nuclear background, the substitution line with C7cytoplasm had a higher CSTP and the least stable pollen sterility. The substitution lines with C2and C3cytoplasms had the most stable pollen sterility and were suitable for application in the ecological region in the middle to lower reaches of the Yangtze River.All the analysis indicated that the biological traits of mononuclear-heteroplasmic TGMS lines and mononuclear-heteroplasmic cross combinations were controlled by nucleu,but the effects of cytoplasm and interaction of cytoplasm and nucleu on some traits are significant also.In this study,the C2cytoplasm was the most suitable cytoplasm for breeding TGMS lines. The C7cytoplasm was the best cytoplasm for breeding the early season hybrid rice combinations. The C2,C4and C5cytoplasms were excellent candidates for breeding the high-yield hybrid rice combinations.
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