| 93 elite rice (Oryza sativa L.), including conventional varieties, hybrid parents, were analyzed with SSR markers. And also the combining ability of 30 hybrid rice and their 5 elite sterile lines and 6 restorer lines were analyzed with Griffing's diallel cross IV method. 4 newly varieties were added to the former 30 combinations to be used as principal components analysis, correlation analysis, regression analysis and path analysis. The hybrid varieties released in Sichuan from 1985 to 2003 were investigated in yield improvement and genetic analysis. The main results are as follows:l.SSR marker; can accurately distinguish Indica and japonica and have larger molecular polymorphism than that of japonica. SSR polymorphism can reflect the genetic relationship among different varieties. Despite genetically diverse rice resouces, the genetic background of skeleton breeding lines is much limited. The genetic distances between elite sterile lines and restorer lines are much larger than that within each of the two parent groups. Genetic distance has some relationship with heterosis. Compared with clustering analysis with molecular markers, the dendrogram based on agronomic traits is much affected by environment and can hardly reflect the genetic essence of the examined lines.2.The polymorphism of (CT)n of PCR products amplified by microsatellite marker 484/485, and the relationships between Wx genotype and amylose content (AC) were studied. The correlation coefficient of Wx genotype and AC is 0.867** reached very significant level. WxlWxl and Wx2Wx2 genotypes showed significantly lower amylose content and Wx3Wx3 genotype higher amylose content. A PCR-Acc I molecular marker has been developed and used to determine whether the first nucleotide of splice donor site of waxy intron 1 is G or T in 93 rice cultivars lines collected from different areas. Most Wx1 Wx1 and Wx2Wx2 genotypes are TT genotypes and most Wx3Wx3 genotypes are GG genotypes. The correlation of Wx genotype and PCR-Acc I genotype is 0.881** with very significant level.3.We established a fingerprint map database of elite rice breeding lines with three groups of SSR markers. With one 1:0 three SSR markers, we can efficiently distinguish anyone of the 26 elite rice breeding lines from others. This poses a bright usage potential for the detection of variety identity and seed purity. We successful established the fingerprint map of a much spread variety, Diyou 527, and accurately examined the purity of its commercial seed.34.According to the combining ability, principal components and path analysis, G46, Mianhui 725, and Shuhui 527 are the top three lines with their best yield and yield traits performances. Three combinations, including G46/Shuhui527, G46/Mianhui725 and D62/Shuhui527, have significantly the best yield and yield traits performances than other combinations. Source traits, such as photosynthesis efficiency and leaf area index, do not show significant difference. The improvement of rice yield is much attributed to the increase of a sink traits, grain weight per panicle.5.Based on the analysis of hybrid varieties approved within the resent 24 years, we find that the main effort of Sichuan rice breeding is being used to make more late maturing hybrids, and such hybrids accounted for 60.4% of the total approved combinations. The yield level were enhancing yearly with its components traits, such as grain number per panicle, 1000-grain weight, grain weight per panicle and panicle grain yield potential, increasing. The increase of rice yield is mainly attributed to the increase of grain weight per panicle, which is further influenced by grain number per panicle and 1000-grain weight. The result is finely coincide with the former incomplete diallel cross analysis.6.The research indicates that pyramiding excellent genes and regulating yield concerning (or components) traits see two most effective approaches to enhance rice yield. Among yield make-up traits, grain weight is most important. So heavy panicle is the most important characteristic that br... |
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