| Rice is the most important crop in the world. However, the growth and production of rice are limitted frequently by some abiotic stresses, such as salinity, drought, and low temperature. Therefore, improving the abiotic stress tolerance in rice has become one main objective of rice research. Two recombine inbred lines (RILs) populations were used to investigate the genetic control of rice seed germination under salt and cold stress in this thesis.In the last decade, the development of rice molecular linkage maps has provided powerful tool to carry out rice genomic researches, such as QTL mapping, map-based cloning, comparative genomics, genetic diversity research and marker-assisted selection breeding. Here, two F2:1 recombinant inbred lines (RILs) populations, IR26/Jiucaiqing and IR28/Daguandao, respectively, derived from a cross between IR26 (Oryza sativa L. spp. indica) and Jiucaiqing (japonica), and IR28 (indica) and Daguandao (japonica), were used to construct two SSR molecular linkage maps. The results showed that the DNA polymorphism between parents of IR26/Jiucaiqing and IR28/Daguandao were similar, with polymorphic rate 42.2% and 44.3%, respectively. There were 57 and 74 SSR loci showing genetic distortion, mainly partial to indica parents, among IR26/Jiucaiqing and IR28/Daguandao genome, respectively, with the segregation distortion rate 42.2% and 44.3%. The genotype of each line at each chromosome was analyzed; there were genetic distortion lines in two RILs with segregation distortion rate 47.2% and 52.9%, respectively. The distribution of paternal contribution was normal in progenies which illustrated that genetic contributions from the parents were equals, and some lines with similar genotypic components in two RILs. In addition, the two genetic maps of IR26/Jiucaiqing and IR28/Daguandao covered 2225.3 cM and 1846.6 cM of rice genome, respectively, with the average interval of 16.5 cM and 11.1 cM, which were suitable for QTL mapping. The two maps differed in mapped markers, sequenced order of markers, genetic distance and average distance on the maps. Finally, six and eight segregation distortion regions (SDRs) were detected on IR26/Jiucaiqing and IR28/Daguandao chromosomes, respectively, three new SDRs (SDR 2, SDR 4-2, SDR 12-1) were detected here, and several gametophytic genes (ga) and sterile gene (s) were located near some SDRs, indicating that segregation distortion could be partially caused by gametophytic genes and sterile genes.One F2:9 recombinant inbred lines (RILs) population, derived from a cross between IR26 (Oryza sativa L. spp. indica) and Jiucaiqing (japonica), was used to determine the germination ability including imbibition rate, germination rate, germination index, root length, shoot length and vigor index under control (water) and salt stress (100 mM NaCl) for 10 d. A major gene plus polygene mix inheritance model and the composite interval mapping (CIM) were applied to conduct genetic analysis for germination ability. The results showed that the performances of rice seed germination were mostly limited by salt stress and the early germination stage (0-5 d) might be the salt sensitive stage in rice. There were significant differences in all germination traits under salt stress among RILs. Correlation coefficients among the germination traits, except the imbibition rate, under salt stress were all positively significant. The frequency distributions of germination traits in RILs population showed continuous segregation, suggesting these were quantitative traits controlled by several genes, and more RILs were skewed to salt sensitive type. Each trait was controlled by the specific genetic model:imbibition rate controlled by two major genes, germination index and vigor index controlled by two major genes plus polygene, germination rate and shoot length regulated by three major genes plus polygene, and root length controlled by two major genes or two major genes plus polygene, and mainly dominated by major genes with high heritability values, accounted for 12.5%-99.0% of the total phenotypic variation. In the control group, twelve QTLs were identified:two for imbibition rate (qIR-8 qIR-10), one for germination rate (qGR-7), one for germination index (qGI-2), four for root length (qRL-1 qRL-4 qRL-9 qRL-10), two for shoot length (qSL-7 qSL-11) and two for vigor index (qVI-6 qⅥ-7), respectively, accounting for 12.5%-25.5% of the total phenotypic variance individually. In the saline group, four QTLs were identified: two for imbibition rate (qIR-4 qIR-9), one for germination rate (qGR-2) and one for vigor index (qⅥ-8), respectively, explaining 9.1%-46.6% of the total phenotypic variance individually. One major QTL qGR-2 was explaning 46.6% of the total phenotypic variance. The expression of QTLs was developmentally regulated and growth stage-specific. Most of the QTLs observed here were located in regions similar to the QTLs for rice salt tolerance reported previously, but qⅥ-8 and qGI-8 are reported here for the first time.One F2:9 recombinant inbred lines (RILs) population, derived from a cross between IR28(Oryza sativa L. spp. indica) and Daguandao (japonica), was used to determine the germination ability including imbibition rate, germination rate, germination index, root length, shoot length and vigor index under control (30℃) for 10 d and cold stress (14℃) for 23 d. A major gene plus polygene mix inheritance model and the composite interval mapping (CIM) were applied to conduct genetic analysis for germination ability. The results showed that the performances of rice seed germination were mostly limited by cold stress and there were significant differences in all germination traits under cold stress among RILs. Correlation coefficients among the germination traits, except the imbibition rate, under cold stress were all positively significant. The frequency distributions of germination traits in RILs population showed continuous segregation, suggesting these were quantitative traits controlled by several genes, and more RILs were skewed to cold sensitive type. Each trait was controlled by the specific genetic model:imbibition rate, root length, shoot length and vigor index controlled by two major genes plus polygene, germination rate controlled by two or three major genes and germination index regulated by two major genes, and mainly dominated by major genes with high heritability values, accounted for 26.4%～95.3% of the total phenotypic variation. In the control group, eleven QTLs were identified:three for imbibition rate(qIR-6 qIR-9 qIR-11), two for germination index (qGI-1 qGI-7), two for root length (qRL-11 qRL-12), two for shoot length (qSL-8 qSL-9) and two for vigor index (qVI-2 qVI-9), respectively, accounting for 15.1%～32.4% of the total phenotypic variance individually. In the cold group, seven QTLs were identified: two for imbibition rate (qIR-6 qIR-9), one for germination rate (qGR-4), two for germination index (qGI-4-1 qGI-4-2) and two for root length (qRL-4-1 qRL-4-2), respectively, explaining 9.1%～37.0% of the total phenotypic variance individually. One major QTL qIR-6 explained for 31.0%～34.5% of the total phenotypic variance, and another major QTL qGI-4-2 accounted for 37.0% of the total phenotypic variance. The expression of QTLs was developmentally regulated and growth stage-specific. Most of the QTLs observed here were located in regions similar to the QTLs for rice cold tolerance reported previously, but qRL-4-2 is reported here for the first time.
|
PDF Full Text Request