| Rice growing area in China is30,670,000ha each year, Japonica rice growing area is8,280,000ha. The area planted with japonica hybrid rice only occupied3-5percent of the total area of japonica rice in China, still having large room for further development. Yield heterosis in hybrid japonica rice(Oryza sativa L.) is mainly due to large panicles. However, large panicles lead to poor plumpness for a number of fertilized grains which limited the realization of yield heterosis. The major point of improving grain plumpness is to improve the grain filling.’Ludao’is a kind of natural born rice with black hull, long awn, and strong tillering ability. And’Ludao’has shorter filling time and faster filling rate in paddy field. It is very helpful for improving the grain plumpness of habrid japonica rice to map the QTL related to grain filling trait in Ludao and to introduce the elite allele into japonica restorer line by MAS. Genetic segregation analysis of grain filling rate were made by using the methods of components of means and the mixed major gene plus polygene inheritance models with segregating generations of Ludao and a restorer line C-Bao in Japonica Rice (Oryza sativa L.) in our laboratory, and the results showed that The inheritance of average grain filling rate fitted additive-dominance-epistasis model based on the analysis of components of means. The average filling rate was controlled by two major genes with additive-dominance-epistatic effects plus polygene with additive-dominance-epistatic effects based on the mixed major gene plus polygene inheritance madels, and was mainly governed by major genes. And then a BaoLuBao (C Bao/Ludao//C Bao) BIL population with102lines was created by single-seed descent method from the previous back-crossing population. Two researches were done in this study based on the previous works, the first one, the trait of grain-filling rate was investigated in six grain-filling stages in2010and2011using BaoLuBao BIL population. Combining the SSR genetic linkage map, three QTL mapping methods, including unconditional QTL mapping, dynamic QTL mapping based on the time-related trait value and conditional QTL by adjusted the grain weight to an identical level, were used to detected the QTL controlling grain-filling rate. The second one, a chromosome segment substitution line (CSSL) population was developed using "LuDao"as donor and C Bao as recipient by SSR molecular-assisted selection and successive back-crossing+self-crossing. Main results obtained were as follows.1. Ten unconditional QTLs and fifteen pairs of unconditional epistatic QTLs were detected in total using the two kinds of computer software of QTLmapper2.0and WinQTLCart2.5. The ten unconditional QTL distributed in chromosome1,4,5,6(two loci),8,9and10(two loci). The positive alleles of four loci were from LuDao.qGFR9.1, which located at RM1328-RM3912of chromosome9, was detected by the two genetic models, the contribution rate was12.62%(mixed inheritance model) and38.46%(multiple regression model) respectively, and the additive effect was0.10mg per grain per day and0.14mg per grain per day, respectively. qGFR10.2, which located at RM1146-RM3773of chromosome10, was detected by the two genetic models, the contribution rate was7.17%(mixed inheritance model) and16.57%(multiple regression model) respectively, and the additive effect was0.07mg per grain per day and0.09mg per grain per day respectively. Six unconditional QTLs, with positive alleles from C Bao, were qGFR1.2located at RM237-RM5389of chromosome1,qGFR1.2located at RM8105-RM84of chromosome1, qGFR4.1located at RM518-RM3471of chromosome4,qGFR6.1located at RM3330-RM162of chromosome6,qGFR6.2located at RM6811-RM5753of chromosome6and qGFR10.1located at RM3470-RM1125of chromosome10.2. Eight dynamic QTLs based on the time-related phynotypic data and thirteen pairs of epistatic QTLs were detected in total using the two genetic models. The eight QTLs were distributed in chromosome1,2,5,6(two loci),8,9and10. The positive alleles of five QTLs were from Ludao. Locus qGFR10.2was detected by two genetic models, and the contribution rate was9.35%(mixed inheritance model) and17.18%(multiple regression model), and the additive effect of this locus was0.06mg per grain per day and0.09mg per grain per day. Three dynamic QTLs, with positive alleles from C Bao, were qGFR1.3located at RM5-RM5461of chromosome1,qGFR2.3located at RM3688-RM6617of chromosome2and qGFR6.6located at RM510-RM225of chromosome6.3. After grain weight was adjusted to an identical level, thirteen conditional QTLs and eleven epistasis QTLs were detected using the2genetic models. The thirteen QTLs were distributed in chromosome1(two loci),4.5,6(three loci),8,9and10(two loci). The positive alleles of eight QTLs were from Ludao. Locus qGFR9.1was detected by two genetic models, and the contribution rate was12.15%(mixed inheritance model) and 34.05%(multiple regression model), and the additive effect of this locus was0.07mg per grain per day and0.10mg per grain per day, respectively. Locus qGFR10.2was also detected by two genetic models, the contribution rate was7.17%(mixed inheritance model) and16.58%(multiple regression model), and the additive effect was0.07mg per grain per day and0.09mg per grain per day. Five conditional QTLs, with positive alleles from C Bao, were qGFR1.1located at RM237-RM5389of chromosome1,#GFR1.3located at RM5-RM5461of chromosome1,qGFR4.1located at RM518-RM3471of cheomosome4, qGFR8.1located at RM3572-RM4085of chromosome8and qGFR10.1located at RM3470-RM1125of chromosome10.4. A CSSL population composed of55lines was developed used "Ludao" as donor and C Bao as recipient by a combination of backcross and MAS. The CSSL population covered96.54%of Ludao genome. Among the55lines, four lines had seven donor fragments, one line had six donor fragments, seventeen lines had five donor fragments, thirteen lines had four donor fragments, eleven lines had three donor fragments, four lines had two donor fragments, and five lines had only one donor fragement, which located in chromosomes8,1,1,6,6, respectively, and spanned51.2cM with about3%of the total donor’s genome. The most introgression frequency of Ludao alleles was18.42%, the least was0.44%and the average was4.72%.5. Six introgression lines, i.e., K111005-1,K111005-2, K111005-6, K111010-5, K111010-2and K111010-7, were heterozygous at the locus of qGFR9.1, which contained the donor’s positive alleles, flanked by marker interval of RM1328-RM3912. Introgression lines K111009-1, K111009-5, K111009-10and K111011-7had the donor’s positive alleles of RM1108-RM3773which covered QTLqGFR10.Summaring the screeing results, we found qGFR9.1and qGFR10.2were the two major QTLs, which were detected by two genetic models; both of Ludao and C Bao had the positive alleles controlling the grain-filling rate; one positive allele from Ludao had a significantly genetic effect in different grain-filling stages. Pyramiding the positive alleles from different parents and different grain-filling stages might be helpful for improving the grain-filling rate of hybrid japonica. There were ten CSSLs could be used to fine map the gene for grain filling rate further. |
PDF Full Text Request