Dynamic Analysis Of QTL For Grain-filling In Rice (Oryza Sativa L.)

Understanding the factors that regulate grain filling is important for improving rice yield potential.However,there is disagreement as to whether improving sink size alone in rice crops will also result in an increase in leaf and whole plant photosynthesis.The grain yield in rice is the product of spikelet yield(or sink)and ripening ability(or source),the relationship between the source and sink in rice research in general level and the QTL mapping methods are used to research the relationship of source and sink is benefit for us.Thus a RIL including 130 offspring was built in order to study the character of dynamic QTLs during the grain-filling.In our study,We compared the correlation between the plant phenotype and the grain-filling rate,found that the day-to-heading was significantly negatively correlation to first stage grain-filling rate and positively correlation to the fourth stages(r=0.175;P＜0.01)and fifth stages grain-filling rates(r=0.155;P＜0.01).The height of plant had a significant positive correlation with the five stages grain-filing rate,their relevance of the order was third stage grain-filling rate(r=172;P＜0.01),second stages grain-filling rate(r=0.141;P＜0.01),first stage grain-filling rate(r=0.130;P＜0.01),fifth stage grain-filling rate(r=0.104;P＜0.01), forth stage grain-filling rate(r=0.126;P＜0.01).For the first stages,a significantly negative correlation was observed with the width of third flag from the top,the correlation coefficient was-0.136(P＜0.01).Scanning the entire five grain filing stages,between the current stages filling rate and the last stage grain-filling rate showed a significant negative correlation. Through a composite interval mapping,40 QTLs were detected for the 11 source-related traits. In addition,10 of the 12 chromosomes have been mentioned except for 10 and 11 chromosomes.Correlations between net photosynthetic rates and grain-filling rate were calculated.There was no significant correlation between first net photosynthetic rate and the grain-filling rates. The second stage net photosynthetic rate had weak negative correlation with the fifth stages grain-filling rate(r=-0.118,P＜0.05).There was a small positive correlation between third stage net photosynthetic rate and third stages grain-filling rate(r=0.117,P＜0.05).A negative correlation was mentioned between the forth stages net photosynthetic and fifth stage grain-filling rate(r=-0.122,P＜0.05).A total of 12 QTLs loci related to five stages net photosynthetic rate were detected.These QTLs were located on 8 out of 12 chromosomes except chromosome 3,5,6 and 10,with contributions from 6%-23%.At the last two stages, qNPR-12-1 for the forth stage net photosynthetic rate and qNPR-12-2 for the fifth stage net photosynthetic rate were detect on the same region.The leak correlation was found between first stage gain-filling rate and second stage grain-filling rate(r=-0.126,P＜0.05).Significant negative correlations also found between second stage grain-filling rate and the third stage grain-filling rate(r=-0.223,P＜0.01),and between third stage grain-filling rate and forth stage grain-filling rate(r=-0.230).There was a negative correlation between third stages grain-filling rate and fifth stage grain-filling rate, which the correlation coefficient was -0.133(P＜0.01).Totally 18 QTLs were detected with the characters of five stages grain-filling rate and mean of grain-filling rate after heading.One putative QTL were detected on chromosome 2 at 6 day after heading.Three QTLs were detected on the chromosome 4 and 7 at 12 day after heading.Three putative QTL were detected on chromosomes 1,7 and 8 at 18 day after heading.Moreover two QTLs were detected on chromosomes 11 and 12 at 24 day after heading.Furthermore,three QTLs were detected on the chromosomes 4,9 and 12 at 30 day after heading.At the same time six putative QTLs were detected on the chromosomes 2,6,7 and 8 for the character of mean of grain-filing rate.The first stage first stage panicle weight were positively correlated with the first grain-filling rate(r=0.435,P＜0.01)and fourth stage grain-filling rate(r=0.177,P＜0.01).the second panicle weight had significant correlations with the first stage grain-filling rate and second grain-filling rate(r=0.419,P＜0.01),forth stage panicle weight also had the same significant correlation with the second stage grain-filling rate and forth stage grain-filling rate the third panicle weight had a significant correlation with the second(r=0.231,P＜0.01)and third stages grain-filing rate(r=0.253,P＜0.01).For the fifth stage panicle weight,the. correlation with the fourth stage grain-filling rate(r=0.231,P＜0.01)and five stage grain-filling rate(r=0.138,P＜0.01)were observed during the last half of grain-filling stage.A total of 14 QTLs for 6 traits was identified by the analyses in common.Four significant QTLs were identified on chromosome 1,4,7 and 10 for the first stage panicle weight.One QTLs were associated with second stage panicle weight were identified in the RM279 and RM213 zone. Three significant QTLs were identified with R2 ranging from 0.1 to 0.12 for the third stage panicle weight.Two putative QTLs(qPW-4 and qPW-6)for fourth stage panicle weight were detected on chromosome 4 and 6,respectively.Only one putative QTL(qPW-6-2)with a LOD score 2.40 was detected on chromosome 6 for fifth stage panicle weight.Three QTLs(qPL-4-2, qPL-6-2 and qPL-10-2)significantly affecting panicle length were detected on chromosomes4, 6 and 10.We further discussed the interaction between rice grain-filling source components QTL and the QTL for grain-filling rate.Also discussed the interaction of QTL for flag leaf net photosynthetic rate and genetic filling rate,as a components office sink,the panicle weight performed dynamic characteristics which grain-filling rate also have the same dynamic characteristics in different grain-filling period.This research regarding the source and the sink carries on separately QTL mapping at different stages in rice,this also in a sense has promulgated grain filing process in the rice is a gene dynamic expression process,simultaneously is also a interactive action between the gene and gene in the process,this is willing to have certain significance without doubt regarding the breeding work's practice.Simultaneously the gene dynamic expression and interaction cannot only depend on the QTL method to make the simple analysis.Understanding the gene expression in space and time characteristic,this also need to do more work.In the different levels,such as RNA protein level.