Main QTL Fine Mapping And Genetic Dissection Of Stigma Exsertion Rate In Rice(Oryza Sativa L.)

Rice is the most important food crop in the world,and the application research of rice in various aspects emerges in endlessly.Stigma exsertion rate,as one of the most important agronomic traits of rice,contributes greatly to the commercial production efficiency of hybrid rice seed production,and has gradually become one of the research hotspots.Scientific research shows that the stigma exsertion rate of hybrid rice can improve the efficiency of hybrid rice seed production,so stigma exsertion rate has become one of the effective means of improving characters in commercial hybrid rice seed production technology.Based on our previous work and research,we preliminarily located a major gene controlling stigma exsertion rate in rice and located it on the long arm of chromosome 7.Through previous studies and demonstrations,we detected a quantitative trait locus(QTL)-qSE7(unpublished)controlling stigma exsertion rate on the long arm of chromosome 7 in rice.A chromosome segment substitution line(CSSL)was established by using Xieqingzao B as female parent and Zhonghui 9308 as male parent.The chromosome segment substitution line was based on XQZB as insertion fragment and ZH9308 as background.Further genetic studies and phenotypic analysis showed that the QTL was located between RM5436 and RM5499,with a physical distance of about 1000 kb.By developing new markers and developing secondary populations,we finally located the gene between InDel marker SER4-1 and SSR marker RM5436,with a physical distance of 322.9-kb.Therefore,the results of this study are as follows: 1.A line(C51)was selected from the chromosome segment substitution line and backcrossed with background ZH9308 continuously.From this line,a near-isogenic line (NIL)named NIL(qSE7XB)was developed.The near isogenic line contained XQZB insertion fragments with high stigma exsertion rate,while the other backgrounds were ZH9308 with low stigma exsertion rate.2.Genetic analysis showed that the QTLqSE7 was a single Mendelian factor,and fragments from high stigma exposure rate XQZB could reduce stigma exposure rate.In this study,we hypothesized that qSE7 could simultaneously control single stigma exposure rate,double stigma exposure rate and total stigma exposure rate.The related genetic experiments and phenotypic data identification tests based on qSE7 could provide sufficient experimental evidence to verify the hypothesis and further demonstrate our hypothesis.Correctness and verifiability.3.To further fine-tune the QTL,we combined the related phenotypic data and further located the QTL between SSR markers RM5436 and RM5499,about 1000-kb of physical distance.The analysis of phenotypic data showed that the QTL explained 1.52% of phenotypic variation.4.C51 strain selected from chromosome segment substitution line CSSL was backcrossed with ZH9308,and then further self-pollinated.Secondary population F2(BC5F2)and F2:3(BC5F2:3)were reconstructed.These two secondary populations were used to detect,analyze and verify the role of QSE7.In 4000 F2 and 3200 F2:3(BC5F2:3) populations,we detected,analyzed and validated the effects of the QTL qSE7 by marker identification of genotype and phenotype of each strain.5.In order to further fine-tune the qSE7 to a smaller spatial and physical distance on the chromosome,we developed new insertion deletion markers(InDel),analyzed heterozygote data and combined phenotypic data to locate the qSE7 locus between the InDel marker SER4-1 and SSR marker RM5436,with a physical distance of about 322.9.-kb.The relevant genetic evidence has been obtained.The experimental data such as phenotypic data identification in the two sub-populations also prove the validity and demonstrability of our experimental results once again.6.This study will be helpful for further isolation and identification of candidate genes controlling stigma exsertion rate in rice,and provide reference and basis for fine mapping,gene cloning and molecular marker assisted breeding(MAS).In the near future,it is believed that genes controlling stigma exposure will play an increasingly important role in hybrid rice breeding.