Fine Mapping Of Deep Rooting Ratio Of QTL-qRDR-7 In Rice

With global warming,climate change had a serious impact on the ecological environment,precipitation distribution and food production.Drought has become an important threat to the security of global food production.Rice（Oryza sativa L.）is a staple food for more than half of the world’s population.The cultivation of water-saving and drought-resistant rice is one of the important ways to solve the contradiction between the severe production environment and the increasing demand for rice yield.Root system is an indispensable organ of rice,which directly affects many important aboveground characters of rice.In the distribution of rice roots,the higher the ratio of deep rooting can enhance the ability of drought.It is helpful to excavate the mechanism of drought resistance and enrich the information of stress resistance genes by locating the genes controlling the ratio of deep root in rice.Using the Recombinant inbred line population（ZS97/IRAT109）,we mapped six major QTL to control the ratio of deep rooting in rice,and preliminary fine mapping qRDR-7 located on chromosome 7.It is found that the QTL is not located in the initial interval（RM134-RM478）,the study had shown that it is on the left of RM478.On this study,we further fine mapping the qRDR-7.The results are as follows:1.Screening the polymorphic molecular markers in qRDR-7 localization interval:according to the location of qRDR-7 has been located in the left side of RM478（25.9Mb）and parental re-sequencing results,a total of 217 pairs of primers were discovered,in the interval of 25Mb-26Mb.Then,60 pairs of makers were selected for polymorphic screening.12 pairs of polymorphic markers were selected for fine mapping.2.Recombination screening and exchange position:Near isogenic lines BC₄F₃develop a population of 7000 plants.It was found that the exchange sites are all located in the right side of the R7Q89 with detection of small random population.We infer qRDR-7is located at R7Q89-RM478.74 recombinants exchange strains were screened by marker R7Q89 and RM478.12 pairs of encrypted markers were used to genotype the target sections.10 exchanged sites cover the whole target area.3.Fine mapping of qRDR-7:11 F₄ families with different recombination exchange sites were selected from 74 recombinant plants.Each family selected 60 healthy seedlings were selected to detect the ratio of deep rooting phenotype by"basket method".R7Q89-R7Q106 and R7Q106-R7Q146 are obtained by analysis.In order to further determine the QTL interval,five families were selected to confirm the above two sections by using the basket method.The genotypes were detected with markers on both sides of the exchange site.Six seedlings with two parent genotypes were selected from each family to determine the ratio of deep rooting.The results show that qRDR-7 is located between R7Q133-R7Q146,and the interval is 58kb.4.Candidate gene screening based on expression:there are 7 candidate genes in R7Q133-R7Q146:LOC_Os07g42600,LOC_Os07g42610,LOC_Os07g42620,LOC_Os07g42626,LOC_Os07g42632,LOC_Os07g42640 and LOC_Os07g42650.RNA was extracted from the root tip of the parents of ZS97 and IRAT109.The realtime PCR analysis was carried out to detect the difference of the relative expression of the genes in the root tip tissues of different parents.