Fine Mapping Of QTL-qRDR-2 For Ratio Of Deep Root On Chromosome 2 In Rice

Oryza sativa is one of the most important food crops in the world,and drought is a severe abiotic stress.In recent years,the greenhouse gases and the acceleration of urbanization have exacerbated the shortage of water resources in China,so the research of water saving and drought resistance rice is very important.Root is an important organ of absorbing water in rice.Deep root can improve the drought resistance of rice.Therefore,molecular marker assisted selection and fine mapping could help us understand the mechanism of drought resistance,accelerate the drought-resistant breeding process and play an important role in food security to China.In 2004,the recombinant inbred lines?RILs?population was constructed by Zhenshan 97B and IRAT109 and the linkage map was constructed by 213 simple sequence repeat markers.These QTLs can be repeatedly detected in different environments.We found that four deep root QTLs were detected in Chr1?Chr2?Chr4?Chr7,then four near-isogenic lines with target QTLs were constructed by backcrossing with zhenshan97B,the major QTL-q RDR-2 on chromosome 2 was fine mapping,the results were as follows:1.Target QTLs and background detection in BC₄F₁:BC₄F₁ was constructed by background and foreground selection with the target QTL which was double heterozygote of RM6 and RM240.32 plants were selected among 63 BC₄F₁ plants,in the spring of2015.2.q RDR-2 recombinant plants selection and determination of recombination exchange position:The BC4F1 containing the target fragment was developed into 8000 F₂population and RM6 and RM240 was genotyped,289 recombinant plants were detected.The genotypes of makers were analysized,14 markers loci were recombinized,including22 recombinant plants.3.q RDR-2 fine mapping:22 BC₄F₃ which contain 42 plants grew in Langxia,Jinshan Distriction,Shanghai in June of 2016.Combining the detection of molecular marker genotypes and phenotypes which detected by the"basket"method,QTL-q RDR-2was mapped between Q2-323 and Q2-12 with 570 kb.4.The second recombinant plants selection and determination of recombination exchange position.Based on the result of first fine mapping,BC4F4 containing the target fragment was developed into 4000 plants.Q2-323 and Q2-12 were genotyped,106recombinant plants were detected.The genotypes of makers were analysized,6 markers loci were recombinized,including 14 recombinant plants.5.Candidate genes prediction:Seven candidate genes were detected in the target segment by bioinformatics analysis,combined with the laboratory RNA-seq data,including LOC_Os02g48360,LOC_Os02g48710,LOC_Os02g48770,LOC_OS02g49160,LOC_Os02g49440,LOC_Os02g49460,and LOC_Os02g49720.The LOC_OS02g49160was a known gene OsPIN1.