Fine Mapping Of QTL For The Ratio Of Deep Root On Chromosome 7 In Rice

Rice is one of the most necessary staple crops in China, and drought is an important abiotic stresses which causes severe reduction of rice yield. Root is the main organ of rice water absorption,the cultivars with a deep root system have stronger tolerance to water stress. Studying the genetic diversities of rice and cloning the related genes can help us reveal the drought resistant mechanism on rice fundamentally, In addition, functional genes can be also used in WDR breeding. The ratio of deep root(RDR) reflects the distribution of root system in soil layer, so it is an effective index to evaluate deep root characteristics of rice.Our groups had made the ZhenShan97-IRAT109 linkage map by 213 SSR makers since 2004, according to several years dates, we detected 4 QTLs on Chr1、 Chr2、 Chr4 、Chr7 which explain phenotypic variation of 12.37%、19.07%、12.20%、5.44% respectively. These 4 QTLs have a stable genetic effect as they can be detected in RIL and F2 populations.Based on the results of previous study, we constructed 4 near-isogenic lines using Zhenshan97 B as their backgrounds, and the qRDR-7 was selected for fine mapping.1. 4 NILs(Near Isogenic Lines)construction. Trough more 3 times backcrossing we constructed 4 NILs included q RDR-1、qRDR-2、qRDR-4、qRDR-7 loci, ZhenShan97 B as the background. 203 SSR were used for foreground and background selection from BC2F1,we got the BC3F1 population for qRDR-7,the BC4F1 for qRDR-1 、qRDR-2 qRDR-4. The background homozygosity of all populations are more than 90%.2.The linkage map construction at q RDR-7 loci. A BC3F2 population were derived from NIL of qRDR-7, the topical linkage map at this loci,constructed with 11 newly developed InDel makers and genotype analysis on BC3F2 individuals, was 30 cM at total length, and the average genetic distance of two makers was 2.73 cM.3.Fine mapping of the qRDR-7 QTL.A BC3F2 large population included 10000 individuals was planted in ShangHai for recombinants selecting in June 2015, we got 281 recombination individuals and the seeds of every plant, then 19 representative lines were picked out of these 281 recombination plant for progeny test. The qRDR-7 QTL was delimited to a 36 kb,by analyzing the genotype and phenotype between every homozygous lines. We searched this region through bioinfomatics and found 7 ORFs in this area, of which are 5 predicted protein, the other 2 are unknown protein. The 5 predicted protein are as fellow, two SWIM zinc finger family protein; a MYST-like histone acetyltransferase 1; a amine oxidase family protein; a 4-alpha-glucanotransferase.