QTL Analysis Of Cadmium Tolerance In Rice Seedlings And Cadmium Accumulation In Grains

The cadmium pollution of rice grains is serious and will cause great harm to the human body.To find favorable alleles for cadmium tolerance and low cadmium accumulation in rice,it can provide a theoretical basis for screening and breeding cadmium-tolerant stress and low cadmium accumulation varieties.This study used a set of Chromosome Fragment Replacement（CSSL）populations constructed with Changhui 121as the recurrent parent and Koshihikari as the donor parent,and a set of 85 indica rice germplasm materials from known SNP loci.The QTLs related to cadmium stress and cadmium accumulation in rice seedlings were identified by linkage analysis and association analysis,and candidate genes related to cadmium accumulation in grain were screened.The main results are as follows:1.The cadmium stress treatment of rice seedlings was carried out by hydroponic method using CdCl₂solution with a concentration of 17 mg/L.The hydroponic solution without CdCl₂was used as control.The seedling length,root length,fresh weight,root fresh weight and dry weight of seedlings were used.The cadmium stress index of 6 traits such as root dry weight is cadmium tolerance index,and 50 cadmium stress-related QTLs are detected in three environments,respectively,on chromosomes other than chromosome9.The contribution rate is between 3.23%and 40.40%.These include 9 seedlings with QTLs for cadmium tolerance,QTLs for fresh seedlings with cadmium tolerance,QTLs for cadmium stress tolerance of 6 seedlings,QTLs for cadmium tolerance of 8 roots,and QTLs for cadmium tolerance of 5 roots.9 root dry weight tolerance to cadmium stress QTLs.Among them q TSL1.1 and q TSL8.2 can be repeatedly detected in three environments,q TRL6.1,q TRL7.1,q TSL8.1 can be repeatedly detected in two environments.2.The CSSL population was planted in the cadmium-contaminated environment of Nanchang barrel plant and Dayu County of Ganzhou City.The QTL related to cadmium accumulation in the grain was detected by linkage analysis.Seven QTLs related to grain cadmium accumulation were detected and distributed in On rice 1,7,10,11 and 12,a total of 11.46%to 24.54%of genetic variation was explained.Among the Nanchang potted experiments,the contribution rate of q Cd12 on chromosome 12 was 24.54%,followed by the contribution rate of q Cd1.1 on chromosome 1 22.10%.In the cadmium-contaminated soil experiment,the contribution rate was the highest.The contribution rate of q Cd10 on chromosome 10 was 23.70%.In addition,four QTLs in the QTLs associated with cadmium accumulation in the same grain were found to be in the same position as QTLs for seedlings resistant to cadmium stress.3.The QTLs related to cadmium accumulation in 85 japonica rice germplasm resources planted in cadmium polluted environment in Nanchang were detected by genome-wide association analysis.43 SNPs were identified to be significantly correlated with grain cadmium accumulation.Based on these 43 SNPs,27 QTLs related to cadmium accumulation in the grain were located on 9 chromosomes of rice,distributed on chromosomes 1,2,3,4,5,8,9,10,and 11.Among them,9 QTLs are identical or similar to the previously located QTL regions,and the remaining 18 are unreported QTLs.Two repetitive QTLs were detected by linkage analysis and association analysis,which were located at the RM1117 marker on chromosome 1 and the RM5349 marker on chromosome11,respectively,demonstrating that these two replicate QTLs were stably inherited.4.Of the 27 QTLs associated with accumulation of cadmium in grains,four important QTLs were identified.The candidate gene LOC＿Os01g01450 associated with stress response and the candidate gene LOC＿Os01g02360 associated with the resistance receptor kinase were found around four important QTLs.Through correlation analysis,16 SNP loci with significant accumulation of cadmium in the grain were found on the candidate gene LOC＿Os01g02360 on chromosome 1.Among them,4 SNPs are located in exons,and 3 of them are synonymous mutations.Only the 2802th position is changed from C to A,and the amino acid is changed from alanine to serine.For the mutation,the contribution rate of the locus reached 36.4%.By haplotype analysis of 4 sites in the exon,it was divided into 3haplotypes,of which only b-type mutation occurred at 4 sites,and the mutation rate was3.5%.