Mapping Of Cadmium Accumulating QTLs For Rice(Indica)

With the development of modern industry and agriculture,the increasing environmental pollution has been a great threat to food safety and human health.One of the most serious contaminants is heavy metal pollution in soil.It is reported that one-fifth of farmland in China is polluted and cadmium is one of the most important pollutants.Rice is one of main food crops in China and taking food from rice contaminated with cadmium would be toxic to human health.To reduce cadmium accumulation in rice,many methods have been developed,such as displacing polluted soil or using other plants to absorb cadmium.Unlike these methods,we try to breed new rice cultivars with lower cadmium accumulation in seeds.Absorption and accumulation of cadmium in rice is controlled by many loci,which is known as quantitative trait loci(QTL),and is differentiated among rice cultivars.Analysis on accumulation of cadmium and quantitative trait loci(QTL)in these cultivars will facilitate us to discover new QTLs that can be used for molecular breeding.To this aim,more than 200 indica rice cultivars were grown twice in Liantang Village,Shaoguan city,where is heavily polluted by cadmium,and once in our experimental field,SCBG,Guangzhou city,by adding cadmium artificially from 2014 to 2016.Cadmium accumulation in seeds among cultivars was investigated with from 0.031 to 0.153 mg/kg in the first batch,from 0.034 to 0.162 mg/kg in the second one and from 0.211 to 3.516 mg/kg in the third one.Correlation analysis was performed pairwise in the same cultivar among the three times and higher correlation was found between the first and second batches,which may be due to the same growing place for the first and second batches.By whole genome association analysis(GWAS)between cadmium accumulation and single nucleotide polymorphism(SNP),we found 39 SNPs that may involve in the accumulation of cadmium in indica rice.Finally,we obtained 9 QTLs that may involve in the accumulation of cadmium in indica rice by linkage disequilibrium analysis on 50 kb region upstream or downstream significant SNPs and Gene Ontology(GO)analysis on 20 kb region upstream or downstream significant SNPs.The repeatability of our experiment is bad,so we need to plant rice and analyze data again.In addition,we must do more experiments to verify the reliability of our QTLs.