Mapping of QTL for Iron and Zinc Toxicity Tolerance at Seedling Stage Using a Set of Reciprocal Introgression Lines of Rice

Ferrum and zinc are essential microelements for rice.However,rice growing in lowland or acid soil is easily subjected to ferrous iron and zinc toxicities which harm plant growth and finally result in deduction of biomass and yield in production.The aim of this study was to identify quantitative trait locus(QTL)underlying ferrous iron toxicity tolerance(FTT)and zinc toxicity tolerance(ZTT)of rice using a reciprocal advanced backcross introgression lines,which was derived from the cross between Lemont(japonica)and Teqing(indica),and 308 evenly distributed single nucleotide polymorphism(SNP)markers developed from the two parents.A total of 42 putative QTLs affecting shoot height(SH),shoot dry weight(SDW),and root dry weight(RDW)under control and stress conditions and for the relative value of the stress to the control were detected,the alleles at most loci improving the tolerance of ferrous and zinc toxicities were from Lemont.Among them,only four QTLs(9.5%)were detected under the two backgrounds,indicating the expression of most QTLs is specific to genetic background.Nine QTLs were detected from the same genetic background affecting the tolerance of both ferrous and zinc toxicities,in which QSdw5 was expressed under the two backgrounds with the same direction and similar quantity of gene additive effect,suggesting that there is a genetic overlap between FTT and ZTT at seedling stage in rice.It is likely,therefore,to improve Teqing's FTT and ZTT by introgressing and pyramiding Lemont favorable alleles at the overlapping QTLs via marker-assisted selection.