Breeding Dual-purpose Genic Sterile Rice With Low Cadmium Accumulation Using Molecular Marker-assisted Selection

Rice is the largest staple food crop in China and its edible safety takes a very important role in ensuring human health.Excessive cadmium content in rice grain is an important factor that leading to rice food insecurity and endangers human health.Breeding rice cultivar with low accumulation of cadmium is an important way to solve this problem.Recently,OsLCT1,OsHMA3 and qlGCd3 have been identified as genes/QTL conferring low accumulation of cadmium in rice and Pi1,pi47,pi48 and pi49 have been identified as the dominant and main effect rice blast gene with broad-spectrum resistance.In this study,several recombinant inbred lines,which derived from NPB/R1126 cross,carrying low cadmium gene OsLCT1 and Os HMA3,and the variety named LAC23 which carries gene of Pi1 and qlGCd3,were used as the donor parents,respectively.Yun-9S and Chuang-5S were used as the receptor parents,respectively.The genes/QTL related to low cadmium accumulation were introduced to Chuang-5S or Yun-9S by successive backcross combined with molecular marker assistant selection.Six dual-purpose genic sterile rice lines,which carried both low cadmium accumulation genes and blast resistance genes,were developed.The cadmium accumulation characteristics and main agronomic traits of those improved lines were evaluated.The main results were as follows:1.Ten SSR markers including OsLCT1-1,OsLCT1-8,RM21260,RM21268,RM1352,RM16153,RM5766,K107,RM224 and LY2,which showed obvious and stable polymorphism between any crosses of donor and receptor parents,were screened and used to analysis the target genes,respectively.2.BC₂F₂ plants,which harbor at least one cadmium low accumulation gene/QTL,respectively,were screened,by using backcross method combining with marker assisted technology.Including 1)two lines with OsLCT1,OsHMA3 and one lines with Pi1 and qlGCd3 based the genetic background of Yun-9S;2)two lines with OsLCT1,OsHMA3,Pi49and one line with OsLCT1,OsHMA3,qlGCd3,Pi1,Pi47 and Pi48 based the genetic background of Chuang-5S.3.After investigating the main agronomic traits including plant height,panicle length,grain number per spike,effective tillering number,primary rachis branches number and secondary rachis branches number of the BC₂F₂ improved lines,it was found that the improved lines of Yun-9S were consistent with receptor parent Yun-9S,and the improved lines of Chuang-5S was almost consistent with receptor parent Chuang-5S.4.The content of cadmium in brown rice of six improved dual-purpose genic sterile rice and their parents was detected.The results show that the content of cadmium in improved sterile rice was significantly lower than that of receptor parents and indicating that the cadmium low accumulation gene had been successfully introduced into the receptor parent and expressed stably.The study confirmed that molecular marker assisted selection technology is a reliable technical approach to bred rice with cadmium low accumulation.