Abstract
To reduce cadmium (Cd) accumulation in the grains of rice Chuang-5S (C5S), a gene OsHMA3 and a QTL qlGCd3 related to low-Cd accumulation were separately introgressed into the recipient parent C5S (male sterile line) by molecular marker-assisted breeding. The recurrent parent C5S was then replaced by NIL (near-isogenic line)-C5S with the blast resistance gene Pi48 or Pi49 to construct the BC(2)F(1) generation. Finally, two groups of improved materials of C5S, which pyramided the gene/QTL associated with low-Cd accumulation and blast resistance gene, were developed. The Cd accumulation, agronomic traits, genetic background and blast resistance of these improved C5S materials were evaluated. The results showed that the average Cd content of improved C5S material carrying OsHMA3 and qlGCd3 was, respectively, reduced by 52.8% and 50.8% compared with that of C5S, indicating that the gene related to low-Cd accumulation was, successfully, transferred to C5S with stable expression. The main agronomic traits of the improved materials were consistent with those of C5S. Besides, the improved C5S lines showed stronger blast resistance than C5S and more than 88% similarity to the genetic background of C5S. These two groups of improved materials may be further utilized for the breeding of advanced male sterile lines or superior hybrid rice.