Grain size influences the yield and quality of rice (Oryza sativa L.), and grain length is one of the component traits of grain size. In this study, a near-isogenic line LB3 with long grain size was constructed using japonica rice cultivar 02428, with short grain size, as the recipient parent and indica rice cultivar ZYX, with long grain size, as the donor parent, by multi-generation backcrossing and selfing. BSA-seq was used for preliminary QTL mapping and InDel markers were developed to fine map the locus. The major QTL, tentatively named qGL10, for grain length was located in a 128.45 kb region of chromosome 10. Combined with haplotype analysis of rice varieties, expression pattern analysis of candidate genes suggested LOC_Os10g39130 (OsMADS56) as a candidate gene. Sequence alignment of OsMADS56 in 02428 and LB3 revealed that there were 15 SNPs in the promoter region and four in the coding region. Further haplotype analysis suggested that SNP9 (G/A) located in the TGTCACA motif might account for the different expression levels of OsMADS56 in 02428 and LB3. These results lay a foundation for the application of qGL10 in molecular breeding of new rice varieties.

粒级影响水稻（ Oryza sativa L.）的产量和品质，粒长是粒级的组成性状之一。本研究以短粒粳稻品种 02428 为受体亲本，以长粒籼稻品种ZYX为供体亲本，通过多途径构建近等基因系 LB3。世代回交和自交。BSA-seq 用于初步 QTL 作图，开发 InDel 标记以精细定位基因座。籽粒长的主要QTL，暂定为qGL10，位于10号染色体128.45 kb区域。结合水稻品种的单倍型分析，候选基因的表达模式分析表明LOC_Os10g39130 ( OsMADS56 ) 作为候选基因。OsMADS56在02428和LB3的序列比对显示启动子区有15个SNP，编码区有4个。进一步的单倍型分析表明，位于 TGTCACA 基序中的 SNP9 (G/A) 可能解释了OsMADS56在 02428 和 LB3 中的不同表达水平。这些结果为qGL10在水稻新品种分子育种中的应用奠定了基础。