A thorough understanding of the genetic basis of rice grain traits is critical for the improvement of rice (Oryza sativa L.) varieties. In this study, we generated an F2 population by crossing the large-grain japonica cultivar CW23 with Peiai 64 (PA64), an elite indica small-grain cultivar. Using QTL analysis, 17 QTLs for five grain traits were detected on four different chromosomes. Eight of the QTLs were newly-identified in this study. In particular, qGL3-1, a newly-identified grain length QTL with the highest LOD value and largest phenotypic variation, was fine-mapped to the 17 kb region of chromosome 3. A serine/threonine protein phosphatase gene encoding a repeat domain containing two Kelch motifs was identified as the unique candidate gene corresponding to this QTL. A comparison of PA64 and CW23 sequences revealed a single nucleotide substitution (C→A) at position 1092 in exon 10, resulting in replacement of Asp (D) in PA64 with Glu (E) in CW23 for the 364th amino acid. This variation is located at the D position of the conserved sequence motif AVLDT of the Kelch repeat. Genetic analysis of a near-isogenic line (NIL) for qGL3-1 revealed that the allele qGL3-1 from CW23 has an additive or partly dominant effect, and is suitable for use in molecular marker-assisted selection.
水稻籽粒性狀遺傳基礎(chǔ)的深刻理解對(duì)于水稻品種的改良是十分重要的。本研究我們構(gòu)建了大粒粳稻品種CW23和優(yōu)良小粒秈稻品種培矮64（PA64）的F2群體。通過QTL分析，鑒定到分布在4條染色體的17個(gè)籽粒性狀QTLs，其中8個(gè)QTLs是本研究新發(fā)現(xiàn)的，尤其，一個(gè)新的粒長(zhǎng)QTL qGL3-1具有最大LOD值和最大表型變異，被定位到第3染色體17kb范圍內(nèi)。一個(gè)編碼具有兩個(gè)Kelch基序重復(fù)結(jié)構(gòu)域的蛋白磷酸酶基因是對(duì)應(yīng)于該QTL的唯一候選基因。通過比較PA64和CW23的序列，發(fā)現(xiàn)第10外顯子上1092位的單核苷酸替換（C-G）導(dǎo)致364th氨基酸由PA64的Asp(D)替換成CW23的GLU(E)。這個(gè)變異位于Kelch重復(fù)AVLDT保守基序的D位置上。對(duì)qGL3-1近等基因系（NIL）的遺傳分析表明CW23的qGL3-1具有加性或部分顯性效應(yīng)，適合通過分子標(biāo)記輔助選擇。