Background

Grain size affects not only rice yield but is also an important element in quality of appearance. However, the mechanism for inheritance of grain size is unclear.

Results

A rice chromosome segment substitution line Z1392, which harbors three substitution segments and produces grains of increased length, was identified. The three chromosome segments were located on chromosomes 1, 5, and 6, and the average length of the substitution segment was 3.17 Mb. Cytological analysis indicates that the predominant cause of increased grain length in Z1392 could be cell expansion in the glumes. Seven quantitative trait loci (QTLs) for grain size related traits were identified using the secondary F₂ population produced by Nipponbare/Z1392. The inheritance of grain length in Z1392 was mainly controlled by two major QTLs, qGL-5 and qGL-6. qGL-6 was localized on a 1.26 Mb region on chromosome 6, and OsARF19 may be its candidate gene. Based on QTL mapping, three single-segment substitution lines (S1, S2, and S3) and two double-segment substitution lines (D1 and D2) were selected, and the mapping accuracy for qGL-5 and qGL-6 was further verified using three single-segment substitution lines. Analysis of QTL additive and epistatic effects revealed that the additive effect of alleles qGL-5 and qGL-6 from ‘Xihui 18’ was estimated to increase grain length of Z1392 by 0.22 and 0.15 mm, respectively. In addition, a positive epistatic interaction between qGL-5 and qGL-6 was detected, which indicates that the pyramiding of qGL-5 and qGL-6 for grain length produces a novel genotype with longer grains.

Conclusions

Inheritance of grain length in the triple-segment substitution line Z1392 is mainly controlled by two major QTLs, qGL-5 and qGL-6. qGL-6 was found to be located in a 1.26 Mb region on chromosome 6, and OsARF19 may be its candidate gene. A positive epistatic interaction between qGL-5 and qGL-6 results in longer grains. The present results can be used to facilitate cloning of the qGL-5 and qGL-6 genes and contribute to improvement of grain yield in rice.

中文翻译：

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具有长粒和qGL-6精细定位的水稻染色体片段替代系Z1392的粒大小QTL分析。

背景

粒度不仅影响稻米产量，而且还是外观品质的重要因素。但是，晶粒尺寸的遗传机理尚不清楚。

结果

确定了一个水稻染色体区段替代品系Z1392，其具有三个替代区段并产生了长度增加的籽粒。这三个染色体片段位于1、5和6号染色体上，取代片段的平均长度为3.17 Mb。细胞学分析表明，Z1392中晶粒长度增加的主要原因可能是颖片中的细胞膨胀。使用Nipponbare / Z1392产生的次生F ₂种群，确定了七个与晶粒大小相关性状的数量性状位点（QTL）。Z1392中籽粒长度的遗传主要受两个主要QTL（qGL-5和qGL-6）控制。qGL-6位于6号染色体上的1.26 Mb区域，OsARF19可能是其候选基因。基于QTL映射，选择了3条单段替换线（S1，S2和S3）和2条双段替换线（D1和D2），并使用进一步验证了qGL-5和qGL-6的映射精度三个单段替换行。对QTL加性和上位性效应的分析表明，来自“喜回18”等位基因qGL-5和qGL-6的加性效应估计分别使Z1392的粒长增加了0.22和0.15 mm。此外，检测到qGL-5和qGL-6之间存在积极的上位相互作用，这表明qGL-5和粒长的qGL-6产生了一种具有更长晶粒的新基因型。

结论

三段替代线Z1392中晶粒长度的遗传主要受两个主要QTL（qGL-5和qGL-6）控制。发现qGL-6位于6号染色体上的1.26 Mb区域，OsARF19可能是其候选基因。qGL-5和qGL-6之间的阳性上位性相互作用导致更长的晶粒。本结果可用于促进qGL-5和qGL-6基因的克隆并有助于提高水稻的籽粒产量。