Background

Chromosome segment substitution lines (CSSLs) can be used to dissect complex traits, from which single-segment substitution lines (SSSLs) containing a target quantitative trait loci (QTL) can be developed, and they are thus important for functional analysis and molecular breeding.

Results

A rice line with short wide grains, CSSL-Z563, was isolated from advanced-generation backcross population (BC₃F₆) derived from ‘Xihui 18’ (the recipient parent) and ‘Huhan 3’ (the donor parent). Z563 carried seven segments from ‘Huhan 3’, distributed on chromosomes 3, 7, and 8, with average substitution length of 5.52 Mb. Eleven QTLs for grain size were identified using secondary F₂ population of ‘Xihui 18’/Z563. The QTLs qGL3–1, qGL3–2, and qGL7 control grain length in Z563 and have additive effects to reduce grain length; qGW3–1 and qGW3–2 control grain width in Z563 and have additive effects to increase grain width. Four SSSLs, three double-segment substitution lines (D1–D3), and two triple-segment substitution lines (T1 and T2) were developed containing the target QTLs. The genetic stability of eight QTLs, including qGL3–2, qGL3–1, and qGL7, was verified by the SSSLs. D1 (containing qGL3–2 and qGL3–1), D2 (qGL3–1 and qGL7), and T1 (qGL3–2, qGL3–1, and qGL7) had positive epistatic effects on grain length, and their grain length was shorter than that of the corresponding SSSLs. The QTL qGL3–2 was fine-mapped to a 696 Kb region of chromosome 3 containing five candidate genes that differed between ‘Xihui 18’ and Z563. These results are important for functional research on qGL3–2 and molecular breeding of hybrid rice cultivars.

Conclusions

The short and wide grain of Z563 was mainly controlled by qGL3–1, qGL3–2, qGL7, qGW3–1 and qGW3–2. The major QTL qGL3–2 was fine-mapped to a 696 Kb region of chromosome 3 containing five candidate genes. Different QTLs pyramiding displayed various phenotypes. In essence, the performance after pyramiding of genes depended on the comparison between the algebraic sum of the additive and epistatic effects of QTLs in the pyramidal line and the additive effect value of the single QTL. The results lay good foundation in the functional analysis of qGL3–2 and molecular design breeding of novel hybrid rice cultivars.

中文翻译：

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基于短粒CSSL-Z563和qGL3–2精细映射的水稻粒QTL的鉴定和金字塔化

背景

染色体片段替代品系（CSSLs）可用于解析复杂性状，从中可以开发出包含目标定量性状基因座（QTL）的单片段替代品系（SSSLs），因此它们对于功能分析和分子育种非常重要。

结果

从“ Xihui 18”（受体亲本）和“ Huhan 3”（施主亲本）衍生的先进回交群体（BC ₃ F ₆）中分离出了短粗粒水稻品系CSSL-Z563 。Z563携带来自“ Huhan 3”的七个片段，分布在3、7和8号染色体上，平均取代长度为5.52 Mb。使用'Xihui 18'/ Z563的次生F ₂群体鉴定了11个籽粒大小的QTL 。QTL qGL3-1，qGL3-2和qGL7控制Z563中的晶粒长度，并具有减少晶粒长度的累加作用。qGW3-1和qGW3-2控制Z563中的晶粒宽度，并具有增加晶粒宽度的累加效果。开发了四个包含目标QTL的SSSL，三个双段替换线（D1-D3）和两个三段替换线（T1和T2）。SSSLs验证了包括qGL3–2，qGL3–1和qGL7在内的八个QTL的遗传稳定性。D1（包含qGL3–2和qGL3–1），D2（qGL3–1和qGL7）和T1（qGL3–2，qGL3–1和qGL7）对晶粒长度具有积极的上位性影响，并且它们的晶粒长度短于相应的SSSL的密码。QTL qGL3–2将其精细映射到3号染色体的696 Kb区域，该区域包含5个在“ Xihui 18”和“ Z563”之间不同的候选基因。这些结果对于qGL3–2的功能研究和杂交水稻品种的分子育种具有重要意义。

结论

Z563的短而宽的晶粒主要受qGL3-1，qGL3-2，qGL7，qGW3-1和qGW3-2的控制。主要的QTL qGL3–2被精细映射到3号染色体的696 Kb区域，其中包含5个候选基因。不同的QTL金字塔显示了不同的表型。本质上，基因金字塔化后的性能取决于金字塔线中QTL的加性和上位效应的代数和与单个QTL的加性效应值之间的比较。该结果为qGL3–2的功能分析和杂交水稻新品种的分子设计育种奠定了良好的基础。