Liang Peixuan, Wang Hui, Zhang Qiuli, Zhou Kai, Li Miaomiao, Li Ruxiang, Xiang Siqian, Zhang Ting, Ling Yinghua, Yang Zhenglin, He Guanghua, Zhao Fangming
Rice Research Institute, Academy of Agricultural Sciences, Southwest University, Chongqing, 400715, China.
Rice (N Y). 2021 Apr 13;14(1):35. doi: 10.1186/s12284-021-00477-w.
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.
A rice line with short wide grains, CSSL-Z563, was isolated from advanced-generation backcross population (BCF) 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 F 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.
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.
染色体片段代换系（CSSLs）可用于剖析复杂性状，从中可培育出含有目标数量性状基因座（QTL）的单片段代换系（SSSLs），因此对功能分析和分子育种具有重要意义。
从‘西恢18’（受体亲本）和‘沪旱3’（供体亲本）衍生的高世代回交群体（BCF）中分离出一个粒短而宽的水稻品系CSSL-Z563。Z563携带了来自‘沪旱3’的7个片段，分布在第3、7和8号染色体上，平均代换长度为5.52 Mb。利用‘西恢18’/Z563的次级F群体鉴定出11个控制粒型的QTL。QTL qGL3-1、qGL3-2和qGL7控制Z563的粒长，具有降低粒长的加性效应；qGW3-1和qGW3-2控制Z563的粒宽，具有增加粒宽的加性效应。培育出了包含目标QTL的4个SSSLs、3个双片段代换系（D1-D3）和2个三片段代换系（T1和T2）。通过SSSLs验证了包括qGL3-2、qGL3-1和qGL7在内的8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）对粒长具有正向上位性效应，其粒长比相应的SSSLs短。QTL qGL3-2被精细定位到第3号染色体上一个696 Kb的区域，该区域包含5个在‘西恢18’和Z563之间存在差异的候选基因。这些结果对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。
Z563的短宽粒主要受qGL3-1、qGL3-2、qGL7、qGW3-1和qGW3-2控制。主效QTL qGL3-2被精细定位到第3号染色体上一个696 Kb的区域，该区域包含5个候选基因。不同QTL的聚合表现出不同的表型。本质上，基因聚合后的表现取决于聚合系中QTL的加性和上位性效应代数和与单个QTL加性效应值的比较。这些结果为qGL3-2的功能分析和新型杂交水稻品种的分子设计育种奠定了良好基础。
