通过回交程序结合分子标记辅助选择构建了一套以优良籼稻恢复系9311为背景、导入片段来源于粳稻日本晴的代换系群体。该套群体由125个代换系组成，每系含有单一或少量导入染色体片段，导入片段间相互重叠或衔接能覆盖粳稻全基因组。代换系的平均背景回复率为98.4%，导入片段平均长度为20.9 cM，纯合和杂合导入片段分别占水稻基因组的1.4%和0.2%。利用该群体，两年共检测到31个QTL影响水稻穗重、穗长、结实率和秃顶等性状；导入片段QTL对穗重和结实率均起减效作用。该套重叠片段代换系将为重要性状的基因定位、功能鉴定以及籼粳杂交育种研究提供极有价值的遗传材料。
Introgression lines in crops have been proposed as an attractive and powerful way to identify quantitative trait loci (QTLs) affecting importance traits. Here we report construction of a set of contiguous segment substitution lines (CSSLs) in rice through repeated backcrossing and molecular marker-assisted selection (MAS). These CSSLs were derived from a cross between the sequenced japonica cv. Nipponbare as donor and indica cv. 9311 as recurrent parent, which is also known as an elite restorer line of super-hybrid rice in China. The advanced backcross generations (BC3 and BC4) were subjected to three rounds of MAS to select lines with single or few japonica introgression chromosomal segments. One hundred and twenty-five polymorphic SSR markers evenly distributed on rice genome were used in the MAS scheme. A set of 125 CSSLs was determined by graphical genotypes, each of lines contained a single or few chromosomal introgression segments with the indica background, all the overlapped segments covered the whole genome of japonica. The genome proportion of the recurrent parent in each of the CSSLs ranged from 93.8% to 99.9%, with an average of 98.4%. The average proportions of homozygous and heterozygous donor segments were 1.4% and 0.2%, respectively. The average length of introgression segments was 20.9 cM, ranging form 2.9 to 63.9 cM. In order to illustrate a potential application and validate these CSSLs, the phenotypic effects of the japonica introgressions on the panicle-related traits (panicle weight, panicle length, seed setting rate and degenerated spikelet of top panicle) were analyzed. Thirty-one QTLs were detected for the four panicle-related traits in two year (site) trials. The all japonica alleles at those QTLs for panicle weight and seed setting had negative effects. The set of CSSLs will provide a useful genetic stock for functional identification of genes conferring phenotypic variations between subspecies and for the subspecies breeding.
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