以国内、外12个水稻品种（包括8个籼稻品种和4个粳稻品种）为供体亲本，利用回交和微卫星标记辅助选择相结合的方法构建了一个以籼稻品种“华粳籼74”为遗传背景的单片段代换系（SSSL）群体。该群体由260个不同的SSSL组成，其代换片段分布在水稻的12条染色体上，长度分布于0.2～109.9 cM，平均长度为19.9 cM；代换片段的总长度为5 166.0 cM，相当于水稻基因组总长度的3.4倍，代换片段在水稻基因组上的覆盖率为83.8%。这些SSSL的代换片段包含了水稻基因组丰富的等位基因变异，将在基因（QTL）的定位、克隆、功能分析及水稻分子育种中具有重要的利用价值。
Single segment substitution line (SSSL) is a power tool for mapping, cloning and functional analysis of genes. In this study, A SSSL population was developed using a Indica cultivar “Huajingxian 74” as recipient and 12 accessions including 8 Indica and 4 Japonica as donors (Table 1 and Fig.1). Five hundreds and forty-nine SSR markers with an average marker interval about 2.8 cM on the rice microsatellite map were used to survey the polymorphism between parents. The polymorphisms between the 12 donors and the recipient were varied from 33.0% to 70.7% with an average of 50.0% (Table 2). By backcrossing four or five times, a series of candidate SSSLs were selected. The genetic backgroud in the candidate SSSLs was examined in BC4F1, BC4F2, BC5F1 or BC5F2. The samples with residual segments from the candidate SSSLs were 1.07% (Table 3). Discarding the candidate SSSLs with residual segments, a total of 260 SSSLs were developed, of which 74 SSSLs were selected from BC4F2, 134 SSSLs from BC4F3 and other 52 from BC5F2 (Table 4). Each SSSL contained a single defined homozygous chromosome substituted segment from one of the twelve donors in the Huajingxian 74 genetic background. The estimated lengths of the substituted segments ranged from 0.2 cM to 109.9 cM with an average of 19.9 cM (Fig.2 and Table 4). Total length of the substituted segments in the SSSL population was 5166.0 cM, which was about 3.4 times of the rice genome. The substituted segments in the SSSLs were distributed on 12 chromosomes (Fig.3 and Table 5) and provided a coverage of 83.8% of the rice genome (Table 4). These SSSLs will play an important role in the study of functional genomics and molecular breeding in rice.
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