The secondary mapping populations (SMPs), which were used to map quantitative trait loci (QTLs), include near-isogenic lines, introgression lines, chromosome segment substitution lines et al.
用于作物数量性状基因座（QTL）定位研究的次级作图群体有近等基因系、导入系、染色体片段代换系等。
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Single segment substitution lines (SSSL) containing only one segment of donor chromosome introgressed into a recipient genetic background permits QTLs to be mapped with greater precision.