利用多个亲本进行交配设计、开展遗传研究的重要性日益突出。与双亲衍生群体相比，多亲群体具有更丰富的遗传变异，能挖掘出具有更高育种价值的基因。然而，多亲群体的遗传分析方法研究还很少。本项目在前期克隆F1和四交群体的研究基础上，拟开展四向和八向杂交衍生纯系群体的遗传分析方法和分析软件研究，具体内容包括（1）推导两个连锁座位的理论基因型频率，研究重组率估计方法和高密度连锁图谱构建算法；（2）利用已构建图谱，推导区间标记基因型下QTL基因型的期望频率，建立表型与基因型间的线性关系模型，提出该类群体定位QTL的有效方法；（3）研制遗传分析软件，利用大量模拟群体验证遗传分析方法的有效性，并将这些方法应用于二至三个真实的多亲纯系群体。本项目研究结果将为四交和八交衍生纯系群体的遗传分析提供有效方法和工具，为其他多亲交配设计的遗传分析方法提供借鉴，促进多亲本群体创建、基因挖掘和育种利用等多方面的研究工作。

Genetic studies on populations derived from multiple parents have become more and more important. Compared with bi-parental populations, multi-parental populations contain more abundant genetic variation, and can be used to detect QTL with higher breeding values. However, genetic analysis methods for multi-parental populations are particularly lacking. Based on our previous studies on clonal F1 and four-way crosses, this project will focus on genetic analysis methods and software development for populations of pure lines derived from four-way and eight-way crosses. Our objectives are (1) to derive the theoretical genotypic frequencies between two linked loci, and then propose algorithms for estimating pairwise recombination frequencies and constructing high density linkage maps; (2) to derive the expected frequencies of QTL genotypes conditional on each marker class, build the linear model of phenotype on marker type, and then develop the efficient method for QTL detection; (3) to develop the software for genetic analysis, validate the proposed methods using simulated populations, and finally apply these methods to two or three actual multi-parental pure line populations. Outcomes from this project will contribute useful methods and tools for genetic analysis in pure line populations derived from four-way and eight-way crosses. In addition, methodology used in this project will also provide guidance for populations derived from other multi-parental mating designs, which will contribute to population development, gene discovery and future breeding application using multiple parents.