Abstract: It’s well-known that incorporating some existing populations derived from multiple parents may improve QTL mapping and QTL-based breeding programs. However, no general maximum likelihood method has been available for this strategy. Based on the QTL mapping in multiple related populations derived from two parents, an maximum likelihood estimation method that can incorporate several populations derived from three or more parents and can be used to handle different mating designs was proposed. Taking the circle design as an example, simulation studies were performed to study the impact of QTL heritability and sample size upon the proposed method. The results showed that under the same heritability, higher QTL detection power and more exact and accurate estimation of parameters could be obtained when three F2 populations were analyzed jointly than when only any two F2 populations were analyzed simultaneously; and higher heritability, especially with larger sample sizes would increase the ability of QTL detection and improve the estimation of parameters. Potential advantages of the method are as follows: firstly, the existing results of QTL mapping in single population can be compared and integrated with each other using this proposed method, so the ability of QTL detection and precision of QTL mapping can be improved. Secondly, owing to multiple alleles in multiple parents, the method can exploit gene resource more adequately, which will lay an important genetic groundwork for plant improvement.

Key words: related population, quantitative trait locus, gene mapping, maximum likelihood estimation

摘要： 对多亲本杂交衍生的多个群体的联合分析将有助于QTL的定位和基于QTL分析的育种实践，但目前还没有一个可对这类群体进行联合分析的通用方法。在以往发展的双亲杂交衍生的多个相关群体QTL图谱的联合构建方法的基础上，进一步拓展为可以对多个亲本杂交衍生的多个相关群体进行联合分析。首先建立了多亲本杂交衍生的多个相关群体QTL联合作图的通用遗传模型，然后根据混合分布理论建立基于EM(expectation maximization)算法实现的QTL作图的极大似然估计方法。以循环杂交设计的3个F2群体为例用计算机模拟数据研究了QTL遗传力和样本容量2个因素对方法的影响。结果表明，无论是统计功效，还是参数估计的准确度和精确度，相同遗传力下，对循环杂交设计的3个F2群体联合作图均优于对其中的任2个F2群体联合作图。该方法的主要优点：一是可以比较和综合已有的对单个作图群体的定位结果，提高QTL检测的功效和定位的精度；二是在多亲本涉及的等位基因数更多的情形下，可以扩大和发掘有关数量性状的基因资源，从而为育种学家改良相应的数量性状奠定重要基础。

关键词: 相关群体, 数量性状座位, 基因定位, 极大似然估计方法