标记辅助选择育种中QTL基因型的多点联合推断

传统的育种方法对数量性状的选择存在很大难度,现代分子标记技术为实现控制数量性状基因的准确选择提供了有效的技术手段。目前分子标记辅助选择实践仅是对标记基因型的选择,而非直接对QTL基因型进行选择。尽管标记基因型容易获得,但标记基因型通常并非QTL基因型,除非有关的QTL恰巧在标记座位。因此,如何鉴别QTL的基因型成为分子标记辅助选择的关键。QTL基因型通常需要通过分子标记基因型进行推断,由于标记信息的不完全或缺失,使得对个体QTL基因型的鉴别会发生困难。本文在四向杂交设计的基础上,结合贝叶斯理论和马尔可夫链原理,提出一种通用的QTL基因型多点联合推断方法,该方法能够很方便地处理显性标记和缺失标记,同时结合标记信息和表型数据联合推断QTL基因型的条件概率。模拟研究发现,表型数据选择的效果较差,其选择的个体QTL基因型基本上都是错误的,而应用本文所论述的方法,将表型数据与标记数据相结合选择,对QTL基因型的判断正确,且推断的把握性很高。

Multi-point Joint Inference of QTL Genotype in Marker-assisted Selection

The improvement of the quantitative traits is very difficult through the traditional breeding methods. Modern marker technologies provide powerful methods to identify the genes controlling the quantitative traits. In marker-assisted selection (MAS) breeding, most researches are to select the marker's genotype, rather than the QTL genotype. The marker's genotype is observed readily, however it is not the QTL genotype usually, excepting QTL and marker are in the same location. So, the identification of QTL genotypes of candidate individuals is the basis of marker-assisted selection (MAS) breeding. QTL genotype is usually inferred by the genotypes of DNA molecular markers. However, it would be difficult to identify the QTL genotypes when some marker genotypes are missing or incomplete. In this paper, based on hidden Markov chain model and Bayes' theorem, a multi-point method was proposed to identify QTL genotypes in four-way crosses design. The proposed algorithm can deal with dominant and missing markers, and joint the phenotypic value and marker genotype to infer the conditional probability. Simulation studies show that selection according the phenotype value is weak, and can not choose the individuals with interested QTL, however jointing inference method is expected to be more accurate than the commonly used method in detecting QTL genotype.