Studies On The Relationship Between Diallel Analysis And QTL Mapping

Diallel analysis has been broadly used as an important tool of genetic analysis in classical quantitative genetics, which advanced the development of genetics studies and breeding practices. Being a hotspot in genetic studies, QTL mapping is a powerful tool in molecular quantitative genetics, which is an inter-discipline between quantitative genetics and molecular genetics. Both tools serve as the key methods of genetic analysis for investigating the genetic natures of quantitative traits, and play important roles in the studies of quantitative genetics. Therefore, there were many similarities between the two methods. In diallel analysis, those genes controlling a quantitative trait were analyzed as a whole. However, those genes controlling a quantitative trait could be dissected into single genes and be studied individually using the method of QTL mapping. Therefore, there also were many differences between the two methods. What's the relationship between diallel analysis and QTL mapping? Could more interesting informations be provided if diallel analysis and QTL mapping were jointly applied to analyzing the same set of data. This was an interesting problem. Up to now, no reports on this was seen.The present studies were conducted to investigate the relationship between diallel analysis and QTL mapping. Monte Carlo simulations were employed for this purpose. Both tools were used to analyze a real set of data including quantitative trait and molecular marker information of an immortalized F2 (IF2) population of rice, which was constructed by random mating among RIL hues derived from Zhenshan97B x Minghui63. The dissertation consists of two sections: simulation studies and a worked example.In the section of simulation studies, Monte Carlo simulations were conducted to study the relationship between diallel analysis and QTL mapping. The section was mainly involved in studying the factors influencing the relationship between diallel analysis and QTL mapping. The correlation coefficient was introduced into present studies for measuring the relationship between diallel analysis and QTL mapping. The main contents and conclusions of the simulation studies are as follows:(1) Diallel analysis and QTL mapping adopted different definations of genetic effect respectively. This had an influence on the correlation between diallel analysis and QTL mapping. When genetic variance or genetic effect was equal, the ranking of the correlation from large to small was additive, dominance and additive by additive in turn.(2) When genetic variance increased relative to total variance, its correlation between diallel analysis and QTL mapping also obviously aggrandized; But when the genetic effect increased to certain level, the speed of aggrandizement of its correlation changed more and more slow, and the correlation curse entered into a platform stage finally.(3) The correlation of each genetic effect was influenced by other genetic effects. Among the genetic components, residual variance had the most remarkable influence on the correlation between diallel analysis and QTL mapping.(4) The linkage of QTLs and number of QTLs showed no effects on the correlationbetween diallel analysis and QTL mapping when genetic variances were not changed.(5) The sample proportion of DH to IF2 was bigger; the correlation between diallel analysis and QTL mapping was lower.(6) In the results of QTL mapping, either biased effects or biased positions were capable of affecting the correlation between diallel analysis and QTL mapping. The bias was larger, the correlation was lower.(7) Selecting different thresholds in QTL mapping had certain influence to the correlation between diallel analysis and QTL mapping.(8) The different of polygenic system was the main factor influencing the correlation between diallel analysis and QTL mapping. Because of the existence of polygenes, the correlation between diallel analysis and QTL mapping was lower. The variance proportion of polygenes to major genes was larger, the correlation was lower. On the contrary, according to...