Comparative Study Of Quantitative Trait Loci For Major Traits Between Rice And Maize

With the development of molecular marker technology, researchers have gotten a lot of QTL information for different crops and different traits using a variety of statistical methods. The advanced technology of computers and web database made possible to rapidly exchange results between different researchers. Now, most of QTL mapping results have been published on the Internet for free searching. We next step need to find methods, which can guide us to organize and synthesize this rapid increasing research information, and help us to understand the QTLs controlling the quantitative traits and their distribution pattern between the relative species and to improve the accurate and precision of QTL mapping.Almost all the published QTL mapping information of 15 common traits of rice and maize, such as plant height, were collected and arranged in this study, which was integrated into its common genetic map according to the flanking markers of QTL and QTL genetic position. Comparative research was implemented at the genome QTL level between rice and maize, among which the QTL underlying traits of plant height and panicle number (ear number) were compared on the basis of the information of QTL flanking markers, while all the 15 traits were studied based on the QTL genetic position.In the flanking markers-based comparative analysis of QTL, the QTL identified from each species were first integrated into the public genetic maps based on the flanking markers. The relationship between the QTL from two species underlying the same trait was then identified using marker information from the public genetic maps. The results indicate that:(1) In the regions of chromosome where markers of rice and maize have significant collinearity, QTL of the same traits also showed obvious collinearity. The homologous QTL can be more easily found when the trait with higher heritability, such as plant height. This result suggests that the genes controlling the plant height of rice and maize may come from the same origin. Therefore the genomic information from the rice with smaller genome can be used in the fine mapping and cloning of the genes controlling some important traits from maize with bigger genome.(2) Usually QTL that control plant height and panicle number (ear number) are condensed in some particular homologous regions, which is consistent with the results from the genome sequencing of rice and maize. It means that the positions of genes on chromosome are not randomly assigned, but focus on some regions that could be gene-rich region or reserved region in the process of evolution.In the genetic position-based comparative analysis, the ratios of genetic length of chromosomes between QTL mapping and public genetic mapping were first calculated. Then the confidence interval of QTL was zoomed and the QTL were integrated into the public genetic maps. The results indicate that:(1) The QTL mapping frequencies on different chromosome regions were different from traits. It's found that there were several hot spot regions. The region with high frequency might mean high expression of specific traits under various genetic background and environmental conditions. In these regions, there is higher probability to detect the high-heritability QTL.(2) QTL hot spot regions often overlap for different traits. It may be result from genes underlying different traits are condensed on the chromosome and close linked to form a gene cluster. It also can be the result of pleiotropy, that is, one gene influence several traits. These active regions controlling different traits are vital to the crop genetic improvement.