Genetic Diversity Evaluation, Association Analysis Of Phenotypic Traits And Molecular Id Construction In Maize

Analyzing the genetic diversity of maize inbred lines and classifying the heterotic group and the model of heterosis which using to select the parents and improve, innovate, excavate and employ the good germplasm cloud improve the efficiency of selecting the parents of hybrid and shorting the duration of breeding, which was the important basis of maize breeding.QTL location of important maize traits is the basis of marker-assisted selection, which has a very important significance to improve the accuracy and foresight of breeding. The materials of this study were part of important inbred lines in our country, varieties which popularizing in large areas and inbred lines selected by ourselves. Genetic distance obtain by SSR markers were used to classify the heterotic group of good maize germplasm and analyze and discuss the model of heterosis, Association analysis was an approach to identify the relationship of molecular markers or candidate genes with traits in a given population based on linkage disequilibrium (LD). In this study, 64 pair SSR markers were used for genotyping of 257 maize inbred lines. LD of pairwise loci and population structure were analyzed, then association analysis between SSR and nine phenotypic traits such as plant height, ear height, growth duration, ear length, row number of ear, 100-seeds weight, oil content, protein content, and starch content were performed using TASSEL GLM and their explained phenotypic variation were detected, too. Molecule ID could be build up by the germplasm character analysis software (ID Analysis1.0) which developed by ourselves, and classify the materials by least primers.The results of this study follow as:(1) At present, the purpose of maize inbred lines breeding with high yield should focus on prolonging the growth duration and increasing the ear length and 100-seed weight, according with other triait. Breeding of maize inbred lines with high quality should directional select the germplasms with ear diameter and plant height, next with growth duration, row number per ear and ear diameter, according with other traits to correspond the relational factors and pick up the process of breeding.(2) The materials in this study could be classified into six groups of PA, BSSS, Lvdahonggu, Tangsipingtou, Lancaster and PB. The result of clustering analysis was according with pedigree. In this study, Lancaster can be classified into group A, Tangsipingtou and Lvdahonggu in group B, PA and PB in group C (PN), and BSSS in the group D because of different from other groups. The materials in this research could be classified into 4 groups (6 subgroups). Since the genetic base of maize germplasms was narrow in our country, simplifying the number of groups could beneficial to explore the model of heterosis. Core SSR markers could classify the heterotic group.(3) In the 64 SSR loci, there are 43 markers associated with 24 traits, in which 19 loci associated with 14 phenotypic traits at the level of 0.01 and other markers at the level of 0.05. There are 80 markers associated with agronomic traits and quality traits, in which only seven associated with quality traits, which highly less than that associated with agronomic traits. The number of SSR loci found by associating analysis were more than the number which fixed by population with the same size, the markers associated with one traits were focus in the linkage group, such as most of the markers associated with growth duration were in the linkage group 7, which may to do with there more markers in this linkage group. It is ubiquity that one marker associated with more than one trait which in one category, such as umc1741 associated with plant height, ear height and ear length; umc2160 and umc1545 in linkage group 7 associated with not only growth duration but also, which indicating that there are inner genetic factor associated with phenotypic traits of maize. The results indicated that: the markers which associated with plant height, ear height, ear length and row number per ear were more than that with oil and protein content. More materials with variation in quality should add to the research group. There are several markers associated with one or several agronomy traits in one chromosome and different markers associated with one trait in different chromosomes, most markers were according with the mapping of QTL.(4) Resource characteristic analysis of 257 maize inbred lines by SSR indicated that: only ten pair of primers can differentiate the varieties in this study. The inbred lines could be identified quickly and exactly by amplificating one variety with ten primers and examining by electrophoresis, which acquiring the photographs of molecule ID.