Maize Genetic Diversity And Genome-wide Association Analysis Of Flowering Time In Northeast China

Maize germplasm resources are the basis of breeding maize varieties.In addition to revea l the genetic characteristics of themselves and provide information and reference for subseque nt germplasm improvement,innovation and breeders’selection,the analysis of genetic diversit y and population structure of maize germplasm resources are also the basis of research work s uch as association analysis and exploring excellent alleles.With the development of molecular biology,SNP markers have been widely used in genetic diversity analysis.And they can clear ly divide the population structure and analyze the genetic diversity.Due to the fact that China is not the origin land of maize and maize breeding was carried out late,the germplasm resourc es of Maize in China are relatively narrow.Nevertheless,the maize lineage in China is more c haotic because of the continuous introduction of foreign hybrids for breeding.Northeast areas,as one of the main maize producing places in China,also faces the situation of narrow germpl asm resources and chaotic gene-relationship.Therefore,only by clearly dividing the inbred lin es with unknown genetic relationship into known groups,can it be conducive to the developm ent and utilization of germplasm resources.Accordingly,this study used 378 inbred lines of northeast core associated population,two different SNP markers,DArT and reduced GBS markers,to analyze the genetic diversity and divide the population structure of the associated population,clarify their gene-relationship and lay a foundation for Genome-Wide Association Study.Meanwhile,the study used DArT and GBS population structure matrix to analyze the genome-wide association of flowering time,w hich is an important adaptive trait in the process of maize domestication,to find the relevant c andidate genes,and evaluate the performance of the two markers in different analysis.And fin ally,the study combined genetic diversity analysis with Genome-Wide Association Study of fl owering time,and provided theoretical guidance for breeding work.The main results are as fo llows:(1)The genetic diversity of core associated populations in Northeast China is rich.The polymorphism information content of SNP marked by DArT ranged from 0.0754 to0.375,and the variation range of gene-diversity was 0.0784 to 0.51.The SNP polymorphism i nformation content of GBS markers ranged from 0.0778 to 0.5899,and the gene diversity rang ed from 0.0811 to 0.664.Both DArT and GBS markers showed that the genetic relationship co efficient of most inbred lines(65%,66%)was less than or equal to 0,which showed that most of the 378 inbred lines were non genetic or distant,indicating that the maize population had ri ch genetic diversity.It was determined that when the marker of GBS was LD r~2=0.1,filtering was more suitable for genetic diversity analysis,and the population was divided into four sub groups:Reid,Lancaster,Iodent and MIX.Using DArT markers for genetic diversity analysis,378 inbred lines can be divided into 7 subgroups,namely LRC,Iodent,Lancaster,domestic R eid,Reid group,SPT subgroup and MIX group.According to the genetic relationship,Iodent×LRC,Reid×LRC,SPT×Reid three hybrid modes were proposed.(2)Population structure division of core maize inbred lines in Liaoning ProvinceBased on the evolutionary tree analysis maize of Liaoning Academy of Agricultural Scien ces,Shenyang academy of Agricultural Sciences and Dandong Academy of Agricultural Scien ces,it can be divided into seven subgroups:LRC,SPT,Reid,domestic Reid,MIX,Lancaster a nd P group.Further analysis of three series of inbred lines showed that the series of inbred line s of Liaoning Academy of Agricultural Sciences and Shenyang Academy of Agricultural Scien ces can be divided into 5 subgroups,namely,LRC,SPT,Reid,domestic Reid and P group.Da ndong Academy of Agricultural Sciences Series can be divided into SPT,LRC and Reid group s.(3)Genome-Wide Association Study on flowering time of MaizeThe Genome-Wide Association Study was carried out on the flowering time of the North east core Association population,which is composed of 378 maize inbred lines,by using DArT markers and GBS markers.A total of 57 genes or their Arabidopsis/rice homologous genes have been annotated by DArT markers.According to the annotation,4 genes related to floweri ng time were identified.And a total of 34 genes of maize or their Arabidopsis/rice homologo us genes have been annotation by GBS markers.According to the annotation,14 candidate ge nes related to flowering time have been identified,including 3 previously reported genes Zm00001d042463,Zm00001d042472 and Zm00001d017350.Among them,Zm00001d042463 gen e affects flowering by regulating plant hormones.Zm00001d042472 and Zm00001d017350 re gulate a transcriptional factor TCP21,which plays a key role in the early process of pollen gro wth,and then affects the flowering time.(4)The SNP markers obtained from two different sequencing platforms have different adv antages in applicationCombined with the results of genetic diversity analysis and Genome-Wide Association St udy of 378 maize inbred lines in Northeast core associated population,DArT marker is more s uitable for genetic diversity analysis and population structure division,but also revealing the b lood relationship between inbred lines,while GBS marker is more suitable for Genome-Wide Association Study on associated populations and to find genes related to phenotypic traits,so as to provide theoretical guidance for breeding works.