| As an important agronomic trait of forages,flowering time has a significant impact on the yield,quality and utilization of forages.Controlled by the minor polygenes,flowering time has complex networks.The research on forage flowering genes and the molecular mechanism of forage flowering regulation is very helpful for the mining of forage flowering genes.Therefore,the new breeds of forage with different maturity can be produced.They can meet the production demands of people.Elymus sibiricus,a model grass species,belongs to Elymus in Poaceae,which has the features of perennial,sparse type,mesophyte and xerophyte.It has many advantages including drought and cold resistance,salt and alkali tolerance,high yield,good palatability and forage quality,etc.In the researches on model plants such as Arabidopsis thaliana,rice(Oryza sativa)and wheat(Triticum aestivum),flowering genes have been deeply studied and finally got some achievements.While E.sibiricus and crops are distantly related.It is a heterotetraploid species with the self-compatibility.Due to its chromosomal composition of StStHH(2n = 4x = 28),the hereditary basis of E.sibiricus is relatively complex.Thus it is difficult to obtain the target genes by using the method of homologous cloning.Based on the evaluation of flowering time of E.sibiricus and the observation and analysis of its reproductive traits,the present paper aimed at sequencing of samples at different flowering times of E.sibiricus early and late flowering materials to a great depth by using the sequencing technology of high-throughput transcriptome and then explored its gene expression profile.Furthermore,by utilizing the genotype data with the high densify SNP molecular markers,the genome-wide association analysis on the flowering of E.sibiricus had been conducted in this paper.The main results of the present paper are as follows:1.With 66 selected materials of E.sibiricus germplasms,this study firstly focused on the evaluation of its flowering time and the correlation analysis on its five reproductive traits containing the reproductive branches per plant,spikelet number of rachis,floret number per spikelet,100-seed weight and breaking tensile strength.The results indicated that the flowering time among the different E.sibiricus germplasms was various.For instance,the interval between the earliest and the latest flowering materials were 52 days.Besides,the reproductive traits were different to varying degrees,among which the coefficient of variation of the number of reproductive branch per plant was highest,up to 68.97%.Moreover,the further analysis showed that flowering time was inversely associated with three variables including the number of reproductive branch per plant,spikelet number of rachis,floret number per spikelet.2.Three early flowering genotype and three late flowering genotype were selected,and 18 samples were taken at the booting,heading and flowering stages.After the transcriptome sequence analysis on the tissue samples of E.sibiricus,we had obtained 400,453,230 clean reads and 184,735 Unigenes.166,071 of Unigenes were accompanied with annotation information,from which there were 3,526 differential expressed genes being selected.Afterwards,we further studied the co-expression of genes by using the weighted analysis method.Finally,5 co-expression modules were identified and 7 hub genes were selected.These genes were LIMYB,PEX19,GWD3,BOR7,PMEI28,LRR,AIRP2.3.In this study,155 individual plants of E.sibiricus were used for genome-wide association analysis.Based on genotype data with the high density SNP molecular markers,and phenotypic data of two-year observation,the present study made the association analysis on three flowering related agronomic traits.With mixed linear model,9 SNPs,significantly correlated to the flowering were finally detected,and screened out 3 specific genes.They were FAR1,GLPs,CPSF30. |
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