Genome-wide Association Analysis Of Yield Related Traits In Alfalfa

Alfalfa(Medicago L.)enjoys the reputation of"King of Forage"with a high yield of grass and good nutritional value.It is a source of high quality protein feed.The yield traits of alfalfa are controlled by multiple genes.GWAS analysis is an effective method for quantitative traits.In this study,13 main yield-related traits of alfalfa were determined using population of alfalfa cultivars,and 53028 SNP markers were used for genome-wide association analysis.The main results are as follows:1.Analysis of yield-related charactersPhenotypic analysis of 13 yield-related traits of 119 alfalfa with a coefficient of variation ranged from 10.57%(E1,PH)-45.09%(E3,SDW)and the genetic diversity index ranged from 1.80%(E3,SDW)-2.10%(E1,NMSB).The correlation of 13 traits showed that both fresh grass yield and hay yield were significant positively correlated with plant height and number of rhizome branches.The number of leaves was significant positively correlated with the number of branches,stem diameter,stem dry weight,leaf dry weight and stem-leaf ratio of the main stem.2.Analysis of genetic diversity of AlfalfaUsing 234 SNP markers with uniform distribution,119 alfalfa varieties were divided into2 subgroups by Structure software.A phylogenetic tree was constructed using 53028 SNP markers.119 alfalfa varieties were divided into three groups.13 yield-related traits were used for cluster analysis and 119 materials were divided into three groups.3.GWAS analysis53028 SNP markers were used to correlate 13 yield-related traits of alfalfa.A total of1268 SNP markers were detected at the P?0.0001 level.The explanatory phenotypic variation(R~2)ranged from 15.11 to 88.80%.The highest value of R~2 was SNP146564-c1-g3-i1(SDW-E3),and the lowest was SNP139985-c0-g4-i1(LW-E3).Among them,15 SNP markers were detected for plant height,134 for main stem branches,11 for rhizome branches,81 for fresh grass yield,38 for hay yield and 28 for leaves.185 stable association markers were detected,R~2 ranged from 15.11 to 70.71%.Among them,19 stable association markers were detected for the number of main stem branches,1 for the number of rhizome branches,1stable association site for fresh grass yield,2 for hay yield and 1 for the number of leaves.32multi-potent SNPs were detected,with R~2ranging from 17.68 to 65.66%with an average of30.95%.SNP143687-c15-g19-i2 was significantly correlated with 5 traits(NMSB,DFR,FY,LL,LW),9 multi-potency SNPs were significantly correlated with 4 traits and 21multi-potency SNPs were significantly correlated with 3 traits.