Construction Of Genetic Linkage Map And QTL Mapping For Florescence And Leaf Type Of Alfalfa

Object: To detect the flowering time and leaf-related traits QTL loci of alfalfa by genetic map,and to clarify the genetic law of flowering and leaf traits of alfalfa and to provide theoretical basis for alfalfa breeding with high quality.Methods: The F1 hybrid population of alfalfa were obtained by the male parent with high-yield,late-maturing and the male parent with low-yield,early-maturing.Then the flowering time and leaf shape of the parent and 152 single plants of F1 generation were measured.The major gene and ploy genes inheritance model analysis of flowering time and leaf traits of parents and their offspring were carried out,and a high-density genetic map was constructed,and the QTL mapping was analyzed.Results:(1)The quantitative analysis of the flowering time data of the offspring of alfalfa was carried out by using the quantitative trait Major gene and ploy genes inheritance model analysis method for three years.Then 2MG-ADI was selected as the most optimal genetic model for flowering time.The major gene heritability of 2016,2017 and 2018 were99.89%,62.29%,97.84%,respectively.Moreover,2MG-ADI was the most optimal genetic model for leaf traits based on genetic analysis from 2016 to 2018.The major gene heritability of leaf length,leaf width,leaf area were 92.06%,95.07%,49.48%,respectively.(2)The genetic map of flowering time was performed by the Joinmap software,and 915 paternal markers and 2982 parental markers were selected.The genetic map distance of male parent is 2670.8 cm,the average map distance between markers is 2.92 cm,and the linkage group length ranges from 36.5 to 166.3 cm.The genetic map distance of female parent is 4155.5cm,the average map distance between markers is 1.39 cm,and the linkage group length ranges from 68.6 to 178.0 cm.(3)QTL mapping of flowering time and leaf type traits of alfalfa was performed.A total of 36 QTLs of flowering time of alfalfa were obtained based on the data of three years.Among of these QTLs,there were 12 and 24 of male and female parent,respectively,and they were located on chromosomes 1-8,and the phenotypic variation of each QTL ranged from 2.16% to 17.56%.Moreover,a total of 60 QTLs of the leaf type traits of alfalfa were obtained based on the data of three years.All of these QTLs were located on chromosomes 1-8,and the phenotypic variation of each QTL ranged from 2.99% to 18.78%.Further,more than 10% of phenotypic variation can be explained by 13 QTLs,and there were 27,10 and 23 QTLs related to leaf area,leaf length and leaf width,respectively.Conclusion: Based on the major gene and ploy genes inheritance model analysis,2MG-ADI can be used as the most optimal candidate model for flowering time and leaf traits.The flowering time and leaf traits were mainly controlled by two pairs of major genes,and there were additive effect of genes.Finally,a genetic map of 32 linkage groups was conducted through the analysis of the sequencing data.Moreover,36 and 60 QTLs about flowering time traits and leaf traits of alfalfa were mapped,respectively.