The Candidate Gene Association Analysis For Main Ornamental Traits In Hemerocallis Spp.

Flower color is one of the most important factors affecting the ornamental quality of horticultural plants,and it is also one of the hot spots for the study of ornamental plants.The Hemerocallis spp.is rich in germplasm resources and diverse in morphology and has excellent ornamental value.This test assessed genetic relationships and classification by phenotypic traits and EST-SSR molecular markers and carried out candidate genes association analysis of flower color traits and other ornamental traits,which based on the systematic collection of Hemerocallis germplasm resources.Reveal the genetic background of Hemerocallis germplasm resources,improve the utilization rate of Hemerocallis germplasm resources,discover excellent genetic resources,accelerate the application of molecular breeding in Hemerocallis plants,provide theoretical basis and core materials for the cultivation of higher quality ornamental species.The main results of this study are as follows:1.A database was constructed that containing 141 lines(8 species,1 variant,5 wild species,127 cultivars)and 34 phenotypic traits.As one of the important ornamental traits,the flower color has a total of 7 color groups,there are 4 germplasms is different of petals and sepals color.The yellow group had the most germplasm,with 74(48.37%),and the sepals and petals were the same color group;purple and purplish red germplasm were less,6 petals were purple(3.92%)and 2 were purple(1.31%).The rhythm of flowering time of single flower was obvious,divided into two groups:morning flowering group(5:00?10:00)and evening flowering group(18:00?23:00),with 84 and 57 materials respectively.2.The results of principal component analysis show that the cumulative contribution rate of the first 8 principal components is 88.30%(>85%),of which the contribution rate of Prinl is 31.48%,and the Prin2 is 22.24%,mainly including the sepal color,petal color,sepal length,sepal width,petal length,petal width,single flower flowering time and other traits.Among the 34 phenotypic traits,phenotypic diversity of Hemerocallis was mainly focused on floral traits,among them,the petal width,sepal width,flower diameter,bud fresh weight and the leaf width were significantly positively correlated between the two of all.The variation coefficient of 9 characters were extremely significant differences,including flower diameter,petal length,petal width,sepal length,sepal width,leaf length,leaf width,scape diameter and scape height.3.The EST-SSR primers used in this study were designed from H.'Datong Huang Hua' transcriptome sequencing.Among 304 pairs of primers,68 pairs were polymorphic.Based on the results of transcriptome sequencing,304 pairs of EST-SSR primers were developed,among which 68 pairs were polymorphic,a total of 499 polymorphic fragments were amplified,with an average of 7.34(2 to 25).The average of the polymorphism information content(PIC)was 0.6064(0.2595-0.9065),the Nei's was 0.5914(0.2097-0.9077)and the Shannon's(1)was 1.2935(0.4770-2.6533).4.The average genetic similarity coefficient among 141 Hemerocallis germplasms was 0.8621(0.7778-1.0000)calculated by NTSYSpc2.10 software.Using STRUCTURE2.3.4 software for population structure analysis,the results show K=2.The linkage disequilibrium analysis was performed using TASSEL 4.3.6 software and the LD value was calculated.Among the 2081 combinatorial sites formed by 68 pairs of EST-SSR primers,there were 1439 combinations with different degrees of linkage disequilibrium,accounting for 69.15%of the total loci.Among them,there are 895 linkage disequilibrium combinations with r2<0.05,accounting for 43.01%of the total loci,and 439 combinations with r2<0.01,accounting for 21.10%.5.Comparison between GLM and MLM in TASSEL 4.3.6 software.The results showed that the GLM could detect more association sites,but the P value associated marker deviated significantly from the expected P value,indicating that only the influence of population structure was considered in the GLM model,and there were many false positive sites.In the MLM model considering both the population structure(Q)and the kinship(K),the associated markers are significantly reduced,and the pseudo-association flag caused by false positives is greatly reduced.The result is more reliable and accurate,at the same time,the P value detected is closer to the expected value.6.Using MLM model(Q+K),141 germplasm resources,21 phenotypic traits,and 68 markers were analyzed for association analysis.A total of 65 markers and 21 traits were detected in different degrees of association.The average r2 is 0.1865,in which the largest association is between SAU00047 and the sepal length.It's P value is the minimum 0.00000088,which can explain the phenotypic variation rate of 47.00%There were 22 highly significant(P<0.01)markers associated with 17 traits,of which 6 markers were associated with flower color.Significantly related(P<0.05)markers were 50,and some markers were associated with multiple traits,of which SAU01115 was associated with flower diameter,sepal length,petal length and bud length 4 traits,and they were associated both in 2016 and 2017.SAU01083 and SAU01082 were significantly associated with lightness of sepal and petal(L*IN and L*OUT),with a phenotypic contribution rate of 10.23%and 15.79%,respectively.The target gene of SAU01083 and SAU01082 is the homologous gene of TT4(chalcone synthase,CHS).SAU01105 is significantly associated with the total chromatic aberration of the sepal(?E*IN).The four markers SAU01151,SAU01144,SAU01149,and SAU01155 all have a significant correlation with flower color.They are all related to the pigment substances in carotenoids and make the tepals appear yellow.