| Chrysanthemum(C × morifolium Ramat.)is a highly artificial cultivation group.Its genetic background is complex and rich in genetic diversity.The phenotypic traits will be very different among the different varieties and the same cultivars under different cultivation environment.Facing such complex cultivars,how to identify and define the complex morphological traits is the first condition that we can identify chrysanthemum.On the basis of identification,understanding the genetic rules of important morphological traits is great significance for the directional improvement breeding of new chrysanthemum varieties.At present,morphological traits observation and related genetic analysis are most based on the"the handbook of distinctiveness,uniformity and stability test of new plant varieties of the People’s Republic of China(Chrysanthemum)".However,its metrical standard are often tend to the direct observation of morphological characters,there is still lack of uniform measurement and classification criteria.And,it even affects subsequent genetic analysis of these important traits.After years of observation,this study summarized the important components of the chrysanthemum morphological traits,redefined and found some important traits that can determine the chrysanthemum shape.Especially,we screen out a number of important quantitative traits,and conducted a quantitative classification analysis based on these traits.And then,in order to analysis these important quantitative traits,inheritance method of quantitative traits and genetic linkage map were conducted based on F1 populations from the parents with big difference in shape.And then QTL analysis further clarified the genetic variation mechanism of the above important traits.(1)In this study,299 ray florets from 151 large-flowered chrysanthemum varieties in China.First,as one of the most important indices of ray floret shape,the corolla tube merged degree(CTMD)was defined as the corolla tube length/ray floret length(CTL/RFL).Combined with a probability grading method and linear regression analysis,the CTMD was divided into 3 groups,flat,spoon and tubular,of which the CTL/RFL ranged from 0-0.20,0.20-0.60 and 0.60-1.00,respectively.Second,Q-mode cluster analysis indicated that the each groups could be further categorized into 3 types(straight,curved and atypical),based on other important variables in the ray floret.Finally,the ray floret was classified into 9 types,including flat-straight,flat-curve,flat-atypical,spoon-straight,spoon-curve,spoon-atypical,tubular-straight,tubular-curve,and tubular-atypical.(2)In this study,24 leaf morphological characteristics observed in 436 varieties,18 traits were further transformed to 13 leaf-shaped structural parameters.The quantitative analysis of the morphology of Chinese traditional large chrysanthemum leaves was carried out by combining the remaining four vein angles and two leaf morphology qualitative traits.The result of coefficient of variation showed that the 19 leaf characters have a high level of uniformity within cultivars(C.V<15%),significant diversity among cultivars(C.V from 13.32%to 34.29%).5 leaf traits that were selected based on correlation analysis and principal component analysis,including the leaf blade length/leaf width,the widest position of the leaf/leaf length,the widest position on the leaf/leaf blade length,right lower lobe length/leaf vein length,right lower lobe length/width and petiole length/leaf length.And,the leaf shape was divided into 16 types based on the above 5 traits,and the 16 types had clear boundaries.(3)In this study,as an important index of ray floret shape,the corolla tube merged degree(CTMD)and the relative number of ray florets(RNRF),the later was defined as the number of ray florets/number of florets(NRF/NF).2 F1 populations from 2 pairs of parents with big difference in CTMD and RNRF were used.A mixed genetic analysis major gene and poly-gene mixed inheritance analysis were conducted on the 18 important flower traits,15 leaf traits,flower color and anthocyanin content.Genetic analysis showed that the CTMD and RNRF were all described by the B-2 genetic model,two pairs of additive-dominance major genes.And,the heritability of major gene for these traits was more than 50%,indicating that the CTMD and RNRF were mainly controlled by genetic factors.The leaf blade length/width,the widest position on the leaf/leaf blade length,leaf lobe length/leaf vein length and leaf lobe length/width were quantitative traits controlled by major gene,and fitted the B-l,B-5,A-1 and B-2 model.And,the heritability of major gene for these traits was greater than 40%.The total anthocyanins content and total carotenoids content was all fitted to B-2.And,the heritability of major gene for them was 70.44%and 86.03%respectively.(4)This study used the combination II of(3)as mapping population,based on 305 F1 hybrids.Using the SLAF-seq technology,905,428 SNP markers were developed with 26,085 polymorphic markers.Finally,a high-density genetic linkage map of chrysanthemum was constructed.The map contains 6452 SNP markers,27 linkage groups with a total length of 4301.5 cM,a linkage group length of 84.66 cM(LG 18)-253.37 cM(LG9),and an average length of the linkage group of 159.315 cM.The average map distance of the map is 0.76 cM,and the number of markers on the linkage group is from 124(LG3)to 528(LG2).Chi-square test was performed on the genotype data of the 6452 markers in the mapping population.The results showed that there were 525 markers of segregation distortion,and the segregation distortion ratio was 8.14%.(5)Based on the genetic map in the(4),QTL analysis was performed on each trait of flower,leaf and flower color in the(3).Using interval mapping method,a total of 136 QTLs controlling flower traits were found,among which 16 QTLs controlling CTMD(CTL/RFL)and 3 major QTLs were detected.A total of 34 QTLs controlling the RNRF and 4 major QTLs were detected.A total of 51 QTLs controlling leaf traits were found,of which 2 QTLs controlling leaf length/leaf width were included;there were 6 QTLs controlling the left lower leaf lobe length/leaf vein length,and 12 QTLs controlling the left lower leaf lobe length/width.There were 3 QTLs controlling total anthocyanin content,and 2 QTLs controlling total carotenoid content,all of which were major QTLs.Eight possible candidate genes were screened using the sunflower genome annotation information of the Compositae,and 19 scaffold sequences were screened by the lettuce genome information.In conclusion,quantitative classification analysis was used to analyze some important morphological traits which was redefined and mined based on the original traits.This result not only clarifies the importance of these traits for the classification of chrysanthemum varieties,but also provides important and effective data information for the classification and identification of chrysanthemum varieties.Furthermore,genetic analysis of these traits based on F1 hybrid populations led to the discovery of QTLs and major QTLs affecting these traits.These results laid the foundation for molecular marker-assisted breeding,gene map cloning and comparative genomics analysis of flower type genetic mechanisms. |
PDF Full Text Request