Construction Of Genetic Map And QTL Mapping Of Traits Related To Grain Size In Common Buckwheat(F.Esculentum.)

Common buckwheat（Fagopyrum esculentum M.）,namely common buckwheat,is an annual or perennial crop of the genus Fagpyrum in Polygonaceae.It has the characteristics of self-incompatibility,short growth period and strong adaptability.Because of its many kinds of nutrition and health care ingredients（such as resistant starch,unsaturated fatty acid,quercetin,beta glucan,rutin,etc.）,and is rich in selenium,zinc,iron,potassium and other human body easy to lack of mineral nutrition elements,for diabetes,cardiovascular disease and constipation have prevention and therapeutic effect,has become one of the 21 st century human green food.As people pay more and more attention to the diet balance,the demand for common buckwheat is increasing,and the breeding of high yield and high quality common buckwheat varieties has become an important goal for buckwheat breeders.At present,the problems of low seed setting rate and low yield are common in the existing common buckwheat varieties.However,the research work of common buckwheat started late,which was difficult and the breeding technology was relatively backward.Modern molecular biology technology provides a new way for fast breeding of high yield common buckwheat.In this study,the hybrid offspring of Ukraine daliqiao（UD,large-seeds）and Youqiao 2（YQ₂,small-seeds）,two common buckwheat varieties with large grain size differences,were used as experimental materials to preliminarily identify QTLs for grain size related traits of common buckwheat.The main research results were as follows:1.Development of EST-SSR primer of Fagopyrum esculentumAt the early stage of the project team,transcriptome sequencing was carried out on 5 and 10 days grains of two common buckwheat varieties UD and YQ₂ with obvious differences in grain size.In this study,187034 Unigenes（the total length of the sequence is about 205214595 bp）obtained by transcriptome sequencing were searched for SSR sites,and 24,609 EST-SSR sites were found from 21376 Unigene.The distribution frequency of SSR in the transcriptome was 13.16%.A total of 18,969pairs of EST-SSR primers were designed and developed by setting the length of primers to 18-23 bp and the size of amplification products to 100～300 bp.Genetic diversity of 45 different buckwheat materials was analyzed by randomly synthesizing84 pairs of primers,and 81%（68 pairs）of SSR primers could amplify clear bands in45 different buckwheat materials,showing polymorphism.According to UPGMA clustering mapping,45 buckwheat varieties were divided into two categories（with similarity coefficient of 0.72 as the dividing line）,among which 34 varieties of sweet buckwheat were the first category and 11 varieties of bitter buckwheat were the second category.On this basis,34 varieties of sweet buckwheat were grouped into 4 categories（with the similarity coefficient of 0.76 as the dividing line）.This result shows the accuracy and practicability of EST-SSR designed and developed in this research.2.Population construction and phenotypic analysisThe phenotype comparison of UD and YQ₂ showed that the grain length,grain width and weight of UD were significantly greater than that of YQ₂,while the length-width ratio was slightly less than that of YQ₂.UD and YQ₂ hybridization were used to construct（UD and YQ₂）F₁ population.Statistical grain size and group related traits,the results show that compared with the parent,10 groups of 10 long,wide,hundred kernel weight and aspect ratio of the maximum grain is bigger in the parent UD is bigger,and its minimum value than parents in the grain smaller YQ₂ smaller,performance surplus separation phenomenon,and grain size distributions of various characters are related approximate continuous normal distribution,show the typical characteristics of quantitative character.3.Construction of genetic linkage map of Fagopyrum esculentum320 pairs of SSR primers and 336 pairs of In Del primers were developed and synthesized using transcriptomic sequencing data,and polymorphism primers were screened between the two parents（UD and YQ₂）.80 pairs of polymorphism primers were obtained from EST-SSR primers with a polymorphism ratio of 25.0%,and 145pairs of polymorphism primers were obtained from In Del primers with a polymorphism ratio of 43.2%.The marker genotypes of 208 individual strains in F₁population（UD and YQ₂）were detected by polymorphism primers,and a total of 265marker loci were obtained.A genetic linkage map of common buckwheat was constructed by means of the proposed method.There were 8 linkage groups in total,including 43 SSR sites and 96 In Del sites,with a total length of 1398.33 c M,an average spacing of 10.06 c M,and a linkage group length between 115.09 c M and243.75 c M.4.Preliminary mapping of QTLs related to grain size traits of Fagopyrum esculentumBased on UD and YQ₂ of F₁ generation of genetic group,208 per plant grain size of phenotypic data,combined with its genetic linkage map of common buckwheat grain size related traits of QTL localization,the results detected by common buckwheat grain size related traits QTL for a total of 37,with 11 common buckwheat QTL,grain length 3 common buckwheat grain QTL wide,11 common buckwheat hundred grain weight QTL and 12 common buckwheat length-width ratio QTL.According to the statistical analysis,QTLS of grain width,100-grain weight and length–to-width ratio were all detected near SWU＿Fe＿In Del076,QTLs of grain length and length–to-width ratio were all detected near SWU＿Fe＿In Del166 and SWU＿Fe＿In Del197,and QTLS of grain width and length–to-width ratio were all detected near SWU＿Fe＿In Del195,and QTLs of grain width and 100-grain weight were all detected near swu＿Fe＿Indel200.