| Tartary buckwheat(Fagopyrum tataricum(L.)Gaertn.)is a minor crop,rich in flavonoids,proteins,vitamins and other biologically active substances.It can reduce blood sugar,blood fat,blood pressure,reduce inflammation and antibacterial effects,so it has the huge market potential and development prospects.With the development of society,people’s demand for food crops gradually changed from the basic sustenance to the balanced nutrition.Because nutritional and health functions of Tartary buckwheat brought the gospel for the treatment of many diseases,this minor crop came gradually into the people’s vision and attracted great interest of the researchers.Starch content is a quantitative trait controlled by multiple factors,such as genetic factors and environmental factors,among which the main factor is genetic factors.In our country,Tartary buckwheat are the rich resource,and research on nutrients in Tartary buckwheat are mostly focused on flavonoids,but there is a lack of research on starch.This study used 221 recombined inbred line(XJ-RILs)populations derived from a cross between "Xiaomiqiao" and "Jinqiaomai 2" as experimental materials.By planting three seasons,this study determines their amylose content,amylopectin content,total starch content,the ratio of amylose to amylopectin and the ratio of amylopectin to amylose,analyzes their variation,frequency distribution and correlation.Based on the high-density SNP genetic linkage map and transcriptomic data of the XJ-RILs population,QTL mapping was performed for the investigated traits,and the related QTL segments were mined and the related candidate genes were detected.The results were as follows:1.Analysis of starch-related of traits in the XJ-RILs populationThe five traits of amylose content,amylopectin content,total starch content,ratio of amylose to amylopectin,and ratio of amylopectin to amylose showed super parental segregation in the XJ-RILs population.The mean values for the three seasons of amylose content in 2021 spring,2021 autumn and 2022 spring were 19.26%,19.76%and 22.39%respectively;the mean values for the three seasons of amylopectin content were 49.83%,32.09%and 40.46%respectively;the mean values for the three seasons of total starch content were 69.08%,51.84%and 62.85%respectively;the mean values for the three seasons of ratio of amylose content to amylopectin content were 0.39,0.62 and 0.56 respectively;and the mean values for the three seasons of ratio of amylopectin content to amylose content were 2.63,1.64 and 1.83 respectively.The coefficient of variation of 5 traits in 2021 spring is as follows:total starch content<amylose content=amylopectin content<ratio of amylose to amylopectin content<ratio of amylopectin to amylose content;the coefficient of variation of 5 traits in 2021 autumn is as follows:total starch content<amylose content<amylopectin content<ratio of amylose to amylopectin content=ratio of amylopectin to amylose;the coefficient of variation of 5 traits in 2022 spring is as follows:total starch content<amylose content<amylopectin content<ratio of amylose to amylopectin content=ratio of amylopectin to amylose.The correlation analysis of starch-related traits in the XJ-RILs population showed that amylose content of the XJ-RILs population was highly significantly negatively correlated with ratio of amylopectin content to amylose content in all three seasons(p<0.01).Amylopectin content was highly significantly negatively correlated with ratio of amylose content to amylopectin content(p<0.01),was highly significantly positively correlated with total starch content and ratio of amylopectin content to amylose content(p<0.01).Total starch content was highly significantly positively correlated with amylopectin content and ratio of amylopectin content to amylose content(p<0.01),was highly significantly negatively correlated with ratio of amylose content to amylopectin content(p<0.01).Ratio of amylose content to amylopectin content was highly significantly negatively correlated with amylopectin content,total starch content and ratio of amylopectin to amylose(p<0.01).Ratio of amylopectin content to amylose content was highly significantly negatively correlated with amylose content and ratio of amylose content to amylopectin content(p<0.01),was highly significantly positively correlated with amylopectin content and total starch content(p<0.01).2.QTL mapping of starch-related traits in the XJ-RILs populationSix QTLs related to amylose content were detected in three seasons,located on 3H,4H and 5H respectively.Among them,the phenotypic contribution rate of qAL4-1 and qAL5-1 was more than 10%,so they are master-effect QTLs controlling amylose content.Ten QTLs related to amylopectin content were detected in three seasons,located on 1H,2H,3H,4H and 7H respectively.Among them,the phenotypic contribution rate of qALP4-3 was more than 10%,so it was master-effect QTL controlling amylopectin content.Three QTLs related to total starch content were detected in three seasons,located on 1H,4H and 7H respectively.Twelve QTLs related to ratio amylose content to amylopectin content were detected,located on 1H,2H,3H,4H,5H and 7H respectively.Among them,the phenotypic contribution rate of qRLP4-1,qRLP4-2,qRLP4-3 and qRLP4-4 10%was more than 10%,so they are master-effect QTLs controlling ratio amylose content to amylopectin content.Thirteen QTLs related to ratio amylopectin content to amylose content were detected,located on 1H,3H,4H,5H and 7H respectively.Among them,the phenotypic contribution rate of qRPL4-2,qRPL4-3 and qRPL4-4 was more than 10%,so they are master-effect QTLs controlling ratio amylopectin content to amylose content.Among the QTLs of amylose content,three QTLs,namely qAL4-1,qAL4-3 and qAL4-4,were repeatedly detected in two seasons,and their phenotypic contribution rates were 10.12%,6.46%and 5.08%,respectively.They were located on the marker interval Block8791-Block8844 on the fourth chromosome.Among the QTLs of amylopectin content,two QTLs,namely qALP4-3 and qALP4-4,were repeatedly detected in two seasons,and their phenotypic contribution rates were 14.41%and 8.59%respectively.They were located on the marker interval Block8793-Block8836 on the fourth chromosome.Among the QTLs of ratio amylose content to amylopectin content,two QTLs,namely qRLP4-2 and qRLP4-3,were repeatedly detected in two seasons,and their phenotypic contribution rates were 18.42%and 17.34%respectively.They were located on the marker interval Block8793-Block8828 on the fourth chromosome.Among the QTLs of ratio amylopectin content to amylose content,three QTLs,namely qRPL4-2,qRPL4-3 and qRPL4-4,were repeatedly detected in two seasons,and their phenotypic contribution rates were 15.04%,15.33%,and 13.42%respectively.They were located on the marker interval Block8765-Block8836 on the fourth chromosome There were no QTLs of total starch content detected repeatedly in at least two seasons.The marker interval Block8793-Block8828 on the fourth chromosome was overlapping among the four traits of amylose content,amylopectin content,ratio amylose to amylopectin and ratio amylopectin to amylose,indicating that this interval is an important segment controlling starchrelated traits in Tartary buckwheat.3.Prediction of Candidate genesThe marker interval associated with amylose content(chromosome 4,Block8791 to Block8844)corresponds to a physical interval of 3.49 Mbp(chromosome 4,39.85 to 43.34 Mbp),and a total of 240 genes were detected within this interval.The marker interval associated with amylopectin content(chromosome 4,Block8793 to Block8836)corresponds to a physical interval of 2.8 Mbp(chromosome 4,39.85 to 42.65 Mbp),and a total of 182 genes were detected in this interval.The marker interval associated with ratio of amylose to amylopectin content(chromosome 4,Block8793 to Block8828)corresponds to a physical interval of 2.25 Mbp(chromosome 4 39.85 to 42.10 Mbp),and a total of 145 genes were detected in this interval.The marker interval associated with ratio of amylopectin to amylose content(chromosome 4,Block8793 to Block8830)corresponds to a physical interval of 2.89 Mbp(chromosome 4 39.85 to 42.74 Mbp),and a total of 188 genes were detected within this interval.29 genes were selected for excellent expression in seeds:Among them,22 genes were effectively annotated.Analysis of the variation sites of the above genes based on high density SNP genetic map showed that seven genes occurred SNP or Indel variation between parents,namely FtPinG0005109900.01,FtPinG0009329200.01,FtPinG0008468900.01,FtPinG0006225500.01,FtPinG0002636200.01,FtPinG0004897100.01,and FtPinG0007371600.01.The variation sites were in the 5’ UTR region,intron region and 3’ UTR region.Seven genes had SNP variation sites,while only one gene had Indel variation site,namely FtPinG0004897100.01.Except for FtPinG0004897100.01,the remaining six genes had only one SNP variation site.The variation sites of the above 7 genes were validated by sequencing between the parents,and the variation sites of 4 genes(FtPinG0009329200.01,FtPinG0002636200.01,FtPinG0004897100.01 and FtPinG0007371600.01)were validated,.FtPinG0009329200.01 was annotated to UDP-galactose transporter,FtPinG0004897100.01 was annotated to GRAS protein,and FtPinG0002636200.01 was annotated to galactosyl transferase,and the above genes might be involved in the biosynthesis process of starch in buckwheat starch. |
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