| Corn is one of the world’s three major crops,and is rich in starch,accounting for more than 80%of the world’s starch.Starch quality-related traits are complex quantitative traits.Studying the relationship between starch synthesis-related genes and starch quality traits is of great significance for breeding elite maize varieties and improving corn starch quality.Starch branching enzyme(SBE)is one of the four key enzymes in starch synthesis,which is mainly involved in the synthesis of starch branches.This study first re-sequenced SBE genes from 335 inbred lines,68 local species,and 32 yarrows,and analyzed the sequence variation of four SBE genes in three groups;Genotype and starch quality related phenotype(peak viscosity PV,through viscosity TV,final viscosity FV,breakdown BD,setback SB,peak time PT,pasting temperature PTP,onset temperature To,peak temperature Tp,conclusion temperature Tc,enthalpy △Hg,and crude starch content starch)were used for candidate gene association analysis to screen for excellent allelic variation sites.The relevant results are as follows:1)The results of phenotypic analysis showed that 12 starch quality traits have extensive variation in 335 elite inbred lines.The coefficient of variation of breakdown was the largest.The coefficient of variation of peak temperature was the smallest.There is a certain correlation between 12 traits.The generalized heritability of trough viscosity is the highest,and the generalized rate of peak time is the lowest.There were significant differences in 9 traits between different years,and there were significant differences in all traits among different lines.There is a significant difference between interaction of line and year.2)SBE genes’ sequence variation analysis showed that among the three populations,1102 polymorphic sites were found in BEⅠ gene,including 916 SNPs(a SNP per 9.9bp)and 186 InDels(a InDel per 50bp);There were 1519 polymorphic sites in BEⅡa gene,including 1302 SNPs(a SNP per 9.7bp)and 217 InDels(a InDel per 58.8bp);There were 1616 polymorphic sites in BEⅡb,including 1353 SNPs(a SNP per 14.5bp)and 263 InDels(a InDel per 76.9bp);a total of 1044 sites were found in the BEⅢ,including 903 SNPs(a SNP per 7.6bp)and 141 InDels(a InDel per 47.6bp).The nucleotide polymorphism π value ranges from 0.00711 to 0.01467.According to the changes of π and the LD in the three groups,it was found that the BEⅡb gene was the most selective in the process of domestication and improvement of the corn,and the selection of BEⅢ was the smallest.3、Based on the association analysis of candidate genes,it was found that a total of 21 significant sites related to starch quality were detected.A total of 4 sites that were significantly associated with enthalpy were detected in the BEⅡa.InDel(-/C)on site 5969 had the highest interpretation rate of enthalpy,which was 4.28%.According to the proportion of the mutation sites in the three groups and the size of the surrounding nucleotide polymorphisms,it was found that InDe15969,SNP403 and InDe15967 were strongly selected during the domestication and improvement of the corn.Four significant sites of the BEⅡb were detected to be significantly associated with the setback,and the contribution rate of the SNP(A/G)on site 8152 was the highest,reaching 3.95%.In addition,the sites SNP17249,SNP8152 and SNP17786 were found to be strongly selected during the domestication and improvement of the corn.In BEⅢ,13 sites that were significantly associated with enthalpy and starch content were detected.Among them,InDel(G/-)on site-830 explained the highest contribution to starch content,reaching 4.88%.Sites InDel-830,SNP-356,SNP3918,SNP4867,SNP4868 and SNP4817 are strongly selected during domestication and improvement of the corn. |
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