Structural Analysis And Genetic Basis Of Amylopectin In Different Glutinous Rice Varieties

Glutinous rice has a long history and has a wide range of application value and prospect.Glutinous rice has significant difference with non-glutinous rice because it contains almost no amylopectin,and the difference of amylopectin structure forms the difference of quality among different glutinous rice varieties.In order to clarify the effect of amylopectin fine structure on the physical and chemical properties of glutinous rice starch,it is of great significance to find out the role of soluble starch enzyme gene SSⅡa in the fine structure of amylopectin and the physicochemical properties of amylopectin,which is of great significance to reveal the genetic basis of amylopectin structure formation in glutinous rice.In this study,29 glutinous rice varieties were used to determine the amylopectin structure,starch physical and chemical properties and quality,and the base variation types of 4 SNPs on SSⅡa gene were detected by allele specific PCR.The base variation of four SNP sites on SSⅡa gene,the haplotype,starch fine structure and physicochemical properties of starch were analyzed.The main results are as follows:1.The amylose content of 29 glutinous rice varieties and the detection of the +1G/T site of the 1st intron of Wx gene showed that AC of 29 glutinous rice varieties was extremely low and the +1 site of the 1st intron of Wx gene was all T,indicating that AC had little effect on the physicochemical properties of glutinous rice starch.The fine structure of amylopectin was the decisive factor affecting the physicochemical properties of starch in the tested glutinous rice varieties.2.The fine structure of amylopectin of different glutinous rice varieties was determined by ion chromatography,and the degree of polymerization of amylopectin was classified into short chain(DP6-12),medium and long chain(DP13-24),long chain(DP25-36),extra-long chain(DP≥37)and average degree of polymerization(DPn).The results showed that the fine structure parameters of amylopectin in 29 glutinous rice varieties were different.3.The correlation between the fine structure of amylopectin and the physicochemical properties of starch was analyzed.The results showed that the fine structure of ΣDP6-12 was significantly negatively correlated with HPV,CPV,CSV,Pe T,Pa T,To,Tp and Tc,was significantly negatively correlated with PKV and ΔH.ΣDP13-24 was significantly positively correlated with HPV,CPV,CSV,Pe T,Pa T,To,Tp and Tc.ΣDP25-36 was negatively correlated with Pa T,To,Tp and Tc,while DPn was positively correlated with Pe T and Pa T.The fine structure of amylopectin had no correlation with the number and size of starch granules and the crystallinity of starch.4.The correlation between the starch physical and chemical properties was analyzed.The results showed that the thermodynamic properties of the starch physical and chemical properties in 29 glutinous rice varieties were significantly correlated with most of the characteristic values of RVA spectrum.The relative crystallinity was negatively correlated with SBV.ΔH was significantly negatively correlated with starch grain volume and positively correlated with relative crystallinity.5.Four missense SNP sites of soluble starch synthase gene SSⅡa in 29 glutinous rice cultivars were analyzed.The results showed that there were 2 missense SNP sites of SSⅡa gene 264 in G and 27 in C in 29 glutinous rice cultivars.At site 1810,there were 27 in A and 2 in G.There were 9 in site A and 20 in site G at 2209,11 in site GC and 18 in site TT at 2340/2341.Each point mutation of SSⅡa could be divided into 3 haplotypes,including 9for HP1(C-A-A-GC),18 for HP2(C-A-G-TT),and 2 for HP3(G-G-G-GC).6.The differences between SNP sites and habotypes of SSⅡa gene and amylopectin fine structure and starch physical and chemical properties were analyzed.The results showed that there were significant differences in amylopectin chain length distribution,RVA partial eigenvalues and thermodynamic parameters at sites 264 and 1810 of SSⅡa gene,and significant differences in RVA partial eigenvalues at sites 2209.There were significant differences in amylopectin chain length distribution,RVA partial eigenvalues and thermodynamic parameters at 2340/2341 sites.Compared with HP1 and HP2,HP3 has higher RVA spectrum characteristic value,thermodynamic parameter value,middle and long chain of amylopectin DP13-24,and lower short chain of DP6-12 in each habtype.HP3 had more starch granules than HP1.HP2 has more DP25-36 long chains than HP3.