| Maize(Zea mays L.)is one of the main crops,important food,feed and industrial raw material in China.Starch is the main component of maize kernels,accounting for about 75%.It consists of two polymers: amylose and amylopectin.The ratio of amylose to amylopectin affects the physicochemical properties,nutritional value and industrial use of maize starch.The amylose content in normal maize kernels is about 25%,and maize with more than 50% amylose content is high amylose maize.Amylose is an important industrial raw material.It plays an important role in food,medical treatment,textile,paper making,packaging and environmental protection.It is an ideal food for patients with diabetes and gallstones.Starch synthesis is regulated by a variety of enzymes,including sucrose synthase(SUS),ADPG pyrophosphorylase(AGPase),granule-bound starch synthase(GBSS),soluble starch synthase(SSs),starch branching enzyme(SBE)and starch debranching enzyme(SDBE).Ae(Amylose extender)is the coding gene of SBE.Ae1-5180 dominant mutation can effectively increase amylose content.The amylose content of it can be increased to 72%,but the total starch content and yield are reduced.Through backcross breeding,Ae1-5180 dominant mutant gene was introduced into excellent maize inbred lines with different backgrounds.Materials with increased amylose content and less yield traits were screened to create high-amylose maize varieties,so as to accelerate the breeding process of high-amylose maize.In this study,Ae1-5180 dominant mutant,its wild type and 25 excellent maize inbred lines were used as materials.The Ae1-5180 mutant and its wild type were analyzed for phenotype,physical and chemical properties and endosperm submicroscopic structure.Analysis of starch synthesis pathway key enzyme activities and its coding genes expression to preliminarily analyze the mechanism of increase in amylose content of Ae1-5180 dominant mutants.Meanwhile,molecular marker was developed based on mutation sites of Ae1-5180 gene.In addition,the Ae1-5180 mutants was crossed with 25 excellent maize inbred lines,by the preliminary agronomic traits analysis of F1 hybrids,and molecular marker-assisted selection to create near-isogenic lines of high amylose maize with different backgrounds.The main research contents of this article are as follows:1.Phenotypic,physicochemical properties and submicroscopic structure analysis: In Ae1-5180 mutant,the grains are wrinkled,the hundred-kernel weight was significantly reduced,and the amylose content was significantly increased,reaching 60.88% at the maturity stage;the short chain part with a degree of polymerization <21 significantly reduce while the long chain part increase,the peak temperature and termination temperature of starch gelatinization increase,and the gelatinization enthalph decreases;starch granules changed into irregular shapes,the size is uneven,smaller and there are more matrix proteins on the surface,the number of starch granules and protein bodies increases,and the protein bodies are evenly distributed around the starch granules.2.Analysis of starch synthesis pathway key enzymes and gene expression: The expression of SBEIIb in Ae1-5180 mutant is significantly decreased from 10 d to 30 d after pollination,and the activity of SUS,APGase,SBE and SDBE are significantly decreased.3.Development of molecular markers and analysis of agronomic traits: A dominant molecular marker,MU1ae5180-F/R,was developed according to the insertion of MU1 at-524 bp in the promoter region of Ae1-5180 mutant.Through analysis of the agronomic traits and grain quality,it was found that the cross of Ae1-5180 mutant with JI H214,W16F41 or CA240 as parents could significantly increase the amylose content of F1 generation with the minimum yield change.This study is helpful to further understand the mechanism of increasing amylose content in the Ae1-5180 mutant,and has important reference significance for accelerating the breeding process of high amylose maize and cultivating high amylose maize varieties. |
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