Engineering high amylose and resistant starch in maize by CRISPR/Cas9-mediated editing of starch branching enzymes

To improve the amylose content(AC)and resistant starch content(RSC)of maize kernel starch,we employed the CRISPR/Cas9 system to create mutants of starch branching enzyme I(SBEI)and starch branching enzyme IIb(SBEIIb).A frameshift mutation in SBEI(E1,a nucleotide insertion in exon 6)led to plants with higher RSC(1.07%),lower hundred-kernel weight(HKW,24.71±0.14 g),and lower plant height(PH,218.50±9.42 cm)compared to the wild type(WT).Like the WT,E1 kernel starch had irregular,polygonal shapes with sharp edges.A frameshift mutation in SBEIIb(E2,a four-nucleotide deletion in exon 8)led to higher AC(53.48%)and higher RSC(26.93%)than that for the WT.E2 kernel starch was significantly different from the WT regarding granule morphology,chain length distribution pattern,X-ray diffraction pattern,and thermal characteristics;the starch granules were more irregular in shape and comprised typical B-type crystals.Mutating SBEI and SBEIIb(E12)had a synergistic effect on RSC,HKW,PH,starch properties,and starch biosynthesis-associated gene expression.SBEIIa,SS1,SSIIa,SSIIIa,and SSIIIb were upregulated in E12 endosperm compared to WT endosperm.This study lays the foundation for rapidly improving the starch properties of elite maize lines.

Combining QTL Mapping and Multi-Omics Identify Candidate Genes for Nutritional Quality Traits during Grain Filling Stage in Maize

The nutritional composition and overall quality of maize kernels are largely determined by the key chemical com-ponents:protein,oil,and starch.Nevertheless,the genetic basis underlying these nutritional quality traits during grainfilling remains poorly understood.In this study,the concentrations of protein,oil,and starch were studied in 204 recombinant inbred lines resulting from a cross between DH1M and T877 at four different stages post-pollination.All the traits exhibited considerable phenotypic variation.During the grain-filling stage,the levels of protein and starch content generally increased,whereas oil content decreased,with significant changes observed between 30 and 40 days after pollination.Quantitative trait locus(QTL)mapping was conducted and a total of 32 QTLs,comprising 14,12,and 6 QTLs for grain protein,oil,and starch content were detected,respectively.Few QTLs were consistently detectable across different time points.By integrating QTL analysis,glo-bal gene expression profiling,and comparative genomics,we identified 157,86,and 54 differentially expressed genes harboring nonsynonymous substitutions between the parental lines for grain protein,oil,and starch con-tent,respectively.Subsequent gene function annotation prioritized 15 candidate genes potentially involved in reg-ulating grain quality traits,including those encoding transcription factors(NAC,MADS-box,bZIP,and MYB),cell wall invertase,cellulose-synthase-like protein,cell division cycle protein,trehalase,auxin-responsive factor,and phloem protein 2-A13.Our study offers significant insights into the genetic architecture of maize kernel nutritional quality and identifies promising QTLs and candidate genes,which are crucial for the genetic enhance-ment of these traits in maize breeding programs.

Analysis of Genetic Variation and Population Structure of Starch Synthesis-related Genes in Indica Rice Cultivars

In this study, 34 molecular markers of starch synthesis-related genes were used to evaluate the genetic variation and population structure of 87 indica rice cultivars from different countries and regions. The results showed that a total of 80 alleles were amplified using 34 primer pairs, with an average of 2.5 alleles per locus. The allele number varied from 2 to 6 among various cultivars. Shannon＇s diversity index of molecular markers varied from 0.303 to 0.796, with an average of 0.539. Polymorphism information content （PIC） varied from 0.084 to 0.658, with an average of 0.295. The genetic similarity coefficients of 87 indica rice cultivars ranged from 0.265 to 0.990, indicating significant genetic differences of starch synthesis-related genes among different cultivars, but the variation frequency of alleles varied among different cultivars. Population structure analysis showed that these 87 indica rice cultivars were divided into three categories. Genetic differences were small within the same category but great among different categories. Moreover, indica rice cultivars with simple genetic components accounted for 39.1% and those with complex genetic background accounted for 60.9%. This study may not only provide theoretical basis for genetic improvement of rice starch quality, but also lay a solid foundation for subsequent association analysis of rice quality-related traits.

Screening and Application of Molecular Markers for Starch Synthesis-related Genes in Rice

In this study, the genotypes of starch synthesis-related genes were systematically screened from different rice varieties using molecular markers. The results showed that starch synthesis-related genes were highly polymorphic between indica and japonica varieties, as they greatly variated among indica varieties, but were conserved among japonica varieties. The genotypes of two indica varieties9311 and Minghui 63 were more similar to that of japonica varieties. Two or three alleles of six starch synthesis-related genes were found in 28 japonica parental varieties. Four genotypes of two soluble starch synthase genes, SSIIa and SSIIIa,were detected in 88 stable lines derived from the cross of Kanto 194/ Wujing 13 using molecular markers.

Effect of high temperature on the expressions of genes encoding starch synthesis enzymes in developing rice endosperms

High temperature is the major environmental factor affecting grain starch properties of cooking rice cultivars. In this study, two non-waxy indica rice genotypes, cv. 9311 and its mutant with extremely high amylose phenotype（9311eha） were used to study the differential expressions of genes in starch synthesis and their responses to high temperature（HT）. Significant increase in apparent amylose content and hot-water-soluble starch content in mutant 9311 eha were genetically caused by a substitution from AGTTATA to AGGTATA at the leader intron 5′ splice site in Wx gene. This mutation resulted in different m RNA transcript levels, m RNA splicing efficiencies and protein levels of Wx between the two rice genotypes, which also lead to the genotype-dependent alteration in the temporal pattern of Wx transcription and granule-bound starch synthase（GBSS） activity in response to HT. However, changes in the activities of other starch synthesizing enzymes and their expressions of distinct isoform genes were not significant with the Wx gene mutation, thus only minor difference in the particle size of starch granule, chain-length distribution and gelatinization enthalpy were found between the two genotypes. The temporal-specific expression of multiple isoform genes responsive to different temperature regiments indicated that the reduction of GBSS transcript expression under HT was generally accompanied by the decreased expressions of SSSIIa, SSSIIIa and SBEIIb. Consequently, high temperature-ripened grains in 9311 eha showed high proportion of intermediate and long B chains and somewhat lower level of short A chain compared to the wildtype. The temperature-dependent alteration of amylose content was not only attributed to the reduced expression of GBSS, but also associated with the complimentary effect of SSSIIa and SBEIIb.

The Source of Genes Related to Rice Grain Starch Synthesis Among Cultivated Varieties and Its Contribution to Quality

The property of starch in rice grain endosperm is a very important determinant for rice quality, and it is essential to understand the genetic effect of the genes related to starch synthesis in high-yielding rice varieties for rice quality improvement. The physicochemical properties （e.g., amylose content, gel consistency, and RVA profile） were assessed on 53 rice varieties, including certain typical indica/japonica landraces and certain high-yielding modern varieties. And molecular markers for Sbel, Sbe3 developed on the basis of sequence diversities between the rice subspecies indica and japonica, together with PCR-Acc I marker for Wx gene were used to investigate the genotypes of 53 rice cultivars. The result showed that the developed molecular markers for Wx, Sbel, Sbe3 could distinguish indica or japonica alleles at three loci. Among all the 53 rice cultivars, six genotypes were observed when Sbel, Sbe3, and Wx loci were considered together, while the genotypes of WxiSbelJSbe3i and WxiSbelJSbe3J were absent. In order to explore the genetic effects of the three genes, especially for starch branching enzyme genes, ANOVA and multiple comparison analysis were conducted. The results showed that rice cultivars with different genotypes exhibited different phenotypes, including amylose content, gel consistency and certain RVA characteristics, and the significant differences among the six genotypes were observed. It was concluded that these three genes had randomly recombined during the process of the rice variety development. And the genetic effects of indica and japonica alleles at three gene loci were different, of which, Wx gene plays a major role in determining the starch properties, followed by Sbel and Sbe3, and the genetic effects of Sbel and Sbe3 in different backgrounds （Wx~, WxJ） are different. The results have provided a clue for rice good quality variety development, and the molecular markers will benefit to the improvement in quality of rice.

Temperature Stress at Grain Filling Stage Mediates Expression of Three Isoform Genes Encoding Starch Branching Enzymes in Rice Endosperm

An early-maturity indica rice variety Zhefu 49, whose grain quality and starch structure are sensitive to environmental temperature, was subjected to different temperatures （32℃ for high temperature and 22℃ for optimum temperature） at the grain filling stage in plant growth chambers, and the different expressions of three isoform genes （SBEI, SBEIII and SBE/V） encoding starch branching enzyme （SBE） in the endosperms were studied by the real-time fluorescence quantitative PCR （FQ-PCR） method. Effects of high temperature on the SBE expression in developing rice endosperrns were isoform-dependent. High temperature significantly down-regulated the expressions of SBEI and SBEIII, while up-regulated the expression of SBEIV. Compared with SBEIV and SBEIII, the expression of SBEI gene in Zhefu 49 rice endosperms was more sensitive to temperature variation at the grain filling stage. This study indicates that changes in weather/climate conditions especially temperature stress influence rice grain formation and its quality as evidenced by isoform expression.

Effects of RNAi Silencing of SSIII Gene on Phosphorus Content and Characteristics of Starch in Potato Tubers

The sense and antisense fragments of the soluble starch synthase （SSII1） gene and the intron fragment of somatic embryogenesis receptor-like kinase （SERK1） gene were cloned from potato using PCR techniques. The RNAi plant expression vectors pBI-SSIII-RNAi and pBIC-SSIII-RNAi were constructed which containing fusion fragment of ＂sense fragment-intron-antisense fragment＂ driven by the constitutive expression promoter CaMV 35S and the tuber-specific expression promoter CIPP, respectively. The putative transgenic plants of potato cultivars Kexin-1 and Kexin-4 were obtained using Agrobacterium-mediated transformation method. PCR assay showed that the interference fragment of SSlll gene was integrated into potato genome. The RT-PCR analysis showed that the expression of SSlll gene was repressed apparently on the transcription level. Starch granules of the transgenic potato plants were different in morphology and became cracked in starch granule centre compared with the non-transgenic control plants. The amylose content of starch was increased by 2.68-29.05%, amylopectin to amylose ratio of starch had declined significantly, and the phosphorus content of the starch of the transgenic plants was reduced 9.94-58.36% compared with control plants. The results could provide certain foundation for improvement of potato starch quality.

Characterization of starch morphology, composition, physicochemical properties and gene expressions in oat

Starch is the major carbohydrate in oat （Avena sativa L.） and starch formation requires the coordinated actions of several synthesis enzymes. In this study, the granule morphology, composition and physicochemical properties of oat starch, as well as the expressions of starch synthesis genes were investigated during oat endosperm development. Under the scanning electron microscopy （SEM）, we observed that the unique compound granules were developed in oat endosperms at 10 days post anthesis （DPA） and then fragmented into irregular or polygonal simple granules from 12 DPA until seed maturity. The amylose content, branch chain length of degree of polymerization （DP=13-24）, gelatinization temperature and percentage of retrogradation were gradually increased during the endosperm development; whereas the distribution of short chains （DP=6-12） were gradually decreased. The relative expressions of 4 classes of 13 starch synthesis genes characterized in this study indicated that three expression pattern groups were significantly different among gene classes as well as among varied isoforms, in which the first group of starch synthesis genes may play a key role on the initiation of starch synthesis in oat endosperms.

Identification and gene mapping of the starch accumulation and premature leaf senescence mutant ossac4 in rice

The rice mutant ossac4(starch accumulating 4)was raised from seeds of the rice(Oryza sativa L.)indica maintainer line Xinong 1B treated with ethyl methanesulfonate.The distal and medial portions of the second leaf displayed premature senescence in the ossac4 mutant at the four-leaf stage.Physiological and biochemical analysis,and cytological examination revealed that the ossac4 mutant exhibited the premature leaf senescence phenotype.At the four-leaf stage,the leaves of the ossac4 mutant exhibited significantly increased contents of starch compared with those of the wild type(WT).Quantitative real-time PCR analysis showed that the expression levels of photosynthesis-associated genes were down-regulated and the expression levels of glucose metabolism-associated genes were abnormal.Genetic analysis indicated that the ossac4 mutation was controlled by a single recessive nuclear gene.The OsSAC4 gene was localized to a 322.7-kb interval between the simple-sequence repeat marker XYH11-90 and the single-nucleotide polymorphism marker SNP5300 on chromosome 11.The target interval contained 20 annotated genes.The present results demonstrated that ossac4 represents a novel starch accumulation and premature leaf senescence mutant,and lays the foundation for cloning and functional analysis of OsSAC4.

Diurnal Changes in the Transcription Profiles of Genes Encoding Starch Synthesis-related Enzymes in Wheat Grains under Field Conditions

[Objective] During the filling stage of plant growth and development, storage starch is diurnally synthesized and accumulated in the grains from cereal crops, but the underlying molecular mechanism is unclear. [Method] In this study, grains from the bread wheat cultivar Zhoumai 18 grown in fields were harvested at 15 d after anthesis, and quantitative real-time reverse transcription polymerase chain reaction(qPCR) was used to measure the transcriptional levels of 26 genes encoding starch synthesis-related enzymes at 2 h intervals throughout a diurnal cycle. [Result] Our findings indicated that storage starch was persistently synthesized in wheat grains throughout a 24 h period. The diurnal patterns of the transcriptional levels of 26 genes in wheat grains were classified into two groups. The 13 genes in Group 1 were temporally and highly expressed in wheat grains,and their encoded proteins could play crucial roles in starch synthesis. The other 13 genes in Group 2 were characterized by low or no transcription in wheat grains throughout a diurnal cycle, suggesting their function in the synthesis or degradation of transitory starches in wheat grains. [Conclusion] These results provide information on the molecular mechanism of storage starch synthesis in higher plants.

Expression Regulation of Starch and Storage Protein Synthesis Related Genes in Rice Grains

Starch and the storage proteins are the main nutritious substances in crop grains,and their composition and content in grains play a decisive role in the grain quality of rice and other staple food crops.This review has mainly summarized the new advances in the expression regulation of starch and storage protein synthesis related genes in rice grains.Moreover,the challenges of the starch and storage protein synthesis substances in rice genetic improvement were also discussed.This review will provide important information for genetic improvement of grain quality in rice and,potentially,other staple cereals.

Effects of Agrobacterial<i>rol</i>-Genes on the Thermodynamic and Structural Features of Starches Extracted from Potato Microtubers

Wild-type potato (Solanum tuberosum L.) plants and their transformants harboring agrobacterial rolB or rolC genes under control of the patatin class I promoter were cultured in vitro. These plants were used as a source of single-node stem cuttings. The structure of native starch in tubers formed on cuttings was determined using methods of X-ray scattering and differential scanning microcalorimetry (DSC). It was found that in starch from tubers of rolB plants the melting temperature of crystalline lamella was lower and their thickness was less than that in wild-type potato. In tubers of rolC plants starch differed from starch in wild-type plants by a higher melting temperature, reduced melting enthalpy, and a greater thickness of crystalline lamellae. The melting of starch from tubers of rolC plants proceeded as the melting of two independent crystalline structures with melting temperatures of 338.0°K and 342.8°K. Overall data show that starches of different structure can be obtained by using transgenic approach.

Genetic Evaluation of Starch Synthesis-Related Genes and Starch Quality Traits in Special Rice Resources

The genetic diversity of 36 rice landraces and 43 breeding materials in the upper reaches of the Yangtze River in China was studied by intragenic molecular markers of 26 starch synthesis-related loci.And research on quality traits such as the amylose content(AC),gel consistency(GC)and alkali spreading value(ASV)to analyze genetic differences in quality traits.The results showed that the number of alleles,average gene diversity and polymorphism information content values of landraces were higher than those of breeding materials.The genetic similarity coefficient(GS)of 79 rice materials ranged from 0.392 to 1,with an average of 0.757.There were significant variations in the quality traits of rice landraces and breeding materials,and the high-quality compliance rates were low,only 6.3%of the varieties have an amylose content that reached grade 1.The results of cluster analysis and population structure analysis are generally consistent;that is,the two resource types are closely related and cannot be clustered independently.This study can provide a basis for genetic improvement of rice starch quality.Make full use of the quality genetic diversity of landraces in modern breeding work,further broaden the genetic base of rice and improve rice quality.

Optimization of slow-release fertilizer application improves lotus rhizome quality by affecting the physicochemical properties of starch

To achieve the dual goals of high yield and good quality with low environmental costs,slow-release fertilizer(SRF)has been widely used in lotus cultivation as new type of fertilizer instead of traditional nitrogen fertilizer.However,the optimal amount of SRF and how it would promote lotus rhizome quality remain unclear.This study was designed to investigate the photosynthetic characteristics and the synthesis,accumulation,and physicochemical properties of lotus rhizome starches under six SRF levels(CK,S1,S2,S3,S4,and S5).Compared with CK(0 kg ha^(–1)),the net photosynthetic rate(P_(n))and SPAD values of leaves remained at higher levels under SRF treatment.Further research showed that SRF increased the lotus rhizome yield,the contents of amylose,amylopectin,and total starch,and the number of starch granules.Among the six SRF levels,S3(1035 kg ha^(–1))showed the greatest difference from CK and produced the highest levels.With the increasing SRF levels,the peak,hot and final viscosities decreased at first and then increased,but the setback viscosity and pasting temperature increased.In order to interpret these changes at the molecular level,the activities of key enzymes and relative expression levels of starch accumulation related genes were analyzed.Each of these parameters also increased under SRF treatment,especially under the S3 treatment.The results of this study show that SRF,especially S3(1035 kg ha^(–1)),is a suitable fertilizer option for lotus planting which can improve lotus rhizome quality by affecting starch accumulations related enzymes and genes.These results will be useful for SRF application to high-quality lotus rhizome production with low environmental costs.

未来淀粉——淀粉资源的挑战与思考

淀粉是人类活动的主要能量来源和重要的工业原辅料。然而,传统淀粉来源的植物受种植环境影响较大,土地资源有限,产量增长困难,满足不了人口增长的需要;另一方面,传统植物来源的淀粉,其结构相对固定、性能存在局限性,不能完全满足应用的需求,往往要通过结构修饰来调控其性能。化学方法是常用的结构修饰和性能调控手段,但化学反应过程带来的试剂用量受限、化工辅料残留、副产物的产生和淀粉分子中新化学基团的引入等问题,使其作为食品添加剂的使用存在安全隐患。因此,传统淀粉资源已经不能够完全满足人类可持续发展的要求,有必要开发具有“未来特点”的淀粉新资源。未来淀粉来源根据其特点可分为三类:一是将传统淀粉来源植物通过遗传育种或者基因编辑改造,实现淀粉结构的定向或定点改造,使淀粉具有特殊的应用性能;二是能够克服土地和自然环境限制、或者富含淀粉而尚未被充分开发利用的新淀粉资源等;三是不以植物和微生物为载体合成的无细胞合成新型淀粉。本文阐述了未来淀粉发展的必要性、可行性和发展趋势,以高直链淀粉、蜡质淀粉、浮萍淀粉、微藻淀粉、CO_(2)合成淀粉和多糖生物合成淀粉等为例,重点介绍了三类未来淀粉的研究现状和特点,将对未来淀粉的开发研究具有指导意义。

不同温度对羊肚菌淀粉代谢的调控研究

研究了不同温度对淀粉培养基中羊肚菌菌丝生长、淀粉酶活[腺苷二磷酸葡萄糖焦磷酸化酶(AGPase)、α-淀粉酶、β-淀粉酶、淀粉分支酶(DBE)、淀粉脱分支酶(SBE)]、淀粉含量(直链淀粉、支链淀粉)和淀粉相关酶基因表达的影响。结果表明:在10—25℃温度条件下,随着温度的增加,淀粉培养基上菌丝生长速度加快,菌丝浓密度和菌丝尖端分叉增加;AGPase、DBE、α-淀粉酶、β-淀粉酶在20℃下活性最高,SBE则在10℃下活性最高。直链淀粉含量和支链淀粉剩余含量在10℃下最高。相关性分析结果显示,温度与α-淀粉酶活性和SBE活性相关性不显著,与β-淀粉酶活性、AGPase活性、DBE活性呈显著负相关,与直链淀粉含量和支链淀粉含量呈极显著负相关。综上,在15—20℃温度条件下,羊肚菌对培养基中的淀粉代谢能力最强,10℃低温或者25℃高温都不利于羊肚菌对培养基质中淀粉的利用。研究可为羊肚菌的菌种制作和人工种植提供理论支撑。

不同磷酸二氢钾喷施量对水稻淀粉合成及相关基因的影响

【目的】研究在相同栽培条件下不同磷酸二氢钾喷施量对水稻淀粉合成及相关基因的影响。【方法】以3种不同直链淀粉含量的水稻品种作为试验材料,采用两因素裂区设计,4种磷酸二氢钾喷施水平处理,取开花后10 d颖果,提取RNA并分析GBSSⅠ、BEⅡb、BEⅠ、SSⅡa及SSⅢa基因的表达量,待籽粒完全成熟后,检测供试水稻精米及糙米的总淀粉含量、总蛋白含量和总脂质含量,以及供试水稻精米的直链淀粉含量和抗性淀粉含量。【结果】对直链和抗性淀粉分析,磷酸二氢钾处理对琥珀一号可显著提高精米直链淀粉含量和抗性淀粉含量,分别提高了22.43%和95.01%;在琥珀二号和糯优一号中降低直链淀粉含量,但提高抗性淀粉含量,直链淀粉分别降低6.75%和64.24%,抗性淀粉分别提高55.63%和43.07%。进一步对淀粉合成通路关键基因表达分析,磷酸二氢钾影响GBSSⅠ、BEⅡb、BEⅠ、SSⅡa及SSⅢa基因表达,且在3个供试水稻品种籽粒中均呈现先增加后降低趋势。对脂质和蛋白含量分析,随磷酸二氢钾浓度的升高,3个供试水稻品种精米及糙米的脂质含量均逐渐增加,精米中各品种相对于CK分别提高了72.64%、24.24%和4.71%,糙米中各品种脂质含量相对于CK分别提高了25.88%、17.20%和7.81%。相反,在精米中琥珀一号及琥珀二号总蛋白含量比CK分别降低了19.71%和22.15%,而糯优一号材料的蛋白质含量影响不同于其他2个品种,变化呈现波动性,在糙米中,琥珀一号及糯优一号蛋白质含量变化趋势与精米一致,琥珀二号材料的蛋白质含量变化与精米不同,呈现升高状态,最高比CK增加了30.30%。【结论】喷施磷酸二氢钾能够在一定程度上提高稻米精米的抗性淀粉含量以及淀粉合成通路关键基因的表达量,对水稻直链淀粉合成具有一定的品种特异性,能够提高稻米中精米及糙米的脂质含量,但降低精米蛋白质含量。根据不同喷施量对比,喷施磷酸二氢钾20 g/hm^(2)有利于水稻生长发育,改善稻米品质。

水稻糯性突变体r162的鉴定与基因定位

直链淀粉是影响稻米食味品质和外观品质的重要因素,主要由Waxy(Wx)基因编码的颗粒结合淀粉合酶Ⅰ(granule-bound starch synthaseⅠ, GBSSⅠ)介导合成。本研究从宁粳2号的甲基磺酸乙酯(ethyl methanesulfonate,EMS)诱变材料中筛选到了一个糯性突变体r162,与野生型相比,其籽粒外观呈不透明的云雾状,种子和糙米的粒长、粒宽以及千粒重显著下降。通过扫描电镜对淀粉形态进行观察,发现突变体的淀粉颗粒上存在孔洞。半薄切片碘染结果表明,突变体r162发育时期胚乳的造粉体排列结构与野生型相似,但碘染后颜色更浅。理化性质分析发现,突变体r162的总淀粉、总蛋白质和总脂肪含量与野生型相比无显著差异,但是表观直链淀粉含量极显著下降、胶稠度极显著增加,糊化特性发生明显改变,并且淀粉的崩解值、回生值、回复值以及米粉在尿素中的膨胀体积均小于野生型。通过基因定位和测序发现,突变基因Wx位于第6号染色体短臂上,Wx基因第7个内含子的第1个碱基(Int7-1)由鸟嘌呤(G)替换为腺嘌呤(A),造成Wx基因的编码区存在10个碱基的缺失,导致其编码的GBSSⅠ蛋白自第256位氨基酸起出现错误翻译,使蛋白质翻译提前终止,因此将该等位变异命名为Wx-r162。进一步通过蛋白质印迹法检测发现,突变体中的GBSSⅠ蛋白水平极显著下降。酶活性测定也证实,突变体r162中GBSSⅠ活性明显降低。综上所述,Wx-r162基因被视为一个新的等位变异,这种突变导致GBSSⅠ活性下降,进而造成突变体r162表观直链淀粉含量降低和籽粒表现出不透明的表型。

冬小麦淀粉糊化性状的全基因组关联分析

【目的】淀粉是小麦籽粒的主要成分,在加工过程中起着重要作用。而淀粉的糊化特性则是评估其品质的重要指标。深入研究淀粉糊化特性的遗传变异,为提升小麦的品质提供依据。【方法】通过对205份冬小麦品种(系)的糊化温度、峰值时间、峰值黏度、低谷黏度、最终黏度、衰减值和回生值7个淀粉糊化性状进行表型测定,利用90K芯片进行全基因组关联分析,并对挖掘出的稳定且显著的位点进行单倍型分析。【结果】糊化温度等7个性状在不同环境间均表现出丰富的变异,衰减值的变异系数最大(29.31%—31.14%)。各性状在基因型、环境、基因型×环境间均呈现出极显著差异,广义遗传力为0.69—0.86。通过全基因组关联分析,共发现198个位点,这些位点与7个性状呈现出显著的关联,分布在除6D染色体外的其他20个连锁群。在2个及2个以上的环境中均稳定存在的位点有58个,涉及糊化温度(10个)、峰值时间(5个)、峰值黏度(12个)、低谷黏度(10个)、最终黏度(7个)、衰减值(4个)和回生值(10个)等所有7个性状,能解释遗传变异的5.54%—22.21%,发现新位点有21个。通过对多环境下存在且表型贡献率高的多效应位点进行单倍型分析,位于4A染色体的Kukri_c17417_407位点发掘到与峰值黏度和衰减值等性状显著相关的Hap1(占比66.84%)、Hap2(16.84%)、Hap3(9.70%)和Hap4(6.63%)等4个单倍型,其中,Hap2是高峰值黏度和高衰减值单倍型(P<0.0001)。含有单倍型Hap2的品种(系)在不同生态区中分布频率由高到低为黄淮冬麦区>国外品种>西南冬麦区>长江中下游冬麦区>北部冬麦区。有11个位点为一因多效位点,其中,最终黏度、回生值、峰值时间和低谷黏度等性状相关联的多效应位点均有3个。对位于1B、2A、3A、3B、4A、4B、5B和6B上的Jagger_c4026_328等11个稳定遗传的位点进行候选基因的挖掘,筛选到11个可能与小麦淀粉糊化性状相关的候选基因。【结论】RVA参数具有较高的遗传力,不同环境间的小麦淀粉RVA参数均表现较大差异。检测到58个与淀粉糊化性状显著关联的稳定位点,在4A染色体鉴定到与峰值黏度和衰减值等性状显著相关的4个不同单倍型,筛选出11个与淀粉糊化相关的候选基因,可为分子标记辅助优质小麦育种提供帮助。