Starch Characteristics of Waxy and Nonwaxy Tetraploid (Triticum turgidum L. var. durum) Wheats

Manufacture of pasta products is paramount for durum wheat (Triticum turgidum L. var. durum). The recent development of waxy durum wheat containing starch with essentially 100% amylopectin may provide new food processing applications and present opportunities for value‐added crop production. This investigation was conducted to determine differences in some chemical and functional properties of waxy durum starch. Starch was isolated from two waxy endosperm lines and four nonwaxy cultivars of durum wheat. One of the waxy lines (WX‐1) was a full waxy durum wheat whereas the other line (WX‐0) was heterogeneous, producing both waxy and nonwaxy seed. Effects on starch swelling, solubility, pasting, gelatinization, and retrogradation were examined. The full waxy starch had four times more swelling power than the nonwaxy durum starches at 95°C, and was also more soluble at three of the four temperatures used. Starch pasting occurred earlier and peak viscosities were greater for starches from both waxy lines than for the nonwaxy starches, but their slurries were less stable with continued stirring and heating. Greater energy was required to melt gelatinized waxy starch gels, but no differences were found in either refrigerated storage or freeze‐thaw retrogradation, as determined by differential scanning calorimetry. The results of this investigation showed some significant differences in the starch properties of the waxy durum wheat lines compared to the nonwaxy durum wheats.     

Genetic Diversity of Glutenin Protein Subunits Composition in Durum Wheat Landraces [Triticum turgidum ssp. turgidum Convar. durum (Desf.) MacKey] from the Mediterranean Basin

The genetic diversity of high and low molecular weight glutenin subunits of 63 durum wheat landraces from different geographical regions in the Mediterranean Basin was studied using SDS-PAGE. Great variability in glutenin composition was found, with 42 high and low molecular weight glutenin haplotypes, 20 allele combinations at the HMW-GS loci, and 18 at the LMW-GS. All five possible LMW models were detected in all Mediterranean regions. Rare alleles were found at Glu-B1 locus in high frequencies and a priori related alleles to grain quality were also observed. Global genetic diversity index was relatively high (0.67); it ranged from 0.33 to 0.66. Cluster analysis on the frequency patterns of origins grouped genotypes following a geographical structure. Rogers’ distance coefficient on frequency pattern for each region of origin showed two germplasm pools with distinct quality profiles, where South West Asian landraces were very different from the landraces of other Mediterranean areas. The relationship between different regions of origin is discussed and two possible ways of introduction of wheat in the Iberian Peninsula (N Africa and SE Europe) are hypothesized. The use of Mediterranean durum wheat landraces as source of genetic variability for grain quality improvement is highly recommended.     

Physicochemical and Thermal Characteristics of Starch Isolated from a Waxy Wheat Genotype Exhibiting Partial Expression of Wx Proteins

A unique wheat genotype carrying waxy‐type allelic composition at the Wx loci, Gunji‐1, was developed, and its starch properties were evaluated in comparison to parental waxy and wild‐type wheat varieties. Gunji‐1 was null in all three of the Wx genes but exhibited a lower level of Wx proteins than the wild‐type. Starch amylose content and cold water retention capacity were 10.1 and 70.5% for Gunji‐1, 4.2 and 76.6% for waxy, and 27.9 and 65.0% for wild‐type, respectively. No significant differences were observed in microstructure, granule size distribution, and X‐ray diffractograms of the starch granules isolated from Gunji‐1 compared with those of waxy and wild‐type wheat varieties. Starch pasting peak, breakdown, and setback viscosities and peak temperature of Gunji‐1 were intermediate between waxy and wild‐type wheat. In starch gel hardness, Gunji‐1 (1.1 N) was more similar to waxy wheat (0.5 N) than to the wild‐type variety (17.6 N). Swelling power, swelling volume, paste transmittance during storage, and gelatinization enthalpy of Gunji‐1 were lower than those of waxy wheat but greater than those of wild‐type wheat. Retrogradation of starch stored for one week at 4°C expressed with DSC endothermic enthalpy was absent in the waxy wheat variety, whereas Gunji‐1 exhibited both retrogradation of amylopectin and amylose‐lipid complex melting similar to the wild‐type parent, even though enthalpies of Gunji‐1 were much smaller than the wild‐type parent.     

Impact of Waxy,Partial Waxy,and Wildtype Wheat Starch Fraction Properties on Hearth Bread Characteristics

Thirteen different wheat cultivars were selected to represent GBSS mutations: three each of wildtype, axnull, and bxnull, and two each of 2xnull and waxy. Starch and A‐ and B‐granules were purified from wheat flour. Hearth bread loaves were produced from the flours using a small‐scale baking method. A‐granules purified from wildtype and partial waxy (axnull, bxnull, and 2xnull) starches have significantly higher gelatinization enthalpy and peak viscosity compared with B‐granules. A‐ and B‐granules from waxy starch do not differ in gelatinization, pasting, and gelation properties. A‐ and B‐granules from waxy starch have the highest enthalpy, peak temperature, peak viscosity, breakdown, and lowest pasting peak time and pasting temperature compared with A‐ and B‐granules from partial waxy and wildtype starch. Waxy wheat flour has much higher water absorption compared with partial waxy and wildtype flour. No significant difference in hearth bread baking performance was observed between wildype and partial waxy wheat flour. Waxy wheat flour produced hearth bread with significantly lower form ratio, weight, a more open pore structure, and a bad overall appearance. Baking with waxy, partial waxy, and wildtype wheat flour had no significant effect on loaf volume.     

小麦品种Waxy蛋白的鉴定和筛选

鉴定了“中国春”小麦及有关染色体缺体－四体系,中国地方小麦品种“白火麦”及国内外４００多种品种（系）的Ｗａｘｙ蛋白亚基类型,并从中筛选出４３份不同的Ｗａｘｙ蛋白亚基缺失类型材料,特别是筛选出３份Ｗｘ－Ｄ１亚基缺失类型材料;分析了二倍体小麦,四倍体小麦和原始六倍体小麦的Ｗａｘｙ蛋白带型,进一步明确了在小麦的进化过程中,染色体４ＡＬ上的片段曾与７ＢＳ发生过相互易位,使原来在７ＢＳ上的荷载有Ｗｘ－Ｂ１基     

Composition and Reactivity of A‐ and B‐type Starch Granules of Normal,Partial Waxy,and Waxy Wheat

Wheat has great potential to make inroads into starch markets with the advent of partial waxy and waxy starches of diverse composition and properties. The majority of isolated starch utilized in food applications is chemically modified to improve starch properties according to the intended use. Therefore, it is critical to understand factors that affect wheat starch reactivity. This work investigated the relative reactivities of normal, partial waxy, and waxy wheat starches and their respective A‐ and B‐type starch granule fractions. Native starch isolated from four closely related soft wheat lines (normal, partial waxy, and full waxy) was modified through 1) substitution (propylene oxide analog) and 2) cross‐linking (phosphorus oxychloride) reactions to generate both types of modified starch products for each wheat line. Characterization of the unmodified starch fractions confirmed compositional differences among the cultivars and their respective granule types. In cross‐linking reactions, B‐type granules were slightly more reacted than A‐type granules for all cultivars, while the waxy starch generally exhibited higher reactivity compared with normal and partial waxy starches. For the substituted starches, no differences in reactivity were observed among the cultivars or between the two granule types.     

(英文)

对来源于美、中、俄及埃塞阿比亚等22个国家的142份硬粒小麦材料的种子贮藏蛋白位点及遗传变异进行了研究。供试的硬粒小麦(Triticum durum Desf )材料共检测出37条醇溶蛋白条带，无1条带纹为所有材料共有，多态性达到100％，说明硬粒小麦具有丰富的醇溶蛋白等位变异。聚类分析将142份供试材料分为3个大类，材料间遗传差异大小在不同的国家有所不同，表明醇溶蛋白带型与地理来源有一定关系。高分子量谷蛋白电泳共分离出14种亚基和15种亚基组合，但是优质亚基所占比例不高，这可能是因为硬粒小麦加工用途的特殊性，使得多年的育种并未太多改变硬粒小麦高分子量谷蛋白亚基等位变异的频率，促成优质亚基的累计。     

Polymorphism of high M r glutenin subunits in wild emmer Triticum turgidum subsp. dicoccoides: chromatographic,electrophoretic separations and PCR analysis of their encoding genes

Triticum turgidum subsp. dicoccoides (Körn. ex Asch. et Graebn.) Thell. (AABB), the immediate progenitor of tetraploid and hexaploid wheats, is a species characterised by a wide range of protein polymorphism and by high protein content. Surveys on polymorphism and genetic control of the high molecular weight glutenin subunits (HMW-GS) present in this species, in two forms x- and y-type at the Glu-A1 and Glu-B1 loci, are still considered useful, both to improve technological properties of breeding varieties and to study the genome evolutionary process in wheats. Comparative Sodium Dodecyl Sulphate Polyacrylamide Gel Electrophoretic and Reversed Phase High Performance Liquid Chromatographic analyses (SDS-PAGE, RP-HPLC) of the HMW-GS present in several accessions of T. turgidum subsp. dicoccoides allowed the detection of new alleles of Glu-A1 and Glu-B1 loci, with x- and y-type glutenin subunits, apparently similar to those present in cultivated wheats in molecular weight, but different in surface hydrophobicity. In addition, changes in the number of x- and y-type subunits at the glutenin loci were also ascertained. The y-type subunits at the Glu-A1 locus, which are never expressed in cultivated bread and durum wheats, and single y-type expressed glutenin subunits at the Glu-B1 locus were also identified in several accessions. DNA extracted from samples, differing in number or type of HMW-GS and corresponding to x- and y-type genes at Glu-1 loci, were amplified using specific primers, two of which were constructed within the transposon-like sequence of Chinese Spring DNA and analysed by polymerase chain reaction. The results showed this insertion in some accessions of T. turgidum subsp. dicoccoides and also the presence of silent Ax, Bx and By type genes. The usefulness for breeding of these comparative analyses carried out on different HMW-GS alleles detected in Triticum turgidum subsp. dicoccoides, is discussed.     

In Vitro Polymerization of Wheat Glutenin Subunits with Inorganic Oxidizing Agents. I. Comparison of Single‐Step and Stepwise Oxidations of High Molecular Weight Glutenin Subunits

High molecular weight glutenin subunits (HMW‐GS) were isolated from wheat flour and polymerized in vitro at pH 3.0 with different oxidizing agents (KBrO₃, KIO₃, H₂O₂). An oxidation protocol with single addition of oxidant (single‐step oxidation) was compared with a set‐up in which the oxidant was added in multiple steps (stepwise oxidation). Changes in size distribution were evaluated with size‐exclusion HPLC, multilayer SDS‐PAGE, and flow‐field flow fractionation (flow‐FFF). Flow‐FFF is particularly suitable for measuring changes in glutenin size in the very high size ranges. In order of increasing sizes of the resulting polymers, the different oxidizing agents could be ranked as KBrO₃ < KIO₃ < H₂O₂. However, none of the oxidation conditions allowed for a complete polymerization of HMW‐GS. Interestingly, it was found that high concentrations of KIO₃ negatively affect the degree of polymerization. A similar observation was not made with KBrO₃ or H₂O₂. SDS‐PAGE showed that y‐type HMW‐GS particularly failed to incorporate in glutenin polymers. Simultaneously, these HMW‐GS displayed higher mobilities on SDS‐PAGE that can be ascribed to the formation of intrachain SS bonds. Possible explanations for the incomplete polymerization of HMW‐GS are given.