Milling Characteristics of Rice Cultivars and Hybrids

Many rice cultivars and hybrids have unique physical characteristics that affect milling performance. The purpose of this study was to quantify the rate of bran removal during milling for several rice cultivars and hybrids common to the southern United States, and compare the quantity of lipids remaining on the kernel surface to that located throughout the kernel. This was accomplished by analyzing two sample sets. The first comprised cultivars Cocodrie, Cypress, and Lemont, and hybrids XL7 and XL8, which were milled for 0 (brown rice), 20, 30, 40, 50, 60, and 70 sec in a laboratory mill. In the second set, cultivars Cocodrie, Cypress, and Wells, and hybrids XL7 and XL8 were milled for 0, 20, 40, and 60 sec. The surface lipid content (SLC) and color of head rice samples were measured as indications of the degree of milling (DOM). The total lipid content (TLC) of ground head rice was also measured to determine the total amount of lipids present throughout the entire kernel. Results showed that at a given milling duration, SLC and color varied across cultivars and hybrids. In particular, the SLC levels of hybrids were lower than those of cultivars, particularly for Cocodrie, for all milling durations. This research indicated that it may be necessary to mill different cultivars and hybrids for varying durations to attain comparable DOM levels. Milling to a consistent DOM level is necessary to ensure equitable head rice yield comparisons across cultivars and hybrids.     

Genetic and Environmental Effects on Dough Mixing Characteristics and Agronomic Performance of Diverse Hard Red Winter Wheat Genotypes

Wheat (Triticum aestivum L.) genotypes with short mixing times usually have low mixing tolerance values, which make them more sensitive to overmixing in commercial bread production. In this study, we evaluated the genotypic and environmental effects on agronomic performance and end‐use quality of 27 experimental genotypes (hereafter referred to as mixing tolerant genotypes) which were identified in an initial screen as having short mixing times and good mixing tolerances to 1) determine whether genotypes identified in a preliminary end‐use quality screen as lines with usually long tolerances but short mixing times were due to their genotype (G), the environment (E), or G × E; and as these results were unusual, 2) determine whether or not our initial screen predicts end‐use quality, and 3) determine the stability of both agronomic and end‐use quality traits. The 27 genotypes and five check cultivars were grown in a randomized complete block design with two replicates in nine environments in 1997 and 1998. All plots were harvested for grain yield. The harvested grain from the first replicate and random genotypes from the second replicate were micromilled to produce flour samples for evaluation of flour yield, protein content, and mixograph mixing time and mixing tolerance values. Seed diameter, thousand kernel weight, and kernel hardness were also measured in three environments. Environment, G, and G × E interaction effects (mainly changes in magnitude) were significant for most agronomic and end‐use quality parameters. Our initial screen, which had identified 27 genotypes, was partially effective in identifying genotypes that have shorter mixing time values compared with their mixing tolerance values. We identified four genotypes (15%) from the mixing tolerant genotypes that had a good mixing tolerance value and relatively shorter mixing time, as did the released cultivars ‘Agate’ and ‘Scout 66’. However, mixing characteristics values of all genotypes fell within the acceptable limits, indicating our screen effectively identified genotypes with acceptable quality. Mixing tolerant genotypes, which had been identified as having short mixing time scores and long mixing tolerance scores, were considered stable across environments.     

Baking Characteristics of Chiffon Cake as Influenced by Microbial Transglutaminase

Protein modification via covalent bonds by using microbial transglutaminase (TGase) has generated many processing functionality improvements in specific food ingredients. In this study, TGase was added into different cake portions (foam and yolk batter) at levels of 0, 0.5, and 1.0% (w/w, total protein weight basis). The treatment of 0.5% TGase in the yolk batter portion significantly (P ≤ 0.05) increased its emulsion activity. The addition of 1.0% TGase in the yolk batter portion significantly increased both foam stability and emulsion activity of cake batter, whereas the addition in the foam portion only increased the emulsion activity of cake batter significantly (P ≤ 0.05). As the addition of TGase, in foam or in the yolk batter portion, rose from 0 to 1.0%, the specific volume of chiffon cake increased. Cakes with 1.0% TGase in the foam portion had the maximum specific volume, 7.078 mL/g, and the softest texture. SDS‐PAGE was used to analyze the modifications of TGase to the protein fractions from different cake portions. The effect of TGase on protein fractions from the yolk batter portion was more evident than that on protein fractions from the foam portion. However, there was no significant difference between the protein fractions of cake batters with the same level of TGase in the foam and yolk portions, which suggested that the main substrates of TGase were yolk protein and wheat protein, instead of egg white protein.     

还原型谷胱苷肽(GSH)作用下土壤磷酸酶动力学特性研究

采用室内培养方法研究还原型谷胱苷肽(GSH)对黑土和棕壤磷酸酶动力学特性的影响。结果显示480mgkg-1(以风干土重计)的GSH处理的黑土磷酸单酯酶、三酯酶和棕壤的二酯酶、三酯酶Vmax值显著大于对照,证明GSH是通过增大酶量实现Vmax值的增大。试验中GSH处理的棕壤磷酸单酯酶及黑土的磷酸二酯酶Km值显著低于对照,说明GSH改变了酶结构,增强了酶与底物的亲和力。     

Strontium Absorption by Two Trifolium Species as Influenced by Soil Characteristics and Liming

Strontium absorption by plants is specific to individual species and also depends on the underlying soil properties. The purpose ofthis study was to evaluate the effect of certain soil characteristics and liming on Sr absorption by twoTrifolium species. One-liter volume of two inorganic and three organic soilswere treated with a combination of three CaCO₃ levels, 0, 3.6 and 7.2 g, × two Sr levels, 50 and 100 mg, (treatments) in four replications. Trifolium repens L. was grown in thetreated soils, in pots, harvested twice, and Sr in theabove-ground biomass of each harvest and soil exchangeable Caof each treatment were determined. The experiment was repeatedwith Trifolium subterraneum L., harvested once. For bothspecies, Sr transfer factor (T.F.) values of the varioustreatments were calculated. Shoot Sr concentrations weresignificantly affected by soil characteristics and Sr additionrates and were greater in T. repens. In all cases, theSr concentrations of plants grown in the organic soils, whichwere characterized by higher exchangeable Ca and cationexchange capacity (C.E.C.) values, were lower than those ofplants grown in the inorganic soils. Among the organic soils,Sr concentrations of the plants grown in the soil with thehighest values of C.E.C., organic matter and exchangeable Cawere the lowest. Liming decreased significantly the Srconcentrations in T. repens and T. subterraneumgrown in the two acid soils, while the pH and exchangeable Cawere increased. Shoot Sr concentration (log scale) wassignificantly, negatively correlated with soil exchangeable Ca. Strontium T.F. values were quite similar between the two Sr application rates and were affected by the same soil characteristics.     

Differences in Carbohydrate Composition and Digestion In Vitro of Selected Barley Cultivars as Influenced by Pearling and Cooking

Among common cereals, barley is a low glycemic index food. In an attempt to better understand this character, the nutritional properties of glycemic carbohydrates and dietary fiber concentrations of nine cultivars were evaluated. The cultivars were selected based on botanical variations and commercial value to investigate the impact of pearling and cooking on nutritional properties. Each cultivar was pearled into four fractions ranging from hull removal only to hull, bran, germ, and crease removal. The study showed that botanical class and degree of pearling significantly affect the carbohydrate composition and digestion indices of barley. Waxy starch cultivars had less total starch and more rapidly digestible starch (RDS), rapidly available glucose (RAG), and β‐glucan than the other nonwaxy cultivars. Regardless of the barley type, the less pearled kernels had significantly lower total starch and higher total low molecular weight sugars, insoluble, and total fiber. However, β‐glucan content was fairly comparable in the whole grain and pearled fractions. Cooking had a significant effect on nutritional properties of Celebrity and AC Klinck cultivars. The only consistent significant difference between raw and cooked barley was resistant starch (RS), which increased after cooking regardless of cultivar or fraction. The study showed that barley cultivar and carbohydrate composition significantly affected starch digestion with some cultivar fractions holding a promise for the development of low glycemic index foods.     

Genetic Variation and Association Mapping of Protein Concentration in Brown Rice Using a Diverse Rice Germplasm Collection

Protein is the second most abundant constituent in the rice grain next to starch. Association analysis for protein concentration in brown rice was performed using a “mini‐core” collection, which represents the germplasm diversity found in the USDA rice world collection. Protein concentration was determined in replicated trials conducted in two southern U.S. locations, and association mapping was performed by using 157 genomewide DNA markers. Protein concentration ranged from 5.4 to 11.9% among the 202 accessions. Protein variation owing to accession and accession × location interaction were highly significant. Ample variation was seen within each subpopulation by ancestry, as well as within the 14 geographic regions where the accessions originated. Accessions from Eastern Europe had the highest level of protein. Ten markers on eight chromosomes were significantly associated with protein concentration. Five of these markers occurred near known protein precursor genes or quantitative trait loci, and the other five markers were novel for the association with protein concentration in rice. The germplasm and genetic markers identified in this study will assist breeders in developing cultivars tailored for applications requiring specific protein concentration in the rice grain. The research results contribute to the potential discovery of novel rice storage protein pathways in the endosperm.     

Categorizing Rice Cultivars Based on Cluster Analysis of Amylose Content,Protein Content and Sensory Attributes

Presently, rice cultivars are categorized according to grain dimensions, amylose content, and alkali spreading value (gelatinization temperature type). Categorization of rice cultivars based on total sensory impact is needed. This work endeavors to divide world rices into groups based on amylose, protein, flavor, and texture properties. Ninety‐one rice samples representing 79 different cultivars and seven growing locations were separated into seven groups with Ward's Cluster Analysis. Cluster 1 included a third of the rice samples and had cultivars with a large diversity of grain shapes and amylose contents. Mean attribute scores for this cluster were near the grand mean for the collective rice samples for nearly every sensory attribute. Cluster 2 included conventional U.S. short‐ and medium‐grain cultivars. Cluster 3 included conventional U.S. medium cultivars that were produced in Louisiana. Mean sensory scores for this cluster characterized these cultivars as having relatively undesirable flavor and texture attributes. Cluster 4 included Japanese premium quality cultivars and U.S. medium‐grain cultivars developed for the Japanese market. Cluster 5 included high‐amylose, indica types that had relatively firm textural properties. Cluster 6 included relatively soft cooking, aromatic cultivars. Cluster 7 included waxy cultivars and other soft cooking grains. In several cases, the production environment (location, weather effects, etc.) influenced flavor and texture characteristics and resulted in the cultivar falling into an unexpected cluster. This categorization serves as a catalyst for indexing rice cultivars for cooking and processing qualities.     

Nitrate Reductase,Micronutrients and Upland Rice Development as Influenced by Soil pH and Nitrogen Sources

The average yield of upland rice under no-tillage system (NTS), a sustainable soil management, is lower than in conventional tillage (one plowing and two disking). One of the reasons given for this drop in crop grain yield would be the low-nitrate assimilation capacity of rice seedlings, due to the low activity of the nitrate reductase (NR) enzyme in the early development phase. A greenhouse experiment was conducted to evaluate the effects of the soil acidic and nitrogen source in the micronutrient concentrations, NR activity and grain yield of upland rice growing under NTS. The soil used in the experiment was an Oxisol. The experimental design was completely randomized in a factorial 3 × 4. Treatments consisted of three levels of soil acidity (high, medium, and low) combined with four nitrogen sources (nitrate, ammonium, ammonium + nitrification inhibitor, and control – without N fertilization). The reduction of soil acidity reduced the concentration of zinc and manganese in rice plants. Generally, the activity of the NR enzyme was higher in plants grown in soils with low acidity and fertilized with calcium nitrate. There was a greater response in growth and yield in rice plants grown in soils with high acidity. Under medium acidity, rice plants grown with ammonium sulfate were more productive (no differences were detected with the addition of the nitrification inhibitor).     

Wet-Milling Characteristics of Selected Yellow Dent Corn Hybrids as Influenced by Storage Conditions

Three yellow dent corn hybrids (FR1064×LH59, FR600×FR1087, and FR618×LH123HT) from the 1994 crop, one hybrid (FR1064×LH59) from the 1995 crop, and two hybrids (FR1064×LH59 and FR618×LH123HT) from the 1996 crop were used to study the effect of storage time and storage temperature on starch yields. Samples of all of the corn hybrids were stored under one of two conditions: in a 4°C cold room or under a shed exposed to ambient conditions. The hybrids from the 1994, 1995, and 1996 crops were stored for up to 24, 12, and 3 months, respectively. No significant differences were found between starch yields of the hybrids with respect to storage time. However, there was a significant difference in hybrids from the 1994 samples. Starch yields of two of the three corn hybrids (from the 1994 crop) stored in the 4°C cold room were higher when compared to the starch yields of the same hybrids stored at ambient conditions.     

稻米蒸煮特性QTL定位及与感官食味品质的相关性分析

稻米蒸煮特性和感官食味品质是稻米品质的重要评价指标,其遗传复杂.为挖掘与利用优异的稻米品质基因,本研究利用籼稻昌恢121为受体亲本和优质粳稻越光为供体亲本构建的一套染色体片段置换系(CSSL),对稻米的吸水率(WA)、延伸率(CRE)和膨胀率(VE)3个蒸煮特性进行QTL定位.共检测到4个QTL,分布于第8和第11号染...     

硒高/低累积型水稻富硒特征的比较研究

通过盆栽试验分析硒高、低累积型水稻植株硒的吸收和分配规律、糙米中有机硒的累积特点及土壤有效硒的变化。结果表明:两个水稻品种各部分硒的分配规律完全一致,均为根茎叶糙米稻壳。水稻各部分的含硒量及糙米有机硒的含量均随土壤施硒水平增加而升高,且高累积水稻的含硒量显著高于低累积水稻(P0.05),在0、0.5、1.0和5.0 mg kg-1施硒水平下,前者分别为后者的6.7、1.9、2.1和1.6倍。糙米中有机硒的比例为64.7%~74.4%,不过,高、低累积型水稻糙米有机硒占全硒的比例之间并无显著性差异(P0.05)。土壤总硒及有效硒的含量随施硒量的增加也表现出逐步升高的趋势,但高、低累积型水稻土壤有效硒的比例均在5.5%~7.4%范围内,且两者之间无明显差异(P0.05)。除水稻基因型外,土壤有效硒的比例对水稻籽粒有机硒的累积也有一定影响。     

Rhizosphere pH Profile of Rice Plant Influenced by Al Treatment

To study the mechanisms of Al tolerance in rice, we focused on the change of rhizosphere pH. The 4-d seedlings were treated with Al solution (0, 10, 50 mM) for 24 h. Then each sample was put on an agarose gel including bromocresol green, so that the color of the gel indicated pH change. During 2-h contact, the pH of rhizosphere was decreased gradually, especially for Al-treated samples, showing the specific pH profiles along the root axis. Pretreatment of sample plants with a decoupling reagent 2,4-dinitrophenol (DNP) or a plasma membrane H⁺-ATPase inhibitor Na₃VO₄ did not decrease rhizosphere pH. Therefore, it was suggested that the H⁺ secretion activity was involved with Al-tolerant mechanisms of rice.     

两个水稻品种富硒特性比较研究

以前期田间试验筛选出的富硒能力较强的水稻品种捷丰优629和谷丰优8312为材料,采集硒含量不同的稻田土壤,通过盆栽试验进一步研究了两个水稻品种对土壤硒的吸收、分配及其糙米和精米中无机硒与有机硒含量的组成特点。结果表明:两个水稻品种植株的硒累积量、糙米和精米的硒含量与有机硒含量都是高硒土壤极显著高于低硒土壤,表明高硒土壤有利于稻米硒的累积与有机硒的合成,因此生产优质富硒大米最好选择硒含量较高的稻田土壤。无论在高硒土壤还是低硒土壤上,捷丰优629植株中硒累积量和籽粒中硒累积量与谷丰优8312的差异都不显著,但捷丰优629的糙米和精米中硒含量以及有机硒含量都极显著高于谷丰优8312,表明捷丰优629吸收的硒易分配到可食用部位(糙米和精米),而且其无机硒向有机硒的转化能力较强,因此综合比较来看捷丰优629富硒特性优于谷丰优8312。     

Soil Boron Migration as Influenced by Leaching Rate and Soil Characteristics: A Column Study

ABSTRACT

Soil boron (B) supply is usually used by farmers to correct B deficiency in many crops. The excessive application of this fertilizer may threaten environment components particularly underground water and soil. This study was undertaken to evaluate B migration at different soil characteristics and leaching levels. Three soils were collected from different southwestern Mediterranean areas. Then, three annual leaching rates were tested for each soil: 35 mm, 237 mm, and 565 mm in a sandy soil; 35 mm, 103 mm, and 247 mm in a silty-clay soil; 35 mm, 70 mm, and 140 mm in a clay-calcareous soil. The experiments were conducted in PVC columns filled with 30 cm of the studied soils. 0.5 mg kg^?1 of B was applied to the surface of each soil. The results showed that B migration is mainly related to leaching rate and clay content. The soil B losses (y) can be predicted using the regression model: y (mg kg^?1) = 0.001a–0.01b+0.14 (adjusted R² = 0.92) where a = leaching rates (mm) and b = soil clay content (%). The B leaching threat is higher on sandy soil compared to other soils. However, soil B accumulation risk seems to occur particularly in silty-clay and clay-calcareous soils. Further, bioavailable B enrichment was recorded only on silty-clay soil.