bluuebunny/crossref_metadata_2025 huggingface dataset:
Streamline-Based Simulation of Non-Newtonian Polymer Flooding
Authors: AlSofi Abdulkareem M. , Blunt Martin J.
Published: August 2010

Current commercial simulators for polymer flooding often make physical assumptions that are not consistent with available experimental data and pore-scale modeling predictions. This may lead to overly optimistic recovery predictions for shear-thinning polymers, while the potential advantages of reducing flow rate or using shearthickening agents are overlooked.

We develop a streamline-based simulator that overcomes these limitations and demonstrate how it can be used to design polymerflooding projects. The simulator implements an iterative approach to solve the pressure field because the pressure depends on the aqueous-phase viscosity, which, in turn for non-Newtonian fluids, depends on shear stress and, hence, the pressure gradients. This is in contrast to the common approach in commercial simulators where this viscosity/pressure interdependence is ignored, leading to overestimation of sweep efficiency. Furthermore, in the simulator, non-Newtonian viscosities are defined to be cell-centered while current simulators use a face-centered approach, thereby overpredicting viscosities and the stability of the displacing fronts. In addition, we use a physically based rheological model where non-Newtonian viscosities in two-phase flow are taken at actual effective stresses instead of single-phase equivalents.

To validate the simulator, we construct 1D analytical solutions for waterflooding with a non-Newtonian fluid. We then compare our results to those from commercial simulators. We discuss the significance of current assumptions to demonstrate the effect of non-Newtonian behavior on sweep efficiency and recovery.
Structural Surface Uncertainty Modeling and Updating Using the Ensemble Kalman Filter
Authors: Seiler A.. , Aanonsen S.I.. I. , Evensen G.. , Rivenæs J.C.. C.
Published: August 2010

Although typically large uncertainties are associated with reservoir structure, the reservoir geometry is usually fixed to a single interpretation in history-matching workflows, and focus is on the estimation of geological properties such as facies location, porosity, and permeability fields. Structural uncertainties can have significant effects on the bulk reservoir volume, well planning, and predictions of future production.

In this paper, we consider an integrated reservoir-characterization workflow for structural-uncertainty assessment and continuous updating of the structural reservoir model by assimilation of production data. We address some of the challenges linked to structural-surface updating with the ensemble Kalman filter (EnKF).

An ensemble of reservoir models, expressing explicitly the uncertainty resulting from seismic interpretation and time-to-depth conversion, is created. The top and bottom reservoir-horizon uncertainties are considered as a parameter for assisted history matching and are updated by sequential assimilation of production data using the EnKF. To avoid modifications in the grid architecture and thus to ensure a fixed dimension of the state vector, an elastic-grid approach is proposed. The geometry of a base-case simulation grid is deformed to match the realizations of the top and bottom reservoir horizons.

The method is applied to a synthetic example, and promising results are obtained. The result is an ensemble of history-matched structural models with reduced and quantified uncertainty. The updated ensemble of structures provides a more reliable characterization of the reservoir architecture and a better estimate of the field oil in place.
Potential for Polymer Flooding Reservoirs with Viscous Oils
Authors: Seright R.S.. S.
Published: August 2010

This paper examines the potential of polymer flooding to recover viscous oils, especially in reservoirs that preclude the application of thermal methods. A reconsideration of enhanced-oil-recovery (EOR) screening criteria revealed that higher oil prices, modest polymer prices, increased use of horizontal wells, and controlled injection above the formation parting pressure all help considerably to extend the applicability of polymer flooding in reservoirs with viscous oils. Fractional-flow calculations demonstrated that the high mobile-oil saturation, degree of heterogeneity, and relatively free potential for crossflow in our target North Slope reservoirs also promote the potential for polymer flooding. For existing EOR polymers, viscosity increases roughly with the square of polymer concentration—a fact that aids the economics for polymer flooding of viscous oils. A simple benefit analysis suggested that reduced injectivity may be a greater limitation for polymer flooding of viscous oils than the cost of chemicals. For practical conditions during polymer floods, the vertical sweep efficiency using shear-thinning fluids is not expected to be dramatically different from that for Newtonian or shear-thickening fluids. The overall viscosity (resistance factor) of the polymer solution is of far greater relevance than the rheology.
Equivalent Wellblock Radius for Partially Perforated Vertical Wells—Part I: Anisotropic Reservoirs With Uniform Grids
Authors: Dogru Ali H.
Published: August 2010

The well index in a numerical reservoir simulator relates the flow rate to the difference between well flowing pressure and simulator gridblock pressure. The standard method for computing well index, Peaceman's formula (Peaceman 1978), requires an equivalent wellblock radius at which the gridblock pressure is equal to the pressure from an analytical solution for steady-state single-phase flow. Although Peaceman's formula is accurate for fully penetrating vertical wells, it fails to account for the effect of vertical flow in partially penetrating wells.

In this paper, we present a new analytical expression for the equivalent wellblock radius in a homogeneous, anisotropic reservoir with a uniform square grid around the well path. The new equation has the same structure as Peaceman's equation but adds one new parameter to account for partial penetration and for vertical flow. The new formula reduces to Peaceman's formula when the well is fully penetrating. Model simulation study showed that the new method reduced the error in the calculated flow rates from 30% to less than 1% at minimal cost.
A USD 100 Million "Rock": Bitumen in the Deepwater Gulf of Mexico
Authors: Han Gang , Osmond Jerry , Zambonini Michael
Published: August 2010

Bitumen encounters in the deepwater Gulf of Mexico (GOM) are not unusual. In many cases, bitumen presence delayed or prevented reaching programmed total depth and adversely affected rig schedule and development planning. The cost from these events could be as high as USD 100 million. On the basis of a series of laboratory tests that investigate the effect of temperature, pressure, and drilling fluids on bitumen mechanical behaviors, this paper attempts to address four questions: (1) What is bitumen and what are its properties, especially at in-situ conditions (18,000-psi stress and 185°F temperature); (2) where is it found, in pore space or fracture; (3) what are the shapes of the in-situ accumulation; and (4) what drives it into the borehole? It has been found that the bitumen encountered at various depths may be significantly different. The bitumen adjacent to salt formation is likely to be stable and could accumulate in a large horizontal spread. The bitumen at the greater depth has to be close to vertical to survive in-situ stresses. For the horizontal bitumen spread, there is a potential to successfully drill through with a liner, and manipulating mud weight may also help. However, for the vertical-column bitumen, increasing mud weight may not be efficient, and sidetracking to avoid further encounter may be more practical. These findings are consistent with the drilling experience in the field and may help to develop a strategy to manage future bitumen encounters in the deepwater GOM.
Assessment of CO2 Storage in DF1-1 Gas Field South China Sea for a CCS Demonstration
Authors: Zhang Liang , Niu Baolun , Ren Shaoran , Zhang Yin , Yi Ping , Mi Honggang , Ma Yongxin
Published: August 2010

DF1-1 gas field is located in the west of the South China Sea, which is associated with high concentration of CO2. Currently CO2 separated from the natural gas stream is emitted into the atmosphere. In this study, a demonstration project of CO2 capture and storage (CCS) is considered, proposing to inject CO2 separated on the platform back into the original gas reservoir. The CO2 storage site considered is a nearly abandoned gas block in the DF1-1 gas field, which was reassessed for the safety of CO2 storage. Membrane separation technique will be installed on the platform for the separation. CO2 is compressed at a super-critical state and injected through a single well (used to be a producer) into the gas formation. A new platform auxiliary to the main platform will be built to accommodate the compressor and separation equipment. CO2 will be injected at the rate of 0.14 million Sm ³ for 10 years over the field development period. At the end of the project, the pressure of the CO2 storage reservoir will be increased to its original pressure. Scoping economic analysis shows that the CO2 storage cost of the project is around US$20 per ton CO2, in which the auxiliary platform is the main cost factor.
Analysis of the Storage Capacity for CO2 Sequestration of a Depleted Gas Condensate Reservoir and a Saline Aquifer
Authors: Barrufet Maria A. , Bacquet Alexandre , Falcone Gioia
Published: August 2010

Among the three types of geological CO2 sequestration (mature oil and gas fields, unminable coalbeds and deep saline formations), depleted gas condensate reservoirs are particularly interesting. First, because of the high-compressibility of gas, these reservoirs have larger storage capacity than oil reservoirs or aquifers. Second, the condensate that has dropped out from the gas phase during natural depletion will re-vaporize because of re-pressurization of the reservoir and by miscibility with the injected CO2. This condensate can be recovered from producing wells and leaves more pore volume for available storage of CO2.

The objective of this study is to investigate the CO2 storage capacity in different formation types, for different levels of CO2 purity and different injection schedules. To this aim, we analyzed the injection of a CO2-based stream into a depleted gas condensate reservoir and into a saline aquifer using a compositional reservoir simulation model.

The dynamics of the reservoir impose a minimum period of injection that is required in order for the storage scheme to benefit from 100% of the reservoir storage capacity. Hence, over and above a certain CO2 injection rate, it becomes meaningless to invest in bigger compressors to increase this rate to reduce the time of injection.

When the CO2 stream contains impurities, such as N2 or methane, the storage capacity of the reservoir decreases proportionally to the impure stream's compressibility factor and its concentration of impurities. This finding suggests that an economic optimum between the costs of separation, compression and injection can be determined.

Finally, the mass of CO2 sequestrated per pore volume in the equivalent aquifer model is approximately 13 times lower that of the depleted gas condensate reservoir model. This confirms that, because of their low overall compressibility, aquifers offer a far lower ratio of CO2 stored per pore volume than depleted gas condensate reservoirs. However, aquifers tend to have a far larger extent, which often compensates somewhat for this lower ratio and therefore provides storage for significant volumes of CO2.
A Practical Way Out of the GHG Emissions Problem
Authors: Gupta Subodh C.
Published: August 2010

Ever-increasing global demand for energy, and the world's supply predominantly being fossil-based, implies continued growth of emissions. Efficiency improvements and employment of non-fossil energy will definitely help mitigate the problem, but it is generally recognized that "pure carbon offsets" will have to play a major role if the problem has to be combated in a timely fashion. Discussion on pure offsets employing geological storage [namely, carbon capture and storage (CCS)] is advancing rapidly. However, major issues with this approach are its high cost and the long-term post operation liability. The author has previously proposed an alternate approach of pure offset-charcoal sequestration (CS), which essentially employs conversion of dead plant material into inert solid carbon. CS promises to be both less expensive and a better option as far as the operational and post-operation liability is concerned. Among the numerous advantages of the charcoal approach is its easier reversibility, both in terms of liability and costs. Although implementation of this approach at a scale where it can make a significant impact on global CO2 concentration needs to be preceded by a substantial information dissemination and public preparedness, a practical way to introduce it is through using municipal solid waste (MSW) as the feed biomass for CS. This will not only allow time for public acceptance to evolve, and evaluation of potential associated risks, but immediately help mitigate the growing problem of space requirement for waste landfills, waste transport costs and emission of methane from the rotting municipal waste associated with the continued urban sprawl. This paper, aside from describing the carbon sequestration from waste (CSW) method, estimates the cost of carbon offset with this and other competing approaches, such as the use of MSW for conversion to bio-alcohol and for power generation. It highlights the difference between carbon credits associated with mobile energy needs (pure offsets) and stationary energy needs and makes a case for price duality of carbon credits. It also compares the global potential of CSW in combating the greenhouse gas (GHG) problem, making more than two Socolow wedges with use of charcoal for soil enhancement and other purposes amounting to less than 0.04 such wedges. In this work, the cost of carbon offset with CSW is estimated to be as low as CAD 2.6/tonne CO2 equivalent (CO2e).
Permanent Production Packer Installations in Canadian Gas Wells
Authors: Welsh G.A.
Published: August 2010

Permanent production packer installations have been widely used in Canadiangas wells. They also have been used, but to a lesser degree, in oil and waterwells. A permanent production packer virtually becomes a part of the casing andprovides a sound, reliable base on which a successful well completion may bebuilt. Although many types of installations have been used successfully, thispaper will describe only those most commonly used. As tubing movement must be amajor consideration in the design of permanent packer installations, this paperwill also discuss causes, effects and calculations for such movement.

INTRODUCTION

PERMANENT TYPE PRODUCTION PACKERS have proved to be efficient and reliabletools for segregating fluids and pressures in Canadian gas wells. Most suchinstallations have been in wells that are particularly hot, high pressure orcorrosive, and in wells where more than one of these extreme conditionsexist.

Due in part to this variety of conditions -along with fluid, pressure andtemperature changes encountered during well treatment, and well owners'individual preferences -several different basic packer installations haveevolved.

As most of these installations have proved highly successful, it appearsuseful to describe in detail those most commonly used. To this end, differentpermanent packers and allied equipment will be shown and discussed.

This will be followed by diagrams and explanations of the nine most commonbasic installations. As a major consideration in almost all of these gasinstallations has been tubing movement, the causes, effects and calculationsfor same will be described. For the most part, all discussion will be confinedto installations in wells with a single gas zone. With the exception ofreference to hot oil and fluid injection strings, discussion will center onwells with single tubing strings.

PERMANENT PACKERS AND ALLIED EQUIPMENT

Permanent production packers may be set on either wire line or tubing. Ontubing, this may be achieved by mechanical or hydraulic means. Most packers areset on wire line for greater accuracy and speed and to minimize the possibilityof accidental presetting. Such packers fall into two categories top sealing andthrough sealing. Top Sealing packers provide a larger minimum bore (I.D.) forproduction or injection (Figure 1a).

Through Sealing packers allow for the addition of tailpipe to theseals on the tubing string. Also, on some through sealing installations, additional seal units maybe attached and the tubing allowed to travel. Thisminimizes or eliminates the possibility of parting at the surface (Figure1b).

Also available are permanent production packers with packer body extensionson the bottom, on which maybe be installed tailpipe or other equipment, or withpacker bore extensions on the bottom which provide additional sealing borelength and external protection to the seals from corrosive well fluids (Figures2a and 2b.
Association Mapping of Malting Quality Data from Western Canadian Two‐row Barley Cooperative Trials
Authors: Beattie Aaron D. , Edney Michael J. , Scoles Graham J. , Rossnagel Brian G.
Published: August 2010

Re‐examining historical datasets is a proposed use for association mapping (AM) and is particularly valuable when the data describes time‐consuming and/or expensive to measure traits. A collection of 91 elite two‐row malting barley (Hordeum vulgare L.) lines entered in the western Canadian Cooperative Two‐Row Barley Trials over a 13‐ yr period were analyzed by AM to identify markers associated with seven malting quality traits. A linear mixed‐model incorporating population structure and familial relatedness identified 27 diversity array technology (DArT) markers associated with malting quality. These markers will assist selection of parents with complementary allele combinations for future crosses and help identify progeny with the desired alleles. Putative candidate expressed sequence tags (ESTs) responsible for marker‐trait associations were identified for 19 of the 27 DArT markers and include genes important for seed storage protein accumulation, gibberellin‐mediated gene expression, seed storage mobilization, and dormancy. Efforts to identify novel variability in these genes may present opportunities to improve malting quality.
Development of a Multiplex Polymerase Chain Reaction Method for Simultaneous Detection of Four Cimicifuga Species
Authors: Jigden Baigalmaa , Wang Hongtao , Kim Yeon‐Ju , Noh Jong‐Hun , Gotov Choijamts , Lee Jong‐Il , Yang Deok‐Chun
Published: August 2010

Expensive herbs like oriental medicinal plants are always possible targets for fraudulent labeling or misuse in many countries. In the genus Cimicifuga, most species have been used as “Sheng‐Ma” for oriental medicinal purposes. Among the Cimicifuga species, C. heracleifolia Kom., C. dahurica (Turcz. ex Fisch and C.A. Mey.) Maxim., C. foetida L., and C. simplex (DC.) Wormsk. ex Turcz. were used as certified medicinal materials in Korea, China, and Japan. To identify these four Cimicifuga species, the internal transcribed spacer was used for polymerase chain reaction (PCR) analysis, and nucleotide polymorphisms were identified in the four Cimicifuga species. Four specific primers were designed from their polymorphic sites to identify Cimicifuga species using multiplex PCR. The established multiplex‐PCR proved to be effective for the differentiation of Cimicifuga species in commercial materials.
Root Distribution of Temperate Forage Species Subjected to Water and Nitrogen Stress
Authors: Skinner R. Howard , Comas Louise H.
Published: August 2010

Root allocation and distribution patterns can influence forage yield during periods of moisture or nitrogen stress, as deep‐rooted species access water and nutrients found deeper in the soil profile. In a greenhouse study, we examined rooting characteristics to a depth of 50 cm for 21 cool‐season forage species (9 grasses, 6 legumes, and 6 forbs) exposed to drought and low N conditions. The goal of this research was to compare root distribution under uniform growing conditions for common grass, legume and non‐leguminous forb species found in humid‐temperate pastures of the northeast United States. Nitrogen or water stressed grasses generally had greater root biomass and a greater proportion of roots in the 30 to 40 cm soil layer than did stressed legumes or forbs. Low N significantly reduced root weight, but to a lesser extent than the decrease in shoot weight, resulting in an increase in root/shoot ratio. Drought stress reduced shoot weight but had no effect on root weight, also resulting in a greater root/shoot ratio. Drought stress also increased the proportion of deep roots compared with controls, whereas, N stress did not. Comparisons with previously published field studies suggested that information from container‐grown plants could provide insights into field results, and also suggested that inherent species differences in root distribution could explain some, but not all, rooting patterns observed in multi‐species forage mixtures.
Proper Management Improves Seedling Survival and Growth during Early Flooding in Contrasting Rice Genotypes
Authors: Ella Evangelina S. , Dionisio‐Sese Maribel L. , Ismail Abdelbagi M.
Published: August 2010

Flooding following direct seeding reduces germination and emergence in rice (Oryza sativa L.); however, crop establishment can be enhanced through genetic improvement and proper management. This study describes the effects of selected management practices on seedling survival of rice genotypes that vary in tolerance of flooding during germination. Seeds were sown in pots and submerged, and seedling survival was determined 21 d later. Extent of lipid peroxidation and activity of reactive oxygen‐scavenging enzymes in dry seeds and amylase activity in germinating seeds were assessed. Flooding decreased survival in old seeds and in seeds stored at warmer temperature, and this reduction was associated with a decrease in activities of superoxide dismutase and catalase and an increase in lipid peroxidation. Survival, shoot and root growth, and activities of amylase enzymes measured 3 d after sowing were highest when floodwater temperature was 24 to 26°C. Survival decreased with increasing water depth and algal growth and correlated positively with total amylase activity and negatively with lipid peroxidation. Apparently, floodwater conditions and seed handling affects survival in direct‐seeded rice subject to early flooding, and tolerant genotypes are more responsive to such conditions. Sowing properly stored, fresh seeds in a well‐prepared seedbed to control flooding depth and irrigating with water at optimum temperature will further enhance the establishment of tolerant genotypes.
Determining Salinity Threshold Level for Castor Bean Emergence and Stand Establishment
Authors: Zhou Guisheng , Ma B. L. , Li Jun , Feng Chaonian , Lu Jianfei , Qin Pei
Published: August 2010

Castor bean (Ricinus communis L.) is grown on marginal lands that can be prone to having medium to high salt concentrations. This study was done to identify a salinity threshold level for castor bean emergence and stand establishment. Seedlings were first cultured in organic matter–soil mixed media at different salinity levels (0.5, 3.6, 7.1, 10.4, and 13.6 dS m−1) and then transplanted into pots filled with soils at similar salinity levels (0.4, 3.6, 7.1, 10.4, and 13.6 dS m−1). Emergence, survival, seedling growth, nutrient accumulation, and leaf photosynthetic parameters were determined. The salinity threshold level was identified at 7.1 dS m−1 At this salinity level or lower, the emergence rate and survival rate reached 75% or higher; and seedling growth, nutrient accumulation, and leaf photosynthetic parameters were not severely affected. As the salinity level increased to 10.4 and 13.6 dS m−1, emergence rate dropped to below 70%, and survival rate below 50%. Photosynthetic rate and stomatal conductance were reduced by up to 66% and chlorophyll reading by up to 24%. Nutrient uptake and accumulation were also significantly reduced at these two salinity levels. Our results indicate that castor bean could be cultured in plastic seedling trays filled with organic matter–soil mixed seedling media and then transplanted into conventional soils provided that the salinity levels in seedling media and conventional soils are ≤7.1 dS m−1
Combining Ability and Reciprocal Cross Effects of Elite Quality Protein Maize Inbred Lines in Subtropical Environments
Authors: Machida Lewis , Derera John , Tongoona Pangirayi , MacRobert John
Published: August 2010

General combining ability (GCA), specific combining ability (SCA), and reciprocal cross effects information facilitate efficient utilization of inbred lines in a breeding program. A diallel analysis of nine quality protein maize (Zea mays L.) inbred lines was evaluated over seven environments in Zimbabwe. Hybrid × environment interaction was significant for all the traits except for tryptophan content and Quality Index. Thus, phenotyping for tryptophan content and Quality Index can be done using a few environments. There was preponderance of GCA effects for tryptophan content, protein content, kernel endosperm modification, and anthesis dates, while SCA effects were both significant and dominant for grain yield, and were also significant for Quality Index and anthesis dates. Reciprocal effects were significant for Quality Index, tryptophan, and anthesis dates, but on the average they accounted for <13% of the variation among hybrids; hence, they were less important. The cross CML181f × CML176 between heterotic group B inbreds was the highest yielding. Inbred CZL03016 exhibited the most desirable GCA effects for kernel modification, while CML264Q showed the best GCA effects for Quality Index, tryptophan, and protein content. CML264Q would be crucial for use as a donor in breeding for these traits in subtropical maize programs.
Improving Efficiency of Sugarcane Genotype Selection in Florida
Authors: del Blanco Isabel A. , Glaz Barry , Edmé Serge J.
Published: August 2010

The Canal Point (CP) sugarcane (Saccharum spp.) breeding program has developed high‐yielding cultivars for the organic soils of South Florida, but cultivar development has not been as successful for sand soils in this region. Our objectives were to improve final‐stage (Stage 4) selection efficiency of this program by assessing interactions among genotypes, soils, and locations and other sources of variation and by comparing the relationship between repeatability and number of replications as a measure of precision for testing sugarcane genotypes on sand and muck soils. Sources of variation were partitioned for plant‐cane, first‐ratoon, and second‐ratoon data, from 7 yr and five CP series in Stage 4 tested at eight locations on muck soils and two locations on sand soils. Variation related to genotype × location (soil) was highly significant for cane and sugar yields for all series and crops, but most genotype × soil interactions were nonsignificant. This suggested that planting more Stage‐4 tests on sand may improve genotype selection for these soils. The six replications used routinely in Stage 4 provided elevated levels of precision for both soil types. All locations with muck and sand soils in Stage 4 have ample testing resources for discriminating among genotypes. Our results indicate that, to improve sugarcane genotype selection for sand soils, increasing the number of sand locations would be a more successful strategy than increasing replications within locations.
Total Grain‐Arsenic and Arsenic‐Species Concentrations in Diverse Rice Cultivars under Flooded Conditions
Authors: Pillai Tushara R. , Yan Wengui , Agrama Hesham A. , James William D. , Ibrahim Amir M. H. , McClung Anna M. , Gentry Terry J. , Loeppert Richard H.
Published: August 2010

Arsenic (As) is not an essential element and can be toxic to both plants and animals. Low As concentrations in all foodstuffs, including rice grain, is a desirable goal because of the potential detrimental impacts of As on plant growth and yield and its potential toxicity to humans. Twenty‐five diverse rice (Oryza sativa L.) cultivars, including both indica and japonica subspecies, were grown over a 3‐yr period (2004, 2005, and 2007) on a moderate As‐concentration, paddy soil (Dewitt silt loam, fine, smectitic, thermic Typic Albaqualf) under continuously flooded field conditions. The total grain‐As [TGAs; HNO3/H2O2 digestion and analysis by inductively‐coupled‐plasma mass‐spectroscopy (ICP–MS)] and As‐species [trifluoroacetic acid (TFA) extraction and analysis by high performance liquid chromatography (HPLC) coupled with ICP–MS] concentrations and their relationships with plant‐growth parameters (e.g., heading date and yield) were assessed. The only As species detected in milled (polished) rice grain were inorganic AsIII (arsenite) (iAsIII) and dimethylarsinic acid (with pentavalent As) (DMAsV). Total grain‐As (TGAs) and As‐species concentrations, as well as iAsIII/TGAs ratio, each varied widely between cultivars. Arsenic concentration and speciation were mostly dependent on genotype (G), but there were also significant genotype by year (G × Y) and year (Y) effects that were likely impacted by annual differences in environmental conditions, such as temperature, and local soil characteristics. This study indicates the significant potential for lowering rice‐grain As concentration through genotype selection and plant breeding.
Genetic Variability of Cultivated Rhizoma Peanut
Authors: Maas Andrea L. , Anderson William F. , Quesenberry Kenneth H.
Published: August 2010

Rhizoma peanut (RP; Arachis glabrata Benth.) is a vegetatively propagated tropical legume that combines high forage nutritive value and long‐term persistence under a wide range of grazing and harvested hay systems. The objectives of this study were to measure the genetic relatedness among 15 RP accessions and assess purity of accessions maintained at different locations. A total of 22 RP clones were tested and included eight duplicate accessions sourced from the national Arachis collections and germplasm collections from Florida, Texas, and Georgia. Fourteen amplified fragment length polymorphism (AFLP) primer combinations produced a total of 951 bands, with an average of 67.92 ± 6.56 bands per primer combination. Analysis by unweighted pair group mean algorithm found genetic similarity coefficients (GSAs) that ranged from 0.21 to 1.0. STRUCTURE analysis found minimal population structure or admixture for the RP lines in this study. The duplicated accessions showed a range of genetic distances from no genetic drift (GSA 1.0) to a high degree of drift (GSA 0.28). Overall, AFLP markers provided sufficient polymorphism to successfully differentiate RP clones and determine when genetic drift occurred. The AFLPs substantiated genetic dissimilarity of newly released cultivars from standard accessions. Results also indicated the potential for genetic drift occurring from spontaneous crossing among field‐grown accessions, which could lead to selection of improved cultivars.
Quantitative Trait Loci Associated with Resistance to Rice Stripe Virus and Small Brown Planthopper Infestation in Rice
Authors: Zhang Y. X. , Jiang L. , Liu L. L. , Wang B. X. , Shen Y. Y. , Wang Q. , Cheng X. N. , Wan J. M.
Published: August 2010

Rice stripe is a serious viral disease of japonica rice (Oryza sativa L.) cultivars in Asia. Resistance to this disease can be divided into that to rice stripe virus (RSV) and to the pest (small brown planthopper, SBPH). Here we have used a doubled‐haploid (DH) population bred from the cross Zhaiyeqing8 (ZYQ8) × Jingxi17 (JX17) and four separate inoculation methods to genetically dissect the rice stripe resistance present in ZYQ8. Two linked RSV resistance quantitative trait loci (QTLs) were located on chromosome 1, and one on chromosome 11, jointly explaining 30 to 44% of the trait variance. The main‐effect qSTV11 was mapped close to the established RSV resistance gene Stvb‐i For resistance to SBPH, three QTLs were located, mapping to chromosomes 1, 2, and 11, and jointly explaining 44 to 51% of the trait variance. The large‐effect qSBPH1 appears to be a novel QTL conferring a degree of tolerance and antibiosis against SBPH. The positive alleles at all six QTLs were present in ZYQ8. Analysis of a set of chromosome segment substitution lines (CSSLs) in which chromosomal segments of various indica varieties were present in a japonica background showed that rice stripe resistance genes/QTLs are common on the long arm of chromosome 1.
Abundance of SSR Motifs and Development of Candidate Polymorphic SSR Markers (BARCSOYSSR_1.0) in Soybean
Authors: Song Qijian , Jia Gaofeng , Zhu Youlin , Grant David , Nelson Rex T. , Hwang Eun‐Young , Hyten David L. , Cregan Perry B.
Published: August 2010

Simple sequence repeat (SSR) genetic markers, also referred to as microsatellites, function in map‐based cloning and for marker‐assisted selection in plant breeding. The objectives of this study were to determine the abundance of SSRs in the soybean genome and to develop and test soybean SSR markers to create a database of locus‐specific markers with a high likelihood of polymorphism. A total of 210,990 SSRs with di‐, tri‐, and tetranucleotide repeats of five or more were identified in the soybean whole genome sequence (WGS) which included 61,458 SSRs consisting of repeat units of di‐ (≥10), tri‐ (≥8), and tetranucleotide (≥7). Among the 61,458 SSRs, (AT)n, (ATT)n and (AAAT)n were the most abundant motifs among di‐, tri‐, and tetranucleotide SSRs, respectively. After screening for a number of factors including locus‐specificity using e‐PCR, a soybean SSR database (BARCSOYSSR_1.0) with the genome position and primer sequences for 33,065 SSRs was created. To examine the likelihood that primers in the database would function to amplify locus‐specific polymorphic products, 1034 primer sets were evaluated by amplifying DNAs of seven diverse Glycine max (L.) Merr. and one wild soybean (Glycine soja Siebold & Zucc.) genotypes. A total of 978 (94.6%) of the primer sets amplified a single polymerase chain reaction (PCR) product and 798 (77.2%) amplified polymorphic amplicons as determined by 4.5% agarose gel electrophoresis. The BARCSOYSSR1.0 SSR markers can be found in SoyBase (http://soybase.org; verified 21 June 2010) the USDA‐ARS Soybean Genome Database.
Genetic Diversity of Widely Used U.S. Sorghum Hybrids 1980–2008
Authors: Smith Stephen , Primomo Valerio , Monk Roger , Nelson Barry , Jones Elizabeth , Porter Kay
Published: August 2010

Sixty‐three sorghum [Sorghum bicolor (L.) Moench] hybrids that are, or have been, widely used in the United States were profiled using 167 simple sequence repeat (SSR) markers. Genetic distance and cluster analysis determined that 43 (68%) of the hybrids formed seven groupings, with each group containing hybrids commercialized by a single breeding organization. Groupings were also reflective of known pedigrees. Hybrids released by different organizations were not very closely associated with one exception of two hybrids. Groupings had limited association with the decade that the hybrid was released. Numbers of alleles per locus have been constant during the past three decades with gain in new alleles being balanced by loss of other alleles. Hybrids released during the 2000s showed the least number of new alleles compared to the previous two decades. Much of the SSR allelic diversity that was introduced via the Sorghum Conversion Program that converted tropical germplasm to be day‐length neutral has been deployed on U.S. farms. Continued monitoring of genetic gain and genetic diversity are important components of sustainable plant breeding strategies.
Genetic Variation in Testcrosses and Relationship between Line per se and Testcross Performance for Resistance to Gibberella Ear Rot in Maize
Authors: Bolduan C. , Miedaner T. , Utz H. F. , Dhillon B. S. , Melchinger A. E.
Published: August 2010

Gibberella ear rot (GER), caused by Fusarium spp., is a major concern in maize production in Central Europe, and development of hybrid cultivars having GER resistance is an important breeding goal. The objectives of the present study were to (i) evaluate the variation in testcross performance (TP) of European maize germplasm for GER resistance and deoxynivalenol (DON) contamination, (ii) estimate variance components, heritabilities, and correlations of these traits, and (iii) examine the relationship between line per se performance (LP) and TP. Testcrosses of 30 diverse flint inbred lines with two dent inbred testers were evaluated in four environments under artificial inoculation. Data were recorded on severity of GER and concentration of DON. There was substantial GER development and the range of both traits was greater for LP than TP. Estimates of genotypic and genotype × environment interaction variances were significant for testcrosses with both testers. Genotypic variances were generally higher for LP than for TP in each testcross set. Correlations between LP and TP were moderate ( ≤ 0.57) for GER rating and DON concentration. We recommend multi‐stage selection to develop GER resistant maize hybrids based on evaluation of GER resistance under artificial inoculation for (1) LP in one environment followed by (2) TP evaluation in two to three environments. Only the most promising testcrosses should be tested for DON concentration.
Distribution of Rht Genes in Modern and Historic Winter Wheat Cultivars from the Eastern and Central USA
Authors: Guedira M. , Brown‐Guedira G. , Van Sanford D. , Sneller C. , Souza E. , Marshall D.
Published: August 2010

Over 70% of wheat (Triticum aestivum L.) cultivars grown worldwide have a semidwarf phenotype controlled by the major genes Rht‐B1, Rht‐D1, and Rht8c The objective of this study was to determine their frequency in a set of historic and modern soft and hard winter wheat cultivars grown in the central and eastern USA. Three hundred sixty‐two cultivars that were developed from 1808 to 2008 were evaluated with molecular markers for Rht‐B1, Rht‐D1, and Rht8c All cultivars released before 1964 (41 soft winter wheat and 6 hard winter wheat) had wild‐type (tall) alleles at all three loci. After introduction of the dwarfing genes, the percentage of tested lines carrying either Rht‐B1b or Rht‐D1b increased rapidly to greater than 90% of modern varieties. Among soft winter wheat cultivars, the Rht‐D1b dwarfing gene was the most frequent being present in 45% of all lines tested and Rht‐B1b was present in 28%, while in the hard winter wheat cultivars the Rht‐B1b allele is the most prevalent in 77% of lines. Only 8% of the hard cultivars tested had the Rht‐D1b allele. The presence of the 192‐base pair (bp) allele of the microsatellite marker Xgwm261 indicated that Rht8c was less frequently used as a source of dwarfing in U.S. winter wheat germplasm, being present in 8 and 3% of the soft winter wheat and the hard winter wheats, respectively. A number of modern cultivars were identified that did not carry any of the dwarfing genes assayed and may possess alternative reduced height genes.
Plant Breeding with Genomic Selection: Gain per Unit Time and Cost
Authors: Heffner Elliot L. , Lorenz Aaron J. , Jannink Jean‐Luc , Sorrells Mark E.
Published: August 2010

Advancements in genotyping are rapidly decreasing marker costs and increasing genome coverage. This is facilitating the use of marker‐assisted selection (MAS) in plant breeding. Commonly employed MAS strategies, however, are not well suited for agronomically important complex traits, requiring extra time for field‐based phenotyping to identify agronomically superior lines. Genomic selection (GS) is an emerging alternative to MAS that uses all marker information to calculate genomic estimated breeding values (GEBVs) for complex traits. Selections are made directly on GEBV without further phenotyping. We developed an analytical framework to (i) compare gains from MAS and GS for complex traits and (ii) provide a plant breeding context for interpreting results from studies on GEBV accuracy. We designed MAS and GS breeding strategies with equal budgets for a high‐investment maize (Zea mays L.) program and a low‐investment winter wheat (Triticum aestivum L.) program. Results indicate that GS can outperform MAS on a per‐year basis even at low GEBV accuracies. Using a previously reported GEBV accuracy of 0.53 for net merit in dairy cattle, expected annual gain from GS exceeded that of MAS by about threefold for maize and twofold for winter wheat. We conclude that if moderate selection accuracies can be achieved, GS could dramatically accelerate genetic gain through its shorter breeding cycle.
A Major QTL Controlling Seed Cadmium Accumulation in Soybean
Authors: Benitez Eduardo R. , Hajika Makita , Yamada Tetsuya , Takahashi Koji , Oki Nobuhiko , Yamada Naohiro , Nakamura Takehiro , Kanamaru Kyohei
Published: August 2010

Cadmium (Cd) is a pollutant heavy metal that is naturally present in soils and highly toxic to biological organism even at low concentrations. Significant differences were observed among soybean [Glycine max (L.) Merr.] cultivars in the uptake of Cd by root and its posterior translocation to the shoot and grain. The aim of this research was to identify quantitative trait loci (QTLs) for seed Cd concentration in soybean. A single population derived from a cross between the cultivars Harosoy and Fukuyutaka, which differ in seed Cd levels, were used for QTL analysis. The population consisted of 93 F5:6 recombinant inbred lines (RILs), 93 F6:7 RILs, 93 F7:8 RILs, and 100 F6:7 near‐isogenic lines (NILs). A total of 220 simple sequence repeat (SSR) markers were genetically mapped on the 93 F5:6 RILs population and clustered into 22 molecular linkage groups (MLGs) which covered a genetic distance of approximately 2400 centimorgans (cM). Analysis revealed one major QTL (cd1) on Chromosome 9 (MLG K) associated with seed Cd concentration. The cd1 was stable across years–generations and accounted for 82, 57, and 75% of the genetic variation in the RILs populations tested in the field. Effect of cd1 was verified by means of a NIL population developed from the F5:6 RILs. The followup survey results indicated that the novel SSR markers Gm09: 4770663 and Gm09: 4790483 assigned to MLG K seemed to be suitable markers for selecting genotypes with low seed Cd concentration in soybean.
QTL for Yield, Earliness, and Cell Wall Quality Traits in Topcross Experiments of the F838 × F286 Early Maize RIL Progeny
Authors: Barrière Yves , Méchin Valérie , Denoue Dominique , Bauland Cyril , Laborde Jacques
Published: August 2010

QTL for cell wall digestibility related traits were investigated in maize (Zea mays L.) topcross experiments of 240 RILs obtained from the F838 × F286 early maize hybrid. Genotype effects were highly significant for all agronomic and cell wall related traits and much higher than genotype × environment (GE) interaction effects for cell wall digestibility traits. Eight quantitative trait loci (QTL) for dry matter (DM) yield were observed, out of which only one increasing allele originated from F286. Conversely, three QTL out of four with alleles increasing DM content at silage harvest stage originated from the earliest F286 line. Out of four QTL increasing starch content, two QTL, which originated from F838, did not colocalize with silking date QTL or any other investigated traits. Ten QTL were observed for lignin content and between six and nine QTL were observed for each of the three cell wall digestibility investigated traits. QTL located in bins 1.02 (position 76–80 cM), 1.07 (position 228–230 cM), and 8.07 (position 134–142 cM) are likely of priority interest when it comes to improving maize cell wall digestibility. Candidate genes underlying cell wall digestibility QTL were searched for on the basis of in silico investigations and with maize, Arabidopsis, poplar, and eucalyptus genomic information. In most of QTL positions, transcription factors regulating cell wall lignification were shown to be the currently most plausible candidates involved in genetic variation of maize cell wall digestibility.
Genetic Improvement in Winter Wheat Yields in the Great Plains of North America, 1959–2008
Authors: Graybosch Robert A. , Peterson C. James
Published: August 2010

Data from USDA‐coordinated winter wheat (Triticum aestivum L.) regional performance nurseries collected over the time period 1959 to 2008 were used to estimate genetic gain (loss) in grain yield, grain volume weight, days to heading, and plant height in winter wheats adapted to the Great Plains of North America. In both the Southern Regional (SRPN) and Northern Regional Performance Nurseries (NRPN), linear regression revealed significant positive relationships between relative grain yields of advanced breeding lines and calendar year of the nursery trial. The estimated genetic gain in grain yield potential since 1959 was approximately 1.1% (of the control cultivar Kharkof) yr−1 for all entries in the SRPN, and 1.3% yr−1 if only the most productive entry was considered. For the NRPN, the estimates of genetic gain in grain yield were 0.79% yr−1 for all entries, and also 0.79% yr−1 for the most productive entry. Linear regressions of relative grain yields vs. year over the time period 1984 to 2008, however, showed no statistically significant trend in the SRPN. For the same time period in the NRPN, a statistically significant positive slope of 0.83 was observed, though the coefficient of determination (R2) was only 0.28. Relative grain yields of Great Plains hard winter wheats may have peaked in the early to mid‐1990s, and further improvement in the genetic potential for grain yield awaits some new technological or biological advance.
Increased Wheat Grain Hardness Conferred by Novel Puroindoline Haplotypes from Aegilops tauschii
Authors: Reynolds Nicholas P. , Martin John M. , Giroux Michael J.
Published: August 2010

The Puroindoline genes (Pina and Pinb) together comprise the wheat (Triticum aestivum L.) Hardness locus (Ha) located on chromosome 5D and control grain texture. While hard wheats contain a mutation in either Pina or Pinb, there is no puroindoline allelic diversity among soft hexaploid wheats as all carry the Pina‐D1a/Pinb‐D1a alleles. However, Pina and Pinb allelic variation exists within synthetic hexaploid wheats created using novel D genome donors. Here we tested the effects of four Aegilops tauschii‐derived Ha locus haplotypes (Pina‐D1c/Pinb‐D1h, Pina‐D1e/Pinb‐D1i, Pina‐D1a/Pinb‐D1i, and Pina‐D1j/Pinb‐D1i) found in synthetic wheats by crossing them into the soft white spring wheats ‘Alpowa’ and ‘Vanna’. The effect of each Ha haplotype on grain hardness was measured by analyzing backcross or F2–derived lines. All novel Ha loci increased grain hardness while still conditioning soft wheat texture independent of durum or Ae. tauschii synthetic wheat parent line. The Pina‐D1c/Pinb‐D1h haplotype was found to increase grain hardness relative to the wild‐type Ha locus by an average of 6.5 units, Pina‐D1e/Pinb‐D1i by 5.6 units, Pina‐D1a/Pinb‐D1i by 12.6 units, and Pina‐D1j/Pinb‐D1i by 3.8 units. None of the novel Ha locus haplotypes significantly affected Pina or Pinb transcript or protein expression levels. The results indicate that Ae. tauschii derived novel Ha loci could be useful in modifying soft wheat grain texture and end product quality.