bluuebunny/crossref_metadata_2025 huggingface dataset:
Graphene Production With Stirred Media Mills
Authors: Knieke Catharina , Berger Angela , Peukert Wolfgang
Published: October 2010

Since the discovery of stable graphene sheets by Novoselov und Geim in 2004 the one atom thick carbon material has been attracted great interest because of its outstanding physical, mechanical and chemical properties. Although there had been intensive research to find new ways in the preparation of single-layer graphene sheets in the last few years, especially the large-scale production of graphene still remains challenging. In this paper we present a new approach, which allows the high-yield production of graphene sheets in a simple stirred media milling process. Under mild milling conditions single- and multilayer graphene sheets have been successfully produced from commercial graphite powder in a liquid medium. During the delamination procedure, the graphite particles were stressed between the milling beads. Shear and compressive normal forces can lead under mild milling conditions, i.e. low stress energies, to a continuous mechanical peeling of graphene sheets from the graphite surface. By means of Atomic Force Microscopy a high yield of single- and multilayer graphene sheets was detected. A concentration of exfoliated sheets of 2 wt% starting from a 5 wt% suspension of coarse graphite particles could be determined after a milling time of only 3 h. This concentration is much higher than those, which were reached by most of the known chemical methods. Since stirred media milling can be realized as large-scale process, a high-yield and low-cost production of graphene flakes becomes possible at ambient temperature.
Transient Charge Carrier Transport Effects in Organic Field Effect Transistor Channels
Authors: Chang Hsiu-Chuang , Ruden P. P. , Liang Yan , Frisbie C.
Published: October 2010

Transient phenomena that impact the speed of electron devices fabricated from organic semiconductor materials are of critical importance for the development of this new technology. Here we investigate theoretically and experimentally the effects of traps on the establishment and the depletion of the conducting channel in organic semiconductor field effect transistors (OFETs). The device structures explored resemble typical organic thin-film transistors with one of the channel contacts removed. The channel length is varied, and generally is longer than in typical OFETs, in order to vary the carrier transit time. By measuring the displacement current associated with charging and discharging of the channel in these capacitors, transient effects on the carrier transport in organic semiconductors may be studied. When carriers are injected into the device, a conducting channel is established with traps that are initially empty. Gradual filling of the traps then modifies the transport characteristics of the injected charge carriers. In contrast, DC experiments as they are typically performed to characterize the transport properties of organic semiconductor channels investigate a steady state with traps partially filled. Numerical and approximate analytical models of the formation of the conducting channel and the resulting displacement currents are presented. Two simple scenarios are considered first: the spatially-averaged carrier density model neglects carrier dynamics but shows the salient trapping/detrapping effects. Second: a simple geometric model neglects traps but elucidates the effect of carrier dynamics and is used to define an effective mobility that can be extracted from experiments. Finally, numerical simulations are used to study the dynamical and trap effects together. Comparing the average trapping time with the time scale of the current transient sheds light on the influence of traps on the effective mobility. If the average trapping time is very long the effect of traps is negligible and the mobility is largely unaffected by traps on the timescale of the experiment. If the average trapping time is short the effective mobility is reduced but it is time-independent. However, the effective mobility changes with time if the average trapping time is comparable to the current transient interval, eventually reaching a constant value once the trapping and detrapping events balance. Furthermore, the temperature dependence of the effective mobility arising from the temperature dependence of the trap emission rate is explored. Experimental data for pentacene based devices of different channel length and obtained over in the temperature range 120K < T < 300K support the concepts of the physical model.
High-power Organic Field-effect Transistors Using a Three-dimensional Structure
Authors: Uno M. , Hirose Yuri , Nakayama Kengo , Uemura Takafumi , Nakazawa Yasuhiro , Takimiya K. , Takeya Jun
Published: October 2010

Three-dimensional organic field-effect transistors with multiple sub-micrometer channels are developed to exhibit high current density and high switching speed. The sub-micrometer channels are arranged perpendicularly to substrates and are defined by the height of a multi-columnar structure fabricated without using electron-beam-lithography technique. For devices with dinaphtho[2,3-b:2',3'-f]thieno[3,2-b]thiophene, extremely high current density exceeding 10 A/cm2 and fast switching within 200 ns are realized with an on-off ratio of 105. The unprecedented performance is beyond general requirements to control organic light-emitting diodes, so that even more extensive applications to higher-speed active-matrices and display-driving circuits can be realized with organic semiconductors.
Histologic and Histometric Evaluation of Bovine Cancellous Bone and Beta-Tricalcium Phosphate 45 Months After Grafting in Maxillary Sinus
Authors: Khatiblou Farokh
Published: October 2010

The aim of this report is to determine the long-term histologic and histometric evaluation of beta-tricalcium phosphate (beta-TCP) and bovine cancellous bone grafted into the left maxillary sinus of a patient in order to augment the sinus floor to prepare it for receiving an implant. Beta-TCP and bovine cancellous bone (BCB) were grafted into the left maxillary sinus at the extracted sites of maxillary left first and second molars of a 62-year-old male patient. Using osteotome technique, 45 months later, core biopsies were taken for histologic and histometric comparison of the newly formed bone. Histometric and histologic evaluation of both specimens revealed a normal maxillary bone structure with 23.08% calcified bone and 76.92% marrow and connective tissue for the beta-TCP grafted site, and 24.81% calcified bone with 75.19% marrow and connective tissue for the BCB grafted site. No residual grafting material was seen in either specimen. Both beta-TCP and BCB were completely resorbed and replaced by new bone 45 months after grafting. Histologic results of the newly formed bone were similar for both grafting materials.
Predator manipulation experiments: impacts on populations of terrestrial vertebrate prey
Authors: Salo Pälvi , Banks Peter B. , Dickman Chris R. , Korpimäki Erkki
Published: October 2010

Quantifying the relative impacts of top‐down vs. bottom‐up control of ecosystems remains a controversial issue, with debate often focusing on the perennial question of how predators affect prey densities. To assess predator impacts, we performed a worldwide meta‐analysis of field experiments in which the densities of terrestrial vertebrate predators were manipulated and the responses of their terrestrial vertebrate prey were measured. Our results show that predation indeed limits prey populations, as prey densities change substantially after predator manipulations. The main determinant of the result of an experiment was the efficiency of predator manipulation. Positive impacts of predator manipulation appeared to increase with duration of the experiment for non‐cyclic prey, while the opposite was true for cyclic prey. In addition, predator manipulation showed a large positive impact on cyclic prey at low prey densities, but had no obvious impact at peak prey densities. As prey population densities generally respond predictably to predator manipulations, we suggest that control of introduced vertebrate predators can be used to effectively conserve and manage native wildlife. However, care should be taken when controlling native predators, especially apex species, owing to their importance as strong interactors and the biodiversity value of their habitats. We discuss gaps in our knowledge of predator–prey relationships and methodological issues related to manipulation experiments. An important guideline for future studies is that adequate monitoring of predator numbers before and during the experiment is the only way to ensure that observed responses in prey populations are actually caused by changes in predation impacts.
Morphological Characterization of Ugandan Sweetpotato Germplasm
Authors: Yada B. , Tukamuhabwa P. , Alajo A. , Mwanga R. O. M.
Published: October 2010

Sweetpotato [Ipomoea batatas (L.) Lam] is a widely grown and consumed root crop in Uganda. A total of 1303 accessions of sweetpotato germplasm collected from 21 districts of Uganda were planted for morphological characterization. Forty morphological descriptors were scored on 1256 accessions 90 to 100 d after planting. Stepwise discriminant analysis showed that the discriminating power of 20 morphological traits was sufficient to differentiate the accessions. The level of morphological variation for the 40 traits estimated using the Shannon Weaver diversity index (H') ranged from 0.10 to 0.99, with an overall mean of 0.71 ±0.03, suggesting a highly diverse collection. Cluster analysis using the unweighted pair‐group method using arithmetic averages grouped the 1256 accessions into 20 major clusters, with the number of accessions per cluster ranging from 15 to 166. The general leaf outline was highly correlated with leaf lobe type (r = 0.79) and leaf lobe number (r = 0.80) and were the predominant characters in grouping the accessions to clusters. No grouping of accessions based on region of origin was observed, suggesting movement of germplasm between regions. Approximately 70% of the accessions were morphologically distinct and a collection of 946 accessions was selected to represent Ugandan sweetpotato landrace diversity. The complete passport data for this collection is available at: http://www.viazivitamu.org/ugasp_db/gis.htm
Construction of a Genetic Linkage Map for the Olive Based on AFLP and SSR Markers
Authors: Aabidine Amal Zine El , Charafi Jamal , Grout Cinderella , Doligez Agnès , Santoni Sylvain , Moukhli Abdelmajid , Jay‐Allemand Christian , Modafar Cherkaoui El , Khadari Bouchaib
Published: October 2010

Genetic mapping is essential for quantitative trait locus (QTL) identification related to interesting traits. However, only two genetic maps on olive have yet been published, with very few transferable markers. We have constructed a linkage map of the olive according to a “two‐way pseudo‐testcross” mapping strategy and based on the progeny generated from a cross between ‘Picholine marocaine’ (female parent) × ‘Picholine du Languedoc’ (male parent) cultivars. A total of 592 markers (47 simple sequence repeat [SSR], 509 amplified fragment length polymorphism [AFLP], 27 inter‐simple sequence repeat [ISSR], eight random amplified polymorphic DNA [RAPD], and one sequence characterized amplified region [SCAR] marker) were scored in 140 F1 progeny. Linkage groups were defined at a likelihood odds ratio score of 6.00 and a recombination fraction of 0.40. The maternal map consisted of 175 markers clustered into 40 linkage groups and spanning 1547.40 cM, while the paternal map was based on 170 markers clustered into 38 linkage groups and covering 1428.00 cM. For the consensus map, 345 markers were used covering 2366.4 cM and clustered into 49 linkage groups with a mean distance between two adjacent loci of 8.06 cM and the estimated map coverage of 72.6%. This integrated map provides a useful tool for the detection of QTLs controlling economically important traits.
Selection for Reduced Fusarium Ear Rot and Fumonisin Content in Advanced Backcross Maize Lines and Their Topcross Hybrids
Authors: Eller Magen S. , Payne Gary A. , Holland James B.
Published: October 2010

Backcross breeding is an important method to improve elite cultivars for traits controlled by a small number of loci but has been used less frequently to improve quantitatively controlled traits. Resistances to Fusarium ear rot [caused by Fusarium verticillioides (Sacc.) Nirenberg (teleomorph Gibberella moniliformis Wineland)] and contamination by the associated mycotoxin fumonisin in maize (Zea mays L.) are quantitatively inherited. We backcrossed the more resistant but unadapted inbred GE440 for four generations to the susceptible but agronomically elite commercial inbred FR1064. A selected set of 19 BC4F1:3 lines had greater resistance to ear rot and fumonisin content than their recurrent parent FR1064. Topcrosses of the selected lines had greater resistance to Fusarium ear rot and similar grain yield compared to the topcross of the recurrent parent FR1064. We also genotyped selected lines at DNA markers linked to ear rot and fumonisin resistance quantitative trait loci (QTL) identified in the BC1 generation of this cross to determine which QTL demonstrated allele frequency shifts due to selection. Markers linked to QTL on chromosomes 1 and 4 inherited the GE440 allele significantly more often than expected by random chance.
Effects of the Alleles at OsAGPS2 and OsSUT1 on the Grain Filling in Extra‐Heavy Panicle Type of Rice
Authors: Kato Tsuneo , Taniguchi Ayano , Horibata Akira
Published: October 2010

Rice (Oryza sativa L.) cultivars of extra‐heavy panicle type (EHPT), which have numerous spikelets in a panicle, often fail to realize their high‐yield potential due to poor grain filling in general, while some EHPTs showed relatively better grain filling. This study first surveyed nucleotide polymorphisms in rice genes possibly related to grain filling, that is, genes for ADPglucose pyrophosphorylase (AGPase) subunits, OsAGPS2 and OsAGPL2, and a sucrose transporter gene, OsSUT1, to clarify the causes underlying such genetic variation. Many types of polymorphisms were detected in all three genes, but none of them affected amino acid sequences. OsAGPS2 and OsSUT1 had an identical series of polymorphisms in two EHPT cultivars, Milyang 23 and Nanjing 11, both of which have a high degree of grain filling, while another series for these genes was detected in other EHPTs showing a low grain filling. The former polymorphisms could constitute alleles for good grain filling in OsAGPS2 and OsSUT1, designated as AS2‐2 and SUT1‐2, respectively. Second, new molecular markers based on the polymorphisms for OsAGPS2 and OsSUT1 were developed. Finally, three EHPT cultivars with AS2‐2 SUT1‐2 genotype showed a higher degree of grain filling and higher activity of AGPase than three other EHPTs with another genotype at these loci. These results suggest that these AS2‐2 and SUT1‐2 alleles can contribute to the improvement of poor grain filling of EHPTs assisted with the developed markers.
Role of Phosphatidic Acid in High Temperature Tolerance in Maize
Authors: Chen Junping , Xu Wenwei , Burke John J. , Xin Zhanguo
Published: October 2010

Maize (Zea mays L.) germplasm exhibits large genetic variations in tolerance to high temperature (HT) stress under field conditions, but the mechanisms underling this variation are largely unknown. Based on many years of field observation, maize inbred line B76 consistently displays better tolerance to HT than B106. Heat waves during growing season cause leaf firing in developing leaves and tassel blasting in B106 but not in B76. The difference in HT tolerance between the two inbred lines was confirmed in growth chambers under controlled conditions. The two inbred lines showed similar level in the induction of heat shock proteins and a maize chloroplast protein synthesis elongation factor (EF‐Tu), two mechanisms known to involve in HT tolerance in maize. A drastic decrease in photosynthetic system II (PSII) quantum efficiency occurred at 34 to 35°C in B106; in B76, it occurred at a much higher temperature (>38°C). Cell membranes of B76 appeared to be more stable under HT than those of B106 based on electrolyte leakage analysis. Lipid profiles of young developing leaves by lipidomics showed that, among all lipids detected, only phosphatidic acid (PA) exhibited significant higher level in B76 than in B106 under both normal and HT stressed conditions (p < 0.02). Moreover, PA was the only lipid that was significantly increased by HT treatment (p < 0.05). Our results suggest that membrane thermostability is essential to HT tolerance and that PA may play an important role in imparting membrane thermostability, and, hence, HT tolerance in maize.
Source of Resistance Affect Soybean Yield, Yield Components, and Biomass Accumulation in Heterodera glycines‐Infested Fields
Authors: Rotundo J. L. , Tylka G.L. , Pedersen P.
Published: October 2010

The soybean cyst nematode (Heterodera glycines Ichinohe) is the main yield limiting pathogen of soybean [Glycine max (L.) Merr.] in the USA. Resistant cultivars are the most efficient management tool today. Our research studied the physiological basis of yield differences between H. glycines‐susceptible and H. glycines‐resistant cultivars developed from the Hartwig, PI 88788, and Peking sources of resistance at two locations in Iowa during 2005 and 2006. Supplementing resistance with chemical control may improve soybean yield and/or nematode control, so nematicide application {aldicarb[2‐methyl‐2 (methylthio) propionaldehyde O‐(methylcarbamoyl) oxime]} was included as an experimental factor. Aldicarb increased total plant biomass by 9% during R1–R5 soybean growth stages, but there was no increase in seed yield. Yields of the resistant cultivars were greater than those of the susceptible cultivars, except for the Peking source. Compared with the susceptible cultivars, cultivars with H. glycines resistance from PI 88788 had a 13% increase in yield associated with a 15% increase in growth during R1–R5. In cultivars with resistance from Hartwig, a 6% increase in yield was associated with a 4% increase in R1–R5 duration and increased seed‐set efficiency. This work demonstrates that yield increases due to resistance to H. glycines can be attained by different physiological mechanisms associated with the different resistance sources and probably are controlled by different genes. This opens the possibility of pyramiding genes conferring resistance by different mechanisms.
Role of Host‐plant Resistance and Disease Development Stage on Leaf Photosynthetic Competence of Soybean Rust Infected Leaves
Authors: Kumudini S. , Godoy C. V. , Kennedy B. , Prior E. , Omielan J. , Boerma H. R. , Hershman D.
Published: October 2010

Host‐plant resistance is known to reduce fungal growth of Phakospora pachyrhizi Syd. & P. Syd., the causal agent of soybean rust (SBR) in soybean (Glycine max L. Merr.). This disease has been shown to reduce soybean leaf photosynthesis in susceptible soybean plants. Since resistant lines have reduced fungal growth, the resistance genes may protect these plants against injury to leaf photosynthesis. The objectives of this study were to determine the impact of a host‐plant resistance gene and disease developmental stage on leaf photosynthesis. Two controlled‐environment studies and a field experiment were conducted using genotypes resistant and susceptible to SBR. Photosynthesis was measured at the pre‐ and the post‐sporulation disease developmental stage and its quantitative impact was calculated for the genotypes. The susceptible genotypes formed tan, sporulating lesions, and the resistant genotype formed reddish‐brown (RB), nonsporulating lesions. The resistant genotype reduced disease severity (measured as relative lesion area). The negative impact of SBR on leaf photosynthesis was the same for resistant and susceptible genotypes (at equivalent disease severity levels), and the pre‐ and postsporulation disease development stages. Since the resistant genotype formed significantly lower lesion area, the reduced disease severity and the lack of sporulation in the resistant genotype will likely minimize the impact of the disease on canopy photosynthesis and yield.
Comparison of the Effects in Field Tests of Soybean Cyst Nematode Resistance Genes from Different Resistance Sources
Authors: Delheimer J. C. , Niblack T. , Schmidt M. , Shannon G. , Diers B. W.
Published: October 2010

The soybean cyst nematode (SCN) (Heterodera glycines Ichinohe) continues to be the most damaging soybean [Glycine max (L.) Merr.] pathogen in the United States. Many quantitative trait loci (QTL) that confer SCN resistance have been mapped. These QTL include rhg1, which was mapped in several sources of SCN resistance, and two resistance QTL mapped from Glycine soja Siebold & Zucc. The objective of this study was to test the effects of different QTL on SCN reproduction in the field, as well as their associated effects on agronomic traits. Three populations of near isogenic lines (NILs) that segregated for major SCN resistance QTL were developed and planted in field plots in 2006 and 2007. Plant introduction (PI) 88788, PI 437654, and G. soja PI 468916 were the sources of the SCN resistance QTL. Soybean cyst nematode field population densities were estimated from soil samples taken shortly after emergence [initial population density (Pi)] and again close to maturity [final population density (Pf)]. A lower SCN reproductive factor (Rf = Pi/Pf) was found on NILs with the SCN resistance alleles from PI 88788 and PI 468916 (p < 0.05) than those with the susceptibility alleles. The rhg1 allele from PI 88788 was also associated with greater yields in multiple environments than those lines with the susceptibility allele. The results indicate that the rhg1 allele from PI 88788 remains as an effective source of resistance to SCN, and with further research, the SCN resistance QTL alleles from G. soja may serve as a novel source of SCN resistance.
Grain‐Yield Heterosis in Zea mays L. Shows Positive Correlation with Parental Difference in CHG Methylation
Authors: Qi X. , Li Z. H. , Jiang L. L. , Yu X. M. , Ngezahayo Frédéric , Liu B.
Published: October 2010

Heterosis has been extensively exploited in maize (Zea mays L.), but the underlying molecular basis remains poorly understood. Identification of molecular markers in the inbred parental lines, which is reliably associated with heterosis, is of apparent breeding interest. We report here that a specific type of cytosine‐methylation‐based epigenetic difference, that is, CHG methylation (H is A, C, or T) at the 5′‐CCGG sites of randomly sampled genomic loci, is positively correlated with grain yield (GY) heterosis in maize (P < 0.01). This conclusion was reached based on an analysis of cytosine methylation differences for 12 maize parental inbred lines by methylation‐sensitive amplification polymorphism analysis and on field trials for GY of the inbred parental lines together with 132 F1 hybrids produced by complete diallel crossing. Multiple regression analysis showed that the parental difference in CHG methylation level (relative amount) was positively correlated with both midparent heterosis and better‐parent heterosis in GY. In contrast, no correlation with GY heterosis was detected for parental differences in CG or total (CG+CHG) methylation levels. Also, no significant correlation was obtained between the amplified fragment length polymorphism‐based genetic difference and heterosis in GY for the same set of inbred lines and hybrids. We conclude that parental difference in CHG methylation is a promising molecular marker for grouping germplasms into heterotic groups in maize.
Comparisons of Genetically Modified and Non‐Genetically Modified Soybean Cultivars and Weed Management Systems
Authors: Owen M. D. K. , Pedersen P. , De Bruin J. L. , Stuart J. , Lux J. , Franzenburg D. , Grossnickle D.
Published: October 2010

Adoption of glyphosate‐resistant crops and the use of glyphosate has resulted in the evolution of glyphosate‐resistant weeds. The objective of the studies reported was to investigate yield and weed management systems of genetically modified (GM) and non‐GM soybean [Glycine max (L.) Merr.] at three Iowa locations during 2007 and 2008. Yield of glyphosate‐resistant, glufosinate‐resistant, and non‐GM cultivars was determined in six site–years. The non‐GM cultivars yielded 315 and 265 kg ha−1 less than the glyphosate‐resistant and glufosinate‐resistant cultivars, respectively, while no differences between GM cultivars were observed. Weed management systems differed for the cultivars but had equivalent weed control (>90%). Weed management systems in the non‐GM cultivars caused more phytotoxicity (36% versus approximately 5% 7 d after application) and, coincidentally, the non‐GM cultivars had the lowest yields. No differences in phytotoxicity were observed among the weed management systems for the GM cultivars. Similarly, no differences in yield were observed comparing the weed management systems for the GM cultivars. The experiment locations did not have high weed population densities although the untreated controls yielded 48% less than the other weed management systems included in the studies. Given concerns for glyphosate‐resistant weeds, the studies demonstrated that acceptable and equivalent options to glyphosate‐resistant soybean exist to manage glyphosate‐resistant weeds in maturity groups 2 and 3 soybean which represent the majority of the U.S. soybean production.
The Use of Root Gall Ratings to Determine High Risk Zones in Cotton Fields Infested by Meloidogyne incognita
Authors: Wrather J. A. , Stevens W. E. , Vories E. D. , Kirkpatrick T. L. , Mueller J. D. , Mauromoustakos A.
Published: October 2010

Farmers growing cotton (Gossypium hirsutum L.) need a reliable, accurate, and inexpensive method for mapping areas of potentially high risk from root‐knot nematodes (RKN) [Meloidogyne incognita (Kofoid & White) Chitwood] within individual fields for site‐specific application of nematicides. Evaluation of postharvest cotton roots for galling severity due to RKN may be an alternative to soil analysis for nematodes for developing these maps. The main objectives of this study were to determine the relationship between yield of cotton and root galling severity the year before planting, and the estimated costs per hectare for rating root galling severity compared with that of conventional soil sampling using a 15‐m grid spacing. There was a significant negative correlation between root galling severity in October and cotton yield the next 2 yr, indicating galling severity may be a useful indicator of the potential threat of RKN to crop performance for more than 1 yr. The estimated costs for assessing galling severity, $183 ha−1, were much less than for soil analysis for nematodes, $968 ha−1 Unfortunately, maps based on galling severity will only be useful guides for site‐specific application of nematicides if RKN is the only economically important cotton parasitic nematode present. More accurate and less expensive ways of sampling for RKN are needed to identify within‐field areas where the risk of nematode‐induced yield loss is high.
Obtaining Sethoxydim Resistance in Seashore Paspalum
Authors: Heckart Douglas L. , Parrott Wayne A. , Raymer Paul L.
Published: October 2010

Herbicide resistance has been a sought‐after trait for turfgrasses, however attempts to commercialize genetically modified (GM) turfgrasses have been unsuccessful. Sethoxydim (2‐[1‐(ethoxyimino]butyl)‐5‐[2‐(ethylthio)propyl]‐3‐hydroxy‐2‐cyclohexen‐1‐one) is a grass‐specific herbicide, and resistance results from one of two possible single base‐pair (bp) mutations. The most common mutation is an isoleucine (Ile) to leucine (Leu) substitution caused by an A to T mutation at position 1781 of acetyl coenzyme A carboxylase. Research was initiated to develop a novel source of resistance to sethoxydim in seashore paspalum (Paspalum vaginatum Swartz) The objectives of the present study were to develop in vitro selection and regeneration protocols to select for naturally occurring mutations conferring herbicide resistance. A dose response experiment was performed to determine the optimum sethoxydim concentration for selection. Callus was induced from immature inflorescences then plated on callus induction medium containing 10 μM sethoxydim for selection. Green plants were regenerated from resistant callus, the Ile to Leu mutation documented, and expression of herbicide resistance confirmed.
Greenhouse Investigation of Strobilurin Fungicide Applications on Creeping Bentgrass Root Characteristics under Two Irrigation Regimes
Authors: Brosnan J. T. , Horvath B.J. , Elmore M.T. , Breeden G.K. , Sorochan J.C.
Published: October 2010

Secondary effects of strobilurin applications may improve creeping bentgrass tolerance to high temperature stress. This research evaluated the effects of two strobilurin fungicides on the rooting of ‘Penncross’ and ‘Penn A‐1’ creeping bentgrass (Agrostis stolonifera L.) managed under two irrigation regimes during high temperature conditions in a greenhouse. The light and frequent (LF) regime irrigated to 100% evapotranspiration daily, and the deep and infrequent (DI) regime irrigated at leaf wilt to a 30 cm depth. Plants were maintained in a greenhouse that averaged a maximum daily temperature of 31°C. Fungicide treatments were pyraclostrobin (556 g a.i. ha−1), pyraclostrobin + boscalid (431 + 288 g a.i. ha−1), azoxystrobin (610 g a.i. ha−1), and a nontreated control. Azoxystrobin reduced visual root length and root biomass of Penncross plants compared to nontreated plants. Root length, root length density, and root biomass of azoxystrobin‐treated Penn A‐1 plants were also lower than nontreated plants under LF irrigation. Pyraclostrobin increased the visual root length of both cultivars under DI irrigation, and resulted in Penn A‐1 plants exhibiting increased total root length, root surface area, root length density, root volume, and root biomass compared to nontreated plants. Changes in rooting were not associated with changes in turfgrass quality for either cultivar. Additional research is needed to determine if these responses are present following applications in the field.
Allelic Variation and Geographical Patterns of Prolamins in the USDA‐ARS Khorasan Wheat Germplasm Collection
Authors: Rodríguez‐Quijano Marta , Lucas Regina , Ruiz Magdalena , Giraldo Patricia , Espí Araceli , Carrillo José M.
Published: October 2010

Khorasan wheat, Triticum turgidum ssp. turanicum (Jakubz), is an ancient cultivated wheat possessing several characteristics that may be useful for durum wheat improvement. In this paper, the allelic variation of prolamins, principal determinants of pasta quality, has been studied in 77 accessions from the USDA‐ARS germplasm collection. Some prolamin subunits difficult to identify by standard electrophoretic methods were analyzed by molecular and proteomic techniques. These analyses allowed identifying unambiguously the subunits combination HMW‐GS 7+16 (usually mistaken for 13+16) and the 13+8 (HMW‐GS) not found so far in wheat. In total, 22 different genotypes were found for the entries from 21 countries analyzed. Prolamin alleles related to good quality in durum wheat have been identified. Also, new allelic variants were identified at almost all the loci, providing a new source of genetic variability with a potential use in breeding. Two geographical distribution patterns of prolamin alleles, with contrasting differences in pasta quality, were detected: one for the Southwest of Asia, and other for the Mediterranean zone. Seven accessions, mainly from Ethiopia and not included in any of those two groups, were rather unique. The results obtained in this study can help to select breeding material and in a more efficient use of the collection.
Geographic Description of Genetic Diversity and Relationships in the USDA Rice World Collection
Authors: Yan WenGui , Agrama Hesham , Jia Melissa , Fjellstrom Robert , McClung Anna
Published: October 2010

Knowledge of genetic diversity and relationships among global germplasms of rice collected by the USDA since 1866 is critical for utilization, conservation, and management of the collection. A core subset developed from this collection, including 1794 accessions obtained from 112 countries in 14 geographic regions, was genotyped with one indel and 71 simple sequence repeat (SSR) markers. Total alleles were 1005, averaging 14 alleles per locus. A great majority of genetic variance was due to within instead of among geographic regions and within instead of among countries. The regions and countries were highly and significantly differentiated using these markers. Germplasm accessions obtained from the southern Asia, Southeast Asia, and Africa were highly diversified, while those from North America and western and eastern Europe had the lowest diversity. Different measurements of genetic diversity, including average number of alleles per locus, polymorphism information content (PIC), Nei index, and average number of private alleles per locus uniformly reached this conclusion. Three main clusters were revealed by both analyses of principal coordinates and Nei genetic similarities for the 14 regions. Seventy‐eight countries, from which five or more accessions were collected in the core subset, were differentiated into five main clusters. Germplasm accessions obtained from Myanmar, Indonesia, Cambodia, Malaysia, and Nepal were highly diversified, while those from France, Spain, Romania, Italy, and the United States were poorly diversified. This study proves that the USDA global collection effectively supports the U.S. rice industry with vast genetic diversity responsive to biotic and abiotic stresses.
Area Under the Dry Down Curve (AUDDC): A Method to Evaluate Rate of Dry Down in Maize
Authors: Yang J. , Carena M. J. , Uphaus J.
Published: October 2010

Maize (Zea mays L.) hybrids with fast field dry down are economically desirable across production regions. However, accurately measuring this genetically complex trait in a simple way has been a challenge to maize breeders. The objective of this research was to propose and test an efficient, simple, and reliable procedure to select genotypes with fast dry down in maize. Area under the dry down curve (AUDDC), an index representing the dynamic progress of field dry down, was proposed. The main experiment included 144 hybrids arranged in a partially balanced lattice design across four short‐season environments in North Dakota. Data collected were silking date, ear moisture at four 7‐d intervals starting 45 d after pollination, harvest moisture, test weight, and grain yield. Results showed significant genotype × environment interaction for most traits including AUDDC. However, AUDDC had the largest broad‐sense heritability (H) among traits (0.84), suggesting it can be effectively utilized to identify faster drier inbred lines and hybrids. Strong correlations were found between AUDDC and silking date, AUD and moisture content at physiological maturity, and AUDDC and harvest moisture. Area under the dry down curve is proposed as an indirect measurement for dry down rate and we encourage its use to develop lines and hybrids with faster dry down.
Adaptation and Performance of CIMMYT Spring Wheat Genotypes Targeted to High Rainfall Areas of the World
Authors: Tadesse W. , Manes Y. , Singh R. P. , Payne T. , Braun H. J.
Published: October 2010

The high rainfall mega‐environment [mega environment 2 (ME2)], characterized by more than 500 mm rainfall during wheat season, is one of the 12 mega‐environments on which the global wheat breeding program of the International Maize and Wheat Improvement Center (CIMMYT) has been assembling and distributing high rainfall wheat yield trials (HRWYT) since 1992. In this study, our objectives were to evaluate the adaptation and performance of entries included in the 1st through the 12th HRWYT (1992–2004), identify best lines as parents for crossing and recommend for direct release by the National Agricultural Research Systems (NARS), and test the association among sites and determine yield progress in HRWYTs. Combined ANOVA across locations for grain yield showed highly significant difference among genotypes and genotype × environment interactions (p < 0.001) for each of the HRWYTs. At regional level, wide range of yield variability was observed in Africa (0.69–9.614 t ha−1) followed by Asia (0.389–6.93 t ha−1) with the highest mean yields in Europe (4.392 t ha−1). Two widely grown mega‐cultivars have been developed from Attila cross: entry number 4 (CM85836‐4Y‐0M‐0Y‐8M‐0Y) from 1stHRWYT, which is released as PBW343 in India, and entry number 48 from 4thHRWYT (CM85836‐50Y‐0M‐0Y‐3M‐0Y), which is released in Ethiopia, Tunisia, Iran, Pakistan, and Sudan with local names of Kubsa, Utique96, Chamran, MH97, and Imam, respectively. There is a significant positive association between plant height and grain yield in rain‐fed environments whereas the association between heading dates and yield is location specific indicating the importance of selecting broad range of materials for heading date at the main station in Mexico. Correlation analysis shows that the sites giving the best prediction of global performance are Marcos Juarez (Argentina), Pergamino (Argentina), Izmir (Turkey), Bethlehem (South Africa), Sakha (Egypt), and Tassaout (Morocco). In each year, it was possible to find a line out yielding the local check in at least 52% of the sites. However, at the trial level, lines were beating the local checks more frequently in the first trials than in the last trials. Regular assessment of the current and future HRWYTs in terms of adaptation, resistance, diversity, and quality will be of paramount importance in improving the breeding process.
Soybean Photosynthetic Rate and Carbon Fixation at Early and Late Planting Dates
Authors: De Bruin Jason L. , Singer Jeremy W. , Pedersen Palle , Rotundo José L.
Published: October 2010

Early planting (late April to early May) is recommended for increasing soybean [Glycine max (L.) Merr.] yield but a full understanding of the physiological response is lacking. Carbon dioxide exchange rate (CER) was measured on soybean planted between 18 April and 29 May to determine if CER could resolve this yield difference. During the season CER was measured twice weekly on individual leaves. Total carbon fixation, dry matter accumulation, and radiation use efficiency (RUE) were calculated for the growth periods R1 to R3 and R3 to R6. During the early vegetative stages CER (before flowering) declined for all planting dates and reached a minimum of 0.566 (late planting) to 0.629 (optimal planting) mg CO2 m−2 s−1 by approximately R2 (late flowering) followed by a linear rate increase to a maximum of 1.23 mg CO2 m−2 s−1 by R5 to R6 (early seed fill). The optimal first week of May planting increased main‐stem node number, average CER during R1 to R6, total carbon fixation, and dry matter but did not increase seed yield. Overall, yield and seed number were positively related to CER between R3 and R6. These data demonstrate that (i) CER was controlled by plant growth stage and was independent of the date that growth stage occurred and (ii) early planting did not consistently increase the CER rate during the R3 to R6 growth stage, limiting yield improvement. Factors other than CER are more likely to explain the reported positive yield response to early planting.
Variation among Half‐Sib Families and Heritability for Biomass Yield and Other Traits in Lowland Switchgrass (Panicum virgatum L.)
Authors: Bhandari H. S. , Saha M. C. , Mascia P. N. , Fasoula V. A. , Bouton J. H.
Published: October 2010

Switchgrass (Panicum virgatum L.) is a main herbaceous species projected for use as feedstock in biofuel production. Understanding the nature of genetic variation for biomass yield and other important traits in switchgrass would aid cultivar development. The aim of this study was to estimate the genetic component of variation and narrow‐sense heritability for biomass yield and several morphological and phenological traits in lowland switchgrass. Thirty‐seven half‐sib families were evaluated during 2007–2009 at two south central Oklahoma locations, Ardmore and Burneyville. Half‐sib families were different for biomass yields and other traits, suggesting the presence of additive gene action in controlling these traits. Family × location effects were observed for biomass yield and days to spring regrowth. Stem thickness, plant spread, and spring regrowth showed family × year interaction effects. Days to flowering showed a significant family × location × year interaction. Narrow‐sense heritability for biomass yield was 0.13 based on half‐sib family variation and 0.29 based on parent–progeny regression, suggesting a complex genetics of biomass yield. Stem thickness also had low (≤0.27) and plant height and tillering ability had low to moderate (0.26–0.48) heritability. Heritabilities were moderate (0.47–0.70) for heading, flowering, and plant spread and relatively high (≥0.82) for spring regrowth. The biomass yield was positively correlated with tillering ability, plant height, and stem thickness. Rigorous family evaluation procedure and use of tillering ability as an indirect measure to improve biomass yield could enhanced gain from selection.
Agronomic and Quality Performance of Winter Wheat Backcross Populations Carrying Non‐Adapted Fusarium Head Blight Resistance QTL
Authors: von der Ohe C. , Ebmeyer E. , Korzun V. , Miedaner T.
Published: October 2010

Two BC3F2:5 winter wheat populations carrying Fusarium head blight (FHB) resistance quantitative trait loci (QTL) Fhb1 and Qfhs.ifa‐5A were tested for resistance and agronomic and baking‐quality performance in 10 high yielding environments. The objectives of this study were to determine (i) the resistance effect of the two nonadapted QTL, (ii) their side effects on agronomic and quality performance, and (iii) their relative advantage in European breeding programs. The two populations were split into four QTL classes containing either Fhb1, Qfhs.ifa‐5A, both QTL or neither of them with about 25 (Opus BC3F2:5 population) and 15 (Anthus BC3F2:5 population) lines each class and check varieties. Disease resistance trials on microplots and yield trials on large plots had two replicates at five locations in Germany in each of 2 yr. Mean FHB ratings (%) between QTL classes carrying either one or two QTL showed significantly (p < 0.05) improved FHB resistance and a significant variation within QTL classes. Small significant negative effects on grain yield were detected in the Anthus but not in the Opus BC3F2:5 population. However, selection of lines with improved resistance level and similar high yield level like the recurrent parent was feasible. All other differences in agronomic and quality traits were in all cases small although often significant. The introgression of both QTL did not significantly improve the FHB resistance compared to Qfhs.ifa‐5A indicating that this QTL suffices for European breeding programs.
Enumeration of Soybean‐Associated Rhizobia with Quantitative Real‐Time Polymerase Chain Reaction
Authors: Furseth Branden J. , Conley Shawn P. , Ané Jean‐Michel
Published: October 2010

The symbiotic relationship between soybean [Glycine max (L.) Merr.] and rhizobial bacteria such as Bradyrhizobium japonicum allows biological nitrogen fixation (BNF), which, along with residual soil N, can meet the seasonal needs of a soybean crop. The widespread use of rhizobia inoculants to encourage BNF is not strongly supported by previous research. A high throughput, efficient method for quantifying rhizobia would be a valuable tool for assessing the need of inoculation on a case by case basis. Such a method is also needed for large‐scale research on rhizobia populations in various environments and cropping systems. The objective of this study was to create a new method for quantifying soybean‐specific rhizobia in the soil using quantitative (real‐time) polymerase chain reaction (qPCR). Soil from 12 plots with presumably different rhizobia populations was collected from a long‐term corn (Zea mays L.)–soybean rotation study near Arlington, WI, and the most probable number (MPN) of rhizobia in the soil was determined. DNA from the soil was analyzed with qPCR using primers targeting the nodZ specificity gene for nodulation. The qPCR quantification was correlated to the MPN with a simple regression model. The relationship between MPN and qPCR was described by the equation threshold coefficient (CT) = 33.43 – 0.85[ln(MPN)], with an adjusted R2 of 0.88. These data allow for the prediction of soybean‐associated rhizobia populations in the soil based on the qPCR analysis of extracted DNA.
Multi‐Level Determination of Heat Tolerance in Cotton (Gossypium hirsutum L.) under Field Conditions
Authors: Cottee N. S. , Tan D. K. Y. , Bange M. P. , Cothren J. T. , Campbell L. C.
Published: October 2010

Screening a diverse set of cotton genotypes for heat tolerance may enable identification of superior germplasm for inclusion in future breeding programs. This study used a multilevel approach to assess whether cultivar differences in biochemistry reflected physiology or yield performance under high temperature environments for high yielding genotypes. Membrane integrity and enzyme viability were determined for genotypes Sicot 53, Sicala 45, Sicala V‐2, and CSX 99209‐376 subjected to high water bath temperatures. The temperature for 50% membrane integrity was lowest for Sicala 45 (temperature [°C] at which 50% relative electrical conductivity occurred [T50] = 39.3°C) and enzyme viability was highest for Sicot 53 (spectrophotometric absorbance at 530 nm at a specific water bath temperature [Abst] = 1.1) compared with the other genotypes (T50 = 43.7–44.7°C and Abst = 0.6–0.7), indicating relative heat tolerance was higher for Sicot 53 and lower for Sicala 45. To validate this approach in the field, Sicot 53 and Sicala 45 were evaluated for yield, gas exchange, and fluorescence under high temperature tents. Sicot 53 outperformed Sicala 45 under tents. Yield and fruit retention decreased to a greater extent, photosynthesis and electron transport rate (ETR) were lower and stomatal conductance and transpiration were higher for Sicala 45 compared with Sicot 53 under tents. Electron transport rate, membrane integrity, and enzyme viability were the most rapid and reliable screens for heat tolerance, and the utility of these screens were enhanced by incorporation into a multilevel plant screening model encompassing both laboratory and field based components.
Interaction Effects of Salinity and Mowing on Performance and Physiology of Bermudagrass Cultivars
Authors: Shahba Mohamed A.
Published: October 2010

The effects of mowing management on salinity tolerance are not well understood. These effects were studied on turf quality, clipping yield, root mass, canopy photosynthetic rate (Pn), total nonstructure carbohydrate content (TNC), shoot reducing sugar content (RSC), and K+ and Na+ contents in shoots and roots of Tifgreen, Tifdwarf, and Tifway bermudagrass [Cynodon dactylon (L.) Pers.] cultivars using a hydroponic system. Increasing salinity resulted in a significant (p < 0.05) reduction in turf quality. Canopy photosynthetic rate values in Tifgreen were the highest (9.92, 12.98, and 18.91 μmol CO2 m−2 s−1 at 15, 30, and 45 mm mowing heights respectively) compared with Tifdwarf and Tifway at 20 dS m−1 Tifgreen achieved 22, 20, 21, and 32% more clipping yield than Tifway at control and 8, 16, and 20 dS m−1 salinity levels respectively under the highest mowing level. At the highest mowing height, the increase in Tifgreen, Tifdwarf, and Tifway root mass was 33, 40, and 31%, respectively, as salinity increased from control to 20 dS m−1 Total nonstructure carbohydrate content decreased by 36, 21, and 18% in Tifgreen while RSC increased by 35, 34, and 32% at 15, 30, and 45 mm mowing heights, respectively, as salinity increased from control to 20 dS m−1 Bermudagrass had the highest selectivity of K+ over Na+ when maintained at 45 mm mowing height. Tifgreen showed significantly (p < 0.05) higher salinity tolerance compared to other tested cultivars, and the capability of bermudagrass cultivars to survive salinity stress can be enhanced by increasing mowing height.