bluuebunny/crossref_metadata_2025 huggingface dataset:
Age-Dependent Impairment of Spine Morphology and Synaptic Plasticity in Hippocampal CA1 Neurons of a Presenilin 1 Transgenic Mouse Model of Alzheimer's Disease
Authors: Auffret Alexandra , Gautheron Vanessa , Repici Mariaelena , Kraftsik Rudolf , Mount Howard T. J. , Mariani Jean , Rovira Catherine
Published: August 2009

Presenilin 1 (PS1) mutations are responsible for a majority of early onset familial Alzheimer's disease (FAD) cases, in part by increasing the production of Aβ peptides. However, emerging evidence suggests other possible effects of PS1 on synaptic dysfunction where PS1 might contribute to the pathology independent of Aβ. We chose to study the L286V mutation, an aggressive FAD mutation which has never been analyzed at the electrophysiological and morphological levels. In addition, we analyzed for the first time the long term effects of wild-type human PS1 overexpression. We investigated the consequences of the overexpression of either wild-type human PS1 (hPS1) or the L286V mutated PS1 variant (mutPS1) on synaptic functions by analyzing synaptic plasticity and associated spine density changes from 3 to 15 months of age. We found that mutPS1 induces a transient increase observed only in 4- to 5-month-old mutPS1 animals in NMDA receptor (NMDA-R)-mediated responses and LTP compared with hPS1 mice and nontransgenic littermates. The increase in synaptic functions is concomitant with an increase in spine density. With increasing age, however, we found that the overexpression of human wild-type PS1 progressively decreased NMDA-R-mediated synaptic transmission and LTP, without neurodegeneration. These results identify for the first time a transient increase in synaptic function associated with L286V mutated PS1 variant in an age-dependent manner. In addition, they support the view that the PS1 overexpression promotes synaptic dysfunction in an Aβ-independent manner and underline the crucial role of PS1 during both normal and pathological aging.
The Potassium Chloride Cotransporter KCC-2 Coordinates Development of Inhibitory Neurotransmission and Synapse Structure in Caenorhabditis elegans
Authors: Tanis Jessica E. , Bellemer Andrew , Moresco James J. , Forbush Biff , Koelle Michael R.
Published: August 2009

Chloride influx through GABA-gated chloride channels, the primary mechanism by which neural activity is inhibited in the adult mammalian brain, depends on chloride gradients established by the potassium chloride cotransporter KCC2. We used a genetic screen to identify genes important for inhibition of the hermaphrodite-specific motor neurons (HSNs) that stimulateCaenorhabditis elegansegg-laying behavior and discovered mutations in a potassium chloride cotransporter,kcc-2. Functional analysis indicates that, like mammalian KCCs,C. elegansKCC-2 transports chloride, is activated by hypotonic conditions, and is inhibited by the loop diuretic furosemide. KCC-2 appears to establish chloride gradients required for the inhibitory effects of GABA-gated and serotonin-gated chloride channels onC. elegansbehavior. In the absence of KCC-2, chloride gradients appear to be altered in neurons and muscles such that normally inhibitory signals become excitatory.kcc-2is transcriptionally upregulated in the HSN neurons during synapse development. Loss of KCC-2 produces a decrease in the synaptic vesicle population within mature HSN synapses, which apparently compensates for a lack of HSN inhibition, resulting in normal egg-laying behavior. Thus, KCC-2 coordinates the development of inhibitory neurotransmission with synapse maturation to produce mature neural circuits with appropriate activity levels.
Glycinergic Projection Neurons of the Cerebellum
Authors: Bagnall Martha W. , Zingg Brian , Sakatos Alexandra , Moghadam Setareh H. , Zeilhofer Hanns Ulrich , Lac Sascha du
Published: August 2009

The cerebellum funnels its entire output through a small number of presumed glutamatergic premotor projection neurons in the deep cerebellar nuclei and GABAergic neurons that feed back to the inferior olive. Here we use transgenic mice selectively expressing green fluorescent protein in glycinergic neurons to demonstrate that many premotor output neurons in the medial cerebellar (fastigial) nuclei are in fact glycinergic, not glutamatergic as previously thought. These neurons exhibit similar firing properties as neighboring glutamatergic neurons and receive direct input from both Purkinje cells and excitatory fibers. Glycinergic fastigial neurons make functional projections to vestibular and reticular neurons in the ipsilateral brainstem, whereas their glutamatergic counterparts project contralaterally. Together, these data suggest that the cerebellum can influence motor outputs via two distinct and complementary pathways.
Evidence of Mirror Neurons in Human Inferior Frontal Gyrus
Authors: Kilner James M. , Neal Alice , Weiskopf Nikolaus , Friston Karl J. , Frith Chris D.
Published: August 2009

There is much current debate about the existence of mirror neurons in humans. To identify mirror neurons in the inferior frontal gyrus (IFG) of humans, we used a repetition suppression paradigm while measuring neural activity with functional magnetic resonance imaging. Subjects either executed or observed a series of actions. Here we show that in the IFG, responses were suppressed both when an executed action was followed by the same rather than a different observed action and when an observed action was followed by the same rather than a different executed action. This pattern of responses is consistent with that predicted by mirror neurons and is evidence of mirror neurons in the human IFG.
A Direct Simulation of Adiabatic Charge Transfer Through Bridged Organic Molecules
Authors: Koslowski Thorsten , Steinbrecher Thomas
Published: August 2009

We approach the dynamics of adiabatic charge transfer through bridged triarylamine cations by a direct molecular dynamics simulation involving classical and quantum mechanical degrees of freedom. Within a simple yet chemically specific model, the quantum mechanical subsystem is described by a tight-binding Hamiltonian, which is coupled to a classical force field. From a population analysis of the quantum part, the charge transfer rate can be readily extracted, including the influence of memory effects. The direct computation of the associated thermodynamic potential establishes a close link to analytical rate concepts. The theoretical data are compared to experiments, and the limits and possible extensions of our approach are discussed.
Stability Domains of Multi-Component Crystals in Ternary Phase Diagrams
Authors: Rager Timo , Hilfiker Rolf
Published: August 2009

The topology of ternary phase diagrams of systems that are forming salts, cocrystals, solvates, or hydrates is discussed based on a simple mathematical model. The considerations include the thermodynamic stability of the multi-component crystal relative to the individual components, the character of the interactions in solution, the effect of relative solubility of the components, the consequences of using liquid components, the formation of multi-component crystals with different stoichiometry, and the competition between cocrystals or salts and solvates. Based on the characteristics of the phase diagrams, recommendations are provided as to an efficient design of salt formation and cocrystallization experiments.
Density Functional Study of Defects in Boron Nitride Nanotubes
Authors: Mirzaei Mahmoud
Published: August 2009

The electronic structure properties of two pristine and defected models of zigzag and armchair boron nitride nanotubes (BNNTs) are computationally studied. Chemical shielding (CS) tensors at the sites of various boron-11 (B-11) and nitrogen-15 (N-15) nuclei in each of the optimized structures are calculated and converted to isotropic and anisotropic chemical shieldings (ICS and ACS, respectively). The ACS values revel that boron atoms at the end of nanotube play the major role in determining the characteristic properties of the BNNTs. Defects are considered by removing a B-N bond from the pristine models yielding B-B and N-N bonds in the zigzag but not in the armchair BNNT. The changes of the CS tensors at the sites of those B-11 and N-15 nuclei in the B-B and N-N bonds are the most significant among other nuclei. The calculations are performed employing BLYP method and 6–31G* standard basis set using GAUSSIAN 98.
Serum osteocalcin concentrations in relation to glucose and lipid metabolism in Chinese individuals
Authors: Zhou Mi , Ma Xiaojing , Li Huating , Pan Xiaoping , Tang Junling , Gao Yunchao , Hou Xuhong , Lu Huijuan , Bao Yuqian , Jia Weiping
Published: August 2009

Objectives

Osteocalcin, a bone-derived protein, has recently been reported to affect energy metabolism. We investigated the relationship between serum osteocalcin and parameters of adiposity, glucose tolerance, and lipid profile in Chinese subjects.

Methods

Serum osteocalcin was measured by electrochemiluminescence immunoassay in 254 men (128 with newly diagnosed type 2 diabetes mellitus (T2DM) and 126 with normal glucose tolerance (NGT)), 66 premenopausal women (33 with T2DM and 33 with NGT) as well as 180 postmenopausal women (92 with T2DM and 88 with NGT). Their associations with parameters of adiposity, glucose tolerance, and lipid profile were examined.

Results

Serum osteocalcin concentrations in diabetic patients were significantly lower than those in NGT subjects after adjusted for age, gender, and body mass index (P=0.003). Postmenopausal women had higher osteocalcin concentrations than premenopausal women and men (both P<0.001). Multiple stepwise regression analysis showed that age, %fat, high-density lipoprotein cholesterol, fasting plasma glucose, and fasting serum insulin were independently associated with osteocalcin in men (P<0.05). Age and HbA1c were independently correlated with osteocalcin in postmenopausal women. Besides age and HbA1c, serum triglyceride was also an independent factor influencing osteocalcin in premenopausal women. In addition, osteocalcin was also positively associated with homeostasis model assessment of β-cell function. Furthermore, multiple logistic regression analysis demonstrated that osteocalcin was independently associated with T2DM.

Conclusions

Serum osteocalcin was closely associated with not only fat and glucose metabolism but also with lipid metabolism.
Math for Math's Sake: Non-Euclidean Geometry, Aestheticism, and Flatland
Authors: Henderson Andrea
Published: August 2009

This essay argues that Edwin Abbott's Flatland brings into focus the wide-ranging implications of the dethroning of what Victorians regarded as the preeminent representational system: Euclidean geometry. The contemporary debate surrounding the challenge to Euclid, conducted not just in mathematical but also in psychological, philosophical, and aesthetic terms, turned on an anxiety that signs might not have the capacity to bridge subjective and objective worlds, and Flatland seeks solace for this uncertainty by granting even empty signs unprecedented virtues.
Melancholy, Passionate Love, and the Coita d'Amor
Authors: Blackmore Josiah
Published: August 2009

From (Pseudo-)Aristotle's reflections on wine, poetry, and heroes in problems, book 30, to modern psychoanalytic theory and depression, melancholy has claimed the attention of artists and thinkers throughout the history of Western culture. According to Jennifer Radden's historical analysis, melancholy was “a central cultural idea, focusing, explaining, and organizing the way people saw the world and one another and framing social, medical, and epistemological norms” (vii). It takes a number of forms: for ancient Greek physicians it was a somatic malady, an overwrought contemplativeness and moroseness rooted in the body's humors; for Aristotle it was this, too, but was also a fount of artistic inspiration; for the Italian humanist Marsilio Ficino it was the source of poetic and prophetic powers, a requisite for heightened intellect. Melancholy was, in short, a principle of relation between the interior and exterior realms and as such possessed a weighty hermeneutic charge as a lens through which to experience and read the world. In recent years, scholars in literary and cultural studies have begun to explore the perspectives that melancholy offers for understanding such broad topics as the formation of literary subjectivities and cultural constructions of gender. The persistent presence of melancholy in medieval and early modern literature, following Radden's observation, advocates for its many possibilities as an interpretive tool to shape diverse literary positionalities and socioepistemological modes of being.
Estimating the sorption of pharmaceuticals based on their pharmacological distribution
Authors: Williams Mike , Ong Poh L. , Williams Desmond B. , Kookana Rai S.
Published: August 2009

Pharmaceuticals released into aquatic systems are expected to sorb to sediments to varying degrees. Their sorption is likely to influence their fate and, ultimately, the risk they pose to aquatic organisms. This has led to the European Medicines Agency requiring an assessment of affinity to solids, using batch sorption methods, for the environmental risk assessment (ERA) of new human medicines. However, a large body of data is generated before pharmaceuticals are released onto the market, including their extent of distribution throughout the human body, measured by the volume of distribution (VD). In the present study, batch sorption experiments were undertaken using 12 different soils and sediments to determine whether VD was a good indicator of experimental Kd values for 21 pharmaceuticals. The r2 values obtained from the regressions ranged from 0.39 to 0.76 (with a median value of 0.5) and all regressions were found to be significant. The use of this more comprehensive set of soils and sediments was consistent with previous studies comparing VD and Kd, despite the Kd values of the selected pharmaceuticals varying greatly between soils. The relationship between Kd and VD was greatly improved when zwitterionic antibiotics and carbamazepine were not included, possibly due to complex sorption or pharmacokinetic behavior. There are likely to be a number of factors affecting the sorption of pharmaceuticals that cannot be explained by VD. However, further work may elucidate how these factors can be accounted for, enabling VD to be effectively used to facilitate the ERA of human pharmaceuticals with already available information.
Physiological Mechanisms Underlying Heterosis for Shade Tolerance in Maize
Authors: Liu Weidong , Tollenaar Matthijs
Published: August 2009

Heterosis in maize (Zea mays L.) confers stress tolerance. To better understand the physiological mechanisms underlying the differential response of a maize hybrid (CG60 × MBS1236) and its parental inbred lines to shading stress, studies were conducted in a field hydroponic system in Ontario, Canada, from 2004 to 2006. Shading stress consisted of a 55% reduction in incident solar radiation and was implemented either for a 30‐ to 33‐d period before silking starting at the 7‐leaf tip stage, a 21‐d period during silking, or a 21‐d period after silking. Mean reduction in total dry matter at maturity (TDM) due to the shading treatments was 18%, and this reduction was similar for the three shading periods. Heterosis for grain yield was greater when plants were exposed to shading during the presilking and silking periods compared to the unshaded control. This increase was attributable to increased heterosis for both harvest index and TDM. In contrast, shading during the grain‐filling period did not increase heterosis for grain yield. Heterosis for grain yield was highly associated with heterosis for kernel number. Heterosis for kernel set was attributable, in part, to the relationship between kernel number and plant growth rate (PGR) during the period bracketing silking and the inherent lower PGR of the inbred lines as compared to the hybrid. Kernel set was also affected by shading during the presilking period, in particular, in one of the two inbred lines.
Effects of Foliar‐Applied Ethylene Inhibitor and Synthetic Cytokinin on Creeping Bentgrass to Enhance Heat Tolerance
Authors: Xu Yan , Huang Bingru
Published: August 2009

Heat stress is a major factor causing leaf senescence and other physiological damages in cool‐season grass species. Cytokinins and ethylene are two major plant hormones affecting leaf senescence. The objective of this study was to determine whether foliar application of an ethylene synthesis inhibitor (aminoethoxyvinylglycine, AVG) and a synthetic cytokinin (trans‐zeatin riboside, t‐ZR) would enhance creeping bentgrass (Agrostis stolonifera L.) tolerance to heat stress associated with the suppression of leaf senescence. Creeping bentgrass ‘Penncross’ was exposed to either heat stress (35°C) or optimal growth temperature (20°C) for 35 d in growth chambers. Plants at each temperature were treated with 25 μM AVG, 25 μM t‐ZR or water (control). Foliar spray of AVG or zeatin riboside (ZR) solution resulted in increases in turf quality, leaf chlorophyll content, activities of antioxidant enzymes, and the reduction in lipid peroxidation, compared with water‐treated plants, for plants exposed to heat stress. In addition, foliar application of AVG suppressed ethylene evolution, whereas exogenous ZR resulted in elevated endogenous cytokinin levels under heat stress. The results suggest that the application of AVG or ZR suppressed leaf senescence and improved heat tolerance of creeping bentgrass, which could be because of their effects on endogenous production of ethylene and cytokinins and on antioxidant metabolism.
Introgressing White Mold Resistance from Phaseolus Species of the Secondary Gene Pool into Common Bean
Authors: Singh Shree P. , Terán Henry , Schwartz Howard F. , Otto Kristen , Lema Margarita
Published: August 2009

White mold (WM) caused by Sclerotinia sclerotiorum (Lib.) de Bary is a severe disease of common bean (Phaseolus vulgaris L.) in North America. Common bean has only partial resistance. However, some accessions of P. coccineus L. and other species of the secondary gene pool (SGP) are highly resistant. The objectives of this study were to (i) introgress WM resistance from the SGP and (ii) compare resistance of interspecific breeding lines (IBL) VCW 54 and VCW 55, developed by congruity backcrossing between ‘ICA Pijao’ and P. coccineus accession G 35172, and VRW 32, derived from recurrent backcrossing of ICA Pijao with P. costaricensis accession S 33720 with known sources of resistance. The three IBL, ICA Pijao, and susceptible (‘Othello’) and resistant (92BG‐7, A 195, G 122, I9365–25, ‘ICA Bunsi’, and VA 19) genotypes were screened in the greenhouse in Colorado and Idaho in 2007 and 2008 and in the field in Idaho in 2007. White mold resistance was successfully introgressed from two of the three Phaseolus species (P. coccineus and P. costaricensis) of the SGP. VCW 54 had the highest WM resistance, and VCW 55 and VRW 32 had similar resistance as previously reported. These sources of WM resistance should be introgressed into common bean cultivars.
Dry Bean Landrace and Cultivar Performance in Stressed and Nonstressed Organic and Conventional Production Systems
Authors: Singh Shree P. , Terán Henry , Muñoz‐Perea Carlos German , Lema Margarita , Dennis Marie , Hayes Richard , Parrott Richard , Mulberry Kenneth , Fullmer David , Smith Jay
Published: August 2009

High‐yielding cultivars adapted to stressed and nonstressed production systems (PS) would maximize efficiency of soil water and nutrient usage, compete well with weeds, resist diseases and insect pests, and reduce dependence on water, fertilizer, and pesticide. The objectives of this study were to (i) determine the performance of dry bean (Phaseolus vulgaris L.) landraces and cultivars across seven stressed and nonstressed PS, (ii) identify high‐yielding cultivars within and across PS, and (iii) determine associations among PS. Three landraces and 13 cultivars were evaluated for days to maturity, 100‐seed weight, and yield in 2003 and 2004. The PS and genotype effects and their interactions with years were significant (P < 0.01). The mean yield (740 kg ha−1), 100‐seed weight (28 g), and days to maturity (81 d) were least in the on‐farm organic low input (OFOL) PS. The greatest mean yield (2740 kg ha−1) was obtained in the on‐station conventional (OSCN) PS, while the greatest 100‐seed weight (35 g) and days to maturity (95) were obtained in the on‐farm low soil fertility (OFLF) PS. Red genotypes yielded more across all PS. ‘Bill Z’ in OSCN and on‐farm organic high‐input (OFOH) PS, ‘UI 239’ in on‐station continual bean production (OSCB), CO46348 in on‐station drought‐stressed production (OSDS), ‘Matterhorn’ in on‐farm conventional (OFCN), ‘NW 63’ in OFLF, and ‘Buster’ in OFOL had high yield. CO46348, UI 239, NW 63, and Bill Z had high yields across PS. Positive associations for yield in the OFCN occurred with yield across all PS except OFOL. The latter was not correlated with other PS. Thus, testing in the OFCN PS would be pivotal for development of high‐yielding cultivars for diverse PS, while testing at OFOL would need to be done for cultivars developed for use in that PS.
Transgenic Breeding: Perspectives and Prospects
Authors: Visarada K. B. R. S. , Meena Kanti , Aruna C. , Srujana S. , Saikishore N. , Seetharama N.
Published: August 2009

Transgenic technology serves to introduce gene sequences for expression of a desired trait. Production of transgenic plants is reported in many crops, but commercialization is limited to a few selected crops, such as cotton (Gossypium hirsutum L.), corn (Zea mays L.), soybean [Glycine max (L.) Merr.], and canola (Brassica napus L. and B. rapa L.). This paper presents the sequential processes of transgenic event design, event selection, and “cleaning up” genetic background for forward breeding programs. Expression of the foreign gene cannot be viewed in isolation and is more complex than has been assumed because of the interaction of transgene with native genes. Variations among clones and within the progeny are observed, and hence all the clones are taken into account for evaluation. Plant breeding must be involved to move transgenes from transformable but agronomically unacceptable genotypes into elite breeding lines with two backcrosses. Production of transgenic plants in large numbers is difficult and laborious and requires large investments. It is worthwhile investing in parallel efforts to incorporate the transgene into improved plant material to satisfy commercial interests.
The Associated Effects of the Soybean Aphid Resistance Locus Rag1 on Soybean Yield and Other Agronomic Traits
Authors: Kim Ki‐Seung , Diers Brian W.
Published: August 2009

The soybean aphid (Aphis glycines Matsumura) is a new invasive soybean [Glycine max (L.) Merr.] insect pest first identified in North America in 2000. A major aphid resistance gene Rag1 was identified and mapped from the maturity group VIII cultivar Dowling, and the gene has been introgressed into Midwest‐adapted germplasm. The objective of this study was to test the associated effects of Rag1 on yield and several important agronomic traits in two elite Midwest‐adapted soybean backgrounds. To do this, we tested two backcross populations that segregate for Rag1 with simple sequence repeat markers linked to the gene in field tests conducted in multiple environments with no detectable soybean aphid infestations. Across environments, Rag1 had no significant (P = 0.05) associated effects on yield, plant height, and lodging score in either population. However, Rag1 was significantly associated with a 2‐d delay in maturity in one population. This delay in maturity is likely caused by linkage drag between Rag1 and gene(s) that delayed maturity. These results indicate that breeders can incorporate Rag1 into Midwest‐adapted backgrounds without an associated yield reduction.
Linkage Maps of Wheat Stripe Rust Resistance Genes Yr5 and Yr15 for Use in Marker‐Assisted Selection
Authors: Murphy Lesley R. , Santra Dipak , Kidwell Kimberlee , Yan Guiping , Chen Xianming , Campbell Kimberly Garland
Published: August 2009

Stripe rust (caused by Puccinia striiformis Westend. f. sp. tritici Eriks.) is a serious disease of wheat (Triticum aestivum L.). Resistance genes Yr5 and Yr15 are the only known all‐stage resistance genes that defeat all stripe rust races currently found in the United States. Previously mapped markers for these genes, however, show limited polymorphism across diverse genotypes and/or map at a distance from the genes, reducing the effectiveness of marker‐assisted selection. Our objective was to create new linkage maps for both genes using sequence tagged site (STS) and simple sequence repeat (SSR) loci and to evaluate closely linked markers across a diverse panel of wheat genotypes. Two recombinant inbred populations created using Avocet‐Susceptible as a susceptible parent and Triticum aestivum L. ssp. spelta (L.) Thell. ‘Album’ and Triticum dicoccoides Koern. as the Yr5 and Yr15 donors, respectively, were evaluated for resistance to multiple races of stripe rust. Molecular markers that had been previously mapped to wheat chromosome 1B (Yr5) or 2B (Yr15) were mapped on the appropriate population. Markers most closely linked to each gene were evaluated against a panel of genotypes collected from active introgression programs in the United States. The Yr5 gene is flanked on the distal side by STS7/8 marker and by Xbarc349 and Xbarc167 on the proximal side, although none of these markers were diagnostic in all backgrounds. For Yr15, Xbarc8 and Xgwm413 appear to be completely linked with the gene in our population, along with resistance gene analog polymorphism marker Xwgp34. These two SSR markers also appear to be diagnostic in all backgrounds tested with one exception (Zak). We have developed linkage maps for both genes and identified several useful SSR and STS markers for introgression of Yr5 and Yr15
New and Diverse Sources of Multiple Disease Resistance in Wheat
Authors: Gurung Suraj , Bonman J. Michael , Ali Shaukat , Patel Jaimin , Myrfield Mary , Mergoum Mohamed , Singh Pawan K. , Adhikari Tika B.
Published: August 2009

Tan spot (caused by Pyrenophora tritici‐repentis) and Stagonospora nodorum blotch (SNB), (caused by Phaeosphaeria nodorum) are destructive diseases of wheat (Triticum aestivum L.). The majority of currently grown wheat varieties are susceptible to both diseases, presumably because of high pathogenic variability occurring in these fungi or narrow genetic background for resistance in wheat varieties. Therefore, identifying new sources of tan spot and SNB resistance in wheat is imperative. A subset of 825 wheat accessions from the core collection of the National Small Grains Collection (NSGC) of the United States Department of Agriculture, National Plant Germplasm System (NPGS) was evaluated for resistance to tan spot and SNB at seedling stage in a growth chamber. On the basis of disease reactions, 88 wheat accessions exhibited resistance to both diseases. Data from the Germplasm Resources Information Network (GRIN) were examined for the 88 accessions to identify those that also have resistance to other key diseases and on this basis 28 accessions with multiple resistances were identified. The genetic relationship among the 88 accessions was assessed using resistance gene analog polymorphism (RGAP) primers. Wheat accessions with similar growth habit were grouped together despite differences in country of origin. Associations between agronomic traits and host resistance indicated that winter wheat habit in the studied collection was strongly associated with both SNB and tan spot resistance. This study identified genetically diverse wheat accessions with broad‐spectrum resistance that can be used in developing cultivars with high levels of resistance to multiple diseases in wheat breeding programs.
Identification of QTL Conferring Resistance to Fusarium Head Blight Resistance in the Breeding Line C93‐3230‐24
Authors: Lamb Kenneth E. , Gonzalez‐Hernandez Jose L. , Zhang Bingxin , Green Marci , Neate Stephen M. , Schwarz Paul B. , Horsley Richard D.
Published: August 2009

Control of Fusarium head blight (FHB), incited primarily by Fusarium graminearum Schwabe [telomorph Gibberella zea (Schwein)], has been a challenge for barley (Hordeum vulgare L.) producers in the upper midwestern United States for more than a decade. This disease manifests primarily in the form of food safety issues and quality discounts due to the presence of deoxynivalenol (DON), a mycotoxin produced by the pathogen. Cultural practices and fungicides only provide partial control; genetic resistance to FHB and DON accumulation may add to control of the disease. Field studies in North Dakota and China were conducted in FHB disease nurseries using 118 double‐haploid lines from the cross C93‐3230‐24/‘Foster’. Foster is susceptible to FHB, and C93‐3230‐24 is moderately resistant. The quantitative trait locus (QTL) analysis revealed five putative QTL for Type I FHB resistance; however, only the one in bins 7 and 8 of chromosome 2H was detected in more than 70% of the environments. In addition, QTL associated with late days to heading and maturity and tall plant height also were located in the same region. Three putative QTL for increased DON accumulation were detected; however, none were detected in more than three of the eight environments where data were collected. On the basis of these results, it is unlikely that C93‐3230‐24 has a novel QTL for FHB resistance different from those identified in other resistant accessions. However, C93‐3230‐24 is unique in that it provides QTL for improved FHB resistance but not reduced DON accumulation. This is an atypical response compared with other sources of FHB resistance and provides evidence that FHB resistance and DON accumulation are under separate genetic control.
Yield and Water Use Response of Cuphea to Irrigation in the Northern Corn Belt
Authors: Gesch R. W. , Sharratt B. S. , Kim K.‐I.
Published: August 2009

Cuphea (Cuphea viscosissimaJacq. ×C. lanceolataW.T. Aiton) may be prone to drought stress, yet little is known about the yield response of this new oilseed crop to irrigation. A field study was conducted in western Minnesota on a Barnes loam soil (fine‐loamy, mixed, superactive, frigid Calcic Hapludolls) in 2002 and 2003 to compare yield and water use of irrigated and nonirrigated cuphea. Nonirrigated cuphea received only precipitation, while irrigated plants received supplemental watering to maintain soil water content near field capacity during the study. Crop drought stress was assessed by measuring photosynthesis, stomatal conductance, leaf water potential, and δ13C (13C/12C stable isotope composition). In 2002, soil water content was similar for irrigated and nonirrigated plants throughout the growing season owing to timely rains, and seed yield was similar between treatments (873 kg ha−1). During 2003, irrigation resulted in a 2.7‐fold increase in seed yield and greater harvest index than nonirrigated plants, while water use efficiency (WUE) of seed production for both treatments was similar (2.4 kg ha−1mm−1). Drought conditions occurred in 2003; by mid‐August, leaf photosynthesis and leaf water potential of nonirrigated plants were 83 and 56% less, respectively, than for irrigated cuphea. Moreover, δ13C measurements of seed further confirmed that nonirrigated cuphea suffered significant drought stress. Our results indicate that cuphea is drought sensitive and that regions or soils prone to water deficits will likely require supplemental irrigation to increase seed yield.
Biplot Analysis of Genotype × Environment Interaction: Proceed with Caution
Authors: Yang Rong‐Cai , Crossa Jose , Cornelius Paul L. , Burgueño Juan
Published: August 2009

Biplot analysis has been used for studying genotype × environment interaction (GE) or any two‐way table. Its descriptive and visualization capabilities along with the availability of user‐friendly software have enabled plant scientists to examine any two‐way data by a click on a computer button. Despite widespread use, the validity and limitations of biplot analysis have not been completely examined. Here we identify and briefly discuss six key issues surrounding overutilization or abuse of biplot analysis. We question (i) whether the retention of the first two multiplicative terms in the biplot analyses is adequate; (ii) whether the biplot can be more than a simple descriptive technique; (iii) how realistic a “which‐won‐where” pattern is identified from a biplot; (iv) what if genotypes and/or environments are random effects; (v) how relevant biplot analysis is to the understanding of the nature and causes of interaction; and (vi) how much the biplot analysis can contribute to detection of crossover interaction. We stress the need for use of confidence regions for individual genotype and environment scores in biplots to make critical decisions on genotype selection or cultivar recommendation based on a statistical test. We conclude that the biplot analysis is simply a visually descriptive statistical tool and researchers should proceed with caution if using biplot analysis beyond this simple function.
DNA Polymorphisms of Genes Involved in Fiber Development in a Selected Set of Cultivated Tetraploid Cotton
Authors: Lu Yingzhi , Curtiss Jessica , Percy R. G. , Hughs S. E. , Yu Shuxun , Zhang Jinfa
Published: August 2009

The lack of genetic diversity within cultivated upland cotton (Gossypium hirsutum L.) has hindered the construction of genomewide linkage maps and their applications in genetics and breeding. The objective of this investigation was to develop candidate gene markers for fiber quality and yield on the basis of approximately 90 genes implicated in fiber development. Polymorphisms using sequence‐tagged site (STS) and single nucleotide polymorphism (SNP) markers based on single strand conformation polymorphism (SSCP) and cleaved amplified polymorphism (CAP) were evaluated among three upland and five Pima cotton (G. barbadense L.) genotypes. Of the 90 primer pairs, 75 resulted in polymerase chain reaction amplifications, including 11 that yielded polymorphic STS markers. Of the 48 primer pairs that produced polymorphic SSCP markers, 27 yielded interspecific polymorphism, while 15 yielded both inter‐ and intraspecific polymorphisms. Six pairs yielded only intraspecific polymorphisms. A total of 18 SNPs, including four indels, were identified in seven of the 15 fiber gene fragments on the basis of direct DNA sequencing, and the average length was 350 bp, with a mean of 1.3 SNPs per fragment. The average rate of SNPs per nucleotide was 0.34%, and 0.31% and 0.41% in coding and noncoding regions, respectively. Eight of the 15 SNPs were interspecific and 78% were nucleotide substitutions, with the four indels contributing to interspecific polymorphism. Six selected SNPs were confirmed by restriction enzyme digestion. The high level of SSCP polymorphism observed within a selected set of agronomically improved lines of upland cotton suggests that the use of SSCP will greatly facilitate genomewide mapping in upland cotton.
Photosynthetic Responses of Bermudagrass to Drought Stress Associated with Stomatal and Metabolic Limitations
Authors: Hu Longxing , Wang Zhaolong , Huang Bingru
Published: August 2009

Plants may survive drought stress by altering photosynthetic metabolism. This study was designed to investigate stomatal and metabolic changes associated with photosynthetic responses to drought for bermudagrass. A hybrid bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt Davy, cv. Tifway] and a common bermudagrass (C. dactylon, cv. C299) were subjected to drought by withholding irrigation in growth chambers. Tifway maintained higher relative water content and lower electrolyte leakage than C299 under drought. Net photosynthetic rate (Pn) and stomatal conductance (gs) decreased, with more rapid decline in C299, but Pn was significantly greater in Tifway than in C299, while gs did not differ between the two genotypes during 14 d of drought. Photochemical efficiency, ribulose‐1,5‐bisphosphate carboxylase:oxygenase (Rubisco) activity, and activation state declined during drought stress, but were higher in Tifway than in C299 within 14 d of treatment. Electrophoretic analysis revealed that at 14 and 18 d of drought, pyruvate orthophosphate dikinase (98 kDa) and Rubisco protein (49 kDa) exhibited severe degradation in C299 but to a lesser extent in Tifway. These results indicated that the superior drought resistance in Tifway could be attributed to higher photosynthetic capacity through the maintenance of higher metabolic activities, as manifested by more active Rubisco enzyme and Rubisco activase and more stable photosynthetic proteins.
Sources of Soybean Rust Resistance Challenged with Single‐Spored Isolates of Phakopsora pachyrhizi
Authors: Paul C. , Hartman G. L.
Published: August 2009

Soybean rust, caused by the fungus Phakopsora pachyrhizi Syd., is a potentially devastating disease that can cause significant yield losses. Resistance in soybean [Glycine max (L.) Merr.] germplasm, both qualitative and quantitative, may be effective in providing at least partial control of soybean rust. A number of soybean genotypes have resistance to soybean rust, but few of these have been challenged with the recently recovered U.S. isolates. The objective of this study was to evaluate known sources of soybean rust resistance against U.S. isolates of P. pachyrhizi Twenty‐eight soybean genotypes that either contained known major‐genes for resistance or had been reported as new sources of soybean rust resistance, along with two susceptible checks, were challenged with six P. pachyrhizi isolates collected in the U.S. All six isolates produced similar phenotypic reactions within each of the genotypes. Five genotypes, including the Rpp1 source and the isoline of ‘Williams 82’ with Rpp1, had no visible lesions. Eleven genotypes produced red‐brown lesions with few uredinia, including the sources of Rpp2 and Rpp3, and the remainder had susceptible tan lesions, including the source of resistance for Rpp4 Uredinial counts from genotypes producing red‐brown lesions on live and fixed leaflets showed significant variation in the number of uredinia with a genotype × isolate interaction. Uredinial counts from genotypes producing tan lesions on live and fixed leaflets showed significant variation in the number of uredinia among genotypes, but there was no genotype × isolate interaction. There were significant correlations (r = 0.8, P < 0.0001; and r = 0.4, P < 0.0001) between uredinial counts based on live and fixed leaflets within genotypes producing red‐brown lesions and those producing tan lesions, respectively.
Rapid Microwave Processing of Winter Cereals for Histology Allows Identification of Separate Zones of Freezing Injury in the Crown
Authors: Livingston D. P. , Tuong T. D. , Haigler C. H. , Avci U. , Tallury S. P.
Published: August 2009

In histological studies, microwave processing of tissue considerably shortens the time required to prepare samples for observation under light and electron microscopy. However, plant tissues from different species and different regions of the plant respond differently to microwave processing, making it impossible to use a single protocol for all plant tissue. The crown of winter cereals such as rye (Secale cereale L.), wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), and oats (Avena sativa L.) is the below‐ground portion of the stem that overwinters. It is composed of numerous types of cells with an organizational pattern that is similar to other grasses. When we used microwave protocols that were developed for other plant tissues, winter cereal crown tissue shattered and crumbled when sectioned. This study reports a procedure developed to process winter cereal crowns for histological observations. Using this microwave protocol, samples were prepared in 1 d as compared to 2 wk using traditional protocols. This enabled many more samples to be processed and allowed us to identify four overlapping zones of response to freezing within the crown. Results of varying time, temperature, and microwave wattage during fixing, dehydrating, and embedding in paraffin are described. High quality sections from the crowns of oat, barley, wheat, and rye indicate that this procedure is valid for all winter cereals. Since crown tissue is similar across all grass species, we predict that the protocol will be useful for other grasses as well.
Solute Spreading under Transient Conditions in a Field Soil
Authors: Kasteel Roy , Pütz Thomas , Vanderborght Jan , Vereecken Harry
Published: August 2009

Lateral mass redistribution in soils is the key to understanding field‐scale solute transport, but the underlying assumptions of common transport theories are violated under transient‐flow conditions. We tested the applicability of two limiting cases for solute spreading under transient‐flow conditions in the field after an appropriate time coordinate transformation: no lateral mass redistribution, described by the convective‐lognormal transfer function (CLT), vs. perfect lateral mass redistribution, described by the convection–dispersion equation (CDE). A Br− transport experiment was performed in six zero‐tension lysimeters and in the field for almost 3 yr under atmospheric conditions. Sampling in the field was performed by extracting soil cores during seven campaigns. According to time‐domain reflectometry readings, only slight variations in water content were measured in space and time in the lysimeters. In contrast, water content was lower and more variable in the plow layer in the field. The variance of solute spreading was better predicted by the CDE assuming perfect lateral mass redistribution. This hints at the importance of molecular diffusion. Both models have the flexibility to fit the flux‐averaged breakthrough curve in the lysimeters and the averaged concentration profiles in the field, but not with one set of parameters. The CLT parameters obtained from the lysimeter experiment better predicted the measured concentration profiles in the field for shorter times, but both models failed for longer times. Due to the occurrence of local saturation at the lower boundary of zero‐potential lysimeters, differences in water regimes hamper the transferability of transport parameters from lysimeters to the field.
Degradation of Diffuse Pesticide Contaminants: Screening for Microbial Potential Using a Functional Gene Microarray
Authors: Liebich Jost , Wachtmeister Thorsten , Zhou Jizhong , Burauel Peter
Published: August 2009

Recently, a functional gene array—GeoChip—was introduced, targeting more than 12,000 different microbial functional genes. In addition to microbial genes involved in widespread microbial functions, this array also includes 37 probes for genes involved in atrazine [6‐chloro‐N‐ethyl‐N′‐(1‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine] degradation. In our study, we evaluated whether this type of microarray is suitable for screening a rural aquifer for native atrazine degraders and their intrinsic degradation capacities. Surprisingly, small amounts of organic contaminants (up to ∼10 μg/L) in a well close to a farmyard led to the establishment of a specific degrader community. This means that although contamination at such low concentrations should have only a minor effect on water quality, the microbial community in this oligotrophic environment reacted in a very sensitive manner to the contaminants. Specific atrazine degradation genes were detected in the aquifer showing the highest level of contamination. Their presence was confirmed using a specially developed polymerase chain reaction approach combined with gene sequence analysis. Whether this should be considered an undesired ecotoxicological effect or whether it should be taken as evidence for regular natural attenuation of such diffuse contaminants is a question that remains to be answered by more comprehensive studies.
Simultaneous Laboratory Measurement of Acoustic and Hydraulic Properties of Unsaturated Soils
Authors: George Lindsay A. , Dewoolkar Mandar M. , Znidarcic Dobroslav
Published: August 2009

Complete sets of acoustic properties (compressional and shear wave velocities and attenuations) and hydraulic properties (the soil water characteristic curve and the unsaturated hydraulic conductivity function) were determined across a full range of water contents for two types of soil specimens. The acoustic and hydraulic data were collected using a novel device developed at the University of Vermont. The acoustic data were collected using a Kelly wavelet with a center frequency of 20 kHz. The measured acoustic velocities and attenuations across a full range of water contents were consistent with similar measurements found in the literature and made in rock specimens. The experimental data reported here can be used to verify analytical models that attempt to link acoustic and hydraulic properties of unconsolidated and unsaturated porous media.
Characterization and Estimation of Hydraulic Properties in an Alluvial Gravel Vadose Zone
Authors: Dann R. , Close M. , Flintoft M. , Hector R. , Barlow H. , Thomas S. , Francis G.
Published: August 2009

Understanding the physical and hydraulic properties of the vadose zone is important for modeling land use effects on groundwater quality. This study used a variety of characterization methods to derive conceptual understanding and estimates of hydraulic properties of a coarse alluvial gravel vadose zone in New Zealand. Sandy gravel (SG) material constituted approximately 90% of the vadose zone, with the remainder comprising sand lenses and open‐framework gravels. The gravel content of the SG material was approximately 70% (v/v) (range 68–73%). The water content of the bulk SG material (43 samples) ranged from 3.5 to 13.9%. The average bulk density of the SG material was 2.20 g/cm3 (range 2.00–2.33 g/cm3) giving an average calculated porosity of 17%. The average porosity of the open‐framework gravels was 34% and these gravels were often coated with 2‐ to 3‐mm‐thick deposits of amorphous Fe and Mn oxides. Neutron probe (NP) depth profiles indicated unsteady conditions, with variable water contents with depth and time reflecting the vertical heterogeneity and the variably saturated state of the vadose zone. Time series NP data to 3 m indicated water content in the alluvial gravels responded quickly to soil drainage events, and saturation variability was greater in the sand lenses and the SG material immediately underlying. When compared with derived water retention curves, variability in the water content equated to significant fluctuation in unsaturated hydraulic conductivity (Kunsat). Tension infiltrometer measurements were variable but were within the range of the Kunsat estimates from site‐average particle size distribution data. The gravel‐transformed, texture‐based models used to estimate saturated water content values in this study appeared to underestimate the measured values.
Diffuse subsurface zinc loads from mining areas in the Dalälven River Basin, Sweden
Authors: Baresel Christian , Destouni Georgia
Published: August 2009

The zinc load from the Dalälven River to the Baltic Sea is greater than for any other watercourse in Sweden. This paper investigates zinc mass flows into and through the Dalälven River from major mining areas within its drainage basin. Reported zinc mass flow data for this river are re-analyzed using an input-output flow analysis approach. Results show major inconsistencies in previous data interpretations which totally neglected possible zinc mass load contributions from the groundwater system to the river. This paper quantifies significant subsurface zinc load contributions that are consistent with all independently available data. Furthermore, a possible explanation for why these subsurface contributions may have been missed in previous studies and by the prevailing Swedish environmental monitoring system is provided. The study indicates that the input-output flow analysis approach may be generally useful for identifying and quantifying diffuse, unmonitored and uncertain pollutant load contributions from ground- to surface water systems.