bluuebunny/crossref_metadata_2025 huggingface dataset:
An Interrelationship Between Autophagy and Filamentous Growth in Budding Yeast
Authors: Ma Jun , Jin Rui , Jia Xiaoyu , Dobry Craig J , Wang Li , Reggiori Fulvio , Zhu Ji , Kumar Anuj
Published: September 2007

Over the last 15 years, yeast pseudohyphal growth (PHG) has been the focus of intense research interest as a model of fungal pathogenicity. Specifically, PHG is a stress response wherein yeast cells deprived of nitrogen form filaments of elongated cells. Nitrogen limitation also induces autophagy, a ubiquitous eukaryotic stress response in which proteins are trafficked to the vacuole/lysosome for degradation and recycling. Although autophagy and filamentous growth are both responsive to nitrogen stress, a link between these processes has not been investigated to date. Here, we present several studies describing an interrelationship between autophagy and filamentous growth. By microarray-based expression profiling, we detect extensive upregulation of the pathway governing autophagy during early PHG and find both processes active under conditions of nitrogen stress in a filamentous strain of budding yeast. Inhibition of autophagy results in increased PHG, and autophagy-deficient yeast induce PHG at higher concentrations of available nitrogen. Our results suggest a model in which autophagy mitigates nutrient stress, delaying the onset of PHG; conversely, inhibition of autophagy exacerbates nitrogen stress, resulting in precocious and overactive PHG. This physiological connection highlights the central role of autophagy in regulating the cell's nutritional state and the responsiveness of PHG to that state.
Evolution of Gene Sequence in Response to Chromosomal Location
Authors: Díaz-Castillo Carlos , Golic Kent G
Published: September 2007

Evolutionary forces acting on the repetitive DNA of heterochromatin are not constrained by the same considerations that apply to protein-coding genes. Consequently, such sequences are subject to rapid evolutionary change. By examining the Troponin C gene family of Drosophila melanogaster, which has euchromatic and heterochromatic members, we find that protein-coding genes also evolve in response to their chromosomal location. The heterochromatic members of the family show a reduced CG content and increased variation in DNA sequence. We show that the CG reduction applies broadly to the protein-coding sequences of genes located at the heterochromatin:euchromatin interface, with a very strong correlation between CG content and the distance from centric heterochromatin. We also observe a similar trend in the transition from telomeric heterochromatin to euchromatin. We propose that the methylation of DNA is one of the forces driving this sequence evolution.
The Persistence of Parasitic Plasmids
Authors: Lili Loukia N , Britton Nicholas F , Feil Edward J
Published: September 2007

The conditions under which plasmids are predicted to persist remain controversial. Here, we reevaluate the ordinary differential equations used previously to model plasmid persistence and conclude that the parameter space required for maintenance is far less stringent than has been supposed. Strikingly, our model demonstrates that purely parasitic plasmids may persist, even in the absence of heterogeneity in the host population, and that this persistence is expressed by oscillations or damped oscillations between the plasmid-bearing and the plasmid-free class.
Transplantation of Embryonic Stem Cell-Derived Endodermal Cells into Mice with Induced Lethal Liver Damage
Authors: Ishii Takamichi , Yasuchika Kentaro , Machimoto Takafumi , Kamo Naoko , Komori Junji , Konishi Sayuri , Suemori Hirofumi , Nakatsuji Norio , Saito Michiko , Kohno Kenji , Uemoto Shinji , Ikai Iwao
Published: September 2007

ESCs are a potential cell source for cell therapy. However, there is no evidence that cell transplantation using ESC-derived hepatocytes is therapeutically effective. The main objective of this study was to assess the therapeutic efficacy of the transplantation of ESC-derived endodermal cells into a liver injury model. The β-galactosidase-labeled mouse ESCs were differentiated into α-fetoprotein (AFP)-producing endodermal cells. AFP-producing cells or ESCs were transplanted into transgenic mice that expressed diphtheria toxin (DT) receptors under the control of an albumin enhancer/promoter. Selective damage was induced in the recipient hepatocytes by the administration of DT. Although the transplanted AFP-producing cells had repopulated only 3.4% of the total liver mass 7 days after cell transplantation, they replaced 32.8% of the liver by day 35. However, these engrafted cells decreased (18.3% at day 40 and 7.9% at day 50) after the cessation of DT administration, and few donor cells were observed by days 60–90. The survival rate of the AFP-producing cell-transplanted group (66.7%) was significantly higher in comparison with that of the sham-operated group (17.6%). No tumors were detected by day 50 in the AFP-producing cell-transplanted group; however, splenic teratomas did form 60 days or more after transplantation. ESC transplantation had no effect on survival rates; furthermore, there was a high frequency of tumors in the ESC-transplanted group 35 days after transplantation. In conclusion, this study demonstrates, for the first time, that ESC-derived endodermal cells improve the survival rates after transplantation into mice with induced hepatocellular injury.

Disclosure of potential conflicts of interest is found at the end of this article.
Trinexapac‐Ethyl Application Regimens Influence Growth, Quality, and Performance of Bermuda Grass and Creeping Bentgrass Putting Greens
Authors: McCullough Patrick E. , Liu Haibo , McCarty Lambert B. , Toler Joe E.
Published: September 2007

Dwarf bermudagrass (Cynodon dactylon×C. transvaalensisBurtt‐Davy) and creeping bentgrass (Agrostis stoloniferaL.) are planted for golf greens in the U.S. transition zone, but management regimes, such as the use of a plant growth regulator (PGR), often vary for long‐term culture of the two species. The objective of this experiment was to investigate application regimens of the PGR trinexapac‐ethyl (TE), on growth, quality, and performance of creeping bentgrass and bermudagrass putting greens in Clemson, SC. ‘L‐93’ creeping bentgrass and ‘TifEagle’ bermudagrass putting greens, established in summer 2002 and mowed at 3.2 mm, received TE over 12 wk in three regimens: 0.017 kg ha−1wk−1, 0.033 kg ha−12 wk−1(biweekly), or 0.05 kg ha−13 wk−1(triweekly) from May to August 2003 and 2004. Creeping bentgrass was not discolored from TE, but unacceptable bermudagrass discoloration (>20%) occurred on one, two, and six dates for weekly, biweekly, and triweekly regimens, respectively. All TE regimens reduced bermudagrass clippings approximately 50% from nontreated bermudagrass across all dates, while creeping bentgrass clipping reductions, approximately 20 to 35% from nontreated grass, were inconsistent. The root masses of both species treated with TE regimens were similar to nontreated turf. Bermudagrass aerification recovery was reduced on two, two, and four dates after weekly, biweekly, and triweekly TE regimens, respectively. All TE regimens increased morning and evening bermudagrass golf ball roll distance approximately 25 cm from morning distances of nontreated turf.
Assignment Tests for Variety Identification Compared to Genetic Similarity‐Based Methods Using Experimental Datasets from Different Marker Systems in Sugar Beet
Authors: De Riek J. , Everaert I. , Esselink D. , Calsyn E. , Smulders M. J. M. , Vosman B.
Published: September 2007

High genetic variation within sugar beet (Beta vulgaris L.) varieties hampers reliable classification procedures independent of the type of marker technique applied. Datasets on amplified fragment length polymorphisms, sequence tagged microsatellite sites, and cleaved amplified polymorphic sites markers in eight sugar beet varieties were subjected to supervised classifiers, methods in which individual assignments are made to predefined classes, and unsupervised classifiers, defined afterward on the similarity in marker composition from sampled individuals. Major issues addressed are (i) which classification method gives the most consistent results when three marker techniques are compared, and (ii) given different classification techniques available, for which marker technique is the output generated least constrained by the way data analysis is performed. Assignment tests showed a higher consistency across classifications independent from the marker technique. A good allocation to the proper variety was obtained, together with a reliable allocation pattern among the other varieties. Both aspects deal with the variation within a variety and the distance to other varieties. Assignment data were transformed into an average similarity measure, similarity by assignment (Sax,y), which is a new genetic distance measure with interesting properties.
Effects of Trinexapac‐Ethyl Foliar Application on Creeping Bentgrass Responses to Combined Drought and Heat Stress
Authors: McCann Stephen E. , Huang Bingru
Published: September 2007

Simultaneous drought and heat stress is detrimental to turfgrass growth. Growth regulators may influence plant responses to stresses. The objective of this study was to determine effects of pretreatment with trinexapac‐ethyl (TE) on creeping bentgrass (Agrostis stoloniferaL.) responses to subsequent exposure to combined heat and drought stress. Plants were treated with TE (1.95 mL L−1[v/v], Primo Maxx) every 14 d for 42 d and then exposed to combined drought and heat (35°C) in growth chambers. Application of TE increased turf quality and relative water content and chlorophyll content during 21 d of stress. Trinexapac‐ethyl–treated plants had increased growth rate and maintained constant canopy photosynthetic rate (Pn) and photochemical efficiency (Fv/Fm) during the stress period, while these parameters declined for the untreated control. Trinexapac‐ethyl–treated plants maintained lower evapotranspiration rate (ET) under nonstressed control conditions, but higher ET at 21 d of stress. Trinexapac‐ethyl–treated plants showed no differences from untreated plants in osmotic adjustment, and had lower levels of total nonstructural carbohydrates during the stress period. The study suggests that TE application enhanced turf performance under stress, as demonstrated by maintenance of higher turf quality and growth rate during a prolonged period of com bined stress. The beneficial effects of TE on bentgrass stress responses could be related to the maintenance of photosynthetic activities and greater level of cellular hydration. These and other published data indicate that use of TE on creeping bentgrass that seasonally experiences heat and drought stresses could benefit its performance.
Chalkiness in Rice: Potential for Evaluation with Image Analysis
Authors: Yoshioka Yosuke , Iwata Hiroyoshi , Tabata Minako , Ninomiya Seishi , Ohsawa Ryo
Published: September 2007

Chalkiness is a major concern in rice (Oryza sativa L.) breeding because it is one of the key factors in determining quality and price. Evaluation of chalkiness is traditionally performed by human visual inspection, and there is no standard objective method to effectively classify chalky grains into different categories. In this study, we evaluated the effectiveness of image information processing with an inexpensive personal computer and a digital image scanner to measure and categorize chalkiness and assessed the method's viability as an alternative to human visual assessment. A support vector machine based on the image data generated an accuracy rate of 90.2% in discriminating the level of chalkiness, and principal‐components analysis of the image data provided new quantitative variables related to the location and degree of chalkiness with much greater accuracy than was previously possible. These results indicate that image processing may be a useful tool for evaluating the chalkiness of rice in scientific research and breeding programs.
Correlation between Heat Stability of Thylakoid Membranes and Loss of Chlorophyll in Winter Wheat under Heat Stress
Authors: Ristic Zoran , Bukovnik Urska , Prasad P.V. Vara
Published: September 2007

Determining mechanisms associated with heat tolerance and identifying screening methods are vital for improvement of heat tolerance in plants. The objectives of this study were to investigate the relationship between the heat stability of thylakoids and loss of chlorophyll in winter wheat (Triticum aestivum L.) under heat stress, and to examine whether chlorophyll loss can be used as an indicator of heat tolerance in wheat. We assessed heat tolerance and measured chlorophyll content in 12 cultivars of winter wheat at flowering stage during exposure to 16‐d‐long heat stress. Heat tolerance was assessed using fluorescence to determine the heat stability of thylakoids, and chlorophyll content was measured with a chlorophyll meter. Experiments were conducted under controlled conditions. Heat stress caused damage to thylakoids in all cultivars as indicated by the increase in the ratio of constant fluorescence (O) and the peak of variable fluorescence (P). Heat stress also caused a decline in chlorophyll content in most cultivars. A strong negative correlation between heat‐induced increases in O/P and chlorophyll content was seen. The results suggest that heat‐induced damage to thylakoids and chlorophyll loss are closely associated in winter wheat. Measurements of chlorophyll content with a chlorophyll meter could be useful for high throughput screening for heat tolerance in wheat.
Response of Low Seed Phytic Acid Soybeans to Increases in External Phosphorus Supply
Authors: Israel D. W. , Kwanyuen P. , Burton J. W. , Walker D. R.
Published: September 2007

Commercialization of soybean [Glycine max (L.) Merr.] varieties with low seed phytic acid will depend on the stability of the trait when grown in soils with a wide range of P availabilities and on the impact of altered P composition on seed protein and oil concentrations. Impacts of deficient (0.05 mmol L−1) to excessive (0.9 to 1.2 mmol L−1) levels of external P on seed P composition of normal and low phytic acid lines and of altered seed P composition on seed protein and oil synthesis were evaluated. Soybean lines homozygous recessive (pha/pha) at one of two loci with genes that condition the low seed phytic acid trait had the same greater‐than‐threefold increase in phytic acid in response to increasing external P as their normal phytic acid parent, ‘AGS Prichard‐RR’ (Pha/Pha). This supports the conclusion from previous inheritance studies that the low seed phytic acid trait in CX1834‐1‐2 is controlled by epistatic interaction between two independent recessive genes. The seed phytic acid concentration in the low phytic acid line G03PHY‐443 (derived from CX1834‐1‐2) was <2 g phytic acid P kg−1 dry wt. when grown under deficient to excessive external P. As the P supply increased, seed inorganic P concentrations for this line increased from 0.8 to 4.0 g kg−1 dry wt., compared to an increase of 0.2 to 0.6 g kg−1 dry wt. for the normal phytic acid lines. Seed protein and oil concentrations did not differ significantly between normal and low phytic acid lines. These results support continued development of varieties with low seed phytic acid and high yields.
Differences in Freeze Tolerance of Zoysiagrasses: I. Role of Proteins
Authors: Patton Aaron J. , Cunningham Suzanne M. , Volenec Jeffrey J. , Reicher Zachary J.
Published: September 2007

Genotypic variation in winter injury exists among zoysiagrasses (Zoysia spp.), but the physiological basis for these differences is not understood. Our objective was to determine the relationships between protein accumulation, polypeptide composition, and freeze tolerance of zoysiagrass. Thirteen genotypes of zoysiagrass with contrasting cold hardiness were identified. Cold acclimation was induced with 4 wk of 8/2°C day/night cycles and a 10‐h photoperiod of 300 μmol m−2 s−1 Rhizomes and stolons of zoysiagrass were harvested from nonacclimated and cold‐acclimated plants and used for protein analysis. Protein composition was analyzed using sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS‐PAGE) and immunoblotting with an antidehydrin polyclonal antibody. Buffer‐soluble protein concentrations were higher among cold‐acclimated (7.3 g kg−1 dry wt.) than nonacclimated (5.1 g kg−1 dry wt.) plants. The SDS‐PAGE analysis indicated few differences in polypeptide composition among genotypes irrespective of cold acclimation. Immunoblotting indicated that dehydrin polypeptides (23 and 25 kDa) increased during cold acclimation. Abundance of the 23‐kDa dehydrin polypeptide was positively associated (r2 = 0.41) with genetic variation in freezing tolerance. Our results suggest that dehydrins are associated with zoysiagrass cold acclimation, but that only the 23‐kDa dehydrin plays a role in improving freeze tolerance.
Differences in Freeze Tolerance of Zoysiagrasses: II. Carbohydrate and Proline Accumulation
Authors: Patton Aaron J. , Cunningham Suzanne M. , Volenec Jeffrey J. , Reicher Zachary J.
Published: September 2007

Cold hardiness among zoysiagrass (Zoysia spp.) genotypes varies, but the physiological basis for cold hardiness is not completely understood. The objective of this study was to determine the relationship of carbohydrate (starch, total soluble sugars, total reducing sugars, sucrose, glucose, and raffinose family oligosaccharides) and proline concentrations with the cold acclimation of zoysiagrass and the lethal temperature killing 50% of the plants (LT50). Thirteen genotypes of zoysiagrass were selected with contrasting levels of winter hardiness. Plants were grown for 4 wk of 8/2°C day/night cycles and a 10‐h photoperiod of 300 μmol m−2 s−1 to induce cold acclimation. Rhizomes and stolons were sampled from nonacclimated and cold‐acclimated plants and used for carbohydrate and proline analysis. Concentrations of soluble sugars and proline increased during cold acclimation, while starch concentrations decreased. Starch, sugar/starch ratio, glucose, total reducing sugars, and proline in cold‐acclimated plants were correlated (r = 0.61, −0.67, −0.73, −0.62, and −0.62, respectively) with LT50 These correlations indicate that higher concentrations of total reducing sugars, glucose, and proline are positively associated with zoysiagrass freeze tolerance, whereas higher concentrations of starch appeared detrimental to freeze tolerance.
Within‐Boll Yield Components of High Yielding Cotton Cultivars
Authors: Bednarz Craig W. , Nichols Robert L. , Brown Steve M.
Published: September 2007

Cotton (Gossypium hirsutum L.) within‐boll yield components have changed throughout the last 30 yr of cultivar development. The question arises, how do within‐boll yield components differ in contemporary high yielding cultivars? Nine commercially available cotton cultivars were over‐seeded and hand‐thinned to 10.8 plants m−2 in 2001, 2002, and 2003. Before machine harvest, plants from 6 m of one row were removed from each plot and hand‐harvested by fruiting position. After hand‐harvest, seed cotton from each fruiting position was ginned separately. Boll number, lint mass, seed number, seed mass, seed surface area, and fiber properties were determined for each fruiting position. These data were then used for within‐boll yield component calculations. One of the top yielding cultivars in this investigation (DPL 33 B), characterized by a smaller seed mass, produced greater total seed surface area per unit of land area, but lower lint mass and fiber number per unit of seed surface area. The other two top yielding cultivars in this investigation (DPL 491 and STV 4892 BR), characterized by a larger seed mass, produced lower total seed surface area per unit of land area, but greater lint mass and fiber number per unit of seed surface area. These data indicate fiber number and lint mass per unit of seed surface area are linked to seed size, which should be considered when selecting for increased lint mass or fiber number per unit of seed surface area.
Expansion of PCR‐based Marker Resources in Oat by Surveying Genome‐Derived SSR Markers from Barley and Wheat
Authors: Hu Gongshe , Jackson E.W. , Bonman J. Michael
Published: September 2007

Identifying polymerase chain reaction (PCR)‐based markers in crop genomes and amplifying them with specific primer pairs has provided convenient molecular markers for mapping projects. Oat (Avena sativa L.) lags behind other crops in the utilization of PCR‐based markers due to limited development of genomic and genetic resources in Avena species. We surveyed 356 genome‐derived simple sequence repeat (SSR) markers from wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.), chosen on the basis of even dispersal across different chromosomes, to search for an alternate method of expanding the PCR‐based marker pool in oat. Primer pairs for these SSR markers were tested for amplification and polymorphism between parental lines from Ogle1040/TAM‐O‐301 (OT) and Kanota/Ogle157 (KO) mapping populations. Eighty‐nine of 210 wheat primer pairs (42%) and 56 of 146 barley primer pairs (38%) successfully amplified sequences in oat. Forty‐five percent of the amplified markers, representing 19% of the total markers, showed polymorphism between parental lines of at least one mapping population. The polymorphism was primarily the presence or absence of a product band. Fifteen PCR products from 10 primer pairs were tested for reproducibility by amplifying each marker in the OT population. When assayed with the same PCR conditions used in the survey, the segregation ratio of 14 markers did not differ from the 1:1 ratio expected for a single locus. This study indicates that genomic SSR primer pairs from wheat and barley may be a good way to efficiently generate PCR‐based DNA markers for oat genetics research.
Evaluation of Nicotiana tabacum Genotypes Possessing Nicotiana africana‐derived Genetic Tolerance to Potato Virus Y
Authors: Lewis R. S.
Published: September 2007

New alleles influencing resistance to potato virus Y (PVY) would be valuable for developing resistant tobacco (Nicotiana tabacum L.) cultivars. The first objective of this research was to evaluate materials possessing an introgressed genomic region (Nafr) from N. africana Merx. & Buttler for their resistance against an array of nine PVY isolates. Seven near‐isogenic genotypes of flue‐cured tobacco cultivar K326 were produced that possessed Nafr and the recessive resistance gene, va, in different combinations and zygosities. Nafr provided little protection against mild non‐necrotic isolates, but imparted significant increased resistance against the necrotic effects of two severe isolates. Data indicated that Nafr and va can be combined to increase the range and level of resistance or tolerance to PVY. A second objective was to evaluate five backcross‐derived K326 Nafr/Nafr isolines and corresponding hemizygous F1 hybrids for yield and quality characteristics in field experiments in the absence of PVY infection. The K326 Nafr/— genotypes were not significantly different from K326 for yield or cash return, and produced cured leaf with improved quality. The Nafr/Nafr genotypes were inferior to Nafr/— genotypes for yield, cash return, and cured leaf quality. Genotypes of the Nafr/— va/va combination may have the greatest practical value when yield, quality, and reaction to PVY infection are collectively taken into consideration.
Marker‐Assisted Selection of Columbia Root‐Knot Nematode Resistance Introgressed from Solanum bulbocastanum
Authors: Zhang L.-H. , Mojtahedi H. , Kuang H. , Baker B. , Brown C. R.
Published: September 2007

The Columbia root‐knot nematode (Meloidogyne chitwoodi Golden et al.) is a serious pest that reduces tuber quality of potato (Solanum tuberosum L.) in the U.S. Northwest and other parts of the world. A gene, RMc1(blb), derived from the Mexican wild species Solanum bulbocastanum Dunal, encodes resistance to this pest. An F1 mapping population with >250 individuals generated from an intraspecific cross between resistant and susceptible clones of S. bulbocastanum, SB22 and PT29, respectively, was used for marker screening and genetic linkage analysis. One amplified fragment length polymorphism marker and five sequence tagged site (STS) markers cosegregated with RMc1(blb) The five STS markers were developed from bacterial artificial chromosome (BAC) end sequences of BAC clones that were derived from another wild species, S. demissum Lindl, and contained homologs of resistance gene N against tobacco mosaic virus. These markers were tested on families that were part of the introgression of RMc1(blb) into advanced breeding lines in BC5 The utility of an efficient alternative to greenhouse and field phenotypic screening was demonstrated. The results of this study confirm that molecular markers closely linked to RMc1(blb) will assist in a selection program, reducing expense and time involved in root‐knot nematode screening.
Determining Seed Performance of Frost‐Damaged Maize Seed Lots
Authors: DeVries Mindy , Goggi A. Susana , Moore Kenneth J.
Published: September 2007

Seed quality of maize (Zea mays L.) can be negatively impacted by a fall frost event. It is important for the seed industry to detect frost damage early and to make marketing decisions before the seed lots are conditioned for sale. This study compared several seed quality tests (standard germination [WG], accelerated aging [AA], saturated cold [SC], and soak tests) for their ability to quantify frost damage. Additionally, these tests were used to predict field emergence under poor and average to good field conditions. Two genotypes (B73 × IRF311 and Mo17 × IRF311) were harvested at three moisture contents (300–350, 400–450, and 500–550 g H2O kg−1 fresh weight). An artificial frost treatment was applied to the seed and damage was determined by testing seed after approximately 0, 1.5, 3, 4.5, and 6 mo of storage. The artificial frost treatment significantly decreased viability and vigor of all the seed lots except Mo17 × IRF311 harvested at 300 to 350 g H2O kg−1 fresh weight. As seeds matured, the damage associated with frost treatment decreased. Laboratory tests did not accurately predict field emergence of frost‐damaged seed under poor field conditions; however, AA at 0 mo, SC at approximately 0, 1.5, and 3 mo, and soak at approximately 0, 1.5, and 3 mo had strong relationships to field emergence under average to good field conditions. These results indicate that frost damage in seed lots is quantifiable using the SC and soak tests during approximately the first 3 mo of storage and both tests accurately predict field emergence.
Recovery of Imidazolinone‐Resistant Hard Red Wheat Lines Following Imazamox Application
Authors: Hanson Bradley D. , Fandrich Lynn , Shaner Dale L. , Westra Philip , Nissen Scott J.
Published: September 2007

Imidazolinone‐resistant hard red wheat (Triticum aestivum L.) cultivars are occasionally injured by imazamox applications because a portion of the acetolactate synthase (ALS) remains susceptible to the herbicide. The growth and enzyme activity of two groups of hard red wheat near‐isolines with spring or winter growth habit were examined following imazamox application. Each group of near‐isolines contained a susceptible cultivar and cultivars with the imidazolinone‐resistant trait on either the B or D genome. The spring wheat group also contained a line carrying both the B and D genome copies of the resistance gene. In whole plant experiments, growth of all single‐gene resistant lines was delayed by both 35 and 105 g ha−1 imazamox while the two‐gene line was delayed at only the highest rate. There was a herbicide rate effect on biomass accumulation but no differences among genome locations in the single‐gene resistant lines or among spring vs. winter growth habit. On an ALS enzyme basis, however, there were differences among B‐ vs. D‐genome resistance and between winter and spring growth habit. Spring wheat cultivars with the B‐genome resistance had greater reductions in ALS activity compared to the D‐genome cultivars, while in winter wheat, B‐ and D‐genome lines responded similarly. Differences among genotypes existed in the recovery of ALS activity in imidazolinone wheat but other factors also likely influence the injury occasionally observed in the field.
Geographic Distribution of Stem Rust Resistance in Wheat Landraces
Authors: Bonman J. Michael , Bockelman Harold E. , Jin Yue , Hijmans Robert J. , Gironella Ann Inez N.
Published: September 2007

Wheat stem rust, caused by Puccinia graminis Pers.:Pers f. sp. tritici Eriks. & Henn., is of renewed concern due to the emergence of a new virulent race in East Africa. Landrace accessions of common wheat (Triticum aestivum L. subsp. aestivum) and durum wheat (T. turgidum L. subsp. durum) from the National Small Grains Collection (NSGC) could be sources of new stem rust resistance genes. In an effort to better target the screening of NSGC landrace accessions against the new race, data from the NSGC were analyzed for the geographic distribution of resistance. We used data from U.S. screening trials for 5700 landrace accessions of common wheat and 2719 of durum wheat. Areas with a high incidence of stem rust resistance were found in Ethiopia, Chile, Turkey, Bosnia and Herzegovina, and adjacent areas of the former Yugoslavia. Resistance to multiple races at the seedling stage was most frequent in accessions from Ethiopia and Turkey. Resistance in durum wheat was more frequent than resistance in common wheat. The distribution of the areas with high incidence of resistant durum landraces was similar to that for common wheat landraces. A logistic regression model predicting resistance in common wheat accessions (n = 3607) from 10 traits identified 192 previously untested accessions with a greater than 50% chance of being resistant. Based on this model and on the identification of geographic centers for resistance, accessions will be prioritized for future screening against new stem rust races.
Cold Sensitivity Gradient in Tuber‐Bearing Solanum Based on Physiological and Transcript Profiles
Authors: Ballou Susan M. , Yun Kil‐Young , Cheng Chen , de los Reyes Benildo G.
Published: September 2007

Tuber‐bearing Solanum species exhibit a wide variation with respect to cold sensitivity. Physiological evaluation based on the leakage of cellular electrolytes showed a continuous gradient of sensitivity among cultivated and wild species, which ranged from chilling sensitivity to freezing tolerance by cold acclimation (CA). Solanum trifidum Correll, a chilling‐sensitive species, defines the baseline of cold tolerance within the genus, while S. commersonii Dunal, a cold‐acclimating species, represents the hardiest end of the spectrum. Solanum species at the extreme ends of the sensitivity gradient exhibited distinct expression signatures for selected CA‐associated genes (CBF1, ZAT12, COR47, and GolS3). Transcription factor (CBF1 and ZAT12) expression was positively correlated with CA but not with the sensitivity gradient among nonacclimating species. Variation across the sensitivity gradient was reflected by the differences in induction profiles of nonregulatory genes (COR47 and GolS3).
Canopy Structure and Neutral Detergent Fiber Differences among Temperate Perennial Grasses
Authors: Brink G. E. , Casler M. D. , Hall M. B.
Published: September 2007

Intake of animals grazing grass pasture is in part influenced by canopy density. Our objective was to determine the vertical distribution of dry matter and neutral detergent fiber (NDF) within temperate perennial grass swards. The study was conducted in 2004 and 2005 on a Plano silt loam (fine‐silty, mixed, superactive, mesic Typic Argiudolls). When leaf height of each grass reached 25 cm in spring, summer, and fall, canopy layers were harvested from 20 to 25, 15 to 20, and 10 to 15 cm. Differences in canopy density were usually not significant when precipitation was below normal. With abundant spring precipitation, quackgrass [Elymus repens (L.) Gould] had greater upper canopy density (1.9 mg dry matter [DM] cm−3) than any of the other grasses studied. Grasses typically grazed at shorter heights such as bluegrass (Poa pratensis L.) and perennial ryegrass (Lolium perenne L.) had greater density in the lower canopy layer (1.0–1.3 g DM kg−1). While soft‐leaf tall fescue (Festuca arundinacea Schreb.), reed canarygrass (Phalaris arundinacea L.), and meadow fescue (Festuca pratensis Huds.) had lower density in the upper canopy than timothy (Phleum pratense L.) and quackgrass in the spring, the reverse was true in the summer. Herbage NDF of grasses generally increased from the upper to lower canopy layer (mean difference of 50 g kg−1); perennial ryegrass and meadow fescue often had the lowest NDF throughout the canopy (range of 392–452 and 418–469 g kg−1, respectively). Pasture intake may benefit from a diverse species composition because animals can graze a mixture having optimum density and NDF throughout the canopy.
Influence of Sequential Trinexapac‐Ethyl Applications on Cytokinin Content in Creeping Bentgrass, Kentucky Bluegrass, and Hybrid Bermudagrass
Authors: Ervin E. H. , Zhang Xunzhong
Published: September 2007

Trinexapac‐ethyl (TE) is a popular plant growth regulator in the turfgrass industry not only for its effectiveness in reducing mowing requirements but for its positive effects on turf density and appearance. We hypothesized that reported side effects of TE such as increases in color, photochemical efficiency (PE) of photosystem II, tillering, and chlorophyll, may be related to changes in leaf cytokinin content. Our objective was to determine if TE influences leaftrans‐zeatin riboside (t‐ZR) content of three common turfgrass species. Sods of Kentucky bluegrass (Poa pratensisL.), creeping bentgrass (Agrostis stoloniferaL.), and hybrid bermudagrass (Cynodon dactylon×C. transvaalensis) were transplanted and grown in flats under a greenhouse mist system. Label‐rate TE treatments were applied every 2 wk for 2 mo. Canopy PE, leaf color, canopy height, and leaft‐ZR contents were measured every 2 wk in 2003, with leaf total nonstructural carbohydrates (TNC) measurements added in 2004. A significant increase int‐ZR content was measured following sequential TE treatment in all three species in both years. Leaf TNC was consistently increased following the second TE application in creeping bentgrass and hybrid bermudagrass. While our data are nonspecific as to how TE increases leaft‐ZR, it appears that a shift in assimilate partitioning to basal organs could be a contributing factor. Whatever the mechanism, increased leaft‐ZR is likely to confer aesthetic, as well as functional, advantages to treated turfgrasses.
Yield Environment Affects Glyphosate‐Resistant Hybrid Response to Glyphosate
Authors: Thelen Kurt D. , Penner Don
Published: September 2007

The yield response of glyphosate‐resistant corn (Zea mays L.) to glyphosate across a broad range of temporal yield environments is not well understood. Field experiments were conducted at three Michigan locations over a five year period (2002–2006) comparing corn grain yield of glyphosate‐resistant hybrids as affected by a glyphosate‐based or conventional herbicide system. Regression analyses of yield data showed a dual glyphosate‐resistant hybrid yield response to glyphosate based on the temporal yield environment for a given year. Under average‐ to low‐yield environments, the glyphosate‐based herbicide system resulted in greater grain yield. However, under temporal high yield environments, the conventional herbicide system resulted in greater grain yield. Threshold corn grain yields above which the conventional herbicide system resulted in higher grain yield and below which the glyphosate‐based herbicide system resulted in higher grain yield were determined to be: 11.38 (± 0.13), 12.73 (± 0.14), 13.97 (± 0.25), and 11.62 (± 0.10) Mg ha−1 respectively for the Huron, Montcalm, Saginaw, and combined site average. Differences in weed control levels were not observed and weed control did not appear to be a factor in grain yield determination. The results suggest a slight corn grain yield reduction from glyphosate under certain temporal high‐yield environments.
Diurnal Shifts in Nutritive Value of Alfalfa Harvested as Hay and Evaluated by Animal Intake and Digestion
Authors: Burns J. C. , Fisher D. S. , Mayland H. F.
Published: September 2007

Forages accumulate nonstructural carbohydrates during the day, with animals showing preference and improved daily responses from afternoon compared with morning cut hays. This study evaluated alfalfa (Medicago sativa L.) hay harvested at 0700, 1000, 1300, 1600, and 1900 h to determine how nutritive value changes during the day and to assess the impact of these changes on animal preference using cattle (Bos taurus L.), sheep (Ovis aries L.), and goat (Capra hircus L.) responses. Total nonstructural carbohydrates were altered by time of cut (cubic contrast, P < 0.01) ranging from 85 g kg−1 at 0700 h to 83 g kg−1 at 1000 h, then increasing to 97 g kg−1 by 1600 h with little change at 1900 h (96 g kg−1). Fiber fractions also varied diurnally, with a quadratic decrease from 418 g kg−1 at 0700 h to 387 g kg−1 by 1900 h in neutral detergent fiber. A combined analysis of three animal trials showed a linear increase in dry matter intake (DMI) with later hay harvest, a cubic response for dry matter digestion (DMD), and a linear increase in digestible DMI. Mean DMI increased from 27.5 g kg−1 body weight at 0700 h to a maximum of 30.8 g kg−1 body weight at 1600 h, whereas DMD decreased from 658 g kg−1 at 0700 to 647 g kg−1 at 1300 h and peaked at 664 g kg−1 at 1600 h. Digestible DMI increased from 18.1 g kg−1 body weight at 0700 h to a maximum of 20.5 g kg−1 body weight at 1600 h. No additional advantages in animal responses were noted by cutting after 1600 h.
Microsatellite Markers Linked to Stem Rust Resistance Allele Sr9a in Wheat
Authors: Tsilo Toi J. , Jin Yue , Anderson James A.
Published: September 2007

Host resistance to stem rust of wheat (Triticum aestivum L.), caused by Puccinia graminis Pers.:Pers. f. sp. tritici Eriks. & E. Henn., is more effective and durable when several stem rust resistance (Sr) genes are pyramided into a single line. We studied the Sr9a allele, one of six known alleles at the Sr9 locus on chromosome 2BL, using 116 F2 plants and their F2:3 families derived from the cross of near‐isogenic lines (NILs) ‘Chinese Spring’ and ISr9a‐Ra. Four microsatellite markers were identified that mapped within 3.6 cM proximal to the Sr9a locus. Fifty‐nine wheat accessions were screened with the three codominant and one dominant markers to determine their polymorphism information content (PIC). The marker Xgwm47 revealed 12 alleles and had the highest PIC value of 0.85. We attempted to postulate the presence of Sr9a by phenotypic screening. In accessions that had multiple Sr genes, however, it was not possible to postulate Sr9a due to masking effects. Despite the ambiguity of phenotypic evaluation, Xgwm47 was diagnostic for Sr9a in additional NILs tested. These results suggest that Xgwm47 will be a useful tool for marker‐assisted selection of Sr9a in wheat breeding programs.
Development of Investment‐Casting Process of Mg‐Alloys for Aerospace Applications
Authors: Arruebarrena G. , Hurtado I. , Väinölä J. , Cingi C. , Dévényi S. , Townsend J. , Mahmood S. , Wendt A. , Weiss K. , Ben‐Dov A.
Published: September 2007

Investment casting offers high‐quality castings with good dimensional accuracy, being therefore suitable for aircraft applications. Since commercial ceramic shells react with Mg melts and appropriate inhibitors being not available, magnesium alloys are not widely used in industrial investment‐casting. In order to overcome this situation and enable the aircraft industry to take advantage of the light‐weight properties of magnesium, the process is analyzed within the European FP6 IDEA project, which aims at developing new high‐strength magnesium casting alloys for aeronautic applications.
Microstructural and Mechanical Behavior of Friction Welds in a High Creep Resistance Magnesium Alloy
Authors: Pinheiro G. A. , Olea C. A. W. , dos Santos J. F. , Kainer K. U.
Published: September 2007

Friction weldability of Mg based alloys has been worldwide discussed. Within this context the aim of this study was to investigate rotational friction welding of an Aluminum‐Rare Earth based high creep resistance Mg alloy AE42HP from the viewpoint of thermo cycle‐microstructure‐performance relationships to evaluate the potential use of FW in joining modern Mg‐alloys.
Mg Based Bulk Metallic Glasses with high Mechanical Strength and Large Viscoplastic Forming Capacity
Authors: Puech S. , Blandin J. J. , Soubeyroux J. L.
Published: September 2007

Various Mg based BMG were successfully elaborated by copper mould casting. High strengths (> 600 MPa) were obtained in compression at room temperature associated with a large elastic strain (≈ 0.015) but also to a macroscopically brittle behavior. Deformation capacity in the glass transition interval has been investigated. For such temperatures, thanks to Newtonian rheologies, glasses exhibit a particularly good viscoplastic forming ability with low viscosities. However, in some cases, crystallization can occur during the process and increase sharply the viscosity.
Thermally Responsive Biomineralization on Biodegradable Substrates
Authors: Shi J. , Alves N. M. , Mano J. F.
Published: September 2007

Biomineralization offers an elegant example of how nature can design complex, hierarchical, and structurally/morphologically controllable materials. In this work, the surface of bioactive substrates prepared from poly(L‐lactic acid) and reinforced with Bioglass are modified by the graft polymerization of poly(N‐isopropylacrylamide), (PNIPAAm) after plasma activation. It is found that such treatment, together with temperature, could trigger the formation of apatite on the biodegradable substrate upon immersion in simulated body fluid above the PNIPAAm lower critical solution temperature (LCST); in contrast, no apatite is formed at room temperature. A control experiment on a material that is not subjected to surface treatment does not show any evidence of mineral deposition at the two analyzed temperatures. This “smart” biomineralization concept is combined with patterning methodologies to control the microstructure of the surface onto which PNIPAAm is grafted. In this case, the apatite is formed at 37 °C in the modified regions. We suggest that this concept could be extended in the biomimetic production of other minerals, where it would be triggered by another kind of stimulus (e.g., pH or ionic strength) in substrates with more complex geometries.
Characterization of Geoinspired and Synthetic Chrysotile Nanotubes by Atomic Force Microscopy and Transmission Electron Microscopy
Authors: Piperno S. , Kaplan‐Ashiri I. , Cohen S. R. , Popovitz‐Biro R. , Wagner H. D. , Tenne R. , Foresti E. , Lesci I. G. , Roveri N.
Published: September 2007

Geoinspired synthetic chrysotile nanotubes both stoichiometric and 0.67 wt % Fe doped were characterized by transmission electron microscopy and electron diffraction. Bending tests of the synthetic chrysotile nanotubes were performed using the atomic force microscope. The nanotubes were found to exhibit elastic behaviour at small deformations (below ca. 20 nm). Young's modulus values of (159 ± 125) GPa and (279 ± 260) GPa were obtained from the force‐deflection curves using the bending equation for a clamped beam under a concentrated load, for the stoichiometric and the Fe doped chrysotile nanotubes, respectively. The structural modifications induced by Fe doping altered the mechanical properties, with an apparent dependence of the latter on the number of constituting walls of the nanotubes.
Highly Efficient Non‐Doped Blue‐Light‐Emitting Diodes Based on an Anthrancene Derivative End‐Capped with Tetraphenylethylene Groups
Authors: Shih P.‐I , Chuang C.‐Y. , Chien C.‐H. , Diau E. W.‐G. , Shu C.‐F.
Published: September 2007

A novel blue‐emitting material, 2‐tert‐butyl‐9,10‐bis[4‐(1,2,2‐triphenylvinyl)phenyl]anthracene (TPVAn), which contains an anthracene core and two tetraphenylethylene end‐capped groups, has been synthesized and characterized. Owing to the presence of its sterically congested terminal groups, TPVAn possesses a high glass transition temperature (155 °C) and is morphologically stable. Organic light‐emitting diodes (OLEDs) utilizing TPVAn as the emitter exhibit bright saturated‐blue emissions (Commission Internationale de L'Eclairage (CIE) chromaticity coordinates of x = 0.14 and y = 0.12) with efficiencies as high as 5.3 % (5.3 cd A–1)—the best performance of non‐doped deep blue‐emitting OLEDs reported to date. In addition, TPVAn doped with an orange fluorophore served as an authentic host for the construction of a white‐light‐emitting device that displayed promising electroluminescent characteristics: the maximum external quantum efficiency reached 4.9 % (13.1 cd A–1) with CIE coordinates located at (0.33, 0.39).
High Performance Polymer Electrophosphorescent Devices with tert‐Butyl Group Modified Iridium Complexes as Emitters
Authors: Wei X. , Peng J. , Cheng J. , Xie M. , Lu Z. , Li C. , Cao Y.
Published: September 2007

The synthesis and photophysical study of two novel tert‐butyl modified cyclometalated iridium(III) complexes, i.e., bis(4‐tert‐butyl‐2‐phenylbenzothiozolato‐N,C2′) iridium(III)(acetylacetonate) [(tbt)2Ir(acac)] and bis(4‐tert‐butyl‐1‐phenyl‐1H‐benzimidazolato‐N,C2′) iridium(III)(acetylacetonate) [(tpbi)2Ir(acac)], are reported, their molecular structures were characterized by 13C NMR, 1H NMR, ESI‐MS, FT‐IR, and elementary analysis. Compared with their prototypes without tert‐butyl substituents [(bt)2Ir(acac) and (pbi)2Ir(acac)], (tbt)2Ir(acac) and (tpbi)2Ir(acac) both have shortened phosphorescent lifetimes[(tbt)2Ir(acac) versus (bt)2Ir(acac), 1.1 μs:1.8 μs; (pbi)2Ir(acac) versus (tpbi)2Ir(acac), 0.8 μs:1.82 μs]. Moreover, (tbt)2Ir(acac) has much more improved phototoluminescence quantum efficiencies in CH2Cl2 solution, [(tbt)2Ir(acac), 0.51; (bt)2Ir(acac), 0.26]. Employing them as dopants, high performance double‐layer PLEDs were fabricated. The (tbt)2Ir(acac)‐based and (tpbi)2Ir(acac)‐based PLEDs have the maximum external quantum efficiencies of 8.71 % and 10.25 %, respectively, and high EL quantum efficiencies of 5.92 % and 7.21 % can be achieved under high driven current density of 100 mA cm–2. PLEDs fabricated with both the two phosphors have much broadened EL spectra with FWHM of > 110 nm, which afford the feasibility to be used as dopants in white LEDs, and the best doping concentrations of the two complexes in fabrication of PLEDs were optimized.
Shape‐Selective Synthesis of Gold Nanoparticles with Controlled Sizes, Shapes, and Plasmon Resonances
Authors: Zhang J. , Liu H. , Wang Z. , Ming N.
Published: September 2007

The attachment of water molecules to poly(vinylpyrrolidone) (PVP) is used in conjunction with the region‐selective distribution of PVP and water in a water/PVP/n‐pentanol system to confine reactions along the surface of PVP, thus achieving the highly shape‐selective synthesis of anisotropic Au nanostructures with controlled sizes and remarkable shapes such as regular octahedrons, triangles, rods, dumbbells, belts, and hexagons. The IR absorption spectra of the Au nanoparticles confirm that the nanoparticles are formed around PVP, and corroborate the adsorption of PVP on Au. The size, shape, and plasmon resonance of the Au nanoparticles can be readily tuned by modifying the adsorption behavior and/or the reducing ability of PVP by adjusting the relative amounts of PVP and water, directly adding gold seeds, or changing the stirring conditions in the reaction mixture. The obtained highly pure anisotropic Au nanostructures and the synthesis method demonstrated here enable us to study distinct nanostructures to search for novel physicochemical properties and technological applications. Our method is also successfully extended to prepare highly pure silica spheres, tubes, and needles with controlled aspect ratios.
Corporate leadership award: How Conocophillips manages disputes
Authors: Bleemer Russ
Published: September 2007

Behind the CPR 2007 Corporate Leadership Award, a top ConocoPhillips Inc. attorney discusses the oil giant's ADR‐first strategy.