1,720,955 research outputs found
Characterization of the bacterial stem blight pathogen of alfalfa, Pseudomonas syringae pv. syringae ALF3
Full text linkPoster presentation at the 2014 meeting of the American Phytopathological Society,Bacterial stem blight of alfalfa occurs sporadically in the central and western U.S. Yield losses of up to 50% of the first harvest can occur with some cultivars. Developing resistant cultivars is hampered by lack of information on the pathogen and a standard test for evaluating plant germplasm. Bacteria producing a fluorescent pigment were isolated on King’s B agar from alfalfa with symptoms of bacterial stem blight from near Cheyenne, WY. The strain ALF3 was tentatively identified as Pseudomonas syringae pv. syringae based on 16S rDNA sequence and PCR amplification of syrB for lipodepsinonapeptide toxin production. Multilocus sequence analysis indicated that ALF3 falls within a clade containing strains of P. syringae pv. syringae with closest affinity to FF5 from pear. Comparison of a draft whole-genome sequence of ALF3 further confirmed that ALF3 most closely resembles FF5 (~96% sequence identity) and P. syringae pv. aptata DSM50252 from beet. Approximately 60 genes were unique to ALF3, including several predicted genes in the T3SS cluster such as a type III helper protein HrpZ (Pto) and phage-associated genes. ALF3 was highly pathogenic to snapbean pods but caused only mild symptoms on leaves of snapbean, pear, and sugarbeet. A standardized method for evaluating disease resistance in alfalfa was developed. Cultivars with fall dormancy ratings of 1 and 2 had higher percentages of resistant plants than cultivars with fall dormancy ratings of 8-11.Samac, Deborah A; Studholme, David J; Ao, Samadangla. (2014). Characterization of the bacterial stem blight pathogen of alfalfa, Pseudomonas syringae pv. syringae ALF3. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/194194
Morpho-Physiological Traits Associated with Drought Tolerance of Maize Hybrids Subjected to Different Water and Nitrogen Supply
No full textUniversity of Minnesota Ph.D. dissertation. November 2016. Major: Applied Plant Sciences. Advisor: Jeffrey Coulter. 1 computer file (PDF); xvi, 142 pages.Maize (Zea mays L.) hybrids reported as having tolerance to drought are expected to perform better than non-drought-tolerant (‘standard’) hybrids under drought stress, but few studies confirm this with a mechanistic justification. In addition, morpho-physiological traits that may confer drought tolerance have not been compared extensively between drought-tolerant and standard maize hybrids. This study was conducted to assess whether drought-tolerant and standard varieties differ in agronomic and morpho-physiological traits associated with drought tolerance. Three experiments were conducted on loamy sand field soil in central Minnesota, in which a drought-tolerant and a standard hybrid were compared under three levels of sustained moderate drought stress established using drip irrigation: no drought stress; drought stress from the 14 leaf collar maize phenological stage (V14) to maize physiological maturity (R6); and drought stress from the blister maize phenological stage (R2) to R6. The three fertilizer N rate treatments: sub-optimal (50%), 50% of the expected economically optimum N rate; optimal (100%), 100% of the economically optimum N rate; and supra-optimal (150%), 50% greater than the economically optimum N rate were applied to each combination of hybrid and drought stress. Grain yield was 10% greater for the drought-tolerant compared to the standard hybrid with drought stress from V14 to R6, but did not differ between hybrids when drought stress occurred from R2 to R6 or in the absence of drought stress. Grain and silage yields with the supra-optimal N rate were 7 and 12% greater for the drought-tolerant than standard hybrid, respectively. With drought stress from R2 to R6 and V14 to R6, kernels per square meter were 6 and 23% greater and kernel mass was 3 and 10% less with the drought-tolerant than standard hybrid, respectively. Aboveground N uptake was 9% greater with the drought-tolerant than standard hybrid at the supra-optimal N rate. Actual crop evapotranspiration (ETa) decreased with increasing duration of drought stress. Crop water use efficiency (CWUE) was 21% greater in the absence of drought stress compared to when drought stress occurred from V14 to R6 or R2 to R6. The drought-tolerant hybrid had 7 and 8% greater CWUE and irrigation water use efficiency (IWUE), respectively, than the standard hybrid with drought stress from V14 to R6. Irrigation water use efficiency for the standard and drought-tolerant hybrids was greater by 20 and 29%, respectively, with the supra-optimal than sub-optimal N rates. The basal crop coefficient (Kcb) during the mid-season was 1.08, 0.89, and 0.73, respectively, for no drought stress, drought stress from R2 to R6, and drought stress from V14 to R6 across hybrids in experiment where maize followed soybean with optimal N rate; and during the late season growth stage was 0.82, 0.61, and 0.61, respectively. Two phases of Kcb, an initial adaption phase with fluctuating Kcb followed by a response phase with stable Kcb, occurred when maize was exposed to drought stress. Compared to the standard hybrid, the drought-tolerant hybrid had a narrower anthesis-silking interval (ASI), greater leaf area index (LAI) for all N rates across experiments and drought stress at milk maize phenological stage, and lower leaf chlorophyll content in all levels of drought stress across experiments and N rates at silking and milk maize phenological stages. Drought stress and sub-optimal N rate increased ASI, and reduced LAI, leaf greenness, and leaf chlorophyll content. With drought stress from R2 to R6, photosynthesis (A) did not differ between hybrids but transpiration (E) and stomatal conductance (gs) were greater for the drought-tolerant hybrid suggests greater stomatal aperture. In the absence of drought stress, the standard hybrid had greater A, E, and gs in the experiment when maize followed winter rye. The drought-tolerant hybrid had more root length density (RLD) that was 0.4 to 1.5 mm in diameter in the 0- to 15-cm soil depth. Fine roots with a diameter 0 to 0.4 mm were more abundant in the entire sampled depth of 0 to 90 cm. Distribution of RLD was associated with water availability in the soil profile. Overall, the greater grain yield of the drought-tolerant maize hybrid when drought stress occurred from V14 to R6 was associated with greater aboveground biomass, N uptake, and kernel number, which were strongly correlated to IWUE. Results demonstrated expression of multiple morpho-physiological traits under drought stress; in particular, greater LAI, chlorophyll content, and stomatal conductance suggest that drought tolerant hybrids can conduct photosynthesis under drought stress conditions compared to standard hybrids. Further research is needed to enhance the knowledge of N management for drought-tolerant hybrids and the relationship of traits associated with drought tolerance, especially mechanisms related to photosynthetic carbon assimilation and crop water use.Ao, Samadangla. (2016). Morpho-Physiological Traits Associated with Drought Tolerance of Maize Hybrids Subjected to Different Water and Nitrogen Supply. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/185203
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Lignin reduction in alfalfa (Medicago sativa) does not affect foliar disease resistance
No full textPoster presentation at the annual meeting of the American Phytopathological Society in August 2018.Disruptions in the lignin biosynthetic pathway have been shown to reduce disease resistance in
a number of crops. Recently, genetically modified alfalfa (Medicago sativa) varieties have been
marketed with reduced lignin and improved forage quality traits, including increased
digestibility by ruminants at later stages of plant maturity. The objective of this study was
to compare foliar disease resistance in three reference alfalfa varieties, 54R02, DKA43-22RR,
WL355.RR, and the reduced lignin variety, 54HVX41, to evaluate the effect of the reduced lignin
trait on foliar disease resistance. Alfalfa plants in research plots at three locations in
Minnesota were evaluated for percent defoliation caused by foliar pathogens at four maturity
stages; early bud, bud, early flower, and flowering; with natural inoculum. Spring black stem
and leaf spot, Leptosphaerulina leaf spot, and common leaf spot were observed from June through
September in all locations on all varieties. Summer black stem and leaf spot was most prevalent
in August on all varieties at one location. The amount of defoliation increased with maturity
stage for all varieties. When harvest was delayed until the flowering stage, moderate to severe
(32 to 64%) leaf loss occurred, depending on location. Alfalfa varieties did not differ in
percent defoliation at any maturity stage indicating that the reduced lignin trait did not
affect foliar disease resistance.Samac, Deborah A; Ao, Samadangla; Dornbusch, Melinda R; Grev, Amanda M; Wells, M Scott; Martinson, Krishona; Sheaffer, Craig C. (2018). Lignin reduction in alfalfa (Medicago sativa) does not affect foliar disease resistance. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/202991
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