118,414 research outputs found
Chlorotic mottle of bean (Phaseolus vulgaris L.)
No full textFor the past years there have been outbreaks of a disease of bean ( Phaseolus vulgaris L.) in Colombia called bean chlorotic mottle. The etiology of bean chlorotic mottle was not known, but the disease was generally believed to be incited by the same whitefly-transmitted virus that causes variegation in malvaceous plants. The aim of this study was to identify and further characterize the causal agent of bean chlorotic mottle.As from the literature it was not clear which symptoms were characteristic of the disease, firstly a symptom had to be established common to all allegedly bean chlorotic mottle-affected bean plants. This symptom, a sharp mosaic in which the discoloured areas ranged from pale greenish-yellow to bright yellow, was of diagnostic value to detect infected plants in the field. In addition to this sharp mosaic, chlorotic mottle-affected bean plants in the field often showed a host of other symptoms, such as mild mottle, rugosity, leaf curling, malformation, dwarfing, proliferation and witches' broom-like growth. In the same affected population some bean plants showed only the sharp mosaic, whereas others showed additional witches' broom-like growth.Mechanical inoculation experiments conducted with crude sap and partially purified preparations from bean plants exhibiting chlorotic mottle in the field, showed three viruses to be present, viz. bean mild mosaic virus, cucumber mosaic virus and southern bean mosaic virus. By means of differential hosts these three viruses could be separated. Isolates of these viruses were designated BMMV-CIAT, CMV-CIAT and SBMV-CIAT, respectively. Experiments conducted with whiteflies did not reveal the presence of any whitefly-transmitted virus in chlorotic mottle-affected bean plants.BMMV-CIAT, is an isometric particle, 32 nm in diameter, with a single-stranded RNA molecule. The virus is readily transmitted mechanically and its host range is restricted to legumes, viz. Glycine max , Macroptilium spp., Phaseolus spp. and Rhynchosia minima . In P. vulgaris the virus usually causes a mild mosaic which is hardly visible, and in certain cultivars with age, the virus becomes latent. Though affected bean plants grew normally producing healthy- looking pods, flowering and pod formation were usually delayed by about a week under glasshouse conditions. The chrysomelid beetles Diabrotica balteata and Cerotoma facialis were efficient vectors of BMMV-CIAT. The virus is seed-transmitted in beans, percentages ranging from 1.2 to 3.6 in the different cultivars tested. In contrast to many other beetle-transmitted viruses, BMMV-CIAT sediments in sucrose gradients as one particle. The physical and chemical properties of BMMV-CIAT are similar or equal to those of BMMV described by Waterworth et al. (1977). The darkly stained granular material in root cells occasionally observed in the light microscope, proved to be aggregates of virus particles.Cross protection and serological tests showed that CMV-CIAT is related to the CMV-type strain. However, many differences exist between them, the most striking being the ability of CMV-CIAT to cause systemic mosaic in P. vulgaris . The host reactions of CMV- CIAT resembled those of CMV-B 32, an isolate from bean in Spain (Bos and Maat, 1974), but the former had a longer longevity in vitro . Generally, CMV-CIAT induced a yellow mosaic in P. vulgaris , but the symptoms varied greatly in different cultivars. In the cultivars Honduras 46 and Porrillo 1 a sharp mosaic, similar to chlorotic mottle, was produced one month after inoculation with CMV-CIAT None of the bean cultivars and CIAT advanced breeding lines tested were found to be resistant or hypersensitive to CMV-CIAT The virus is transmitted by Aphis gossypii and through seeds of P. vulgaris , Vigna radiata and V. unguiculata 'California Blackeye'. It has poor antigenic properties and is serologically related to CMV-B 32, to a CMV isolate from Yucca (Bouwen et al., 1978) and to the Y-strain of CMV (Scott, 1968). Large inclusions in plant tissues infected with CMV-CIAT could easily be detected in the light microscope.The third virus, SBMV-CIAT, is readily transmitted mechanically. Though the host plant range included mostly legumes, the virus also infected Cucumis sativus 'Ashley'. The virus was more harmful to P. acutifolius , in which it caused severe top necrosis, than to P. vulgaris . Among the cultivars and CIAT advanced breeding lines of P. vulgaris , hypersensitive hosts were found. The virus induced a bright yellow mosaic in G. max . Besides P. vulgaris 'Pinto U.I. 650' other suitable assay hosts for SBMV-CIAT were found viz. Mucuna pruriens and M. utilis which reacted with pin-point necrotic local lesions to the virus. SBMV-CIAT is seed transmitted, the percentages ranging from 3.6 to 33.6 depending on the bean cultivar. Thephysical and chemical properties of SBMV-CIAT are similar or equal to the SBMV bean strain, except for the guanine content of the nucleic acid.An experiment conducted to find out the effect of the above- mentioned viruses alone or in combination with each other on bean plants, indicated that symptoms resembling chlorotic mottle could be reproduced in bean plants by mechanical inoculation with CMV-CIAT alone or in combination with the other two viruses. The vast range of other symptoms sometimes exhibited by bean plants with chlorotic mottle in the field, could also be reproduced by mechanically inoculating the viruses in different combinations at different times after planting of seeds. Witches' broom-like symptoms were produced in bean plants inoculated on their primary leaves with a mixture containing SBMV-CIAT with BMMV-CIAT or with CMV-CIATFrom the present study it is clear that bean chlorotic mottle, as described in literature, is a composite disease caused by a combination of BMMV-CIAT, CMV-CIAT and SBMV-CIAT in which CMV-CIAT is responsible for the sharp mosaic and the other two viruses together are responsible for the additional symptoms like rugosity, leaf curling, witches' broom-like growth etc. Efficient vectors of these viruses are present in the bean fields. Though data are not available for the population distribution of aphids, chrysomelid beetles are present throughout the year in the CIAT fields. Seed transmission of the virus is of considerable epidemiological significance. Infected seeds are vehicles for long distance transport and survival from one season to another, especially in case of BMMV-CIAT, and BMMV-CIAT which have a narrow host range. The diseases caused by the three viruses might be controlled by reducing the number of infection sources and by limiting the spread of the viruses
Recent advances in the synthesis of naturally occurring tetronic acids
No full textDuring the last decades the interest towards natural products containing the tetronic acid moiety augmented significantly, due to their challenging structures and to the wide range of biological activities they display. This increasing enthusiasm has led to noteworthy advances in the development of innovative methodologies for the construction of the butenolide nucleus. This review provides an overview of the progress in the synthesis of tetronic acid as a structural key motif of natural compounds, covering the last 15 years. Herein, the most representative synthetic pathways towards structurally diverse natural tetronic acids are grouped according to the strategy followed. The first part describes the functionalization of a preformed tetronic acid core by intermolecular reactions (cross-coupling reactions, nucleophilic substitution, multicomponent reactions) whereas the second part deals with intramolecular approaches (Dieckmann, cycloaddition or ring expansion reactions) to construct the heterocyclic core. This rational subcategorization allowed us to make some considerations about the best approaches for the synthesis of specific substrates, including modern intriguing methodologies such as microwave irradiation, solid phase anchoring, bio-transformations and continuous flow processes
A new 3,4-seco-lupane derivative from Lasianthus gardneri
No full textA new seco-ring A lupane triterpene derivative (1), along with lupenone, lupeol, beta-sitosterol, ursolic acid, and stigmasterol 3-O-beta-d-glucoside, were isolated from a methanol extract of mature stems of Lasianthus gardneri, a shrub from the family Rubiaceae growing in Sri Lanka. The structure and stereochemistry of the new compound were determined using a combination of (13)C and (1)H homo- and heteronuclear 2D NMR experiments and from mass spectral data. The structure of 1 was confirmed by partial synthesis from lupeol
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
Square Dancing with the Stars to Enhance Dynamic Hirschman Linkages?
No full textIn this Presidential Address, the author takes the reader on a reconnaissance of his life and time as a regional scientist. He points out scenery he found scintillating along the way, hoping that some may pick up the banner and chew on a few of the ideas for a while. He suggests a revisit to Albert O. Hirschman’s notion of key sectors and more empirical analysis related to Marcus Berliant’s and Masahisa Fujita’s notion of knowledge creation and transfer.Presidential Address, San Antonio, Texas, March 29, 2014 (53rd Meetings of the Southern Regional Science Association
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe 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
Synthesis and Antifungal Activity of a Series of N-Substituted [2-(2,4-Dichlorophenyl)-3-(1,2,4-triazol-1-yl)]propylamines
No full textA series of N-mono- or N,N-disubstituted [2-(2,4-dichlorophenyl-3-(1,2,4-triazol-1-yl)]propylamines and N-[2-(2,4-dichlorophenyl-3-(1,2,4-triazol-1 -yl)propyl]amides were synthesized and tested for their fungicidal activity in vitro and in vivo against a group of plant pathogenic fungi. Some compounds exhibited a fairly good in vitro activity. The replacement of the ether group of tetraconazole with a secondary or tertiary amino group leads to compounds that maintain the antifungal activity on several phytopathogenic fungi, provided that the substituents are not too bulky or lipophilic. The allyl, propargyl, and cyclopropyl groups appear particularly suitable. Although these compounds have some structural similarities with terbinafine and naftifine, which act as squalene epoxidase inhibitors, they maintain the usual mechanism of action of the other triazoles
Letter from unknown writer to Jesse L. Boyce
No full textLetter to Jesse L. Boyce from unknown author (possibly Jack) about the investigation into the powder magazine located in the Grand Canyon. Some personal news is included in the letter such as the writer's marriage to the daughter of C.A. Taylor, former Supervisor of Cochise County
Dispelling the Myths Behind First-author Citation Counts
No full textWe 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
Sarah L. Blum Author Visit - Warrior Nurse: PTSD and Healing
No full textHear Sarah L. Blum, author of Women Under Fire: Abuse in the Military, discuss her newest book, Warrior Nurse: PTSD and Healing followed by a Q&A and book signing.
Sarah L. Blum is a decorated Vietnam veteran who served as an operating room nurse during the intense fighting of 1967. In recognition of her service, she was awarded the Army Commendation Medal.
Sponsored by CWU Veterans Center and CWU Libraries.https://digitalcommons.cwu.edu/libraryevents/1252/thumbnail.jp
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