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Bioherbicide use of plant defensive compounds in meadowfoam seed meal
Get PDFMeadowfoam (Limnanthes alba Hartw. ex Benth) seed meal (MSM), a by-product of meadowfoam oil extraction, has a plant defensive compound known as glucosinolate glucolimnanthin (GLN). Myrosinase enzymes present in soil microbes and meadowfoam seeds can convert GLN to glucosinolate breakdown products (GBPs), which demonstrate herbicidal activity and have the potential to be used as bioherbicides. The goals of this research were to evaluate the effectiveness of MSM on weed control and to explore the optimal timing, rate, and application method for further use of MSM as a bioherbicide. Adding active myrosinase from freshly ground meadowfoam seeds to MSM increased its phytotoxicity. In a greenhouse study, no lettuce emergence was observed for six days in soil amended with 3% by weight activated MSM. In a field application, MSM provided a nitrogen source and promoted lettuce growth when lettuce seedlings were transplanted seven days after MSM incorporation. Co-occurrence of herbicide and fertilizer effects was observed with all MSM concentrations. MSM concentrations of 5% and 7% provided greater weed emergence suppression than the 3% concentration but no difference in weed biomass was observed between MSM concentrations. A split MSM application resulted in a significant benefit for weed control, similar to a single MSM application; however for the split application, the concentration and time should be adjusted to prevent residual crop injury. Activated MSM inhibited spiny sowthistle (Sonchus asper (L.) Hill) greater than 95% for emergence and 80% for biomass compared to the untreated control. Soil microbes reallocated carbon input from MSM application to biomass and enzyme production. The reallocation occurred quickly, within 7 to 14 days, after MSM application. Microbial biomass increased by at least 85% for carbon and 95% for nitrogen with MSM application compared to the untreated control. β-N-acetylglucosaminidase activity was highly correlated with microbial biomass nitrogen and was involved in the acquisition of nitrogen from organic sources. Isothiocyanate showed potent herbicidal activity and was detected only in activated MSM. 3-Methoxyphenylacetic acid (MPAA), a previously unidentified GBP with herbicidal activity, was discovered in soil amended with non-activated and activated MSM. A single MSM application at 2.86 kg m⁻² as a pre-emergent soil amendment benefited crop yield, weed suppression, and soil carbon and nitrogen inputs
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Molecular basis of target-site resistance to acetolactate synthase-inhibiting herbicides in mayweed chamomile (Anthemis cotula L.)
Get PDFMayweed chamomile (Anthemis cotula L.) is an annual weed in the Asteraceae family that is commonly found in fields of the Pacific Northwest. Acetolactate synthase (ALS)-inhibiting herbicides are frequently used to control a broad spectrum of weed species including mayweed chamomile. Seeds of four biotypes of mayweed chamomile (KJ, KL1, KL2, and GW) suspected to be resistant to ALS-inhibiting herbicides were collected from different fields in Washington State, USA. Seeds from a susceptible (S) biotype of mayweed chamomile collected in Oregon were used as the control in all the experiments. Greenhouse studies were conducted to determine if the biotypes were resistant to four chemistry classes of ALS-inhibiting herbicides which were sulfonylureas (SU), imidazolinones (IMI), pyrimidinylthio-benzoate (PTB), and sulfonylamino-carbonyltriazolinone (SCT). A whole-plant dose-response assay confirmed cross-resistance to thifensulfuron+tribenuron (SU) and imazethapyr (IMI) in resistant biotypes. There were high levels of resistance to thifensulfuron+tribenuron and moderate to low levels of resistance to imazethapyr. Propoxycarbazone (SCT) and cloransulam (TP) were applied at the recommended field rate. All resistant biotypes had moderate levels of resistance to propoxycarbazone while biotypes GW and KJ had moderate and low levels of resistance to and cloransulam, respectively. The resistance also was confirmed using an in vitro ALS assay. The herbicide concentrations that inhibited ALS activity by 50% (I50) in the resistant biotypes were between 26- and 289-fold greater than in the S biotype for thifensulfuron+ tribenuron; 2- to 5-fold greater for imazethapyr; 3- to 18-fold greater for propoxycarbazone; and 4- to 18-fold greater for cloransulam. Once resistance was confirmed, the ALS gene was sequenced to determine if mutations occurred in the target-site. At least two ALS isoforms of ALS gene (ALS1 and ALS2) were found in the mayweed chamomile biotypes. No mutations were observed in ALS2. The target-site mutations conferring the resistance to ALS-inhibiting herbicides were likely in ALS1. Sequence analysis of the ALS1 gene identified four point mutations (Pro197 to Leu, Gln, Thr or Ser) at position 197 in the resistant biotypes. Homozygous and heterozygous resistance and the existence of two different mutant ALS alleles were found in resistant biotypes. The ALS-resistant alleles and genotypes in resistant biotypes were diverse and related to the cross-resistance to ALS-inhibiting herbicides
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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
Seed morphology and allelopathy of invasive Praxelis clematidea
Get PDFPraxelis [Praxelis clematidea (Griseb.) R.M.King & H.Rob.] is an invasive species that infests many agricultural systems globally, such as orchards, rubber plantations, and other economic crops. The purpose of this research was to study seed morphology, germination factors, and allelopathy of aboveground parts of P. clematidea. P. clematidea seeds are small, light, and possess pappi that allow them to be dispersed easily by wind or animals. Among four P. clematidea populations collected from different provinces in Thailand, the size of P. clematidea seeds ranged from 2.6 to 3.2 mm in length, 0.6 to 0.7 mm in width, and were 0.4 mm in thickness. The weight of P. clematidea seeds ranged from 0.13 to 0.21 mg. P. clematidea had about 44 to 48 seeds per head. Seeds germinated over a temperature range of 20 to 30 °C while high (45 °C) and low (10 °C) temperatures reduced germination. Maximum germination occurred when seeds were planted on the soil surface. No seedlings germinated when seeds were planted at a depth more than 1 cm. P. clematidea extracts from aerial plant parts at concentrations of 25 and 50% inhibited seedling growth of hairy beggarticks (Bidens pilosa L.). Basic knowledge of the seed biology of P. clematidea and allelochemicals can help in understanding the invasiveness and in developing management strategies for this weed
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
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