104 research outputs found
ANTIFUNGAL ACTIVITY OF AQUEOUS AND ETHANOL EXTRACTS OF TROPICAL PLANTS AGAINST TOMATO FUNGAL PATHOGENES.
No full textSeveral plant extracts may have a strong antifungal activity
that can be exploited in the management of fungal diseases as an
alternative to synthetic fungicides, the abuse of which may have
consequences on the environment and health. Ethanol extracts
(EE) and water extracts (WE) of three tropical plants, Stachytarpheta
cayennensis (Verbenaceae), Oxalis barrelieri (Oxalidaceae) and
Euphorbia hirta (Euphorbiaceae) were obtained and screened for
their antifungal activity against three major phytopathogenic fungi
of tomato: Fusarium sp., Alternaria sp. and Colletotrichum sp. The
phytopathogenic fungi used across the experiments were isolated in
Cameroon on severely affected tomatoes and their molecular identification
and characterization is ongoing. The antifungal activity was
checked in vitro on different media supplemented with different
concentrations of the extracts. O. barrelieri EE, at the concentration
of 25 mg/ml, inhibited the mycelium growth of Fusarium sp. by
26.8% and remarkably modified its morphology. WE and EE of the
same O. barrelieri inhibited the mycelium growth of Colletotrichum sp. by 43.7% and 50.3% respectively, but showed no inhibition on
Alternaria sp. The phytochemical analysis of these plant extracts
revealed that EE of S. cayennensis was the richest in polyphenols
and flavonoids. EE from O. barrelieri was particularly rich in alkaloids.
The inhibitory effects on the phytopathogenic fungi were possibly
related to the amount of polyphenols and alkaloids obtained
through the extraction. Field experiments are being conducted on
tomato to confirm the action of such extracts in vivo. These findings
may contribute to develop new biofungicides to protect tomato
from some fungal pathogens
Exploiting the microbiome associated with normal and abnormal sprouting rice (Oryza sativa L.) seed phenotypes through a metabarcoding approach
No full textRice germination and seedlings’ growth are crucial stages that influence crop establishment and productivity. These performances depend on several factors, including the abundance and diversity of seed microbial endophytes. Two popular rainfed rice varieties cultivated in Cameroon, NERICA 3 and NERICA 8, were used for investigating the seed-associated microbiome using the Illumina-based 16 S rRNA gene. Significant differences were observed in terms of richness index between normal and abnormal seedlings developed from sprouting seeds, although no significant species evenness index was assessed within either phenotype. Two hundred ninety-two bacterial amplicon sequence variants were identified in seed microbiome of the rice varieties, and principal coordinate analysis revealed that microbial communities formed two distinct clusters in normal and abnormal seedling phenotypes. Overall, 38 bacteria genera were identified, belonging to 6 main phyla. Furthermore, the core microbiome was defined, and the differential abundance of 28 bacteria genera was assessed. Based on the collected results, putative bacterial genera were directly correlated with the development of normal seedlings. For most genera that are recognised to include beneficial species, such as Brevundimonas, Sphingomonas, Exiguobacterium, Luteibacter, Microbacterium and Streptomyces, a significant increase of their relative abundance was found in normal seedlings. Additionally, in abnormal seedlings, we also observed an increased abundance of the genera Kosakonia and Paenibacillus, which might have controversial aspects (beneficial or pathogenic), together with the presence of some genera (Clostridium sensu stricto) that are commonly correlated to sick plants. The putative functional gene annotation revealed the higher abundance of genes related to the metabolic biosynthesis of soluble carbohydrates and starch, tryptophan, nucleotides and ABC transporters in normal seedlings. Data presented in this study may help in further understanding the importance of the seed endophyte microbiome for driving a correct development of rice plants at the early stages and to identify possible beneficial bacteria for technological applications aimed to increase seed quality and crop productivity
Activity of extracts from three tropical plants towards fungi pathogenic to tomato (Solanum lycopersicum)
No full textAntifungal properties were assessed of water and ethanol extracts from the pan-tropical plants Oxalis barrelieri L., Stachytarpheta cayennensis L., and Euphorbia hirta L. against Fusarium oxysporum f. sp. vasinfectum, Alternaria solani Sorauer, and Rhizoctonia solani Kuhn. The plant extracts inhibited fungal growth in vitro at 1.25-20 mg mL-1, and the degrees of inhibition increased in a dose-dependent manner. Ethanol extracts from the plants inhibited fungal growth by 80-100%, while water extracts showed less antifungal activity, with maximum growth inhibition of 62%. Growth inhibition from ethanol extracts was two- to three-fold greater than for water extracts at equivalent concentrations. Antifungal activity of the extracts varied with their content and composition of phenolics, flavonoids, tannins, and alkaloids. In greenhouse experiments, spraying tomato plants (Solanum lycopersicum L.) with ethanol extract from E. hirta at 2.5 mg mL-1 did not cause phytotoxicity, and increased plant size, when compared to untreated plants. Spraying E. hirta ethanol extract on tomato plants infected by R. solani reduced disease severity up to 80%, when compared to non-sprayed plants. These results demonstrate potential of leaf extracts from E. hirta, O. barrelieri, and S. cayennensis as biofungicides for the control of R. solani, A. solani, and F. oxysporum, which are among the most important causal agents of tomato diseases
Phenolic compounds profile of water and ethanol extracts of Euphorbia hirta L. leaves showing antioxidant and antifungal properties
No full textThe bioactive chemical constituents of water and ethanol extracts of Euphorbia hirta L. leaves have been identified and quantified using an un-targeted mass spectrometric approach. The study allowed the tentative identification of 123 individual phenolic compounds and 18 non-phenolic phytochemicals, most of them described in Euphorbia hirta L. leaves for the first time. Gallotannins, hydroxybenzoic and hydroxycinnamic acids were the most abundant phenolic classes in Euphorbia hirta L. leaves, representing together the 71.5% (26.3%, 25.2% and 20%, respectively) of the total amount of identified phenolics. The main phenolic compounds detected were tri-O-galloyl-glucose isomers, feruloyl-coniferin, tetra-O-galloyl-glucose isomers, di-O-galloyl-glucose isomers, ethyl-gallic acid, protocatechuic acid-O-pentoside-O-hexoside, 5-O-caffeoyl-quinic acid trans isomer and digalloyl-quinic acid. Feruloyl-coniferin was found to be approximately six times more concentrated in the ethanol extract with respect to the water extract. The ethanol extract exhibited higher ABTS (1338.3 ± 85.3 and 802.3 ± 91.0 μmol ascorbic acid equivalent/gram of dry extract, respectively) and superoxide anion (2014.6 ± 78.6 and 1528.0 ± 111.7 μmol ascorbic acid equivalent/gram of dry extract, respectively) scavenging abilities than the water extract. Additionally, the ethanol extract also showed a remarkable anti-fungal effect against Fusarium oxysporum f. sp. vasinfectum, Alternaria solani and Rhizoctonia solani. This study provides new information about Euphorbia hirta L., offering reasons to promote this plant species as rich source of phenolics and an excellent source of antifungal molecules that might have a prospective use in controlling fungal diseases of vegetable crops
Chemical characterization of an aqueous extract and the essential oil of Tithonia diversifolia and their biocontrol activity against seed-borne pathogens of rice.
No full textThe high cost of chemical pesticides and their negative impact on the environment prompted the search for natural pesticides from plants. The objective of our study was to control rice seed pathogenic fungi and bacteria using aqueous extract and essential oil from Tithonia diversifolia leaves. We obtained aqueous extract and essential oil, respectively, by maceration and hydrodistillation; the antimicrobial activities were determined in vitro on a solid medium by the food poisoning method. The secondary metabolites were determined by qualitative and quantitative assays; the chemical composition of the essential oil obtained from Titonia diversifolia was studied using gas-chromatography coupled with mass spectrometry. The results showed that phenols, tannins, flavonoids, alkaloids, terpenoids, sugars and saponins were present in the aqueous extract. The essential oil contained mainly hydrocarbonated, oxygenated monoterpenes, terpenoids and sesquiterpenes. α-terpineol (20.3%), eucalyptol (14.6%), camphor (14.3%) and α-pinene (13.5%) as the main compounds. Regarding the antimicrobial activity, all tested bacteria were sensitive to aqueous extract and essential oil. The activity of the aqueous extract on the tested fungi showed an inhibitory concentration 50 (IC50) of 50 mg/mL against Bipolaris oryzae and Fusarium moniliforme. The activity of the essential oil on bacteria and fungi showed MIC of 125 μg/mL (Xanthomonas oryzae pv. oryzae and Pseudomonas fuscovaginae) and MFC of 5000 μg/mL (Bipolaris oryzae and Fusarium moniliforme). These results allow us to consider Tithonia diversifolia as a potential source of natural biopesticides against rice seed-borne pathogens
Memoir characteristics of Julienne Eden Bušić's prose
No full textMemoari su jedan od modela autobiografske proze u kojemu autor nastoji problematizirati političku, povijesnu ili socijalnu stvarnost u kojoj je živio i djelovao. Najčešće se radi o autoru koji je poziciju pripovjedača stekao zahvaljujući svom društvenom položaju, a iz njegova položaja mogu se iščitati i razlozi koji su ga naveli na pisanje. Cilj je ovoga rada iznijeti memoarske odrednice u Ljubavnicima i luđacima Julienne Bušić. Najprije se iznosi kratka biografija autorice, kao i recenzije koje su o Ljubavnicima i luđacima pisali književni teoretičari i kritičari. Rad je podijeljen na dva dijela. Prvi je dio teorijski u kojemu se predstavljaju književni žanrovi koji se uz djelo najčešće vezuju. Iznose se definicije i karakteristike autobiografije, kao i za temu relevantna podjela suvremene hrvatske autobiografije Helene Sablić Tomić. Nakon toga definiraju se memoari, opisuje povijest žanra, osvrće na vjerodostojnost memoara kao povijesnih izvora i navode osnovne razlike između memoara i autobiografije u užem smislu. U drugom se dijelu analizira književni predložak. Najprije se iznosi kratak opis Ljubavnika i luđaka, s naglaskom na potvrdu autobiografičnosti teksta. Potom se prelazi na najistaknutiji dio rada, a to je analiziranje zastupljenosti memoarskih karakteristika u samom predlošku, pri čemu se opisuje autoričin položaj u izvanjezičnoj stvarnosti, retorička priroda teksta, i njegov sadržaj.Memoirs are one model of autobiographical prose in which the author seeks to problematize the political, historical or social reality in which he lived. Most often it is the autor who has acquired the position of narrator thanks to his social position from which we can also read the reasons that led him to writing. This paper deals with the characteristics of a memoir found in Julienne Bušić's Lovers and Madmen. The first part of the paper deals with a short biography of their author, as well as the reviews written about the work by theorists and critics. The work has two parts. The first part is theoretical and it is about the literary genres to which novel belongs. It contains the definitions and the characteristics of an autobiographical work, as well as the division of contemporary Croatian autobiographical works which is relevant for the thesis. Following are the definitions of a memoir. The history of the genre is described and plausibility of memoirs as historical sources, as well as the main differences between memoirs and autobiographies, in the strict sense of that term. The second part brings the analysis of the literary work. First, there is a short description of Lovers and Madmen. The emphasis is on confirming that the work is autobiographical. Following, there is the main part of the work with the analysis of the number of memoir characteristics found within, where the author's position outside of the literar
Mère Julienne du Rosaire et l'adoration : exploration d'un chemin de vie spirituelle
No full textS’inscrivant au carrefour de la théologie de la vie spirituelle et de l’histoire de la spiritualité chrétienne, la recherche explore l’oeuvre doctrinale de Julienne Dallaire (1911-1995). Mieux connue sous le nom de Mère Julienne du Rosaire, cette spirituelle québécoise – fondatrice de la congrégation des Dominicaines Missionnaires Adoratrices – développe une spiritualité ancrée dans une contemplation du Christ, où l’Écriture et la Tradition de l’Église sont largement convoquées. Une lecture approfondie de son héritage manuscrit permet de constater que l’adoration y occupe une place centrale et y assure une fonction intégratrice. Dès lors, pour une première approche du corpus, l’intérêt de privilégier la piste de l’adoration comme thème principal de la thèse s’est naturellement imposé. Le choix d’étudier les écrits d’un auteur spirituel procède de la conviction que l’expérience chrétienne est un réel lieu théologique, comme l’ont largement montré au vingtième siècle des théologiens de la vie spirituelle tels que Charles-André Bernard ou François-Marie Léthel. Au plan méthodologique, outre un procédé descriptif visant à établir les présupposés nécessaires au niveau historique, la démarche d’investigation des documents transmis par Julienne est essentiellement inductive. Elle fait appel à des outils d’analyse littéraire – rhétoriques, narratifs et pragmatiques –, qui ont l’avantage de favoriser une appropriation plus objective du contenu des textes, en tenant compte de leurs genres respectifs. Dans ce domaine, la recherche bénéficie de l’expertise développée par Thérèse Nadeau-Lacour. Les résultats obtenus au terme de ce processus exploratoire laissent apparaître divers éléments bibliques, christologiques et anthropologiques par lesquels Julienne opère un déplacement majeur dans les conceptions « traditionnelles » de l’adoration. Tout en rappelant la signification naturelle de cette réalité, Julienne invite à en découvrir la nouveauté apportée par le Christ. La distinction qu’elle effectue entre le Christ adorable et le Christ adorateur se révèle fondamentale. Mettant en lumière la spécificité de l’union hypostatique, propre à l’Incarnation du Christ, elle amène son lecteur à envisager non seulement le caractère adorable de la personne du Christ, mais le dynamisme adorateur qui sous-tend toute son existence. La réflexion s’ouvre ainsi à la dimension trinitaire de l’adoration et à la relation d’alliance qu’elle suppose. Ce point de vue permet à Julienne d’éclairer l’acte d’amour par lequel le Christ s’offre pour la gloire de Dieu et le salut du monde, un acte qui se perpétue dans l’éternité et demeure toujours actuel dans le sacrement de l’autel, grâce à l’événement du Jeudi saint. De ces assises christocentriques se dégage une anthropologie théologique qui, fondée sur les dons du baptême et de l’Eucharistie, convie le croyant à devenir conforme au Christ dans le mystère de sa vie adoratrice. L’approche contribue à rendre explicite le chemin spirituel manifesté dans le quatrième Évangile : dans le Christ, toute la vie participe de cette attitude fondamentale qu’est l’adoration « en esprit et en vérité ». Julienne rassemble ses compréhensions sous l’expression « dévotion au Coeur Eucharistique ». Elle fait de la Vierge Marie le modèle par excellence de cette spiritualité. Dans l’horizon théologique actuel, la proposition de Julienne se révèle complémentaire et, à certains égards intégratrice, de la perspective sacramentaire qui, au cours des dernières décennies, a largement – et presque exclusivement – occupé les discussions concernant l’adoration. Son enseignement à ce sujet convoque à redécouvrir et/ou à initier d’autres voies fécondes, anticipant dans un premier temps l’impulsion donnée par le concile Vatican II puis, dans un second temps, la déployant. À partir des ouvertures que la démarche théologique réalise, les conclusions suggèrent des pistes d’explorations futures dans des domaines aussi variés que l’exégèse biblique, la liturgie et même l’oecuménisme.Situated at the crossroads between the theology of spiritual life and the history of Christian spirituality, the research explores the doctrinal work of Julienne Dallaire (1911-1995). Better known as Mother Julienne of the Rosary, this spiritual person from Quebec – foundress of the congregation of the Dominican Missionary Adorers – develops a spirituality rooted in a contemplation of Christ where Scripture and Church Tradition are widely called upon. An in-depth reading of her manuscript heritage shows that adoration occupies a central place in it and serves an integrative function. Thus, for a first approach to the corpus, focusing on the subject of adoration as the main theme of the thesis naturally imposed itself. The choice to study the writings of a spiritual author stems from the conviction that the Christian experience is a real locus theologicus as was widely pointed out in the twentieth century by theologians of spiritual life, such as Charles-André Bernard or François-Marie Léthel. At the methodological level, in addition to a descriptive process aiming to establish the necessary presuppositions at the historical level, the process of investigation of the documents transmitted by Julienne is essentially inductive. It uses tools of literary analysis – rhetorical, narrative and pragmatic – which have the advantage to favour a more objective appropriation of the content of the texts, taking into account their respective genres. In this field, the research benefits from the expertise developed by Thérèse Nadeau-Lacour. The results at the end of this exploratory process reveal various biblical, christological and anthropological elements through which Julienne operates a major shift in the « traditional » ways of conceiving adoration. While recalling the natural meaning of this reality, Julienne helps discover the newness brought by Christ. The distinction she makes between the adorable Christ and the adoring Christ is fundamental. By bringing to light the specificity of the hypostatic union proper to the Incarnation of Christ, she leads her reader to consider not only the adorable character of the person of Christ, but the worshiping dynamism that underlies his whole existence. Reflection thus opens up to the Trinitarian dimension of adoration and to the covenantal relationship it implies. This point of view allows Julienne to bring to light the act of love by which Christ offers himself for the glory of God and the salvation of the world, an act that is perpetuated in eternity and is always present in the Sacrament of the altar, because of the event of Holy Thursday. From these christocentric foundations emerges a theological anthropology which, based on the gifts of baptism and Holy Eucharist, invites the believer to become Christ-like in the mystery of his adoring life. The approach helps to make explicit the spiritual path shown in the fourth Gospel: in Christ, all life participates in this fundamental attitude of adoration « in spirit and in truth ». Julienne brings together her understandings under the expression « devotion to the Eucharistic Heart (of Jesus) ». She considers the Virgin Mary as the model par excellence of this spirituality. In the current theological horizon, Julienne's proposal is complementary and, in some respects, has an integrating capacity, with regards to the sacramental perspective of recent decades, which has largely – and almost exclusively – occupied the discussions concerning adoration. Her teaching on this subject invites to rediscover and/or to initiate other fertile approaches, anticipating first of all the impetus given by the Second Vatican Council and then secondly, deploying it. From the openings that the theological research achieves, the conclusions suggest paths for future exploration in areas as varied as biblical exegesis, liturgy and even ecumenism
Evaluation of Antifungal Potential of Ocimum gratissimum Extracts on Two Seedborne Fungi of Rice (Oryza sativa L.) in Cameroon
No full textDoes Sea Ice Influence Greenland Ice Sheet Surface-melt?
No full textRecent decreases in Arctic sea ice and increases in Greenland ice sheet surface-melt may have global impacts, but the interactions between these two processes are unknown. Using microwave satellite data, we explore the spatial and temporal covariance of sea ice extent and ice sheet surface-melt around Greenland from 1979 to 2007. Significant covariance is discovered in several loci in the late summer, with the strongest covariance in western Greenland, particularly in the southwest (Kangerlussuaq). In this region, wind direction patterns and a statistical lag analysis of ice retreat/advance and surface-melt event timings suggest that sea ice extent change is a potential driver of ice sheet melt. Here, late summer wind directions facilitate onshore advection of ocean heat, and enhanced melting on the ice sheet commonly occurs after reductions in offshore sea ice. Hence, this study identifies for the first time the covariability patterns of sea ice and ice sheet melt and suggests that a retreating sea ice margin may enhance melting over the ice sheet.Peer reviewe
Analysis of engineering wake model validation and calibration with historical data from OWEZ wind farm
No full textWind turbines are often placed together in wind farms for economic considerations. This causes wake interactions between turbines, resulting in significant power losses. Models that predict these wake losses are critical for estimating wind farm power output and developing strategies to mitigate the wake effect, such as wind farm control. For these applications, engineering wake models are favoured for their computational efficiency. Hence, the validation and improvement of these models is an ongoing area of research. Currently, consensus on the accuracy of engineering wake models is absent in the literature. Existing studies employ varying validation strategies that impact the perceived model accuracy. Furthermore, proposed model improvements often lack quantitative evaluation, limiting the generalisability of the results. Additionally, the potential benefits of calibrating wake model parameters are recognised, yet research on calibration methods and the impact thereof is limited. This thesis addresses this scientific gap by proposing a holistic framework for the validation and calibration of engineering wake models. The framework combines best practices from literature. First, it accounts for wind direction uncertainty in historical wind farm data. Additionally, it corrects model inputs by including heterogeneous inflow wind speeds. Finally, it offers a methodology for parameter calibration to improve the model's accuracy using historical wind farm data. The overarching framework employs both quantitative and qualitative validation methods to mitigate the impact of experiment design and enable a thorough evaluation of model improvements. The effectiveness of this framework is demonstrated through a case study with SCADA data from OWEZ wind farm and four engineering wake models from the popular control-oriented wake modelling tool FLORIS. Results show that wind direction uncertainty in SCADA d|ata must be included when validating wake models for specific wind directions or sectors. Additionally, incorporating heterogeneous inflow wind speeds reduced the absolute turbine error by up to 20%. Furthermore, it is demonstrated that calibrating model parameters significantly improves model accuracy. The resulting error reductions reach up to 92% for individual turbines and 65% at farm-level, i.e., for all turbines collectively. Furthermore, results revealed that while the performance of the different models converges post-calibration, differences persist in various scenarios with numerous wake interactions. In these cases, the CC and TurbOPark models outperform the Jensen and GCH models. Through this holistic framework and the demonstrated potential of model parameter calibration, a path forward is paved for further model improvement in a systematic and quantitative manner.Mechanical Engineering | Systems and Contro
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