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DRUG DELIVERY NANOSYSTEMS AS PLANT “VACCINES”: FABRICATION AND ASSESSMENT OF THEIR USE FOR PLANT PROTECTION AGAINST BROAD HOST-RANGE NECROTROPHIC PATHOGENSPablo Vega (9760526) 14 December 2020 (has links)
<p>Drug-delivery nano-systems enhances the potency of bioactive
molecules due to its increase membrane permeability, as a result of their
sub-cellular size. The concept of engineered nano-carriers may be a promising
route to address confounding challenges in agriculture that could lead to an
increase in crop production while reducing the environmental impact associated
with crop protection and food production. A key motivation of this work is to
evaluate the potential use of drug delivery nanosystems in agriculture,
especially in the area of disease control. To this end, identifying the most
suitable materials to serve as carrier and cargo is imperative. Understanding
their bioactive properties and their physical-chemical characteristics is
critical because these influences not only their biological effects on plants
and environmental impact, but also, the fabrication process and potential
scaling-up, enabling practical and relevant field applications in the future. </p>
<p> </p>
<p>In this work, chitosan was selected as nano-carrier material
because of its biological and chemical properties. The chemical structure of
chitosan allows spontaneous assemble of core-shell like nanostructures via
ionic gelation, has enabled it to be used as nano-carrier biomaterial intended
for delivery of bioactive cargo. In agriculture, the use of chitosan is of
special interest due to its immune-modulatory activity elicited in plants.
However, due to its inherent molecular heterogenicity, the formulation and
fabrication of stable and low inter-batch variability chitosan nanocarriers via
ionic gelation is difficult and time consuming.</p>
<p> </p>
<p>A myriad of different bioactive molecules has been tested as
payload, encapsulated into chitosan-based delivery nano-systems for a range of purposes
ranging from biomedicine, pharmaceutical, food and agriculture. In this work
plant derived essential oils were selected as bioactive payload. Essential oils
are at the core of the plant communication process with their phytobiome,
including plant pathogens. Molecules from essential oils can carry an air-borne
message serving as a plant-to-plant communication system (a phenomenon known as
allelopathy) that activate the plant defense mechanisms. Encapsulation of
essential oils into chitosan nanocarriers is only possible by forming
nano-emulsions. </p>
<p>Despite the potential benefits from the use of chitosan and
essential oils in agriculture, its use at a large scale has been hindered by
the overwhelming inconsistencies in the current literature, regarding their
formulation and fabrication. This work addresses these problems and presents
evidence that support the feasibility of producing highly chitosan nanocarriers
loaded with essential oils, in a facile and rapid way, using FDA-grade
materials only, without the need of expensive or specialized instrumentation. </p>
<p> </p>
<p>The plant-pathogen compatible interaction between <i>A.
thaliana</i> and <i>B. cinerea</i> was used as biological model to test the
hypothesis that chitosan nano-carriers and essential oil nano-emulsions can
enhance the quantitative disease resistance of plants against broad host-range
necrotrophic pathogens. We found that these treatments display a dose-dependent
response in plants triggering a systemic immune response. Image-based
phenotyping analysis showed that chitosan nanoparticles alone, as well as
loaded with d-limonene, significantly enhanced the disease resistance of <i>A.
thaliana</i> against <i>B. cinerea</i>. Nano-emulsions using essential oils
from cinnamon, clove, coriander and red thyme also produced similar effects on
the defense response in the pathosystem under study. Functional analysis of the
differentially expressed genes from treated plants revealed that these
treatments up-regulated the biological process involved in “stress management”,
while down-regulated the biological process required for normal growth and
development during ideal, non-stressful conditions.</p>
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Characterization of a Major Quantitative Disease Resistance Locus for Partial Resistance to <i>Phytophthora sojae</i>Karhoff, Stephanie 04 September 2019 (has links)
No description available.
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Studies in the Management of Pythium Seed and Root Rot of Soybean: Efficacy of Fungicide Seed Treatments, Screening Germplasm for Resistance, and Comparison of Quantitative Disease Resistance Loci to Three Species of <i>Pythium and Phytophthora sojae</I>Scott, Kelsey L. 15 August 2018 (has links)
No description available.
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Genetic and biochemical characterization of resistance to bacterial canker of tomato caused by <i>Clavibacter michiganensis</i> subsp. <i>michiganensis</i>Coaker, Gitta Laurel January 2003 (has links)
No description available.
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Pouvoir pathogène et résistance : implication des toxines dans l’interaction carotte-Alternaria dauci / Resistance and pathogenicity : how toxins are involved in the carrot-Alternaria dauci interactionCourtial, Julia 18 April 2019 (has links)
La brûlure foliaire causée par Alternaria dauci est la maladie foliaire la plus dommageable pour les cultures de carottes, entravant la récolte mécanique. Seuls des cultivars partiellement résistants sont connus et commercialisés, mais leurs niveaux de résistance sont insuffisants. Les mécanismes de la résistance quantitative des plantes aux agents pathogènes sont mal caractérisés. Nous avons choisi d'étudier ces mécanismes dans l'interaction A. dauci-carotte. Auparavant, plusieurs résultats expérimentaux convergents ont montré que la résistance aux toxines fongiques entre en jeu dans cette interaction. Les tests de toxicité effectués avec des suspensions cellulaires de carotte ont révélé une corrélation entre la résistance des carottes à A.dauci et la résistance des cellules de carotte aux exsudats du champignon. Ces résultats nous ont incités à étudier les toxines impliquées dans le pouvoir pathogène d'A. dauci et afin de pouvoir étudier la réponse de la plante à celles –ci. En utilisant les profils HPLC de la phase organique d'exsudats de différentes souches de champignons, nous avons découvert une corrélation entre la production de toxines et l’agressivité de ces souches suggérant que la production de toxines joue un rôle majeur dans l’interaction A. dauci-carotte. Nous avons effectué l'extraction, la purification et la caractérisation de l'une des molécules candidates que nous avons nommé aldaulactone. Nous avons démontré sa toxicité grâce à un nouveau protocole de quantification de cellules mortes et vivantes. Un transcriptome d’A. dauci et une étude de l’expression des gènes en fonction de la production d’aldaulactone ont été utilisées pour étudier sa voie de biosynthèse. / Alternaria leaf blight, caused by the necrotrophic fungus Alternaria dauci, is the most damaging foliar disease of carrots, especially because it hampers leaf-pull harvesting. Only partially – and insufficiently – resistant cultivars exist. In general, partial resistance mechanisms are poorly understood, so we chose to study them in this interaction. Previous results obtained in the lab highlighted a correlation between plant resistance to the fungus and plant cell resistance toward fungal toxins. It was also shown using carrot cell suspensions that fungal exudates’ toxicity was only present in the organic phase. These results led us to better characterize the toxins produced by A. dauci, in order to get a deeper understanding of carrot cell resistance mechanisms toward those toxins. HPLC analysis of the exudates from different fungal strain uncovered a correlation between toxin production and the aggressiveness of the fungal strains, suggesting that toxin production is an important component of said aggressiveness. We extracted, purified and characterize one of these candidates, and named it aldaulactone. Using a new image analysis protocol, we demonstrated the toxicity of Aldaulactone on carrot cell suspensions. Transcriptomic data from Alternaria dauci were used to explore the biosynthesis pathway of Aldaulactone. Candidate Genes were selected and their level of expression compared with aldaulactone production in various A. dauci cultures.
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A study of Phytophthora sojae Resistance in Soybean (Glycine max [L. Merr]) using Genome-Wide Association Analyses and Genomic PredictionRolling, William R. 30 September 2020 (has links)
No description available.
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Soybean QTL Mapping and Candidate Gene Identification for Pythium irregulare and Phytophthora sojae Partial Resistance; and Root-Knot Nematode Induced Suppression of Gene SilencingNauth, Brittany J. 29 October 2014 (has links)
No description available.
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