Thèses : « Soilborn pathogen »

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Al-Gharabally, Dunia Hashim. « Biological control of soilborne plant pathogens by greenwaste compost ». Thesis, University of Exeter, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.393320.

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Fichtner, Elizabeth Jeanne. « Abiotic pathogen suppression physiology and biology of aluminum toxicity to soilborne fungi / ». NCSU, 2003. http://www.lib.ncsu.edu/theses/available/etd-10222003-020101/.

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An interdisciplinary approach was utilized to study the toxicity of aluminum (Al) to soilborne plant pathogens with the goal of developing a pathogen-suppressive potting medium containing non-phytotoxic, Al-organic matter complexes. Toxicological studies addressed the toxicity of monomeric Al species to Thielaviopsis basicola and Phytophthora parasitica and documented the sensitivity of these organisms to the metal. Until recently, research on Al-toxicity to fungi has only focused on the trivalent Al cation (Al³⁺) which is also considered the most phytotoxic Al ion. The toxicity of Al-hydrolysis species to fungi were tested by modeling in vitro test solution equilibria using GEOCHEM-PC and correlating the predicted values of Al-species activities with reduction in spore production of the two pathogens. Chlamydospore production of T. basicola was negatively correlated with Al³⁺ activity, whereas inhibition of sporangia production of P. parasitica was related to the activity of multiple monomeric Al species. Toxicity of Al to T. basicola was observed in solutions containing ≥ 20 micromolar Al. Sensitivity of P. parasitica to Al was observed at < 1.0 micromolar Al, suggesting that P. parasitica is more sensitive to Al than T. basicola. Using fluorescence microscopy, the localized accumulation of Al in pathogen tissues was detected using lumogallion, an Al-specific, fluorescent stain. Accumulation of Al was observed under various chemical conditions, ranging from salt solutions to more complex systems containing Al-peat complexes. An ecological approach was applied to study the dynamic interactions of soil chemical and physical properties with soil microflora for the suppression of P. parasitica in a medium amended with Al₂(SO₄)₃ and composted swine waste (CSW). Abiotic and biological mechanisms of pathogen suppression were incorporated into the CSW-amended medium. Al-mediated suppression resulted in reduction of sporangia production in medium exhibiting K-exchangeable Al levels > 2 micromolar Al. Biological suppression also resulted in reduction of sporangia production and this suppression was maintained after Al levels dropped below the threshold necessary for abiotic suppression. The incorporation of abiotic and biological control mechanisms into a potting media may facilitate suppression of a wide range of soilborne pathogens and enhance applicability of disease-suppressive media in a disease management strategy.

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Tilston, Emma Louise. « Phytoprotective properties of composted recycled organic matter against soilborne plant pathogens ». Thesis, University of Exeter, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323987.

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Odom, Jennifer Lorraine. « Evaluation of Field Pea Varieties for Resistance to Fusarium Root Rot Pathogens ». Thesis, North Dakota State University, 2017. https://hdl.handle.net/10365/28500.

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Fusarium root rot is one of the most important diseases of pulse crops, with numerous Fusarium spp. comprising the disease complex. Fusarium solani and F. avenaceum have been reported to be major pathogens in the pea root rot complex, and all commonly grown varieties are susceptible. Greenhouse methods to evaluate peas for resistance to Fusarium root rot resulted in inconsistent disease severity across varieties. In 2015, F. avenaceum infested field plots were more heavily damaged based on emergence and yield than F. solani infested plots, and opposite trends were observed in 2016. Differences in root rot severity between years could be due to F. solani infestation causing more damage under warmer temperatures, while plots infested with F. avenaceum caused more damage under cooler temperatures. These results highlight the difficulties observed when screening for soil-borne pathogens, and the increased difficulties when a pathogen complex and changing environmental conditions are involved.

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Kapsalis, Apostolos V. « Biological control of soilborne pathogens causing damping-off symptoms in cotton plants ». Thesis, University of Reading, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.430919.

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Fang, Lynn. « Biological Indicators Of Compost-Mediated Disease Suppression Against The Soilborne Plant Pathogen Rhizoctonia Solani ». ScholarWorks @ UVM, 2015. http://scholarworks.uvm.edu/graddis/456.

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Compost can suppress soilborne plant pathogens that cause significant damage on globally important food crops. However, reports of plant pathogen suppression are inconsistent likely because there are no established standards for feedstock material, application rate, and maturity age upon application. Excellent results can be achieved in greenhouse trials, but field applications are much less reliable. Disease suppression occurs through the activity of biocontrol organisms (direct antagonism), and general microbial competition. Biocontrol species are hypothesized to colonize the pile during the curing phase, but single species may not be as important as microbial consortia. Substrate composition during maturation may give rise to a suppressive microbial community. More research is needed to understand the relationships between feedstock, maturity, and production process on compost microbial ecology. The thesis had two main objectives: 1) identify biological indicators in compost that could (a) characterize maturity, process, and feedstock, and (b) predict disease suppression against R. solani, and 2) identify bacterial and fungal community composition and/or structure that is associated with suppression of soilborne disease. Rhizoctonia solani is a facultative saprophytic fungus and soilborne plant pathogen that attacks many globally important food crops and turfgrass. Prior research suggests that managing carbon quality and compost maturity will alter relative competition between biological control microbes and the R. solani pathogen. The pathogen is responsible for economic losses to organic vegetable production in Vermont and there are no available methods to manage the disease that meet organic certification. R. solani on radish was chosen as a model system given its global importance, competitiveness affected by carbon quality, and lack of disease management options for organic production. Compost samples were most abundant in the bacterial phyla Proteobacteria and Bacteroidetes, and known biocontrol species were not detected in abundance. Compost samples did not differ significantly in fungal community composition, suggesting a dominance effect from the native soil fungal community. Overall, anaerobic digestate and vermicompost were most suppressive against R. solani. Thermophilic composts were not very suppressive overall, though a specially made hardwood bark compost was comparable to the suppressiveness of vermicompost application. Ecoenzyme analysis was able to integrate information on environmental substrate composition, microbial nutrient acquisition, and microbial community metabolism, offering the best view of current ecological conditions in compost. Ecoenzyme analysis showed that the most suppressive composts, anaerobic digestate and vermicompost, were most nutrient limited. All compost samples were severely nitrogen (N) limited, and anaerobic digestate and vermicompost were severely limited in both N and phosphorus (P). The additional P limitation may support non-pathogenic species to outcompete R. solani. The key to disease suppression may lie in matching up the ecology of the plant pathogen with the ecology of biocontrol, which may be engineered in compost.

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Filgueira, Pimentel Mirian. « EVALUATION AND FUNCTIONAL CHARACTERIZATION OF BIOCONTROL AGENTS TARGETING SELECT SOILBORNE PATHOGENS OF SOYBEAN ». OpenSIUC, 2021. https://opensiuc.lib.siu.edu/dissertations/1886.

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Soybean crops are vulnerable to a wide range of pathogens that reduce yield and cause extensive losses worldwide. In the United States, the soilborne pathogens Pythium spp., causing soybean damping-off, and Fusarium virguliforme, causing sudden death syndrome (SDS) of soybean, have been among the top diseases that most reduced soybean yields. This study demonstrated that biological control using native fungal antagonists could be a powerful tool to integrate with current management strategies for more efficient control of Pythium damping-off and SDS in soybean. Trichoderma spp. and Clonostachys rosea demonstrated the ability to mycoparasitize and antagonize the pathogens using different mechanisms and exhibited a protective effect on soybean in field conditions. The development of an efficient biological control program for disease management relies on a deep understanding of the BCA-pathogen interaction’s biology. This research also uncovered the molecular mechanisms involved in the F. virguliforme-T. afroharzianum interaction by using a dual RNAseq approach. Significant changes in both fungal organisms’ transcriptomes were discovered at different stages in their interaction. The results provided here can contribute to the future implementation of effective biological control programs for soybean. The benefits may also extend to other crops.

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Kalonji, Kabengele Muzela J. B. « Evaluation of three fungicides for control of soilborne diseases of lettuce seedlings ». Diss., University of Pretoria, 2008. http://hdl.handle.net/2263/29549.

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Lettuce (Lactuca sativa L.) seedlings diseases caused by soilborne pathogens are characterised by root rot, stem rot and damping-off of the seedlings that can occur at any time during growth. Fusarium solani, Pythium ultimum and Rhizoctonia solani are known to be the important destructive pathogens of lettuce, causing severe yield losses in South Africa. The aim of this research was to evaluate the effects of three selected fungicides to control these pathogens on lettuce seedlings. In this study the fungicides metalaxyl (Apron®), fludioxonil (Celest®) and mefenoxam (Subdue®) were applied at two concentrations as single and double doses on lettuce seedlings to determine their efficacy to control the pathogens Fusarium solani, Pythium ultimum and Rhizoctonia solani after significant reduction of mycelia growth was observed in vitro. Cultures of P. ultimum (UPGH024), R. solani (UPGH122) and F. solani (UPGH122) were obtained from the culture collection of the Department of Microbiology and Plant Pathology, University of Pretoria and cultivated on PDA for 2 days at 25ºC. Pasteurised soil was artificially inoculated with these pathogens. For the first experiment lettuce seeds were planted in polystyrene seedling trays at a depth of 1.0 cm. There were four replications of 50 seeds per treatment. In Experiment 2 pots (12 cm x 7 cm) were filled with pasteurised growing medium and 3-week old seedlings were transplanted. There were three replications of six pots containing three plants each. Seedling trays and pots were drenched with fungicides and placed in a randomised block design in a controlled environment room at 20- 26°C with a 12h-light/dark regime. The seedling trays and pots were rotated daily in the room. Seedling trays and pots were watered daily to maintain field capacity. The seedlings were able to grow larger in the pots than in seedling trays. It was confirmed that the treatment with fludioxonil (Celest®) at double and single dose inhibited the growth of the three fungi F. solani, P. ultimum and R. solani on lettuce seedlings without causing phytotoxicity. All three fungicides significantly reduced the diseases caused by the three pathogens. These findings are consistent with previous reports that fludioxonil, metalaxyl and mefenoxam can control oomycete fungi. There are few registered fungicides for the control of Fusarium solani, Pythium ultimum and Rhizoctonia solani on lettuce, therefore further work will aim to confirm these results in the field.
Dissertation (MInstAgrar)--University of Pretoria, 2008.
Microbiology and Plant Pathology
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au, nolad@iprimus com, et Nola Kim D'Souza. « Pathosystem development, characterisation and genetic dissection of the soil pathogen Phytophthora medicaginis and the model legume Medicago truncatula : a view to application of disease resistance in susceptible legume species ». Murdoch University, 2009. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20090423.105414.

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Phytophthora medicaginis is an important soil-borne oomycete pathogen of lucerne (Medicago sativa) and chickpea (Cicer arietinum) within Australia and overseas. To understand the host/pathogen interaction, a pathosystem was developed using the model legume Medicago truncatula. Using the resources developed for genetics and molecular characterisation in this model plant, the aim of this research was to understand the interaction between M. truncatula and P. medicaginis, with a view to improving resistance to this important pathogen in related legumes. To observe and characterise the interaction between M. truncatula and P. medicaginis, a pathosystem was developed by first screening a germplasm collection of 99 M. truncatula accessions. This revealed a continuous distribution in disease phenotypes with variable extremes in natural resistance to P. medicaginis culture UQ5750, isolated originally from M. sativa. P. medicaginis zoospore inoculation of 1-2 week-old seedlings in glasshouse experiments proved to be a robust and repeatable method to consistently confirm the responses observed for six key M. truncatula accessions; SA8618 and SA8623 exhibit high natural resistance to this pathogen, accession A17 is moderately resistant, A20 is moderately susceptible and accessions Borung and SA30199 are susceptible. To characterise the genetic basis of resistance to P. medicaginis, two reciprocal F2 populations from cross pollinations between A17 and Borung and SA8618 and SA30199 were produced and then phenotyped for disease symptoms. Genetic segregation patterns indicated the involvement of a gene with a major effect in both reciprocal populations. In particular, a 3:1 segregation ratio for resistance in the F2 populations from cross pollinations between A17 and Borung indicated the possibility of a single dominant gene for moderate resistance. Further phenotyping of F3 families is required to verify this. A M. truncatula linkage map was constructed using 50 F2 individuals of the A17 X Borung population and 49 F2 individuals from the Borung X A17 population. The map, covering 519.3 cM, is comprised of 84 SSR markers with an average distance between markers of 8.7 cM. These are evenly spaced over 7 linkage groups, including a super linkage group conferred by a translocation event between LG4 and LG8 of accession A17. Quantitative trait locus (QTL) analysis confirmed there was a QTL with a major effect in the A17/Borung reciprocal populations. A significant QTL was determined by quantifying two symptoms of P. medicaginis infection - proportion of dead/chlorotic leaves and root fresh weight. The trait loci for both symptoms were located on the same linkage group within the same region, supporting the putative position of the QTL and the authenticity of its involvement in resistance to P. medicaginis. This QTL was located on LG6 and accounted for 69.5% of the observed variation in proportion of dead/chlorotic leaves or 38.1% of the variation in root fresh weight within the inoculated populations. The effect of this QTL on resistance to P. medicaginis translated into 27.5% less dead/chlorotic leaves or 0.86 g more root fresh weight. Other QTLs with minor effects that are potentially involved in the interaction are located elsewhere on LG6 and LG2. However, the marker density of the linkage map and the population size need to be increased to verify this. In parallel to this, an F7 recombinant inbred line (RIL) population of chickpea (BG212 X Jimbour), developed by breeders at the New South Wales Department of Primary Industries (NSW DPI), was also assessed for the genetic basis of resistance to P. medicaginis. Variance component analysis of phenotype scores for this intraspecific RIL population indicated that 57.15% of the differences in between-family and withinfamily variance could be attributed to a genetic component. However, gene-based markers developed in M. truncatula and established simple sequence repeat (SSR) markers of chickpea were not sufficiently polymorphic in size to produce a linkage map for further QTL analysis. An interspecific cross between C. arietinum and C. echinospermum (Howzat X ILWC246) was also performed by breeders at the NSW DPI to develop RILs. In the duration of this research these interspecific RILs were bred to generation F3 and phenotyping assessment had not been performed. However, marker screening of the parents revealed 122 size polymorphic chickpea SSR markers. A sufficient linkage map could be produced for QTL analysis once field assessment of this population is performed. Initial screening of the M. truncatula gene-based markers on the parents of this interspecific cross also revealed that 50% show a sequence-identified base pair difference. A chickpea linkage map incorporating these markers could be comparatively mapped with M. truncatula. Molecular investigations of the M. truncatula/P. medicaginis pathosystem were performed to elucidate the possible underlying defence mechanisms involved in the observed resistance. To determine the function of ethylene in the resistant response, the characterisation of defence associated mutants of M. truncatula and Agrobacterium rhizogenes-mediated hairy root transformations were employed. Comparison of response to inoculation of an ethylene insensitive mutant of M. truncatula (sickle) with the moderately resistant background genotype A17 showed that sickle was hypersensitive to P. medicaginis. This indicated that ethylene insensitivity was not the source of resistance to this pathogen and importantly that ethylene is a key defence signalling molecule in the moderate resistance of A17 to P. medicaginis. Agrobacterium-mediated hairy root transformations of M. truncatula with 4GCC::Luc constructs, revealed that the production of ethylene and consequently ethylene response factors (ERFs) after inoculation by P. medicaginis was a general defence reaction by all accessions. The two susceptible M. truncatula accessions exhibited a much stronger and earlier response to inoculation than the highly resistant and moderately resistant accessions. This indicated that the resistant response may be directed by a transcriptional component governed by the host genotype, downstream of ethylene production. The M. truncatula/P. medicaginis hairy root transformation assay has scope to be a powerful functional genomics tool for this pathogen interaction. Reverse transcriptase quantitative polymerase chain reaction (RTqPCR) was employed to determine the general patterns of gene expression and function underlying the response to P. medicaginis infection. Relative changes in gene expression of key enzymes in each of the salicylic acid, jasmonic acid, ethylene and isoflavonoid defence pathways and in genes encoding downstream target proteins revealed potential genes involved in the resistance to P. medicaginis. There was a distinct molecular difference in the response between the high and moderately resistant M. truncatula phenotypes to this pathogen. Moderate resistance to P. medicaginis in M. truncatula is possibly mediated by ethylene and involves the considerable induction of pathogenesis related protein 5 (PR5), which was not the same defence response that conferred the high resistance to P. medicaginis. Early and consistent expression of genes encoding key enzymes of the isoflavonoid pathway by the highly resistant accession indicated that phytoalexin response could be associated with the high resistance. Confirmation of the involvement of isoflavonoid phytoalexins in the high resistance response to P. medicaginis merits further investigation.

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Jensen, Alexa Lunt. « Evaluating Nitrogen and Carbon Differences in Standing Litter from Normal and Prematurely Senesced Bromus tectorum Plants ». BYU ScholarsArchive, 2019. https://scholarsarchive.byu.edu/etd/8265.

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Bromus tectorum, an invasive winter annual, has displaced native vegetation throughout the western United States. Bromus tectorum litter influences nutrient cycling near the soil surface as well as plant establishment. Failed seed production of B. tectorum occasionally occurs in the field, with plants exhibiting weak flowering culms that turn straw-colored in spring when normal plants are green or purple in color. Because annual grasses transport most soluble carbon (C) and nitrogen (N) to reproductive organs, seed production failure results in significantly different fates for these nutrients compared with normal plants. As part of larger efforts to understand events leading to large-scale seedling emergence failure (termed die-offs), occasionally observed in near mono-cultures of B. tectorum, we here test the hypothesis that prematurely senesced litter associated with seed production failure has higher soluble C and N than normal litter. C and N concentrations of aboveground biomass were compared for normal and prematurely senesced B. tectorum plants. Two methods were used to cause premature senescence: fungal pathogen infection with Clarireedia capillus-albis and glyphosate herbicide application. In a related experiment, field sampling of normal and prematurely senesced plants under natural conditions was conducted to compare C and N levels in-situ. Herbicide-induced senescence resulted in 1.5 to 2 times greater soluble C concentrations, but fungal infection had no effect on soluble C under experiment conditions. Prematurely senesced litter had increased total N concentrations, resulting in lower C:N ratios. The C:N ratio for prematurely senesced plants (averaged across all studies) was 68:1, whereas mature normal plants averaged 243:1. These findings illustrate failed seed production associated with premature senescence results in B. tectorum litter with significantly higher N concentrations and can result in increased soluble C concentrations. Altered nutrient status may contribute to changes in soil microbial activity, including activity of soilborne pathogens found in die-offs.

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Ellis, Richard John. « Basis for the biocontrol of Pythium by fluorescent pseudomonads ». Thesis, University of Oxford, 1997. http://ora.ox.ac.uk/objects/uuid:980ebd0a-5cd5-4408-858e-55e184e8566a.

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The aim of this thesis was to gain an understanding of the molecular and ecological basis for the biological control of Pythium by fluorescent pseudomonads. A fluorescent pseudomonad biocontrol agent (BCA), Pseudomonas fluorescens 54/96, identified as a potential candidate for commercial development, was analysed together with transposon induced mutants in a variety of assays for anti-fungal activity (Chapter 2). It was revealed that 54/96 had a fungistatic effect generated by a number of different mechanisms, which included nutrient competition and antibiosis. The synecology of this organism with Pythium was then compared to a similar organism (P. fluorescens SBW25) demonstrating a similar degree of anti-fungal activity (Chapter 3). The similarity of the population dynamics of these two strains prompted an examination of the genetic basis for the anti-fungal activity of the second strain, with the intention of comparing with 54/96 (Chapter 4). Again this revealed a multifactorial mode of action of SBW25 against Pythium. Whilst some mutants with reduced anti-fungal activity were deficient in growth on seed exudate others were unaffected, but the mechanisms appeared to be different to those utilized by 54/96. The comparison of strains was expanded to a larger collection of pseudomonad BCAs which were contrasted by a number of phenotypic and genotypic methods (Chapter 5). Various markers were identified which showed commonality within the different classes of BCA, the most useful of which was cyclopropanated fatty acids. These may prove to be a useful marker when screening for new pseudomonad BCAs. It was concluded that a greater understanding of the molecular, physiological and ecological basis of anti-fungal activity of bacterial will lead to the development of biocontrol strategies with improved efficacy.

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Elmore, Whitney Colleen. « Population and identification of mycorrhizal fungi in St. Augustinegrass in Florida and their effect on soilborne pathogens ». [Gainesville, Fla.] : University of Florida, 2006. http://purl.fcla.edu/fcla/etd/UFE0015421.

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Levenfors, Jens. « Soil-borne pathogens in intensive legume cropping - Aphanomyces spp. and root rots / ». Uppsala : Dept. of Plant Pathology and Biocontrol Unit, Swedish Univ. of Agricultural Sciences, 2003. http://epsilon.slu.se/a393.pdf.

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Weeks, James Michael Jr. « Perennial Grass Based Crop Rotations in Virginia : Effects on Soil Quality, Disease Incidence, and Cotton and Peanut Growth ». Thesis, Virginia Tech, 2008. http://hdl.handle.net/10919/35394.

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In 2003 eight peanut and cotton crop rotations were established in southeastern Virginia, 4 of which included 2 or 3 years of tall fescue or orchardgrass grown as high-value hay crops. Each crop rotation was evaluated for changes in soil quality indicators including soil carbon and nitrogen, water stable soil aggregates, plant available water content, bulk density, cone index values, and soil moisture. Cotton and peanut growth and yield were also observed to evaluate changes in crop growth associated with differences in soil quality. Soilborne plant pathogens including root-knot nematode, stubby root nematode, ring nematode, stunt nematode, and Cylindrocladium parasiticum microsclerotia were measured in the spring and fall of each year to determine differences associated with crop rotations. Water stable soil aggregates in 2007 were higher in rotations with 3 years of either perennial grass. Soil moisture tended to be the highest at depths 30 - 60 cm in the 3-year tall fescue rotation in August and September 2007. Cotton in 2006 and peanut in 2007 had higher growth and yield where the annual crop directly followed a perennial grass. Root-knot nematode tended to decrease in all rotations over time. Stubby root nematode populations tended to increase in rotations with either duration of orchardgrass. Including perennial grasses in cotton and peanut rotations has the potential to increase growth and yield as demonstrated in this research.
Master of Science

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Sanabria, Andres SANABRIA. « EFFECTS OF ANAEROBIC SOIL DISINFESTATION COMBINED WITH BIOLOGICAL CONTROL ON ROOT-KNOT NEMATODE AND LETTUCE DROP ». The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1534496965018979.

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Chamoun, Rony. « Molecular and metabolic investigation into the fungal-fungal interaction between the soilborne plant pathogen «Rhizoctania solani» and the mycoparasite «Stachybotrys elegans» ». Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=119556.

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Mycoparasitism, the direct attack of one fungus on another, is a complex process that involves sequential events, including recognition, attack and subsequent penetration and killing of the host. The cellular interaction between Stachybotrys elegans a mycoparasite of the soilborne plant pathogen Rhizoctonia solani begins with molecular and chemical interactions that lead to expression of several genes or components of signaling pathways, and secretion of many metabolite biomarkers. Transcriptional changes of several mycoparasitism-induced genes (oxidoreductase, cytochrome P450 monooxygenase, carboxylesterase, and O-methyltransferase) during an extended period of interaction were associated with the formation of excessive coils and infection pegs which are required for limiting the growth of the pathogen. Hyphae and sclerotia of R. solani triggered different expression patterns of these genes, which is a clear indication that multiple regulatory mechanisms might be involved during the mycoparasitic process. In response to attack, hyphal and sclerotial cells of R. solani had elevated expression of pyridoxal reductase, a precursor of vitamin B6 or its derivatives which are known as antioxidants and quenchers of reactive oxygen species. The high elevated expression of some genes belonging to the mycoparasite and the host suggests that these genes play an important role during the mycoparasitic process and host defense, respectively. As a first step toward understanding the molecular basis of signal transduction during the cross talk between S. elegans and R. solani, the cloning and complete characterization of smkA, the first MAP kinase (MAPK/ERK1/2) gene from S. elegans was accomplished. At the transcriptional level, smkA was significantly induced in response to hyphal parasitism compared to parasitized sclerotia. However, under starvation condition, smkA levels were significantly induced at a later stage of growth. Western blot analysis against ERK1/2 showed an increase in their phosphorylated forms when S. elegans was grown under starvation condition compared to that detected in response to mycoparasitism. A higher abundance of phosphorylated ERK1/2 at the third day of interaction compared to that estimated under starvation condition was detected by applying LC–MS/MS. Direct Infusion Orbitrap MS (DI-MS) and robust bioinformatics tools highlighted a total of 486 metabolites as biomarkers in parasitized cells of R. solani, and in cells from monocultures of R. solani. Carboxylic acids and alkaloids were the predominant chemical groups in parasitized cells compared to those in R. solani monocultures indicating their role in the mycoparasitism. The increase in relative intensity of R. solani-derived indole biomarker, 11-hydroxycanthin-6-one, is indicative of a defense reaction against S. elegans. This study provides new knowledge that can be exploited for plant disease management strategies and for research dealing with biotechnology such as genetic engineering and/or biomarker-assisted plant breeding.
Le mycoparasitisme est un procédé complexe par lequel un champignon en attaque un autre par une série d'événements, soit l'identification, l'attaque et la pénétration subséquente et la mort de l'hôte. L'interaction cellulaire entre Stachybotrys elegans, un mycoparasite du cryptogame Rhizoctonia solani, est caractérisée par des interactions moléculaires et chimiques résultant en l'expression de plusieurs gènes ou composantes de mécanismes de transduction du signal ainsi que la sécrétion de plusieurs métabolites biomarqueurs. Des changements dans la transcription de plusieurs gènes (oxydoréductase, cytochrome P450 monooxygénase, carboxylesterase, et O-méthyltransférase) activés par le mycoparasitisme durant une longue période d'interaction sont associés à l'enroulement et au développement de tubes pénétrants de type infectieux tous deux requis pour limiter la croissance du pathogène. Les hyphes et les sclérotes de R. solani ont initié différents patrons d'expression génique indiquant clairement que plusieurs mécanismes de régulation sont impliqués lors du mycoparasitisme. En réponse à l'attaque, des cellules d'hyphes et de sclérotes ont exprimé abondamment la pyridoxal réductase qui est un précurseur de la vitamine B6 ou de ses dérivés connue pour leur effet antioxydant. Une augmentation dans l'expression de certains gènes appartenant au mycoparasite et à l'hôte suggère que ceux-ci jouent un rôle important lors du mycoparasitisme et de la défense de l'hôte, respectivement. Afin de comprendre la base moléculaire de la transduction du signal durant l'échange entre S. elegans et R. solani, le clonage et la caractérisation complète de smkA, le premier gène codant pour une MAP kinase (MAPK/ERK1/2) chez S. elegans, ont été accomplis. Au niveau de la transcription, smkA a été induit significativement en réponse au parasitisme des hyphes en comparaison avec les sclérotes parasités. Toutefois, en absence de nutriments, les transcrits de smkA ont été induits significativement à un stade de croissance plus avancé. Une analyse par immunobuvardage contre ERK1/2 a démontré une augmentation de la traduction des formes phosphorylées de ces protéines lorsque S. elegans était cultivé en absence de nutriments en comparaison avec la quantité détectée lors du mycoparasitisme. Grâce à la méthode LC–MS/MS, une plus grande concentration des formes phosphorylées de ERK1/2 a été détectée au troisième jour d'interaction en comparaison avec celle estimée en absence de nutriments. À l'aide de la spectrométrie de masse Orbitrap (DI-MS) et d'outils de bioinformatique, 486 métabolites biomarqueurs ont été détectés dans les cellules parasitées de R. solani et dans les cellules provenant de monocultures de R. solani. En comparaison avec les monocultures de R. solani, les groupes chimiques prédominants dans les cellules parasitées étaient les acides carboxyliques et les alkaloids ce qui les associe au mycoparasitisme. L'augmentation de l'intensité relative du biomarqueur d'alkaloid dérivé de R. solani, 11- hydroxycanthin-6-one, est un indicateur de la réaction défensive contre S. elegans. Les résultats de cette recherche apportent de nouvelles connaissances utiles à la phytoprotection et à la recherche en biotechnologie comme le génie génétique et/ou la sélection végétale assistée par biomarqueurs.

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Cruz, Juliana Cristina Sodário [UNESP]. « Preservação, caracterização patogênica e molecular de Plasmodiophora brassicae, agente causal da hérnia das crucíferas ». Universidade Estadual Paulista (UNESP), 2007. http://hdl.handle.net/11449/105444.

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A doença conhecida por hérnia das crucíferas é causada pelo patógeno Plasmodiophora brassicae Woronin, sendo uma das mais importantes e de difícil controle em brássicas. Em virtude da dificuldade de preservação das estruturas de resistência de P. brassicae em condições laboratoriais, por se tratar de um parasita obrigatório, foi desenvolvido um ensaio visando a obtenção de uma técnica eficiente e prática de preservação. Para isto, raízes de diferentes brássicas naturalmente infectadas por P. brassicae, contendo hérnias, foram coletadas de uma mesma propriedade (município de Pardinho - SP), em diferentes períodos, e imediatamente congeladas em freezer a -20°C±2°C. Os tratamentos foram: T1: hérnias congeladas por 389 dias, (rúcula); T2: hérnias congeladas por 242 dias (brócolis); T3: hérnias congeladas por 21 dias (couve-chinesa) e T4: testemunha (sem inóculo). Os testes de patogenicidade, após os diferentes períodos de armazenamento, foram realizados em condições controladas de casa de vegetação (25±2°C), onde em cada planta, de uma variedade suscetível de couve-chinesa (Pak choi), foi inoculado 2mL da suspensão de esporos, dos diferentes tratamentos, na concentração de 107 esporos.mL–1. Cada tratamento contou com seis repetições distribuídas ao acaso. Passadas cinco semanas, após a inoculação, as raízes foram lavadas e avaliadas. Houve diferença estatística significativa entre os materiais avaliados quanto aos diferentes períodos de armazenamento em “freezer”. Os materiais congelados entre 21 a 242 dias preservaram suas características infectivas, sendo este método uma boa opção para a preservação das estruturas de repouso nesse período. Foram realizados testes de patogenicidade e análises moleculares de populações de P. brassicae,...
Disease known as clubroot of crucifers is caused by the pathogen Plasmodiophora brassicae Woronin, and is one of the most important and difficult control crucifer diseases in brassicas. Because of the difficulty in preserving the resistance structures of P. brassicae under laboratory conditions, given that it is an obligate parasite, an assay was carried out to develop a practical and effective technique that would allow further studies to be conducted. On this proposal, roots of different brassica species naturally infected by P. brassicae showing clubroot symptoms were collected in the some grower (Pardinho, SP-city, Brazil) during different seasons, and were immediately frozen at approximately 20°C±2°C. The treatments were: T1: clubroots frozen for 389 days (arugula); T2: clubroots frozen for 242 days (broccoli); T3: clubroots frozen for 21 days (Chinese cabbage), and T4: control (no inoculum). The pathogenicity tests after different storage periods were conducted under controlled greenhouse conditions (25±2°C); each plant of a susceptible variety of Chinese cabbage was inoculated with 2mL of a spore suspension of the various treatments at a concentration of 107spores.mL-1. Each treatment consisted of six replicates distributed at random. The roots were washed and evaluated five weeks after inoculation. There were statistical differences between the materials evaluated with respect to different storage periods in the freezer. Materials kept frozen between 21 and 242 days retained their infective traits. Therefore, this method is a good option to preserve resting spores during this period. In addition, pathogenicity tests and molecular analyses were conducted with P. brassicae populations obtained from infected roots of several production regions of Brazil, on some...(Complete abstract click electronic access below)

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Carter, Mel. « Investigating novel approaches for the integrated control of the soilborne strawberry pathogens Macrophomina phaseolina and Fusarium oxysporum f. sp. fragariae ». DigitalCommons@CalPoly, 2016. https://digitalcommons.calpoly.edu/theses/1628.

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Macrophomina phaseolina (Mp) and Fusarium oxysporum f. sp. fragariae (Fof) are emerging soilborne pathogens causing crown rot and Fusarium wilt, respectively, in commercial strawberry production in California. Fungicides representing eight active ingredients from four different mode of action groups (FRAC groups 1, 3, 7 and 12) were evaluated for their efficacy against each pathogen in vitro and each disease in planta. Fungicide active ingredients were evaluated for their ability to inhibit mycelial growth of both pathogens in vitro. Half-strength potato dextrose agar was amended with six different concentrations (0.01, 0.1, 1.0, 5.0, 10, 50 µg a.i./ml) of seven fungicides in FRAC groups 3, 7 and 12. Concentrations that inhibited fungal growth by 75% (EC75) compared to unamended media were determined for two different isolates each of Mp and Fof and were used to determine fungicide rates for subsequent in planta studies. Tebuconazole strongly inhibited the mycelial growth of both pathogens (average EC75 for Mp was 2.4 ppm; average EC75 for Fof was 7.48 ppm), as did metconazole (average EC75 for Mp was2.53 ppm; average EC75 for Fof was 1.28 ppm). Fludioxonil strongly inhibited mycelial growth of Mp, but had no impact on the growth of Fof. Penthiopyrad, fluopyram, flutriafol, and flutolanil were less effective at inhibiting fungal growth of either fungus. Greenhouse in planta studies evaluated twenty-four fungicide treatments (eight fungicides at low, med and high rates) that were drench applied to infested potting media two days prior to planting of pathogen susceptible strawberry cultivars (San Andreas for Mp and Monterey for Fof) and again at day 21. Controls were a non-inoculated and an inoculated water-drench treatment. Buried inoculum was recovered at days 2 and 23 and plated on selective media for colony forming unit (CFU) quantification. Plant disease assessments were made each week for 11 weeks. An analysis of variance (ANOVA) of CFUs revealed no significant differences (p > 0.05) among treatments and when compared to the non-treated control for both Mp and Fof, but showed significant decreases (p < 0.05) in CFUs between weeks 1 and 3 for both Mp and Fof. An ANOVA for disease assessments in the form of area under the disease progress curve (AUDPC) showed significant decreases of disease severity in treatments with penthiopyrad only (low, medium and high rates) (p < 0.05). There were no significant differences (p > 0.05) in AUDPC among treatments and when compared to the non-inoculated and no-fungicide controls for Fof. The data indicates that these fungicides used alone are not effective against these pathogens in planta. A strawberry plant extract (germination stimulant) was assessed for its ability to stimulate germination of Mp microsclerotia in vitro and in planta. The germination stimulant was applied as a drench at six different concentrations (0, 10, 100, 1,000, 10,000 and 30,000 ppm) to soil containing filter disk packets of microsclerotia of Mp at day 0 and 14. Filter disk packets were retrieved three days after the drench and microsclerotia were observed microscopically for germination. Results showed that the number of germinating microsclerotia was significantly higher after the application of the germination stimulant compared to non-drench and 0 ppm controls (p < 0.001). An integrated container trial was also conducted using the germination stimulant at 10,000 ppm applied three days prior to a fungicide drench with tebuconazole or thiophanate-methyl to determine the effect of fungicides on the germinated microscleotia. The use of the germination stimulant with label rates of the fungicides lowered the number of germinated intact microsclerotia significantly (p < 0.001) especially after two drench applications. The use of the germination stimulant with fungicides could be investigated further as one method for controlling soilborne diseases of strawberry.

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Yusran. « Use of plant growth-promoting rhizobacteria (PGPR) to improve mycorrhization, nutrient acquisition and growth of vegetable plants affected by soilborne pathogens ». Göttingen Cuvillier, 2009. http://d-nb.info/997890959/04.

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Short, Nicolyn. « Implications of green manure amendments on soil seed bank dynamics ». University of Western Australia. School of Earth and Geographical Sciences, 2006. http://theses.library.uwa.edu.au/adt-WU2006.0022.

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[Truncated abstract] Weeds are a major limitation to agricultural and horticultural production and the main method of control is the use of herbicides. In addition to the resulting chemical pollution of the environment, the wide spread and continues use of herbicides have resulted in many weeds developing resistance to commonly used herbicides. This study investigated the potential of using green manures as a cultural method of control of weed invasion in agricultural fields. To understand the general mechanisms involved in the suppression of seed germination in green manure amended soils, seeds of crop species with little or no dormancy requirements were used in certain studies. Lettuce (Lactuca sativa) and cress (Lepidium sativum) seeds were sown to a sandy soil amended with green manures of lupin (Lupinus angustifolius), Brassica juncea, or oats (Avena sativa) to determine if the amendments affected seed germination and/or decay. It was hypothesised that the addition of plant material would increase the microbial activity of the soil thereby increasing seed decay, under laboratory and greenhouse conditions. Initial experiments used lettuce, cress and lupin seeds. Lettuce and cress are commonly used as standard test species for seed viability studies. Subsequent experiments used seeds of annual ryegrass (Lolium rigidum), silver grass (Vulpia bromoides), wild radish (Raphanus raphanistrum) and wild oat (Avena fatua) as these weed species are commonly found throughout agricultural regions in Western Australia. Amending the soil with lupin or Brassica green manure was established as treatments capable of developing environments suppressive to seed germination. Lupin residues as green manure showed the strongest inhibition of seed germination and seed decay. The decay of certain seeds was enhanced with changes to soil microbial activity, dissolved organic carbon and carbon and nitrogen amounts in lupin amended soil. Seeds of weed species were decayed in lupin amended soil, but showed varied degree of decay. Annual ryegrass and silver grass were severely decayed and wild oat and wild radish were less decayed, in lupin amended soil.

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Cummings, Jaime Anne. « Evaluation of seed and drench treatments for management of damping-off and seedling blight pathogens of spinach for organic production ». Online access for everyone, 2007. http://www.dissertations.wsu.edu/Thesis/Fall2007/j_cummings_112007.pdf.

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Cruz, Juliana Cristina Sodário 1975. « Preservação, caracterização patogênica e molecular de Plasmodiophora brassicae, agente causal da hérnia das crucíferas / ». Botucatu : [s.n.], 2007. http://hdl.handle.net/11449/105444.

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Orientador: Edson Luiz Furtado
Banca: Marli Teixeira de Almeida Minhoni
Banca: Romulo Fujito Kobori
Banca: Louise Larissa May de Mio
Banca: César Júnior Bueno
Resumo: A doença conhecida por hérnia das crucíferas é causada pelo patógeno Plasmodiophora brassicae Woronin, sendo uma das mais importantes e de difícil controle em brássicas. Em virtude da dificuldade de preservação das estruturas de resistência de P. brassicae em condições laboratoriais, por se tratar de um parasita obrigatório, foi desenvolvido um ensaio visando a obtenção de uma técnica eficiente e prática de preservação. Para isto, raízes de diferentes brássicas naturalmente infectadas por P. brassicae, contendo hérnias, foram coletadas de uma mesma propriedade (município de Pardinho - SP), em diferentes períodos, e imediatamente congeladas em freezer a -20°C±2°C. Os tratamentos foram: T1: hérnias congeladas por 389 dias, (rúcula); T2: hérnias congeladas por 242 dias (brócolis); T3: hérnias congeladas por 21 dias (couve-chinesa) e T4: testemunha (sem inóculo). Os testes de patogenicidade, após os diferentes períodos de armazenamento, foram realizados em condições controladas de casa de vegetação (25±2°C), onde em cada planta, de uma variedade suscetível de couve-chinesa (Pak choi), foi inoculado 2mL da suspensão de esporos, dos diferentes tratamentos, na concentração de 107 esporos.mL-1. Cada tratamento contou com seis repetições distribuídas ao acaso. Passadas cinco semanas, após a inoculação, as raízes foram lavadas e avaliadas. Houve diferença estatística significativa entre os materiais avaliados quanto aos diferentes períodos de armazenamento em "freezer". Os materiais congelados entre 21 a 242 dias preservaram suas características infectivas, sendo este método uma boa opção para a preservação das estruturas de repouso nesse período. Foram realizados testes de patogenicidade e análises moleculares de populações de P. brassicae, ...(Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Disease known as clubroot of crucifers is caused by the pathogen Plasmodiophora brassicae Woronin, and is one of the most important and difficult control crucifer diseases in brassicas. Because of the difficulty in preserving the resistance structures of P. brassicae under laboratory conditions, given that it is an obligate parasite, an assay was carried out to develop a practical and effective technique that would allow further studies to be conducted. On this proposal, roots of different brassica species naturally infected by P. brassicae showing clubroot symptoms were collected in the some grower (Pardinho, SP-city, Brazil) during different seasons, and were immediately frozen at approximately 20°C±2°C. The treatments were: T1: clubroots frozen for 389 days (arugula); T2: clubroots frozen for 242 days (broccoli); T3: clubroots frozen for 21 days (Chinese cabbage), and T4: control (no inoculum). The pathogenicity tests after different storage periods were conducted under controlled greenhouse conditions (25±2°C); each plant of a susceptible variety of Chinese cabbage was inoculated with 2mL of a spore suspension of the various treatments at a concentration of 107spores.mL-1. Each treatment consisted of six replicates distributed at random. The roots were washed and evaluated five weeks after inoculation. There were statistical differences between the materials evaluated with respect to different storage periods in the freezer. Materials kept frozen between 21 and 242 days retained their infective traits. Therefore, this method is a good option to preserve resting spores during this period. In addition, pathogenicity tests and molecular analyses were conducted with P. brassicae populations obtained from infected roots of several production regions of Brazil, on some...(Complete abstract click electronic access below)
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Van, Coller Gerhardus J. (Gerhardus Johannes). « An investigation of soilborne fungi associated with roots and crowns of nursery grapevines ». Thesis, Stellenbosch : Stellenbosch University, 2004. http://hdl.handle.net/10019.1/49844.

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Thesis (MScAgric)--University of Stellenbosch, 2004.
ENGLISH ABSTRACT: Soilborne diseases of grapevines represent a complex problem with limited information available, both locally and internationally. Previous research in South Africa indicated that Phytophthora and Pythium spp. were the most widespread and devastating pathogens in grapevine nurseries and vineyards in the Western Cape province. The local grapevine industry is currently expanding; new cultivars, methods and agricultural chemicals are being used which can affect soilborne pathogens. It has therefore become necessary to reassess the status of soilborne pathogens in nurseries, since information in this regard is crucial for the development of disease management practices for the expanding local grapevine industry. Soilborne fungal genera associated with roots and crowns of declining nursery grapevines were assessed in surveys conducted at three different grapevine nurseries in the Western Cape province. Cylindrocarpon, Fusarium, Pythium, and Rhizoctonia spp. were consistently isolated from roots and crowns of declining nursery grapevines. Cylindrocladiella spp. and Phytophthora cinnamomi were infrequently isolated from diseased roots, crowns and soil whereas Pythium spp. were abundant in most of the soils. Results suggest that the status of soilborne fungal pathogens in grapevine nurseries in the Western Cape province has changed over the last 30 years. The DNA phylogeny and pathogenicity of the isolates of Cylindrocladiella were determined. Four species of Cylindrocladiella occur on grapevines in South Africa, namely C. lageniformis, C. parva, C. peruviana, as well as a new species, described in this study as C. viticola, which forms part of the C. infestans species complex. Pathogenicity trials were inconclusive. Ten Fusarium spp. were isolated from roots and crowns of declining nursery grapevines, namely F. acuminatum, F. anthophilum, F. chlamydosporum, F. equiseti, F. nygamai, F. oxysporum, F. proliferatum, F. scirpi, F. semitectum and F. solani. The dominant species was F. oxysporum, followed by F. proliferatum and F. solani. In pathogenicity trials F. oxysporum and F. solani significantly reduced root volume, root dry mass, length of new shoots, stem diameter and number of leaves, but increased the percentage of chlorotic leaves and root rot severity. Fusarium proliferatum also caused a significant reduction in new shoot growth, number of leaves and increased root rot severity compared to the controls. Fusarium so/ani seems to be more virulent than F. oxysporum, followed by F. pro/iferatum. This is the first report of F. oxysporum, F. pro/iferatum and F. so/ani as pathogens of grapevines in South Africa, and the first report of F. proliferatum as a pathogen of grapevines in the world. Phytophthora cinnamomi was isolated at low frequencies from declined grapevines, although present in the rhizosphere soil. It is possible that the extensive use of downy mildew chemicals in grapevine nurseries may protect grapevines from infection by P. cinnamomi. The effect of chemicals used to combat downy mildew on Phytophthora root rot of nursery grapevines was evaluated in a glasshouse. There was very little discernable effect of the chemicals tested relative to the control plants for the parameters measured and it was concluded that the inoculation technique needed refinement. However, plants treated with phosphorous acid tended to be taller and have more leaves, greater stem diameter and root volume than controls or plants treated with the other chemicals. The data obtained in this study are not conclusive, but indicated certain trends that more glasshouse trials and field trials would resolve. Results presented in this thesis indicate that a major shift has occurred in the status of soilborne fungi associated with roots and crowns of grapevines in nurseries in the Western Cape since the 1970s when Phytophthora and Pythium were predominant. The prevalence and role of soilborne fungi need to be determined so that new appropriate disease management strategies can be developed to limit losses in grapevine nurseries and ensure the sustainable production of healthy plants for the grapevine industry.
AFRIKAANSE OPSOMMING: 'N ONDERSOEK NA GRONDGEDRAAGDE SWAMME GEASSOSIEER MET WORTELS EN KRONE VAN WINGERD IN KWEKERYE Grondgedraagde siektes van wingerd is 'n komplekse probleem waaroor min inligting, beide plaaslik en internasionaal, beskikbaar is. Vorige navorsing in Suid-Afrika het aangedui dat swamme van die genera Phytophthora en Pythium die mees algemene en vernietigende grondgedraagde patogene in kwekerye en wingerde in die Wes-Kaap provinsie is. Die plaaslike wingerdbedryf brei huidiglik uit; nuwe kultivars, metodes en landbouchemikalieë word gebruik wat 'n invloed kan hê op grondgedraagde patogene. Gevolglik het dit noodsaaklik geword om die status van grondgedraagde patogene in wingerdkwekerye weer te bepaal, aangesien inligting in hierdie verband noodsaaklik is vir die ontwikkeling van siekte bestuurspraktyke vir die ontwikkelende plaaslike wingerdbedryf. Grondgedraagde swamgenera geassosieer met wortels en krone van terugsterwende wingerd in kwekerye is bepaal in opnames wat by drie verskillende wingerdkwekerye in die Wes-Kaap provinsie uitgevoer is. Cylindrocarpon, Fusarium, Pythium, en Rhizoctonia spp. is konstant vanuit wortels en krone van terugsterwende wingerdplante in kwekery geïsoleer, Cylindrocladiella spp. en Phytophthora cinnamomi is ongereeld vanuit siek wortels, krone en grond geïsoleer, terwyl Pythium spp. algemeen in meeste gronde voorgekom het. Resultate dui daarop dat die status van grondgedraagde swampatogene in wingerdkwekerye in die Wes- Kaap provinsie oor die laaste 30 jaar verander het. Die DNA filogenie en patogenisiteit van die isolate van Cylindrocladiella is bepaal. Vier spesies van Cylindrocladiella kom voor op wingerd in Suid-Afrika, naamlik C. lageniformis, C. parva, C. peruviana, sowel as 'n nuwe spesie, wat in hierdie studie as C. viticola aangedui is en wat deel is van die C. infestans spesie kompleks. Patogenisiteits proewe was onvoldoende om die patogeniese status van die swam me te bepaal. Tien Fusarium spp. is vanuit wortels en krone van terugsterwende wingerdplante in kwekery geïsoleer, naamlik F. acuminatum, F. anthophilum, F. chlamydosporum, F. equiseti, F. nygamai, F. oxysporum, F. proliferatum, F. scirpi, F. semitectum en F. solani. Die dominante spesies was F. oxysporum, gevolg deur F. proliferatum en F. solani. In pathogenisteitsproewe het F. oxysporum en F. solani gelei tot 'n betekenisvolle laer wortelvolume, droë massa van wortels, lengte en droë massa van nuwe groei en aantal blare, maar het die persentasie chlorotiese blare en graad van wortelvrot verhoog. Fusarium proliferatum het ook gelei tot 'n betekenisvolle afname in lengte en massa van nuwe groei, aantal blare en 'n verhoogde graad van wortelvrot in vergelyking met die kontrole behandelings. Dit wil voorkom asof Fusarium solani meer virulent is as F. oxysporum, gevolg deur F. proliferatum. Hierdie is die eerste aanmelding van F. oxysporum, F. proliferatum en F. solani as patogene van wingerd in Suid-Afrika, en die eerste aanmelding van F. proliferatum as 'n patogeen van wingerd in die wêreld. Phytophthora cinnamomi is konstant teen lae frekwensies vanuit terugsterwende wingerd in kwekerye geïsoleer, alhoewel dit in risosfeer gronde teenwoordig was. Dit is moontlik dat die ekstensiewe gebruik van chemikalieë teen donsskimmel in wingerdkwekerye die wingerdplante kan beskerm teen infeksie deur P. cinnamomi. Die effek van chemikalieë wat gebruik word teen donsskimmel op Phytophthora wortelverrotting van wingerd in kwekerye, is 'n glashuis geëvalueer. Die chemikalieë wat gestoets is, het vir die gemete parameters, tot baie min onderskeibare effek gelei relatief tot die kontrole plante, en daar is afgelei dat die inokulasie tegniek verbetering benodig. Plante wat met fosforiensuur behandel is, het egter geneig om langer te wees met meer blare, 'n groter stamdeursnee en wortelvolume as kontrole plante of plante behandel met ander chemikalieë. Data verkry vanuit die hierdie studie was onvoldoende, maar sekere neigings is aangedui wat deur verdere glashuis- en veldproewe verklaar sal word. Resultate wat in hierdie tesis weergegee is, het aangedui dat 'n algehele verskuiwing in die status van grondgedraagde swamme geassosieer met wortels en krone van wingerd in kwekerye vanaf die 1970s, toe Phytophthora en Pythium die dominante genera was, plaasgevind het. Die voorkoms en rol van grondgedraagde swamme moet bepaal word, sodat nuwe voldoende siektebestuurspraktyke ontwikkel kan word om verliese in wingerdkwekerye te beperk en sodoende die volhoubare produksie van gesonde plante vir die wingerdbedryf te verseker.

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Tewoldemedhin, Yared Tesfai. « Characterisation of Rhizoctonia in cropping systems in the Western Cape Province ». Thesis, Stellenbosch : University of Stellenbosch, 2005. http://hdl.handle.net/10019.1/2269.

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Thesis (MScAgric (Plant Pathology))--University of Stellenbosch, 2005.
The genus Rhizoctonia includes important soilborne plant pathogens that can cause severe economic losses on a wide range of crops including cereal, canola, pasture and grain legume crops. Limited information is available on specific anastomosis groups (AGs), nuclear status, pathogenicity and cross-pathogenicity of Rhizoctonia isolates associated with each of these crops in the Western Cape province. Therefore, these aspects were investigated in this study, since information in this regard is crucial for the development of Rhizoctonia disease management practices.

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Sena, Kenton L. « TRACKING A TREE-KILLER : IMPROVING DETECTION AND CHARACTERIZING SPECIES DISTRIBUTION OF PHYTOPHTHORA CINNAMOMI IN APPALACHIAN FORESTS ». UKnowledge, 2018. https://uknowledge.uky.edu/pss_etds/102.

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Phytophthora cinnamomi is a soil-borne oomycete pathogen causing root rot in susceptible host species. P. cinnamomi is thought to have originated in Southeast Asia, but has since been introduced to many regions around the world, where it causes dramatic declines in many forest tree species. In the eastern US, the primary susceptible tree species of concern are American chestnut (Castanea dentata), white oak (Quercus alba), and shortleaf pine (Pinus echinata). American chestnut, functionally eliminated in the early 1900s by the rapidly acting chestnut blight (Cryphonectria parasitica), has been the subject of decades-long breeding efforts aimed at improving chestnut resistance to chestnut blight. To improve chestnut restoration success, and restoration of other susceptible species, the distribution patterns of P. cinnamomi on a landscape scale must be better understood. This project was initiated to develop an improved method for detecting P. cinnamomi to permit high-throughput screening of forest soils, and to implement the improved detection approach in characterizing the distribution patterns of P. cinnamomi in developing soils on reclaimed surface mines in eastern Kentucky, as well as mature forest soils within an undisturbed watershed in a reference-quality eastern Kentucky forest. We developed an improved detection method using a molecular DNA-amplification approach (PCR), which demonstrated similar sensitivity to traditional culture-based methods, but required less time and space than traditional methods. We used this detection approach to screen soils from a chronosequence of reclaimed surface mines (reclaimed at different points in time) to evaluate whether reclaimed surface mined sites become favorable for P. cinnamomi colonization over time. Our analysis detected P. cinnamomi at the two older sites (reclaimed in 1997 and 2003), but we did not detect P. cinnamomi at the two newer sites sampled (reclaimed in 2005 and 2007). These results suggest that surface mined sites become favorable for P. cinnamomi colonization over time, and should not be considered permanently “Phytophthora-free.” We also collected ~200 samples from a watershed in UK’s Robinson Forest, from plots representing a gradient of topographic position, slope, and aspect. This survey indicated that P. cinnamomi distribution in forests is complex and can be difficult to predict; however, P. cinnamomi was detected in both drier upslope sites and in moister drainage sites.

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Fortes, Nara Lúcia Perondi [UNESP]. « Efeito da incorporação do lodo de esgoto sobre a fusariose do milho ». Universidade Estadual Paulista (UNESP), 2004. http://hdl.handle.net/11449/105427.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Universidade Estadual Paulista (UNESP)
O trabalho objetivou verificar os fatores químicos e microbiológicos do lodo de esgoto e do solo responsáveis pela incidência da podridão do colmo do milho, causada por Fusarium em solo fertilizado com lodo, e foi desenvolvido em condições de campo, numa área que vem sendo tratada com lodo e cultivada com milho desde 1999 em latossolo vermelho distróférrico (textura argilosa), localizada no município de Jaguariúna/SP. Os dois lodos utilizados foram obtidos nas Estações de Tratamento de Esgoto de Franca e de Barueri/SP. Os lodos foram incorporados ao solo nas concentrações de 0, 1, 2, 4 e 8 vezes a dose recomendada com base no teor de nitrogênio, em dois cultivos sucessivos de milho (Savana 133S) nas safras 2001/2002 e 2002/2003, em parcelas de 200 m2. As doses de lodo foram comparadas com a adubação mineral recomendada para a cultura do milho. Os tratamentos foram distribuídos em delineamento experimental casualizado em blocos e com três repetições. Foram verificadas, nas safras de 2001/2002 e 2002/2003, diferenças significativas entre as doses de lodo de esgoto, sobre a variação de Fusarium spp. no solo, na rizosfera, na raiz, no colmo e na semente, bem como sobre a incidência de plantas com podridão no colmo e nas espigas. As análises de regressão mostraram que a porcentagem de plantas doentes foi positivamente correlacionada com a concentração dos lodos incorporados ao solo. Os coeficientes de determinação para o cultivo de 2001/2002 foram de R2=0,61 e R2=0,32, enquanto para o cultivo de 2002/2003 foram de R2=0,76 e R2=0,45, para os lodos de Franca e Barueri, respectivamente. As concentrações de lodos também apresentaram correlação positiva com a comunidade de Fusarium do solo e da rizosfera e com a incidência de Fusarium na raiz, no colmo e na semente. As correlações entre a comunidade de Fusarium do solo e da rizosfera e o percentual de plantas... .
This work aimed at verifying the chemical and microbiological sewage sludge and soil factors re 0sponsible for the incidence of the corn stalk rot caused by Fusarium in soil fertilized with sludge and has been developed in field conditions, in an area that has been treated with sludge and cultivated with corn since 1999, in red dystroferric latosol (clayey texture), in Jaguariúna/SP. Both sludges used were obtained in the sewage sludge treatment stations of Franca and Barueri/SP. Sludges were incorporated into the soil in concentrations of 0, 1, 2, 4 and 8 times in relation to the recommended rate based on the nitrogen contents, in two successive corn cultures (Savana 133S), in 2001/2002 and 2002/2003, in plots of 200 m2. Sludge doses were compared to the mineral fertilization recommended to the corn culture. The treatments were distributed in a randomized design experimental drawing in blocks and with three repetitions. Significant differences were verified in both 2001/2002 and the 2002/2003 crops among the sewage sludge doses about the variation of Fusarium spp. in soil, root, stalk and seed, as well as about the incidence of plants with stalk and corn rot. The regression analyses have showed that the percentage of diseased plants was positively correlated to the concentration of the sludges incorporated to the soil. The determination coefficients to the 2001/2002 culture were R2=0.61 and R2=0.32, while the 2001/2003 culture showed R2=0.76 and R2=0.45, to Franca and Barueri sludges, respectively. The sludges concentrations also presented positive correlation with the Fusarium community of the soil and the rhizosphere, and with the incidence of Fusarium in the root, stalk and seed. The correlations between the Fusarium community of the soil and rhizosphere and the percentage of diseased plants with chemical soil attributes were significant and positive, for both kinds of sludges, in the level of 1 and 5%, to phosphorus and calcium contents.

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Fortes, Nara Lúcia Perondi. « Efeito da incorporação do lodo de esgoto sobre a fusariose do milho / ». Botucatu : [s.n.], 2004. http://hdl.handle.net/11449/105427.

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Orientador : Raquel Ghini
Banca: Raquel Ghini
Banca: Wagner Bettiol
Banca: Nilton Luiz de Souza
Banca: Idalmir dos Santos
Banca: Gisela Maria Fantin
Resumo: O trabalho objetivou verificar os fatores químicos e microbiológicos do lodo de esgoto e do solo responsáveis pela incidência da podridão do colmo do milho, causada por Fusarium em solo fertilizado com lodo, e foi desenvolvido em condições de campo, numa área que vem sendo tratada com lodo e cultivada com milho desde 1999 em latossolo vermelho distróférrico (textura argilosa), localizada no município de Jaguariúna/SP. Os dois lodos utilizados foram obtidos nas Estações de Tratamento de Esgoto de Franca e de Barueri/SP. Os lodos foram incorporados ao solo nas concentrações de 0, 1, 2, 4 e 8 vezes a dose recomendada com base no teor de nitrogênio, em dois cultivos sucessivos de milho (Savana 133S) nas safras 2001/2002 e 2002/2003, em parcelas de 200 m2. As doses de lodo foram comparadas com a adubação mineral recomendada para a cultura do milho. Os tratamentos foram distribuídos em delineamento experimental casualizado em blocos e com três repetições. Foram verificadas, nas safras de 2001/2002 e 2002/2003, diferenças significativas entre as doses de lodo de esgoto, sobre a variação de Fusarium spp. no solo, na rizosfera, na raiz, no colmo e na semente, bem como sobre a incidência de plantas com podridão no colmo e nas espigas. As análises de regressão mostraram que a porcentagem de plantas doentes foi positivamente correlacionada com a concentração dos lodos incorporados ao solo. Os coeficientes de determinação para o cultivo de 2001/2002 foram de R2=0,61 e R2=0,32, enquanto para o cultivo de 2002/2003 foram de R2=0,76 e R2=0,45, para os lodos de Franca e Barueri, respectivamente. As concentrações de lodos também apresentaram correlação positiva com a comunidade de Fusarium do solo e da rizosfera e com a incidência de Fusarium na raiz, no colmo e na semente. As correlações entre a comunidade de Fusarium do solo e da rizosfera e o percentual de plantas... (Resumo completo, clicar acesso eletrônico abaixo).
Abstract: This work aimed at verifying the chemical and microbiological sewage sludge and soil factors re 0sponsible for the incidence of the corn stalk rot caused by Fusarium in soil fertilized with sludge and has been developed in field conditions, in an area that has been treated with sludge and cultivated with corn since 1999, in red dystroferric latosol (clayey texture), in Jaguariúna/SP. Both sludges used were obtained in the sewage sludge treatment stations of Franca and Barueri/SP. Sludges were incorporated into the soil in concentrations of 0, 1, 2, 4 and 8 times in relation to the recommended rate based on the nitrogen contents, in two successive corn cultures (Savana 133S), in 2001/2002 and 2002/2003, in plots of 200 m2. Sludge doses were compared to the mineral fertilization recommended to the corn culture. The treatments were distributed in a randomized design experimental drawing in blocks and with three repetitions. Significant differences were verified in both 2001/2002 and the 2002/2003 crops among the sewage sludge doses about the variation of Fusarium spp. in soil, root, stalk and seed, as well as about the incidence of plants with stalk and corn rot. The regression analyses have showed that the percentage of diseased plants was positively correlated to the concentration of the sludges incorporated to the soil. The determination coefficients to the 2001/2002 culture were R2=0.61 and R2=0.32, while the 2001/2003 culture showed R2=0.76 and R2=0.45, to Franca and Barueri sludges, respectively. The sludges concentrations also presented positive correlation with the Fusarium community of the soil and the rhizosphere, and with the incidence of Fusarium in the root, stalk and seed. The correlations between the Fusarium community of the soil and rhizosphere and the percentage of diseased plants with chemical soil attributes were significant and positive, for both kinds of sludges, in the level of 1 and 5%, to phosphorus and calcium contents.
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Pinto, Zayame Vegette [UNESP]. « Desenvolvimento de substrato supressivo à murcha do crisântemo causada por Fusarium oxysporum ». Universidade Estadual Paulista (UNESP), 2009. http://hdl.handle.net/11449/105478.

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Made available in DSpace on 2014-06-11T19:35:01Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-12-16Bitstream added on 2014-06-13T19:44:47Z : No. of bitstreams: 1 pinto_zv_dr_botfca.pdf: 894968 bytes, checksum: 522dc825bbc64c7631c86fa63430a259 (MD5)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
A murcha de Fusarium spp. em crisântemo é responsável por sérios prejuízos à cultura no Brasil. Uma alternativa para o seu controle é o uso de substrato supressivo, o qual pode ser obtido pela adição de fontes de matérias orgânicas. Dessa forma, o presente trabalho teve por objetivo desenvolver um substrato supressivo à murcha do Fusarium em crisântemo com a introdução de matéria orgânica em substratos comerciais. Para tanto, lodo de esgoto e lodo de esgoto compostado; torta de mamona; esterco suíno; cama aviária; compostos comerciais Lanzi®; casca de camarão, biofertilizante e hidrolisado de peixe foram incorporados a substratos à base de casca de Pinus e de turfa em diferentes concentrações e combinações. Os experimentos foram realizados em propriedade produtora de crisântemo Bola-belga com problemas de Fusarium. Em todos os experimentos o número mínimo de repetições foi de 20 vasos por tratamento. Transcorridas 8, 12, 15 e 20 semanas do transplantio foi avaliada a severidade da doença por uma escala de notas de 0 para planta sadia a 5 para planta morta. Com os dados foram calculadas as áreas abaixo da curva de progresso da severidade da murcha de Fusarium. Além disso, foram realizadas análises dos atributos químicos e da atividade microbiana dos substratos bem como do desenvolvimento das plantas. O lodo de esgoto, lodo de esgoto compostado, cama aviária, casca de camarão e o composto Lanzi® induziram a supressividade do substrato à base de casca se Pinus e/ou de turfa, controlando a murcha de Fusarium. Por outro lado, esterco suíno, torta de mamona, hidrolisado de peixe, quitosana e Trichoderma asperellum não interferiram na supressividade à doença. Substratos obtidos com lodo de esgoto e cama aviária, em mistura ou não, nas concentrações de 10, 20 e 30% (v/v) foram os mais adequados do ponto de vista de indução de supressividade...
Fusarium spp. wilt causes serious damages to chrysanthemum crops in Brazil. An alternative for its control is the use of suppressive plant growth media, which can be obtained by the addition of organic matter to container media. The objective of the present work was to develop a plant growth media suppressive to the Fusarium spp. in chrysanthemum with the introduction of organic matter to commercial container media. Sewage sludge and sewage sludge compost; castorbean presscake, swine manure; poultry litter; shrimp peel, biofertilizer, chitosan and fish hydrolyzed were incorporated to pine-bark and turf container media in different concentrations and combinations. The experiments were conducted in a Belgianchrysanthemum variety producing property with a Fusarium problem. In all experiments the minimum number of repetitions was 20 containers per treatment. Eight, 12, 15 and 20 weeks following transplanting the severity of the disease was evaluated according to a progressive scale from 0 (healthy plant) to 5 (dead plant). Areas under the disease progress curve for disease severity of Fusarium wilt were calculated. Chemical and microbiological attributes of container media and plant development were analyzed. The sewage sludge, sewage sludge compost, poultry litter, shrimp peel and the Lanzi® compost induced the suppressiveness of pine bark and/or turf container media, controlling the wilt. On the other hand, swine manure, castorbean presscake, fish hydrolyzed, chitosan and Trichoderma asperellum did not affect the suppressiveness to the disease. Plant growth media with sewage sludge and poultry litter, in mixture or alone, in the concentrations of 10, 20 and 30% (v/v) were the most appropriate from the point of view of induction of suppressiveness and product quality, being the plant growth media recommended... (Complete abstract click electronic access below)

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Mgcoyi, Bulelani William. « Quality assessment of agricultural water used for fertigation in the Boland district ». Thesis, [Bloemfontein?] : Central University of Technology, Free State, 2011. http://hdl.handle.net/11462/174.

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Thesis (M. Tech. (Agriculture)) -- Central University of Technology, Free state, 2011
Quality assessment of agricultural water used for fertigation in the Boland district. The study was undertaken to determine the influence of seasonal changes on the water quality (chemical and microbial analyses) of five different rivers in the Boland. The data was collected in the five most important water sources that are used for irrigation purposes in the district, i.e. Berg river, Eerste river, Klapmuts River, Klippies river and Krom river. The samples were collected from all sites once every three weeks for a period of six months. The sampling was carried out during specific periods in summer (December, 2006 to February, 2007) and winter (June to August, 2007). The results of the study showed that Klapmuts river recorded the highest levels of chloride and iron, especially in summer. However, chloride levels were far below the levels set by the Department of Water Affairs and Forestry. Results obtained from this study show the presence of pathogens in some of the rivers assessed which may have resulted from the leaching of these pathogens from nearby agricultural land, livestock watering or informal settlements in the catchment areas. The bigger rivers recorded low levels of micro-elements and this might have been affected by winter rainfall. In the Berg River, many sources of nitrate pollution seem to be present in the catchment area. The levels of iron in all the rivers assessed were far more than the levels set by the Department of Water Affairs and Forestry in all rivers assessed and these might be due to the pH levels and interaction between the rivers and seasons. Iron and manganese levels should be kept low as this may cause production problems by blocking irrigation drippers. The water samples tested for bacterial and fungal density showed Klapmuts and Eerste rivers were positive for Phytophthora cinnamomi during winter. Phytophthora citricola and Phytophthora cactorum were detected in the Klapmuts and Klippies rivers in summer. The Berg-, Klapmuts-, Krom- and Eerste rivers tested positive for species of the genera Pythium and Fusarium. Similar organisms were detected in the Eerste river mainly during summer on the fourth sampling date, while Krom river only tested positive for Pythium during summer. The total bacterial and algal density differed significantly between the seasons and was highest in winter. This might be due to high rain water influx and efflux and/or moist and aerobic conditions and air temperature. There is an increased need for farmers to sterilize feeding water (chlorination) due to high microbial count.

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Pinto, Zayame Vegette 1977. « Desenvolvimento de substrato supressivo à murcha do crisântemo causada por Fusarium oxysporum / ». Botucatu : [s.n.], 2008. http://hdl.handle.net/11449/105478.

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Orientador: Wagner Bettiol
Banca: Edson Luiz Furtado
Banca: Marcelo Augusto Boechat Morandi
Banca : Nelson Sdney Massola Júnior
Banca: Flávia Rodrigues Alves Patrício
Resumo: A murcha de Fusarium spp. em crisântemo é responsável por sérios prejuízos à cultura no Brasil. Uma alternativa para o seu controle é o uso de substrato supressivo, o qual pode ser obtido pela adição de fontes de matérias orgânicas. Dessa forma, o presente trabalho teve por objetivo desenvolver um substrato supressivo à murcha do Fusarium em crisântemo com a introdução de matéria orgânica em substratos comerciais. Para tanto, lodo de esgoto e lodo de esgoto compostado; torta de mamona; esterco suíno; cama aviária; compostos comerciais Lanzi®; casca de camarão, biofertilizante e hidrolisado de peixe foram incorporados a substratos à base de casca de Pinus e de turfa em diferentes concentrações e combinações. Os experimentos foram realizados em propriedade produtora de crisântemo Bola-belga com problemas de Fusarium. Em todos os experimentos o número mínimo de repetições foi de 20 vasos por tratamento. Transcorridas 8, 12, 15 e 20 semanas do transplantio foi avaliada a severidade da doença por uma escala de notas de 0 para planta sadia a 5 para planta morta. Com os dados foram calculadas as áreas abaixo da curva de progresso da severidade da murcha de Fusarium. Além disso, foram realizadas análises dos atributos químicos e da atividade microbiana dos substratos bem como do desenvolvimento das plantas. O lodo de esgoto, lodo de esgoto compostado, cama aviária, casca de camarão e o composto Lanzi® induziram a supressividade do substrato à base de casca se Pinus e/ou de turfa, controlando a murcha de Fusarium. Por outro lado, esterco suíno, torta de mamona, hidrolisado de peixe, quitosana e Trichoderma asperellum não interferiram na supressividade à doença. Substratos obtidos com lodo de esgoto e cama aviária, em mistura ou não, nas concentrações de 10, 20 e 30% (v/v) foram os mais adequados do ponto de vista de indução de supressividade... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Fusarium spp. wilt causes serious damages to chrysanthemum crops in Brazil. An alternative for its control is the use of suppressive plant growth media, which can be obtained by the addition of organic matter to container media. The objective of the present work was to develop a plant growth media suppressive to the Fusarium spp. in chrysanthemum with the introduction of organic matter to commercial container media. Sewage sludge and sewage sludge compost; castorbean presscake, swine manure; poultry litter; shrimp peel, biofertilizer, chitosan and fish hydrolyzed were incorporated to pine-bark and turf container media in different concentrations and combinations. The experiments were conducted in a Belgianchrysanthemum variety producing property with a Fusarium problem. In all experiments the minimum number of repetitions was 20 containers per treatment. Eight, 12, 15 and 20 weeks following transplanting the severity of the disease was evaluated according to a progressive scale from 0 (healthy plant) to 5 (dead plant). Areas under the disease progress curve for disease severity of Fusarium wilt were calculated. Chemical and microbiological attributes of container media and plant development were analyzed. The sewage sludge, sewage sludge compost, poultry litter, shrimp peel and the Lanzi® compost induced the suppressiveness of pine bark and/or turf container media, controlling the wilt. On the other hand, swine manure, castorbean presscake, fish hydrolyzed, chitosan and Trichoderma asperellum did not affect the suppressiveness to the disease. Plant growth media with sewage sludge and poultry litter, in mixture or alone, in the concentrations of 10, 20 and 30% (v/v) were the most appropriate from the point of view of induction of suppressiveness and product quality, being the plant growth media recommended... (Complete abstract click electronic access below)
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MIGLIORINI, DUCCIO, PAOLO CAPRETTI et ALBERTO SANTINI. « Phytophthora in natural and anthropic environments : new molecular diagnostic tools for early detection and ecological studies ». Doctoral thesis, 2016. http://hdl.handle.net/2158/1028950.

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L’efficacia di PCR quantitativa basata su una sonda TaqMan specifica per il genere è stata confermata come preciso strumento di rilevamento di DNA di Phytophthora su suolo artificialmente infettato, in suolo di invasatura contaminato proveniente da vivaio ed in campioni di trappole aeree. Nessuna quantificazione di DNA è avvenuta dopo due settimane dalla morte indotta del patogeno e, in confronto con i metodi di isolamento tradizionali, è stata dimostrata una significativa maggiore efficienza come strumento diagnostico. La fluttuazione stagionale di Phytophthora in aria è stata quantificata e descritta per il periodo di campionamento. La tecnica di sequenziamento 454 è stata utilizzata per identificare la tassonomia delle specie di Phytophthora in un hotspot biologico in Western Australia ed al fine di descrivere la patogenicità delle due specie sequenziate con maggior frequenza è stato realizzato un esperimento in serra. Le tecniche di laboratorio utilizzate in questo studio hanno fornito nuove nozioni sull’ecologia di Phytophthora. La PCR quantitativa basata su sonda TaqMan è testata e proposta come efficace strumento di prevenzione verso l’arrivo di specie invasive. Importanza dell’impatto di questo studio L’efficienza della gestione di Phytophthora dipende dalla conoscenza delle caratteristiche patogene di gruppi ristretti di specie o di una singola specie . Ricerche come queste forniscono le basi scientifiche per comprendere l’epidemiologia di una malattia ed applicare un controllo risolutivo. A quantitative PCR technique based on a genus specific TaqMan probe was confirmed as a precise method for detecting Phytophthora DNA in artificially infested soil under laboratory condition, in naturally infested soil and tissues of potted nursery plants and in the filters of air traps. No positive DNA quantification occurred in soil after two weeks from pathogen induced death and a significant higher efficiency as diagnostic tool was demonstrated compared to traditional isolation methods both in soil and plant tissues. Seasonal fluctuation of aerial spread of Phytophthora was also quantified and described. A 454 sequencing approach was used to identify the Phytophthora species present in a biological hotspot area in Western Australia, and a glass house experiment was performed in order to describe the pathogenicity traits of the two most frequently detected species. The lab procedures used in this study provided a more precise knowledge of Phytophthora ecology. The quantitative PCR assay based on designed TaqMan probe was demonstrated to be very efficient and is proposed as a reliable early detection instrument of prevention against the income of invasive species. Efficient management of Phytophthora depends to the knowledge of pathogenicity traits in restrict groups or single species. Investigations like those presented in this thesis contribute the scientific bases to understand the epidemiology of disease and to apply a successful control.

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Hsu, Chiao-Fang, et 徐巧芳. « Study on actinomycetes antagonistic to soilborne pathogens ». Thesis, 2015. http://ndltd.ncl.edu.tw/handle/55478637549122896973.

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碩士
國立中興大學
土壤環境科學系所
103
The warm and humid climate as well as inappropriate soil fertilizer management result in outbreaks of plant disease in Taiwan, especially caused by soil-born plant pathogen. The were 177 strains of actinomycetes were isolated from four soils and one compost in Taiwan. Four isolates, A47, A177, A186 and A297, were selected for further studies based on their exceptional ability to inhibit Fusarium oxysporum f. sp. lycopersici and Rhizoctonia solani growth by dual culture test. Furthermore, the selected isolations were tested the antifungal activities against sclerotium rolfsii and Phytophthora capsici by the dual culture test. At least two of these plant fungal pathogens were inhibited by the selected isolates, and their antifungal index were all > 40%. Both A177 and A297 inhibited all the tested soil-born plant fungal pathogens with varying efficiencies. The production of extracellular enzymes, including chitinase, cellulose, gelatinase, protease and lipase and amylase by these isolates were analyzed. The production of plant growth regulator including indole-3- acetic acid and siderophore were also evaluated. A47, A177 and A297 showed the greatest in production of the extracellular enzymes and plant growth regulator. These isolates were used to determine their antagonistic ability to Fusarium oxysporum f. sp. lycopersici on potato dextrose agar plates with different pH values. The antifungal activities of A177, A186 and A297 were not significantly different as pH ranged from 4.5 to 9.5. The antifungal activities of A47 increased with increasing pH. A47, A177, A186 and A297 were taxonomically closed to Lentzea waywayandensis, Streptomyces sp., Amycolatopsis circi, and Streptomyces sp. repectively based on 16S rDNA sequences.The spore suspensions of A297 inhibited egg hatching rate of southern root-knot nematode, and increased the juvenile mortality. The hatching rate were 8%, and juveniles mortality rate were 30%. Although the spore suspension of A47 and A297 didn’t show inhibition efficacy to juveniles, they decrease the ability of juveniles to infect water spinach by 16.3%. The pre-treatment of spore suspension of A297 reduced the population density of Fusarium oxysporum f. sp. lycopersici and disease severity (biocontrol efficacy 87%). Application of spore suspension of A47 and A177 didn’t reduce the population of Fusarium oxysporum f. sp. lycopersici, but the disease severity was significantly reduced (biocontrol efficacy 100%). A47 and A177 may induce systemic resistance in tomato against Fusarium oxysporum f. sp. lycopersici. The culture filtrate of A297 treated with proteinase K and boiled. This indicated that A297 produced not only chitinase but also thermostable antifungal compound(s). A47, A177 and A297 could be developed as biocontrol agents for controlling tomato Fusarium wilt. Of them A47 and A297 could also be developed as biocontrol agents of southern root-knot nematode.

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Reimann, Stephan [Verfasser]. « The interrelationships between rhizobacteria and arbuscular mycorrhizal fungi and their importance in the integrated management of nematodes and soilborne plant pathogens / von Stephan Reimann ». 2005. http://d-nb.info/975356615/34.

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Fernando, W. Gerard Dilantha. « Biology, epidemiology, and biological and chemical control of Phytophthora vignae ». Thesis, 1990. http://hdl.handle.net/1957/37166.

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Phytophthora vignae, causal agent of stem and root rot of cowpea (Vigna unguiculata), was reported for the first time in Sri Lanka. The pathogen was found in cowpea field soils from 3 of 5 geographic regions sampled. Only one site however, had plants exhibiting disease symptoms. Of the eight cowpea varieties grown in Sri Lanka, four were shown to be relatively resistant; all other legumes inoculated were completely resistant. Two morphologic and physiologic races of P. vignae were identified among the 24 isolates recovered, based on differential pathogenicity on cowpea varieties. Bacteria isolated from field soils, and other known bacterial biocontrol agents, inhibited P. vignae in culture, but only three Sri Lankan isolates considerably suppressed the disease in greenhouse tests. Volatile substances produced by most bacteria inhibited mycelial growth and sporangial production by P. vignae. The increased pH of the exposed medium suggested the involvement of ammonia. Volatile inhibitors were produced by these bacteria in soil, but only with added substrate; Strain DF-3101 also reduced oospore germination in soil. Cowpea plants inoculated with the VA mycorrhizal (VAM) fungus Glomus intraradices in P. vignae-infested soil were larger than non-mycorrhizal plants, but only at low levels of the pathogen. VAM colonization was reduced at high levels of the pathogen, and root infection by the pathogen was reduced by VAM. The fungicides metalaxyl, fosetyl-Al, Banrot, and Manzate-200DF reduced in vitro mycelial growth, but at different concentrations. Sporangia formation and germination, and oogonia formation by P. vignae, was reduced significantly by metalaxyl and fosetyl-Al. In greenhouse tests, metalaxyl, even at low concentrations, reduced disease; Fosetyl-Al was effective at high concentrations; Manzate-200DF was effective as a soil drench but not as a foliar spray; Banrot effectively reduced disease at 50 mg a.i./L. Exposure of a bacterial biocontrol agent to these fungicides in vitro did not affect its capacity to subsequently produce volatile inhibitors, but exposure to 10 ug/ml of metalaxyl and 50 ug/ml of Manzate-200DF reduced its capacity to subsequently inhibit mycelial growth of P. vignae.
Graduation date: 1991

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Abraham, Abraha Okbasillasie. « Biological control of Phytophthora root rot of citrus seedlings and cuttings ». Thesis, 2005. http://hdl.handle.net/10413/3830.

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With an increasing realization that many agrochemicals are hazardous to animals and humans, came the desire to replace these chemical agents with biological approaches that are more friendly to the environment and human health. Microorganisms play an important role in plant disease control, as naturally occurring antagonists. Microorganisms may also have beneficial effects on plant development when applied to plant roots. Research efforts worldwide have recorded successes in biological control and growth stimulation on many crops, particularly when using members of the genera Bacillus and Trichoderma. Their use on citrus rootstock could be advantageous to nurserymen and growers in reducing the incidence of seedling mortality and increasing production. To achieve these objectives, laboratory and tunnel experiments were conducted to develop effective biocontrol agents for citrus seedlings and cuttings. Nineteen 0 ut 0 f 23 Trichoderma isolates tested in vitro against Phytophthora p arasitica sp showed antagonistic activity by hyperparasitism and four out of eight Bacillus isolates resulted in antagonism by forming inhibition zones. The positive in vitro activity of Trichoderma and Bacillus isolates on Phytophthora provided motivation step for further trials in the greenhouse to evaluate their biological control activity on citrus seedlings and cuttings. A greenhouse trial was carried out to evaluate the biological control potential of 23 Trichoderma isolates (drenched at 5 x 105 spores / rnI) and two Bacillus isolates (drenched at 1 X 106 or 1 X 108 colony forming units (CFU) / rnI) to suppress Phytophthora parasitica sp. of rough lemon (Citrus jambhirini Lush.) seedlings. Five isolates ofTrichoderma (AA12, AA5, Trichoderma harzianum (AA16), SY3F and Eco-T~ were highly effective in suppressing Phytophthora root rot, with AA12 providing the best control. The Bacillus isolates also suppressed the pathogen but were not as effective as the Trichoderma isolates. This trial was used to test for growth stimulation activity by some of the biocontrol agents. To verify these results, a further trial was carried out to evaluate growth stimulation capabilities in the absence of any pathogen. Trichoderma Isolates AA13 and AA17 caused no 111 change in seedling growth, while other Trichoderma and Bacillus isolates had an inhibitory effect on the seedling growth. This trial indicated that the biocontrol activity was affected by inoculum densities, and as a result in vitro sporulation capacity was evaluated. TrichodermaIsolate AA16 was the largest spore producer, followed by Eco-T®. Spore production was lowest from Trichoderma isolates AA4 and AA12. Growth stimulation responses of Trichoderma Isolates AA4, AA16, Eco-TID and SYN6 were further studied at four different doses (1 X 103, 1 X 104, 5 X 105 or 1 X 106 spores / ml) on rough lemon and trifoliate orange seedlings. Trifoliate oranges responded positively to 1 X 104 and 5 X 105 spores / ml of Eco-TID, but rough lemon responded negatively to all dosages of the Trichoderma isolates applied. This indicates that the inoculum density responses may be host specific. Higher population density of 1 X 106 spores / ml of all tested Trichoderma isolates had a stunting effect on seedling growth of both species. Based on t he positive results 0 f individual applications of some Trichoderma and Bacillus isolates, of the biological control agents on rough lemon seedlings against Phytophthora parasitica in an earlier greenhouse trial, their combined effect in the control of the pathogen was performed. Before carrying out a greenhouse trial, activities of the isolates to be combined were evaluated in vitro. This trial showed that Trichoderma Isolates AA16 and Eco-T®were compatible. Trichoderma isolates AA16 and Eco-T®were also found to be compatible with Bacillus Isolates B77, B81 and PHP. As a result, further in vivo trials were conducted. The tunnel trials were carried out as two separate experiments: In the first experiment, a combination of two Trichoderma Isolates A A 16 and Eco-T®was conducted assayed at 5 X 105 or 1 X 106 spores / ml, on rough lemon seedling, and cuttings and trifoliate orange and sour orange seedlings. A combination of Trichoderma isolate AA16 and Eco-T®at 5 X 105 spore / ml increased significantly the new flush biomass of rough lemon cuttings compared to AA16 alone, but was not different from Eco-TID alone. The combination of AA16 and Eco-T® achieved no change of biomass of rough lemon and trifoliate orange seedlings. The combination of AA16 and Eco-TID did not increase the root biomass of sour orange compared to AA16 or Eco-r® alone. The combination of AA16 and Eco-r® at higher doses (1 x 106 spores / ml) showed significantly better suppression of Phytophthora root rot of rough lemon cuttings but did not show disease suppression in all seedling species verities tested. In a second experiment, individual and combined effects of Trichoderma isolates (drenched at 5 X 105 spores / ml) with Bacillus isolate (drenched at 1 X 106 colony forming units (CFU) / ml) for suppression of Phytophthora root rot on rough lemon and trifoliate orange seedlings was performed. The combination of Trichoderma Isolate AA16 and Bacillus Isolate B81 increased root biomass on rough lemon seedlings compared to the combination of Trichoderma AAI6 or Bacillus PHP but was not significantly different to Trichoderma AA16 alone. Bacillus PHP combined with Trichoderma AA16 or singly had no effect on rough lemon seedlings. Combining Trichoderma Eco--r® and with Bacillus B8I or PHP did not increase biomass of rough lemon seedlings compared to Trichoderma Isolate Eco--r® alone. There was no statistically significant differences in the effects of the combinations of the Trichoderma and Bacillus isolates compared to their individual applications on the biomass of trifoliate oranges. This study established the antagonistic potential of several South African isolates of Trichoderma and Bacillus as a viable alternative to agrochemicals for controlling Phytophthora parasitica. The growth stimulation capabilities of Trichoderma isolates in terms of seedling development was also demonstrated.
Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2005.

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Kubheka, Bongani Petros. « In vitro and in vivo screening of Bacillus spp. for biological control of Rhizoctonia solani ». Thesis, 2003. http://hdl.handle.net/10413/5501.

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The increasing concerns about chemical pesticides that are environmentally hazardous and the continuous development of resistance by palhogens to chemical pesticides have led to this study. Many studies have shown that some Gram-negative bacteria, such as Pseudomonas flouresens, control plant diseases and promote plant growth. In this study Gram positive bacteria, Bacillus sp., were chosen because of their ability to produce endospores. Endospores can be used in stable, dry formulations. The advantage of using endospores is their ability to survive harsh conditions such as droughts and high temperatures, which give a long shelf life to the biological control agent. Bacillus isolates were recovered from the rhizosphere of 12 different crops, and were subsequently screened in vitro for their antimicrobial activity. Of 130 isolates, 87 exhibited antimicrobial activity against the test organisms: Rhizoctonia solani, Pythium sp., Phytophthora cinnamoni, Fusarium sp., and single representatives of Gram negative and Gram positive bacteria, namely, Erwinia carotovora and Staphylococcus aureus respectively. The Bacillus isolates B77, B81 and B69 inhibited all the test organisms investigated, which suggests that they produced broad spectrum antimicrobial compounds or more than one antimicrobial compound. Of the isolates that showed antimicrobial activity, 78 of them did not inhibit Trichoderma harzianum K D, which is a registered biological control agent; indicating their potential for combined application. Selected Bacillus isolates were tested for the biological control of R. solani under greenhouse conditions in wheat, cabbage, tomato, maize, and cucumber seedlings. Bacillus isolates were applied as seed treatments, and the inoculated seeds were planted in R. solani infested speedling trays. Shoot dry weight measurement of seedlings indicated that 12 out of 19 Bacillus isolates showed significantly different shoot dry weight in wheat whereas all the isolates tested in tomato and cucumber gave significantly different shoot dry weight. No significantly different shoot dry weight was obtained for maize or cabbage. Seed emergence findings indicated that none of the Bacillus isolates gave significantly different emergence percentage on wheat, cabbage, tomato, and maize but all of them showed significantly different emergence percentage on cucumber. The results indicate that both the pathogen and the biological control agents exhibited varying levels of specificity on each crop tested. The biological control potential of the best Bacillus isolates was tested on bean and maize crops in the field. Green bean and maize seeds were coated with the selected Bacillus isolates and then sown under field conditions. For each isolate, four replicate treatment plots were established, with and without a R. solani inoculum. Percentage emergence, plant survival levels to harvesting and yield of maize cobs and green beans pods were measured. For all parameters measured the positive and negative controls were not significantly different thereby rendering the results for the entire field study inconclusive. However, Bacillus isolates B77, BII, R5 and R7 improved green bean pod yield and Bacillus Isolate B8I increased maize yield, indicating their potentials as plant growth promoting rhizobacteria (PGPR).
Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2003.

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Yobo, Kwasi Sackey. « Biological control and plant growth promotion by selected trichoderma and Bacillus species ». Thesis, 2005. http://hdl.handle.net/10413/5335.

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Various Trichoderma and Bacillus spp. have been documented as being antagonistic to a wide range of soilborne plant pathogens, as well as being plant growth stimulants. Successes in biological control and plant growth promotion research has led to the development of various Trichoderma and Bacillus products, which are available commercially. This study was conducted to evaluate the effect of six Trichoderma spp. and three Bacillus spp. and their respective combinations, for the biological control of Rhizoctonia solani damping-off of cucumber and plant growth promotion of dry bean (Phaseolus vulgaris L.). In vivo biological control and growth promotion studies were carried out under greenhouse and shadehouse conditions with the use of seed treatment as the method of application. In vitro and in vivo screening was undertaken to select the best Trichoderma isolates from 20 Trichoderma isolated from composted soil. For in vitro screening, dual culture bioassays were undertaken and assessed for antagonisms/antibiosis using the Bell test ratings and a proposed Invasive Ability rating based on a scale of 1-4 for possible mycoparasitic/hyperparasitic activity. The isolates were further screened in vivo under greenhouse conditions for antagonistic activity against R. solani damping-off of cucumber (Cucumis sativus L.) cv. Ashley seedlings. The data generated from the in vivo greenhouse screening with cucumber plants were analysed and grouped according to performance of isolates using Ward‟s Cluster Analysis based on a four cluster solution to select the best isolates in vivo. Isolates exhibiting marked mycoparasitism of R. solani (during ultrastructural studies) viz, T. atroviride SY3A and T. harzianum SYN, were found to be the best biological control agents in vivo with 62.50 and 60.06% control of R. solani damping-off of cucumber respectively. The in vitro mode of action of the commercial Trichoderma product, Eco-T®, and Bacillus B69 and B81 suggested the production of antimicrobial substances active against R. solani. In vitro interaction studies on V8 tomato juice medium showed that the Trichoderma and Bacillus isolates did not antagonise each other, indicating the possibility of using the two organisms together for biological control and plant growth promotion studies. Greenhouse studies indicated that combined inoculation of T. atroviride SYN6 and Bacillus B69 gave the greatest plant growth promotion (43.0% over the uninoculated control) of bean seedlings in terms of seedling dry biomass. This was confirmed during in vivo rhizotron studies. However, results obtained from two successive bean yield trials in the greenhouse did not correlate with the seedling trials. Moreover, no increase in protein or fat content of bean seed for selected treatments was observed. In the biological control trials with cucumber seedlings, none of the Trichoderma and Bacillus combinations was better than single inoculations of Eco-T®, T. atroviride SY3A and T. harzianum SYN. Under nutrient limiting conditions, dry bean plants treated with single and dual inoculations of Trichoderma and Bacillus isolates exhibited a greater photosynthetic efficiency that the unfertilized control plants. Bacillus B77, under nutrient limiting conditions, caused 126.0% increase in dry biomass of bean seedlings after a 35-day period. Nitrogen concentrations significantly increased in leaves of plants treated with Trichoderma-Bacillus isolates. However, no significant differences in potassium and calcium concentrations were found. Integrated control (i.e. combining chemical and biological treatments) of R. solani damping-off of cucumber seedlings proved successful. In vitro bioassays with three Rizolex® concentrations, viz., 0.01g.l-1, 0.1g.l-1 and 0.25g.l-1 indicated that the selected Trichoderma isolates were partly sensitive to these concentrations whereas the Bacillus isolates were not at all affected. In a greenhouse trial, up to 86% control was achieved by integrating 0.1g.l-1 Rizolex® with T. harzianum SYN, which was comparable to the full strength Rizolex® (1g.l-1) application. Irrespective of either a single or dual inoculations of Trichoderma and/or Bacillus isolates used, improved percentage seedling survival as achieved with the integrated system, indicating a synergistic effect. The results presented in this thesis further reinforce the concept of biological control by Trichoderma and Bacillus spp. as an alternative disease control strategy. Furthermore, this thesis forms a basis for Trichoderma-Bacillus interaction studies and proposes that the two organisms could be used together to enhance biological control and plant growth promotion.
Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2005.

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Ramputla, Mogwale Janet. « Nutritional water productivity of hot chilli (capsicum annuum) under infection with meloidogyne javanica and meloidogyne incognitarace 2 ». Thesis, 2019. http://hdl.handle.net/10386/3168.

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Thesis (M.Sc. Agriculture (Soil Science)) -- University of Limpopo, 2019
Nutritional water productivity (NWP) is an assessment tool, which describes the amount of water that has been used to produce selected mineral malnutrition (MMN) elements and micronutrient malnutrition (MNMN) substances. Therefore, it links agricultural production to human nutrition. Deficiencies in MMN elements and/or MNMN substances in human nutrition referred to as malnutrition, had been linked with fatal diseases. Agricultural soils could be affected by soil-borne pathogens such as plant-parasitic nematodes, which could limit the availability of MMN elements and MNMN substances. In some communities, vegetable crops, including chilli are regarded as a major source of MMN elements and MNMN substances. Effects of root-knot (Meloidogyne species) nematodes on NWP of chilli (Capsicum annuum L.) have not been documented. The objective of the study was to determine the effects of increasing population densities of M. incognita race 2 and M. javanica on the NWP of hot chilli plants. A microplot trial was conducted at the Green Biotechnologies Research Centre of Excellence (GBRCE), University of Limpopo, South Africa. Pots were filled with 10-L steam-pasteurised (300oC) sandy clay loam soil sourced from GBRCE and Hygromix-T (Hygrotech, Pretoria North) growth medium in the ratio 3:1 (v/v). Thereafter, three-week-old hot chilli cv. 'Serrano' seedlings were transplanted into each pot, with inoculum prepared by extracting eggs and second-stage juveniles (J2) of M. incognita race 2 and M. javanica from roots of grown nematode susceptible tomato cv. 'Floradade' (Solanum lycopersicum L.) in a 1% NaOCl solution. Fourteen days after transplanting, treatments 0, 50, 125, 250, 625, 1250 and 2000 eggs and second-stage juveniles (J2) of M. incognita race 2 and M. javanica were separately inoculated using a 20 ml plastic syringe into 5-cm-deep holes in pots. At 56 days after the initiation of the treatments, Meloidogyne species xiv decreased soil pH and increased organic carbon, contributing 29 and 43% in total treatment variation (TTV) of the respective variables. Treatment effects caused the pH to decrease. NWP variables against increasing nematode numbers exhibited quadratic relations, with coefficients of determination ranging from 59 to 86% for M. incognita race 2 trial and 80 to 98% for M. javanica trial. Meloidogyne species population densities against plant variables did not show any significant relationship, except for root galling and chlorophyll content where treatments contributed 76, 98 and 47% TTV of the respective variables. Generally, root galling increased with increase in Meloidogyne species population densities, whereas chlorophyll content decreased with increasing inoculum levels. Nematode variables against their increasing population exhibited quadratic relationship with the model explained by 44 to 95% for M. incognita race 2 and 28 to 82%, association, respectively for M. javanica. In conclusion, Meloidogyne species interfered with NWP of mineral elements in chilli plant and therefore, nematode management practices should be done to reduce the nematode population densities that would confer quality to agricultural produce for human health benefits.

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Msiska, Zola. « Arbuscular mycorrhizal fungi of Ugandan banana plantation soils ». Diss., 2003. http://hdl.handle.net/2263/28719.

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Tesfagiorgis, Habtom Butsuamlak. « Studies on the biocontrol of seedling diseases caused by Rhizoctonia solani and Pythium sp. on sorghum and tef ». Thesis, 2003. http://hdl.handle.net/10413/6254.

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Rhizoctonia solani and Pythium spp. are aggressive soil-borne fungal pathogens responsible for seed rot and seedling damping-off of many crops. With increased environmental and public concern over the use of chemicals, biological control of these diseases has been attracting more attention. However, success with this strategy depends on the development of effective antagonists, which requires repeated in vitro and in vivo tests. Bacillus spp. were isolated from a soil sample obtained from a field where sorghum and tef had been grown for at least two years. Potential Bacillus isolates were screened for their ability to inhibit in vitro growth of R. solani and Pythium sp. Among 80 isolates tested, endospore forming Bacillus spp. H44 and H51 gave highest antifungal activity against the two test-pathogens in three consecutive tests. Results demonstrated that both H44 and H51 have potential as biocontrol agents against diseases caused by these two pathogenic fungi. The interaction between three isolates of Trichoderma (T. harzianum Eco-T, Trichoderma spp. SY3 and SY4) and Pythium sp. were investigated using in vitro bioassays together with environmental scanning electron microscopy (ESEM). Visual observation on the dual culture tests revealed that hyphal growth of Pythium was inhibited by these antagonists soon after contact between the two organisms within 3-4 days of incubation. The ESEM investigations showed that all three isolates of Trichoderma grew toward the pathogen, attached firmly, coiled around and penetrated the hyphae of the pathogen, leading to the collapse and disintegration of the host's cell wall. Degradation of the host cell wall was postulated as being due to the production of lytic enzymes. Based on these observations, antibiosis (only by Eco-T) and mycoparasitism (by all three isolates) were the mechanisms of action by which in vitro growth of Pythium sp. was suppressed by these Trichoderma isolates. The reduction of seedling diseases caused by R. solani and a pythium sp. were evaluated by applying the antagonists as seed coating and drenching antagonistic Bacillus spp. (B81, H44 and H51) and Trichoderma (T. harzianum Eco-T and Trichoderma spp. SY3 and SY4). On both crops, R. solani and Pythium sp. affected stand and growth of seedlings severely. With the exceptions of H51, applications all of isoltes to seeds reduced damping-off caused by R. solani in both crops. Application of Eco-T, H44 and SY3 to sorghum controlled R. solani and Pythium sp. effectively by yielding similar results to that of Previcur®. On tef, biological treatments with Eco-T and SY4 reduced seedling damping-off caused by R. solani and Pythium sp., respectively, by providing seedling results similar to the standard fungicides, Benlate® and Previcur®. Most other treatments gave substantial control of the two pathogens on tef. Overall, Bacillus sp. H44 and T harzianum Eco-T were the best biocontrol agents from their respective groups in reducing damping-off by the two pathogens. In all instances, effects of application method on performance of biocontrol agents and adhesive on emergence and growth of seedlings were not significant. A field trial was conducted at Ukulinga Research Farm at the University of Natal, Pietermaritzburg, South Africa, to determine efficacy of biological and chemical treatments on growth promotion and reduction of damping-off incited by R. solani and Pythium sp., and to evaluate the effects of a seed coating material, carboxymethyl cellulose (CMC), on seedling emergence and disease incidence. Seeds of sorghum and tef were treated with suspensions of antagonistic Bacillus H44 or T harzianum Eco-T, or sprayed with fungicides, Benlate® or Previcur®. Application of Benlate® and Previcur® during planting significantly increased the final stand and growth of sorghum seedlings. Seed treatments with both H44 and Eco-T substantially controlled damping-off caused by Pythium, resulting in greater dry weights of seedlings than the standard fungicide. However, they had negative effects when they were tested for their growth stimulation and control of R. solani. The CMC had no significant effect on germination and disease levels. These results showed that these antagonists can be used as biocontrol agents against Pythium sp. However, repeated trials and better understanding of the interactions among the antagonists, the pathogens, the crop and their environment are needed to enhance control efficiency and growth promotion of these antagonists. Some of these biocontrol agents used in this study have the potential to diseases caused by R. solani and Pythium sp. However, a thorough understanding of the host, pathogen, the antagonist and the environment and the interactions among each other is needed for successful disease control using these antagonists.
Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2003.

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Otfinowski, Rafael. « Patterns and processes of exotic plant invasions in Riding Mountain National Park, Manitoba, Canada ». 2008. http://hdl.handle.net/1993/3065.

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Invasive exotic species threaten the biodiversity and function of native ecosystems. Existing models, attempting to predict and control successful invaders, often emphasize isolated stages of in their life history and fail to formalize interactions between exotic species and recipient environments. In order to elucidate key mechanisms in the success of select invaders, I investigated the role of dispersal, establishment, proliferation, and persistence in their threat to natural areas. Focusing on Riding Mountain National Park, Manitoba, Canada, I integrated the native climatic range and biological traits of 251 exotic vascular plants reported inside and outside the park. Based on their climatic range in Europe, 155 among 174 exotic plant species absent from the Park were predicted to establish within its boundaries; among these, 40 clonal perennials were considered the highest threat to the Park’s biodiversity. Focusing on smooth brome (Bromus inermis Leyss.), a Eurasian perennial, threatening the structure and function of native prairies throughout the Great Plains, I extended my research to investigate the role of dispersal, establishment, proliferation, and persistence in characterizing its threat to the endemic diversity of northern fescue prairies, protected within Riding Mountain National Park. Patterns of smooth brome invasions were contingent on the type of propagules dispersed. The shallow dispersal gradient of individual florets combined with the steeper gradient of panicles and spikelets suggested that smooth brome is capable of simultaneously invading along dense fronts as well as by establishing isolated foci. While low correlations between the number of dispersed seeds and their recruitment suggested post-dispersal transport, seedling establishment remained contingent on prairie diversity. Seedling biomass increased with declining plant diversity, however, its impact depended on the availability of soil nitrogen. As a result, disturbed areas, preserving the root function of native plants, resisted smooth brome establishment. Even though low nitrogen contributed to a decline in seedling biomass, physiological integration between ramets facilitated their vegetative proliferation in low resource environments. Despite its rapid establishment and proliferation, smooth brome productivity declined at the center of invading clones. Although field and greenhouse observations failed to implicate soilborne pathogens, reasons for the observed decline remain unresolved. My research demonstrates that while Riding Mountain National Park and other natural areas in western Canada will continue to be impacted by exotic plants, integrating key stages in their life history provides an important conceptual framework in predicting their threat to natural areas and prioritizing management.
October 2008

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(12298370), Alison S. Jensen. « Redefining pachymetra root rot management strategies and cultivar resistance in commercial sugarcane fields ». Thesis, 2020. https://figshare.com/articles/thesis/Redefining_pachymetra_root_rot_management_strategies_and_cultivar_resistance_in_commercial_sugarcane_fields/19426862.

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Pachymetra chaunorhiza is an important soilborne pathogen of sugarcane and is found only in Australia. Pachymetra root rot is managed primarily by growing resistant cultivars, which are chosen for planting based on oospore levels in the soil. This management strategy does not account for differences in virulence among Pachymetra populations, despite previous research demonstrating that two genetically distinct groups of Pachymetra occur, which may differ in pathogenicity. Higher than expected yield losses have been associated with high oospore levels under some cultivars with intermediate resistance to the pathogen. Increased virulence of Pachymetra towards specific cultivars, following long-term exposure to that cultivar, could explain these reports of high yield losses in intermediate cultivars. This research project aimed to deliver knowledge of the genetic and pathogenic variation among Pachymetra populations in different growing regions and following long-term exposure to different cultivars. The level of genetic and pathogenic variation among Pachymetra populations and the factors contributing to pachymetra root rot were investigated in a series of field trials, glasshouse experiments and laboratory molecular analyses. Results from field experiments generally support the current guidelines used for Pachymetra management. No evidence was found to support the hypothesis that planting the same intermediate cultivar over multiple crop cycles could lead to higher than expected yield losses due to pachymetra root rot. Yield losses of 17 percent were associated with continual cropping of Q208A in a field trial near Bundaberg, in the southern Queensland sugarcane-growing region. A range of putative Pachymetra genes were identified which could play a role in pathogenicity. Collectively, the findings from this research supported the conclusion that two genetically distinct groups of Pachymetra occur in growing regions a) north of Townsville and b) south of Townsville, as previously reported. Three potential native hosts of Pachymetra were also identified, including Themeda australis and this finding supports the theory that lighter soil types are conducive to pachymetra root rot.

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