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1
Das, Jyotsna. "Serological detection of sphaerostible repens B. and Br. causing violet root rot disease of tea and its management". Thesis, University of North Bengal, 2002. http://hdl.handle.net/123456789/915.
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Subbalakshmi, P. "Biochemical and serological studies on charcoal stump rot disease of tea and its management". Thesis, University of North Bengal, 2008. http://hdl.handle.net/123456789/1356.
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Tollefson, Stacy Joy. "Compost Water Extracts And Suppression Of Root Rot (F. Solani F. Sp. Pisi) In Pea: Factors Of Suppression And A Potential New Mechanism". Diss., The University of Arizona, 2014. http://hdl.handle.net/10150/338972.
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One of the motivating reasons for the development of hydroponics was avoidance of root pathogens. Hydroponics involves growing crops in relatively sterile media, isolated from the underlying soil which may have disease pressure. However, even when hydroponics is coupled with controlled environments such as high tunnels and climate-controlled greenhouses, soil-borne pathogens can enter the growing area and proliferate due to optimal environmental conditions for pathogen growth. Control of root pathogens is difficult and usually achieved through synthetic fungicides since few biocontrol options are available. Compost water extracts (CWE) have recently been gaining the attention of greenhouse growers because they may be a low-cost, environmentally friendly approach to control root disease. CWE are mixtures of compost and water incubated for a defined period of time, either with or without aeration, and with or without additives intended to increase microbial populations, which in turn suppress disease. Much anecdotal, but very little scientific, evidence exists describing CWE effect on suppressing soil-borne pathogens. The present study 1) examined the effect of an aerated CWE on disease suppression at the laboratory scale and in container studies using different soilless substrates, 2) investigated a phenotypic change at the root level caused by CWE that may be associated with disease suppression, and 3) isolated some factors in the production of CWE that affect the ability of a CWE to suppress disease. The common model pathogen-host system of Fusarium solani f.sp. pisi and pea was used to examine CWE-induced disease suppression, with information then being translatable to similar patho-systems involved in greenhouse crop production. In the first study, laboratory-based root growth and infection assays resulted in 100% suppression of F. solani when roots were drenched in CWE. These protected seedlings were then taken to a greenhouse and transplanted into fine coconut coir, watered with hydroponic nutrient solution, and grown for five weeks. At the end of the experiment, 23% of the shoots of the pathogen-inoculated, CWE-drenched seedlings remained healthy while only 2% of the inoculated seedlings without CWE drench remained healthy. All of the roots of the inoculated seedlings developed lesions, even those drenched in CWE. However, 29% of the CWE drenched roots were able to recover from disease, growing white healthy roots past the lesion, while only 2% recovered naturally. A shorter-term container study was conducted in the laboratory to determine the effects of CWE-induced suppression when peas were grown in different substrates and to determine if the hydroponic nutrient solution had an effect on the suppression. Peas were grown in sterilized fine and coarse coconut coir fiber and sand irrigated with water, with a second set of fine coir irrigated with hydroponic nutrient solution. Pea seeds with 20-25mm radicles were inoculated with pathogen and sown directly into CWE-drenched substrate and grown for three weeks. At the end of the experiment, 80%, 60%, 90%, and 50% of the shoots of the inoculated, CWE-drenched seedlings remained healthy when grown in fine coir, coarse coir, sand, and fine coir irrigated with hydroponic nutrient solution, respectively. Nearly 100% of the roots grown in coconut coir substrates again developed necrotic lesions but 83%, 87%, 100%, and 87% grew healthy roots beyond the disease region. The hydroponic nutrient solution had a negative effect on suppression, with a reduction of at least 30 percentage points. Sand demonstrated a natural ability to suppress F. solani. Only 23% of inoculated seedlings had dead or dying shoots by the end of the experiment (compared to 77-80% in coir substrates) and although all but one of the roots developed lesions, all were able to recover on their own with CWE. CWE further increased shoot health and also prevented 57% of the roots from developing lesions. In a second study, two different CWE were used to examine the effect on root border cell dispersion and dynamics in pea, maize, cotton, and cucumber and its relation to disease suppression. Dispersal of border cells after immersion of roots into water or CWE was measured by direct observation over time using a compound microscope and stereoscope. Pictures were taken and the number of border cells released into suspension were enumerated by counting the total number of cells in aliquots taken from the suspension. Border cells formed a mass surrounding root tips within seconds after exposure to water, and most cells dispersed into suspension spontaneously. In CWE, >90% of the border cell population instead remained appressed to the root surface, even after vigorous agitation. This altered border cell phenomena was consistent for pea, maize, and cotton and for both CWE tested. For most cucumber roots (n=86/95), inhibition of border cell dispersal in both CWE was similar to that observed in pea, maize, and cotton. However, some individual cucumber roots (8±5%) exhibited a distinct phenotype. For example, border cells of one root immersed into CWE remained tightly adhered to the root tip even after 30 minutes while border cells of another root immersed at the same time in the same sample of CWE expanded significantly within 5 minutes and continued to expand over time. In a previous study, sheath development over time in growth pouches also was distinct in cucumber compared with pea, with detachment of the sheaths over time, and root infection was reduced by only 38% in cucumber compared with 100% protection in pea (Curlango-Rivera et al. 2013). Further research is needed to evaluate whether this difference in retention of border cell sheaths plays a role in the observed difference in inhibition of root infection. In the third study, a series of investigations were conducted to isolate different factors that contribute to the suppression ability of a CWE by changing incrementally changing some aspect of the CWE production process. The basic aerated CWE recipe (with molasses, kelp, humic acid, rock phosphate, and silica) provided 100% protection of pea from root disease while the non-aerated basic recipe CWE provided 72% protection. Aerated CWE made of only compost and water resulted in 58% protection. It was found that molasses did not contribute to the suppression ability of the ACWE, while kelp contributed strongly. When soluble kelp was added by itself to the compost and water, the CWE provided 80% suppression. However, when all additives were included except molasses and kelp, suppression remained high (93%) indicating that humic acids, rock phosphate, and/or silica were also major contributors toward the suppression effect. Optimal fermentation time for ACWE was 24 hr to achieve 100% suppression, with increased time resulting in inconsistent suppression results. Optimal fermentation time for NCWE was 3 days or 8 days. These studies are important contributions to understanding the differences that might be expected in CWE suppression when growing in different substrates, some of the factors in the production of CWE that affects the ability of a CWE to suppress disease, and the phenotypic effect CWE has on the root zone of plants and the possible relationship between that effect and disease suppression.
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Bhutia, Lhanjey Phuti. "Screening of phosphate solubilizing fungi from tea rhizosphere of Sikkim and formulation of bioinoculants with a plant growth promoting rhizobacterium for management of charcoal stump root disease of tea". Thesis, University of North Bengal, 2010. http://hdl.handle.net/123456789/1465.
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Chowdhury, Prabir Roy. "Exploitation of Rhizosphere microorganisms of tea for protection against root rot pathogens". Thesis, University of North Bengal, 2008. http://hdl.handle.net/123456789/1063.
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Xia-Hong, He. "Bio-control of root rot disease in vanilla". Thesis, University of Wolverhampton, 2007. http://hdl.handle.net/2436/15398.
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Fusarium oxysporum Schl. var. vanillae (Tucker) Gondon is known to cause root rot in Vanilla planifolia Andrews in most regions where it is grown, including the major plantations in Xishuangbanna, Yunnan Province of China. This is of serious economic concern to the Province since the vanilla flavouring extractable from the beans of the plant is a valuable food product and an important export commodity. There are no fungicides registered for the control of Fusarium root rot and the only available chemical control methods are ineffective and cause serious contamination of the soil. Breeding for resistance is difficult when no dominant gene is known or where little information is available on fungal pathogenicity. Biocontrol is the main alternative for disease control in this crop, an attractive approach because of increasing concerns for environmental protection. The investigation considers two biocontrol strategies: first the introduction of virulent, antagonistic, non-pathogenic strains, closely-related to the pathogen, to overcome pathogenic populations in infected soils; second the use of essential oils with antimicrobial properties when applied to infected soils. Pathogenicity tests have been done on 81 out of 87 F. oxysporum isolates collected in Yunnan Province. Among these, 32 isolates were non-pathogenic and 49 were pathogenic. The pathogenicity results showed the complexity of F. oxysporum in Yunnan. Seventeen isolates were recovered from the Daluo plantation, of which 14 were pathogenic isolates and 3 non-pathogenic isolates; 26 from the Menglun plantation, in which 12 were pathogenic and 14 were non-pathogenic; 18 isolates from the Manjingdai plantation, in which 12 isolates were pathogenic, whilst the other 6 were non-pathogenic and 20 were obtained from the plantation in Hekou i County, of which 11 were pathogenic isolates and 9 were non-pathogenic. Genetic diversity within this population of F. oxysporum has been investigated with respect to vegetative compatibility and to determine the relationship between VCGs and virulence. The VCG results showed that the 87 strains of Fusarium oxysporum f.sp vanillae isolated from Yunnan Province were complex. They could be distributed into 12 different VCGs and that a direct relationship between VCGs group and virulence could not be drawn. Two non-pathogenic strains, ML-5-2 and HK-5b-4-1, have been screened from 87 strains as candidate biocontrol agents by pathogenicity and VCG, which are self-incompatible and closely related to the pathogens. These two strains were effective in vanilla root rot control in controlled environments, but their effects in field experiments were less conclusive. Seven essential oils, which have long been regarded as having inhibitory effects on pathogens in nature, have also been investigated as biocontrol agents. Three oils, cinnamon oil, thyme oil and clove oil, were effective in inhibiting the growth of pathogen in vitro. These oils may develop into useful components of different management strategies with non-pathogenic strains. For the future, consideration will need to be given to the mechanism(s) of the interaction of the antagonistic components with the soil microbe population and host plant and also to appropriate formulation, to take account of soil type, crop status, cultural practices, environmental and economic factors. Biocontrol methods have considerable potential but must be acceptable to farmers as part of an overall crop management programme.
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West, Jon. "Chemical control of Armillaria root rot". Thesis, University of Reading, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386565.
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Olsen, Mary. "Cotton (Texas) Root Rot". College of Agriculture, University of Arizona (Tucson, AZ), 2015. http://hdl.handle.net/10150/346609.
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Revised 02/2015; Originally published: 2000.The most important disease of woody dicotyledonous plants in Arizona is Phymatotrichopsis root rot (Cotton or Texas root rot) caused by a unique and widely distributed soil-borne fungus, Phymatotrichopsis omnivora. The fungus is indigenous to the alkaline, low-organic matter soils of the southwestern United States and central and northern Mexico.
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Mabey, M. "An investigation of the foot rot disease complex on peas". Thesis, Manchester Metropolitan University, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.377699.
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Fernandes, Priya. "Study of charcoal rot disease using the model plant Arabidopsis Thaliana". Thesis, Wichita State University, 2013. http://hdl.handle.net/10057/7035.
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Macrophomina phaseolina is a warm climate fungal pathogen of the Botryosphaeriaceae family that causes charcoal rot disease in over 700 plant species including commercially grown plants such as soybean, maize, peanut and cotton. Currently used management approaches for the disease including irrigation, addition of organic amendments and crop rotation are not very effective. Limited knowledge on host-pathogen interactions hinders the development of disease resistance strain by genetic engineering. To understand the disease mechanisms at the molecular level, we chose to use Arabidopsis thaliana as a model to study charcoal rot. In this study we established Arabidopsis as a susceptible host for Macrophomina phaseolina. Furthermore, the cellular process of infection and propagation of the pathogen within the host system during the early and late stages of infection were examined by microscopy. Recent studies have demonstrated the crucial roles of different phytohormones in the induction of defense signaling pathways. Here, the interactions between plant hormone-mediated signaling and plant disease resistance were studied using a genetics approach with a hope of understanding the mechanisms of plant immunity against Macrophomina phaseolina mediated by auxin, SA, JA, ET and ABA. In this study we hypothesized that the necrotrophic fungus M. phaseolina invades the host by affecting the biosynthesis of plant hormones (mainly JA, ET and auxin) and/or activation of the corresponding hormonal pathways that are directly or indirectly involved in mounting a defense response against the pathogen. Several mutants that carry mutations in genes that are involved in hormone biosynthesis or signaling were obtained and tested. Results from our study showed that auxin, ET and SA signaling pathways have possible roles of in imparting pathogen resistance against M. phaseolina.Thesis (M.S.)--Wichita State University, Fairmount College of Liberal Arts and Sciences, Dept. of Biological Sciences.
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Raziq, Fazli. "Biological and integrated control of the root rot caused by Armillaria mellea". Thesis, University of Reading, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.245321.
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Songa, Wilson A. "Variation and survival of Macrophomina phaseolina in relation to screening common bean (Phaseolus vulgaris L.) for resistance". Thesis, University of Reading, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283673.
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Woodbridge, Bill. "The biology of Typhula incarnata causing snow rot disease of winter barley". Thesis, University of Hull, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.280359.
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Bibble, Anthony John. "Factors associated with pea foot rot complex and methods of disease prediction". Thesis, Manchester Metropolitan University, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.332893.
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Mauk, P. A. y R. B. Hine. "A Predictive System for Disease Incidence of Black Root Rot of Cotton". College of Agriculture, University of Arizona (Tucson, AZ), 1987. http://hdl.handle.net/10150/204490.
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A quantitative technique has been developed to assay cotton soils for populations of Thielaviopsis basicola, a soil occurring fungus that causes the seedling disease of cotton known as Black Root Rot. The procedure utilizes a soil dilution technique with a carrot extract agar containing etridiazol, Mystatin, streptomycin sulfate, chlortetracycline, calcium carbonate and PCNB. Populations of the fungus have been monitored from April to December, 1986 in a heavily infested Pima S-6 field in cooperation with Bob Cockrill, a Coolidge grower. When field soils containing approximately 600 propagules of the fungus per gram of air dry soil were planted to Pima S-6 in the laboratory, 75-100% and 50-75% cortical decay occurred at 20 and 28 C, respectively. This seedling damage was related to subsequent reduced seedling vigor.
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Pryor, Barry, Mike Matheron y Patricia Figuli. "Characterization of Alternaria isolates associated with Alternaria Rot of Citrus". College of Agriculture, University of Arizona (Tucson, AZ), 2003. http://hdl.handle.net/10150/198111.
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Alternaria rot of citrus is a serious problem in citrus production world wide. In Arizona, the disease is most commonly found in Minneola tangelos and navel oranges grown in Maricopa County. Alternaria rot occurs primarily as a stem-end rot on fruit held in cold storage. However, under optimum conditions the disease occurs as a stylar-end rot in the orchards. In Arizona, the disease can significantly reduce yield, and annual fruit losses have been estimated at 0.5 box per tree. In terms of fruit quality, this disease can be a serious problem for the fresh fruit market as well as for the processing industry because only a small amount of rot imparts a bitter flavor and small black fragments of rotted tissue spoil the appearance of the juice. The application of fungicides is the most common tactic used to reduce losses to this disease. However, to date, no consistent reduction in disease has been achieved through chemical applications. This suggests that additional information relating to the biology of the pathogen and the epidemiology of disease will be necessary for the successful development of a reliable disease management program.
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Glue, Joshua Barnaby. "Engineering Allium White Rot Disease Resistance in Allium Species and Tobacco Model Species". Thesis, University of Canterbury. School of Biological Sciences, 2009. http://hdl.handle.net/10092/3513.
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Allium white rot (AWR) is a soilborne disease that seriously damages commercial cultivation of onion (Allium cepa) and garlic (Allium sativum) crops. The disease has been found everywhere onions are cultivated and at present no system of control has been found that fully prevents the occurrence of the disease. The fungus responsible for the disease, Sclerotium cepivorum, uses oxalic acid to kill Allium bulb and root tissue in growing onion and garlic plants. Research suggests recombinant oxalate oxidase and oxalate decarboxylase enzymes may be able to degrade this acid and confer resistance against pathogens that rely on it, such as Sm. cepivorum or Sclerotinia sclerotiorum. To test the efficacy of these enzymes against white rot pathogens, three transgenes for wheat oxalate oxidase, barley oxalate oxidase and Flammulina oxalate decarboxylase were transformed into onions and garlic by Agrobacterium-mediated transformation. Allium species are highly recalcitrant to transformation, so these three transgenes were also transformed into tobacco to provide fast-recovering, easy to test transformants to assess the efficacy of the transgenes. Transformed garlic and tobacco lines were analysed to assess the integration and expression of the transgenes, then challenged with Sm. cepivorum or Sa. sclerotiorum, respectively, to assess the bioactivity of recombinant wheat oxalate oxidase, barley oxalate oxidase, and Flammulina oxalate decarboxylase against oxalic acid-dependent pathogens. Results show that one line of tobacco expressing the Flammulina oxalate decarboxylase enzyme was found to be consistently resistant to Sclerotinia sclerotiorum. Garlic lines transformed with this transgene failed to display stable transgene expression or disease resistance, possibly due to silencing of the transgene in recovered transformant tissue.
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Matheron, M. y J. Matejka. "Phytophthora Gummosis and Root Rot of Citrus-Effect of Temperature on Disease Development". College of Agriculture, University of Arizona (Tucson, AZ), 1991. http://hdl.handle.net/10150/215726.
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Experiments were conducted to examine the effect of temperature on development of Phytophthora gummosis and root rot of citrus as well as the influence of temperature on sporulation of Phytophthora citrophthora and P. parasitica. Maximum production of sporangia by each fungus occurred at 25 C, while slight or no sporangia production occurred at 10, 15, and 35 C. Minimal growth of lesions was observed when stems of rough lemon were inoculated with P. citrophthora or P. parasitica and incubated at 5 and 30 C or 10 and 30 C, respectively. The inhibitory and stimulating effect of certain temperatures on sporulation and disease development could be useful for determination of optimum times for application of fungicides or other disease control measures.
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Thorpe, Catherine. "Molecular genetic investigation of reduced virulence mutants of Erwinia carotovora subspecies atroseptica". Thesis, University of Warwick, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308021.
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Kamel, M. A. M. "ETIOLOGY OF CROWN ROT OF ORGANIC BANANAS". Doctoral thesis, Università degli Studi di Milano, 2015. http://hdl.handle.net/2434/342536.
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Crown rot is one of the most important postharvest diseases with a great negative impact on banana fruit quality. Bananas are harvested green and many packaging processes are carried out before coming on the market. The infections occur at harvest, but the symptoms appear after overseas transportation. Different pathogens are involved in crown rot, varying according to farming area. Little is known about its etiology and causal agents in organic farming. Dominican Republic is one of the leading exporters of organic bananas, and therefore, in this PhD thesis, five organic farms and their corresponding packing stations located in Valverde were investigated. To the best of our knowledge this is the first study covering Dominican Republic and it focused in particular on: the disease etiology, conditions, infection time and mechanisms that determine its development. Over a period of three years, 558 banana hands were collected and a total of 5000 fungal colonies were obtained from the crown tissues and 1750 representative colonies were purified. The identification of mycoflora associated with crown tissues was carried out with the final aim to search for disease management strategies compatible with organic production. Fungi were found in all the analyzed samples collected from various processing stages: from field to packing houses, and obtained in high rate starting from field from flowers as well as crown parts. The diffusion of the pathogen inoculum occurs principally during the banana processing, especially during the dehanding and in washing tanks. The final crown trimming followed by washing and quality of water used in the application of protective products were the critical points of crown infections. Five hundred and eighteen representative colonies were characterized and identified using morphological and molecular methods. The fungal community was dominated by Fusarium, the most frequent genus (55%) found in more than 80% of all analyzed samples. It was represented by nine species; F. incarnatum 53%, F. verticillioides 12%, F. sacchari 12%, F. proliferatum 7%, and F. solani 6%. Strains belonging to eight less frequent genera were represented by Colletotrichum musae 7% and found in 13% of all samples; Lasiodiplodia theobromae 4% and L. pseudotheobromae 1%, both found in 7% of all samples; Nigrospora sp. 11%, Alternaria spp. 6%, Phoma spp. 2%, Pestalotiopsis sp. 2%, Curvularia spp. 1% and Microdochium sp. 1%. Considering the main genera, the results based on morphological and molecular aspects showed a high variability among strains. By conducting the experimental inoculation trials, C. musae strains resulted from the most virulent among different species, followed by F. sacchari, L. theobromae, L. pseudotheobromae and F. verticillioides. The remaining strains had low pathogenicity, and their role could be ancillary in the crown rot development, or could be considered saprophytic. Summarizing the isolation frequency and pathogenicity tests, F. incarnatum strains played the main role in crown rot disease of organic bananas in the investigated areas.
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Rungjindamai, Nattawut. "Biological control of brown rot disease caused by Monilinia Laxa in cherries and plums". Thesis, University of Kent, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.633823.
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Monilinia laxa is the causal agent of brown rot disease on stone fruits, and also causes blossom wilt and twig canker. The common practice used to manage this disease is through fungicide treatments, especially during the flowering and fruiting period. However the demand to reduce fungicide input has been increasing and there is a growing number of reports of M. laxa strains that are resistant to fungicides. This study is based on the development of biological control agents (BCAs) as an alternative strategy for disease control using either existing BCA products or new indigenous isolates from UK orchards. Efficacy of exotic commercial BCAs against M laxa was investigated using in vivo tests on cherries and plums. Serenade partially inhibited M laxa while the other four BCA products (BioPK, BoniProtect, Prestop and Trianium) had no effect against the pathogen. Indigenous BCAs were isolated from healthy leaves, intact fruits and mummified fruits of cherries and plums collected from orchards in Kent. A total of 217 isolates were screened against two strains of ill! laxa in a series of in vitro tests using a dual culture technique. From these tests, 12 isolates were selected for fUliher screening. The final screening based on in vivo tests on cherries and plums narrowed these down to two isolates with good potential for development. They were further tested under post-harvest conditions by dipping cherries and plums in suspensions of cells of the individual control agents and storing treated fruit under standard storage conditions. The two BCAs did not control brown rot on cherries under these conditions, and the low incidence of natural infection by fvi laxa in plums also meant that significant control could not be demonstrated. The two BCAs were identified as Bacillus amyloliquefacienslsubtilis (isolate B91) and Aureobasidium pulIulans (isolate YI26). Their modes of action were investigated. Bacillus sp. B91 was shown to produce soluble and volatile organic compounds which inhibited M laxaJ while A. pulIulans Y126 apparently competes with the pathogen for nutrients and did not produce inhibitory compounds. The capability of B91 and Y126 to . grow and survive at low temperatures was studied. Bacillus sp. B91 was shown to be a mesophillic bacterium that could grow at 10-2S0C but suffered significant mOltality at 0 and SOC, while A. pulIulans Y126 was both mesophilic and psychrotolerant because it grew between 0-2SoC, although 20°C was the optimum temperature. Once all nutrients were . removed, Y12.6 was able to survive for several weeks in all test temperatures (0-2S°C) but showed significant mortality at 2SOC. The capability of B91 to survive at 20 and 2SoC was h-igher than low temperatures (O-IS°C) . . Molecular studies were used to show that M laxa populations on mummified fruits were likely to be responsible for fruit rot infection in the same orchards the following season. Geographical origin and host also influenced the population structure of A1. laxa. Field trials were conducted in which mummified fruits were either treated with a commercial fungicide (Indar) or BCAs to investigate whether these treatments would significantly reduce sporulation of the pathogen in the field thus reducing the infection load in . the spring. Spraying in Winter alone was not sufficient to significantly suppress sporulation of M laxa but the efficacy was improved when the control agents were applied in Spring either as a single spray or in combination with a Winter spray. Sprays of Indar or A. pulIulans Y126 greatly suppressed sporulation on mummified fruits if the fruits were treated on both occasions. It was concluded that the two novel, indigenous BCAs have potential to control M laxa but more research is necessary to develop these two potential BCAs for field use.
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Cruz, David Ricardo Jimenez. "Influence of soils, nutrition, and water relations upon charcoal rot disease processes in Kansas". Thesis, Kansas State University, 2011. http://hdl.handle.net/2097/10747.
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Master of ScienceDepartment of Plant Pathology
Christopher R. Little
Christopher R. Little
Charcoal rot, caused by Macrophomina phaseolina, is the most important soybean disease in Kansas. Several strategies have been recommended to control this disease including crop rotation, lower plant densities, biological control, plant resistance and tolerance, and fungicide application. However, those techniques have not been completely effective and the information concerning soil texture, irrigation and micronutrient fertility (particularly manganese) upon charcoal rot disease severity and the pathogen population is limited. The objective of this study was to determine key factors that affect the biology of M. phaseolina and charcoal rot processes under laboratory, greenhouse and field conditions. M. phaseolina microsclerotia were produced from PDA pure isolate and infested Japanese millet in the laboratory and characterized by different techniques such as serial dilutions in semi selective media with the aim to produce quality inoculum to reliably infect soybean seedling roots under greenhouse conditions; production of inoculum by infesting Japanese millet was the most efficient method. Root colonization and root infection of soybean seedlings was assessed through the use of M. phaseolina inoculum under controlled conditions in the greenhouse. Root infection by M. phaseolina and microsclerotia longevity in soil is determined by environmental factors such as soil moisture content, soil texture and source of inoculum. The objective of the greenhouse study was to determine the impact of these variables on seedling root infection at the V1 and V2 development stages. Artificial soils with different textures were infested; M. phaseolina microsclerotia and soybean seedlings were exposed to different soil moisture contents including pot saturation, pot (field) capacity, and permanent wilting point. Soil populations and levels of root colonization for the stages were assessed by estimating CFUs and root length. Results indicate that soil texture has a significant impact upon root morphology and root length. Root populations of M. phaseolina were significantly higher in sandy soil textures and lower in the fine-textured soils, suggesting an impact of soil water holding capacity in the root infection process. The effect of water stress on seedling root colonization by M. phaseolina indicates that early infection may be more important than previously thought. A field study was also conducted to determine the effect of the aforementioned variables in a 2-year field experiment conducted at two Kansas locations. Pathogen colonization was iii assessed by measuring colony-forming units (CFUs) from ground root tissue at R2-R4 (post-flowering/early pod development) and R8 (maturity) stages. Soil populations (pre-planting and post-harvest) of M. phaseolina, yield parameters, and plant characteristics were obtained. Results indicated that there are complex relationships between soil physiochemical properties (pH, NPK content, exchangeable cations, and organic matter) and soil texture (sand, soil, and clay composition), which may mitigate disease severity and pathogen levels in host tissue. Results also indicated that in natural M. phaseolina-infested soils, cropping history and soil texture play an important role in charcoal rot processes and influence the levels of pathogen soil populations, root colonization at maturity and, more importantly, soybean yield.
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Malligan, Cassandra D. "Crown rot (fusarium pseudograminearum) symptom development and pathogen spread in wheat genotypes with varying disease resistance". University of Southern Queensland, Faculty of Sciences, 2009. http://eprints.usq.edu.au/archive/00006225/.
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[Abstract]Crown rot, caused by Fusarium pseudograminearum (Fpg), is an important soilborne disease of wheat and barley. The degree of crop damage depends on seasonal conditions. Typically, high moisture conditions early in the season encourage seedling infection from stubble residues. Moisture stress later in the season leads to the production of unfilled “whiteheads”. Current control relies on cultural practices and sowing of partially resistant varieties. In order to understand the nature of partial resistance, I have examined the patterns of disease symptom development and pathogen spread in susceptible and partially resistant tissues of both pot-grown wheat, barley and oat seedlings and field-grown inoculated wheat trials. Further research was conducted to determine whether differences in pathogenicity occur amongst a small subset of Australian Fpg isolates. Seedling experiments confirmed that differences in disease ratings between susceptible and partially resistant genotypes are detected in younger leaf sheaths of older seedlings. At later harvest times differences between these genotypes are not significant in older leaf sheaths. Re-isolation of Fpg from inoculated seedlings has shown that each tissue was infected later in partially resistant genotypes compared to susceptible ones with a significantly lower number of isolations recorded at each harvest time in 42 day old seedlings. Barley cultivars were rapidly infected by the pathogen and exhibited high levels of disease symptoms. By comparison levels of infection in oats were low compared to all other genotypes. No significant differences between genotypes were observed in coleoptile tissues, either in fungal colonisation or development of disease symptoms. Disease development in the subcrown internode varied between lines/cultivars but was not representative of the relative susceptibility of each genotype. The pathogen did not appear to invade plant tissue via the vascular system but rather spread directly across the stem from leaf sheath to leaf sheath. Field trials were designed to study disease symptom development and localisation of Fpg hyphae in all expanded tissues (excluding head and roots) in wheat genotypes of known susceptibility to crown rot. Plants were harvested at approximately fortnightly intervals throughout the growing season. The main effects and interactions of harvest, genotype and tiller on each plant part were examined with a detailed statistical analysis of differences seen in these factors between susceptible and partially resistant wheat genotypes, in two inoculated field trials. While differences between genotypes were mostly not significant at each harvest when disease rating or isolations from leaf sheath tissues were examined, important differences between susceptible and resistant genotypes were seen in disease developments and Fpg infections of stem tissue in field trials. Restriction of pathogen growth and symptom development was more pronounced in the tissues of 2-49 (possesses seedling resistance) than in the field resistant Sunco. At present, the mechanisms that lead to these resistance responses are unknown. The pathogenicity study aimed to determine whether 7 Fpg isolates and a mixed inoculum differed in ability to cause crown rot in 9 wheat genotypes ranging in susceptibility to this disease. Although a genotype*inoculum interaction was significant, there is no evidence of stable pathogenic races in the isolates examined in these experiments. The growth of all isolates was partially inhibited in a consistent manner on resistant genotypes when compared to very susceptible genotypes. These results confirm significant differences in the aggressiveness of Fpg isolates on wheat, evidenced by variation in mean disease severity between isolates growing on a range of host genotypes.
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Pereira, J. L. M. "Alternative strategies for the chemical control of Phytophthora pod rot of cocoa in Bahia, Brazil". Thesis, University of Bristol, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384415.
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Ehrnhöfer, Dagmar Elisabeth. "Green tea catechins change the aggregation behavior of proteins associated with neurodegenerative disease". Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2007. http://dx.doi.org/10.18452/15624.
Texto completoResumen
Eine Gemeinsamkeit verschiedener neurodegenerativer Erkrankungen ist die abnormale Ansammlung von Proteinen im Gehirn, wie z. B. von alpha-Synuclein (Syn)-Aggregaten bei der Parkinson''schen Krankheit (PD) oder von Huntingtin (Htt)-Aggregaten bei Chorea Huntington (HD). Am Anfang dieser Studie wurde eine Bibliothek von ca. 5000 natürlichen Substanzen nach Inhibitoren der Htt-Aggregation durchsucht. Eine der wirksamen Substanzen war (-)-Epigallocatechingallat (EGCG), eine Verbindung, die in grünem und schwarzem Tee vorkommt. Die antioxidativen Eigenschaften von EGCG wurden bereits mit einer neuroprotektiven Wirkung in Verbindung gebracht, was EGCG zu einem vielversprechenden Kandidaten für die Entwicklung einer neuen Behandlungsmethode macht. Eine inhibierende Wirkung auf Proteinaggregation wurde jedoch bis jetzt noch nicht nachgewiesen. Diese Studie zeigt, dass EGCG die Aggregation von Htt und Syn hemmt, indem es dosisabhängig eine oligomere Proteinkonformation stabilisiert. Diese Oligomere wirken jedoch nicht als Keime in Aggregationsreaktionen. Zusätzlich verändert EGCG die Exposition bestimmter Epitope, die von konformationsspezifischen Antikörpern im Laufe der Aggregation erkannt werden. Daher könnte die Substanz Proteine, die zur Aggregation neigen, auf einen alternativen Faltungspfad in der Missfaltungskaskade führen. Weiterhin legen die Ergebnisse nahe, dass eine direkte Wechselwirkung zwischen EGCG und Proteinen in einer ungefalteten Konformation stattfindet. In verschiedenen Zellkultur-Modellsystemen verringerte EGCG die Toxizität, die von missgefalteten Proteinen ausgeht, was nahelegt, dass die neu geformten oligomeren Spezies nicht toxisch sind. EGCG könnte daher ein chemisches Chaperon darstellen, das die Missfaltung und Toxizität von Proteinen, die mit neurodegenerativen Krankheiten assoziiert sind, verringert. Die Substanz könnte daher die Basis zur Entwicklung einer neuen Therapie für diese unheilbaren Krankheiten darstellen.A common feature of neurodegenerative disorders is the abnormal accumulation of aggregated protein the brain, such as alpha-Synuclein (Syn) aggregates in Parkinson''s disease (PD) and Huntingtin (Htt) aggregates in Huntington''s disease (HD). In this study, a library of approximately 5000 natural compounds was screened for inhibitors of Htt aggregation. One of the hits was (-)- Epigallocatechin gallate (EGCG), a compound present in green and black tea. The antioxidant properties of this substance have been linked to neuroprotection before, making it a promising candidate for the development of a treatment for neurodegenerative diseases. Inhibition of protein aggregation by EGCG, however, has not been demonstrated so far. This study shows that EGCG inhibits the aggregation of Htt and Syn by stabilizing an oligomeric conformation of the respective proteins in a dose-dependent manner. These oligomers do not seed the aggregation of Htt and Syn. Also, EGCG modifies the exposure of different epitopes recognized by conformation-specific antibodies during the aggregation process. The compound might therefore lead aggregation-prone proteins on an alternative folding pathway in the misfolding cascade. The results furthermore suggest that direct interaction occurs between EGCG and proteins in an unfolded conformation. EGCG also reduces toxicity caused by misfolded Htt or Syn in cell culture model systems, suggesting that the oligomeric protein species formed in the presence of EGCG are not toxic to living cells. EGCG might therefore represent a chemical chaperone that can modulate misfolding and toxicity of proteins associated with neurodegenerative diseases and could provide the basis for the development of a novel pharmacotherapy for these fatal disorders.
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Cui, Xiaohui. "Regulation of biosurfactant production by quorum sensing in Pseudomonas fluorescens 5064, the cause of broccoli head rot disease". Thesis, University of Edinburgh, 2004. http://hdl.handle.net/1842/580.
Texto completoResumen
Broccoli head rot is a destructive disease found in most broccoli production areas. The main pathogen is the bacterium Pseudomonas fluorescens. P. fluorescens 5064, which was first isolated from an infected broccoli head in SE Scotland, produces biosurfactants that are important for bacterial establishment on the plant surface prior to causing disease in broccoli. Preliminary experiments performed in this study showed that biosurfactant production in P. fluorescens 5064 was cell density dependent, which is a typical characteristic of the quorum sensing mechanism. Quorum sensing is a bacterial communication mechanism, which controls a number of key processes in growth, reproduction and virulence via signalling molecules (quorum sensing signal) in many gram-negative bacteria. One aim of this study was to determine if biosurfactant production in P. fluorescens 5064 is controlled via quorum sensing. To do this, 35 surfactant-minus Tn5 mutants of P. fluorescens 5064 were screened for their abilities to produce a quorum sensing signal. Six of these biosurfactant-deficient mutants showed a large reduction in quorum sensing signal production. In one mutant 6423, which contains a single Tn5 insertion, the production of the quorum sensing signal was almost eliminated. Addition of quorum sensing signal, either synthetic or extracted from wild type P. fluorescens 5064, was able to restore biosurfactant production in mutant 6423. This strongly suggests that quorum sensing regulates biosurfactant production in P. fluorescens 5064. Attempts were made to clone and sequence the Tn5 disrupted gene in mutant 6423, but the identity of the gene remains inconclusive. The quorum sensing signal in wild type P. fluorescens 5064 was identified in this study by High Pressure Liquid Chromatography and Mass Spectrometry as N-3-hydroxyoctanoyl-homoserine lactone, which has been shown by other researchers to be present in P. fluorescens strain 2-79, but not in the strains F113, 7-14 and NCIMB 10586. The discovery that biosurfactant production in P. fluorescens 5064 is regulated by quorum sensing opens up a possibility for novel control of broccoli head rot. Although only the control of biosurfactant production by quorum sensing was examined in this study, it is possible that other virulence factors, such as pectic enzyme production, are also controlled by quorum sensing as in other pathogenic bacteria. By blocking the quorum sensing system, the pathogenic P. fluorescens that use this mechanism to control virulence could potentially be rendered avirulent. In greenhouse pathogenicity tests, a quorum sensing signal-degrading bacterium, Bacillus sp. A24, was evaluated for biocontrol of head rot disease caused by P. fluorescens 5064 on broccoli. However, the Bacillus sp. A24 showed only limited control effects, despite its strong quorum sensing signal-degrading ability towards the pathogen in vitro. A subsequent test proved that Bacillus sp. A24 is a surfactant producer itself and this could explain its ineffectiveness in disease control. When screening the quorum sensing signals of the 35 biosurfactant mutants, mutant 6418 was found to produce a potent antibiotic-like compound. This was identified by thin-layer chromatography as pyrrolnitrin. Unlike wild-type P. fluorescens 5064, mutant 6418 has lost its ability to produce virulence factors and is thus non-pathogenic. It was therefore of interest to determine if mutant 6418 could be used as a biocontrol agent to control broccoli head rot disease. In greenhouse pathogenicity tests, mutant 6418 significantly reduced disease by 41 %. The practical application of this research to bacterial disease control – via the manipulation of quorum sensing to inhibit virulence gene expression – is discussed.
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Hutchins, John David. "Antagonism of the stem rot pathogen (Sclerotina sclerotiorum) by microorganisms from oilseed rape flowers : prospects for biological control". Thesis, Imperial College London, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.281747.
Texto completo
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Matheron, Michael E. y Martin Porchas. "Evaluation of Fungicidal Management of Alternaria Fruit Rot on Citrus in 2000 and 2001 Seasons". College of Agriculture, University of Arizona (Tucson, AZ), 2003. http://hdl.handle.net/10150/198098.
Texto completoResumen
Alternaria fruit rot on Minneola tangelos and navel oranges can reach economically important levels in central Arizona. The objective of this study was to test the efficacy of a new fungicide, Headline (BAS 500), for disease management. A trial was conducted in 2000 and 2001 in a commercial Minneola tangelo grove with a history of Alternaria fruit rot. In 2000, nine trees were sprayed monthly from August to December with Headline at a rate of 0.25 lb active ingredient per acre. Another nine trees were not sprayed and served as controls. In 2001, 15 trees were sprayed monthly from November, 2001 to February, 2002 with the same rate of fungicide used in 2000. Another 15 trees were not sprayed and served as controls. Disease severity was evaluated monthly from September to February in each season by counting the number of infected fruit that had dropped from trees. No disease was evident from September through November, when fruit were green. By December the fruit had matured and turned color; additionally, Alternaria fruit rot was first observed. Low numbers of infected fruit were recorded in December and January with higher numbers of infected fruit from non-treated compared to treated trees. In February the mean number of infected fruit from trees treated with Headline and non-treated trees was 2.1 and 3.8%, respectively, in the 2000 trial and 1.9 and 4.5%, respectively, in the 2001 trial. Disease was numerically reduced in both years; however, the difference was only statistically significant in 2001. The findings of this research suggest that Headline could provide meaningful reduction in the incidence and severity of Alternaria fruit rot in Minneola tangelo groves.
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Wright, Glenn C. "Control of Brown Wood Rot in Lemons with Low Pressure Injection 2013-14". College of Agriculture, University of Arizona (Tucson, AZ), 2015. http://hdl.handle.net/10150/578401.
Texto completoResumen
6 pp.We injected AGRA PHOS (Potassium Phosphite) 0-2.4-2, Propiconizole – 0.05%, Zn, Mn and Fe 0.105, 0.112, and 0.10% respectively, Zn, Mn and Fe 0.210, 0.220, and 0.200% respectively and Propiconizole – 0.05% + Zn, Mn and Fe 0.105, 0.112, and 0.10% respectively using a low pressure injection system for the control of Antrodia sinuosa in lemon trees. No treatment led to a significant reduction in fungal growth.
30
Allay, Sanjita. "Screening of Arbuscular Mycorrhizal Fungi and Plant Growth Promoting Fungi from rhizosphere of Citrus reticulata Blanco and their assessment for management of root rot disease". Thesis, University of North Bengal, 2014. http://ir.nbu.ac.in/hdl.handle.net/123456789/955.
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MONDANI, LETIZIA. "Garlic dry rot: a comprehensive study from field to fork on casual agents and disease management". Doctoral thesis, Università Cattolica del Sacro Cuore, 2021. http://hdl.handle.net/10280/96575.
Texto completoResumen
L’aglio è coltivato a livello mondiale nelle regioni temperate, secondo la FAO nel 2016 1.5 milioni di ettari sono stati destinati a questa coltura. A partire dal 2002 Fusarium proliferatum è stato segnalato come principale agente causale del marciume secco dell’aglio in post raccolta. I sintomi sono identificabili come macchie necrotiche sui bulbilli e in presenza di forti infezioni è possibile osservare la presenza di micelio bianco. F. proliferatum è un patogeno in grado di produrre Fumonisina B1 e B2, micotossine che potrebbero accumularsi all’interno dei bulbi ed essere tossiche per il consumatore. In Italia nel 2012 il 30% del raccolto è stato perso a causa di questo patogeno. Essendo la Fusariosi una malattia emergente a livello mondiale in letteratura si trovano ancora scarse informazioni sul suo sviluppo a livello di campo e sulle strategie di contenimento.
1. Allo scopo di verificare la quantità di inoculo fungino presente nell’ambiente si è proceduto all’analisi dei suoli in presemina con specifica attenzione alla quantificazione e all’identificazione delle specie fungine presenti. A tale scopo è stata eseguita: la conta delle Unità Formanti Colonia per grammo di terreno (UFC/g) su terreni specifici per l’isolamento del genere Fusarium spp. per grammo di terreno. Le identificazioni sono state eseguite al microscopio ottico e confermate successivamente con metodi molecolari.
2. Per seguire l’avanzamento della malattia durante la stagione colturale, invece, si è proceduto al campionamento in tre fasi fenologiche (inizio formazione dei bulbilli BBCH 15, ingrossamento dei bulbilli BBCH 45, maturazione di raccolta BBCH 49) con caratterizzazione dei sintomi, isolamento e riconoscimento dei funghi associati al marciume.
3. Per verificare la correlazione tra andamento meteo e incidenza delle specie fungine associate al marciume secco, sono stati raccolti i dati di meteorologici relativi al totale delle piogge, ai gradi giorno, all’umidità relativa media e alla temperatura media nei quadrati corrispondenti alle aziende agricole oggetto di studio. I dati sono stati correlati attraverso il coefficiente di correlazione di Pearson con i valori di gravità e incidenza della malattia stimati a fine stagione colturale.
4. Per verificare l’insorgenza dalla malattia nella fase di post raccolta si è proceduto con campionamenti di bulbi in conservazione, posa in piastra di bulbilli sintomatici e asintomatici e calcolo dell’incidenza delle specie fungine associate ai sintomi del marciume.
5. Al fine di verificare la possibile presenza di fumonisine nei campioni analizzati durante la stagione colturale e nel post raccolta, si è proceduto all’analisi attraverso HPLC di estratti di aglio.
6. Per individuare possibili strategie di controllo della malattia durante la stagione colturale sono stati eseguiti test di efficacia di prodotti chimici e biologici in vitro e in campo. I prodotti chimici sono stati provati su PDA modificato inoculato centralmente con F. proliferatum, mentre per gli agenti di biocontrollo sono state allestite prove di coltura duale. La prova in campo, invece, è stata eseguita all’interno di un campo sperimentale a strip plot. L’aglio delle diverse tesi è stato conservato in cella frigorifera per 9 mesi, per valutare la persistenza dei prodotti utilizzati alla concia.
I risultati ottenuti hanno dimostrato che F. proliferatum e F. oxysporum sono le specie maggiormente associate al marciume dell’aglio durante la stagione colturale. L’andamento delle due specie è complementare e varia a seconda dell’andamento meteorologico della stagione colturale. F. proliferatum è correlato positivamente con l’aumento della temperatura e delle piogge, mentre F. oxysporum sembra prevalere nelle stagioni meno piovose ed ha mostrato correlazione positiva con la gravità dei sintomi rilevati in campo sulle corone.
La carica micotica di Fusarium nel terreno rimane costante negli anni di analisi, facendo presupporre un maggiore ruolo del seme nella trasmissione della malattia.
Per quanto riguarda il post raccolta, invece, F. proliferatum risulta la specie isolata con maggiore frequenza dai bulbilli e si correla positivamente ai sintomi rilevati sugli spicchi, confermando il suo ruolo come agente causale del marciume secco durante lo stoccaggio. F. oxysporum, invece, colonizza in prevalenza le radici e la parte basale della pianta dividendo il patosistema in due subsistemi: F. proliferatum-bulbi; F. oxysporum-radici. F. proliferatum è stato isolato anche dagli spicchi asintomatici con frequenza del 25%, ed è stato possibile rilevare la presenza di fumonisine con l’avanzare del tempo di stoccaggio in cella. Essendo il fungo presente anche sugli spicchi asintomatici maggiori studi saranno necessari per garantire la sicurezza dei consumatori. Infine, dalle prove di concia in campo è emerso che il principio attivo Tebuconazolo, riduce la comparsa dei sintomi da Fusarium, ma non in modo risolutivo. Ciononostante, una volta che il prodotto viene riportato a temperatura ambiente dopo lo stoccaggio in cella refrigerata, l’incidenza di F. proliferatum aumenta nuovamente con possibilità di sviluppo di danni al prodotto da commercializzare.Since 2002, Fusarium proliferatum has been reported as the main causal agent of garlic dry rot during the postharvest stage, but information on the development of the disease throughout the production chain was nearly absent. Dry rot has caused huge economic losses in the past few years (up to 30 % of the yield), symptoms are visible on bulbs during storage as necrotic spots and in the most severe attacks, white mycelium may become visible on cloves. Few pest management strategies were tested in the recent past, but none were satisfactory. Due to the economic effect that this pathogen can have on local productions, the thesis aimed to deeply investigate the pathosystem with a field to fork approach and to test new strategies to control fungal infections. First of all, the work focused on garlic (Allium sativum L.) cropping season, intending to clarify the role of F. proliferatum in bulb infection as well as the impact of crop growing conditions on the development of the pathogen. A 3-year study was conducted in Piacenza (northern Italy) by sampling six garlic farms with different dry rot history (three highly contaminated and three low contaminated). Soil samples were recovered at sowing time for the counting of fungal colony-forming units (CFU). Plant samples were collected at three relevant growth stages, from April to July, for which disease severity assessment and fungi isolations were performed. Fusarium was the most frequently isolated genus, and F. proliferatum and F. oxysporum the dominant species during the garlic cropping season. F. oxysporum was dominant in the first year of the study, but F. proliferatum registered the highest incidence in all the farms tested. F. oxysporum incidence was correlated with dry weather, whereas F. proliferatum was enhanced in rainy years. To conclude, F. proliferatum is confirmed to be associated with garlic bulbs, even at crop’s early growth stages and symptoms are visible mainly on roots and basal plates at the field stage, related to F. oxysporum. Then, the focus was made in detecting the presence of F. proliferatum on garlic bulbs during prolonged storage, and to identify other fungal species associated with garlic dry rot. Moreover, fumonisin contamination in symptomatic and asymptomatic cloves were detected. Samples of 100 plants were collected over three production seasons in six farms located in Northern Italy at three-time points (at harvest, processing, and 6 months storage at –4° C). Results obtained lead to think that Fusarium–garlic pathosystem is split into two parts: basal plate/root and bulb. F. proliferatum had the highest incidence in infected bulbs and was confirmed as the causal agent of postharvest dry rot in garlic (mean incidence: 35.4%). F. oxysporum co-occurred with F. proliferatum but symptoms were visible only on basal plate/root. Dry rot incidence slightly increased during cold storage (from 14.6% at processing to 18.4% at 6-month storage); although, F. proliferatum incidence was stable during cold storage, fumonisin were produced from harvest through storage. Cloves showing symptoms were more contaminated compared to those asymptomatic, both by the fungus (mean incidence 39% vs 25.3%) and the toxin (287.0 vs 24.4 µg kg-1). Therefore, cold storage limits garlic dry rot, but health concerns related to fumonisin should be seriously considered. Regarding disease management, garlic crop is commonly propagated by plant parts (cloves). To protect garlic crop from early growth stages it is important to find commercial products able to control the pathogen growth on seedlings. The experiment aimed to test in vitro and in vivo the efficacy of triazoles and biocontrol agents (BCAs) against F. proliferatum and F. oxysporum. In in vitro trials, the best performance was achieved by propiconazole+prochloraz (100%), followed by tebuconazole (88.9%). BCAs were less effective but still showed great capacity to control the pathogen with maximum growth inhibition of 80% (Trichoderma harzianum +T. gamsii). In both cases, temperature influenced the capacity to control the pathogen with minimum effect at 25°C compared to lower temperatures. In vivo bacterial BCAs showed a similar capacity to control Fusaria compared to chemical products (mean of severity index 18.6% and 11.7%, respectively) and did not show side effects on root length. In vitro and in vivo results are comparable, except for Trichoderma, with the worst performances in terms of disease severity on plants. Finally, a field trial was designed to verify the efficacy of chemical and biological active ingredients as seed coating both at crop stage and postharvest, simulating the entire production chain, by taking into account visible symptoms and incidence of fungi. All products tested reduced the severity of symptoms on basal plates at the field stage, but none of them was able to reduce Fusarium incidence. A postharvest analysis conducted on bulbs demonstrated the efficacy of Tebuconazole, B. subtilis, and Trichoderma+B. subtilis in reducing the number of cloves showing symptoms per bulb (mean 34.3% vs control 45.8%). Moreover, Tebuconazole was able to reduce the incidence of F. proliferatum by 48% with respect to untreated control. The trial highlighted also that the incidence of F. proliferatum increased by 37% when garlic bulbs were kept for 15 days at room temperature simulating storage at consumers houses. Results obtained in the trial are promising and seed coating had a positive effect on garlic dry rot postharvest; although further studies are needed to test the persistence of seed coating treatments after prolonged storage period, especially when the product is kept outside cold chambers.
32
MONDANI, LETIZIA. "Garlic dry rot: a comprehensive study from field to fork on casual agents and disease management". Doctoral thesis, Università Cattolica del Sacro Cuore, 2021. http://hdl.handle.net/10280/96575.
Texto completoResumen
L’aglio è coltivato a livello mondiale nelle regioni temperate, secondo la FAO nel 2016 1.5 milioni di ettari sono stati destinati a questa coltura. A partire dal 2002 Fusarium proliferatum è stato segnalato come principale agente causale del marciume secco dell’aglio in post raccolta. I sintomi sono identificabili come macchie necrotiche sui bulbilli e in presenza di forti infezioni è possibile osservare la presenza di micelio bianco. F. proliferatum è un patogeno in grado di produrre Fumonisina B1 e B2, micotossine che potrebbero accumularsi all’interno dei bulbi ed essere tossiche per il consumatore. In Italia nel 2012 il 30% del raccolto è stato perso a causa di questo patogeno. Essendo la Fusariosi una malattia emergente a livello mondiale in letteratura si trovano ancora scarse informazioni sul suo sviluppo a livello di campo e sulle strategie di contenimento.
1. Allo scopo di verificare la quantità di inoculo fungino presente nell’ambiente si è proceduto all’analisi dei suoli in presemina con specifica attenzione alla quantificazione e all’identificazione delle specie fungine presenti. A tale scopo è stata eseguita: la conta delle Unità Formanti Colonia per grammo di terreno (UFC/g) su terreni specifici per l’isolamento del genere Fusarium spp. per grammo di terreno. Le identificazioni sono state eseguite al microscopio ottico e confermate successivamente con metodi molecolari.
2. Per seguire l’avanzamento della malattia durante la stagione colturale, invece, si è proceduto al campionamento in tre fasi fenologiche (inizio formazione dei bulbilli BBCH 15, ingrossamento dei bulbilli BBCH 45, maturazione di raccolta BBCH 49) con caratterizzazione dei sintomi, isolamento e riconoscimento dei funghi associati al marciume.
3. Per verificare la correlazione tra andamento meteo e incidenza delle specie fungine associate al marciume secco, sono stati raccolti i dati di meteorologici relativi al totale delle piogge, ai gradi giorno, all’umidità relativa media e alla temperatura media nei quadrati corrispondenti alle aziende agricole oggetto di studio. I dati sono stati correlati attraverso il coefficiente di correlazione di Pearson con i valori di gravità e incidenza della malattia stimati a fine stagione colturale.
4. Per verificare l’insorgenza dalla malattia nella fase di post raccolta si è proceduto con campionamenti di bulbi in conservazione, posa in piastra di bulbilli sintomatici e asintomatici e calcolo dell’incidenza delle specie fungine associate ai sintomi del marciume.
5. Al fine di verificare la possibile presenza di fumonisine nei campioni analizzati durante la stagione colturale e nel post raccolta, si è proceduto all’analisi attraverso HPLC di estratti di aglio.
6. Per individuare possibili strategie di controllo della malattia durante la stagione colturale sono stati eseguiti test di efficacia di prodotti chimici e biologici in vitro e in campo. I prodotti chimici sono stati provati su PDA modificato inoculato centralmente con F. proliferatum, mentre per gli agenti di biocontrollo sono state allestite prove di coltura duale. La prova in campo, invece, è stata eseguita all’interno di un campo sperimentale a strip plot. L’aglio delle diverse tesi è stato conservato in cella frigorifera per 9 mesi, per valutare la persistenza dei prodotti utilizzati alla concia.
I risultati ottenuti hanno dimostrato che F. proliferatum e F. oxysporum sono le specie maggiormente associate al marciume dell’aglio durante la stagione colturale. L’andamento delle due specie è complementare e varia a seconda dell’andamento meteorologico della stagione colturale. F. proliferatum è correlato positivamente con l’aumento della temperatura e delle piogge, mentre F. oxysporum sembra prevalere nelle stagioni meno piovose ed ha mostrato correlazione positiva con la gravità dei sintomi rilevati in campo sulle corone.
La carica micotica di Fusarium nel terreno rimane costante negli anni di analisi, facendo presupporre un maggiore ruolo del seme nella trasmissione della malattia.
Per quanto riguarda il post raccolta, invece, F. proliferatum risulta la specie isolata con maggiore frequenza dai bulbilli e si correla positivamente ai sintomi rilevati sugli spicchi, confermando il suo ruolo come agente causale del marciume secco durante lo stoccaggio. F. oxysporum, invece, colonizza in prevalenza le radici e la parte basale della pianta dividendo il patosistema in due subsistemi: F. proliferatum-bulbi; F. oxysporum-radici. F. proliferatum è stato isolato anche dagli spicchi asintomatici con frequenza del 25%, ed è stato possibile rilevare la presenza di fumonisine con l’avanzare del tempo di stoccaggio in cella. Essendo il fungo presente anche sugli spicchi asintomatici maggiori studi saranno necessari per garantire la sicurezza dei consumatori. Infine, dalle prove di concia in campo è emerso che il principio attivo Tebuconazolo, riduce la comparsa dei sintomi da Fusarium, ma non in modo risolutivo. Ciononostante, una volta che il prodotto viene riportato a temperatura ambiente dopo lo stoccaggio in cella refrigerata, l’incidenza di F. proliferatum aumenta nuovamente con possibilità di sviluppo di danni al prodotto da commercializzare.Since 2002, Fusarium proliferatum has been reported as the main causal agent of garlic dry rot during the postharvest stage, but information on the development of the disease throughout the production chain was nearly absent. Dry rot has caused huge economic losses in the past few years (up to 30 % of the yield), symptoms are visible on bulbs during storage as necrotic spots and in the most severe attacks, white mycelium may become visible on cloves. Few pest management strategies were tested in the recent past, but none were satisfactory. Due to the economic effect that this pathogen can have on local productions, the thesis aimed to deeply investigate the pathosystem with a field to fork approach and to test new strategies to control fungal infections. First of all, the work focused on garlic (Allium sativum L.) cropping season, intending to clarify the role of F. proliferatum in bulb infection as well as the impact of crop growing conditions on the development of the pathogen. A 3-year study was conducted in Piacenza (northern Italy) by sampling six garlic farms with different dry rot history (three highly contaminated and three low contaminated). Soil samples were recovered at sowing time for the counting of fungal colony-forming units (CFU). Plant samples were collected at three relevant growth stages, from April to July, for which disease severity assessment and fungi isolations were performed. Fusarium was the most frequently isolated genus, and F. proliferatum and F. oxysporum the dominant species during the garlic cropping season. F. oxysporum was dominant in the first year of the study, but F. proliferatum registered the highest incidence in all the farms tested. F. oxysporum incidence was correlated with dry weather, whereas F. proliferatum was enhanced in rainy years. To conclude, F. proliferatum is confirmed to be associated with garlic bulbs, even at crop’s early growth stages and symptoms are visible mainly on roots and basal plates at the field stage, related to F. oxysporum. Then, the focus was made in detecting the presence of F. proliferatum on garlic bulbs during prolonged storage, and to identify other fungal species associated with garlic dry rot. Moreover, fumonisin contamination in symptomatic and asymptomatic cloves were detected. Samples of 100 plants were collected over three production seasons in six farms located in Northern Italy at three-time points (at harvest, processing, and 6 months storage at –4° C). Results obtained lead to think that Fusarium–garlic pathosystem is split into two parts: basal plate/root and bulb. F. proliferatum had the highest incidence in infected bulbs and was confirmed as the causal agent of postharvest dry rot in garlic (mean incidence: 35.4%). F. oxysporum co-occurred with F. proliferatum but symptoms were visible only on basal plate/root. Dry rot incidence slightly increased during cold storage (from 14.6% at processing to 18.4% at 6-month storage); although, F. proliferatum incidence was stable during cold storage, fumonisin were produced from harvest through storage. Cloves showing symptoms were more contaminated compared to those asymptomatic, both by the fungus (mean incidence 39% vs 25.3%) and the toxin (287.0 vs 24.4 µg kg-1). Therefore, cold storage limits garlic dry rot, but health concerns related to fumonisin should be seriously considered. Regarding disease management, garlic crop is commonly propagated by plant parts (cloves). To protect garlic crop from early growth stages it is important to find commercial products able to control the pathogen growth on seedlings. The experiment aimed to test in vitro and in vivo the efficacy of triazoles and biocontrol agents (BCAs) against F. proliferatum and F. oxysporum. In in vitro trials, the best performance was achieved by propiconazole+prochloraz (100%), followed by tebuconazole (88.9%). BCAs were less effective but still showed great capacity to control the pathogen with maximum growth inhibition of 80% (Trichoderma harzianum +T. gamsii). In both cases, temperature influenced the capacity to control the pathogen with minimum effect at 25°C compared to lower temperatures. In vivo bacterial BCAs showed a similar capacity to control Fusaria compared to chemical products (mean of severity index 18.6% and 11.7%, respectively) and did not show side effects on root length. In vitro and in vivo results are comparable, except for Trichoderma, with the worst performances in terms of disease severity on plants. Finally, a field trial was designed to verify the efficacy of chemical and biological active ingredients as seed coating both at crop stage and postharvest, simulating the entire production chain, by taking into account visible symptoms and incidence of fungi. All products tested reduced the severity of symptoms on basal plates at the field stage, but none of them was able to reduce Fusarium incidence. A postharvest analysis conducted on bulbs demonstrated the efficacy of Tebuconazole, B. subtilis, and Trichoderma+B. subtilis in reducing the number of cloves showing symptoms per bulb (mean 34.3% vs control 45.8%). Moreover, Tebuconazole was able to reduce the incidence of F. proliferatum by 48% with respect to untreated control. The trial highlighted also that the incidence of F. proliferatum increased by 37% when garlic bulbs were kept for 15 days at room temperature simulating storage at consumers houses. Results obtained in the trial are promising and seed coating had a positive effect on garlic dry rot postharvest; although further studies are needed to test the persistence of seed coating treatments after prolonged storage period, especially when the product is kept outside cold chambers.
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Timney, David. "The role of the physical properties of fungicides in controlling root rot in tomatoes caused by Phytophthora capsici Leonian". Thesis, University of Reading, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239555.
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Samils, Nicklas. "Monitoring the control methods of Heterobasidion annosum s.l. root rot /". Uppsala : Department of Forest Mycology and Pathology, Swedish University of Agricultural Sciences, 2008. http://epsilon.slu.se/200847.pdf.
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Bovill, Jessica. "Mapping spot blotch & common root rot (causal agent: bipolaris sorokiniana) resistance genes in barley". University of Southern Queensland, Faculty of Sciences, 2008. http://eprints.usq.edu.au/archive/00006178/.
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The fungal pathogen Bipolaris sorokiniana (teleomorph Cochliobolus sativus)causes the foliar disease spot blotch (SB) and the root disease common root rot (CRR). Spot blotch and CRR are serious disease constraints to barley production in warmer growing regions of the world, with estimated yield losses ranging from 30-70% from SB and 15-30% for CRR. Although chemical treatments may assist incontrolling spot blotch infections, the most effective and environmentally sound means of control for each disease is breeding for varieties with natural resistance. InAustralia, no commercially available varieties offer resistance to either SB or CRR. This study has sought to establish molecular markers that will be useful for selecting for resistance to each of these important fungal diseases.Barley cultivars derived from the breeding line NDB112 have provided durable SB resistance in the North Dakota region of the USA for over 40 years. The robustnessof this resistance had not been determined under Australian environmental conditions or with those B. sorokiniana pathotypes present within Australia. Toelucidate the genetics of resistance, two seedling and two field trials were conducted on an ND11231-12/VB9524 (ND/VB) doubled haploid (DH) population (180 lines).A molecular map of the ND/VB population was curated in order to provide a firm basis for mapping of resistance loci. Composite interval mapping revealed thatdifferent gene combinations are effective at different stages of plant development. Seedling resistance was found to be conditioned by a major locus on the short arm ofchromosome 7H and this region was validated in the related population ND11231-11/WI2875*17. A minor quantitative locus on chromosome 5HS was detected in one of the two seedling trials. However, this region requires further investigation to confirm its association to SB resistance in this population. Field resistance to SB in adult plants was found to be associated with two major quantitative trait loci (QTL)on chromosomes 7HS and 3HS; and a putative third minor QTL on chromosome 2HS. The 7H region is common between seedling and field resistance and is the most important locus for the expression of resistance at both stages of plant development. These findings largely concur with genetic studies of this trait in tworowed barley germplasm in North American environments.Common root rot is a difficult disease to phenotype for, and breeding programs will benefit from the identification of molecular markers linked to resistance. Data wasprovided from field trials of subsets of the population over four years. Using a novel approach combining the efficiency of bulked-segregant analysis with highthroughputDiversity Arrays Technology markers (BSA-DArT), CRR resistance was found to be conditioned by three putative QTL in an unmapped Delta/Lindwall population. QTL were identified on chromosomes 2HS, 4HS, and 7HS. To validatethe trait-linkage associations between the DArT markers and the CRR QTL,microsatellite (SSR) markers known to map to the regions identified by BSA-DArT were used. The 2H and 4H regions were validated using marker regression of the SSR markers in most seedling trials, whereas the 7H QTL, which is proximal to the location of the SB resistance QTL in the ND/VB population, was detected in only one seedling trial.The QTL identified in this study offer potential to combat the foliar and root diseases causes by this fungal pathogen. The chromosomal location of QTL for SB and CRR resistance have been found to differ in the ND/VB and D/L populations,which suggests that resistance to each disease is independently inherited. Further research is required to confirm the hypothesis that it is possible to combineresistance to both diseases into a single genotype. Such allelic combinations would provide elite germplasm that would benefit barley breeding programs world-wide.
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Parker, Monica. "Fusarium root and stem rot of greenhouse cucumbers in British Columbia, host range, epidemiology and disease control". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ51443.pdf.
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Jeannotte, Richard. "Fatty acid biomarker analysis to characterize soil microbial communities in soybean agroecosystems with Sclerotinia stem rot disease". Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=102988.
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Soybean (Glycine max (L.) Merr.) is one the major crops produced worldwide. However, soybean is susceptible to many diseases. Sclerotinia stem rot (SSR) disease caused by Sclerotinia sclerotiorum (Lib.) de Bary is considered one of the most important fungal diseases of soybean. It can be controlled by chemicals (e.g. fungicides), by breeding cultivars with disease resistance and by cultural control (e.g. increasing the width between rows, reducing plant populations). A promising and complementary method of controlling SSR disease in the field is the application of biological control agents. Biological control agents introduced in a soil environment will interact with other soil food web organisms, as do the pathogenic organism and infected plants, which may change the genetic and functional diversity in soil microbial communities. Profiling these changes may lead to an improved understanding of the interactions between these players (biological control agents, pathogens, soil biota and plants) in the biological control phenomenom, permiting us to exploit naturally-occurring ecological relationships and develop more sustainable approaches to control soybean diseases. Fatty acid biomarkers analysis was used to profile microbial communities in soils. Two laboratory studies were conducted to evaluate the methods used for extraction and profiling the fatty acid biomarkers from soil samples with a range of soil properties (clay content, organic matter content), The first study investigated the best solvent mixture for recovering fatty acid biomarkers from soil using an automated pressurized solvent extraction (PSE) system. Solvent mixtures containing chloroform and methanol were more efficient at extracting fatty acids from agricultural soils than hexane:2-propanol and acetone. The second study presented an exploratory pyrolysis-mass spectrometry technique to rapidly fingerprint soil lipids extracted from different agroecosystems. Pyrolysis-mass spectrometry discriminated among soils and crop production systems in the same way as the fatty acid profiling. I also report on the efficicacy of biological control agents to control Sclerotinia stem rot disease in soybean. A two-year study was conducted in soybean fields under conventional or no tillage to determine whether Trichoderma virens (SoilGard(TM)) and arbuscular mycorrhizal fungi (a mixture of Glomus intraradices and G. mosseae ), used alone or in combination, could reduce sclerotinia stem rot (SSR) disease incidence. Generally, SSR disease indicators, as well as the soybean yield, were not affected significantly by the biological control treatments. I then studied whether changes in microbial community composition were related to the inoculation of the biological control agents and the disease incidence in soybean fields. Inoculation of biological control agents changes the expression of many soil fatty acids during both years of the trial. Also, in the plots with severely diseased plants, fatty acids biomarkers of gram positive and actinomycetes bacteria were significantly greater than in plots with healthy plants. I conclude that further improvement in laboratory techniques and procedures will permit researchers to efficiently extract and characterize soil lipids, providing new insight into soil organic matter dynamics and soil microbial ecology. Further study will be needed to verify the efficacy and optimize the application method, dose and timing of biocontrol agents to provide protection against SSR disease in soybean fields.
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Nourian, Farideh. "Quality changes in raw and processed potatoes as influenced by storage conditions and bacterial soft rot disease". Thesis, McGill University, 2002. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=83083.
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Potato ranks fourth after wheat, rice and corn as a major food crop. It is an excellent source of nutrients and at the same time relatively inexpensive, therefore it is the mainstay in the diets of people in both developed and developing countries. Potato losses and quality degradation due to the effect of storage variables or processing conditions must be reduced to increase the world food supply. To accomplish these objectives, studies have been conducted to evaluate: (a) quality changes in potatoes during cooking and frying, (b) quality changes in raw potatoes as influenced by storage conditions, (c) changes in cooking quality of potatoes as influence by storage conditions, (d) changes in frying quality of potatoes as influenced by storage conditions, and finally (e) quality changes in potatoes as influenced by Erwinia carotovora ssp. carotovora infection (Ecc, casual agent of soft rot disease in potato).Kinetics of quality changes during cooking and frying of potatoes were evaluated. Potatoes were cooked at 80--100°C or fried at 160--190°C for selected times and their texture and color were evaluated. Results showed that texture values of cooked potatoes decreased with the progress of cooking, and the rate of texture changes at each temperature was found to be consistent with two pseudo first-order kinetic mechanisms. Textural values of fried potatoes increased with frying time and followed a first order kinetic model. Cooked potatoes were less bright, more red and less yellow in color as compared to raw samples. A modified first order model was used to characterize the color changes kinetics of both cooked and fried potatoes based on the changes occurring between the initial and a maximum or minimum value. 10 min cooking at 100°C and 10 min frying at 180°C were considered to give the designed cooked and fried products, respectively.
The changes in quality characteristics of potatoes as a function of storage variables (temperature and time) were evaluated. Potatoes were stored at five temperatures (4, 8, 12, 16 and 20°C) for selected duration (at least 5 time intervals) and different physico-chemical quality parameters were evaluated. Potatoes remained healthier when they stored at lower temperatures due to absence of sprouts and visible spoilage. They became softer and darker by passage of time.
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Fiedler, Kathryn. "Integrated Approach to Understanding Tomato Sour Rot and Improving Disease Management on the Eastern Shore of Virginia". Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/49117.
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Sour rot of tomatoes, caused by Geotrichum candidum, occurs in the field and postharvest settings regularly, although postharvest losses are severe only in some years on the Eastern Shore of Virginia (ESV) and other tomato production regions. Fungicide products and cultural control methods are tested for efficacy utilizing a traditional wounding technique that does not properly reflect natural sour rot infections. A new inoculation technique was optimized for G. candidum using negative pressure to infiltrate the tomato stem scar with pathogenic spores. This new method creates consistently high rates of infection and more successfully creates infections in mature green and breaker fruit. The population of G. candidum on the Eastern Shore of VA (ESV) was characterized using multilocus sequencing technique. The resulting phylogenetic tree defines four distinct groups, including two with uncommon loci that distinguish them from the majority of the population. Thirty-seven G. candidum isolates were inoculated to media amended with ten fungicides and antimicrobial compounds commonly used in tomato production and postharvest treatments. Propiconazole and tebuconazole completely inhibited growth of all colonies. Cultivar trials were conducted to determine if resistance or tolerance to G. candidum occurs. Ten commonly grown round and Roma cultivars on the ESV were similarly susceptible to G. candidum, even at low inoculum levels. Field and postharvest surveys of sour rot on tomato fruit attempted to correlate disease incidence with weather conditions in order to better understand the cause of sporadic infection. Few patterns were seen consistently throughout harvest periods and years. Rainfall was positively correlated with disease 2-3 days before surveys and temperature was negatively correlated with disease 5-7 days before surveys. No in-field weather conditions were correlated with postharvest disease incidence. Greenhouse trials were conducted to assess the influence of water congested tomato fruit on susceptibility to sour rot. Tomato plants were exposed to water inundation to mimic rainfall and varying levels of irrigation, both in order to congest tomato fruit. Though water congestion was achieved, tomato fruit were equally susceptible to sour rot infections.Ph. D.
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Datta, Shraboni. "Studies on the Biology of Brown blight disease of Tea, Camellia sinences(L.) O, Kuntze with special reference to the factors effecting its in incidence". Thesis, University of North Bengal, 2000. http://hdl.handle.net/123456789/891.
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El, Masry Mousa Ahmed. "Biological and chemical control of Pythium butleri on tomato". Thesis, University of London, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.265901.
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Rana, Sanjay. "Studies on the resistance of camellia sinensis(L) O Kuntze to corticium theae Bernard causing black rot disease". Thesis, University of North Bengal, 2002. http://hdl.handle.net/123456789/1072.
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Krsikapa, Nenad. "Variation for resistance to Fusarium graminearum ear rot in selfed families from the corn population Zapalote Chico". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape16/PQDD_0021/MQ37137.pdf.
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Pooranampillai, Christina D. "Evaluation of resistance to Sclerotinia crown and stem rot caused by Sclerotinia trifoliorum in selected alfalfa cultivars". Thesis, Virginia Tech, 1988. http://hdl.handle.net/10919/43273.
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Sclerotinia crown and stem rot (SCSR) incited by Sclerotinia trifoliorum Eriks. causes severe losses in some fall-seeded, no-tillage plantings of alfalfa (Medicago sativa IL.) in Virginia. A mycelial plug inoculation technique was used to detect differences between cultivar (cv) responses of two alfalfa cvs, Arc and Vertus, under greenhouse conditions. A six dia plug from the margin of a 5-day-old culture of S. trifoliorum was placed near the crown area of a plant and incubated for a pre-determined period in a dew chamber at 18 C and 100% RH. Differences in isolate virulence were detected; cv Vertus was less susceptible than Arc to the less virulent isolates while the more virulent isolate (TAL 4) was equally severe on both. An incubation period of 96 hr produced significantly higher disease severity than 72, 48 or 24 hr, however, cv differentiation was best after 72 hr. Eight-, and nine-week-old plants were found to be most suitable for cv evaluation tests since younger seedlings were severely damaged and more mature plants did not develop sufficient symptom expression. Evaluation of twelve cvs with the virulent isolate (TAL 4) and the less virulent isolate (LAL 3) after 96 hr incubation produced significant differences between the mean disease severity ratings (MDSRs). Disease severity increased up to 20 days and then stabilized. Cultivar Anstar followed by WL 320, Vertus and Saranac AR were less susceptible in a majority of the tests; Endure and Euver performed well in some tests while Pioneer Brand 526 and Raidor performed poorly in all tests. This inoculation technique may act as the primary step in the selection of disease resistant germplasm for propagation, re-evaluation, and mass selection before field testing.Master of Science
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Lygis, Vaidotas. "Root rot in north-temperate forest stands : biology, management and communities of associated fungi /". Uppsala : Department of Forest Mycology and Pathology, Swedish University of Agricultural Sciences, 2005. http://epsilon.slu.se/200504.pdf.
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Hidayah, Baiq Nurul. "Sclerotinia stem rot disease on canola in Western Australia: Understanding of the pathogen and exploring biological control agents". Thesis, Hidayah, Baiq Nurul (2017) Sclerotinia stem rot disease on canola in Western Australia: Understanding of the pathogen and exploring biological control agents. PhD thesis, Murdoch University, 2017. https://researchrepository.murdoch.edu.au/id/eprint/40955/.
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Sclerotinia sclerotiorum (Lib.) de Bary is fungal pathogen that attacks over 400 plant species worldwide, causing Sclerotinia stem rot (SSR), an important disease in canola (Brassica napus L.). In Australia, SSR disease is one of the major soil-borne diseases in the canola industry. Furthermore, SSR has emerged as a serious problem on canola production in Western Australia (WA) over the past few years where crop losses can be up to 40% in the worst affected crops. Current management of Sclerotinia disease mostly relies on cultural and chemical control options that often only provide partial and/or sporadic control and can be cost prohibitive. Biological control is one of the alternatives to control soil-borne fungal diseases on brassica and there is an increased interest in biological control encouraged by public awareness about issues related to the use of chemical pesticides and biological control will likely become more important in agricultural systems in the future.
The research in this thesis addresses major gaps in knowledge on S. sclerotiorum on canola in WA through examination of the biological characterization of WA isolates of S. sclerotiorum, their pathogenicity on canola, and the possibility of applying biological control in the field. The research involves plant and soil sampling to collect isolates of the pathogen and potential local Biological Control Agents (BCAs); laboratory, glasshouse and field experiments to identify biological characteristics and pathogenicity of S. sclerotiorum and to test the effectiveness of potential local BCAs.
One hundred and forty isolates of S. sclerotiorum were collected from WA canola growing areas between 2009 and 2014. Isolate growth on PDAA (Potato Dextrose Agar + Aureomycin) medium at 24 and 48-hours showed highly significant (P≤0.001) differences between isolates. The number of sclerotia produced by isolates over 14 days in-vitro varied from 0 to 50 sclerotia per colony with highly significant differences between isolates (P≤0.001). More than 25 isolates (17.9%) formed an average of 20 sclerotia while 15 isolates (10.7%) did not form sclerotia and only one isolate (0.7%) formed 50 sclerotia. The general colour of the mycelia of the WA isolates of S. sclerotiorum was white but variation was observed from white to grey.
Pathogenicity on 10 day-old canola seedlings varied among isolates, both after 48 hours incubation in a misting chamber and after another 48 hours in a growth room. Pathogenicity of fungal pathogens is one of the indi-cators used to determine variability among isolates. S. sclerotiorum has a wide host range and many studies have shown that it is differentiated in pathogenicity. Results of mycelial agar plug inoculations on 10-day old seed-lings indicated that there was variation in pathogenicity among the isolates of S. sclerotiorum from WA and these were categorized as having low, medium or high level of pathogenicity. There were highly significant differences (P≤0.001) in seedling mortality among isolates at 48 hours after incubation in a misting chamber. In addition, there were highly significant differences (P≤0.001) in seedling mortality at 48 hours after being placed into a growth room. At 48 hours after incubation in the misting chamber, only 5 isolates of S. sclerotiorum caused 100% seedling mortality, while 26 isolates caused 0% mortality. The highest frequency of seedling mortality was 10% caused by 44 isolates. Pathogenicity was further investigated after seedlings were returned to the growth room for another 48 hours. Here 33 isolates caused 100% seedling mortality.
Research on variability of fungal pathogens has been conducted for many species, including S. sclerotiorum, all over the world. One of the conventional methods used is Mycelial Compatibility Groups (MCGs). Mycelial compatibility is an indirect measure of genetic diversity in fungal populations, and can show the degree of relatedness between or within MCGs. A total of 31 WA isolates of S. sclerotiorum, representative of a range of pathogenicity levels, were chosen for MCG tests. The 31 isolates were classified into 9 my-celial compatibility groups.
Fifteen potential fungal biological control agents (F-BCAs) and three potential bacterial biological control agents (B-BCAs) were isolated from canola growing regions in WA. The potential F-BCAs were grown in Petri dishes on PDAA. Mycelial colour showed wide variation, from dark green to white. Radial mycelial growth at 24 and 48 hours differed (P≤0.001) be-tween isolates. At 24 and 48 hours after incubation, isolate F-BCA9 had the highest radial mycelial growth rate with a diameter of 3.2 and 8.5 cm, re-spectively. All potential F-BCA isolates showed some capacity to inhibit the radial mycelial growth of S. sclerotiorum as well as reduce the number of sclerotia formed by the pathogen in dual culture tests in Petri dishes. There were significant differences (P≤0.001) in the magnitude of inhibition of radial mycelial growth (40 – 60%) and sclerotial formation (65 - 100% inhibition).
Isolates F-BCA12 and F-BCA15 totally inhibited the formation of sclerotia by the pathogen. Colonization of sclerotia in soil indicated that sclerotia were colonized by the spores of each F-BCA and therefore all sclerotia in the presence of F-BCAs could not form any new sclerotia in Petri dishes.
The colony colour of the 3 potential B-BCAs ranged from yellow to whitish yellow. Isolate B-BCA3 had the fastest colony growth rate. There was no significant difference among the potential B-BCAs in their ability to inhibit radial mycelial growth (57 - 59%) of the pathogen (P=0.934>0.05) or for-mation of sclerotia (89 - 95%) (P=0.079>0.05).
Using Sanger Sequencing molecular tools (ITS regions), the F-BCAs were identified as Trichoderma atroviride (four isolates), T. gamsii (three iso-lates), T. koningiopsis (two isolates), T. longibrachiatum (two isolates), T. paraviridescens (two isolates), T. pseudokoningii (one isolate), and T. viri-descens (one isolate). Identification of B-BCAs through 16S rRNA sequencing revealed that B-BCA1 and B-BCA2 were Serratia proteamaculans while BCA3 was Ochrobactrum anthropi.
Three field experiments were undertaken with canola to evaluate effi-cacy of BCAs. Experiment 1, conducted in 2014 was established as a Randomized Complete Block Design. However, no SSR disease symptoms were observed and there were no significant (P=0.2744>0.05) yield differ-ences between treatments at harvest.
In field experiment 2 undertaken in 2015, a Randomized Complete Factorial Design (RCFD) was used consisting of 16 treatments with pseudo- replication inside the treatment due to limited space. Because of pseudo-replication, Restricted Maximum Likelihood (REML) analysis was used to evaluate treatments effects. There were differences (P<0.001) among the BCAs in controlling SSR disease and there was an interaction (P<0.001) be-tween BCAs and the flowering stage of pathogen application. Protein and oil contents of canola seed harvested were analysed and there was a significant effect on the protein content between treatments due to the application of BCAs during the green bud phase (P=0.022<0.05) and also on the applica-tion of the pathogen during different flowering times (P=0.019<0.05). In ad-dition, there were significant differences in oil content between the treat-ments from the application of BCAs (P=0.030<0.05), but there was no signif-icant difference in oil content between treatments on the application of path-ogen at different flowering stages (P=0.051>0.05). The protein content of the untreated control treatement was significantly higher compared to the BCA treatments, but for oil content it was significantly lower compared to the other treatments. The best BCA for grain oil content in experiment 2 was B-BCA1.
In the second experiment undertaken in 2015, the RCFD consisted of fifteen treatments with pseudo-replication inside the treatments. Clear symp-toms of SSR disease were apparent when the canola crop was sprayed with S. sclerotiorum. The REML analysis revealed significant effects among the BCAs (P<0.001), and time of application of the pathogen (P<0.001), but time of fungicide application was not significant (P=0.901>0.001). There were also differences between time of BCA application (P<0.001), but no significant difference (P=0.382>0.001) between interation of BCAs and time of spraying the pathogen. Moreover, protein and oil contents based on dif-ferent flowering stage of BCA application showed that seed protein content, when the application of BCAs was made at 50% flowering stage, was signifi-cantly higher compared to application of BCAs at 30% and 10% flowering stages. The seed oil content was lowest when the BCAs were applied at 50% flowering. There were no significant differences in seed protein content be-tween the treatments (P=0.854>0.05), spraying time (P=0.850>0.05), and flowering stage (P=0.828>0.05). Furthermore, there were no significant dif-ferences in oil content between treatments (P=0.855>0.05), timing of BCA application (P=0.624>0.05) and flowering time (P=0.694>0.05).
The flowering trial was undertaken to observe after how many days newly formed flowers drop their petals. Data for petal dynamics at first flow-ering, at first petal drop, and at end of flowering, in the field and glasshouse showed that first flower opening occurred in the glasshouse at 74 days after sowing (DAS), while in field plots the first flower opening occurred 2 days later. First petal drop in the glasshouse was at 78 DAS while in the field plots first petal drop was at 79 DAS. Furthermore, flowering finished in the glasshouse on 109 DAS, but in the field plots flowering finished 107 DAS. However, there was no significant difference in timing of petal dynamics be-tween glasshouse and field studies where the mean flowering period in the glasshouse was 35 days and in the field was 32 days.
The results from these preliminary experiments indicate that local WA BCAs have some ability to control SSR disease in the field, however multiple trials in grower’s fields are needed in order to observe the stability of the BCAs and maintenance of their virulence against the pathogen. Further investigation is needed to determine other mechanisms of bio-control such as antibiosis and myco-parasitism as well as improving formulations and delivery systems. Untimately, biological control products should be as effec-tive as pesticides, economical, easy to use, non-toxic, environmentally safe and acceptable to regulatory agencies, growers and consumers.
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MUSTAFA, MAJID HASSAN MUSTAFA. "BROWN ROT DISEASE DEVELOPMENT IN PEACH(P. PERSICA L. BATSCH): FROM FUNGAL BIOLOGY TO HIGH-THROUGHPUT ON-FIELDPHENOTYPING". Doctoral thesis, Università degli Studi di Milano, 2022. http://hdl.handle.net/2434/924066.
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Brown rot (BR) disease, caused by Monilinia spp., causes significant pre-and post-harvest losses in stone fruit production, especially in humid and warm temperatures. In this thesis, we tried to tackle the subject with three complementary approaches. First, the recent progress in BR resistance in peach fruit was reviewed. Then we highlighted best practices in phenotyping BR susceptibility/resistance procedures in field and in vitro. We concluded that the main factors contributing to disease development are Monilinia inocula availability, environmental conditions, cultivars, fruit stage and management practices.
Secondly, we investigated the anti-fungal effect of some phenolics such as chlorogenic and ferulic acids and triterpenoids such as oleanolic, betulinic, and ursolic acids. Furthermore, fruit surface compound (FSC) extracts of peach fruit at two developmental stages on Monilinia fructicola and M. laxa characteristics during in vitro growth were studied. A new procedure for assaying anti-fungal activity of triterpenoids, which are notoriously difficult to assess in vitro because of their hydrophobicity, has been developed. Also, a follow-up of this study revealed that certain phenolics and triterpenoids showed modest anti-fungal activity while dramatically modulating M. fructicola gene expression. MfRGAE1 gene was overexpressed by chlorogenic and ferulic acids and MfCUT1 by betulinic acid at 4- and 7-days post-inoculation.
The third objective was to investigate the genetic background responsible for disease resistance in peach by detecting Quantitative Trait Loci (QTL) and attempts to identify molecular markers for assisted selection (MAS) in peach. For this, three F2 progenies, derived from three selfied F1 selections obtained from "Contender" (C, resistant) × "Elegant Lady" (El, susceptible), were investigated for two seasons (2019 and 2021). The whole progeny was genotyped by Single-Primer Enriched Technology (SPET) and a recently developed 18K SNP array. The genome-wide QTL analysis showed intriguing areas relevant to disease resistance, mainly the QTLs on chromosomes 2 and 4, which may be candidates for future MAS applications. Several new QTLs were detected for other fruit quality traits, including maturity date, soluble solid content and fruit weight.
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Twengström, Eva. "Epidemiology and forecasting of Sclerotinia stem rot on spring sown oilseed rape in Sweden /". Uppsala : Swedish Univ. of Agricultural Sciences (Sveriges lantbruksuniv.), 1999. http://epsilon.slu.se/avh/1999/91-576-5722-X.pdf.
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Allende-Molar, Raul. "Role of 2,4-diacetylphloroglucinol-producing Pseudomonas fluorescens in the suppression of take-all and pythium root rot of wheat". Online access for everyone, 2006. http://www.dissertations.wsu.edu/Dissertations/Fall2006/r_allende-molar_100506.pdf.
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Mandal, Parimal. "Induction of resistance in tea (Camellia sinensis (L.) O. Kuntze) by biotic and abiotic inducers aganist lasiodiplodia theobromae (Pat) griffon & mauble for management of diplodia disease". Thesis, University of North Bengal, 2008. http://hdl.handle.net/123456789/1353.
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