• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 49
  • 41
  • 16
  • 6
  • 5
  • 5
  • 5
  • 5
  • 5
  • 5
  • 3
  • 3
  • 1
  • 1
  • Tagged with
  • 138
  • 32
  • 30
  • 27
  • 20
  • 19
  • 18
  • 18
  • 18
  • 17
  • 15
  • 13
  • 12
  • 11
  • 10
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
101

Vliv biologické ochrany rostlin na produkci sekundárních metabolitů Papaver somniferum III. / Influence of plant biological protection on production of secondary metabolites of Papaver somniferum III.

Kaman, Petr January 2018 (has links)
Kaman, P.: Influence of plant biological protection on production of secondary metabolites of Papaver somniferum III. Diploma thesis. Charles University, Faculty of Pharmacy in Hradec Králové, Department of Pharmaceutical Botany, Hradec Králové, 2018, 77 pp. Diploma thesis was aimed to verify the impact of biological protection on the production of alkaloids of the opium poppy (Papaver somniferum, L.). Polyversum biofungicide was selected for this purpose, the active ingredient of which is oomycete Pythium oligandrum. The poppy tested were Orbis and Lazur high-morphine varieties. Extracts were prepared from the individual samples which were analyzed by HPLC. The following alkaloids were morphine, codeine, papaverine, noscapine and thebain. The average morphine content was around 0,5 %. The largest amount of 0,62 % was found in the poppyhead of untreated variant of the Orbis variety. Codeine for both varieties averaged 0,07 % in the poppyhead of untreated variant. Treated plants reached slightly lower values. The average papaverine content was around 0,01 % in the treated and also untreated variant, but only in poppyhead of the Lazur variety. Higher noscapine content was measured in the Lazur poppyheads, averaging 0,06 %. The content was only around 0,01 % for Orbis variety. The alkaloid content was...
102

Suscetibilidade in vitro e in vivo da terbinafina, itraconazol, caspofungina, ibuprofeno e fluvastatina, em combinações duplas e triplas, frente a Pythium insidiosum

Argenta, Juliana Siqueira January 2012 (has links)
Pythium insidiosum, um micro-organismo do Reino Stramenopila, é o agente etiológico da pitiose em mamíferos, uma doença difícil de tratar. O presente estudo investigou a atividade inibitória in vitro da terbinafina, itraconazol, caspofungina, fluvastatina e ibuprofeno contra 15 isolados brasileiros de P. insidiosum em combinações duplas e triplas e determinou as correlações in vivo usando coelhos com pitiose experimental. Além disso, este estudo objetivou relatar o crescimento paradoxal de isolados de P. insidiosum quando submetidos a testes de suscetibilidade in vitro com caspofungina. A concentração inibitória mínima (CIM) foi determinada pelo protocolo M 38-A2 do Clinical and Laboratory Standards Institute, e as interações in vitro foram avaliadas usando um método de microdiluição checkerboard. Para o estudo in vivo, 20 coelhos inoculados com zoósporos de P. insidiosum foram divididos em quatro grupos: o grupo 1 foi tratado com terbinafina e itraconazol; o grupo 2 foi tratado com terbinafina, itraconazol e fluvastatina; o grupo 3 foi tratado com terbinafina e caspofungina; e o grupo 4 foi o grupo controle. As combinações de terbinafina com caspofungina ou ibuprofeno foram sinérgicas para 47% dos isolados, e antagonismo não foi observado em nenhuma das combinações duplas. As combinações triplas foram principalmente indiferentes, mas sinergismo e antagonismo também foram observados. O crescimento paradoxal foi observado em 50% dos isolados testados a concentrações acima da CIM variando de 16 a 128 mg/ml. No estudo in vivo, o aspecto histológico das lesões foi similar entre os grupos, mas o grupo 2 mostrou a menor quantidade de hifas e diferiu significativamente dos outros grupos. Os melhores resultados in vivo foram observados quando utilizada a combinação tripla de terbinafina, itraconazol e fluvastatina (grupo 2). O presente estudo foi o primeiro estudo de suscetibilidade in vitro e in vivo com P. insidiosum usando combinações de três fármacos, e o fenômeno do efeito paradoxal envolvendo oomicetos foi descrito aqui pela primeira vez.
103

Controle biológico da podridão radicular (Pythium aphanidermatum) em cultivos hidropônicos

Corrêa, Élida Barbosa [UNESP] 17 December 2009 (has links) (PDF)
Made available in DSpace on 2014-06-11T19:34:59Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-12-17Bitstream added on 2014-06-13T19:24:04Z : No. of bitstreams: 1 correa_eb_dr_botfca.pdf: 989982 bytes, checksum: 71fbc2f45208972feb39e1343c4e6620 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O cultivo hidropônico de hortaliças vem crescendo e se tecnificando no Brasil. No entanto, podridões radiculares causadas por espécies de Pythium constituem um sério problema para a sua expansão. Uma vez o patógeno instalado no sistema, esse pode ser suprimido por meio da adição de microrganismos antagônicos. Além de suprimirem a podridão radicular, esses microrganismos introduzidos na solução nutritiva podem promover o crescimento das plantas, aumentando a receita do produtor. Entretanto, muitas vezes verifica-se baixa sobrevivência dos microrganismos adicionados na solução nutritiva. O desenvolvimento de formulações de agentes de controle biológico, principalmente de bactérias do gênero Pseudomonas, é um fator chave para a sua utilização em escala comercial. Devido à importância da podridão radicular em cultivos hidropônicos e o potencial de utilização do controle biológico da doença, os objetivos do presente trabalho foram (i) selecionar microrganismos residentes do manguezal como agentes de biocontrole da podridão radicular e promotores de crescimento em pepino hidropônico; (ii) avaliar o controle biológico da podridão radicular e a promoção de crescimento por Pseudomonas chlororaphis 63-28 e Bacillus subtilis GB03 em pimentão e alface cultivados em hidroponia; (iii) desenvolver uma formulação de Pseudomonas spp.. Em condições de casa de vegetação, Bacillus cereus AVIC-3-6, isolado de manguezal, protegeu as plantas de pepino do subdesenvolvimento causado pelo patógeno; Gordonia rubripertincta SO-3B-2 e Pseudomonas stutzeri MB-P3A-49, também isolados de manguezal, promoveram o crescimento de plantas de pepino não inoculadas com o patógeno. A adição de P. chlororaphis 63-28 e B. subtilis GB03 na solução nutritiva de pimentão cultivado em hidroponia e inoculado com P. aphanidermatum teve efeito positivo na supressão dos danos causados... / Hydroponic production of vegetables and flowers is increasing in Brazil, and the production technology is improving. A major factor constraining crop productivity is root rot caused by Pythium spp. Root rot severity can be reduced by the application of appropriate antagonistic microbes into the hydroponic nutrient solution or root zone of the crops. When in the root zone beneficial microbes may suppress progress of the root rot and increase crop productivity. However some beneficial microbes are not well-adapted to hydroponic environments and do not survive well in plant nutrient solutions. Ecologically-adapted microbes that are effective against root rot are a key factor for successful root rot control in hydroponic crops. The need for effective biological agents that are adapted to hydroponic systems and appropriately formulated for commercial use prompted investigations with the following aims: i) to select bacterial strains from among isolates obtained from mangrove swamps for effectiveness in controlling Pythium root rot in hydroponic cucumber; ii) to evaluate Pseudomonas chlororaphis 63-28 and Bacillus subtilis GB03 for controlling root rot and promoting growth of hydroponic lettuce and pepper; and iii) to assess formulations of Pseudomonas spp. for long-term shelf life. Bacillus cereus AVIC -3-6 from a mangrove reduced stunting of hydroponic cucumbers associated with Pythium root rot. Gordonia rubripertincta SO-3B-2 and Pseudomonas stutzeri MB-3PA-49 from a mangrove increased growth of healthy cucumber plants. Application of Pseudomonas chlororaphis 63-28 and Bacillus subtilis GB03 into the nutrient solution of hydroponic pepper suppressed root rot and increase the plant growth. Among tested formulations of Pseudomonas chlororaphis 63-28, a formulation with coconut fibre of 80% moisture content had the longest shelf life (up to 32 weeks) when kept at at 3ºC. We conclude that a)... (Complete abstract click electronic access below)
104

Controle biológico da podridão radicular (Pythium aphanidermatum) em cultivos hidropônicos /

Corrêa, Élida Barbosa. 1979- January 2009 (has links)
Resumo: O cultivo hidropônico de hortaliças vem crescendo e se tecnificando no Brasil. No entanto, podridões radiculares causadas por espécies de Pythium constituem um sério problema para a sua expansão. Uma vez o patógeno instalado no sistema, esse pode ser suprimido por meio da adição de microrganismos antagônicos. Além de suprimirem a podridão radicular, esses microrganismos introduzidos na solução nutritiva podem promover o crescimento das plantas, aumentando a receita do produtor. Entretanto, muitas vezes verifica-se baixa sobrevivência dos microrganismos adicionados na solução nutritiva. O desenvolvimento de formulações de agentes de controle biológico, principalmente de bactérias do gênero Pseudomonas, é um fator chave para a sua utilização em escala comercial. Devido à importância da podridão radicular em cultivos hidropônicos e o potencial de utilização do controle biológico da doença, os objetivos do presente trabalho foram (i) selecionar microrganismos residentes do manguezal como agentes de biocontrole da podridão radicular e promotores de crescimento em pepino hidropônico; (ii) avaliar o controle biológico da podridão radicular e a promoção de crescimento por Pseudomonas chlororaphis 63-28 e Bacillus subtilis GB03 em pimentão e alface cultivados em hidroponia; (iii) desenvolver uma formulação de Pseudomonas spp.. Em condições de casa de vegetação, Bacillus cereus AVIC-3-6, isolado de manguezal, protegeu as plantas de pepino do subdesenvolvimento causado pelo patógeno; Gordonia rubripertincta SO-3B-2 e Pseudomonas stutzeri MB-P3A-49, também isolados de manguezal, promoveram o crescimento de plantas de pepino não inoculadas com o patógeno. A adição de P. chlororaphis 63-28 e B. subtilis GB03 na solução nutritiva de pimentão cultivado em hidroponia e inoculado com P. aphanidermatum teve efeito positivo na supressão dos danos causados... (Resumop completo, clicar acesso eletrônico abaixo) / Abstract: Hydroponic production of vegetables and flowers is increasing in Brazil, and the production technology is improving. A major factor constraining crop productivity is root rot caused by Pythium spp. Root rot severity can be reduced by the application of appropriate antagonistic microbes into the hydroponic nutrient solution or root zone of the crops. When in the root zone beneficial microbes may suppress progress of the root rot and increase crop productivity. However some beneficial microbes are not well-adapted to hydroponic environments and do not survive well in plant nutrient solutions. Ecologically-adapted microbes that are effective against root rot are a key factor for successful root rot control in hydroponic crops. The need for effective biological agents that are adapted to hydroponic systems and appropriately formulated for commercial use prompted investigations with the following aims: i) to select bacterial strains from among isolates obtained from mangrove swamps for effectiveness in controlling Pythium root rot in hydroponic cucumber; ii) to evaluate Pseudomonas chlororaphis 63-28 and Bacillus subtilis GB03 for controlling root rot and promoting growth of hydroponic lettuce and pepper; and iii) to assess formulations of Pseudomonas spp. for long-term shelf life. Bacillus cereus AVIC -3-6 from a mangrove reduced stunting of hydroponic cucumbers associated with Pythium root rot. Gordonia rubripertincta SO-3B-2 and Pseudomonas stutzeri MB-3PA-49 from a mangrove increased growth of healthy cucumber plants. Application of Pseudomonas chlororaphis 63-28 and Bacillus subtilis GB03 into the nutrient solution of hydroponic pepper suppressed root rot and increase the plant growth. Among tested formulations of Pseudomonas chlororaphis 63-28, a formulation with coconut fibre of 80% moisture content had the longest shelf life (up to 32 weeks) when kept at at 3ºC. We conclude that a)... (Complete abstract click electronic access below) / Orientador: Wagner Bettiol / Coorientador: John Clifford Sutton / Banca: Antonio Carlos Maringoni / Banca: Edson Luiz Furtado / Banca: Marcelo Augusto Boechat Morandi / Doutor
105

Suscetibilidade in vitro e in vivo da terbinafina, itraconazol, caspofungina, ibuprofeno e fluvastatina, em combinações duplas e triplas, frente a Pythium insidiosum

Argenta, Juliana Siqueira January 2012 (has links)
Pythium insidiosum, um micro-organismo do Reino Stramenopila, é o agente etiológico da pitiose em mamíferos, uma doença difícil de tratar. O presente estudo investigou a atividade inibitória in vitro da terbinafina, itraconazol, caspofungina, fluvastatina e ibuprofeno contra 15 isolados brasileiros de P. insidiosum em combinações duplas e triplas e determinou as correlações in vivo usando coelhos com pitiose experimental. Além disso, este estudo objetivou relatar o crescimento paradoxal de isolados de P. insidiosum quando submetidos a testes de suscetibilidade in vitro com caspofungina. A concentração inibitória mínima (CIM) foi determinada pelo protocolo M 38-A2 do Clinical and Laboratory Standards Institute, e as interações in vitro foram avaliadas usando um método de microdiluição checkerboard. Para o estudo in vivo, 20 coelhos inoculados com zoósporos de P. insidiosum foram divididos em quatro grupos: o grupo 1 foi tratado com terbinafina e itraconazol; o grupo 2 foi tratado com terbinafina, itraconazol e fluvastatina; o grupo 3 foi tratado com terbinafina e caspofungina; e o grupo 4 foi o grupo controle. As combinações de terbinafina com caspofungina ou ibuprofeno foram sinérgicas para 47% dos isolados, e antagonismo não foi observado em nenhuma das combinações duplas. As combinações triplas foram principalmente indiferentes, mas sinergismo e antagonismo também foram observados. O crescimento paradoxal foi observado em 50% dos isolados testados a concentrações acima da CIM variando de 16 a 128 mg/ml. No estudo in vivo, o aspecto histológico das lesões foi similar entre os grupos, mas o grupo 2 mostrou a menor quantidade de hifas e diferiu significativamente dos outros grupos. Os melhores resultados in vivo foram observados quando utilizada a combinação tripla de terbinafina, itraconazol e fluvastatina (grupo 2). O presente estudo foi o primeiro estudo de suscetibilidade in vitro e in vivo com P. insidiosum usando combinações de três fármacos, e o fenômeno do efeito paradoxal envolvendo oomicetos foi descrito aqui pela primeira vez.
106

Some aspects on the taxonomy, ecology and histology of Pythium Pringsheim species associated with Fucus distichus in estuaries and marine habitats of British Columbia

Thompson, Timothy Alan January 1982 (has links)
Pythium undulatum var. litorale Hohnk was found to infect Fucus distichus in the Squamish River estuary of southern British Columbia. This thesis adresses the questions of: 1.) whether this symbiosis can be found outside the Squamish River estuary, 2.) relationship of the infection within the estuary to the distribution of P. undulatum var. litorale in estuarine sediments, 3.) taxonomically defining those species associated with Fucus and/or in estuarine sediments, and 4.) the host parasite relationship as determined by means of histochemical and light microscope observations. Results indicated that outside the Squamish River estuary, associations between pythiaceous fungi and Fucus are uncommon in British Columbia coastal areas. Sampling of live and decaying Fucus plants from 10 field stations in British Columbia and Washington yielded only 4 species, the most common isolate being Phytophthora vesicula. Within the Squamish estuary, an association was found to exist between the distribution of P. undulatum var. 1itorale in the sediments and the distribution of infected Fucus plants. Sediment sampling from the Fraser River estuary, where Fucus does not occur, yielded P. undulatum var. litorale, suggesting that the fungus is probably indigenous to estuarine sediments. Numerous other species of Pythium were recovered from estuarine sediments, including P. butler i, P. carolinianum, P. catenulatum, P. gracile, P. torulosum , and P. volutum . Two taxa are described in detail. Pythium undulatum var. litorale was originally described by Hohnk (1953), but the varietal status was rejected by Waterhouse (1967). Arguments are presented for retention of the variety. Pythiogeten utriforme Minden is transferred to the genus Pythium and P. hohnkii is proposed as the nomen nova of this taxon. A discussion of the generic characteristics of the genus Pythiogeten is presented. In order to facilitate an understanding of the infection process by Pythium species, the anatomy and histochemistry of Fucus distichus were examined. Anatomically, F. distichus agrees with earlier reports of other species of Fucus. The internal structure of cells was found to agree with descriptions in earlier publications, although higher physode content was noted in F. distichus. Histochemical staining suggested that cell walls of Fucus are three layered; having an outer fucan-rich layer, a middle layer composed principally of alginic acid, and an innermost layer of cellulose. Several phenolic-indicating reagents were tested on both fresh and fixed/embedded Fucus tissue, resulting in some interesting new observations of phenolics in the matrix. The host-parasite interface of P. undulatum var. 1itorale and F. distichus was also examined by use of histochemistry and the light microscope. Macroscopically, the infection of F. distichus occurs behind the most recent dichotomy, and lesions are necrotic, firm (flaccid with age), and are pink-to-red in color. Microscopically, fungal hyphae are confined to the cortical and medullary regions. Hyphae appear to penetrate host cell walls by means of an enzymatic dissolution of the alginic acid and cellulosic portions of the cell wall. Use of the Periodic Acid/Schiff's reagent shows a distinct non-staining halo at the point where hyphae cross the cell wall. Pit connections between cortical cells were observed to break down with hyphae present in only one cell, suggesting that the fungus is capable of parasitizing several cells via digestion of pits. Gemmae were observed to form in both cortical and medullary cells. The response by Fucus to infection is an active one; a hypersensitivity reaction analagous to that of higher plants is observed. Cells in advance of fungal hyphae are observed to autolyse. Normally metabolically quiescent medullary filaments are observed to have an increase in general protein levels and to have increased physode content. Physodes become polarized within the medullary cells, and coalesce to form larger units, which are then delimited from the producing cell by a cross wall. The fate of these 'giant' physodes was not observed, but it is believed that these cells autolyse and release their phenolic contents to the matrix, as levels of phenolic-reactive material were observed to increase in this region. Coupled with the buildup,of phenolics in the matrix is a decrease in the fucan component of the matrix. Stress and tear lines appear between cells, and eventually this region serves as an abscission zone by which the infected portions are dropped out of the plant. Behind the abscission zone, medullary filaments undergo transverse divisions to form irregular, cuboidal cells which function as epidermis after abscission of the lesion occurs. / Science, Faculty of / Botany, Department of / Graduate
107

Suscetibilidade in vitro e in vivo da terbinafina, itraconazol, caspofungina, ibuprofeno e fluvastatina, em combinações duplas e triplas, frente a Pythium insidiosum

Argenta, Juliana Siqueira January 2012 (has links)
Pythium insidiosum, um micro-organismo do Reino Stramenopila, é o agente etiológico da pitiose em mamíferos, uma doença difícil de tratar. O presente estudo investigou a atividade inibitória in vitro da terbinafina, itraconazol, caspofungina, fluvastatina e ibuprofeno contra 15 isolados brasileiros de P. insidiosum em combinações duplas e triplas e determinou as correlações in vivo usando coelhos com pitiose experimental. Além disso, este estudo objetivou relatar o crescimento paradoxal de isolados de P. insidiosum quando submetidos a testes de suscetibilidade in vitro com caspofungina. A concentração inibitória mínima (CIM) foi determinada pelo protocolo M 38-A2 do Clinical and Laboratory Standards Institute, e as interações in vitro foram avaliadas usando um método de microdiluição checkerboard. Para o estudo in vivo, 20 coelhos inoculados com zoósporos de P. insidiosum foram divididos em quatro grupos: o grupo 1 foi tratado com terbinafina e itraconazol; o grupo 2 foi tratado com terbinafina, itraconazol e fluvastatina; o grupo 3 foi tratado com terbinafina e caspofungina; e o grupo 4 foi o grupo controle. As combinações de terbinafina com caspofungina ou ibuprofeno foram sinérgicas para 47% dos isolados, e antagonismo não foi observado em nenhuma das combinações duplas. As combinações triplas foram principalmente indiferentes, mas sinergismo e antagonismo também foram observados. O crescimento paradoxal foi observado em 50% dos isolados testados a concentrações acima da CIM variando de 16 a 128 mg/ml. No estudo in vivo, o aspecto histológico das lesões foi similar entre os grupos, mas o grupo 2 mostrou a menor quantidade de hifas e diferiu significativamente dos outros grupos. Os melhores resultados in vivo foram observados quando utilizada a combinação tripla de terbinafina, itraconazol e fluvastatina (grupo 2). O presente estudo foi o primeiro estudo de suscetibilidade in vitro e in vivo com P. insidiosum usando combinações de três fármacos, e o fenômeno do efeito paradoxal envolvendo oomicetos foi descrito aqui pela primeira vez.
108

Imunoproteômica do oomiceto Pythium insidiosum antígenos candidatos ao diagnóstico da pitiose equina /

Chechi, Jéssica Luana January 2020 (has links)
Orientador: Sandra de Moraes Gimenes Bosco / Resumo: A pitiose, cujo agente etiológico é o oomiceto Pythium insidiosum, é uma doença emergente que ocorre principalmente em países tropicais e subtropicais, afetando diversas espécies animais, sendo mais frequente em cavalos no Brasil e humanos na Tailândia. A doença é difícil de diagnosticar, porque as hifas do patógeno são frequentemente confundidas com mucormicoses ou entomoftoromicoses em cortes histológicos. Além disso, não há antígeno eficiente e específico que possa ser utilizado para o diagnóstico rápido e o tratamento eficiente da pitiose em diferentes espécies. Os antígenos são moléculas que o sistema imunológico reconhece, tornando essas moléculas importantes alvos para o diagnóstico de micro-organismos. Para a identificação de antígenos, a imunoproteômica é considerada uma ferramenta poderosa. Nesse sentido, investigamos quais antígenos de P. insidiosum são reconhecidos pelo soro de equinos no Brasil e por soro de pacientes tailandeses com pitiose, a fim de encontrar proteínas semelhantes que possam ser utilizadas para futuros testes de diagnóstico ou terapia para pitiose. Para identificar as proteínas imunorreativas de P. insidiosum, foram utilizadas abordagens imunoproteômicas, técnica de Western blot, seguida pela identificação de antígenos por espectrometria de massas. Consequentemente, foi possível identificar 23 antígenos reconhecidos entre os soros de equinos e humanos. Sete antígenos foram correspondentes aos soros em ambas espécies: heat shock cognate 70 KDa p... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Pythiosis, whose etiological agent is the oomycete Pythium insidiosum, is an lifethreatening disease that occurs mainly in tropical and subtropical countries, affecting several animal species, being more frequent in horses in Brazil and humans in Thailand. The disease is difficult to diagnose, because the pathogen's hyphae are often confused with Mucorales or Entomophthorales fungi in histological sections. In addition, there is no efficient and specific antigen that can be used for the rapid diagnosis and efficient treatment of pythiosis in different species. Antigens are molecules that the immune system recognizes, making these molecules important targets for the diagnosis of microorganisms. For the identification of antigens, immunoproteomics is considered a powerful tool. In this sense, we investigated which P. insidiosum antigens are recognized by horses in Brazil and Thai humans’ serum with pythiosis, in order to find similar proteins that could be used for future diagnostic tests or therapy approaches for pythiosis. To identify the immunoreactive proteins of P. insidiosum, immunoproteomic approaches were used, using the Western blot technique followed by the identification of antigens by mass spectrometry. Consequently, it was possible to identify 23 antigens recognized between the serum of horses and humans. Seven antigens were similar to the two types of serum, being heat shock cognate 70 KDa protein, heat shock 70 KDa protein, glucan 1,3-beta-glucosidase, fructosebi... (Complete abstract click electronic access below) / Doutor
109

Combating Fungal Pathogens (Helminthosporium solani, Pythium ultimum) with Secondary Metabolites of Streptomyces Bacteria

Kemp, Erik W. 02 March 2022 (has links)
Fungal diseases, Pythium ultimum (Pythium leak) and Helminthosporium solani (silver scurf) have detrimental effects on potato tuber (Solanum tuberosum) quality and yield. Tubers are the world’s fourth largest agricultural food crop and are crucial for feeding a growing population. Bacteria from the genus Streptomyces are known for producing a wide variety of secondary metabolites with antifungal properties. Isolates of Streptomyces have recently shown inhibitory effects towards P. ultimum and H. solani in Petri dish assays. These data suggest that Streptomyces may work as a biocontrol to protect tubers from P. ultimum and H. solani. We tested talc-based powder formulas for their ability to maintain viable Streptomyces spores in storage. The formula that maintained spores the longest was then used to coat varying Streptomyces isolates onto a tuber surface that contained, or would be exposed to P. ultimum or H. solani. Tests were conducted in a lab, greenhouse, and field setting. We found a powder formula that kept 50% of the added Streptomyces spores viable for a period of three to six months depending on the isolate. Isolates with inhibitory effects towards H. solani were applied as a powder on seed tubers infected with H. solani and grown in a greenhouse. Upon completion of the experiment, we found that progeny tubers from neither the treatment nor the control groups contained H. solani. Instead, we found a similar surface pathogen, Colletotrichum coccodes (Black dot), on many of the progeny tubers. While not the target pathogen of this study, some isolates significantly limited C. coccodes compared to the control. This experiment was repeated in a field setting where C. coccodes was again the primary disease found on the progeny tubers. In the field, isolates showed no inhibitory effect towards C. coccodes. Isolates with inhibitory effects towards P. ultimum were applied as a powder onto wounded tubers. One hour later the tubers were exposed to P. ultimum. Isolates did not limit P. ultimum compared to the control after a week of incubation. A follow up experiment revealed that the Streptomyces isolate used needed at least 24 hours of growth to produce antifungal secondary metabolites. Our data suggest that Streptomyces bacteria can easily be stored in a powder and that there are beneficial effects as a biocontrol against C. coccodes. Our data also suggest that timing Streptomyces application for maximum secondary metabolite production may improve its efficacy as a biocontrol.
110

EVALUATION AND FUNCTIONAL CHARACTERIZATION OF BIOCONTROL AGENTS TARGETING SELECT SOILBORNE PATHOGENS OF SOYBEAN

Filgueira Pimentel, Mirian 01 June 2021 (has links) (PDF)
Soybean crops are vulnerable to a wide range of pathogens that reduce yield and cause extensive losses worldwide. In the United States, the soilborne pathogens Pythium spp., causing soybean damping-off, and Fusarium virguliforme, causing sudden death syndrome (SDS) of soybean, have been among the top diseases that most reduced soybean yields. This study demonstrated that biological control using native fungal antagonists could be a powerful tool to integrate with current management strategies for more efficient control of Pythium damping-off and SDS in soybean. Trichoderma spp. and Clonostachys rosea demonstrated the ability to mycoparasitize and antagonize the pathogens using different mechanisms and exhibited a protective effect on soybean in field conditions. The development of an efficient biological control program for disease management relies on a deep understanding of the BCA-pathogen interaction’s biology. This research also uncovered the molecular mechanisms involved in the F. virguliforme-T. afroharzianum interaction by using a dual RNAseq approach. Significant changes in both fungal organisms’ transcriptomes were discovered at different stages in their interaction. The results provided here can contribute to the future implementation of effective biological control programs for soybean. The benefits may also extend to other crops.

Page generated in 0.0606 seconds