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1.
Microbiol Res ; 230: 126347, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31586859

RESUMO

Biocontrol has emerged in recent years as an alternative to pesticides. Given the importance of environmental preservation using biocontrol, in this study two antagonistic bacteria against phytopathogenic fungi were isolated and evaluated. These bacterial strains, identified as Paenibacillus polymyxa NMA1017 and Burkholderia cenocepacia CACua-24, inhibited (70 to 80%) the development of two phytopathogens of economic importance: the fungus Rhizoctonia solani RhCh-14, isolated from chili pepper, and the oomycete Pythium ultimum PyFr-14, isolated from tomato. The spectrum was not limited to the previous pathogens, but also to other phytopathogenic fungus, some bacteria and other oomycetes. Fungi-bacteria microcultures observed with optical and scanning electron microscopy revealed hyphae disintegration and pores formation. The antifungal activity was found also in the supernatant, suggesting a diffusible compound is present. Innocuous tests on tobacco leaves, blood agar, bean seed germination and in Galleria mellonella larvae showed that strain NMA1017 has the potential to be a biocontrol agent. Greenhouse experiments with bean plants inoculated with P. polymyxa exhibited the efficacy to inhibit the growth of R. solani and P. ultimum. Furthermore, P. polymyxa NMA1017 showed plant growth promotion activities, such as siderophore synthesis and nitrogen fixation which can contribute to the crop development.


Assuntos
Antifúngicos/farmacologia , Burkholderia cenocepacia/química , Paenibacillus polymyxa/química , Controle Biológico de Vetores/métodos , Doenças das Plantas/microbiologia , Pythium/efeitos dos fármacos , Rhizoctonia/efeitos dos fármacos , Antifúngicos/metabolismo , Burkholderia cenocepacia/metabolismo , Paenibacillus polymyxa/metabolismo , Pythium/crescimento & desenvolvimento , Pythium/fisiologia , Rhizoctonia/crescimento & desenvolvimento , Rhizoctonia/fisiologia , Tabaco/crescimento & desenvolvimento , Tabaco/microbiologia
2.
Plant Dis ; 103(11): 2877-2883, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31490089

RESUMO

Some diseases are caused by coinfection of several pathogens in the same plant. However, studies on the complexity of these coinfection events under different environmental conditions are scarce. Our ongoing research involves late wilting disease of cucumber caused by coinfection of Cucumber green mottle mosaic virus (CGMMV) and Pythium spp. We specifically investigated the role of various temperatures (18, 25, 32°C) on the coinfection by CGMMV and two predominant Pythium species occurring in cucumber greenhouses under Middle Eastern climatic conditions. During the summer months, Pythium aphanidermatum was most common, whereas P. spinosum predominated during the winter-spring period. P. aphanidermatum preferred higher temperatures while P. spinosum preferred low temperatures and caused very low levels of disease at 32°C when the 6-day-old seedlings were infected with P. spinosum alone. Nevertheless, after applying a later coinfection with CGMMV on the 14-day-old plants, a synergistic effect was detected for both Pythium species at optimal and suboptimal temperatures, with P. spinosum causing high mortality incidence even at 32°C. The symptoms caused by CGMMV infection appeared earlier as the temperature increased. However, within each temperature, no significant influence of the combined infection was detected. Our results demonstrate the complexity of coinfection in changing environmental conditions and indicate its involvement in disease development and severity as compared with infection by each of the pathogens alone.


Assuntos
Cucumis sativus , Meio Ambiente , Doenças das Plantas , Pythium , Tobamovirus , Cucumis sativus/parasitologia , Cucumis sativus/virologia , Doenças das Plantas/parasitologia , Doenças das Plantas/virologia , Pythium/fisiologia , Tobamovirus/fisiologia
3.
Plant Dis ; 103(7): 1685-1692, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31115270

RESUMO

In Quebec muck soils, Pythium stunt (Pythium tracheiphilum Matta) is responsible for important yield losses in head lettuce crops each year, which can reach up to 50% in certain cases. Despite the significance of the disease, factors influencing its development remain poorly documented, and no disease risk indicators are available, which makes the development of management strategies difficult. Hence, growers systematically use chemical fungicides throughout the growing season to reduce crop losses. However, it is known that soilborne disease incidence or severity may be influenced by soil inoculum density and environmental parameters. Therefore, the objectives of this study were to investigate the influence of inoculum density on lettuce growth under controlled conditions and evaluate the influence of soil inoculum density, air temperature, relative humidity, and rainfall on disease incidence under field conditions. In particular, this study aims to develop accurate predictors for Pythium stunt incidence. Results showed that, under controlled environment, thresholds of inoculum density of 97 and 46 propagules per gram of dry soil were needed to reduce lettuce dry weight by one-half for cultivars Estival and Prestige, respectively. These results were confirmed under field conditions, where a soil inoculum density >132 propagules per gram of dry soil combined with air temperatures <18°C for the first 2 weeks and rain accumulation >64 mm for the first 3 weeks after transplanting accurately predicted disease incidence 79% of the time. These relationships improve understanding of seasonal Pythium stunt development and will provide useful tools to develop sustainable management strategies.


Assuntos
Meio Ambiente , Doenças das Plantas , Pythium , Produtos Agrícolas/parasitologia , Alface/parasitologia , Pythium/fisiologia , Quebeque , Solo/parasitologia
4.
Immunobiology ; 224(3): 427-432, 2019 05.
Artigo em Inglês | MEDLINE | ID: mdl-30765134

RESUMO

BACKGROUND: Pythium insidiosum has been mainly reported to cause morbidity and mortality in thalassemia patients. P. insidiosum zoospores can germinate to be hyphae within a few hours; therefore, it is difficult to study the initial immune response that P. insidiosum zoospores induce. The present study aims to compare immune responses against P. insidiosum zoospore infection by comparing monocytes/macrophages from thalassemia patients with those from non-thalassemia controls. METHODS: In order to keepP. insidiosum in the zoospore stage in vitro for inoculation, the P. insidiosum zoospores were preserved without germination by treatment with inorganic hypochlorite solution. CD14+ cells were isolated from peripheral blood mononuclear cells of thalassemia and non-thalassemia donors and then left to transition to macrophages. Monocytes/macrophage culture was infected with P. insidiosum zoospores and culture supernatants were subjected to Th1/Th2 multiplex cytokine detection. RESULTS: Our study of cytokine production revealed that the basal level of GM-CSF produced by thalassemia monocytes/macrophages was lower than that observed in monocytes/macrophages of non-thalassemia individuals. Higher GM-CSF and IFN-γ response was also found when cells from non-thalassemia people were stimulated with P. insidiosum zoospores compared to thalassemia cells. It was also found that TNF-α, GM-CSF and IFN-γ productions from monocytes/macrophages of thalassemia patients who received iron chelator treatment were significantly higher than those produced from thalassemia patients without iron chelator treatment. CONCLUSION: For the first time, the present study demonstrates defective immune responses in monocytes/macrophages derived from thalassemia patients in response toP. insidiosum zoospore infection. The results also show an inverse correlation between iron overload and cytokine production in monocytes/macrophages of thalassemia patients. This finding could explain why thalassemia patients are susceptible to P. insidiosum infection.


Assuntos
Quelantes de Ferro/uso terapêutico , Macrófagos/imunologia , Monócitos/imunologia , Pitiose/imunologia , Pythium/fisiologia , Talassemia beta/imunologia , Adolescente , Adulto , Células Cultivadas , Citocinas/metabolismo , Feminino , Humanos , Imunidade , Sobrecarga de Ferro , Masculino , Pessoa de Meia-Idade , Pitiose/tratamento farmacológico , Esporos Fúngicos/imunologia , Adulto Jovem , Talassemia beta/tratamento farmacológico
5.
Plant Dis ; 103(3): 475-483, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-30657427

RESUMO

In Canada, head lettuce (Lactuca sativa capitata) is extensively produced in the muck soils of southwestern Québec. However, yields are increasingly affected by various soilborne pathogens, including Pythium spp., which cause wilt and damping off. In a survey conducted in Québec muck soils in 2010 and 2011, Pythium tracheiphilum Matta was identified as the predominant Pythium sp. in the root of head lettuce showing Pythium stunt symptoms. Therefore, to improve risk assessment and help further understanding of disease epidemiology, a specific and sensitive real-time quantitative polymerase chain reaction (qPCR) assay based on TaqMan-minor groove binder (MGB) technology was developed for P. tracheiphilum. The PCR primers along with a TaqMan-MGB probe were designed from the ribosomal internal transcribed spacer 2 region. A 100-bp product was amplified by PCR from all P. tracheiphilum isolates tested while no PCR product was obtained from 38 other Pythium spp. or from a selection of additional lettuce pathogens tested. In addition to P. tracheiphilum, the assay was multiplexed with an internal control allowing for the individual validation of each PCR. In artificially infested soils, the sensitivity of the qPCR assay was established as 10 oospores/g of dry soil. P. tracheiphilum was not detected in soils in which lettuce has never been grown; however, inoculum ranged from 0 to more than 200,000 oospores/g of dry soil in commercial lettuce fields. Also, disease incidence was positively correlated with inoculum concentration (r = 0.764). The results suggest that inoculum concentration should be considered when making Pythium stunt management decisions. The developed qPCR assay will facilitate reliable detection and quantification of P. tracheiphilum from field soil.


Assuntos
Reação em Cadeia da Polimerase Multiplex , Pythium , Reação em Cadeia da Polimerase em Tempo Real , Solo , Canadá , Primers do DNA , Pythium/genética , Pythium/fisiologia , Quebeque , Solo/parasitologia
6.
Vet Radiol Ultrasound ; 60(2): E20-E23, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-28547920

RESUMO

A Staffordshire terrier presented for evaluation of a chronic, nonproductive cough that was unresponsive to antibiotic therapy. A large mass identified in the pulmonary hilum was most consistent with tracheobronchial lymphadenopathy on radiographic and computed tomography (CT) images. Bronchoscopy confirmed a mass compressing the dorsal portion of the intrathoracic trachea. Bronchoscopic biopsies of the tracheal mass revealed necrosuppurative and eosinophilic inflammation with intralesional Pythium insidiousum hyphae. Pythiosis should be included as a differential diagnosis for tracheobronchial lymphadenopathy and bronchopneumopathy in dogs, especially when the patient is from or has visited a region endemic for Pythium insidiosum.


Assuntos
Broncopatias/veterinária , Tosse/veterinária , Doenças do Cão/diagnóstico , Pneumopatias/veterinária , Linfadenopatia/veterinária , Pitiose/diagnóstico , Doenças da Traqueia/veterinária , Animais , Broncopatias/diagnóstico , Broncopatias/diagnóstico por imagem , Broncopatias/microbiologia , Broncoscopia/veterinária , Tosse/diagnóstico por imagem , Diagnóstico Diferencial , Doenças do Cão/diagnóstico por imagem , Doenças do Cão/microbiologia , Cães , Pneumopatias/diagnóstico , Pneumopatias/diagnóstico por imagem , Pneumopatias/microbiologia , Linfadenopatia/diagnóstico , Linfadenopatia/diagnóstico por imagem , Linfadenopatia/microbiologia , Masculino , Pitiose/diagnóstico por imagem , Pitiose/microbiologia , Pythium/fisiologia , Radiografia/veterinária , Tomografia Computadorizada por Raios X/veterinária , Doenças da Traqueia/diagnóstico , Doenças da Traqueia/diagnóstico por imagem , Doenças da Traqueia/microbiologia
7.
Pest Manag Sci ; 75(2): 356-365, 2019 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-29888848

RESUMO

BACKGROUND: Pythium species attack various vegetable crops causing seed, stem and root rot, and 'damping-off' after germination. Pythium diseases are prevalently controlled by two classes of fungicides, QoIs with azoxystrobin and phenlyamides with mefenoxam as representatives. The present study aimed to test the sensitivity of six Pythium species from different vegetable crops to azoxystrobin and mefenoxam and differentiating species based on ITS, cytochrome b and RNA polymerase I gene sequences. RESULTS: The inter- and intra-species sensitivity to azoxystrobin was found to be stable, with the exception of one Pythium paroecandrum isolate, which showed reduced sensitivity and two cytochrome b amino acid changes. For mefenoxam, the inter-species sensitivity was quite variable and many resistant isolates were found in all six Pythium species, but no RNA polymerase I amino acid changes were observed in them. ITS and cytochrome b phylogenetic analyses permitted a clear separation of Pythium species corresponding to globose- and filamentous-sporangia clusters. CONCLUSION: The results document the necessity of well-defined chemical control strategies adapted to different Pythium species. Since the intrinsic activity of azoxystrobin among species was stable and no resistant isolates were found, it may be applied without species differentiation, provided it is used preventatively to also control highly aggressive isolates. For a reliable use of mefenoxam, precise identification and sensitivity tests of Pythium species are crucial because its intrinsic activity is variable and resistant isolates may exist. Appropriate mixtures and/or alternation of products may help to further delay resistance development. © 2018 Society of Chemical Industry.


Assuntos
Alanina/análogos & derivados , Fungicidas Industriais/farmacologia , Doenças das Plantas/classificação , Pirimidinas/farmacologia , Pythium/classificação , Pythium/efeitos dos fármacos , Estrobilurinas/farmacologia , Transportadores de Cassetes de Ligação de ATP/análise , Alanina/farmacologia , Sequência de Aminoácidos , Produtos Agrícolas/microbiologia , Citocromos b/química , Citocromos b/genética , Citocromos b/metabolismo , DNA Espaçador Ribossômico/análise , Proteínas Fúngicas/química , Proteínas Fúngicas/genética , Proteínas Fúngicas/metabolismo , Filogenia , Doenças das Plantas/microbiologia , Pythium/fisiologia , Reação em Cadeia da Polimerase em Tempo Real , Alinhamento de Sequência , Verduras/microbiologia
8.
Plant Dis ; 102(12): 2560-2570, 2018 12.
Artigo em Inglês | MEDLINE | ID: mdl-30346246

RESUMO

Rhododendrons are an important crop in the ornamental nursery industry, but are prone to Phytophthora root rot. Phytophthora root rot is a continuing issue on rhododendrons despite decades of research. Several Phytophthora species are known to cause root rot, but most research has focused on P. cinnamomi, and comparative information on pathogenicity is limited for other commonly encountered oomycetes, including Phytophthora plurivora and Pythium cryptoirregulare. In this study, three isolates each of P. cinnamomi, P. plurivora, and Py. cryptoirregulare were used to inoculate rhododendron cultivars Cunningham's White and Yaku Princess at two different inoculum levels. All three species caused disease, especially at the higher inoculum level. P. cinnamomi and P. plurivora were the most aggressive pathogens, causing severe root rot, whereas Py. cryptoirregulare was a weak pathogen that only caused mild disease. Within each pathogen species, isolate had no influence on disease. Both P. cinnamomi and P. plurivora caused more severe disease on Cunningham's White than on Yaku Princess, suggesting that the relative resistance and susceptibility among rhododendron cultivars might be similar for both pathogens. Reisolation of P. cinnamomi and P. plurivora was also greater from plants exhibiting aboveground symptoms of wilting and plant death and belowground symptoms of root rot than from those without symptoms. Results show that both P. cinnamomi and P. plurivora, but not Py. cryptoirregulare, are important pathogens causing severe root rot in rhododendron. This study establishes the risks for disease resulting from low and high levels of inoculum for each pathogen. Further research is needed to evaluate longer term risks associated with low inoculum levels on rhododendron health and to explore whether differences among pathogen species affect disease control.


Assuntos
Phytophthora/fisiologia , Doenças das Plantas/estatística & dados numéricos , Pythium/fisiologia , Rhododendron/parasitologia , Suscetibilidade a Doenças , Doenças das Plantas/parasitologia , Raízes de Plantas/genética , Raízes de Plantas/imunologia , Raízes de Plantas/parasitologia , Rhododendron/genética , Rhododendron/imunologia
9.
Plant Dis ; 102(11): 2241-2252, 2018 11.
Artigo em Inglês | MEDLINE | ID: mdl-30222055

RESUMO

Pythium seedling blight, which can be caused by a number of Pythium spp., is a disease that affects soybean (Glycine max) in the United States and Canada. Pythium ultimum var. ultimum, one of the most common pathogenic species, is favored by cool, wet conditions in early spring and causes seed decay, root rot, and seedling damping-off. In all, 102 major ancestors of modern North American cultivars and "first progeny" cultivars developed directly from ancestral lines were evaluated for resistance to P. ultimum var. ultimum and two other species of Pythium in greenhouse assays. Several ancestors and first progeny cultivars, as well as the resistant check Archer, had varying levels of partial resistance to an Illinois isolate of P. ultimum var. ultimum. In a subsequent experiment, four of the most resistant lines (PI 84637, Maple Isle, Fiskeby III, and Fiskeby 840-7-3) and the susceptible cultivar Kanro were screened for resistance against isolates of P. irregulare and P. sylvaticum, and resistance to P. ultimum var. ultimum was confirmed. The lines that were partially resistant to P. ultimum var. ultimum in the first experiment were also partially resistant to P. irregulare and P. sylvaticum. The P. ultimum var. ultimum isolate was the most aggressive of the three isolates, followed by the P. irregulare and P. sylvaticum isolates. Modern cultivars descended from the soybean lines with partial resistance to these pathogens could be useful sources of resistance to Pythium seedling blight if they are found to have similar levels of resistance.


Assuntos
Resistência à Doença/genética , Doenças das Plantas/imunologia , Pythium/fisiologia , Soja/genética , Doenças das Plantas/parasitologia , Plântula/genética , Plântula/imunologia , Plântula/microbiologia , Soja/imunologia , Soja/parasitologia , Especificidade da Espécie
10.
Plant Dis ; 102(11): 2194-2200, 2018 11.
Artigo em Inglês | MEDLINE | ID: mdl-30226419

RESUMO

To improve our understanding of the timing of cold stress and its effect on Pythium damping-off, we performed a factorial experiment with two cold stress temperatures (4 and 10°C); exposure to 96 h of cold stress at 0, 1, 2, 4, 6, and 8 days after planting; and inoculation with Pythium sylvaticum-infested millet or control. Increased susceptibility to damping-off resulting in reduced emergence was found in inoculated plants when the cold stress period began 2 or 4 days after planting. In the noninoculated controls, no effect of cold stress on emergence was observed. Slower seedling growth was observed during the cold stress period and in inoculated plants after exposure to cold stress. Seed exudation, mycelial growth, and sporangia germination of P. sylvaticum was evaluated at 4, 10, and 18°C. The greatest seed exudation was observed at 4°C. Low temperatures delayed mycelial growth of P. sylvaticum, although the pathogen was still able to grow at 4°C. Sporangia incubated for 3 h at 18°C in the presence of seed exudates had higher germination in comparison with sporangia incubated at 10 or 4°C. Moreover, more sporangia germinated in response to seed exudates that were previously collected from seed imbibed for 24 h at low temperatures (4°C). These results suggest that cold stress 2 to 4 days after planting increases soybean susceptibility to damping-off, presumably because of increased seed exudation and delayed seedling growth.


Assuntos
Suscetibilidade a Doenças , Doenças das Plantas/prevenção & controle , Pythium/fisiologia , Soja/fisiologia , Estresse Fisiológico , Temperatura Baixa/efeitos adversos , Micélio , Doenças das Plantas/parasitologia , Plântula/crescimento & desenvolvimento , Plântula/parasitologia , Plântula/fisiologia , Soja/crescimento & desenvolvimento , Soja/parasitologia
11.
Appl Microbiol Biotechnol ; 102(16): 6827-6839, 2018 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-29948111

RESUMO

Ginger (Zingiber officinale Rosc.) is a tropical plant cultivated all over the world due to its culinary and medicinal properties. It is one of the most important spices commonly used in food, which increases its commercial value. However, soft rot (rhizome rot) is a common disease of ginger caused by fungi such as Pythium and Fusarium spp. It is the most destructive disease of ginger, which can reduce the production by 50 to 90%. Application of chemical fungicides is considered as an effective method to control soft rot of ginger but extensive use of fungicides pose serious risk to environmental and human health. Therefore, the development of ecofriendly and economically viable alternative approaches for effective management of soft rot of ginger such diseases is essentially required. An acceptable approach that is being actively investigated involves nanotechnology, which can potentially be used to control Pythium and Fusarium. The present review is aimed to discuss worldwide status of soft rot associated with ginger, the traditional methods available for the management of Pythium and Fusarium spp. and most importantly, the role of various nanomaterials in the management of soft rot of ginger. Moreover, possible antifungal mechanisms for chemical fungicides, biological agents and nanoparticles have also been discussed.


Assuntos
Fusarium/fisiologia , Gengibre/microbiologia , Nanotecnologia/tendências , Doenças das Plantas/prevenção & controle , Pythium/fisiologia , Doenças das Plantas/microbiologia
12.
Plant Dis ; 102(4): 753-759, 2018 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30673404

RESUMO

In the last decade, the phenomenon of late-wilting has increased in cucumber greenhouses during Cucumber green mottle mosaic virus (CGMMV) epidemics. Because the wilting appears in defined patches accompanied by root rot, it was hypothesized that the phenomenon is caused by coinfection of soilborne pathogens and CGMMV. A field survey showed that 69% of the collapsed plants were infected with both Pythium spp. and CGMMV, whereas only 20 and 6.6% were singly infected with Pythium spp. or CGMMV, respectively. Artificial inoculations in controlled-environmental growth chambers and glasshouse experiments showed that coinfection with Pythium spinosum and CGMMV leads to a strong synergistic wilting effect and reduces growth parameters. The synergy values of the wilting effect were not influenced by the time interval between P. spinosum and CGMMV infection. However, dry mass synergy values were decreased with longer intervals between infections. The results obtained in this study support the complexity of the wilting phenomenon described in commercial cucumber grown in protected structures during infection of Pythium spp. on the background of a vast CGMMV epidemic. They encourage a wider perspective of the complexity of agricultural diseases to apply the most suitable disease management.


Assuntos
Cucumis sativus/microbiologia , Doenças das Plantas/microbiologia , Pythium/fisiologia , Tobamovirus/fisiologia , Coinfecção
13.
Plant Dis ; 102(1): 67-72, 2018 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-30673446

RESUMO

Several studies have shown that mixtures of plant-growth-promoting rhizobacteria (PGPR) could enhance biological control activity for multiple plant diseases through the mechanisms of induced systemic resistance or antagonism. Prior experiments showed that four individual PGPR strains-AP69 (Bacillus altitudinis), AP197 (B. velezensis), AP199 (B. velezensis), and AP298 (B. velezensis)-had broad-spectrum biocontrol activity via antagonism in growth chambers against two foliar bacterial pathogens (Xanthomonas axonopodis pv. vesicatoria and Pseudomonas syringae pv. tomato) and one of two tested soilborne fungal pathogens (Rhizoctonia solani and Pythium ultimum). Based on these findings, the overall hypothesis of this study was that a mixture of two individual PGPR strains would exhibit better overall biocontrol and plant-growth promotion than the individual PGPR strains. Two separate greenhouse experiments were conducted. In each experiment, two individual PGPR strains and their mixtures were tested for biological control of three different diseases and for plant-growth promotion in the presence of the pathogens. The results demonstrated that the two individual PGPR strains and their mixtures exhibited both biological control of multiple plant diseases and plant-growth promotion. Overall, the levels of disease suppression and growth promotion were greater with mixtures than with individual PGPR strains.


Assuntos
Bacillus/química , Agentes de Controle Biológico/química , Capsicum/microbiologia , Cucumis sativus/microbiologia , Lycopersicon esculentum/microbiologia , Controle Biológico de Vetores , Doenças das Plantas/prevenção & controle , Pseudomonas syringae/fisiologia , Pythium/fisiologia , Rhizoctonia/fisiologia , Xanthomonas axonopodis/fisiologia
14.
Plant Dis ; 102(7): 1357-1364, 2018 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-30673570

RESUMO

Hydroponic culture systems are subject to high risks of diseases caused by zoosporic plant pathogens. Control is generally difficult because of the rapid spread of zoospores in the nutrient solutions. In Japan, tomato and eustoma, which are cultivated using the D-tray and nutrient film techniques, respectively, are susceptible to diseases caused by Pythium aphanidermatum and P. irregulare. We used loop-mediated isothermal amplification to identify potential contamination sources of these two pathogens by monitoring their presence in the water supply wells, seedling terraces, nutrient solutions, diseased plants, and ground soils of a tomato greenhouse complex and a eustoma greenhouse complex. The results indicated that the pathogens may enter the culture systems from the soils around the greenhouses. Entry most likely occurs when seedlings are moved from the seedling terraces to the greenhouses, and sterilization of the hydroponic systems may not be sufficient. Therefore, monitoring pathogens in the culture systems and ground soils is very important for the management and prevention of these diseases.


Assuntos
Gentianaceae/microbiologia , Lycopersicon esculentum/microbiologia , Técnicas de Amplificação de Ácido Nucleico/métodos , Doenças das Plantas/microbiologia , Pythium/genética , Pythium/fisiologia , Meios de Cultura/análise , DNA Fúngico/genética , Ambiente Controlado , Água Doce/microbiologia , Interações Hospedeiro-Patógeno , Hidroponia/métodos , Doenças das Plantas/prevenção & controle , Raízes de Plantas/microbiologia , Pythium/classificação , Estações do Ano , Plântula/microbiologia , Microbiologia do Solo
15.
BMC Genomics ; 18(1): 764, 2017 Oct 10.
Artigo em Inglês | MEDLINE | ID: mdl-29017458

RESUMO

BACKGROUND: How pathogen genomes evolve to support distinct lifestyles is not well-understood. The oomycete Phytophthora infestans, the potato blight agent, is a largely biotrophic pathogen that feeds from living host cells, which become necrotic only late in infection. The related oomycete Pythium ultimum grows saprophytically in soil and as a necrotroph in plants, causing massive tissue destruction. To learn what distinguishes their lifestyles, we compared their gene contents and expression patterns in media and a shared host, potato tuber. RESULTS: Genes related to pathogenesis varied in temporal expression pattern, mRNA level, and family size between the species. A family's aggregate expression during infection was not proportional to size due to transcriptional remodeling and pseudogenization. Ph. infestans had more stage-specific genes, while Py. ultimum tended towards more constitutive expression. Ph. infestans expressed more genes encoding secreted cell wall-degrading enzymes, but other categories such as secreted proteases and ABC transporters had higher transcript levels in Py. ultimum. Species-specific genes were identified including new Pythium genes, perforins, which may disrupt plant membranes. Genome-wide ortholog analyses identified substantial diversified expression, which correlated with sequence divergence. Pseudogenization was associated with gene family expansion, especially in gene clusters. CONCLUSION: This first large-scale analysis of transcriptional divergence within oomycetes revealed major shifts in genome composition and expression, including subfunctionalization within gene families. Biotrophy and necrotrophy seem determined by species-specific genes and the varied expression of shared pathogenicity factors, which may be useful targets for crop protection.


Assuntos
Perfilação da Expressão Gênica , Phytophthora infestans/genética , Phytophthora infestans/fisiologia , Pythium/genética , Pythium/fisiologia , Solanum tuberosum/parasitologia , Transcrição Genética , Sequência Conservada , Ontologia Genética , Especificidade de Hospedeiro , Interações Hospedeiro-Parasita/genética , Estilo de Vida , Tubérculos/parasitologia
16.
BMC Res Notes ; 10(1): 376, 2017 Aug 10.
Artigo em Inglês | MEDLINE | ID: mdl-28807055

RESUMO

BACKGROUND: Few studies to date report the transcriptional response of biocontrol bacteria toward phytopathogens. In order to gain insights into the potential mechanism underlying the antagonism of the antimicrobial producing strain P. fluorescens In5 against the phytopathogens Rhizoctonia solani and Pythium aphanidermatum, global RNA sequencing was performed. METHODS: Differential gene expression profiling of P. fluorescens In5 in response to either R. solani or P. aphanidermatum was investigated using transcriptome sequencing (RNA-seq). Total RNA was isolated from single bacterial cultures of P. fluorescens In5 or bacterial cultures in dual-culture for 48 h with each pathogen in biological triplicates. RNA-seq libraries were constructed following a default Illumina stranded RNA protocol including rRNA depletion and were sequenced 2 × 100 bases on Illumina HiSeq generating approximately 10 million reads per sample. RESULTS: No significant changes in global gene expression were recorded during dual-culture of P. fluorescens In5 with any of the two pathogens but rather each pathogen appeared to induce expression of a specific set of genes. A particularly strong transcriptional response to R. solani was observed and notably several genes possibly associated with secondary metabolite detoxification and metabolism were highly upregulated in response to the fungus. A total of 23 genes were significantly upregulated and seven genes were significantly downregulated with at least respectively a threefold change in expression level in response to R. solani compared to the no fungus control. In contrast, only one gene was significantly upregulated over threefold and three transcripts were significantly downregulated over threefold in response to P. aphanidermatum. Genes known to be involved in synthesis of secondary metabolites, e.g. non-ribosomal synthetases and hydrogen cyanide were not differentially expressed at the time points studied. CONCLUSION: This study demonstrates that genes possibly involved in metabolite detoxification are highly upregulated in P. fluorescens In5 when co-cultured with plant pathogens and in particular the fungus R. solani. This highlights the importance of studying microbe-microbe interactions to gain a better understanding of how different systems function in vitro and ultimately in natural systems where biocontrol agents can be used for the sustainable management of plant diseases.


Assuntos
Antibiose/genética , Perfilação da Expressão Gênica/métodos , Pseudomonas fluorescens/genética , Pseudomonas fluorescens/fisiologia , Rhizoctonia/fisiologia , Regulação Bacteriana da Expressão Gênica , Genes Bacterianos/genética , Doenças das Plantas/microbiologia , Pythium/fisiologia
17.
Nat Commun ; 8: 15472, 2017 06 07.
Artigo em Inglês | MEDLINE | ID: mdl-28589950

RESUMO

Fungal-bacterial interactions are highly diverse and contribute to many ecosystem processes. Their emergence under common environmental stress scenarios however, remains elusive. Here we use a synthetic microbial ecosystem based on the germination of Bacillus subtilis spores to examine whether fungal and fungal-like (oomycete) mycelia reduce bacterial water and nutrient stress in an otherwise dry and nutrient-poor microhabitat. We find that the presence of mycelia enables the germination and subsequent growth of bacterial spores near the hyphae. Using a combination of time of flight- and nanoscale secondary ion mass spectrometry (ToF- and nanoSIMS) coupled with stable isotope labelling, we link spore germination to hyphal transfer of water, carbon and nitrogen. Our study provides direct experimental evidence for the stimulation of bacterial activity by mycelial supply of scarce resources in dry and nutrient-free environments. We propose that mycelia may stimulate bacterial activity and thus contribute to sustaining ecosystem functioning in stressed habitats.


Assuntos
Bacillus subtilis/fisiologia , Ecossistema , Micélio/fisiologia , Água/metabolismo , Bacillus subtilis/citologia , Bacillus subtilis/efeitos dos fármacos , Bacillus subtilis/crescimento & desenvolvimento , Basidiomycota/fisiologia , Carbono/farmacologia , Fusarium/fisiologia , Isótopos , Micélio/efeitos dos fármacos , Nitrogênio/farmacologia , Pythium/fisiologia , Espectrometria de Massa de Íon Secundário , Esporos Bacterianos/efeitos dos fármacos , Esporos Bacterianos/crescimento & desenvolvimento
18.
Microb Ecol ; 74(3): 550-560, 2017 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-28386770

RESUMO

Associations between soil properties and Pythium groups on soybean roots were investigated in 83 commercial soybean fields in North Dakota. A data set containing 2877 isolates of Pythium which included 26 known spp. and 1 unknown spp. and 13 soil properties from each field were analyzed. A Pearson correlation analysis was performed with all soil properties to observe any significant correlation between properties. Hierarchical clustering, indicator spp., and multi-response permutation procedures were used to identify groups of Pythium. Logistic regression analysis using stepwise selection was employed to calculate probability models for presence of groups based on soil properties. Three major Pythium groups were identified and three soil properties were associated with these groups. Group 1, characterized by P. ultimum, was associated with zinc levels; as zinc increased, the probability of group 1 being present increased (α = 0.05). Pythium group 2, characterized by Pythium kashmirense and an unknown Pythium sp., was associated with cation exchange capacity (CEC) (α < 0.05); as CEC increased, these spp. increased. Group 3, characterized by Pythium heterothallicum and Pythium irregulare, were associated with CEC and calcium carbonate exchange (CCE); as CCE increased and CEC decreased, these spp. increased (α = 0.05). The regression models may have value in predicting pathogenic Pythium spp. in soybean fields in North Dakota and adjacent states.


Assuntos
Pythium/fisiologia , Microbiologia do Solo , Solo/química , Soja/microbiologia , Modelos Biológicos , North Dakota , Raízes de Plantas/microbiologia , Probabilidade
19.
Can J Microbiol ; 63(5): 411-426, 2017 May.
Artigo em Inglês | MEDLINE | ID: mdl-28178423

RESUMO

Disease suppressive composts have the potential to mitigate the risks associated with chemical pesticides. One of the main characteristics responsible for the suppressive nature of composts is their microbiological populations. To gain insight into the determinants responsible for their suppressive effects, we assayed composts to (i) isolate and identify beneficial antagonistic bacteria, (ii) quantify their antifungal and anti-oomycetal activities, (iii) extract inhibitory compounds produced by the bacteria, and (iv) identify antimicrobial lipopeptides produced by these bacteria. The antagonistic bacteria belonged to the genera Arthrobacter, Pseudomonas, Bacillus, Brevibacillus, Paenibacillus, and Rummeliibacillus and had the ability to antagonise the growth of Fusarium sambucinum, Verticillium dahliae, and (or) Pythium sulcatum. These bacteria produced antimicrobial compounds that affected the mycelial growth and (or) conidial germination of the pathogens. Mass spectrometry analyses showed the presence of various antimicrobial lipopeptides in Bacillus and Bacillus-related spp. extracts, demonstrating that they are responsible, at least in part, for the antagonistic activity of the bacteria. Results from this work provide greater insight into some of the biological, biochemical, and physiological determinants of suppressiveness in composts involved in the control of plant pathogens.


Assuntos
Doenças das Plantas/microbiologia , Plantas/microbiologia , Microbiologia do Solo , Antibacterianos/farmacologia , Antifúngicos/farmacologia , Bacillus/química , Bacillus/fisiologia , Fusarium/química , Fusarium/fisiologia , Germinação , Lipopeptídeos/farmacologia , Pythium/química , Pythium/fisiologia , Esporos Fúngicos , Verticillium/química , Verticillium/fisiologia
20.
Mol Plant Microbe Interact ; 29(12): 965-976, 2016 12.
Artigo em Inglês | MEDLINE | ID: mdl-28035839

RESUMO

Beneficial microorganisms play an important role in enhancing plant health, especially by promoting resistance to plant pathogen infection. The purpose of this study was to gain an understanding of such protection by i) examining the responses of fresh produce (lettuce) to beneficial treatments in their transcriptomes, ii) comparing biological (bacteria, fungi, and oomycete) communities and their diversity when treated with Pseudomonas chlororaphis (beneficial bacterium) in windowfarm hydroponic systems, and iii) identifying the microorganisms in root areas and water. P. chlororaphis treatment was for increasing plant growth and fighting for Pythium ultimum infection. In addition, two more treatments were conducted: i) adding supporting media for increasing bacterial colonizing areas around roots and ii) UV irradiation in water for controlling nuisance biofilm buildup. Changes in gene regulation and expression in lettuce in response to these treatments were investigated. Comparisons of microbial profiles among the treatments and microbial identification were conducted using samples of supporting media (around roots) and water. The results demonstrated that i) P. chlororaphis enhanced lettuce growth, ii) P. chlororaphis-treated lettuce showed dominantly expressed genes for membrane, catalytic activity, cellular process, and metabolic process categories, iii) P. chlororaphis treatment induced genes related to growth promotion and defense pathways, and iv) the microbial community of the root area was affected significantly by P. chlororaphis treatment and microbial diversity in water was significantly changed by UV irradiation. This study provided insight into how beneficial treatments affects the fresh produce growth in root areas and water in a vertical hydroponic system.


Assuntos
Bactérias/metabolismo , Biofilmes/crescimento & desenvolvimento , Fungos/fisiologia , Alface/genética , Consórcios Microbianos , Pseudomonas/fisiologia , Transcriptoma , Agricultura , Hidroponia , Alface/microbiologia , Raízes de Plantas/genética , Raízes de Plantas/microbiologia , Pythium/fisiologia
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