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1.
World J Microbiol Biotechnol ; 35(8): 128, 2019 Aug 02.
Artigo em Inglês | MEDLINE | ID: mdl-31375920

RESUMO

Large patch disease, caused by Rhizoctonia solani AG2-2, is the most devastating disease in Zoysiagrass (Zoysia japonica). Current large patch disease control strategies rely primarily upon the use of chemical pesticides. Streptomyces sp. S8 is known to possess exceptional antagonistic properties that could potentially suppress the large patch pathogen found at turfgrass plantations. This study aims to demonstrate the feasibility of using the strain as a biological control mechanism. Sequencing of the S8 strain genome revealed a valinomycin biosynthesis gene cluster. This cluster is composed of the vlm1 and vlm2 genes, which are known to produce antifungal compounds. In order to verify this finding for the large patch pathogen, a valinomycin biosynthesis knockout mutant was created via the CRISPR/Cas9 system. The mutant lost antifungal activity against the large patch pathogen. Consequently, it is anticipated that eco-friendly microbial preparations derived from the S8 strain can be utilized to biologically control large patch disease.


Assuntos
Antifúngicos/metabolismo , Antifúngicos/farmacologia , Rhizoctonia/efeitos dos fármacos , Streptomyces/metabolismo , Valinomicina/metabolismo , Valinomicina/farmacologia , Vias Biossintéticas/genética , Técnicas de Inativação de Genes , Genoma Bacteriano , Família Multigênica , Controle Biológico de Vetores/métodos , Doenças das Plantas/microbiologia , Doenças das Plantas/prevenção & controle , Poaceae/microbiologia , Rhizoctonia/crescimento & desenvolvimento , Análise de Sequência de DNA , Streptomyces/genética
2.
Plant Dis ; 103(10): 2612-2623, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31408402

RESUMO

Symptoms of Fusarium crown rot of wheat include premature death of inflorescens (whiteheads), lesions on subcrown internodes, and rotting of crown tissue and lower stem internodes. Each symptom type is influenced by a different set of environmental conditions. Whiteheads are the easiest symptom to quantify and are frequently reported in the Pacific Northwest U.S.A. The objective of this research was to examine factors associated with whitehead expression and relationships with wheat yield and test weight. Incidence of whiteheads differed for inoculations with different isolates of F. pseudograminearum and F. culmorum, and over years due to weather factors. Whiteheads became less as planting dates for winter wheat were delayed until after September, and incidence was increased with increasing nitrogen application rate. Dates of initial and greatest expression of whiteheads differed among cultivars, which was associated in part with the cultivar heading date. Whiteheads were not correlated with subcrown internode lesions or browning of crown tissue. Whiteheads were also not correlated with grain test weight. Whiteheads were sometimes negatively associated with grain yield, but that relationship was variable and could not be considered a reliable, recurrent, or accurate measure of crown rot severity. These results indicate the need for caution in reporting whiteheads as a sole indicator of cultivar susceptibility to Fusarium crown rot.


Assuntos
Agricultura , Fusarium , Doenças das Plantas , Triticum , Agricultura/métodos , Grão Comestível/microbiologia , Fusarium/fisiologia , Noroeste dos Estados Unidos , Doenças das Plantas/prevenção & controle , Triticum/microbiologia
3.
Plant Dis ; 103(10): 2498-2504, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31453746

RESUMO

Downy mildew is a yield-limiting disease of sunflower, caused by the pathogen Plasmopara halstedii. Zoospore infection of root tissue shortly after planting results in systemic infection, causing postemergence damping off or severe stunting and head sterility. Although fungicide-applied seed treatments can be an effective management tool, the pathogen is resistant to phenylamide fungicides in many growing regions, and other available fungicides have limited efficacy. Oxathiapiprolin, the first member of the piperidinyl thiazole isoxazoline fungicides, was evaluated for efficacy on downy mildew in field trials conducted from 2011 to 2015 in North Dakota. Throughout the course of the study, the rate range was narrowed from active ingredient (a.i.) at 0.45 to 116.0 µg a.i. seed-1 to an optimal effective rate of 9.37 to 18.75 µg a.i. seed-1. Within that optimal range, the downy mildew incidence of sunflower planted with oxathiapiprolin-treated seed was significantly lower than the incidence in the nontreated sunflower in all 11 trials with disease pressure. Additionally, downy mildew incidence of sunflower planted with oxathiapiprolin-treated seed was significantly lower than sunflower planted with competitive commercially available fungicide-treated seed in 10 of those 11 trials. The use of oxathiapiprolin by sunflower growers is likely to reduce disease incidence and subsequent yield loss to downy mildew.


Assuntos
Helianthus , Hidrocarbonetos Fluorados , Oomicetos , Doenças das Plantas , Pirazóis , Antiparasitários/farmacologia , Helianthus/parasitologia , Hidrocarbonetos Fluorados/farmacologia , North Dakota , Oomicetos/efeitos dos fármacos , Doenças das Plantas/parasitologia , Doenças das Plantas/prevenção & controle , Pirazóis/farmacologia , Sementes/química
4.
Plant Dis ; 103(9): 2184-2190, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31287372

RESUMO

Little cherry disease (LCD) threatens the long-term economic sustainability of the Pacific Northwest sweet cherry (Prunus avium) industry. Results from a series of partial budget analyses indicate that additional investments in monitoring, testing, spraying to control for insect vectors, and removing infected trees are lower than the reduced profit losses compared with the do-nothing scenario. Also, management can prevent or lessen the negative impacts of higher little cherry virus (Velarivirus little cherry virus 1, Ampelovirus little cherry virus 2) spread rates. Our findings illustrate the importance of prevention, correct identification, and controlling for insect vectors in preventing the dissemination of LCD, for which the only known treatment is tree removal.


Assuntos
Agricultura , Closteroviridae , Doenças das Plantas , Prunus avium , Agricultura/métodos , Animais , Closteroviridae/fisiologia , Frutas , Controle de Insetos , Insetos Vetores/fisiologia , Doenças das Plantas/prevenção & controle , Prunus avium/virologia , Washington
5.
Plant Dis ; 103(9): 2433-2442, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31306093

RESUMO

Postbloom fruit drop (PFD) of citrus, caused by Colletotrichum acutatum sensu lato and C. gloeosporioides sensu lato, is an important disease in the humid tropics of the American continent. PFD mainly affects flowers, on which typical symptoms are characterized by orange-brown lesions with presence of acervuli. The disease has a sporadic occurrence, but preventative fungicide sprays are applied every season. The objective of this study was to evaluate the effectiveness of a fungicide spray strategy for PFD based on a predictive model of C. acutatum conidium germination linked to weather conditions. Fungicide sprays were performed when the model predicted pre-established thresholds of 10, 15, 20, and 25% of germinated spores (T10, T15, T20, and T25, respectively). Five experiments were conducted in two different seasons in the state of São Paulo, Brazil. PFD control efficacy of the threshold-based treatments was compared with a nontreated control and to a calendar-based spray system. Additionally, an economic analysis was performed to assess the gross income revenues of the fungicide spraying strategies. Disease control in plots treated at T10, T15, and T20 was as effective as the calendar-based strategy. The number of fungicide applications was reduced by 33 to 71% when sprays were applied at T15 and T20, and gross income increased or was comparable to that of the other treatments. Therefore, using a conidium germination model with a threshold of 15 or 20% is recommended as a spraying strategy for PFD management in Brazil.


Assuntos
Citrus , Fungicidas Industriais , Doenças das Plantas , Brasil , Citrus/microbiologia , Frutas/microbiologia , Fungicidas Industriais/economia , Doenças das Plantas/economia , Doenças das Plantas/microbiologia , Doenças das Plantas/prevenção & controle
6.
Plant Dis ; 103(9): 2212-2220, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31306094

RESUMO

White mold, caused by Sclerotinia sclerotiorum, is a yield-limiting disease of soybean in Brazil. Uniform fungicide trials have been conducted annually since 2009. Data from 74 cooperative field trials conducted over a 10-year period were assembled. We selected five fungicides applied two times around flowering: dimoxystrobin plus boscalid (DIMO+BOSC), carbendazim plus procymidone (CARB+PROC), fluazinam (FLUZ), fluopyram (FLUO), and procymidone (PROC). For comparison, thiophanate-methyl (TMET) applied four times was also included as a low-cost treatment. Network models were fitted to the log of white mold incidence (percentages) and log of sclerotia mass data (grams/hectare) and to the nontransformed yield data (kilograms/hectare) for each treatment, including the untreated check. Back-transformation of the meta-analytic estimates indicated that the lowest and highest mean (95% confidence interval [CI]) percent reductions in incidence and sclerotia mass were 54.2 (49.3 to 58.7) and 51.6% (43.7 to 58.3) for TMET and 83.8 (79.1 to 87.5) and 87% (81.9 to 91.6) for CARB+PROC, respectively. The overall mean (95% CI) yield responses ranged from 323 kg/ha (247.4 to 400.3) for TMET to 626 kg/ha (521.7 to 731.7) for DIMO+BOSC, but the variance was significantly reduced by a binary variable (30% threshold) describing disease incidence in the untreated check. On average, an increment of 352 kg/ha was estimated for trials where the incidence was >30% compared with the low-disease scenario. Hence, the probability of breaking even on fungicide costs for the high-disease scenario was >65% for the more effective, but more expensive fungicide (FLUZ) than TMET. For the low-disease scenario, profitability was less likely and depended more on variations in fungicide cost and soybean price.


Assuntos
Ascomicetos , Fungicidas Industriais , Doenças das Plantas , Soja , Agricultura , Ascomicetos/efeitos dos fármacos , Brasil , Fungicidas Industriais/economia , Fungicidas Industriais/farmacologia , Fungicidas Industriais/normas , Doenças das Plantas/prevenção & controle , Soja/microbiologia
7.
Plant Dis ; 103(9): 2460-2466, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31322492

RESUMO

The intensive use of fungicides in controlling soybean rust (SBR), a damaging foliar fungal disease of soybean caused by the obligate fungus Phakopsora pachyrhizi, may have accelerated the insensitivity of P. pachyrhizi populations to fungicides. The objective of this study was to determine the effect of selected biopesticides and their application time on reducing SBR infection. There were differences (P < 0.05) in percent rust reduction values for application times, biopesticide treatments, and their interaction in detached-leaf and whole-plant greenhouse experiments. All application times and nearly all biopesticide treatments reduced (α = 0.05) fungal infection compared with the nonfungicide control. Among the treatments, Bacillus subtilis QST 713 and acibenzolar-S-methyl often reduced fungal sporulation more than the other treatments in detached-leaf and whole-plant greenhouse experiments. The identification of biopesticides effective to P. pachyrhizi may be a valuable alternative or complement to synthetic fungicides and may be useful in integrated pest management programs for SBR control.


Assuntos
Agentes de Controle Biológico , Phakopsora pachyrhizi , Doenças das Plantas , Soja , Phakopsora pachyrhizi/fisiologia , Doenças das Plantas/microbiologia , Doenças das Plantas/prevenção & controle , Soja/microbiologia
8.
Plant Dis ; 103(9): 2179-2183, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31322494

RESUMO

Potato virus Y (PVY) is among the most economically impactful potato pathogens, yet the spread of PVY from infected seed potatoes within commercial potato fields has not been adequately studied. Test lots containing various seed-borne PVY levels were created by mixing different proportions of seed pieces from healthy and infected tubers drawn from the same seed source. These seed lots were planted in commercial potato fields near the Teton Seed Potato Management Area from 2010 to 2012. Regression analyses on data from these test plots produced models of the in-season spread of PVY originating from infected seed. Conventional ordinary least squares techniques were supplemented with the use of quantile regression; the resulting models indicate the significance of seed-borne PVY on end-of-season infection levels and highlight the need of seed potato buyers to review postharvest testing results.


Assuntos
Doenças das Plantas , Tubérculos , Potyvirus , Solanum tuberosum , Agricultura , Doenças das Plantas/prevenção & controle , Doenças das Plantas/virologia , Tubérculos/virologia , Solanum tuberosum/virologia
9.
Plant Dis ; 103(9): 2153-2170, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31343378

RESUMO

The ready-to-eat salad sector, also called fresh-cut or bagged salads, is a fast-growing segment of the fresh-food industry. The dynamism and specialization of this sector, together with the lack of adequate crop rotation, the globalization of the seed market, and climate change, are the main causes of the development of many new diseases that cause severe production losses. Newly detected diseases of the most important crops grown (lettuce, wild and cultivated rocket, lamb's lettuce, chicory, endive, basil, spinach, and Swiss chard) are critically discussed. The management of these diseases represents a formidable challenge, since few fungicides are registered on these minor-use crops. An interesting feature of the ready-to-eat salad sector is that most crops are grown under protection, often in soilless systems, which provide an environment helpful to the implementation of innovative control methods. Current trends in disease management are discussed, with special focus on the most sustainable practices.


Assuntos
Produtos Agrícolas , Alface , Doenças das Plantas , Verduras , Agricultura/normas , Agricultura/tendências , Produtos Agrícolas/microbiologia , Alface/microbiologia , Alface/normas , Ocimum basilicum , Doenças das Plantas/prevenção & controle , Valerianella , Verduras/microbiologia
10.
J Agric Food Chem ; 67(33): 9265-9276, 2019 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-31361479

RESUMO

Fungal infections significantly alter the emissions of volatile organic compounds (VOCs) by plants, but the mechanisms for VOCs affecting fungal infections of plants remain largely unknown. Here, we found that infection by Botrytis cinerea upregulated linalool production by strawberries and fumigation with linalool was able to inhibit the infection of fruits by the fungus. Linalool treatment downregulated the expression of rate-limiting enzymes in the ergosterol biosynthesis pathway, and this reduced the ergosterol content in the fungi cell membrane and impaired membrane integrity. Linalool treatment also caused damage to mitochondrial membranes by collapsing mitochondrial membrane potential and also downregulated genes involved in adenosine triphosphate (ATP) production, resulting in a significant decrease in the ATP content. Linalool treatment increased the levels of reactive oxygen species (ROS), in response to which the treated fungal cells produced more of the ROS scavenger pyruvate. RNA-Seq and proteomic analysis data showed that linalool treatment slowed the rates of transcription and translation.


Assuntos
Botrytis/efeitos dos fármacos , Fragaria/metabolismo , Frutas/microbiologia , Monoterpenos/metabolismo , Doenças das Plantas/microbiologia , Compostos Orgânicos Voláteis/metabolismo , Trifosfato de Adenosina/metabolismo , Botrytis/crescimento & desenvolvimento , Fragaria/química , Fragaria/microbiologia , Frutas/química , Frutas/metabolismo , Interações Hospedeiro-Patógeno , Membranas Mitocondriais/efeitos dos fármacos , Membranas Mitocondriais/metabolismo , Monoterpenos/farmacologia , Doenças das Plantas/prevenção & controle , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Proteômica , Espécies Reativas de Oxigênio/metabolismo , Compostos Orgânicos Voláteis/farmacologia
11.
Plant Dis ; 103(10): 2592-2598, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31347987

RESUMO

The objective of this study was to evaluate fungicide applications, host resistance, and trellising, alone and in combination, as management practices for downy mildew on slicing cucumber. A split-split plot experimental design was used with three and four replications in spring and fall 2017, respectively. The whole-plot treatment was fungicide, four applications of chlorothalonil (Bravo Weather Stik 6SC) alternated with three applications of cyazofamid (Ranman 400SC), or water. Split plots were nontrellised or trellised with four strings supported by stakes. Split-split plots were cultivar Bristol, which is intermediately resistant to downy mildew, or cultivar Speedway, which is susceptible to downy mildew with similar parentage as Bristol. In both seasons, area under the disease progress curve (AUDPC) values were lower with fungicides than water for both cultivars. In the spring, AUDPC for Bristol was lower than for Speedway regardless of fungicide treatment. In the fall, Bristol had a lower AUDPC than Speedway with fungicides, but the AUDPC did not differ between the two cultivars with water. The mean AUDPC for trellised plants (376.2) was lower than for nontrellised plants (434.0; P = 0.007). Fungicide applications increased marketable and total fruit weights in both seasons (P ≤ 0.0002). Marketable weight with fungicides was almost double (93% greater) the marketable weight with water. Marketable weight was 55% greater for Bristol than for Speedway in spring, but yields did not differ between cultivars in fall (season-by-cultivar interaction, P ≤ 0.0003). Because trellising had no effect on marketable yields (P = 0.11), trellising is not recommended for managing downy mildew on slicing cucumber. Of the three management techniques examined, fungicides had the largest effects on disease and yields, followed by cultivar resistance.


Assuntos
Agricultura/métodos , Cucumis sativus , Resistência à Doença , Fungicidas Industriais , Oomicetos , Cucumis sativus/microbiologia , Cucumis sativus/fisiologia , Fungicidas Industriais/farmacologia , Oomicetos/efeitos dos fármacos , Oomicetos/fisiologia , Doenças das Plantas/prevenção & controle
12.
Microbiol Res ; 226: 1-9, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31284938

RESUMO

Citrus crops have great economic importance worldwide. However, citrus production faces many diseases caused by different pathogens, such as bacteria, oomycetes, fungi and viruses. To overcome important plant diseases in general, new technologies have been developed and applied to crop protection, including RNA interference (RNAi) and clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated (Cas) systems. RNAi has been demonstrated to be a powerful tool for application in plant defence mechanisms against different pathogens as well as their respective vectors, and CRISPR/Cas system has become widely used in gene editing or reprogramming or knocking out any chosen DNA/RNA sequence. In this article, we provide an overview of the use of RNAi and CRISPR/Cas technologies in management strategies to control several plants diseases, and we discuss how these strategies can be potentially used against citrus pathogens.


Assuntos
Citrus/genética , Repetições Palindrômicas Curtas Agrupadas e Regularmente Espaçadas , Doenças das Plantas/genética , Doenças das Plantas/prevenção & controle , Interferência de RNA , Bactérias/genética , Bactérias/patogenicidade , Sistemas CRISPR-Cas , Citrus/microbiologia , Produtos Agrícolas , Fungos/genética , Fungos/patogenicidade , Edição de Genes/métodos , Engenharia Genética , Vírus/genética , Vírus/patogenicidade
13.
Microbiol Res ; 226: 41-47, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31284943

RESUMO

Myzus persicae Sulzer (Hemiptera: Aphididae), is a generalist cosmopolitan insect that infests more than 400 plant species of 40 different families and is one of the major pests infesting potato crops. It causes direct damage and also spread plant viruses. The intensive use of synthetic insecticide to control aphids has led to resistant populations. Therefore, there is a need to develop biopesticides for effective control that minimizes environmental hazards. The bacteria Bacillus amyloliquefaciens is recognized as a producer of a variety of bioactive compounds. The aim here was to evaluate the aphicidal effect of B. amyloliquefaciens strains, CBMDDrag3, PGPBacCA2, and CBMDLO3, and their metabolites on the mortality and fecundity of M. persicae. Cells suspensions, heat-killed cell suspensions, cell-free supernatants, or isolated lipopeptide fractions from B. amyloliquefaciens strains were offered to aphids through artificial diets. The isolated lipopeptide fractions composed mainly of kurstakins, surfactins, iturins, and fengycins, when were administrated through diets, had no aphicidal effect against M. persicae. However, aphids fed on diets with whole cell suspensions and its cell-free supernatant of all three bacteria strains resulted in 100% mortality of adult aphids and nymphs. Specially, B. amyloliquefaciens CBMDLO3, has an effective aphicidal effect on M. persicae, used both bacterial cells and their metabolites. Moreover, heat-killed cells of B. amyloliquefaciens CBMDLO3 also had aphicidal action, although the aphid mortality was lower than on diet with living bacteria. Therefore, these results propose that B. amyloliquefaciens, could function as a novel eco-friendly biopesticide for the control of M. persicae.


Assuntos
Afídeos/efeitos dos fármacos , Afídeos/microbiologia , Bacillus amyloliquefaciens/metabolismo , Controle Biológico de Vetores , Animais , Bacillus amyloliquefaciens/isolamento & purificação , Agentes de Controle Biológico/isolamento & purificação , Agentes de Controle Biológico/metabolismo , Agentes de Controle Biológico/farmacologia , Feminino , Controle de Insetos/métodos , Inseticidas/isolamento & purificação , Inseticidas/metabolismo , Inseticidas/farmacologia , Lipopeptídeos/isolamento & purificação , Lipopeptídeos/metabolismo , Lipopeptídeos/farmacologia , Doenças das Plantas/parasitologia , Doenças das Plantas/prevenção & controle
14.
Phytopathology ; 109(7): 1198-1207, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31166155

RESUMO

Epidemiological models are increasingly used to predict epidemics and improve management strategies. However, they rarely consider landscape characteristics although such characteristics can influence the epidemic dynamics and, thus, the effectiveness of disease management strategies. Here, we present a generic in silico approach which assesses the influence of landscape aggregation on the costs associated with an epidemic and on improved management strategies. We apply this approach to sharka, one of the most damaging diseases of Prunus trees, for which a management strategy is already applied in France. Epidemic simulations were carried out with a spatiotemporal stochastic model under various management strategies in landscapes differing in patch aggregation. Using sensitivity analyses, we highlight the impact of management parameters on the economic output of the model. We also show that the sensitivity analysis can be exploited to identify several strategies that are, according to the model, more profitable than the current French strategy. Some of these strategies are specific to a given aggregation level, which shows that management strategies should generally be tailored to each specific landscape. However, we also identified a strategy that is efficient for all levels of landscape aggregation. This one-size-fits-all strategy has important practical implications because of its simple applicability at a large scale.


Assuntos
Doenças das Plantas , Prunus , Produtos Agrícolas , França , Doenças das Plantas/prevenção & controle , Prunus/virologia , Árvores
15.
J Agric Food Chem ; 67(25): 6970-6977, 2019 Jun 26.
Artigo em Inglês | MEDLINE | ID: mdl-31150237

RESUMO

Huanglongbing (HLB), also known as citrus greening, is a bacterial disease that poses a devastating threat to the citrus industry worldwide. To manage this disease efficiently, we developed and characterized a ternary aqueous solution (TSOL) that contains zinc nitrate, urea, and hydrogen peroxide. We report that TSOL exhibits better antimicrobial activity than commercial bactericides for growers. X-ray fluorescence analysis demonstrates that zinc is delivered to citrus leaves, where the bacteria reside. FTIR and Raman spectroscopy, molecular dynamics simulations, and density functional theory calculations elucidate the solution structure of TSOL and reveal a water-mediated interaction between Zn2+ and H2O2, which may facilitate the generation of highly reactive hydroxyl radicals contributing to superior antimicrobial activity of TSOL. Our results not only suggest TSOL as a potent antimicrobial agent to suppress bacterial growth in HLB-infected trees, but also provide a structure-property relationship that explains the superior performance of TSOL.


Assuntos
Antibacterianos/química , Antibacterianos/farmacologia , Citrus/microbiologia , Nitratos/química , Nitratos/farmacologia , Doenças das Plantas/prevenção & controle , Rhizobiaceae/fisiologia , Compostos de Zinco/química , Compostos de Zinco/farmacologia , Peróxido de Hidrogênio/química , Peróxido de Hidrogênio/farmacologia , Doenças das Plantas/microbiologia , Folhas de Planta/microbiologia , Rhizobiaceae/efeitos dos fármacos , Espectroscopia de Infravermelho com Transformada de Fourier , Análise Espectral Raman , Relação Estrutura-Atividade , Ureia/química , Ureia/farmacologia
16.
Food Chem ; 293: 263-270, 2019 Sep 30.
Artigo em Inglês | MEDLINE | ID: mdl-31151610

RESUMO

Gray mold caused by Botrytis cinerea is the most important disease in postharvest tomato fruit. Inducing resistance to fungal pathogens in the harvested fruit and vegetable is a promising approach to control postharvest losses. In the present study, the effect of l-glutamate on induction of resistance to B. cinerea and the underlying mechanisms were investigated. The results indicated that l-glutamate at 100 ppm was effective in reducing the gray mold of tomatoes after inoculation of the pathogen. Gene expressions of nine glutamate receptors, four pathogenesis-related proteins and the content of amino acids were affected by l-glutamate treatment. Furthermore, the metabolites of l-glutamate, including GABA, Met, Lys and Arg, could also induce significant resistance against B. cinerea in tomato fruit. Our findings suggested that l-glutamate treatment may represent a promising method for managing postharvest decay of tomato fruit.


Assuntos
Aminoácidos/metabolismo , Botrytis/efeitos dos fármacos , Ácido Glutâmico/farmacologia , Lycopersicon esculentum/imunologia , Micoses/prevenção & controle , Doenças das Plantas/prevenção & controle , Receptores de Glutamato/metabolismo , Resistência à Doença , Frutas/química , Lycopersicon esculentum/genética , Lycopersicon esculentum/microbiologia , Micoses/microbiologia , Doenças das Plantas/microbiologia , Proteínas de Plantas/genética , Regulação para Cima/efeitos dos fármacos
17.
J Agric Food Chem ; 67(27): 7738-7747, 2019 Jul 10.
Artigo em Inglês | MEDLINE | ID: mdl-31199650

RESUMO

Cytosinpeptidemycin (CytPM) is a microbial pesticide that displayed broad-spectrum antiviral activity against various plant viruses. However, the molecular mechanism underlying antiviral activity of CytPM is poorly understood. In this study, the results demonstrated that CytPM could effectively delay the systemic infection of tobacco mosaic virus (TMV) in Nicotiana benthamiana and significantly inhibit the viral accumulation in tobacco BY-2 protoplasts. Results of RNA-seq indicated that 210 and 120 differential expressed genes (DEGs) were significantly up- and down-regulated after CytPM treatment in BY-2 protoplasts, respectively. In addition, KEGG analysis indicated that various DEGs were involved in endoplasmic reticulum (ER) protein processing, suggesting a possible correlation between ER homeostasis and virus resistance. RT-qPCR was performed to validate the gene expression of crucial DEGs related with defense, stress responses, signaling transduction, and phytohormone, which were consistent with results of RNA-seq. Our works provided valuable insights into the antiviral mechanism of CytPM that induced host resistance to viral infection.


Assuntos
Antivirais , Citosina/análogos & derivados , Resistência à Doença/genética , Doenças das Plantas/prevenção & controle , Vírus do Mosaico do Tabaco/fisiologia , Tabaco/virologia , Citosina/farmacologia , Resistência à Doença/efeitos dos fármacos , Expressão Gênica , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Interações Hospedeiro-Patógeno/efeitos dos fármacos , Interações Hospedeiro-Patógeno/genética , Doenças das Plantas/virologia , Reguladores de Crescimento de Planta/genética , Protoplastos/efeitos dos fármacos , Protoplastos/virologia , Transdução de Sinais/efeitos dos fármacos , Estresse Fisiológico/efeitos dos fármacos , Estresse Fisiológico/genética , Tabaco/genética , Vírus do Mosaico do Tabaco/efeitos dos fármacos , Vírus do Mosaico do Tabaco/patogenicidade
18.
Plant Dis ; 103(8): 1991-1997, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31169087

RESUMO

Gray mold caused by Botrytis cinerea can be a severe disease of tomato infecting leaves and fruits of tomato plants. Chemical control is currently the most effective and reliable method; however, application of fungicides has many drawbacks. The combination of biological control agents with newly developed fungicides may be a practicable method to control B. cinerea. Fluopimomide is a newly developed fungicide with a novel mode of action. Bacillus methylotrophicus TA-1, isolated from rhizosphere soil of tomato, is a bacterial strain with a broad spectrum of antimicrobial activities. Little information is currently available about the effect of fluopimomide and its integrated effect on B. cinerea. Therefore, laboratory, pot, and field experiments were carried out to determine the effects of fluopimomide alone and in combination with B. methylotrophicus TA-1 against gray mold on tomato. The in vitro growth of B. methylotrophicus TA-1 was unaffected by 100 mg liter-1 fluopimomide. Inhibition of B. cinerea mycelial growth was significantly increased under combined treatment of fluopimomide and B. methylotrophicus TA-1. In greenhouse experiments, efficacy against gray mold was significantly greater by an integration of fluopimomide and B. methylotrophicus TA-1 than by either alone; control efficacy of fluopimomide at 50 and 100 g ha-1 in combination with B. methylotrophicus TA-1 at 108 colony-forming units (cfu) ml-1 reached 70.16 and 69.32%, respectively, compared with the untreated control. In both field trials during 2017 and 2018, control efficacy was significantly higher for the combination of fluopimomide at 50 and 100 g ha-1 in combination with B. methylotrophicus TA-1 than for either treatment alone. The results from this study indicated that integration of the new fungicide fluopimomide with the biocontrol agent B. methylotrophicus TA-1 synergistically increased control efficacy of the fungicide against gray mold of tomato.


Assuntos
Bacillus , Botrytis , Fungicidas Industriais , Lycopersicon esculentum , Doenças das Plantas , Bacillus/fisiologia , Botrytis/efeitos dos fármacos , Botrytis/fisiologia , Fungicidas Industriais/farmacologia , Lycopersicon esculentum/microbiologia , Doenças das Plantas/microbiologia , Doenças das Plantas/prevenção & controle
19.
Plant Dis ; 103(8): 1828-1834, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31184971

RESUMO

Red needle cast is a significant foliar disease of commercial stands of Pinus radiata caused by Phytophthora pluvialis in New Zealand. The effect of copper, applied as a foliar spray of cuprous oxide at a range of doses between 0 and 1.72 kg ha-1, was investigated in two controlled trials with potted plants and in an operational trial with mature P. radiata. In all trials, lesions formed on needles after artificial exposure to the infecting propagules (zoospores) of P. pluvialis were used to determine treatment efficacy, with the number and/or length of lesions as the dependent variable. Results across all trials indicated that cuprous oxide was highly effective at reducing infection of P. radiata with P. pluvialis. Application rates equivalent to ≥0.65 kg ha-1 significantly reduced infection levels relative to a control treatment, with foliar surface copper levels as low as 13 to 26 mg kg-1 of needle tissue preventing infection. Greater copper content was associated with a reduction in the proportion of needles with P. pluvialis lesions, with the probability of lesions developing decreasing approximately 1% for every 1 unit (in milligrams per kilogram) increase in copper content. Over a 90-day period, surface copper content declined to 30% of that originally applied, indicating an approximate period of treatment efficacy of 3 months. Our findings highlight the potential of cuprous oxide for the control of red needle cast in P. radiata stands. Further information about the optimal field dose, timing, and the frequency of foliar cuprous oxide application is key to prevent infection and also reduce the build up of inoculum during severe outbreaks of this pathogen.


Assuntos
Cobre , Phytophthora , Pinus , Doenças das Plantas , Antiparasitários/farmacologia , Cobre/análise , Cobre/farmacologia , Nova Zelândia , Phytophthora/efeitos dos fármacos , Phytophthora/fisiologia , Pinus/parasitologia , Doenças das Plantas/parasitologia , Doenças das Plantas/prevenção & controle
20.
Plant Dis ; 103(8): 1858-1864, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31242132

RESUMO

Although there has been research on managing Fusarium head blight (FHB) in spring barley, little has been published on cultivar resistance and optimal fungicide timing for FHB management in winter barley. A 3-year (2015 to 2017) field experiment was conducted to measure FHB resistance of winter barley varieties, gauge the potential benefit from a fungicide, and help determine the optimal timing for fungicide application. The split-plot experiment took place in a misted, inoculated nursery in Raleigh, North Carolina using main plots of four winter barley cultivars (Atlantic, Endeavor, Nomini, and Thoroughbred). Three fungicide treatments were applied to subplots: prothioconazole + tebuconazole at full spike emergence, the same fungicide 6 days later, or no fungicide. The late applications significantly reduced FHB index in each of 3 years and significantly reduced deoxynivalenol (DON) in harvested grain in 2 of the 3 years. Applications at full spike emergence also yielded significant benefit in 1 of the 3 years for each parameter. Neither disease symptoms nor DON gave reason to prefer one of the fungicide timings over the other. Across the 3 years, DON ranked the cultivars Endeavor < Nomini = Thoroughbred < Atlantic. Combining the moderate resistance of Endeavor with a fungicide application and averaging the two timings resulted in a 75% DON reduction compared with unsprayed Atlantic. Taken together, our results indicate that barley growers concerned about minimizing DON should both plant moderately resistant varieties and apply fungicide if there is scab risk. During the same period, 16 commercial winter barley cultivars were tested in from three to seven Virginia and North Carolina environments each, and the DON results were compared after standardization across environments. The winter two-row malting barley cultivars Endeavor and Calypso displayed superior and robust DON resistance across environments.


Assuntos
Resistência à Doença , Fungicidas Industriais , Fusarium , Hordeum , Resistência à Doença/genética , Fungicidas Industriais/farmacologia , Fusarium/efeitos dos fármacos , Fusarium/fisiologia , Hordeum/classificação , Hordeum/genética , Hordeum/microbiologia , North Carolina , Doenças das Plantas/microbiologia , Doenças das Plantas/prevenção & controle , Virginia
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