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1.
Pestic Biochem Physiol ; 165: 104523, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32359551

RESUMO

Tobacco black shank (TBS) caused by Phytophthora nicotianae is destructive to almost all tobacco cultivars and is widespread in many tobacco-growing countries. Through lab study and field test, we isolated plant growth-promoting rhizobacteria (PGPR) strain Ba168 which is a promising biocontrol strain of TBS. Ba168 was isolated from 168 soil samples and identified as Bacillus velezensis by its genetic and phenotypic characteristics. A susceptibility test indicated that the P. nicotianae antagonistic materials of Ba168 in extracellular metabolites were composed of effective and stable proteins/peptides. P. nicotianae's growth was suppressed by the ammonium sulfate precipitation of Ba168 culture filtrates (ASPBa) at a minimum inhibitory concentration of 5 µg/mL. Extracellular conductivity, pH, and the wet/dry weights of P. nicotianae's mycelia, along with scanning electron microscope analysis, suggested that Ba168-derived proteins/peptides could effectively inhibit P. nicotianae by causing irreversible damage to its cell walls and membranes. Protein identification of ASPBa supported these results and identified many key proteins responsible for various biocontrol-related pathways. Field assays of TBS control efficacy of many PGPRs and agrochemicals showed that all PGPR preparations reduced the disease index of tobacco, but Ba168 was the most effective. These results demonstrated the importance of Bacillus-derived proteins/peptides in the inhibition of P. nicotianae through irreversible damage to its cell wall and membrane; and the effectiveness of PGPR strain B. velezensis Ba168 for biocontrol of the soil-borne disease caused by P. nicotianae.


Assuntos
Bacillus , Phytophthora , Doenças das Plantas , Tabaco
2.
Arch Virol ; 165(7): 1679-1682, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32367229

RESUMO

This report describes the complete genome sequence of a double-stranded RNA (dsRNA) virus infecting the oomycetous plant pathogen Phytophthora cactorum. The virus genome consists of a single dsRNA segment of 5699 bp with two open reading frames predicted to overlap with each other and encoding a putative capsid protein of 705 aa and an RNA-dependent RNA polymerase of 779 aa. Sequence comparisons indicated that this virus, designated as "Phytophthora cactorum RNA virus 1" (PcRV1), shares the highest sequence similarity with the unclassified Pythium splendens RNA virus 1 (58% RdRp aa sequence identity). Phylogenetic analysis revealed that these two oomycete viruses group together with Giardia lamblia virus (GVL; family Totiviridae) and several unclassified toti-like viruses from arthropods, fish and fungi. This is the first report of a toti-like virus in a member of the genus Phytophthora and the first virus characterized in P. cactorum.


Assuntos
Genoma Viral , Phytophthora/virologia , Totiviridae/genética , Sequência de Bases , Fases de Leitura Aberta , Filogenia , Doenças das Plantas/microbiologia , RNA de Cadeia Dupla/genética , RNA Viral/genética , Totiviridae/classificação , Totiviridae/isolamento & purificação
3.
Plant Dis ; 104(6): 1841-1850, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32370604

RESUMO

Rhododendron root rot is a severe disease that causes significant mortality in rhododendrons. Information is needed about the incidence and identity of soilborne Phytophthora and Pythium species causing root rot in Pacific Northwest nurseries in order to better understand the disease etiology and to optimize disease control strategies. The last survey focusing solely on soilborne oomycete pathogens in rhododendron production was conducted in 1974. Since then, advances in pathogen identification have occurred, new species may have been introduced, pathogen communities may have shifted, and little is known about Pythium species affecting this crop. Therefore, a survey of root-infecting Phytophthora and Pythium species was conducted at seven nurseries from 2013 to 2017 to (i) document the incidence of root rot damage at each nursery and stage of production, (ii) identify soilborne oomycetes infecting rhododendron, and (iii) determine whether there are differences in pathogen diversity among nurseries and production systems. Rhododendrons from propagation, container, and field systems were sampled and Phytophthora and Pythium species were isolated from the roots and collar region. Root rot was rarely evident in propagation systems, which were dominated by Pythium species. However, severe root rot was much more common in container and field systems where the genus Phytophthora was also more prevalent, suggesting that Phytophthora species are the primary cause of severe root rot and that most contamination by these pathogens comes in after the propagation stage. In total, 20 Pythium species and 11 Phytophthora species were identified. Pythium cryptoirregulare, Pythium aff. macrosporum, Phytophthora plurivora, and Phytophthora cinnamomi were the most frequently isolated species and the results showed that Phytophthora plurivora has become much more common than in the past. Phytophthora diversity was also greater in field systems than in propagation or container systems. Risks for Phytophthora contamination were commonly observed during the survey and included placement of potting media in direct contact with field soil, the presence of dead plants that could serve as continuous sources of inoculum, and the presence of excess water as a result of poor drainage, overirrigation, or malfunctioning irrigation equipment. In the past, research on disease development and root rot disease control in rhododendron focused almost exclusively on Phytophthora cinnamomi. More research is needed on both of these topics for the other root-infecting species identified in this survey.


Assuntos
Phytophthora , Pythium , Rhododendron , Noroeste dos Estados Unidos , Doenças das Plantas
4.
Plant Dis ; 104(6): 1638-1646, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32310718

RESUMO

Phytophthora nicotianae is an oomycete that causes black shank, one of the most economically important diseases affecting tobacco production worldwide. Identification and introgression of novel genetic variability affecting partial genetic resistance to this pathogen is important because of the increased durability of partial resistance over time as compared with genes conferring immunity. A previous mapping study identified a quantitative trait locus (QTL), hereafter designated as Phn15.1, with a major effect on P. nicotianae resistance in tobacco. In this research, we describe significantly improved resistance of nearly isogenic lines (NILs) of flue-cured tobacco carrying the introgressed Phn15.1 region derived from highly resistant cigar tobacco cultivar Beinhart 1000. The Phn15.1 region appeared to act in an additive or partially dominant manner to positively affect resistance. To more finely resolve the position of the gene or genes underlying the Phn15.1 effect, the QTL was mapped with an increased number of molecular markers (single-nucleotide polymorphisms) identified to reside within the region. Development and evaluation of subNILs containing varying amounts of Beinhart 1000-derived Phn15.1-associated genetic material permitted the localization of the QTL to a genetic interval of approximately 2.7 centimorgans. Importantly, we were able to disassociate the Beinhart 1000 Phn15.1 resistance alleles from a functional NtCPS2 allele(s) which contributes to the accumulation of a diterpene leaf surface exudate considered undesirable for flue-cured and burley tobacco. Information from this research should be of value for marker-assisted introgression of Beinhart 1000-derived partial black shank resistance into flue-cured and burley tobacco breeding programs.


Assuntos
Phytophthora , Alelos , Doenças das Plantas , Locos de Características Quantitativas , Tabaco
5.
PLoS One ; 15(3): e0227710, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32196522

RESUMO

Phytophthora sojae is one of the costliest soybean pathogens in the US. Quantitative disease resistance (QDR) is a vital part of Phytophthora disease management. In this study, QDR was measured in 478 and 495 plant introductions (PIs) towards P. sojae isolates OH.121 and C2.S1, respectively, in genome-wide association (GWA) analyses to identify genetic markers linked to QDR loci (QDRL). Populations were generated by sampling PIs from the US, the Republic of Korea, and the full collection of PIs maintained by the USDA. Additionally, a meta-analysis of QDRL reported from bi-parental studies was done to compare past and present findings. Twenty-four significant marker-trait associations were identified from the 478 PIs phenotyped with OH.121, and an additional 24 marker-trait associations were identified from the 495 PIs phenotyped with C2.S1. In total, 48 significant markers were distributed across 16 chromosomes and based on linkage analysis, represent a total of 44 QDRL. The majority of QDRL were identified with only one of the two isolates, and only a region on chromosome 13 was consistently identified. Regions on chromosomes 3, 13, and 17 were identified in previous GWA-analyses and were re-identified in this study. Five QDRL co-localized with P. sojae meta-QDRL identified from QDRL reported in previous biparental mapping studies. The remaining regions represent novel QDRL, in the soybean-P. sojae pathosystem and were primarily identified in germplasm from the Republic of Korea. Overall, the number of loci identified in this study highlights the complexity of QDR to P. sojae.


Assuntos
Produtos Agrícolas/genética , Resistência à Doença/genética , Espécies Introduzidas , Phytophthora/patogenicidade , Soja/genética , Mapeamento Cromossômico , Cromossomos de Plantas/genética , Produtos Agrícolas/microbiologia , Conjuntos de Dados como Assunto , Genoma de Planta/genética , Estudo de Associação Genômica Ampla , Melhoramento Vegetal , Polimorfismo de Nucleotídeo Único , Locos de Características Quantitativas , República da Coreia , Sementes/genética , Soja/microbiologia , Estados Unidos
6.
Plant Dis ; 104(5): 1421-1432, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32191161

RESUMO

Phytophthora, Phytopythium, and Pythium species that cause early-season seed decay and pre-emergence and post-emergence damping off of soybean are most commonly managed with seed treatments. The phenylamide fungicides metalaxyl and mefenoxam, and ethaboxam are effective toward some but not all species. The primary objective of this study was to evaluate the efficacy of ethaboxam in fungicide mixtures and compare those with other fungicides as seed treatments to protect soybean against Pythium, Phytopythium, and Phytophthora species in both high-disease field environments and laboratory seed plate assays. The second objective was to evaluate these seed treatment mixtures on cultivars that have varying levels and combinations of resistance to these soilborne pathogens. Five of eight environments received adequate precipitation in the 14 days after planting for high levels of seedling disease development and treatment evaluations. Three environments had significantly greater stands, and three had significantly greater yield when ethaboxam was used in the seed treatment mixture compared with treatments containing metalaxyl or mefenoxam alone. Three fungicide formulations significantly reduced disease severity compared with nontreated in the seed plate assay for 17 species. However, the combination of ethaboxam plus metalaxyl in a mixture was more effective than either fungicide alone against some Pythium and Phytopythium species. Overall, our results indicate that the addition of ethaboxam to a fungicide seed treatment is effective in reducing seed rot caused by these pathogens commonly isolated from soybean in Ohio but that these effects can be masked when cultivars with resistance are planted.


Assuntos
Phytophthora , Pythium , Ohio , Doenças das Plantas , Sementes , Soja , Tiazóis , Tiofenos
7.
PLoS One ; 15(3): e0230531, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32191748

RESUMO

Among several studied strains, Streptomyces rochei IT20 and S. vinaceusdrappus SS14 showed a high level of inhibitory effect against Phytophthora capsici, the causal agent of pepper blight. The effect of two mentioned superior antagonists, as single or combination treatments, on suppression of stem and fruit blight diseases and reproductive growth promotion was investigated in pepper. To explore the induced plant defense reactions, ROS generation and transcriptional changes of selected genes in leaf and fruit tissues of the plant were evaluated. The plants exposed to the combination of two species responded differently in terms of H2O2 accumulation and expression ratio of GST gene compared to single treatments upon pathogen inoculation. Besides, the increment of shoot length, flowering, and fruit weight were observed in healthy plants compared to control. Likely, these changes depended on the coordinated relationships between PR1, ACCO genes and transcription factors WRKY40 enhanced after pathogen challenge. Our findings indicate that appropriate tissue of the host plant is required for inducing Streptomyces-based priming and relied on the up-regulation of SUS and differential regulation of ethylene-dependent genes.


Assuntos
Capsicum/microbiologia , Especificidade de Órgãos , Phytophthora/fisiologia , Streptomyces/fisiologia , Aminobutiratos/farmacologia , Capsicum/genética , Capsicum/crescimento & desenvolvimento , Frutas/genética , Regulação da Expressão Gênica de Plantas , Genes de Plantas , Peróxido de Hidrogênio/metabolismo , Especificidade de Órgãos/genética , Doenças das Plantas/genética , Doenças das Plantas/microbiologia , Folhas de Planta/genética
8.
Plant Dis ; 104(5): 1500-1506, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32105574

RESUMO

Widespread symptoms of root rot and mortality on Juniperus communis and Microbiota decussata were observed in two horticultural nurseries in Oregon, leading to the isolation of a Phytophthora sp. from diseased roots. Based on morphology and sequencing the internal transcribed spacer ITS1-5.8S-ITS2 region, isolates were identified as the invasive pathogen Phytophthora lateralis, causal agent of Port-Orford-cedar (POC; Chamaecyparis lawsoniana) root disease. Additional sequencing of the cytochrome c oxidase subunit 1 and 2 genes identified all isolates as belonging to the PNW lineage. Utilizing recovered isolates plus a POC-wildlands isolate and susceptible POC as controls, we completed Koch's postulates on potted Juniperus and Microbiota plants. Nursery isolates were more aggressive than the forest isolate, which was used in the POC resistance breeding program. Increased aggressiveness was confirmed using a branch stem dip assay with four POC clones that differed in resistance, although no isolate completely overcame major-gene resistance. Isolates were sensitive to mefenoxam, a fungicide commonly used to suppress Phytophthora spp. growth in commercial nurseries. Although POC resistance is durable against these more aggressive nursery isolates, the expanded host range of P. lateralis challenges POC conservation through the continued movement of P. lateralis by the nursery industry.


Assuntos
Juniperus , Microbiota , Berçários para Lactentes , Phytophthora , Humanos , Lactente , Oregon , Doenças das Plantas
9.
PLoS One ; 15(2): e0221742, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32023247

RESUMO

Wood and wood products can harbor microorganisms that can raise phytosanitary concerns in countries importing or exporting these products. To evaluate the efficacy of wood treatment on the survival of microorganisms of phytosanitary concern the method of choice is to grow microbes in petri dishes for subsequent identification. However, some plant pathogens are difficult or impossible to grow in axenic cultures. A molecular methodology capable of detecting living fungi and fungus-like organisms in situ can provide a solution. RNA represents the transcription of genes and can become rapidly unstable after cell death, providing a proxy measure of viability. We designed and used RNA-based molecular diagnostic assays targeting genes essential to vital processes and assessed their presence in wood colonized by fungi and oomycetes through reverse transcription and real-time polymerase chain reaction (PCR). A stability analysis was conducted by comparing the ratio of mRNA to gDNA over time following heat treatment of mycelial cultures of the Oomycete Phytophthora ramorum and the fungus Grosmannia clavigera. The real-time PCR results indicated that the DNA remained stable over a period of 10 days post treatment in heat-treated samples, whereas mRNA could not be detected after 24 hours for P. ramorum or 96 hours for G. clavigera. Therefore, this method provides a reliable way to evaluate the viability of these pathogens and offers a potential way to assess the effectiveness of existing and emerging wood treatments. This can have important phytosanitary impacts on assessing both timber and non-timber forest products of commercial value in international wood trade.


Assuntos
Ophiostomatales/isolamento & purificação , Phytophthora/isolamento & purificação , Madeira/microbiologia , Sobrevivência Celular , DNA Fúngico/análise , Ophiostomatales/citologia , Ophiostomatales/genética , Phytophthora/citologia , Phytophthora/genética , Doenças das Plantas/microbiologia , Reação em Cadeia da Polimerase , RNA Fúngico/análise
10.
PLoS One ; 15(2): e0227284, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32050262

RESUMO

Phytophthora blight caused by Phytophthora capsici is a devastating disease for melon plant. However, the underlying resistance mechanisms are still poorly understood. In this study, the transcriptome differences between the resistant ZQK9 and susceptible E31 at 0, 3, and 5 days post-inoculation (dpi) were identified by RNA-seq. A total of 1,195 and 6,595 differentially expressed genes (DEGs) were identified in ZQK9 and E31, respectively. P. capsici infection triggered massive transcript changes in the inoculated tissues. Genes related to plant defense responses were activated, which was reflected by a lot of up-regulated DEGs involved in pathogenesis-related (PR) genes, hormones biosynthesis and signal transduction, secondary metabolites biosynthesis and cell wall modification in resistant ZQK9. The dataset generated in this study may provide a basis for identifying candidate resistant genes in melon against P. capsici and lay a foundation for further research on the molecular mechanisms.


Assuntos
Cucurbitaceae/genética , Resistência à Doença/genética , Regulação da Expressão Gênica de Plantas/genética , Doenças das Plantas/genética , Proteínas de Plantas/genética , Transcriptoma/genética , Perfilação da Expressão Gênica/métodos , Phytophthora/crescimento & desenvolvimento
11.
Plant Dis ; 104(4): 1113-1117, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32040390

RESUMO

Host-pathogen interactions of a new species of Phytophthora, causal agent of late blight of tree tomato (Solanum betaceum Cav.), identified as Phytophthora betacei, were investigated with four different cultivars. Thirty-six P. betacei isolates, collected from southern Colombia between 2008 and 2009, were used to inoculate common tree tomato cultivars, Común, Híbrido, Injerto, and Holandés. Data on incubation and latent periods as well as infection efficiency, lesion development, and total sporulation were collected via detached leaf assays. Significant differences in susceptibility, based on the parameters measured, were observed. Común was the most susceptible cultivar, followed by Injerto, Híbrido, and Holandés. The mean incubation period was lowest for Común at 125.6 h post-inoculation (hpi) and highest for Híbrido at 139.4 hpi. No significant differences in latent period were observed. All 36 isolates produced necrotic lesions on Común, and 33, 24, and 21 caused infection on Injerto, Híbrido, and Holandés, respectively. Two isolates were able to cause infection only on Común, and 13 isolates were able to infect all four cultivars. Infection efficiency was significantly higher for the cultivar Común, followed by Injerto, Híbrido, and Holandés. Average lesion size was larger on Común than on any other cultivar. An inverse relationship of lesion size and total sporulation was observed. Común had significantly lower total sporulation than Híbrido and Holandés, which had the smallest average lesion sizes. These data show variation in pathogenicity of P. betacei isolates, under controlled conditions, and differential susceptibility of four distinct S. betaceum cultivars.


Assuntos
Lycopersicon esculentum , Phytophthora , Solanum , Colômbia , Doenças das Plantas , Árvores
12.
PLoS Pathog ; 16(1): e1008138, 2020 01.
Artigo em Inglês | MEDLINE | ID: mdl-31961913

RESUMO

Eukaryotic heterotrimeric guanine nucleotide-binding proteins consist of α, ß, and γ subunits, which act as molecular switches to regulate a number of fundamental cellular processes. In the oomycete pathogen Phytophthora sojae, the sole G protein α subunit (Gα; encoded by PsGPA1) has been found to be involved in zoospore mobility and virulence, but how it functions remains unclear. In this study, we show that the Gα subunit PsGPA1 directly interacts with PsYPK1, a serine/threonine protein kinase that consists of an N-terminal region with unknown function and a C-terminal region with a conserved catalytic kinase domain. We generated knockout and knockout-complemented strains of PsYPK1 and found that deletion of PsYPK1 resulted in a pronounced reduction in the production of sporangia and oospores, in mycelial growth on nutrient poor medium, and in virulence. PsYPK1 exhibits a cytoplasmic-nuclear localization pattern that is essential for sporangium formation and virulence of P. sojae. Interestingly, PsGPA1 overexpression was found to prevent nuclear localization of PsYPK1 by exclusively binding to the N-terminal region of PsYPK1, therefore accounting for its negative role in sporangium formation. Our data demonstrate that PsGPA1 negatively regulates sporangium formation by repressing the nuclear localization of its downstream kinase PsYPK1.


Assuntos
Subunidades alfa de Proteínas de Ligação ao GTP/metabolismo , Phytophthora/enzimologia , Proteínas Serina-Treonina Quinases/metabolismo , Esporos/crescimento & desenvolvimento , Núcleo Celular/genética , Núcleo Celular/metabolismo , Subunidades alfa de Proteínas de Ligação ao GTP/química , Subunidades alfa de Proteínas de Ligação ao GTP/genética , Phytophthora/genética , Phytophthora/crescimento & desenvolvimento , Phytophthora/patogenicidade , Doenças das Plantas/parasitologia , Ligação Proteica , Domínios Proteicos , Transporte Proteico , Proteínas Serina-Treonina Quinases/química , Proteínas Serina-Treonina Quinases/genética , Soja/parasitologia , Esporos/enzimologia , Esporos/genética , Esporos/metabolismo , Virulência
13.
PLoS One ; 15(1): e0227250, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31910244

RESUMO

Oomycete plant pathogens are difficult to control and routine genetic research is challenging. A major problem is instability of isolates. Here we characterize >600 field and single zoospore isolates of Phytophthora capsici for inheritance of mating type, sensitivity to mefenoxam, chromosome copy number and heterozygous allele frequencies. The A2 mating type was highly unstable with 26% of 241 A2 isolates remaining A2. The A1 mating type was stable. Isolates intermediately resistant to mefenoxam produced fully resistant single-spore progeny. Sensitive isolates remained fully sensitive. Genome re-sequencing of single zoospore isolates revealed extreme aneuploidy; a phenomenon dubbed Dynamic Extreme Aneuploidy (DEA). DEA is characterized by the asexual inheritance of diverse intra-genomic combinations of chromosomal ploidy ranging from 2N to 3N and heterozygous allele frequencies that do not strictly correspond to ploidy. Isolates sectoring on agar media showed dramatically altered heterozygous allele frequencies. DEA can explain the rapid increase of advantageous alleles (e.g. drug resistance), mating type switches and copy neutral loss of heterozygosity (LOH). Although the mechanisms driving DEA are unknown, it can play an important role in adaptation and evolution and seriously hinders all aspects of P. capsici research.


Assuntos
Aneuploidia , Phytophthora/fisiologia , Doenças das Plantas/microbiologia , Reprodução Assexuada/genética , Verduras/microbiologia , Alelos , Evolução Biológica , Mapeamento Cromossômico , Cucumis sativus/microbiologia , Variação Genética , Genótipo , Perda de Heterozigosidade , Phytophthora/isolamento & purificação , Polimorfismo de Nucleotídeo Único , Análise de Sequência de DNA , Análise de Célula Única , Esporos/genética
14.
PLoS One ; 15(1): e0224007, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31978166

RESUMO

The root rot causing oomycete, Phytophthora agathidicida, threatens the long-term survival of the iconic New Zealand kauri. Currently, testing for this pathogen involves an extended soil bioassay that takes 14-20 days and requires specialised staff, consumables, and infrastructure. Here we describe a loop-mediated isothermal amplification (LAMP) assay for the detection of P. agathidicida that targets a portion of the mitochondrial apocytochrome b coding sequence. This assay has high specificity and sensitivity; it did not cross react with a range of other Phytophthora isolates and detected as little as 1 fg of total P. agathidicida DNA or 116 copies of the target locus. Assay performance was further investigated by testing plant tissue baits from flooded soil samples using both the extended soil bioassay and LAMP testing of DNA extracted from baits. In these comparisons, P. agathidicida was detected more frequently using the LAMP test. In addition to greater sensitivity, by removing the need for culturing, the hybrid baiting plus LAMP approach is more cost effective than the extended soil bioassay and, importantly, does not require a centralised laboratory facility with specialised staff, consumables, and equipment. Such testing will allow us to address outstanding questions about P. agathidicida. For example, the hybrid approach could enable monitoring of the pathogen beyond areas with visible disease symptoms, allow direct evaluation of rates and patterns of spread, and allow the effectiveness of disease control to be evaluated. The hybrid LAMP bioassay also has the potential to empower local communities to evaluate the pathogen status of local kauri stands, providing information for disease management and conservation initiatives.


Assuntos
Araucariaceae/microbiologia , Phytophthora/genética , Doenças das Plantas/microbiologia , Microbiologia do Solo , Araucariaceae/genética , Bioensaio , DNA de Plantas/genética , Nova Zelândia , Phytophthora/isolamento & purificação , Phytophthora/patogenicidade , Doenças das Plantas/genética
15.
Plant Dis ; 104(3): 921-929, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31910117

RESUMO

Clonal rootstocks are one alternative used by the walnut industry to control damage caused by Phytophthora species, traditionally using plants grafted on susceptible Juglans regia rootstock. Vlach, VX211, and RX1 are clonal rootstocks with a degree of resistance to Phytophthora species. The resistance to pathogens in these rootstocks depends on the resistance mechanisms activated by the presence of the pathogen and subsequent development of responses in the host. In this work, we analyzed how plants of J. regia, Vlach, VX211, and RX1 responded to inoculation with Phytophthora cinnamomi or Phytophthora citrophthora isolates obtained from diseased English walnut plants from Chilean orchards. After inoculation, plants of Vlach, VX211, and RX1 showed canopy and root damage indexes that did not differ from noninoculated control plants. In contrast, plants of J. regia, which is susceptible to P. cinnamomi and P. citrophthora, died after inoculation. Vlach, VX211, and RX1 plants inoculated with P. cinnamomi or P. citrophthora showed greater root weight and volume and greater root growth rates than their respective controls. These results suggest that short-term carbohydrate dynamics may be related to the defense mechanisms of plants; they are immediately activated after inoculation through the production of phenolic compounds, which support the further growth and development of roots in walnut clonal rootstocks. To our knowledge, this is the first study that comprehensively characterizes vegetative and radicular growth and the dynamics of sugars and phenols in response to infection with P. cinnamomi or P. citrophthora in walnut rootstocks.


Assuntos
Infecções , Juglans , Phytophthora , Chile , Humanos , Doenças das Plantas , Raízes de Plantas
16.
J Asian Nat Prod Res ; 22(6): 578-587, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-31046458

RESUMO

Sixteen sulfonate derivatives of maltol were synthesized and screened in vitro for their anti-oomycete and nematicidal activity against Phytophthora capsici and Bursaphelenchus xylophilus, respectively. Among all the compounds, 3e, 3m, and 3p exhibited the most promising and pronounced anti-oomycete activity against P. capsici than zoxamide, and the EC50 values of 25.42, 18.44, 23.69, and 27.99 mg/L, respectively; compounds 3e, 3m, 3n, and 3p exhibited potent nematicidal activity with LC50 values ranging from 1 to 2 mg/L, especially 3m and 3n showed the best promising and pronounced nematicidal activity, with LC50 values of 1.1762 and 1.2384 mg/L, respectively. [Formula: see text].


Assuntos
Phytophthora , Antinematódeos , Estrutura Molecular , Pironas
17.
Plant Dis ; 104(2): 315-319, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31809254

RESUMO

Phytophthora nicotianae is a widespread cause of black shank disease of tobacco plants and causes substantial harvest losses in all major cultivation areas. The oomycete primarily affects plant roots and the stem, where it leads to a progressing decay of the diseased tissues. In this resource announcement, we provide two complementary datasets comprising 16S gene fragment amplicons (bacteriome) and ITS1 region amplicons (mycobiome) that were sequenced on an Illumina-based platform. Soil samples were obtained from disease-affected fields in Guizhou province (China) and include control samples from adhering fields without previous disease incidence. Both datasets were acquired at a high sequencing depth and accompanied by detailed metadata, which facilitate their implementation in comparative studies. The resource announcement provides a basis for disease-specific biomarker detection and correlation studies that include the microbiome.


Assuntos
Micobioma , Phytophthora , China , Doenças das Plantas , Tabaco
18.
Nucleic Acids Res ; 48(4): 1790-1799, 2020 02 28.
Artigo em Inglês | MEDLINE | ID: mdl-31819959

RESUMO

The relentless adaptability of pathogen populations is a major obstacle to effective disease control measures. Increasing evidence suggests that gene transcriptional polymorphisms are a strategy deployed by pathogens to evade host immunity. However, the underlying mechanisms of transcriptional plasticity remain largely elusive. Here we found that the soybean root rot pathogen Phytophthora sojae evades the soybean Resistance gene Rps1b through transcriptional polymorphisms in the effector gene Avr1b that occur in the absence of any sequence variation. Elevated levels of histone H3 Lysine27 tri-methylation (H3K27me3) were observed at the Avr1b locus in a naturally occurring Avr1b-silenced strain but not in an Avr1b-expressing strain, suggesting a correlation between this epigenetic modification and silencing of Avr1b. To genetically test this hypothesis, we edited the gene, PsSu(z)12, encoding a core subunit of the H3K27me3 methyltransferase complex by using CRISPR/Cas9, and obtained three deletion mutants. H3K27me3 depletion within the Avr1b genomic region correlated with impaired Avr1b gene silencing in these mutants. Importantly, these mutants lost the ability to evade immune recognition by soybeans carrying Rps1b. These data support a model in which pathogen effector transcriptional polymorphisms are associated with changes in chromatin epigenetic marks, highlighting epigenetic variation as a mechanism of pathogen adaptive plasticity.


Assuntos
Histonas/genética , Phytophthora/genética , Doenças das Plantas/microbiologia , Soja/genética , Alelos , Sequência de Aminoácidos/genética , Inativação Gênica , Metilação , Phytophthora/patogenicidade , Doenças das Plantas/genética , Homologia de Sequência de Aminoácidos , Soja/microbiologia , Virulência/genética
19.
Phytopathology ; 110(2): 447-455, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31454304

RESUMO

Phytophthora capsici is a destructive pathogen of cucurbits that causes root, crown, and fruit rot. Winter squash (Cucurbita spp.) production is limited by this pathogen in Michigan and other U.S. growing regions. Age-related resistance (ARR) to P. capsici occurs in C. moschata fruit but is negated by wounding. This study aimed to determine whether structural barriers to infection exist in the intact exocarp of maturing fruit exhibiting ARR. Five C. moschata cultivars were evaluated for resistance to P. capsici 10, 14, 16, 18, and 21 days postpollination (dpp). Scanning electron microscopy imaging of Chieftain butternut fruit exocarp of susceptible fruit at 7 dpp and resistant fruit at 14 and 21 dpp revealed significant increases in cuticle and epidermal thicknesses as fruit aged. P. capsici hyphae penetrated susceptible fruit at 7 dpp directly from the surface or through wounds before 6 h postinoculation (hpi) and completely degraded the fruit cell wall within 48 hpi. Resistant fruit remained unaffected at 14 and 21 dpp. The high correlation between the formation of a thickened cuticle and epidermis in maturing winter squash fruit and resistance to P. capsici indicates the presence of a structural barrier to P. capsici as the fruit matures.


Assuntos
Cucurbita , Resistência à Doença , Frutas , Phytophthora , Cucurbita/parasitologia , Resistência à Doença/fisiologia , Frutas/citologia , Frutas/parasitologia , Phytophthora/fisiologia , Doenças das Plantas/parasitologia
20.
Plant Dis ; 104(2): 408-413, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31790644

RESUMO

Phytophthora root and stem rot (PRR) caused by Phytophthora sojae is a destructive disease afflicting soybean. The use of resistant cultivars is the most effective method to combat PRR. PRR resistance was assessed in 223 soybean cultivars from Huanghuaihai and Dongbei, major soybean-producing regions in east central and northeastern China. To evaluate levels of soybean resistance to P. sojae, we used eight representative P. sojae isolates and a modified etiolated hypocotyl-slit inoculation method. The cultivars Wandou21020, Xu9302-A, Kedou10, and Lidi055 showed resistance to all eight isolates; 14 cultivars showed intermediate resistance to all eight P. sojae isolates, and 53 cultivars were resistant to seven isolates. Thirty-three cultivars (15%) were susceptible only to the highly virulent PsJS2 isolate, which is consistent with the reactions of the Chapman differential line that carries Rps3a. The diverse reaction patterns seen in germplasm from different regions (provinces/cities) in this study reflect the variety of PRR-resistant soybean sources in China. Our research indicates that sources of P. sojae resistance are present in the major soybean production areas of China. This study provides useful information for soybean breeding programs.


Assuntos
Phytophthora , China , Resistência à Doença , Humanos , Doenças das Plantas , Proteínas Ribossômicas , Soja
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