scholarly journals Induced Resistance as a Possible Means to Control Diseases of Strawberry Caused by Phytophthora spp.

Plant Disease ◽  
2003 ◽  
Vol 87 (4) ◽  
pp. 345-350 ◽  
Author(s):  
H. Eikemo ◽  
A. Stensvand ◽  
A. M. Tronsmo
Keyword(s):  
Growth Rate ◽  
Disease Resistance ◽  
Crown Rot ◽  
Fragaria Vesca ◽  
Disease Score ◽  
Phytophthora Cactorum ◽  
Phytophthora Spp ◽  
Retarding Effect ◽  
Severity Of The Disease

Two putative elicitors of disease resistance (acibenzolar-S-methyl and chitosan) were tested for their effect on crown rot (Phytophthora cactorum) in strawberry. The effect of both compounds was enhanced when the time between treatment and inoculation was prolonged from 2 to 20 days. There were no significant differences between treatments when the concentration of acibenzolar-S-methyl was increased from 10 to 1,000 μg a.i./plant. The lowest tested concentrations of chitosan (10 and 50 μg a.i./plant) resulted in a lower disease score compared with the highest concentrations (250 or 1,000 μg a.i./plant). There were no differences in disease score between treatment with fosetyl-Al, acibenzolar-S-methyl, or chitosan when applied 5 or 15 days before inoculation. The effect of acibenzolar-S-methyl and chitosan also was tested against P. fragariae var. fragariae in alpine strawberry (Fragaria vesca var. alpina cv. Alexandria). Chitosan had no effect, whereas fosetyl-Al and all treatments with acibenzolar-S-methyl (50 or 250 μg a.i./plant; 5, 10, 20, or 40 days before inoculation) reduced the severity of the disease. There were no significant differences between acibenzolar-S-methyl and fosetyl-Al when applied at the same time. Acibenzolar-S-methyl and chitosan at concentrations of 0.5, 5, 50, and 500 μg a.i. ml-1 in V8 juice agar were tested for possible effects on P. cactorum and P. fragariae var. fragariae in vitro. Only chitosan at concentrations of 50 and 500 μg a.i. ml-1 had a growth-retarding effect on P. cactorum. Both acibenzolar-S-methyl and chitosan at a concentration of 500 μg a.i. ml-1 reduced the growth rate of P. fragariae var. fragariae.

Phytophthora crown rot of Florida Strawberry: Inoculum Sources and Thermotherapy of Transplants for Disease Management

Plant Disease ◽  
2021 ◽  
Author(s):  
Juliana Silveira Baggio ◽  
Marcus Vinicius Marin ◽  
Natalia A. Peres
Keyword(s):  
Heat Treatment ◽  
Chemical Control ◽  
Pathogen Resistance ◽  
Crown Rot ◽  
Phytophthora Cactorum ◽  
Inoculum Sources ◽  
Phytophthora Spp ◽  
Commercial Farms ◽  
Important Disease

Phytophthora crown rot, caused mainly by Phytophthora cactorum, and also by the recently reported P. nicotianae, is an important disease in the Florida strawberry annual production system. Mefenoxam is the most effective and widely used fungicide to manage this disease. However, due to pathogen resistance, alternatives to chemical control are needed. Phytophthora spp. were rarely recovered during the summer from soil of commercial farms where the disease was observed during the season. In a more detailed survey on research plots, neither of the two species was recovered one month after the crop was terminated and water was shut off. Therefore, Phytophthora spp. does not seem to survive in the soil over summer in Florida. In a field trial, asymptomatic nursery transplants harboring quiescent infections were confirmed as the major source of inoculum for these pathogens in Florida. Heat treatment of P. cactorum zoospores at 44oC for as little as 5 min was effective in inhibiting germination and colony formation; however, oospore germination was not inhibited by any of the tested temperatures in vitro. In the field, thermotherapy treatment of inoculated plants was shown to have great potential to serve as a non-chemical approach for managing Phytophthora crown rot in production fields and reducing mefenoxam-resistant populations in nursery transplants.

Detection and Characterization of QoI-Resistant Phytophthora cactorum and P. nicotianae Causing Leather Rot in Florida Strawberry

Plant Disease ◽  
2021 ◽  
Author(s):  
Marcus Vinicius Marin ◽  
Teresa E Seijo ◽  
Ellias Zuchelli ◽  
Natalia A. Peres
Keyword(s):  
Point Mutations ◽  
Crown Rot ◽  
Cytb Gene ◽  
Phytophthora Cactorum ◽  
Phytophthora Spp ◽  
Mitochondrial Cytochrome B ◽  
Qualitative Resistance ◽  
Selection Of ◽  
Qoi Resistance

Phytophthora cactorum and P. nicotianae cause leather rot (LR) of fruit and Phytophthora crown rot (PhCR) in strawberry. LR occurs sporadically but can cause up to 70% fruit loss when weather is conducive. In Florida's annual strawberry winter production system, PhCR can be severe, resulting in plant stunting, mortality, and severe yield loss. Currently, azoxystrobin is labeled for control of LR but not for PhCR. The aims of this research were i) to determine the sensitivity of P. cactorum and P. nicotianae isolates from strawberry to azoxystrobin and ii) to investigate mechanisms of QoI-resistance present in P. cactorum and P. nicotianae based on the known point mutations within the cytb gene. Isolates of both Phytophthora spp. causing LR and PhCR were collected from multiple strawberry fields in Florida between 1997 and 2020. Isolates were tested for sensitivity to azoxystrobin at 0, 0.01, 0.1, 1.0, 10, and 50 µg/ml on potato dextrose agar (PDA) amended with SHAM (100 µg/ml). Isolates were separated into two groups, sensitive isolates, with the 50% effective concentration (EC50) values lower than 1.0 µg/ml, and resistant isolates having EC50 values higher than 50 µg/ml. P. cactorum and P. nicotianae resistance to azoxystrobin was found for isolates collected after 2010. The first 450 nucleotides of the mitochondrial cytochrome b (cytb) gene were sequenced from a selection of resistant and sensitive isolates of both species. The G143A mutation reported to confer resistance to azoxystrobin was found in all resistant P. cactorum isolates. However, in P. nicotianae, qualitative resistance was observed, but the isolates lacked all the known mutations in the cytb gene. This is the first report of resistance to azoxystrobin in P. cactorum and P. nicotianae.

Improving the toolbox to manage Phytophthora diseases of strawberry: searching for chemical alternatives

2021 ◽  
Author(s):  
Marcus Vinicius Marin ◽  
Natalia Peres
Keyword(s):  
Fungicide Resistance ◽  
Chemical Control ◽  
Mycelial Growth ◽  
Crown Rot ◽  
Resistance Risk ◽  
In Vivo Assays ◽  
Modes Of Action ◽  
Phytophthora Spp

Florida strawberry production is affected by two economically important Phytophthora diseases, Phytophthora crown rot (PhCR) and leather rot (LR), caused primarily by P. cactorum and P. nicotianae. Although products are available, chemical control is limited to mefenoxam, phosphites, and azoxystrobin and resistance to mefenoxam and azoxystrobin has been reported. Both in vitro and in vivo assays were conducted to evaluate the effectiveness of eight different chemical classes on controlling PhCR and LR of strawberry. The fungicides mandipropamid, fluopicolide, oxathiapiprolin, and cymoxanil completely inhibited mycelial growth of both species at 1µg/ml. The same fungicides controlled LR and PhCR caused by P. cactorum, in detached fruit and greenhouse trials, respectively, including mefenoxam-resistant isolates. However, for PhCR caused by P. nicotianae only oxathiapiprolin and cymoxanil were effective in controlling the disease. Cyazofamid, fluazinam, propamocarb, and tebuconazole did not control PhCR caused by either Phytophthora spp. Except for tebuconazole, all fungicides tested reduced incidence of LR caused by P. cactorum in the detached fruit assay; in contrast, fluazinam, cyazofamid, and propamocarb had no effect on P. nicotianae. This study identifies four fungicides that could potentially be registered to manage both PhCR and LR of strawberry. The registration of additional fungicides with different modes of action would allow fruit and nursery growers to alternate products to reduce fungicide resistance risk.

scholarly journals “Shining a LAMP” (Loop-Mediated Isothermal Amplification) on the Molecular Detection of Phytopathogens Phytophthora spp. and Phytophthora cactorum in Strawberry Fields

Pathogens ◽  
2021 ◽  
Vol 10 (11) ◽  
pp. 1453
Author(s):  
Dominika G. Siegieda ◽  
Jacek Panek ◽  
Magdalena Frąc
Keyword(s):  
Molecular Detection ◽  
Detection Method ◽  
Molecular Techniques ◽  
Isothermal Amplification ◽  
Crown Rot ◽  
Phytophthora Cactorum ◽  
Loop Mediated Isothermal Amplification ◽  
Phytophthora Spp ◽  
Freeze Dried ◽  
Starting Point

Phytopathogenic microorganisms belonging to the genus Phytophthora have been recognized many times as causal agents of diseases that lower the yield of many plants important for agriculture. Meanwhile, Phytophthora cactorum causes crown rot and leather rot of berry fruits, mainly strawberries. However, widely-applied culture-based methods used for the detection of pathogens are time-consuming and often inaccurate. What is more, molecular techniques require costly equipment. Here we show a rapid and effective detection method for the aforementioned targets, deploying a simple molecular biology technique, Loop-Mediated Isothermal Amplification (LAMP). We optimized assays to amplify the translation elongation factor 1-α (EF1a) gene for two targets: Phytophthora spp. And Phytophthora cactorum. We optimized the LAMP on pure strains of the pathogens, isolated from organic plantations of strawberry, and successfully validated the assay on biological material from the environment including soil samples, rhizosphere, shoots and roots of strawberry, and with SYBR Green. Our results demonstrate that a simple and reliable molecular detection method, that requires only a thermoblock and simple DNA isolation kit, can be successfully applied to detect pathogens that are difficult to separate from the field. We anticipate our findings to be a starting point for developing easier and faster modifications of the isothermal detection methods and which can be applied directly in the plantation, in particular with the use of freeze-dried reagents and chemistry, allowing observation of the results with the naked eye.

scholarly journals In Vitro Pathogenesis Caused by Phytophthora cactorum and DNA Analysis of the Strawberry-Resistant Microplants with ISSR Markers

Agronomy ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1279
Author(s):  
Wojciech Marecki ◽  
Jadwiga Żebrowska
Keyword(s):  
Genetic Similarity ◽  
In Vitro Selection ◽  
Dna Analysis ◽  
Pathogenic Fungus ◽  
Inter Simple Sequence Repeat ◽  
Issr Markers ◽  
Crown Rot ◽  
Phytophthora Cactorum ◽  
Selection Of

The soil pathogenic fungus Phytophthora cactorum causes the most dangerous diseases occurring in strawberry plantations—strawberry crown rot and leather rot. Modern biotechnology methods, e.g., in vitro culture selection and molecular diagnostics can be utilized in the selection of cultivars that are less susceptible or resistant to Phytophthora diseases. In this study, in vitro selection of four strawberry microclones: ‘Elsanta’, ‘Feltar’, ‘Teresa’ and ‘Plena SVdT’ against Phytophthora cactorum (Lebert and Cohn) J. Schröt was carried out. Molecular analysis with inter simple sequence repeat (ISSR) markers was also used to evaluate genetic similarity of the selected resistant plants. None of the analyzed microclones showed complete resistance to the selection factor, but there were plants in all tested microclones that survived the pressure of the pathogen. Results showed that susceptibility to this pathogenic fungus was significantly differentiated and depended on the microclone. The ‘Feltar’ microclone had the significantly lowest susceptibility to Phytophthora disease, followed by the microclones ‘Elsanta’ and ‘Teresa’ with significantly higher susceptibility. The ‘Plena SVdT’ microclone showed the highest susceptibility to Phytophthora disease. This differentiation was linked to the genetic similarity observed at deoxyribonucleic acid (DNA) level between the resistant plants selected from microclones. Cluster analysis revealed that microclones with similar susceptibility to phytophthorosis, i.e., ‘Elsanta’, ‘Feltar’ and ‘Teresa’, appeared to be genetically similar. The microclone ‘Plena SVdT’ revealed a different course of phytophthorosis from the aforementioned microclones, being the least genetically similar to them.

Antagonism of isolates of Bacillus subtilis to Phytophthora cactorum

1984 ◽  
Vol 62 (5) ◽  
pp. 1032-1035 ◽  
Author(s):  
R. S. Utkhede
Keyword(s):  
Bacillus Subtilis ◽  
Inhibition Zone ◽  
Crown Rot ◽  
Root Weight ◽  
Phytophthora Cactorum ◽  
Sclerotium Cepivorum ◽  
Greenhouse Trial ◽  
Bacterium Bacillus Subtilis ◽  
Bacterium Bacillus

Twenty-one isolates of the bacterium Bacillus subtilis isolated from local and exotic sclerotia of Sclerotium cepivorum were tested on cornmeal agar (CMA) for antagonism to six isolates of Phytophthora cactorum, causal agent of apple crown rot. All bacterial isolates produced diffusible antibiotics antagonistic to growth of all P. cactorum isolates on CMA. Antagonists were further evaluated in a replicated greenhouse trial for their ability to control crown rot infection on McIntosh apple seedlings in sterile soil. Six isolates of B. subtilis provided statistically significant reductions of infection on McIntosh seedlings. No correlation was observed between width of inhibition zone in vitro and protection from P. cactorum infections in McIntosh apple seedlings in a greenhouse trial. Significant negative correlations were observed between percent seedling infection and root weight.

Effect of pH and inhibitors on beta-amyloid fibril assembly

1996 ◽  
Vol 54 ◽  
pp. 752-753
Author(s):  
Beverly E. Maleeff ◽  
Timothy K. Hart ◽  
Stephen J. Wood ◽  
Ronald Wetzel
Keyword(s):  
Amyloid Fibril ◽  
Peptide Fragment ◽  
Hydrophobic Peptides ◽  
Amyloid Fibril Formation ◽  
Effects Of Ph ◽  
Severity Of The Disease ◽  
Kinetics Of ◽  
The Brain

Alzheimer's disease is characterized post-mortem in part by abnormal extracellular neuritic plaques found in brain tissue. There appears to be a correlation between the severity of Alzheimer's dementia in vivo and the number of plaques found in particular areas of the brain. These plaques are known to be the deposition sites of fibrils of the protein β-amyloid. It is thought that if the assembly of these plaques could be inhibited, the severity of the disease would be decreased. The peptide fragment Aβ, a precursor of the p-amyloid protein, has a 40 amino acid sequence, and has been shown to be toxic to neuronal cells in culture after an aging process of several days. This toxicity corresponds to the kinetics of in vitro amyloid fibril formation. In this study, we report the biochemical and ultrastructural effects of pH and the inhibitory agent hexadecyl-N-methylpiperidinium (HMP) bromide, one of a class of ionic micellar detergents known to be capable of solubilizing hydrophobic peptides, on the in vitro assembly of the peptide fragment Aβ.

scholarly journals Biological control of strawberry crown rot, root rot and grey mould by the beneficial fungus Aureobasidium pullulans

BioControl ◽  
2021 ◽  
Author(s):  
Mudassir Iqbal ◽  
Maha Jamshaid ◽  
Muhammad Awais Zahid ◽  
Erik Andreasson ◽  
Ramesh R. Vetukuri ◽  
...  
Keyword(s):  
Root Rot ◽  
Fungal Pathogens ◽  
Aureobasidium Pullulans ◽  
Grey Mould ◽  
Lesion Size ◽  
Plant Diseases ◽  
Crown Rot ◽  
Whole Plants

AbstractUtilization of biocontrol agents is a sustainable approach to reduce plant diseases caused by fungal pathogens. In the present study, we tested the effect of the candidate biocontrol fungus Aureobasidium pullulans (De Bary) G. Armaud on strawberry under in vitro and in vivo conditions to control crown rot, root rot and grey mould caused by Phytophthora cactorum (Lebert and Cohn) and Botrytis cinerea Pers, respectively. A dual plate confrontation assay showed that mycelial growth of P. cactorum and B. cinerea was reduced by 33–48% when challenged by A. pullulans as compared with control treatments. Likewise, detached leaf and fruit assays showed that A. pullulans significantly reduced necrotic lesion size on leaves and disease severity on fruits caused by P. cactorum and B. cinerea. In addition, greenhouse experiments with whole plants revealed enhanced biocontrol efficacy against root rot and grey mould when treated with A. pullulans either in combination with the pathogen or pre-treated with A. pullulans followed by inoculation of the pathogens. Our results demonstrate that A. pullulans is an effective biocontrol agent to control strawberry diseases caused by fungal pathogens and can be an effective alternative to chemical-based fungicides.

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