scholarly journals Purification and Biological Characterization of Host-Specific SV-Toxins from Stemphylium vesicarium Causing Brown Spot of European Pear

1999 ◽  
Vol 89 (10) ◽  
pp. 947-953 ◽  
Author(s):  
P. Singh ◽  
R. Bugiani ◽  
P. Cavanni ◽  
H. Nakajima ◽  
M. Kodama ◽  
...  
Keyword(s):  
Brown Spot ◽  
Early Effect ◽  
Stemphylium Vesicarium ◽  
European Pear ◽  
Veinal Necrosis ◽  
Resistant Cultivars ◽  
Culture Filtrates ◽  
Leaf Tissues ◽  
Electrolyte Loss ◽  
Host Specific Toxins

Culture filtrates of a pathogenic isolate (IT37) of Stemphylium vesicarium, causing brown spot of European pear, induced veinal necrosis only on pear leaves susceptible to the pathogen. Two host-specific toxins, SV-toxins I and II, were purified from culture filtrates of IT37 by successively using Amberlite XAD-2 resin adsorption, cellulose thin-layer chromatography, and high-performance liquid chromatography under three different sets of conditions. Susceptible cultivars showed veinal necrosis at a SV-toxin I concentration of 0.01 to 0.1 μg/ml, whereas resistant cultivars were insensitive to the toxin at 1,000 μg/ml. SV-toxins I and II caused a dose-dependent increase in electrolyte loss from susceptible leaf tissues. No increase in electrolyte loss was detected in leaf tissues from resistant cultivars. The results of physiological studies indicated that SV-toxins appear to have an early effect on plasma membranes of susceptible leaves. Spores of a nonpathogenic isolate induced necrotic lesions on susceptible leaves in the presence of a small amount of toxin. SV-toxins were detected in intercellular fluids obtained from diseased leaves after inoculation with the pathogen. The results indicate that SV-toxins I and II produced by S. vesicarium can be characterized as host-specific toxins.

Alternaria toxins and their effects on host plants

1995 ◽  
Vol 73 (S1) ◽  
pp. 453-458 ◽  
Author(s):  
Hiroshi Otani ◽  
Keisuke Kohmoto ◽  
Motoichiro Kodama
Keyword(s):  
Plasma Membrane ◽  
Host Plants ◽  
Plasma Membranes ◽  
Early Effect ◽  
The Third ◽  
The Matrix ◽  
Electrolyte Loss ◽  
Host Specific Toxins ◽  
Acid Structure ◽  
Malate Oxidation

There are now nine or more Alternaria pathogens that produce host-specific toxins, and the structures of most of the toxins have been elucidated. Alternaria host-specific toxins are classified in three groups in terms of the primary site action. ACT-, AF-, and AK-toxins have in common an epoxy-decatrienoic acid structure and exert their primary effect on the plasma membrane of susceptible cells. A rapid increase in electrolyte loss from tissues and invaginations in the plasma membranes are common effects of these toxins. The second group is represented by ACR(L)-toxin, which induces changes in mitochondria, including swelling, vesiculation of cristae, decrease in the electron density of the matrix, increase in the rate of NADH oxidation, and inhibition of malate oxidation. The third group consists of AM-toxin, which appears to exert an early effect on both chloroplasts and plasma membranes. AM-toxin induces vesiculation of grana lamellae, inhibition of CO2 fixation, invagination of plasma membranes, and electrolyte loss. The roles of host-specific toxins in pathogenesis are discussed. Key words: Alternaria, host-specific toxin, plasma membrane, mitochondrion, chloroplast.

scholarly journals Infection Potential of Pleospora allii and Evaluation of Methods for Reduction of the Overwintering Inoculum of Brown Spot of Pear

Plant Disease ◽  
2006 ◽  
Vol 90 (12) ◽  
pp. 1511-1516 ◽  
Author(s):  
Isidre Llorente ◽  
Albert Vilardell ◽  
Emilio Montesinos
Keyword(s):  
Biological Control ◽  
Brown Spot ◽  
Control Methods ◽  
Optimum Temperature ◽  
Chemical Methods ◽  
Stemphylium Vesicarium ◽  
Mechanical Methods ◽  
Pleospora Allii ◽  
Evaluation Of Methods

The capacity for germination and pathogenicity to pear leaves of ascospores of Pleospora allii, the teleomorph of Stemphylium vesicarium, causal agent of brown spot of pear, were studied in vitro. Most ascospores germinated within 1 h at temperatures between 15 and 20°C, and the optimum temperature for germination was 18.9°C. Infections developed on wounded and non-wounded detached pear leaves, but were more frequent on wounded leaves. The minimum infective dose was one ascospore per wound. Biological, chemical, and mechanical methods for decreasing overwintering inoculum of P. allii were evaluated. Ascospores were discharged from March to May, depending on the orchard and year. Leaf shredding or removal were the most effective methods of reducing overwintering inoculum. Biological control methods based on application of Thichodermasp. formulations were partially effective. Chemical methods based on copper and urea treatments were ineffective.

STREP: a brown-spot disease predictor for scheduling fungicide sprays against Stemphylium vesicarium on pear

EPPO Bulletin ◽  
2000 ◽  
Vol 30 (1) ◽  
pp. 143-148 ◽  
Author(s):  
I. Llorente ◽  
C. Moragrega ◽  
P. Vilardell ◽  
E. Montesinos
Keyword(s):  
Brown Spot ◽  
Stemphylium Vesicarium ◽  
Spot Disease ◽  
Brown Spot Disease

HOST-SPECIFIC SV-TOXIN OF THE FUNGAL PATHOGEN CAUSING BROWN SPOT OF EUROPEAN PEAR

2002 ◽  
pp. 507-511
Author(s):  
P. Singh ◽  
H. Nakajima ◽  
H. Otani ◽  
M. Kodama ◽  
K. Kohmoto ◽  
...  
Keyword(s):  
Fungal Pathogen ◽  
Brown Spot ◽  
European Pear

scholarly journals Effect of Relative Humidity and Interrupted Wetness Periods on Brown Spot Severity of Pear Caused by Stemphylium vesicarium

2002 ◽  
Vol 92 (1) ◽  
pp. 99-104 ◽  
Author(s):  
I. Llorente ◽  
E. Montesinos
Keyword(s):  
Relative Humidity ◽  
Water Film ◽  
Infection Process ◽  
Variable Length ◽  
Brown Spot ◽  
Field Observations ◽  
Plant Surface ◽  
Dry Period ◽  
Stemphylium Vesicarium ◽  
Surface Wetness

Field observations in four pear orchards during 5 years from April to October indicated that days with uninterrupted wetness of variable length represented 83.9% of the total days studied. However, days with surface wetness interruptions and with high relative humidity (RH) (≥90%) without wetness occurred with a frequency of 7.1 and 6.2%, respectively. Accordingly, the effect of interruption of 24-h wetness periods by dry periods of high or low RH on infections caused by Stemphylium vesicarium on pear was determined. Pear plants inoculated with conidia of S. vesicarium were exposed to a 12-h wet period followed by a dry period of variable length (0, 3, 6, 12, 18, or 24 h) and a second wet period of 12 h. The dry period consisted either of low (60%) or high (96%) RH. The infection process was irreversibly stopped under low RH during dry periods between wetness, but continued at high RH. The effect of high RH on disease severity in the absence of wetness was also determined. Pear plants inoculated with S. vesicarium were exposed to periods of variable length (3 to 24 h) either at high RH (96%) in the presence of wetness or at high RH (96%) without wetness. No infections were observed on plants incubated under high RH without wetness, indicating that conidia of S. vesicarium require the presence of a water film in the plant surface to develop infections on pear.

Interaction of antifungal peptide BP15 with Stemphylium vesicarium , the causal agent of brown spot of pear

2016 ◽  
Vol 120 (1) ◽  
pp. 61-71 ◽  
Author(s):  
Mireia Puig ◽  
Concepció Moragrega ◽  
Lídia Ruz ◽  
Claudia E. Calderón ◽  
Francisco M. Cazorla ◽  
...  
Keyword(s):  
Causal Agent ◽  
Brown Spot ◽  
Antifungal Peptide ◽  
Stemphylium Vesicarium

QTLS FOR BROWN SPOT RESISTANCE IN EUROPEAN PEAR

2015 ◽  
pp. 167-171
Author(s):  
P. De Franceschi ◽  
A. Ciriani ◽  
M. Collina ◽  
A. Brunelli ◽  
L. Dondini
Keyword(s):  
Brown Spot ◽  
European Pear

scholarly journals Potential Application of Propolis Extracts to Control the Growth of Stemphylium vesicarium in “Rocha” Pear

2020 ◽  
Vol 10 (6) ◽  
pp. 1990 ◽  
Author(s):  
Marcella Loebler ◽  
Claudia Sánchez ◽  
Elisabete Muchagato Maurício ◽  
Eugénio Diogo ◽  
Mário Santos ◽  
...  
Keyword(s):  
Disease Incidence ◽  
Brown Spot ◽  
In Vitro Assays ◽  
Economic Losses ◽  
Yield Reduction ◽  
Stemphylium Vesicarium ◽  
Spot Disease ◽  
Brown Spot Disease

Stemphylium vesicarium (Wallr.) E. G. Simmons is the pathogen responsible of brown spot disease in pear and has become one of the main concerns for European pear producers. In Portugal, S. vesicarium is responsible for significant yield reduction and economic losses in “Rocha” pear (Pyrus communis L. cv Rocha) production. Considering the antimicrobial potential of propolis, the high incidence of brown spot in pears and the emergence of fungicides resistance in S. vesicarium, this study aimed to evaluate the potential of Portuguese propolis as an alternative strategy to control brown spot disease in “Rocha” pear. In vitro assays showed that propolis extracts were able to inhibit up to 90% the S. vesicarium mycelial growth. In vivo assays in artificially wounded and inoculated “Rocha” pears showed that, compared to the control, the disease incidence decreased up to 25% and the lesions diameter up to 57%, in fruits treated with propolis. Moreover, propolis seems to be more efficient in reducing the disease incidence when applied after pathogen inoculation (curative assay) than when applied before pathogen inoculation (prophylactic assay). Thus, the results suggest that propolis extracts have potential to be applied as part of an integrated approach for the control of brown spot of pear.

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