Sensitivity to fungicides in the isolates of Phytophthora infestans (Mont.) de Bary in the Czech Republic from 2003 to 2008

In the growing seasons from 2003 to 2008, 547 isolates of Phytophthora infestans from five regions in the Czech Republic were collected and examined for their sensitivity to the active ingredients (metalaxyl, dimethomorph and propamocarb-HCl) of frequently used fungicides. The response of the isolates to each of these substances was examined using the in vitro amended-agar method; in 352 of these isolates, the sensitivity to metalaxyl was also assessed by the floating leaf-disc assay. The majority of the isolates were sensitive (89.8%) to metalaxyl. Resistant isolates were found only in two of the sample years (2003 and 2008); they represented 58% of the samples in 2003 and only 29% in 2008. Four isolates from 2004 were found to be intermediate for their level of resistance. All the isolates that were tested were sensitive to dimethomorph and propamocarb-HCl; these particular substances completely suppressed mycelial growth at 1 µg a.i. per ml.

Download Full-text

Evaluation of powdery mildew resistance in various melon (Cucumis melo L.) genotypes

Agricultural Science and Technology ◽

10.15547/10.15547/ast.2018.04.053 ◽

2018 ◽

Vol 10 (4) ◽

pp. 279-284

Author(s):

Zh. Ivanova ◽

K. Vasileva ◽

N. Velkov ◽

S. Grozeva

Keyword(s):

Powdery Mildew ◽

Genetic Resistance ◽

Leaf Disc ◽

Breeding Program ◽

Vegetable Crops ◽

Plant Materials ◽

South Central ◽

Leaf Disc Assay ◽

Disc Assay

Abstract. Powdery mildew, caused by Podosphaera xanthii and Golovinomyces cichoracearum, is an economically important disease in melon worldwide. Genetic resistance is one of the most suitable strategies to control powdery mildew. During the last few years several races of the pathogens have been reported. The need to develop resistant varieties is a challenge for each breeding program. Leaf disc assay was used in phytopathology and breeding programs as a rapid and reliable method for evaluation of disease resistance in a large number of plant materials. The purpose of this study was to establish species and races of powdery mildew in Plovdiv region, South Central Bulgaria; to develop a suitable system of pathogen isolation and cultivation; to determine the resistance levels in different melon genotypes available in Maritsa Vegetable Crops Research Institute (MVCRI) - Plovdiv collection by the leaf disc assay. Fifty-three melon genotypes, including lines, varieties, hybrids and ten differential lines were tested. The data showed that causal agent of powdery mildew was race 1 of P. xanthii in Plovdiv region. Our experimental results indicated that for the long-term storage of powdery mildew it is preferable to keep a whole plant under in vitro conditions. This allows the preservation of powdery mildew for two months before transferring on a new tissue. Thirty-four of the tested melon genotypes reacted as immune or resistant and nineteen as susceptible. Resistant melon genotypes are a suitable source in initiating a new breeding program aimed to increase resistance to powdery mildew.

Download Full-text

Influence of selected fungicides registered in the Czech Republic for winter oilseed rape on in vitro Sclerotinia sclerotiorum mycelial growth

Plant Protection Science ◽

10.17221/137/2016-pps ◽

2018 ◽

Vol 54 (No. 2) ◽

pp. 101-110 ◽

Cited By ~ 1

Author(s):

Poslušná Jana ◽

Plachká Eva ◽

Mazáková Jana

Keyword(s):

Czech Republic ◽

Oilseed Rape ◽

Sclerotinia Sclerotiorum ◽

Mycelial Growth ◽

Winter Oilseed Rape ◽

Baseline Sensitivity ◽

The Czech Republic ◽

Dose Rates ◽

The Mean

The baseline sensitivity of 55 isolates of Sclerotinia sclerotiorum, collected from oilseed rape in 6 regions of the Czech Republic, to selected fungicides was determined during the period 2013–2015. One single-component fungicide – Horizon (tebuconazole), and four multicomponent fungicides – Pictor (boscalid, dimoxystrobin), Efilor (boscalid, metconazole), Prosaro 250 EC (prothioconazole, tebuconazole), and Propulse (fluopyram, prothioconazole), were chosen as these are commonly used locally. The effect of each fungicide on the in vitro pathogen radial mycelial growth and EC50 values for the respective fungicides were determined. The following MIC values were estimated; for the fungicides Horizon 250 EW, Efilor, and Propulse the mean MIC values ranged between 0.125 and 0.250 µl/ml, for Prosaro 250 EC ranged between 0.0625 and 0.125 µl/ml, and for Pictor ranged from 0.00781 to 0.01562 µl/ml. No strains of S. sclerotiorum resistant to the tested fungicides were detected and the growth of all isolates was fully inhibited at concentrations corresponding to their registered dose rates. The highest fungicidal efficacy on the collected S. sclerotiorum isolates was recorded for Pictor, followed by Prosaro 250 with an EC50 value 0.05856 µl/ml and then the remaining fungicides Propulse, Efilor, and Horizon 250 EW (EC50 values 0.07277, 0.07221, and 0.08519 µl/ml, respectively).

Download Full-text

Occurrence and distribution of mating types A1 and A2 of Phytophthora infestans (Mont.) de Bary in the Czech Republic

Plant Protection Science ◽

10.17221/2697-pps ◽

2010 ◽

Vol 42 (No. 2) ◽

pp. 41-48 ◽

Cited By ~ 7

Author(s):

J. Mazáková ◽

V. Táborský ◽

M. Zouhar ◽

P. Ryšánek ◽

E. Hausvater ◽

...

Keyword(s):

Czech Republic ◽

Phytophthora Infestans ◽

Mating Type ◽

Mating Types ◽

Pcr Markers ◽

The Czech Republic ◽

First Report

A total of 199 Phytophthora infestans isolates were obtained from leaves, tubers and fruits of infected crops of potato and tomato in different regions of the Czech Republic in 2003, 2004 and 2005. They were analysed for mating type using the conventional pairing assay and PCR markers; 107 isolates were of A1 and 92 of A2 mating type. No self-fertile isolate was found. Our study is the first report of the presence and distribution of the A2 mating type of P. infestans in the Czech Republic. The co-existence of the two mating types may enable the pathogen to reproduce sexually, thus enhancing the diversity of its population countrywide.

Download Full-text

Biocontrol Activity of Three Pseudomonas in a Newly Assembled Collection of Phytophthora infestans Isolates

Phytopathology ◽

10.1094/phyto-12-18-0487-r ◽

2019 ◽

Vol 109 (9) ◽

pp. 1555-1565 ◽

Cited By ~ 4

Author(s):

Mout De Vrieze ◽

Ramona Gloor ◽

Josep Massana Codina ◽

Stefano Torriani ◽

Katia Gindro ◽

...

Keyword(s):

Phytophthora Infestans ◽

Leaf Disc ◽

Potato Production ◽

Biocontrol Activity ◽

General Demand ◽

Resistant Genotypes ◽

Highly Virulent ◽

Alternative Control Methods ◽

Open Access Article

Late blight caused by the oomycete Phytophthora infestans constitutes the greatest threat to potato production worldwide. Considering the increasing concerns regarding the emergence of novel fungicide-resistant genotypes and the general demand for reducing inputs of synthetic and copper-based fungicides, the need for alternative control methods is acute. Several bacterial antagonists have shown anti-Phytophthora effects during in vitro and greenhouse experiments. We report the effects of three Pseudomonas strains recovered from field-grown potatoes against a collection of P. infestans isolates assembled for this study. The collection comprised 19 P. infestans isolates of mating types A1 and A2 greatly varying in fungicide resistance and virulence profiles as deduced from leaf disc experiments on Black’s differential set. The mycelial growth of all P. infestans isolates was fully inhibited when co-cultivated with the most active Pseudomonas strain (R47). Moreover, the isolates reacted differently to exposure to the less active Pseudomonas strains (S19 and R76). Leaf disc infection experiments with six selected P. infestans isolates showed that four of them, including highly virulent and fungicide-resistant ones, could be efficiently controlled by different potato-associated Pseudomonas strains. [Formula: see text] Copyright © 2019 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Download Full-text

Shikimate Accumulation in Sunflower, Wheat, and Proso Millet after Glyphosate Application

Weed Science ◽

10.1614/ws-06-065.1 ◽

2007 ◽

Vol 55 (1) ◽

pp. 1-5 ◽

Cited By ~ 30

Author(s):

W. Brien Henry ◽

Dale L. Shaner ◽

Mark S. West

Keyword(s):

Leaf Disc ◽

Spectrophotometric Assay ◽

The Other ◽

Proso Millet ◽

Glyphosate Drift ◽

Leaf Disc Assay ◽

Disc Assay

Experiments were conducted to examine the utility of a spectrophometric leaf disc assay for detecting shikimate accumulation after glyphosate application in sunflower, proso millet, and wheat. The assay was conducted on both greenhouse- and field-grown plants. Glyphosate was applied at five rates ranging from 840 to 53 g ae ha−1. Shikimate accumulation data were generated at 1, 4, 7, and 14 d after application (DAA). Sunflower accumulated shikimate more rapidly and at lower glyphosate rates than the other two species. At 14 DAA, glyphosate at the two highest rates remained detectable in all three species. Plants receiving lower glyphosate doses (210, 105, and 53 g ae ha−1) had begun to grow out of the injury, or at least the shikimate levels in the plants were no longer significantly different than that present in the untreated controls. This spectrophotometric assay is both rapid and simple, with respect to other means of detecting shikimate, and it can be used to detect glyphosate drift. For it to be used by crop managers, samples from potentially drift-affected crops should be taken as soon as possible after the suspected drift event or immediately after the appearance of glyphosate injury.

Download Full-text

Variations in the Sensitivity of Phytophthora infestans Isolates from Different Genetic Backgrounds to Dimethomorph

Plant Disease ◽

10.1094/pdis.2003.87.11.1283 ◽

2003 ◽

Vol 87 (11) ◽

pp. 1283-1289 ◽

Cited By ~ 24

Author(s):

J. M. Stein ◽

W. W. Kirk

Keyword(s):

Life Cycle ◽

Phytophthora Infestans ◽

Mycelial Growth ◽

Hyphal Growth ◽

Potato Leaf ◽

Leaf Discs ◽

Highly Sensitive ◽

Significant Difference ◽

Cyst Germination

The sensitivities of 11 isolates of Phytophthora infestans to dimethomorph were examined at all stages of the asexual life cycle and when inoculated onto potato leaf discs. In vitro zoospore encystment and cyst germination were highly sensitive to dimethomorph with 50% reduction of mycelial growth and cyst germination (EC50) values for most isolates <0.20 μg/ml, whereas direct sporangia germination and in vitro hyphal growth and sporulation were less sensitive (means of 0.45 and 0.22 μg/ml, respectively). Zoosporogenesis was not significantly inhibited at the maximum dimethomorph concentration examined, 10 μg/ml. Significant differences (Fisher's least significant difference, P = 0.05) in the EC50 values were present between isolates for all stages of the asexual life cycle, except direct sporangia germination and zoosporogenesis. Sensitivity ratios between the least- and most-sensitive isolates were 6.11, 12.14, 12.36, and 10.56 for hyphal growth, in vitro sporulation, zoospore encystment, and cyst germination, respectively. Application of dimethomorph at 1,000 μg/ml to potato leaf discs at 24 or 48 h before inoculation completely inhibited symptom incidence for most isolates, whereas application after inoculation generally was not significantly different from the untreated control, regardless of concentration. Sporulation from leaf discs treated with dimethomorph at 24 or 48 h after inoculation was completely inhibited for all isolates with dimethomorph at 1,000 μg/ml, even when symptom incidence was not significantly reduced.

Download Full-text

Resistance behaviour of Septoria tritici to some fungicides in the territory of the Czech Republic

Acta Agrobotanica ◽

10.5586/aa.2005.012 ◽

2012 ◽

Vol 58 (1) ◽

pp. 79-84 ◽

Cited By ~ 2

Author(s):

Ludvik Tvaružek ◽

P. Horáková ◽

L. Ji

Keyword(s):

Czech Republic ◽

Septoria Tritici ◽

Resistance Development ◽

The Czech Republic ◽

Colony Diameter ◽

Dmi Fungicides ◽

The Mean ◽

Different Parts ◽

Pathogen Strains

Reduction of colony diameter using two DMI-fungicides and one strobilurine fungicide was evaluated in the Septoria tritici population. In an in vitro assay, 57 strains of S. tritici originating from different parts of the Czech Republic were grown on agar plates containing different concentrations of fungicides. The mean EC50 values of strains were analysed for flusilazole (Capitain), metconazole (Caramba) and one strobilurine fungicide: azoxystrobin (Amistar). ED 50 values for metconazole were low. There were highly significant correlation in reaction of pathogen strains to metconazole and flusilazole. Some isolates showed significant higher level of resistance to azoxystrobin. The data will be used in a continuing survey of resistance development in the S. tritici population originating from the territory of the Czech Republic.

Download Full-text

In vitro antifungal activities of 26 plant extracts on mycelial growth of Phytophthora infestans (Mont.) de Bary

AFRICAN JOURNAL OF BIOTECHNOLOGY ◽

10.5897/ajb10.1219 ◽

2011 ◽

Vol 10 (14) ◽

pp. 2625-2629 ◽

Cited By ~ 8

Author(s):

Yanar Yusuf ◽

Kadioğlu Izzet ◽

Gouml kccedil e Ayhan ◽

Demirtaş İbrahim ◽

Gouml ren Nezhun ◽

...

Keyword(s):

Phytophthora Infestans ◽

Plant Extracts ◽

Mycelial Growth ◽

Antifungal Activities

Download Full-text

Mating type distribution of Phytophthora infestans (Mont.) de Bary in the Czech Republic in 2007 and 2008

Plant Protection Science ◽

10.17221/49/2009-pps ◽

2010 ◽

Vol 46 (No. 3) ◽

pp. 89-97 ◽

Cited By ~ 4

Author(s):

J. Mazáková ◽

M. Zouhar ◽

P. Ryšánek ◽

V. Táborský ◽

E. Hausvater ◽

...

Keyword(s):

Czech Republic ◽

Late Blight ◽

Phytophthora Infestans ◽

Mating Type ◽

Caps Marker ◽

The Czech Republic ◽

Type Distribution ◽

Pcr Assays

A total of 195 isolates of Phytophthora infestans were collected from late blight-diseased potatoes grown in several localities in the Czech Republic during the years 2007–2008. The isolates were analysed for mating type using the pairing test, CAPS marker assays and PCR assays. Of the 195 tested isolates, 28% were of the A1 mating type and 75% corresponded to the A2 mating type. Furthermore, oospores of P. infestans were microscopically detected in leaf samples from one locality.

Download Full-text

Contribution of Hydrogen Cyanide to the Antagonistic Activity of Pseudomonas Strains Against Phytophthora infestans

Microorganisms ◽

10.3390/microorganisms8081144 ◽

2020 ◽

Vol 8 (8) ◽

pp. 1144

Author(s):

Abhishek Anand ◽

Delphine Chinchilla ◽

Christopher Tan ◽

Laurent Mène-Saffrané ◽

Floriane L’Haridon ◽

...

Keyword(s):

Growth Inhibition ◽

Phytophthora Infestans ◽

Hydrogen Cyanide ◽

Mycelial Growth ◽

Developmental Stages ◽

Antagonistic Activity ◽

Potato Leaf ◽

Relative Contribution ◽

Production Of Hydrogen

Plants face many biotic and abiotic challenges in nature; one of them is attack by disease-causing microbes. Phytophthora infestans, the causal agent of late blight is one of the most prominent pathogens of the potato responsible for multi-billion-dollar losses every year. We have previously reported that potato-associated Pseudomonas strains inhibited P. infestans at various developmental stages. A comparative genomics approach identified several factors putatively involved in this anti-oomycete activity, among which was the production of hydrogen cyanide (HCN). Here, we report the relative contribution of HCN emission to the overall anti-Phytophthora activity of two cyanogenic Pseudomonas strains, P. putida R32 and P. chlororaphis R47. To quantify this contribution, we generated HCN-negative mutants (Δhcn) and compared their activities to those of their respective wild types in different experiments assessing P. infestans mycelial growth, zoospore germination, and infection of potato leaf disks. Using in vitro experiments allowing only volatile-mediated interactions, we observed that HCN accounted for most of the mycelial growth inhibition (57% in R47 and 80% in R32). However, when allowing both volatile and diffusible compound-mediated interactions, HCN only accounted for 1% (R47) and 18% (R32) of mycelial growth inhibition. Likewise, both mutants inhibited zoospore germination in a similar way as their respective wild types. More importantly, leaf disk experiments showed that both wild-type and Δhcn strains of R47 and R32 were able to limit P. infestans infection to a similar extent. Our results suggest that while HCN is a major contributor to the in vitro volatile-mediated restriction of P. infestans mycelial growth, it does not play a major role in the inhibition of other disease-related features such as zoospore germination or infection of plant tissues.

Download Full-text