scholarly journals Occurrence of sdh Mutations in German Alternaria solani Isolates and Potential Impact on Boscalid Sensitivity In Vitro, in the Greenhouse, and in the Field

Plant Disease ◽  
2019 ◽  
Vol 103 (12) ◽  
pp. 3065-3071 ◽  
Author(s):  
Nicole Metz ◽  
Birgit Adolf ◽  
Nicole Chaluppa ◽  
Ralph Hückelhoven ◽  
Hans Hausladen
Keyword(s):  
Succinate Dehydrogenase ◽  
Early Blight ◽  
Solanum Tuberosum L ◽  
Point Mutations ◽  
Alternaria Solani ◽  
Field Trials ◽  
Sensitivity Testing ◽  
Development Of Resistance

The fungus Alternaria solani is the main pathogen causing early blight on potatoes (Solanum tuberosum L.). An increase in the development of resistance to the succinate dehydrogenase inhibitor (SDHI) boscalid, one of the main active ingredients for the control of early blight, has been reported. For this study, monitoring data from Germany were collected between 2013 and 2016 and an increase in the occurrence of A. solani succinate dehydrogenase (SDH) mutant isolates was observed. In addition to the known point mutations in sdh complex II, a new mutation in subunit C was found in German isolates (SdhC-H134Q). SDHI fungicide sensitivity testing was performed in the laboratory, greenhouse, and field. Reduced boscalid sensitivity was shown for mutant isolates (SdhB-H278Y and SdhC-H134R) both in vitro and in vivo. In addition, field trials with artificial inoculation were performed in 2016 and 2017. In both years, fungicide efficacy was significantly reduced after mutant inoculation compared with wild-type inoculation.

scholarly journals Potential Impact of Fluopyram on the Frequency of the D123E Mutation in Alternaria solani

Plant Disease ◽  
2018 ◽  
Vol 102 (3) ◽  
pp. 656-665 ◽  
Author(s):  
Mitchell J. Bauske ◽  
S. K. R. Yellareddygari ◽  
Neil C. Gudmestad
Keyword(s):  
Disease Control ◽  
Solanum Tuberosum L ◽  
Management Strategies ◽  
Point Mutations ◽  
Fungal Growth ◽  
Alternaria Solani ◽  
Selective Advantage ◽  
Field Trials

Succinate dehydrogenase-inhibiting (SDHI) fungicides have been widely applied in commercial potato (Solanum tuberosum L.) fields for the control of early blight, caused by Alternaria solani Sorauer. Five-point mutations on three AsSdh genes in A. solani have been identified as conferring resistance to SDHI fungicides. Recent work in our laboratory determined that A. solani isolates possessing the D123E mutation, or the substitution of aspartic acid for glutamic acid at position 123 in the AsSdhD gene, were collected at successively higher frequencies throughout a 3-year survey. In total, 118 A. solani isolates previously characterized as possessing the D123E mutation were evaluated in vitro for boscalid and fluopyram sensitivity. Over 80% of A. solani isolates with the D123E mutation evaluated were determined to be highly resistant to boscalid in vitro. However, effective concentration at which the fungal growth is inhibited by 50% values of isolates with the D123E mutation to fluopyram, ranging from 0.2 to 3 µg/ml, were sensitive and only slightly higher than those of baseline isolates to fluopyram, which ranged from 0.1 to 0.6 µg/ml. Five A. solani isolates with the D123E mutation were further evaluated in vivo for percent disease control obtained from boscalid and fluopyram compared with two wild-type isolates, three isolates possessing the F129L mutation, two isolates possessing the H134R mutation, two isolates possessing the H133R mutation, and one isolate with the H278R mutation. Relative area under the dose response curve values for boscalid and fluopyram were significantly lower for all five D123E-mutant isolates, demonstrating reduced disease control in vivo. In field trials, the frequency of A. solani isolates with the D123E mutation recovered from treatments receiving an in-furrow application of fluopyram ranged from 5 to 37%, which was significantly higher compared with treatments receiving foliar applications of standard protectants, in which the frequency of the D123E mutation in isolates ranged from 0 to 2.5%. Results suggest that A. solani isolates possessing the D123E mutation have a selective advantage under the application of fluopyram compared with SDHI-sensitive isolates, as well as isolates possessing other mutations conferring SDHI resistance. These data illustrate the importance of implementing fungicide resistance management strategies and cautions the use of fluopyram for in-furrow applications that target other pathogens of potato.

scholarly journals Low-Level Resistance to Rifampin in Streptococcus pneumoniae

2003 ◽  
Vol 47 (3) ◽  
pp. 863-868 ◽  
Author(s):  
Patricia Stutzmann Meier ◽  
Silvia Utz ◽  
Suzanne Aebi ◽  
Kathrin Mühlemann
Keyword(s):  
Streptococcus Pneumoniae ◽  
Point Mutations ◽  
Low Level ◽  
Development Of Resistance ◽  
Rifampin Resistance ◽  
High Level ◽  
Tissue Compartments ◽  
Level Resistance

ABSTRACT Rifampin is recommended for combination therapy of meningitis due to β-lactam-resistant Streptococcus pneumoniae. High-level rifampin resistance (MIC, ≥4 mg/liter) has been mapped to point mutations in clusters I and III of rpoB of the pneumococcus. The molecular basis of low-level resistance (MICs, ≥0.5 and <4 mg/liter) was analyzed. Spontaneous mutants of clinical pneumococcal isolates were selected on Columbia sheep blood agar plates containing rifampin at 0.5, 4, 10, or 50 mg/liter. Low-level resistance could be assigned to mutations in cluster II (I545N, I545L). Sensitive (MIC, <0.048 mg/liter) wild-type strains acquired low-level resistance at a rate approximately 10 times higher than that at which they acquired high-level resistance (average mutation frequencies, 2.4 × 10−7 for low-level resistance versus 2.9 × 10−8 for high-level resistance [P < 0.0001]). In second-step experiments, the frequencies of mutations from low- to high-level resistance were over 10 times higher than the frequencies of mutations from susceptibility to high-level resistance (average mutation frequencies, 7.2 × 10−7 versus 5.0 × 10−8 [P < 0.001]). Mutants with low-level resistance were stable upon passage. Sequencing of a clinical isolate with low-level resistance (MIC, 0.5 mg/liter) revealed a Q150R mutation upstream of cluster I. The frequencies of mutations to high-level resistance for this strain were even higher than the rates observed for the in vitro mutants. Therefore, a resistance-mediating mutation located outside clusters I, II, and III has been described for the first time in the pneumococcus. In vitro low-level rifampin resistance in S. pneumoniae could be mapped to cluster II of rpoB. Mutants of pneumococcus with low-level resistance may be selected in vivo during therapy in tissue compartments with low antibiotic concentrations and play a role in the development of resistance.

scholarly journals Lanthanum in vitro control of Alternaria solani and induction resistance mechanism against blight tomato plant

2021 ◽  
Vol 16 (2) ◽  
pp. 153-158
Author(s):  
Antônio Jussiê da Silva Solino ◽  
Juliana Santos Batista Oliveira ◽  
Sergio Augusto Cesnik ◽  
Kátia Regina Freitas Schwan-Estrada
Keyword(s):  
Mycelial Growth ◽  
Culture Medium ◽  
Early Blight ◽  
Resistance Mechanism ◽  
Alternaria Solani ◽  
Plant Diseases ◽  
Guaiacol Peroxidase ◽  
Specific Catalytic Activity

Rare earth elements have been tested in control of plant diseases. Lanthanum (La) was tested in the control of Alternaria solani (in vitro) and tomato early blight (in vivo) using the concentration 0; 0.1; 0.2; 0.4 and 0.8 g L-1. In vitro, the concentration were diluted in V8 culture medium and evaluated for mycelial growth rate index (MGRI) and pathogen sporulation. In vivo, 24 hours after the application of concentration was inoculate the pathogen and 24 hours after the inoculation, leaflets were collected for quantification, the specific catalytic activity and guaiacol peroxidase. The severity of tomato early blight were also analyzed. As 0.27 and 0.28 g L-1 reduces 28% and 50% the MGRI and the sporulation, respectively. Peroxidase and catalase activity was increased by 298% and 151% in tomato treated with 0.5 and 0.4 g L-1de La, respectively. In vivo reduces AUDPC 70% when was applied 0.27 g L-1 La. Lanthanum can be used as resistance inducer in controlling tomato early blight.

scholarly journals Evaluating the Antifungal Activity of Some Traditional Medicinal Plant Extracts against Alternaria solani (Tomato Early Blight Pathogen) in Ethiopia

2022 ◽  
Author(s):  
Meseret Tadelo ◽  
Tamirat Wato ◽  
Tilahun Negash
Keyword(s):  
Medicinal Plants ◽  
Plant Extracts ◽  
Early Blight ◽  
Allium Sativum ◽  
Alternaria Solani ◽  
Significant Inhibition ◽  
Crude Extracts ◽  
Medicinal Plant Extracts

Background: Tomato (Lycopersicon esculentum Mill.) belongs to the family Solanaceae. In Ethiopia, control of early blight is largely dependent on fungicidal application. There is a research need to identify effective botanical extracts to control Alternaria solani that cause early blight of tomato and for evaluation of plant extracts through different solvents on the target pathogen. Methods: In vitro experiment was conducted to evaluate the effectiveness of crude extracts of 16 selected medicinal plants against Alternaria solani. Thus, crude extracts were extracted from medicinal plants with different solvents (methanol, ethanol and petroleum at (25%, 50% and 100%) concentrations. The Alternaria solani was isolated from infected tomato leaves showing early blight symptoms. Evaluation of plant extracts was carried out against Alternaria solani using food poisoned technique on PDA. Result: Results showed that most of the methanolic extract plants were showed significant inhibition of the mycelial growth as compared to ethanolic and petroleum ether extracts. A higher rate of mycelial reduction was recorded by ethanol extracts of Allium sativum at all concentrations (100%) followed by methanol extracts of Allium sativum at 25%, 50%, 100% concentration (90.02%, 97.01%, 100% respectively). The effectiveness of extracts against Alternaria solani depends on use at the higher concentrations and various solvents. For crude extracts that have shown higher inhibitory effects against Alternaria solani in vitro conditions, actual chemical compounds should be identified. Furthermore, it is also important to evaluate these plants on other microbes, study to test in vivo and to assess their real potential field condition wherever early blight is an important disease of tomato.

scholarly journals Parasitic Fitness of Fungicide-Resistant and -Sensitive Isolates of Alternaria solani

Plant Disease ◽  
2018 ◽  
Vol 102 (3) ◽  
pp. 666-673 ◽  
Author(s):  
Mitchell J. Bauske ◽  
Neil C. Gudmestad
Keyword(s):  
Spore Germination ◽  
Point Mutations ◽  
Alternaria Solani ◽  
The United States ◽  
Wild Type ◽  
Parasitic Fitness ◽  
Fitness Parameters ◽  
Multiple Chemical

Resistance to chemistries of the succinate dehydrogenase inhibiting (SDHI) and quinone outside inhibiting (QoI) fungicides has developed rapidly in populations of Alternaria solani, the cause of early blight of potato. Reduced sensitivity to the anilinopyrimidine (AP) fungicide pyrimethanil has also been identified recently, determining that resistance to three chemical classes of fungicides is present within the A. solani population. Although no mutations have been characterized to confer resistance to APs, in A. solani five point mutations on three AsSdh genes have been determined to convey resistance to SDHIs, and the substitution of phenylalanine with leucine at position 129 (F129L) in the cytb gene confers resistance to QoIs. The objective of this study was to investigate the parasitic fitness of A. solani isolates with resistance to one or more of these chemical classes. A total of 120 A. solani isolates collected from various geographical locations around the United States were chosen for in vitro assessment, and 60 of these isolates were further evaluated in vivo. Fitness parameters measured were (i) spore germination in vitro, (ii) mycelial expansion in vitro, and (iii) aggressiveness in vivo. No significant differences in spore germination or mycelial expansion (P = 0.44 and 0.51, respectively) were observed among wild-type and fungicide-resistant isolates in vitro. Only A. solani isolates possessing the D123E mutation were shown to be significantly more aggressive in vivo (P < 0.0001) compared with wild-type isolates. These results indicate that fungicide-resistant A. solani isolates have no significant fitness penalties compared with sensitive isolates under the parameters evaluated regardless of the presence or absence of reduced sensitivity to multiple chemical classes. Results of these studies suggest that A. solani isolates with multiple fungicide resistances may compete successfully with wild-type isolates under field conditions.

In vitro and in vivo activity of essential oils extracted from Eucalyptus staigeriana , Eucalyptus globulus and Cinnamomum camphora against Alternaria solani Sorauer causing early blight in tomato

2017 ◽  
Vol 223 ◽  
pp. 72-77 ◽  
Author(s):  
Elisa Zorzi Tomazoni ◽  
Gabriel Fernandes Pauletti ◽  
Rute Terezinha da Silva Ribeiro ◽  
Sidnei Moura ◽  
Joséli Schwambach
Keyword(s):  
Essential Oils ◽  
Eucalyptus Globulus ◽  
Early Blight ◽  
Alternaria Solani ◽  
Cinnamomum Camphora

Impact of SDH Mutations in Alternaria solani on Recently Developed SDHI Fungicides Adepidyn and Solatenol

Plant Disease ◽  
2021 ◽  
Author(s):  
Sarah Rodriguez ◽  
Rhodesia Celoy ◽  
Ipsita Mallik ◽  
Julie Sherman Pasche ◽  
Neil C Gudmestad
Keyword(s):  
Early Blight ◽  
Field Experiments ◽  
Alternaria Solani ◽  
Potato Production ◽  
Field Trials ◽  
Intrinsic Activity ◽  
In Vitro Assays ◽  
Commercial Application ◽  
Quinone Outside Inhibitor

Early blight, caused by Alternaria solani, is observed annually in all midwestern potato production areas. The use of foliar fungicides remains a primary management strategy. However, A. solani has developed reduced-sensitivity or resistance to many single-site fungicides such as quinone outside inhibitor (QoI, FRAC group 11), succinate dehydrogenase inhibitor (SDHI, FRAC group 7), demethylation inhibitors (DMI, FRAC group 3), and anilinopyrimidine (AP, FRAC group 9) fungicides. Boscalid, fluopyram, solatenol, and adepidyn are EPA-registered SDHI fungicides used commercially on a variety of crops, including potato. Five SDH mutations have been characterized previously in A. solani that affect the efficacy of boscalid while only one of these mutations has been demonstrated to negatively affect fluopyram efficacy. Conidial germination assays were used to determine if a shift in sensitivity has occurred in these SDHI fungicides. Alternaria solani isolates collected prior to the commercial application of SDHI fungicides (baseline) and were compared to recently collected isolates (non-baseline). Greenhouse evaluations were conducted also to evaluate the efficacy of boscalid, fluopyram, solatenol, and adepidyn on A. solani isolates possessing individual SDH mutations. Additionally, field trials were conducted to determine the effects application of these SDHI fungicides on the frequency of SDH mutations. Fluopyram, solatenol, and adepidyn had high intrinsic activity against A. solani when compared to boscalid, based on in vitro assays. The application of adepidyn and solatenol resulted in greater early blight control than the application of boscalid and fluopyram in greenhouse experiments. Molecular characterization of A. solani isolates collected from the field trials determined that the frequency of the H134R-mutation can increase in response to more recently developed SDHI fungicides. In contrast, the H278R/Y- and H133R-mutations decreased to the point of being nearly absent in these field experiments.

scholarly journals Efficacy of different fungicides for management of early blight disease of potato

2017 ◽  
Vol 9 (1) ◽  
pp. 280-285
Author(s):  
S. Murmu ◽  
S. Dey ◽  
A. Chakraborty
Keyword(s):  
Early Blight ◽  
Alternaria Solani ◽  
Control Measures ◽  
Antifungal Compounds ◽  
Germination Inhibition ◽  
Disease Reduction ◽  
Blight Disease ◽  
Chemical Fungicides

The early blight of potato may be controlled by using bio-control agents and plant extracts but not effectively and rapidly. But using of chemical fungicides the disease can be controlled easily and losses of yield will be reduced compare to above mentioned both control measures. Keeping this in mind an experiment was conducted to test the efficacy of seven different fungicides (difenoconazole, propiconazole, hexaconazole, propineb 61% + iprov-alicarb 5.25%, propineb, carbendazim and metalaxyl 8% + mancozeb 64%) for controlling early blight of potato un-der in vivo as well as in vitro condition. These antifungal compounds were applied 3 times at 7days interval after first appearance of the disease in the field. Highest percent disease reduction (57.88%) and highest yield of tuber (27.03 t/ha) was recorded in plot sprayed with propiconazole @1 ml/lit followed by propineb and propineb 61% + iprovalicarb 5.25%, with percent disease reduction 55.98%, 51.90% and yield 26.30 t/ha and 24.53 t/ha respectively. Simultaneously in vitro efficacy of these fungicides were also tested against Alternaria solani where propiconazole and propineb exhibited highest percent inhibition(100%) in radial growth and in case of spore germination inhibition in spite of these two fungicides difenoconazole, hexaconazole and propineb 61% + iprovalicarb 5.25% exhibit same result i.e. 100% inhibition compared to control as well as other treatments. Therefore it may be suggested that propiconazole and propineb can be used successfully in controlling of this disease.

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