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 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 Effect of the F129L Mutation in Alternaria solani on Fungicides Affecting Mitochondrial Respiration

Plant Disease ◽  
2005 ◽  
Vol 89 (3) ◽  
pp. 269-278 ◽  
Author(s):  
J. S. Pasche ◽  
L. M. Piche ◽  
N. C. Gudmestad
Keyword(s):  
Disease Control ◽  
Mitochondrial Respiration ◽  
Alternaria Solani ◽  
Complex Iii ◽  
In Vivo Studies ◽  
Cross Sensitivity ◽  
In Vitro Sensitivity ◽  
Wide Range

Isolates of Alternaria solani previously collected from throughout the Midwestern United States and characterized as being azoxystrobin sensitive or reduced sensitive were tested for sensitivity to the Quinone outside inhibitor (QoI) fungicides famoxadone and fenamidone and the carboxamide fungicide boscalid. All three fungicides affect mitochondrial respiration: famoxadone and fenamidone at complex III, and boscalid at complex II. A. solani isolates possessing reducedsensitivity to azoxystrobin also were less sensitive in vitro to famoxadone and fenamidone compared with azoxystrobin-sensitive isolates, but the shift in sensitivity was of lower magnitude, approximately 2- to 3-fold versus approximately 12-fold for azoxystrobin. The in vitro EC50 values, the concentration that effectively reduces germination by 50% relative to the untreated control, for sensitive A. solani isolates were significantly lower for famoxadone and azoxystrobin than for fenamidone and boscalid; whereas, for reduced-sensitive isolates, famoxadone EC50 values were significantly lower than all other fungicides. Isolates of A. solani with reducedsensitivity to azoxystrobin were twofold more sensitive in vitro to boscalid than were azoxystrobin-sensitive wild-type isolates, displaying negative cross-sensitivity. All isolates determined to have reduced-sensitivity to azoxystrobin also were determined to possess the amino acid substitution of phenylalanine with leucine at position 129 (F129L mutation) using real-time polymerase chain reaction. In vivo studies were performed to determine the effects of in vitro sensitivity shifts on early blight disease control provided by each fungicide over a range of concentrations. Reduced-sensitivity to azoxystrobin did not significantly affect disease control provided by famoxadone, regardless of the wide range of in vitro famoxadone EC50 values. Efficacy of fenamidone was affected by some azoxystrobin reduced-sensitive A. solani isolates, but not others. Boscalid controlled azoxystrobin-sensitive and reduced-sensitive isolates with equal effectiveness. These results suggest that the F129L mutation present in A. solani does not convey cross-sensitivity in vivo among all QoI or related fungicides, and that two- to threefold shifts in in vitro sensitivity among A. solani isolates does not appreciably affect disease control.

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.

scholarly journals Spatial and Temporal Sensitivity of Alternaria Species Associated With Potato Foliar Diseases to Demethylation Inhibiting and Anilino-Pyrimidine Fungicides

Plant Disease ◽  
2016 ◽  
Vol 100 (9) ◽  
pp. 1848-1857 ◽  
Author(s):  
D. L. Fonseka ◽  
N. C. Gudmestad
Keyword(s):  
Fungal Growth ◽  
Alternaria Solani ◽  
Potato Production ◽  
Brown Spot ◽  
Intrinsic Activity ◽  
In Vitro Assays ◽  
Baseline Sensitivity ◽  
Foliar Diseases

Early blight and brown spot, caused by Alternaria solani and Alternaria alternata, respectively, are important foliar diseases of potato, affecting both tuber yield and quality. Most of the commercial cultivars lack resistance; therefore, the application of foliar fungicides remains a primary disease management strategy. Baseline sensitivities of A. solani to difenoconazole and metconazole (demethylation inhibitors) using mycelial growth assay exhibited similar intrinsic activity against the pathogen with mean EC50 (the effective concentration at which the fungal growth is inhibited by 50%) values of 0.09 μg/ml. However, the sensitivity of individual baseline A. solani isolates to each fungicide varied substantially, resulting in very low and nonsignificant correlation coefficients among fungicides. Mean EC50 values for baseline A. alternata isolates in response to difenoconazole and metconazole were 0.14 and 0.26 μg/ml, respectively. The sensitivity of the majority of A. solani and A. alternata isolates collected from 2010 to 2014 from various potato production states was consistent with baseline isolates, therefore, these potato pathogens remain sensitive to the two demethylation inhibitor chemistries used to manage it. Baseline sensitivity assays of pyrimethanil (anilino-pyrimidine) also indicated great intrinsic activity against both foliar pathogens with mean EC50 values of 0.44 and 0.35 μg/ml for A. solani and A. alternata, respectively. Although A. alternata remains largely sensitive to pyrimethanil, 6 out of 245 A. solani isolates collected from 2010 to 2014 exhibited reduced-sensitivity to the fungicide in in vitro assays. Reduced-sensitive isolates were not controlled at most pyrimethanil doses except at 100 μg/ml in greenhouse in vivo efficacy tests. These chemistries remain valuable options for fungicide rotation programs in areas of high disease pressure.

scholarly journals Compensatory mechanisms in resistant Anopheles gambiae AcerKis and KdrKis neurons modulate insecticide-based mosquito control

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Stéphane Perrier ◽  
Eléonore Moreau ◽  
Caroline Deshayes ◽  
Marine El-Adouzi ◽  
Delphine Goven ◽  
...  
Keyword(s):  
Sodium Channel ◽  
Anopheles Gambiae ◽  
Calcium Concentration ◽  
Mosquito Control ◽  
Point Mutations ◽  
Resting Membrane Potential ◽  
Compensatory Mechanisms ◽  
Pyrethroid Insecticides

AbstractIn the malaria vector Anopheles gambiae, two point mutations in the acetylcholinesterase (ace-1R) and the sodium channel (kdrR) genes confer resistance to organophosphate/carbamate and pyrethroid insecticides, respectively. The mechanisms of compensation that recover the functional alterations associated with these mutations and their role in the modulation of insecticide efficacy are unknown. Using multidisciplinary approaches adapted to neurons isolated from resistant Anopheles gambiae AcerKis and KdrKis strains together with larval bioassays, we demonstrate that nAChRs, and the intracellular calcium concentration represent the key components of an adaptation strategy ensuring neuronal functions maintenance. In AcerKis neurons, the increased effect of acetylcholine related to the reduced acetylcholinesterase activity is compensated by expressing higher density of nAChRs permeable to calcium. In KdrKis neurons, changes in the biophysical properties of the L1014F mutant sodium channel, leading to enhance overlap between activation and inactivation relationships, diminish the resting membrane potential and reduce the fraction of calcium channels available involved in acetylcholine release. Together with the lower intracellular basal calcium concentration observed, these factors increase nAChRs sensitivity to maintain the effect of low concentration of acetylcholine. These results explain the opposite effects of the insecticide clothianidin observed in AcerKis and KdrKis neurons in vitro and in vivo.

scholarly journals Characterization of LDD-2633 as a Novel RET Kinase Inhibitor with Anti-Tumor Effects in Thyroid Cancer

2021 ◽  
Vol 14 (1) ◽  
pp. 38
Author(s):  
Hyo Jeong Lee ◽  
Pyeonghwa Jeong ◽  
Yeongyu Moon ◽  
Jungil Choi ◽  
Jeong Doo Heo ◽  
...  
Keyword(s):  
Thyroid Cancer ◽  
Thyroid Carcinoma ◽  
Kinase Inhibitor ◽  
Point Mutations ◽  
Carcinoma Cells ◽  
Medullary Thyroid ◽  
Potent Inhibition ◽  
Kinase Inhibitory Activity

Rearranged during transfection (RET), a receptor tyrosine kinase, is activated by glial cell line-derived neurotrophic factor family ligands. Chromosomal rearrangement or point mutations in RET are observed in patients with papillary thyroid and medullary thyroid carcinomas. Oncogenic alteration of RET results in constitutive activation of RET activity. Therefore, inhibiting RET activity has become a target in thyroid cancer therapy. Here, the anti-tumor activity of a novel RET inhibitor was characterized in medullary thyroid carcinoma cells. The indirubin derivative LDD-2633 was tested for RET kinase inhibitory activity. In vitro, LDD-2633 showed potent inhibition of RET kinase activity, with an IC50 of 4.42 nM. The growth of TT thyroid carcinoma cells harboring an RET mutation was suppressed by LDD-2633 treatment via the proliferation suppression and the induction of apoptosis. The effects of LDD-2633 on the RET signaling pathway were examined; LDD-2633 inhibited the phosphorylation of the RET protein and the downstream molecules Shc and ERK1/2. Oral administration of 20 or 40 mg/kg of LDD-2633 induced dose-dependent suppression of TT cell xenograft tumor growth. The in vivo and in vitro experimental results supported the potential use of LDD-2633 as an anticancer drug for thyroid cancers.

scholarly journals Inhibition of RANKL-Induced Osteoclastogenesis by Novel Mutant RANKL

2021 ◽  
Vol 22 (1) ◽  
pp. 434
Author(s):  
Yuria Jang ◽  
Hong Moon Sohn ◽  
Young Jong Ko ◽  
Hoon Hyun ◽  
Wonbong Lim
Keyword(s):  
Nuclear Translocation ◽  
Critical Role ◽  
Osteoclast Differentiation ◽  
Point Mutations ◽  
Tartrate Resistant Acid Phosphatase ◽  
Mice Model ◽  
Gsk 3Β ◽  
Rank Signaling

Background: Recently, it was reported that leucine-rich repeat-containing G-protein-coupled receptor 4 (LGR4, also called GPR48) is another receptor for RANKL and was shown to compete with RANK to bind RANKL and suppress canonical RANK signaling during osteoclast differentiation. The critical role of the protein triad RANK–RANKL in osteoclastogenesis has made their binding an important target for the development of drugs against osteoporosis. In this study, point-mutations were introduced in the RANKL protein based on the crystal structure of the RANKL complex and its counterpart receptor RANK, and we investigated whether LGR4 signaling in the absence of the RANK signal could lead to the inhibition of osteoclastogenesis.; Methods: The effects of point-mutated RANKL (mRANKL-MT) on osteoclastogenesis were assessed by tartrate-resistant acid phosphatase (TRAP), resorption pit formation, quantitative real-time polymerase chain reaction (qPCR), western blot, NFATc1 nuclear translocation, micro-CT and histomorphological assay in wild type RANKL (mRANKL-WT)-induced in vitro and in vivo experimental mice model. Results: As a proof of concept, treatment with the mutant RANKL led to the stimulation of GSK-3β phosphorylation, as well as the inhibition of NFATc1 translocation, mRNA expression of TRAP and OSCAR, TRAP activity, and bone resorption, in RANKL-induced mouse models; and Conclusions: The results of our study demonstrate that the mutant RANKL can be used as a therapeutic agent for osteoporosis by inhibiting RANKL-induced osteoclastogenesis via comparative inhibition of RANKL. Moreover, the mutant RANKL was found to lack the toxic side effects of most osteoporosis treatments.

scholarly journals Efficacy of coupling gamma irradiation with calcium chloride and lemongrass oil in maintaining guava fruit quality and inhibiting fungal growth during cold storage

2018 ◽  
Vol 30 (1) ◽  
pp. 67-78 ◽  
Author(s):  
Ramadan A. Hassanein ◽  
Ehab A. Salem ◽  
Ahmed A. Zahran
Keyword(s):  
Vitamin C ◽  
Fruit Quality ◽  
Cold Storage ◽  
Fungal Growth ◽  
Alternaria Solani ◽  
Titratable Acidity ◽  
Soluble Solids ◽  
Γ Irradiation ◽  
Lemongrass Oil

AbstractThis study was performed to explore the efficacy of combining more than one postharvest treatment in maintaining some quality attributes and reducing fungal pathogenicity in cold-stored guava fruits. The investigated postharvest treatments included the control, CaCl2(4%), lemongrass oil (2 dm3kg−1), gamma (γ) irradiation (0.2, 0.4 and 0.6 kGy), 0.4 kGy γ irradiation + CaCl2(4%), and 0.4 kGy γ irradiation + lemongrass oil (2 dm3kg−1). The studied physiochemical attributes included weight loss, decay percentage, fruit firmness, total soluble solids (TSS), titratable acidity (TA), and vitamin C content. Different fungal species were also isolated from decayed fruits and were identified asAlternaria alternata,Alternaria solani,Aspergillus niger,Botrytis cinerea,Fusarium solaniandRhizopus stolonifer. The severity of infection for the different fungi was determined, and anin vitroantifungal assay was conducted for lemongrass oil. All the investigated treatments generally reduced decay and water loss percentages, and controlled TSS, TA and vitamin C decrements that occurred during cold storage. On the other hand, higher irradiation doses generally increased fruit softness, and the 0.4 kGy γ dose did not contribute to the overall fruit quality when coupled with CaCl2and lemongrass oil, compared to CaCl2and lemongrass oil treatments alone.

scholarly journals Efeito de extratos vegetais de plantas do Cerrado para controle de pinta-preta em tomateiro

2018 ◽  
Vol 44 (2) ◽  
pp. 189-192
Author(s):  
Bruna Fukumoto Kobayashi ◽  
Daniel Rufino Amaral
Keyword(s):  
Alternaria Solani

RESUMO A “Mancha de Alternaria” causada pelo fungo Alternaria solani é uma das principais e mais frequentes doenças que incidem na cultura do tomate. Manifesta-se nas hastes, caule e principalmente nas folhas, e em alta severidade. Causa desfolha e também pode provocar infecções nos frutos, tornando-os impróprios para comercialização. Para controle da doença, os defensivos sintéticos ainda são os mais utilizados. Visando a diminuição da toxicidade ao meio ambiente e à saúde humana, surge a busca pela utilização de produtos alternativos para o controle de doenças. O objetivo do trabalho foi avaliar o efeito de extratos vegetais para o controle de Alternaria solani na cultura do tomateiro: in vivo e in vitro. O experimento foi conduzido em duas etapas: 1- in vivo (em casa de vegetação em sistema hidropônico) e 2- in vitro (em laboratório). Os tratamentos utilizados na primeira etapa foram: 1- Testemunha (sem aplicação); 2- Extrato de Assa peixe; 3- Extrato de Aroeirinha; 4- Extrato de Pata de Vaca do Cerrado; 5- Extrato de Murici, sendo estes na concentração de 10% do extrato diluído em água e outra testemunha no qual foi aplicado um fungicida (Piraclostrobina). O delineamento experimental foi em blocos ao acaso com quatro repetições. Na segunda etapa, o experimento foi conduzido em delineamento inteiramente casualizado, sendo os mesmos tratamentos da primeira, exceto o tratamento comercial. Observou-se que os extratos a base de Aroeirinha e Assa Peixe, proporcionaram controle de mancha de alternaria em plantas de tomate no experimento in vivo. Já para o experimento in vitro, pode-se observar que o extrato de Murici e Aroeirinha diminuíram o crescimento micelial do fungo.

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