Aggressiveness of Small-Spored Alternaria spp. and Their Sensitivity to Succinate Dehydrogenase Inhibitor Fungicides

Plant Disease ◽  
2022 ◽  
Author(s):  
Sarah Budde-Rodriguez ◽  
Julie Sherman Pasche ◽  
Fereshteh Shahoveisi ◽  
Ipsita Mallik ◽  
Neil C Gudmestad
Keyword(s):  
Leaf Spot ◽  
Sensu Stricto ◽  
Baseline Sensitivity ◽  
Fungicide Sensitivity ◽  
Commercial Potato ◽  
Brown Leaf Spot ◽  
Brown Leaf ◽  
Succinate Dehydrogenase Inhibitor

Brown leaf spot of potato is caused by a number of small-spored Alternaria spp. Alternaria alternata sensu stricto, Alternaria arborescens, and Alternaria tenuissima have been reported with increasing frequency in commercial potato fields. Potato cultivars with resistance to small-spored Alternaria spp. have yet to be developed; therefore, the application of foliar fungicides is a primary management strategy. Greenhouse inoculation assays demonstrated that isolates of these three small-spored Alternaria spp. were pathogenic to potato. Significant differences in aggressiveness were observed across isolates; however, there was no trend in aggressiveness based on species. Significant fungicide by isolate interactions in in vitro fungicide sensitivity and significant differences between baseline and non-baseline isolates were observed in all three small-spored Alternaria spp. The ranges of in vitro sensitivity of A. alternata baseline isolates to boscalid (EC50 <0.010 to 0.89 µg/ml), fluopyram (<0.010 to 1.14 µg/ml) and solatenol (<0.010 to 1.14 µg/ml) were relatively wide when compared to adepidyn (<0.010 to 0.023 µg/ml). The baseline sensitivity of A. arborescens and A. tenuissima isolates to all four fungicides were less than 0.065 µg/ml. Between 10 and 21% of non-baseline A. alternata isolates fell outside the baseline range established for the four SDHI fungicides evaluated. In A. arborescens, 10 to 80% of non-baseline isolates had higher sensitivities than the baseline. A. tenuissima isolates fell outside the baseline for boscalid (55%), fluopyram (14%), and solatenol (14%) but none fell outside the baseline range for adepidyn. Evaluations of in vivo fungicide efficacy demonstrated that most isolates were equally controlled by the four SDHI fungicides. However, reduced boscalid efficacy was observed for four isolates (two each of A. arborescens and A. tenuissima) and reduced fluopyram control was observed in one A. alternata isolate. Results of these studies demonstrate that isolates of all three species could be contributing to the brown leaf spot pathogen complex and that monitoring both species diversity and fungicide sensitivity could be advantageous for the management of brown leaf spot in potatoes with SDHI fungicides.

scholarly journals Sensitivity ofRhizoctonia solanito Succinate Dehydrogenase Inhibitor and Demethylation Inhibitor Fungicides

Plant Disease ◽  
2017 ◽  
Vol 101 (3) ◽  
pp. 487-495 ◽  
Author(s):  
Olutoyosi O. Ajayi-Oyetunde ◽  
Carolyn J. Butts-Wilmsmeyer ◽  
Carl A. Bradley
Keyword(s):  
Succinate Dehydrogenase ◽  
The United States ◽  
Fungicide Sensitivity ◽  
Dmi Fungicides ◽  
Soybean Plants ◽  
Succinate Dehydrogenase Inhibitor ◽  
Collection Date ◽  
Demethylation Inhibitor

Soybean seedling diseases are caused by Rhizoctonia solani and can be managed with seed-applied fungicides that belong to different chemistry classes. To provide a benchmark for assessing a decline in sensitivities to these fungicide classes, R. solani isolates collected prior to 2001 were evaluated for their sensitivities to succinate dehydrogenase inhibitor (SDHI) (penflufen and sedaxane) and demethylation inhibitor (DMI) fungicides (ipconazole and prothioconazole). The effective concentration of each fungicide that reduced mycelial growth by 50% (EC50) was determined in vitro and compared with those of isolates recovered after 2011 from soybean plants with damping off and hypocotyl and root rot symptoms across different soybean-growing regions in the United States and Canada. All isolates, regardless of collection date, were extremely sensitive (EC50< 1 μg/ml) to the SDHI fungicides but were either extremely sensitive or moderately sensitive (1 ≤ EC50≤ 10 μg/ml) to the DMI fungicides. For all four active ingredients, variation in sensitivities was observed within and among the different anastomosis groups composing both isolate groups. Isolates collected after 2011, which also had varying in vitro sensitivities, were further evaluated for in vivo sensitivity to the four fungicides in the greenhouse. In vitro fungicide sensitivity did not always coincide with fungicide efficacy in vivo because all isolates tested, regardless of in vitro sensitivity, were effectively controlled by the application of the seed treatment fungicides in the greenhouse. Overall, our results indicate no shift in sensitivity to the fungicide classes evaluated, although considerable variability in the sensitivities of the two groups of isolates examined was present. Based on this research, continued monitoring of fungicide sensitivities of R. solani populations should occur to determine whether sensitivities become further reduced in the future.

In vitro Reaction of Sunflower (Helianthus annuus L.) to the Toxin(s) Produced by Alternaria alternata, the Casual Agent of Brown Leaf Spot

1996 ◽  
Vol 144 (9-10) ◽  
pp. 465-470 ◽  
Author(s):  
S. Kintzios ◽  
A. Koliopoulos ◽  
E. Karyoti ◽  
J. Drossopoulos ◽  
C. D. Holevas ◽  
...  
Keyword(s):  
Helianthus Annuus ◽  
Alternaria Alternata ◽  
Leaf Spot ◽  
Helianthus Annuus L ◽  
Brown Leaf Spot ◽  
Brown Leaf

Recurrent Phenotypic Selection for Resistance to Brown Leaf Spot in Smooth Bromegrass 1

Crop Science ◽  
1986 ◽  
Vol 26 (3) ◽  
pp. 533-536 ◽  
Author(s):  
Clyde C. Berg ◽  
Robert T. Sherwood ◽  
Kenneth E. Zeiders
Keyword(s):  
Leaf Spot ◽  
Phenotypic Selection ◽  
Smooth Bromegrass ◽  
Brown Leaf Spot ◽  
Brown Leaf ◽  
Selection For

scholarly journals Echinococcus granulosus sensu stricto: silencing of thioredoxin peroxidase impairs the differentiation of protoscoleces into metacestodes

Parasite ◽  
2018 ◽  
Vol 25 ◽  
pp. 57 ◽  
Author(s):  
Hui Wang ◽  
Jun Li ◽  
Chuanshan Zhang ◽  
Baoping Guo ◽  
Qin Wei ◽  
...  
Keyword(s):  
Echinococcus Granulosus ◽  
Sensu Stricto ◽  
Antioxidant Defence ◽  
Culture Studies ◽  
Antioxidant Defence System ◽  
Thioredoxin Peroxidase ◽  
Survival And Growth ◽  
Echinococcus Granulosus Sensu Lato

Cystic echinococcosis (CE) is a cosmopolitan parasitic disease caused by infection with the larval stage of Echinococcus granulosus sensu lato. Thioredoxin peroxidase (TPx) may play an essential role in the antioxidant defence system of E. granulosus s.l. as neither catalase nor glutathione peroxidase activities have been detected in the parasite. However, it is not known whether TPx affects the survival and growth of E. granulosus s.l. during development. In this study, three fragments of siRNA specific for EgTPx (siRNA-1/2/3) were designed and transfected into protoscoleces of E. granulosus sensu stricto by electroporation. Quantitative real-time PCR and Western blotting analysis showed that siRNA-3 significantly reduced the expression of EgTPx. Coincidentally, knockdown of EgTPx expression in protoscoleces with siRNA-3 significantly reduced the viability of the parasite under oxidative stress induced by 0.6 mM H2O2. In vitro culture studies showed that protoscoleces treated with siRNA-3 reduced pre-microcyst formation. In vivo experiments showed that injecting mice intraperitoneally with protoscoleces treated with siRNA-3 resulted in a significant reduction in the number, size and weight of CE cysts compared with those of control animals. Silencing of EgTPx led to the impairment of growth of E. granulosus s.s. both in vitro and in vivo, indicating that EgTPx is an important factor for protoscoleces survival and plays an important role in the antioxidant defence against the host during development.

scholarly journals Bipolaris oryzae Causing Brown Leaf Spot on Echinochloa crus-galli in Southern Brazil

Plant Disease ◽  
2019 ◽  
Vol 103 (5) ◽  
pp. 1038 ◽  
Author(s):  
T. E. Kaspary ◽  
C. Bellé ◽  
C. A. G. Rigon ◽  
L. Cutti ◽  
G. Casarotto ◽  
...  
Keyword(s):  
Leaf Spot ◽  
Southern Brazil ◽  
Bipolaris Oryzae ◽  
Brown Leaf Spot ◽  
Brown Leaf

scholarly journals Fungicide Sensitivity of U.S. Genotypes of Phytophthora infestans to Six Oomycete-Targeted Compounds

Plant Disease ◽  
2015 ◽  
Vol 99 (5) ◽  
pp. 659-666 ◽  
Author(s):  
Amanda Saville ◽  
Kim Graham ◽  
Niklaus J. Grünwald ◽  
Kevin Myers ◽  
William E. Fry ◽  
...  
Keyword(s):  
United States ◽  
Phytophthora Infestans ◽  
The United States ◽  
Effective Concentration ◽  
Response Curves ◽  
Baseline Sensitivity ◽  
Fungicide Sensitivity ◽  
The Past ◽  
The Us

Phytophthora infestans causes potato late blight, an important and costly disease of potato and tomato crops. Seven clonal lineages of P. infestans identified recently in the United States were tested for baseline sensitivity to six oomycete-targeted fungicides. A subset of the dominant lineages (n = 45) collected between 2004 and 2012 was tested in vitro on media amended with a range of concentrations of either azoxystrobin, cyazofamid, cymoxanil, fluopicolide, mandipropamid, or mefenoxam. Dose-response curves and values for the effective concentration at which 50% of growth was suppressed were calculated for each isolate. The US-8 and US-11 clonal lineages were insensitive to mefenoxam while the US-20, US-21, US-22, US-23, and US-24 clonal lineages were sensitive to mefenoxam. Insensitivity to azoxystrobin, cyazofamid, cymoxanil, fluopicolide, or mandipropamid was not detected within any lineage. Thus, current U.S. populations of P. infestans remained sensitive to mefenoxam during the displacement of the US-22 lineage by US-23 over the past 5 years.

Pseudocercospora timorensis. [Descriptions of Fungi and Bacteria].

1987 ◽  
Author(s):  
S. Little
Keyword(s):  
Sweet Potato ◽  
Geographical Distribution ◽  
Leaf Spot ◽  
Ipomoea Batatas ◽  
Leaf Surface ◽  
Solomon Islands ◽  
Leaf Spots ◽  
Brown Leaf Spot ◽  
Water Splash ◽  
Brown Leaf

Abstract A description is provided for Pseudocercospora timorensis. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: Ipomoea batatas (sweet potato), I. biloba, I. campanulata, I. cordofana, I. muricata, I. peltata, I. setifera.DISEASE: Leaf spot or brown leaf spot of sweet potato. Small circular lesions first form on the leaf borders and tips before spreading over the leaf surface. These leaf spots enlarge becoming brown to dark brown in colour with a verruculose surface. The larger leaf veins may delimit the spots. GEOGRAPHICAL DISTRIBUTION: Africa: most countries; Asia: Hong-Kong, India, Indonesia, Malaysia, Taiwan; Australasia: Fiji, Papua New Guinea, Solomon Islands; North America: West Indies (St Lucia). TRANSMISSION: Presumably by wind-borne and water-splash dispersed conidia.

scholarly journals Effect of Pyrisoxazole on Colletotrichum scovillei Infection and Anthracnose on Chili

Plant Disease ◽  
2020 ◽  
Vol 104 (2) ◽  
pp. 551-559
Author(s):  
Y. Y. Gao ◽  
X. X. Li ◽  
L. F. He ◽  
B. X. Li ◽  
W. Mu ◽  
...  
Keyword(s):  
Inhibitory Activity ◽  
Infection Process ◽  
Appressorium Formation ◽  
Baseline Sensitivity ◽  
Sensitivity Curves ◽  
Half Maximal Effective Concentration ◽  
Colletotrichum Scovillei ◽  
Feasible Alternative

Anthracnose caused by Colletotrichum scovillei is one of the most destructive diseases affecting chili production. Disease control mainly relies on conventional fungicides, and repeated exposure to single-site mode-of-action fungicides may pose a risk for the development of resistant isolates within the population. Our previous study suggested that pyrisoxazole has strong inhibitory activity against C. scovillei in vitro. However, the effects of pyrisoxazole on the C. scovillei infection process and the performance of pyrisoxazole in the field remain unclear. In this study, pyrisoxazole exhibited strong inhibitory activity against the mycelial growth, appressorium formation, and appressorium diameter of C. scovillei, with half maximal effective concentration values of 0.1986, 0.0147, and 0.0269 μg/ml, respectively, but had no effect on sporulation, even at the highest concentration of 1.6 μg/ml. The baseline sensitivity curves were unimodal with a long right-hand tail. The in vivo data showed that pyrisoxazole provided both preventive and curative activity against anthracnose on chili. Pyrisoxazole decreased the incidence of anthracnose and reduced disease progress. The results of electron microscopy showed that pyrisoxazole can affect the C. scovillei infection process by altering mycelial morphology, degrading conidia and germ tubes, suppressing conidial germination and appressorium formation, and enhancing conidiophore production. Pyrisoxazole can be used to effectively control anthracnose under field conditions and increase chili yield; moreover, no phytotoxicity symptoms were observed after treatment. These results provide new insight into the mechanisms by which pyrisoxazole controls disease and suggest that pyrisoxazole is a feasible alternative for the management of anthracnose in chili.

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