scholarly journals Sensitivity of Phytophthora nicotianae From Tobacco to Fluopicolide, Mandipropamid, and Oxathiapiprolin

Plant Disease ◽  
2016 ◽  
Vol 100 (10) ◽  
pp. 2119-2125 ◽  
Author(s):  
Tianli Qu ◽  
Yuanyuan Shao ◽  
Alexander S. Csinos ◽  
Pingsheng Ji
Keyword(s):  
Mycelial Growth ◽  
Agar Medium ◽  
Phytophthora Nicotianae ◽  
Limited Information ◽  
Growth Reduction ◽  
Pathogen Population ◽  
Baseline Sensitivity ◽  
Resistance Development ◽  
Black Shank

Black shank incited by Phytophthora nicotianae is a devastating disease in the production of tobacco. Fungicides have been commonly used for managing the disease; however, there is only a narrow pool of effective fungicides. A few new fungicides became available in recent years, including fluopicolide, mandipropamid, and oxathiapiprolin, which reduced diseases incited by oomycetes under field conditions. Limited information is available regarding sensitivity of P. nicotianae isolates to these new fungicides. Research was conducted to determine effects of the three new fungicides on P. nicotianae isolates from tobacco in Georgia. Studies with 106 isolates indicated that they did not grow when agar medium was amended with the fungicides at the rate of 1 μg/ml. Twenty isolates were used for in vitro studies to determine sensitivity to the fungicides. Fluopicolide, mandipropamid, and oxathiapiprolin inhibited mycelial growth of the isolates with mean EC50 values (effective concentrations that provide 50% growth reduction) of 0.09, 0.04, and 0.001 μg/ml, respectively. EC50 values of fluopicolide, mandipropamid, and oxathiapiprolin for inhibiting sporangial formation were 0.15, 0.03, and 0.0002 μg/ml, respectively. EC50 values for suppressing zoospore germination averaged 0.16, 0.04, and 0.002 μg/ml for fluopicolide, mandipropamid, and oxathiapiprolin, respectively. Results from the study indicated that P. nicotianae isolates from tobacco in Georgia were sensitive to the fungicides, with lower EC50 for oxathiapiprolin than for fluopicolide and mandipropamid. The information on effectiveness and baseline sensitivity of fungicides on P. nicotianae will facilitate monitoring of resistance development in the pathogen population.

scholarly journals In vitro evaluation of fungal antagonists of Phytophthora nicotianae

2017 ◽  
Vol 38 (SI 2 - 6th Conf EFPP 2002) ◽  
pp. 634-637
Author(s):  
R. Nicoletti ◽  
F. Raimo ◽  
E. Cozzolino
Keyword(s):  
Mycelial Growth ◽  
Central Italy ◽  
Phytophthora Nicotianae ◽  
Aspergillus Sydowii ◽  
Black Shank ◽  
Culture Filtrates ◽  
Dual Cultures ◽  
Penicillium Brevicompactum ◽  
Fusarium Chlamydosporum

As tobacco black shank epidemics caused by Phytophthora nicotianae occurred in central Italy in the late 1990s, fungal antagonists of the pathogen were searched in the rhizosphere of tobacco plants. Isolates of Aspergillus sydowii, Fusarium chlamydosporum, Gliocladium roseum, Penicillium brevicompactum, P. chrysogenum, Scopulariopsis candida and Trichoderma harzianum were recovered. Antagonism of these isolates toward P. nicotianae was evaluated in vitro: even if no hyphal interactions were observed in dual cultures, aberration in mycelial growth and morphology of sporangia occurred in most cases. Unlike those of T. harzianum, concentrated culture filtrates of A. sydowii, F. chlamydosporum, G. roseum, P. brevicompactum, P. chrysogenum, inhibited growth of all P. nicotianae isolates tested, while culture filtrates of S. candida caused aberrant mycelial growth.

scholarly journals Baseline Sensitivity of Penicillium spp. to Difenoconazole

Plant Disease ◽  
2019 ◽  
Vol 103 (2) ◽  
pp. 331-337 ◽  
Author(s):  
Wayne M. Jurick ◽  
Otilia Macarisin ◽  
Verneta L. Gaskins ◽  
Wojciech J. Janisiewicz ◽  
Kari A. Peter ◽  
...  
Keyword(s):  
United States ◽  
Mycelial Growth ◽  
The United States ◽  
Blue Mold ◽  
Pome Fruit ◽  
Baseline Sensitivity ◽  
Single Spore ◽  
Commercial Use ◽  
Penicillium Spp

Penicillium spp. cause blue mold of stored pome fruit. These fungi reduce fruit quality and produce mycotoxins that are regulated for processed fruit products. Control of blue mold is achieved by fungicide application, and in 2015 Academy (active ingredients fludioxonil and difenoconazole) was released for use on pome fruit to manage postharvest blue mold. Baseline sensitivity for fludioxonil but not difenoconazole has been determined for P. expansum. To establish the distribution of sensitivity to difenoconazole before commercial use of Academy, 97 unexposed single-spore isolates from the United States and abroad were tested in vitro. Baseline EC50 values ranged from 0.038 to 0.827 µg/ml of difenoconazole with an average of 0.16 µg/ml. Complete inhibition of mycelial growth for all but three isolates occurred at 5 µg/ml of difenoconazole, whereas 10 µg/ml did not support growth for any of the isolates examined. Hence, 5 µg/ml of difenoconazole is recommended for phenotyping Penicillium spp. isolates with reduced sensitivity. Isolates with resistance to pyrimethanil and to both thiabendazole and pyrimethanil were observed among the isolates from the baseline collection. Academy applied at the labeled rate had both curative and protectant activities and controlled four representative Penicillium spp. from the baseline population. This information can be used to monitor future shifts in sensitivity to this new postharvest fungicide in Penicillium spp. populations.

scholarly journals Baseline Sensitivity and Control Efficacy of Tetramycin Against Phytophthora capsici Isolates in China

Plant Disease ◽  
2018 ◽  
Vol 102 (5) ◽  
pp. 863-868 ◽  
Author(s):  
Dicheng Ma ◽  
Jiamei Zhu ◽  
Leiming He ◽  
Kaidi Cui ◽  
Wei Mu ◽  
...  
Keyword(s):  
Mycelial Growth ◽  
Southern China ◽  
Phytophthora Capsici ◽  
Environmental Safety ◽  
Phytophthora Blight ◽  
Baseline Sensitivity ◽  
Control Efficacy ◽  
Mean Values ◽  
Greenhouse Experiments

Tetramycin is a new biopesticide that combines high-level and broad-spectrum fungicidal activity, low toxicity, and environmental safety. In this study, 90 Phytophthora capsici isolates obtained from various regions in southern China were characterized for their baseline sensitivity to tetramycin. The protective and curative activities of tetramycin against P. capsici were determined on leaves of pepper, and the control efficacy of tetramycin in greenhouse experiments was also determined. Compared with mycelial growth, the formation of sporangia and the discharge of zoospores were inhibited by lower concentrations of tetramycin, approximately 5 µg ml−1 on V8 media. The frequency distribution curves for the tetramycin sensitivity were unimodal, with mean values for the fungicide concentration that reduced mycelial growth, sporangia formation, and zoospore discharge by 50% compared with the control of 1.18 ± 0.91, 0.64 ± 0.42, and 0.63 ± 0.30 µg ml−1, respectively. In addition, no correlation was observed between tetramycin and other fungicides tested, including mandipropamid, azoxystrobin, mefenoxam, fluazinam, fluopicolide, and famoxadone. Tetramycin exhibited both protective and curative effects against P. capsici in vitro, and its protective activity was better than its curative activity. In greenhouse experiments, tetramycin concentration of 60 and 90 µg ml−1 provided a protective control efficacy of 47.1 to 56.4% and curative efficacy of 43.3 to 52.7%. These results demonstrated that tetramycin could serve as an excellent alternative fungicide to control Phytophthora blight of pepper.

scholarly journals In vitro study of baseline sensitivity of important fungi against different fungicides

2012 ◽  
Vol 4 (2) ◽  
pp. 264-265 ◽  
Author(s):  
Sanjay Goswami ◽  
R. Kaur ◽  
Dipak T. Nagrale
Keyword(s):  
Botrytis Cinerea ◽  
Alternaria Alternata ◽  
In Vitro Study ◽  
Phytopathogenic Fungi ◽  
Plant Diseases ◽  
Baseline Sensitivity ◽  
Resistance Development ◽  
Gloeosporium Ampelophagum ◽  
Mic Value

Baseline sensitivity values of important phytopathogenic fungi were studied against fungicides. ED50, ED90 and MIC value of propiconazole for, Colletotrichum capsici, and Gloeosporium ampelophagum was in the range of 0.020-0.04 μg/ml. ED50 values of tebuconazole for Alternaria alternata was 30.0 μg/ml. Azoxystrobin was also tested for its ED50, ED90 and MIC values against Alternaria alternata, C. capsici, G. ampelophagum and Botrytis cinerea where the values were in the range of 0.019-50.0, 0.03-60.0 and 0.2-100.0 μg/ml respectively. Baseline sensitivity values are important for the management of plant diseases and resistance development.

scholarly journals Baseline Sensitivity of Guignardia citricarpa Isolates from Florida to Azoxystrobin and Pyraclostrobin

Plant Disease ◽  
2014 ◽  
Vol 98 (6) ◽  
pp. 780-789 ◽  
Author(s):  
Martha Hincapie ◽  
Nan-Yi Wang ◽  
Natalia A. Peres ◽  
Megan M. Dewdney
Keyword(s):  
Mycelial Growth ◽  
Control Measure ◽  
Black Spot ◽  
Conidial Germination ◽  
Baseline Sensitivity ◽  
Qoi Fungicides ◽  
Resistance Risk ◽  
Guignardia Citricarpa ◽  
The Mean

Citrus black spot (CBS), caused by Guignardia citricarpa, is an emerging disease in Florida. Fungicide applications are the main control measure worldwide. The in vitro activity and baseline sensitivity of G. citricarpa isolates to quinone outside inhibitor (QoI) fungicides (azoxystrobin and pyraclostrobin) were evaluated. The effective concentration needed to reduce mycelial growth or spore germination by 50% (EC50) was determined for 86 isolates obtained from Florida counties where CBS is found. The effect of salicylhydroxamic acid (SHAM) plus azoxystrobin and pyraclostrobin was also assessed for mycelial growth and conidial germination. The mean EC50 for mycelial growth for azoxystrobin was 0.027 μg/ml and that for pyraclostrobin was significantly lower at 0.007 μg/ml (P < 0.0001). Similarly, the mean EC50 for conidial germination for azoxystrobin was 0.016 μg/ml and that for pyraclostrobin was significantly lower at 0.008 μg/ml (P < 0.0001). There was no effect of SHAM on inhibition of mycelial growth or conidial germination by the QoI fungicides but SHAM slightly affected mycelium inhibition by pyraclostrobin. Cytochrome b was partially sequenced and three group 1 introns were found. One intron was immediately post G143, likely inhibiting resistance-conferring mutations at that site. It is surmised that the QoI resistance risk is low in the Florida G. citricarpa population.

scholarly journals Stepwise-Selected Bacillus amyloliquefaciens and B. subtilis Strains from Composted Aromatic Plant Waste Able to Control Soil-Borne Diseases

Agriculture ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 30
Author(s):  
Massimo Zaccardelli ◽  
Roberto Sorrentino ◽  
Michele Caputo ◽  
Riccardo Scotti ◽  
Enrica De Falco ◽  
...  
Keyword(s):  
Bacillus Amyloliquefaciens ◽  
Mycelial Growth ◽  
Phytopathogenic Fungi ◽  
Cultivated Plants ◽  
Aromatic Plant ◽  
Growth Reduction ◽  
Gene Sequence Analysis ◽  
Reference Strains

In the present study, 133 bacterial isolates from 11 composted aromatic plant wastes were selected for their ability to inhibit the mycelial growth of the soil-borne phytopathogenic fungi Sclerotinia minor and Rhizoctonia solani. Successively, a subset of 35 from them were further characterized for their ability to control, in vivo, rocket damping-off caused by the two fungi. Moreover, the isolates were characterized for morphology of the colonies, Gram reaction, siderophore production, P-solubilization and for the presence of antimicrobial lipopeptide genes in the genome. The screening for the in vitro antagonisms showed a mycelial growth reduction ranging between 31.7% and 56.1% for R. solani and 34.4% and 59.4% for S. minor. All the isolates were not able to produce siderophores and some of them were able to solubilize P. The isolates contained two or more of the five lipoproteins coding genes investigated in this study. The most promising isolates were identified at species level by 16S-rRNA partial gene sequence analysis and were grouped in two main clusters related to Bacillus subtilis and Bacillus amyloliquefaciens reference strains. Results indicated that Bacillus isolates from compost are good candidates for application in the biocontrol of cultivated plants.

scholarly journals Baseline Sensitivity of Fusarium virguliforme to Fluopyram Fungicide

Plant Disease ◽  
2017 ◽  
Vol 101 (4) ◽  
pp. 576-582 ◽  
Author(s):  
Jie Wang ◽  
Carl A. Bradley ◽  
Olivia Stenzel ◽  
Dianne K. Pedersen ◽  
Ursula Reuter-Carlson ◽  
...  
Keyword(s):  
Growth Inhibition ◽  
Mycelial Growth ◽  
Soybean Seed ◽  
Inhibition Assay ◽  
Baseline Sensitivity ◽  
Growth Inhibition Assay ◽  
Fusarium Virguliforme ◽  
Fungicide Sensitivity ◽  
Conidia Germination

Fluopyram, a succinate dehydrogenase inhibitor (SDHI) fungicide, was recently registered for use as a soybean seed treatment for management of sudden death syndrome (SDS) caused by Fusarium virguliforme. Although registered and now used commercially, in vitro baseline fungicide sensitivity of F. virguliforme to fluopyram has not yet been established. In this study, the baseline sensitivity of F. virguliforme to fluopyram was determined using in vitro growth of mycelium and germination of conidia assays with two collections of F. virguliforme isolates. A total of 130 and 75 F. virguliforme isolates were tested using the mycelial growth and conidia germination assays, respectively, including a core set of isolates that were tested with both assays. In the mycelial growth inhibition assay, 113 out of 130 isolates (86.9%) were inhibited 50% by effective concentrations (EC50) less than 5 µg/ml with a mean EC50 of 3.35 µg/ml. For the conidia germination assay, 73 out of 75 isolates (97%) were determined to have an estimated EC50 of less than 5 µg/ml with a mean EC50 value of 2.28 µg/ml. In a subset of 20 common isolates that were phenotyped with both assays, conidia germination of F. virguliforme was determined to be more sensitive to fluopyram (mean EC50 = 2.28 µg/ml) than mycelial growth (mean EC50 = 3.35 µg/ml). Hormetic effects were observed in the mycelial growth inhibition assay as 22% of the isolates demonstrated more growth on medium amended with the lowest fluopyram concentration (1 µg/ml), as compared with the nonfluopyram amended control. It was not possible to determine EC50 values for nine out of 185 isolates (4.8%), as those isolates were not inhibited by 50% even at the highest fluopyram concentrations of 100 µg/ml for mycelial growth and 20 µg/ml for conidia germination inhibition assays. On the whole, the F. virguliforme population appears to be sensitive to fluopyram, and this study enables future monitoring of fungicide sensitivity.

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

2018 ◽  
Vol 54 (No. 2) ◽  
pp. 101-110 ◽  
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 EC<sub>50 </sub>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 EC<sub>50</sub> value 0.05856 µl/ml and then the remaining fungicides Propulse, Efilor, and Horizon 250 EW (EC<sub>50</sub> values 0.07277, 0.07221, and 0.08519 µl/ml, respectively).

scholarly journals The Tobacco Trichome Exudate Z-abienol and Its Relationship With Plant Resistance to Phytophthora nicotianae

Plant Disease ◽  
2017 ◽  
Vol 101 (7) ◽  
pp. 1214-1221 ◽  
Author(s):  
William T. Steede ◽  
Justin M. Ma ◽  
David P. Eickholt ◽  
Katherine E. Drake-Stowe ◽  
Sheri P. Kernodle ◽  
...  
Keyword(s):  
Close Association ◽  
Hyphal Growth ◽  
Field Resistance ◽  
Phytophthora Nicotianae ◽  
In Vitro Assays ◽  
Black Shank ◽  
Plant Parts ◽  
Tobacco Cultivar ◽  
High Level

In previous research, we discovered a favorable quantitative trait locus (QTL) in cigar tobacco cultivar ‘Beinhart 1000’ designated as Phn15.1, which provides a high level of partial resistance to the black shank disease caused by Phytophthora nicotianae. A very close genetic association was also found between Phn15.1 and the ability to biosynthesize Z-abienol, a labdanoid diterpene exuded by the trichomes onto above-ground plant parts, and that imparts flavor and aroma characteristics to Oriental and some cigar tobacco types. Because accumulation of Z-abienol is considered to be undesirable for cultivars of other tobacco types, we herein describe a series of experiments to gain insight on whether this close association is due to genetic linkage or pleiotropy. First, in an in vitro bioassay, we observed Z-abienol and related diterpenes to inhibit hyphal growth of P. nicotianae at concentrations between 0.01 and 100 ppm. Secondly, we field-tested transgenic versions of Beinhart 1000 carrying RNAi constructs for downregulating NtCPS2 or NtABS, two genes involved in the biosynthesis of Z-abienol. Thirdly, we also field tested a recombinant inbred line population segregating for a truncation mutation in NtCPS2 leading to an interrupted Z-abienol pathway. We observed no correlation between field resistance to P. nicotianae and the ability to accumulate Z-abienol in either the transgenic materials or the mapping population. Results suggest that, although Z-abienol may affect P. nicotianae when applied at high concentrations in in vitro assays, the compound has little effect on black shank disease development under natural field conditions. Thus, it should be possible to disassociate Phn15.1-mediated black shank resistance identified in cigar tobacco cultivar Beinhart 1000 from the ability to accumulate Z-abienol, an undesirable secondary metabolite for burley and flue-cured tobacco cultivars.

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