Comparing the Fungicide Sensitivity of Sclerotinia sclerotiorum Using Mycelial Growth and Ascospore Germination Assays

Plant Disease ◽  
2021 ◽  
Author(s):  
Miller da Silva Lehner ◽  
Kaique Alves ◽  
Emerson Medeiros Del Ponte ◽  
Sarah Jane Pethybridge
Keyword(s):  
Sclerotinia Sclerotiorum ◽  
Mode Of Action ◽  
Mycelial Growth ◽  
White Mold ◽  
Fungicide Sensitivity ◽  
Snap Bean ◽  
Thiophanate Methyl ◽  
Ascospore Germination ◽  
Sensitivity Tests

The infection of the floral tissues of snap bean and other crops by Sclerotinia sclerotiorum, the causative agent of white mold, is by ascospores. Irrespective of the fungicide mode of action being evaluated, in vitro fungicide sensitivity tests are conducted almost exclusively using mycelial growth assays. This is likely due to difficulties and time involved in sclerotial conditioning required to produce apothecia and ascospores. The objective of this research was to compare estimates of fungicide sensitivity between mycelial growth and ascospore germination assays for S. sclerotiorum. Sensitivity assays were conducted using serial doses of three fungicides commonly used to control white mold: boscalid, fluazinam, and thiophanate-methyl. A total of 27 isolates were evaluated in replicated trials conducted for each fungicide and assay type. The effective concentration to reduce mycelial growth or ascospore germination by 50% (EC50) was estimated for each isolate, fungicide, assay type, and trial. The median EC50 values obtained from ascospore germination assays were 52.7, 10.0, and 2.7 times higher than those estimated from the mycelial growth for boscalid, fluazinam, and thiophanate-methyl, respectively. No significant correlation was found between EC50 values estimated by the two methods. These findings highlight differences that may be important in evaluating the sensitivity of S. sclerotiorum given the fungicide mode of action and how they will be used in the field.

scholarly journals Sensitivity and Efficacy of Boscalid, Fluazinam, and Thiophanate-Methyl for White Mold Control in Snap Bean in New York

Plant Disease ◽  
2017 ◽  
Vol 101 (7) ◽  
pp. 1253-1258 ◽  
Author(s):  
M. S. Lehner ◽  
E. M. Del Ponte ◽  
B. K. Gugino ◽  
J. R. Kikkert ◽  
S. J. Pethybridge
Keyword(s):  
New York ◽  
Growth Inhibition ◽  
Mycelial Growth ◽  
Point Mutations ◽  
Field Trials ◽  
White Mold ◽  
Dilution Method ◽  
Agar Dilution Method ◽  
Snap Bean ◽  
Thiophanate Methyl

White mold (Sclerotinia sclerotiorum) of leguminous crops in New York is generally managed with preventive applications of fungicides. However, no research has been conducted during the last decade to assess the sensitivity of the S. sclerotiorum population to fungicides or compare their performance under field conditions. The sensitivity of S. sclerotiorum to boscalid, fluazinam, and thiophanate-methyl was assessed in 151 isolates from 15 fields across New York using an agar dilution method with discriminatory concentrations. In addition, the effective concentration at which mycelial growth is reduced by 50% (EC50) was estimated for one representative isolate from each field. The efficacy of commercial formulations of each fungicide on white mold incidence in plants and pods was also tested in two field trials (2015 and 2016). The EC50 values ranged from 0.068 to 0.219, 0.001 to 0.002, and 1.23 to 2.15 µg/ml for boscalid, fluazinam, and thiophanate-methyl, respectively. Evidence of resistance was not found using the discriminatory concentration tests. The mycelial growth inhibition relative to the control ranged from 56 to 83%, 66 to 84%, and 53 to 83% at discriminatory concentrations of boscalid (5 µg a.i./ml), fluazinam (0.05 µg a.i./ml), and thiophanate-methyl (5 µg a.i./ml), respectively. Fourteen isolates with mycelial growth inhibition lower than 60% at 5 µg/ml of thiophanate-methyl, did not exhibit point mutations within a partial sequence of the β-tubulin gene. In the field trials, fungicides effectively reduced white mold incidence on plants by 75% (2015) and 93% (2016) and on pods by 81% (2015) and 87% (2016), both relative to the nontreated plots. However, fungicide applications led to significant increases in pod yield, relative to the nontreated plots, only in 2015 when the incidence of white mold on plants and pods were higher (85 and 49.2%) than in 2016 (31.3 and 10.3%). Although fungicide resistance was not detected, and thus control failures reported by New York snap bean growers may be due to other factors, further monitoring of sensitivity within the S. sclerotiorum population is encouraged as well as the use of rational systems to base their judicious and economic use.

Alternative and sustainable control of the fungus Sclerotinia sclerotiorum that causes white mold in soybeans

2021 ◽  
Author(s):  
Sergio E. Lemos da Silva ◽  
Kimberlly Soares Brito Bratifich ◽  
eloisa Teresa Corradini Santos
Keyword(s):  
Sclerotinia Sclerotiorum ◽  
Agricultural Production ◽  
Mycelial Growth ◽  
Direct Relationship ◽  
White Mold ◽  
Phytopathogenic Fungus ◽  
Environmental Damage ◽  
In Vitro Growth ◽  
Negative Effect

The Sclerotinia sclerotiorum is a phytopathogenic fungus that causes the White Mold of soybean, being responsible for losses of up to 100% in agricultural production. The objective of this work was to verify and analyze the effect of the raw aqueous extract (EBA) of ginger Zingiber officinalis on a strain of Sclerotinia Sclerotiorum isolated from soybean, cultivated and maintained in vitro in laboratory. The methodology consisted of a longitudinal study of the statistical analysis of the mycelial growth velocity index (MICV), after treatment of the mycelia with different concentrations of aqueous crude extract. The results showed a direct relationship between increasing concentration of EBA and a significant negative effect on the growth of scleroderia. It was possible to conclude that the antifungal activity of ginger EBA was able to inhibit the in vitro growth of Sclerotinia sclerotiorum, with potential protection of soybean crops; it can become a sustainable alternative in the control of this fungus, by decreasing the use of agrochemicals that cause damage to public health and environmental damage.

Interactions between Sclerotinia sclerotiorum and Epicoccum purpurascens

1991 ◽  
Vol 69 (11) ◽  
pp. 2503-2510 ◽  
Author(s):  
Ting Zhou ◽  
R. D. Reeleder ◽  
S. A. Sparace
Keyword(s):  
Sclerotinia Sclerotiorum ◽  
Mycelial Growth ◽  
Germ Tube ◽  
Hyphal Growth ◽  
White Mold ◽  
Antifungal Compounds ◽  
Sterile Culture ◽  
Pod Yield ◽  
Culture Filtrates ◽  
Ascospore Germination

Sterile culture filtrates of Epicoccum purpurascens decreased severity of white mold of bean and increased pod yield when applied prior to inoculation of beans with Sclerotinia sclerotiorum. Extracts of these culture filtrates inhibited ascospore germination and mycelial growth of S. sclerotiorum. Similar inhibition of hyphal growth of S. sclerotiorum occurred when dual cultured with E. purpurascens. Contact and penetration of hyphae of S. sclerotiorum by hyphae of E. purpurascens occurred rarely on agar-covered slides and was not observed on flower petals. Inhibition of ascospore germination and germ-tube elongation occurred on agar-covered slides where E. purpurascens had been grown previously; however, addition of nutrients decreased inhibition. Colonization of bean flowers by E. purpurascens reduced white mold incidence. The degree of disease control was affected by addition of nutrients and whether or not colonized flowers were autoclaved. Key words: antifungal compounds, competition, biological control, white mold, Phaseolus.

scholarly journals Antagonism of saprobe fungi from semiarid areas of the Northeast of Brazil against Sclerotinia sclerotiorum and biocontrol of soybean white mold

2020 ◽  
Vol 41 (6) ◽  
pp. 2597-2612
Author(s):  
Douglas Casaroto Peitl ◽  
◽  
Ciro Hideki Sumida ◽  
Ricardo Marcelo Gonçalves ◽  
Sérgio Florentino Pascholati ◽  
...  
Keyword(s):  
Sclerotinia Sclerotiorum ◽  
Mycelial Growth ◽  
Antagonistic Activity ◽  
White Mold ◽  
Saprobe Fungi ◽  
Progress Curve ◽  
Ascospore Germination ◽  
Semiarid Areas ◽  
Soybean Plants ◽  
Commercial Fungicide

The antagonistic activity of 25 saprobe fungi from semiarid areas of Northeast Brazil was evaluated against Sclerotinia sclerotiorum (Lib.) de Bary (Helotiales: Sclerotiniaceae). Four fungi [Myrothecium sp. Tode (Hypocreales: Stachybotryaceae) isolate 2, Volutella minima Höhn. (Hypocreales: Nectriaceae), Phialomyces macrosporus P.C. Misra & P.H.B. Talbot (Pezizomycotina) and Dictyosporium tetraseriale Goh, Yanna & K.D. Hyde (Pleosporales: Dictyosporiaceae)] were selected and further tested their ability to inhibit mycelial growth, sclerotia formation and ascospore germination of S. sclerotiorum and to control white mold on soybean plants. V. minima and P. macrosporus filtrates at 50% effectively suppressed mycelial growth and Myrothecium sp. isolate 2 completely suppressed sclerotia formation and inhibited ascospore germination by over 95%, the same result as commercial fungicide fluazinam. Soybean plants pre-treated with Myrothecium sp. isolate 2, P. macrosporus, and V. minima and inoculated with S. sclerotiorum showed a reduction of 55.8%, 79.7%, and 83.2% of area under disease progress curve (AUDPC) of white mold, respectively, in relation to water. Collectively, these results underline the antagonistic activity of V. minima, P. macrosporus, and Myrothecium sp. isolate 2 against S. sclerotiorum and their potential as biocontrol agents of soybean white mold.

scholarly journals Chemical composition and in vitro inhibitory effects of essential oils from fruit peel of three Citrus species and limonene on mycelial growth of Sclerotinia sclerotiorum

2020 ◽  
Vol 80 (2) ◽  
pp. 460-464 ◽  
Author(s):  
A. L. B. Dias ◽  
W. C. Sousa ◽  
H. R. F. Batista ◽  
C. C. F. Alves ◽  
E. L. Souchie ◽  
...  
Keyword(s):  
Essential Oils ◽  
Sclerotinia Sclerotiorum ◽  
Mycelial Growth ◽  
Major Constituent ◽  
Citrus Species ◽  
Fruit Peel ◽  
Diverse Range ◽  
Citrus Peel ◽  
Fungus Growth

Abstract Essential oils (EO) from aromatic and medicinal plants generally perform a diverse range of biological activities because they have several active constituents that work in different mechanisms of action. EO from Citrus peel have an impressive range of food and medicinal uses, besides other applications. EO from Citrus reticulata, C. sinensis and C. deliciosa were extracted from fruit peel and analyzed by GC-MS. The major constituent of EO under evaluation was limonene, whose concentrations were 98.54%, 91.65% and 91.27% for C. sinensis, C. reticulata and C. deliciosa, respectively. The highest potential of inhibition of mycelial growth was observed when the oil dose was 300 μL. Citrus oils inhibited fungus growth in 82.91% (C. deliciosa), 65.82% (C. sinensis) and 63.46% (C. reticulata). Anti-Sclerotinia sclerotiorum activity of 90% pure limonene and at different doses (20, 50, 100, 200 and 300 μL) was also investigated. This monoterpene showed to be highly active by inhibiting 100% fungus growth even at 200 and 300 μL doses. This is the first report of the in vitro inhibitory effect of natural products from these three Citrus species and its results show that there is good prospect of using them experimentally to control S. sclerotiorum, in both greenhouse and field conditions.

scholarly journals Effects of SHAM on the Sensitivity of Sclerotinia sclerotiorum and Botrytis cinerea to QoI Fungicides

Plant Disease ◽  
2019 ◽  
Vol 103 (8) ◽  
pp. 1884-1888 ◽  
Author(s):  
Hongjie Liang ◽  
Jinli Li ◽  
Chaoxi Luo ◽  
Jianhong Li ◽  
Fu-Xing Zhu
Keyword(s):  
Botrytis Cinerea ◽  
Sclerotinia Sclerotiorum ◽  
Mycelial Growth ◽  
Control Efficacy ◽  
Vitro Assay ◽  
Qoi Fungicides ◽  
Quinone Outside Inhibitor ◽  
Fungal Phytopathogens ◽  
The Ideal

It is a common practice to add salicylhydroxamic acid (SHAM) into artificial medium in the in vitro sensitivity assay of fungal phytopathogens to the quinone outside inhibitor (QoI) fungicides. The rationale for adding SHAM is to inhibit fungal alternative oxidase, which is presumed to be inhibited by secondary metabolites of plants. Therefore, the ideal characteristics of SHAM should be almost nontoxic to phytopathogens and have no significant effect on control efficacy of fungicides. However, this study showed that the average effective concentration for 50% inhibition (EC50) of mycelial growth values of SHAM were 97.5 and 401.4 μg/ml for Sclerotinia sclerotiorum and Botrytis cinerea, respectively. EC50 values of the three QoI fungicides azoxystrobin, kresoxim-methyl, and trifloxystrobin in the presence of SHAM at 20 and 80 μg/ml for S. sclerotiorum and B. cinerea, respectively, declined by 52.7 to 78.1% compared with those without SHAM. For the dicarboximide fungicide dimethachlone, the average EC50 values in the presence of SHAM declined by 18.2% (P = 0.008) for S. sclerotiorum and 35.9% (P = 0.012) for B. cinerea. Pot experiments showed that SHAM increased control efficacy of the three QoI fungicides against the two pathogens by 43 to 83%. For dimethachlone, SHAM increased control efficacy by 134% for S. sclerotiorum and 86% for B. cinerea. Biochemical studies showed that SHAM significantly inhibited peroxidase activity (P = 0.024) of B. cinerea and esterase activity (P = 0.015) of S. sclerotiorum. The strong inhibitions of SHAM per se on mycelial growth of B. cinerea and S. sclerotiorum and significant influences on the sensitivity of the two pathogens to both the QoI fungicides and dimethachlone as well as inhibitions on peroxidase and esterase indicate that SHAM should not be added in the in vitro assay of sensitivity to the QoI fungicides.

scholarly journals Relationship Between Fungicide Sensitivity and Control of Gummy Stem Blight of Watermelon Under Field Conditions

Plant Disease ◽  
2012 ◽  
Vol 96 (12) ◽  
pp. 1780-1784 ◽  
Author(s):  
A. Thomas ◽  
D. B. Langston ◽  
H. F. Sanders ◽  
K. L. Stevenson
Keyword(s):  
Fungicide Resistance ◽  
Field Experiments ◽  
In Vitro Assays ◽  
Didymella Bryoniae ◽  
Fungicide Sensitivity ◽  
Thiophanate Methyl ◽  
Stem Blight ◽  
Gummy Stem Blight ◽  
And Control

Gummy stem blight (GSB), caused by the fungus Didymella bryoniae, is the most destructive disease of watermelon and is managed primarily with fungicides. D. bryoniae has developed resistance to many fungicides that were once very effective, including azoxystrobin, boscalid, and thiophanate-methyl. Field experiments were conducted in Tifton (TN) and Reidsville (RV), GA in 2009 and 2010 to establish a relationship between frequency of resistance to a fungicide based on in vitro assays and its efficacy in the management of GSB. Frequency of resistance to boscalid, thiophanate-methyl, and azoxystrobin was >0.80 in isolates collected from nontreated plots in both locations and years. All isolates collected after six applications of boscalid, thiophanate-methyl, or azoxystrobin were resistant to the respective fungicide. All isolates collected from treated and nontreated plots were sensitive to tebuconazole and difenoconazole. GSB severity was assessed on a weekly basis from 63 days after planting. GSB severity in plots treated with boscalid, thiophanate-methyl, or azoxystrobin was not significantly different from that in the nontreated plots (39%, TN-2009; 45%, TN-2010; and 16%, RV-2010). GSB severity in tebuconazole-treated plots (27%, TN-2009; 14%, TN-2010; and 4%, RV-2010) was significantly lower than all other treatments and the nontreated control. There was a consistent negative association between frequency of fungicide resistance and disease control in the field. Thus, knowledge of the frequency of fungicide resistance in the pathogen population will be helpful in selecting the most effective fungicides for the management of GSB in watermelon fields.

scholarly journals Effects of post-emergent herbicides on Trichoderma harzianum , a potential biocontrol agent against Sclerotinia sclerotiorum in soybean cropping

2007 ◽  
Vol 55 (3) ◽  
pp. 355-362
Author(s):  
M. Rollán ◽  
C. Mónaco ◽  
G. Lampugnani ◽  
N. Arteta ◽  
D. Bayo ◽  
...  
Keyword(s):  
Sclerotinia Sclerotiorum ◽  
Trichoderma Harzianum ◽  
Mycelial Growth ◽  
Detrimental Effect ◽  
Biocontrol Agent ◽  
Selective Medium ◽  
Potential Biocontrol Agent ◽  
Colony Forming Units ◽  
Soil Dilution

Trichoderma harzianum is a potential biocontrol agent against Sclerotinia sclerotiorum in soybean. Information is needed on the compatibility of this biocontrol agent and the post-emergent herbicides used in soybean cropping.Haloxyfop R Methyl (EC 10.4%), Glyphosate (SL 48%), Imazamox (WG 70%) and Imazethapyr (SL 10%) were evaluated for their effects on the mycelial growth of T. harzianum on in vitro agar plates. Glyphosate (2000 ppm), Imazethapyr (500 and 250 ppm) and Haloxyfop R Methyl (1000, 500 and 100 ppm) reduced the mycelial growth of T. harzianum . Imazamox had no effect at any concentration.Subsequently, all the herbicides were assessed for their effect on soil populations of T. harzianum . Greenhouse assays conducted with non-sterile soil inoculated with T. harzianum and a specific herbicide were sampled before pesticide application and after 30 days. The number of colony forming units per gram of soil (c.f.u./g of soil) was evaluated with a soil dilution technique using Trichoderma selective medium (TSM). No detrimental effect was revealed.

White mold (Sclerotinia sclerotiorum), friend or foe: Cytotoxic and mutagenic activities in vitro and in vivo

2016 ◽  
Vol 80 ◽  
pp. 27-35 ◽  
Author(s):  
Luciana Azevedo ◽  
Daniela Aparecida Chagas-Paula ◽  
Hyemee Kim ◽  
Aline Cristina Monteiro Roque ◽  
Kris Simone Tranches Dias ◽  
...  
Keyword(s):  
Sclerotinia Sclerotiorum ◽  
White Mold

scholarly journals Screening for Partial Physiological Resistance to White Mold in Dry Bean Using Excised Stems

1992 ◽  
Vol 117 (2) ◽  
pp. 321-327 ◽  
Author(s):  
P.N. Miklas ◽  
K.F. Grafton ◽  
B.D. Nelson
Keyword(s):  
Phaseolus Vulgaris ◽  
Sclerotinia Sclerotiorum ◽  
Field Resistance ◽  
White Mold ◽  
Lesion Length ◽  
Laboratory Procedure ◽  
Dry Bean ◽  
Snap Bean ◽  
Breeding Lines ◽  
Physiological Resistance

A laboratory procedure was tested to determine whether excised stems would allow a reliable indication of partial physiological resistance (PPR) to white mold [Sclerotinia sclerotiorum (Lib.) deBary] in dry bean (Phaseolus vulgaris L.). Excised stems from 11- and 28-day-old plants were inoculated with growing mycelium of S. sclerotiorum, incubated for 4 to 7 days (11- and 28-day assays, respectively), then assayed for lesion length (LL). A total of 15 bean genotypes were screened for PPR, as indicated by LL. Significant (P < 0.05) differences among LL means of small- and medium-seeded bean genotypes were detected in the 28-day assay, whereas only LL means among medium-seeded genotypes. differed significantly (P < 0.05) in the n-day assay. `Bunsi', `C-20', `Sierra', `Topaz', and snap bean breeding lines NY 5262, NY 5394, and NY 5403 had the highest PPR and `Upland', D76125, and `UI-114' the lowest. The results from both assays were repeatable. A moderately high correlation (r = 0.68, P < 0.02) was observed between PPR and field resistance. The 28-day assay has potential for evaluating dry bean germplasm for PPR to white mold disease caused by S. sclerotiorum. A 28-day assay also was used to measure virulence of 18 isolates of S. sclerotiorum. The 18 isolates did not differ (P < 0.05) for virulence when measured by LL. The lack of any genotype × isolate interaction for LL indicated lack of host-pathogen specificity.

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