An improved real-time PCR system for broad-spectrum detection of Didymella bryoniae, the causal agent of gummy stem blight of cucurbits

2010 ◽  
Vol 38 (3) ◽  
pp. 692-703 ◽  
Author(s):  
K.-S. Ling ◽  
W.P. Wechter ◽  
B.M. Somai ◽  
R.R. Walcott ◽  
A.P. Keinath
Keyword(s):  
Real Time ◽  
Broad Spectrum ◽  
Real Time Pcr ◽  
Causal Agent ◽  
Didymella Bryoniae ◽  
Stem Blight ◽  
Gummy Stem Blight ◽  
Spectrum Detection

scholarly journals Net melon resistance to Didymella bryoniae according to grafting and potassium levels

2012 ◽  
Vol 38 (2) ◽  
pp. 139-143 ◽  
Author(s):  
Edvar de Sousa da Silva ◽  
Felipe Campaner Palangana ◽  
Rumy Goto ◽  
Edson Luiz Furtado ◽  
Dirceu Maximino Fernandes
Keyword(s):  
Chemical Control ◽  
Lesion Size ◽  
Causal Agent ◽  
Didymella Bryoniae ◽  
Stem Blight ◽  
Gummy Stem Blight ◽  
Stem Lesion ◽  
Insertion Method

Chemical control of the fungus Didymella bryoniae, the causal agent of the disease gummy stem blight in melon, is frequently inefficient; thus, alternatives such as grafting and nutrition must be studied. Rootstocks and potassium levels were tested aimed at controlling this disease in net melon under protected environment. The melon hybrid 'Bônus II', ungrafted and grafted onto 'Dinero' melon and 'Strong Tosa' pumpkin rootstocks, was cultivated and inoculated by using the toothpick insertion method with 7-mm mycelial disks from the isolate D. bryoniae Dbr 37; for control, only toothpick insertion was used. The plants were subjected to the following potassium levels: 0, 62.5, 125, 187.5, 250 mg L-1. Grafted 'Bônus II' melon plants were resistant to the fungus, whereas ungrafted ones were susceptible. The adopted potassium levels did not influence the stem lesion size or the survival of plants.

Factors Promoting Pycnidia Production of Didymella bryoniae, the Causal of Gummy Stem Blight in Cucurbits

2017 ◽  
Vol 45 (1) ◽  
pp. 173-187
Author(s):  
Abdel-Fattah El-Wakil ◽  
Amal Khalil ◽  
Ibrahim El -Abbasi
Keyword(s):  
Didymella Bryoniae ◽  
Stem Blight ◽  
Gummy Stem Blight

Boscalid Insensitivity Documented in Didymella bryoniae Isolated from Watermelon in Florida and North Carolina

2012 ◽  
Vol 13 (1) ◽  
pp. 42
Author(s):  
Katherine L. Stevenson ◽  
Anthony P. Keinath ◽  
Anna Thomas ◽  
David B. Langston ◽  
Pamela D. Roberts ◽  
...  
Keyword(s):  
North Carolina ◽  
South Carolina ◽  
High Frequency ◽  
In Vitro Assays ◽  
Didymella Bryoniae ◽  
Triazole Fungicides ◽  
Stem Blight ◽  
Gummy Stem Blight ◽  
Commercial Mixture

The fungicide Pristine, a commercial mixture of pyraclostrobin and boscalid, has been used widely on watermelon and other cucurbits to control gummy stem blight, caused by the fungus Didymella bryoniae. Since 2007, isolates of D. bryoniae insensitive to boscalid have been found in Georgia, Indiana, and South Carolina. Most isolates of D. bryoniae obtained in 2009 and 2010 from diseased watermelon leaves collected in several counties in Florida and North Carolina were found to be insensitive to boscalid using in vitro assays. Gummy stem blight would not be effectively managed with Pristine in any of the counties where samples were collected due to the high frequency of insensitivity to boscalid. Fortunately growers can instead use several triazole fungicides registered for use on cucurbits since 2009. Accepted for publication 30 March 2012. Published 18 May 2012.

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 Baseline Sensitivity of Didymella bryoniae to Cyprodinil and Fludioxonil and Field Efficacy of these Fungicides Against Isolates Resistant to Pyraclostrobin and Boscalid

Plant Disease ◽  
2015 ◽  
Vol 99 (6) ◽  
pp. 815-822 ◽  
Author(s):  
Anthony P. Keinath
Keyword(s):  
South Carolina ◽  
Citrullus Lanatus ◽  
Control Treatment ◽  
Didymella Bryoniae ◽  
Water Control ◽  
Baseline Sensitivity ◽  
Qoi Fungicides ◽  
Stem Blight ◽  
Gummy Stem Blight ◽  
Development Of Resistance

To prevent yield reductions from gummy stem blight, fungicides often must be applied to watermelon (Citrullus lanatus) and muskmelon (Cucumis melo). Didymella bryoniae, the ascomycete fungus that causes gummy stem blight, is resistant to thiophanate-methyl, quinone-outside inhibitors (QoI), boscalid, and penthiopyrad. In place of these fungicides, premixtures of cyprodinil and fludioxonil (Switch 62.5WG) or cyprodinil and difenoconazole (Inspire Super 2.82SC) are used. The objectives of this study were to examine baseline isolates of D. bryoniae for sensitivity to cyprodinil and fludioxonil and to determine the efficacy of cyprodinil-fludioxonil and cyprodinil-difenoconazole against isolates resistant to QoI fungicides and boscalid. Colony diameters of 146 isolates of D. bryoniae collected in South Carolina and other U.S. states prior to 2008 were measured on glucose minimal medium amended with cyprodinil or fludioxonil. Mean effective concentration values that reduced relative colony diameter by 50% were 0.052 and 0.099 mg/liter cyprodinil and fludioxonil, respectively. In autumn 2008, 2009, and 2011, field-grown watermelon inoculated with isolates resistant to QoI fungicides and boscalid was treated with boscalid-pyraclostrobin alternated with chlorothalonil, cyprodinil-fludioxonil alternated with chlorothalonil, cyprodinil-difenoconazole alternated with chlorothalonil, tebuconazole alternated with chlorothalonil, chlorothalonil, or water. In 2008 and 2011, both cyprodinil treatments reduced disease severity compared with the water control treatment and chlorothalonil alone. In 2008 and 2009, cyprodinil-fludioxonil reduced severity compared with boscalid-pyraclostrobin and, in 2008, cyprodinil-difenoconazole and tebuconazole also did. Use of cyprodinil-fludioxonil should control gummy stem blight effectively and may delay development of resistance to cyprodinil and fludioxonil in D. bryoniae. However, because Botrytis cinerea became resistant to both cyprodinil and fludioxonil after multiple applications of cyprodinil-fludioxonil per season, prudent fungicide rotations should be followed when using cyprodinil-containing fungicides against D. bryoniae.

scholarly journals Resistance to Gummy Stem Blight in Muskmelon

HortScience ◽  
1993 ◽  
Vol 28 (9) ◽  
pp. 930-931 ◽  
Author(s):  
D.J. McGrath ◽  
L. Vawdrey ◽  
I.O. Walker
Keyword(s):  
Cucumis Melo ◽  
Didymella Bryoniae ◽  
Disease Reaction ◽  
Stem Blight ◽  
Gummy Stem Blight ◽  
Alternative Sources

Resistance to gummy stem blight [Didymella bryoniae (Auersw.) Rehm] was evaluated in two accessions of Cucumis melo L., PI 266935 and PI 266934. Based on disease reaction scores and dry weights, PI 266934 possessed much greater resistance than PI 266935. The quality of resistance of PI 266934 was unaffected by the ranges of seedling ages and inoculum concentrations used. No melon cultivar, to our knowledge, is highly resistant to gummy stem blight in the field, and alternative sources of superior resistance are potentially useful for breeding.

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