Efficacy of Fungicides and Culture Filtrate of Native Bioagents against Didymella bryoniae Causing Gummy Stem Blight Disease in Gherkin

The fungus Didymella bryoniae causes gummy stem blight (foliar phase) and black rot (fruit phase) in cucurbits. As resistance to other diseases have been incorporated into cucurbits, losses due to gummy stem blight have increased. Populations derived from crosses between a cultivated watermelon (SS-4), susceptible to the fungus Didymella bryoniae and resistant plant introduction accessions (PI 189225 and PI 272778) are used to detect molecular markers linked to gummy stem blight disease resistance. Genomic DNA was purified from primary leaves of watermelon seedlings before seedlings were inoculated with a spore suspension of the fungus. Disease severity was rated 4 days after inoculation. DNA bulked from resistant or susceptible BC seedlings was amplified to detect AFLP markers. Linkages between gummy stem blight resistance and AFLP markers were identified and should facilitate evaluation and selection of watermelon populations segregating for gummy stem blight resistance.

Download Full-text

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

Egyptian Journal of Phytopathology ◽

10.21608/ejp.2017.89736 ◽

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

Download Full-text

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

Plant Health Progress ◽

10.1094/php-2012-0518-01-br ◽

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.

Download Full-text

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

Plant Disease ◽

10.1094/pdis-02-12-0129-re ◽

2012 ◽

Vol 96 (12) ◽

pp. 1780-1784 ◽

Cited By ~ 13

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.

Download Full-text

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

Plant Disease ◽

10.1094/pdis-09-14-0993-re ◽

2015 ◽

Vol 99 (6) ◽

pp. 815-822 ◽

Cited By ~ 13

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.

Download Full-text

Resistance to Gummy Stem Blight in Muskmelon

HortScience ◽

10.21273/hortsci.28.9.930 ◽

1993 ◽

Vol 28 (9) ◽

pp. 930-931 ◽

Cited By ~ 13

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.

Download Full-text

Evaluation of Resistance to Gummy Stem Blight (Didymella bryoniae) Disease in ipt (Isopentenyl Transferase) Transformed Watermelon Plants

HortScience ◽

10.21273/hortsci.39.4.820e ◽

2004 ◽

Vol 39 (4) ◽

pp. 820E-821

Author(s):

Fahrettin Goktepe ◽

Harrison Hughes*

Keyword(s):

Transgenic Plants ◽

Infected Leaf ◽

Wild Type ◽

Didymella Bryoniae ◽

Isopentenyl Transferase ◽

Disease Symptoms ◽

Stem Blight ◽

Transformed Plants ◽

Gummy Stem Blight ◽

Run Off

Watermelon plants are susceptible to Gummy stem blight disease that considerably reduces yields worldwide. In order to develop non-specific resistance, watermelon cv. Crimson Sweet was transformed with copper inducible isopentenyl transferase (ipt), the rate-limiting step in cytokinin biosynthesis, gene via Agrobacterium tumafaciences (LBA4404). Transformed (ipt) and nontransformed plants were grown at approximately 28-30 °C day, 20-22 °C night and 16 hours daylight under greenhouse conditions. Once the plants initiated new growth both transgenic plants and wild type plants were sprayed with one of three different concentrations (0, 10 & 50 μm) of CuSO4. Plants were sprayed twice to run-off in a twenty-four hour time period before inoculation with the pathogen. Cultures of the pathogen Didymela bryonia (W353) were grown for about 3 weeks and an inoculum containing 105 conidia per mL was sprayed with the prepared suspension until initial run-off in a humidified chamber. The disease symptoms were evaluated after one week with resistance demonstrated in all treated transgenic plants. All nonsprayed transgenic and wild type plants showed similar disease symptoms. Infected leaf samples were surface sterilized and re-cultured on V8 medium. The characteristics of the recovered pathogen confirmed that it was identical to the stock culture of W353. The same experiment has been conducted on seedlings from transgenic (T1 generations) and non-transformed plants. The non-transformed seedlings showed the first disease symptoms on their cotyledons and lower leaves. Disease resistance was observed in seedlings of the treated transformed plants as compared to nontransformed ones.

Download Full-text

Screening Melon (Cucumis melo) for Resistance to Gummy Stem Blight in the Greenhouse and Field

HortScience ◽

10.21273/hortsci.32.1.117 ◽

1997 ◽

Vol 32 (1) ◽

pp. 117-121 ◽

Cited By ~ 14

Author(s):

Yiping Zhang ◽

Molly Kyle ◽

Konstantinos Anagnostou ◽

Thomas A. Zitter

Keyword(s):

Cucumis Melo ◽

Field Tests ◽

Plant Introduction ◽

Didymella Bryoniae ◽

Stem Blight ◽

Gummy Stem Blight ◽

High Level ◽

Different Origins ◽

Chinese Group ◽

Onondaga County

Greenhouse and field evaluations of melon (Cucumis melo L.) for resistance to gummy stem blight, caused by the fungus Didymella bryoniae (Auersw.) Rehm, were conducted on 798 U.S. Dept. of Agriculture Plant Introduction (PI) accessions and 24 related Cucumis species. Plants were inoculated at the three to four true-leaf stage with a virulent isolate of D. bryoniae collected from Onondaga County, N.Y., and disease indices were calculated based on foliar and stem symptoms. In greenhouse screens, 43 C. melo accessions showed a high level of resistance. Results were consistent between the optimized greenhouse screening procedure described and inoculated replicated field tests. Of these accessions, a Chinese group, PIs 157076, 157080, 157081, 157082, 157084; another group from Zimbabwe, PIs 482393, 482398, 482399, 482402, 482403, 482408; and some others from different origins, PI 255478 (Korea) and PI 511890 (Mexico), showed high levels of resistance, at least equal to that in PI 140471, the leading source of resistance to date.

Download Full-text