scholarly journals Field Response of Cucurbit Hosts to Pseudoperonospora cubensis in Michigan

Plant Disease ◽  
2015 ◽  
Vol 99 (5) ◽  
pp. 676-682 ◽  
Author(s):  
M. C. Cespedes-Sanchez ◽  
R. P. Naegele ◽  
C. S. Kousik ◽  
M. K. Hausbeck
Keyword(s):  
Downy Mildew ◽  
Cucumis Melo ◽  
Disease Onset ◽  
Research Field ◽  
Pseudoperonospora Cubensis ◽  
Plant Introductions ◽  
Disease Progress ◽  
Pickling Cucumber ◽  
Progress Curve ◽  
Significant Disease

Downy mildew, caused by Pseudoperonospora cubensis, is a severe foliar disease of many cucurbit crops worldwide. Forty-one cucurbit cultigens (commercial cultivars and plant introductions) from five genera (Cucumis, Citrullus, Cucurbita, Lagenaria, and Luffa) were assessed for susceptibility to P. cubensis in a research field exposed to natural inoculum in Michigan. Eight cultigens from a differential set for pathotype determination were included within the 41 cultigens to detect changes in dominant P. cubensis pathotypes present. No pathotype differences were found between 2010 and 2011. Cucumis melo cultigen MR-1 was less susceptible to Michigan P. cubensis populations than other C. melo cultigens. No symptoms or signs of infection were detected on cultigens of Cucurbita moschata and C. pepo. Disease onset was later in 2011 than 2010; greater than 90% disease severity in pickling cucumber ‘Vlaspik’ was observed in both years. This study confirmed that Cucumis is the most susceptible cucurbit genus, while Citrullus and Cucurbita cultigens were the least susceptible genera to populations of P. cubensis in Michigan. Area under the disease progress curve values indicated that disease progress was limited on all Citrullus cultigens compared with Cucumis cultigens, and pathogen sporulation was not detected under field conditions. Future studies should evaluate the ability of a reduced fungicide program to control downy mildew on less susceptible Cucumis melo ‘Edisto 47’, ‘Primo’, ‘Athena’, ‘Strike’, ‘Ananas’, ‘Banana’, and ‘Tam-Dew’. Many of the melon cultivars evaluated were selected on the basis of reported resistance to downy mildew, yet they showed significant disease symptoms. It is important to evaluate candidate cultigens for resistance to local P. cubensis populations.

scholarly journals Fungicides for Control of Downy Mildew on Pickling Cucumber in Michigan

2019 ◽  
Vol 20 (3) ◽  
pp. 165-169 ◽  
Author(s):  
Katelyn E. Goldenhar ◽  
Mary K. Hausbeck
Keyword(s):  
Downy Mildew ◽  
Untreated Control ◽  
Field Studies ◽  
Pseudoperonospora Cubensis ◽  
Relative Area ◽  
Disease Progress Curve ◽  
Cucurbit Downy Mildew ◽  
Disease Progress ◽  
Pickling Cucumber ◽  
Progress Curve

Michigan growers rely on fungicides to limit cucurbit downy mildew (CDM), incited by Pseudoperonospora cubensis; resistance of the pathogen to fungicides is a concern. We evaluated fungicides against CDM in Michigan field studies from 2015 to 2017. According to the relative area under the disease progress curve (rAUDPC), in 2015, mandipropamid, propamocarb, fluxapyroxad/pyraclostrobin, copper octanoate, and dimethomorph resulted in disease levels similar to the control. These treatments, along with cymoxanil, were similar to the control in 2016. Fungicides that were ineffective during 2015 and 2016 did not limit CDM in 2017. Famoxadone/cymoxanil and fluopicolide did not limit CDM in 2017. Each year, the following treatments were similar for disease based on rAUDPC data: oxathiapiprolin applied alone or premixed with chlorothalonil or mandipropamid, ametoctradin/dimethomorph, fluazinam, mancozeb/zoxamide, cyazofamid, and ethaboxam. An exception occurred in 2017, when ethaboxam was less effective than fluazinam, oxathiapiprolin/chlorothalonil, and oxathiapiprolin/mandipropamid. Mancozeb and chlorothalonil treatments were similar in 2015 and 2017, according to rAUDPC data. In 2017, yields were increased for oxathiapiprolin/chlorothalonil, oxathiapiprolin/mandipropamid, mancozeb, ametoctradin/dimethomorph, mancozeb/zoxamide, ethaboxam, cyazofamid, chlorothalonil, and fluazinam compared with the untreated control.

scholarly journals Evaluation of Melon Germplasm for Resistance to Downy Mildew

HortScience ◽  
1992 ◽  
Vol 27 (5) ◽  
pp. 434-436 ◽  
Author(s):  
Claude E. Thomas ◽  
E.L. Jourdain
Keyword(s):  
Downy Mildew ◽  
Cucumis Melo ◽  
Disease Index ◽  
Pseudoperonospora Cubensis ◽  
Reaction Type ◽  
Plant Introductions ◽  
Resistant Reaction ◽  
Moderately Resistant

Field evaluations for resistance against downy mildew, incited by Pseudoperonospora cubensis [(Berk. and Cart.) Rostow], were conducted on 942 U.S. Plant Introductions (PI) of Cucumis melo L. (melon). A disease index (DI) was calculated for each entry. Based on DI, PI 124112 was highly resistant (DI = 3.7), and PIs 124111, 122847, 124210, 145594, and 165525 were resistant (DI = 3.0, 2.8, 2.6, 2.7, and 2.5, respectively). PIs 124111 and 124112 had one or more plants that exhibited a highly resistant reaction type (RT 4). Resistant (RT 3) plants were identified in 31 accessions, and 49 accessions bad moderately resistant (RT 2) plants.

scholarly journals Isolate-Dependent Inheritance of Resistance Against Pseudoperonospora cubensis in Cucumber

Agronomy ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 1086 ◽  
Author(s):  
Tomer Chen ◽  
Daniel Katz ◽  
Yariv Ben Naim ◽  
Rivka Hammer ◽  
Bat Hen Ben Daniel ◽  
...  
Keyword(s):  
Segregation Ratio ◽  
Lesion Size ◽  
Pseudoperonospora Cubensis ◽  
Plant Introductions ◽  
Growing Seasons ◽  
Multiple Phenotypes ◽  
Progress Curve ◽  
Growth Chambers ◽  
Wild Accessions ◽  
Moderately Resistant

Six wild accessions of Cucumis sativum were evaluated for resistance against each of the 23 isolates of the downy mildew oomycete Pseudoperonospora cubensis. The isolates originated from Israel, Europe, USA, and Asia. C. sativum PI 197088 (India) and PI 330628 (Pakistan) exhibited the highest level of resistance against multiple isolates of P. cubensis. Resistance was manifested as reduced lesion number, lesion size, sporangiophores and sporangia per lesion and enhanced encasement of haustoria with callose and intensive accumulation of lignin in lesions of both Plant Introductions (PIs) compared to the susceptible C. sativum SMR-18. In the field, much smaller AUDPC (Area Under Disease Progress Curve) values were recorded in PI 197088 or PI 330628 as compared to SMR-18. Each PI was crossed with SMR-18 and offspring progeny plants were exposed to inoculation with each of several isolates of P. cubensis in growth chambers and the field during six growing seasons. F1 plants showed partial resistance. F2 plants showed multiple phenotypes ranging from highly susceptible (S) to highly resistant (R, no symptoms) including moderately resistant (MR) phenotypes. The segregation ratio between phenotypes in growth chambers ranged from 3:1 to 1:15, depending on the isolate used for inoculation, suggesting that the number of genes, dominant, partially dominant, or recessive are responsible for resistance. In the field, the segregation ratio of 1:15, 1:14:1, or 1:9:6 was observed. F2 progeny plants of the cross between the two resistant PI’s were resistant, except for a few plants that were partially susceptible, suggesting that some of the resistance genes in PI 197088 and PI 330328 are not allelic.

scholarly journals Reaction of Selected Soybean Genotypes to Isolates of Fusarium solani f. sp. glycines and Their Culture Filtrates

Plant Disease ◽  
1998 ◽  
Vol 82 (9) ◽  
pp. 999-1002 ◽  
Author(s):  
Y. H. Huang ◽  
G. L. Hartman
Keyword(s):  
Great Lakes ◽  
Disease Severity ◽  
Culture Filtrate ◽  
Fusarium Solani ◽  
Stem Length ◽  
Soybean Plant ◽  
Foliar Disease ◽  
Plant Introductions ◽  
Disease Progress ◽  
Progress Curve

Four soybean plant introductions, PI 520.733, PI 567.374, PI 567.650B, and PI 567.659, and one soybean cultivar, Great Lakes 3202, were inoculated under greenhouse conditions with four isolates of Fusarium solani f. sp. glycines. Foliar disease severity rating was greatest on PI 567.659, followed by Great Lakes 3202, PI 520.733, PI 567.650B, and PI 567.374. There was no significant interaction between isolates and soybean entries for foliar disease severity ratings. Experiments also were conducted to determine if disease development and root colonization differed among entries. Root infection of the five entries did not differ (P = 0.05). Foliar disease progress curves increased faster for PI 567.659 and Great Lakes 3202 than for PI 567.374. The area under the disease progress curve (AUDPC) value for PI 567.374 was the lowest and differed (P = 0.01) from AUDPC values for Great Lakes 3202 and PI 567.659. There were no differences (P = 0.01) in length of taproot lesions, losses in root dry weight, and vascular stem length discoloration among the entries, and there was no correlation (P = 0.05) between these measurements and foliar AUDPC values. Cut seedling stems immersed in culture filtrate developed interveinal chlorosis on leaves of each entry within 2 days. Disease severity on cut seedlings of PI 567.374 was lower (P = 0.01) than on the other entries. There was a positive correlation (r = 0.94, P = 0.05) between AUDPC values of the five entries inoculated with the fungus and the cut seedling test using culture filtrate.

scholarly journals FIELD INOCULATION TESTS TO QUANTIFY RESISTANCE IN SPINACH TO RACES 3 AND 4 OF DOWNY MILDEW

HortScience ◽  
1992 ◽  
Vol 27 (6) ◽  
pp. 598b-598
Author(s):  
L.P. Brandenberger ◽  
J.C. Correll ◽  
T.E. Morelock ◽  
R.W. McNew
Keyword(s):  
Downy Mildew ◽  
Disease Severity ◽  
Leaf Surface ◽  
Field Inoculation ◽  
Disease Progress Curve ◽  
Disease Progress ◽  
Progress Curve

Resistance to race 3 and 4 of downy mildew (Peronospora farinosa f.sp. spinaciae) was examined in separate field inoculation tests. Three Arkansas cultivars and three other commercial spinach cultivars were compared by periodically scoring individual leaves for disease severity 7 to 28 days after inoculation. Leaves were scored on a 0 to 6 scale with 0 = 0% of the leaf surface being covered with sporulation and 6 = 90-100%. Resistance was evaluated by comparing disease ratings on a given day as well as the area under the disease progress curve. Arkansas spinach cultivars exhibited significantly lower disease severity ratings in field inoculation tests for all sample dates for both races 3 and 4 when compared to known susceptible cultivars.

scholarly journals Additional Evaluations of Cucumis melo L. Germplasm for Resistance to Downy Mildew

HortScience ◽  
1999 ◽  
Vol 34 (5) ◽  
pp. 920-921 ◽  
Author(s):  
C.E. Thomas
Keyword(s):  
Downy Mildew ◽  
Cucumis Melo ◽  
Disease Index ◽  
Reaction Type ◽  
Plant Introductions ◽  
Moderately Resistant ◽  
Cucumis Melo L

Field evaluations for resistance against downy mildew, incited by Pseudoperonospora cubensis (Berk. & M.A. Curtis) Rostovzev were conducted on 1076 U.S. Plant Introductions (PI) of Cucumis melo L. (melon). A disease index (DI) was calculated for each entry that had one or more resistant plants. Based on DI, PIs 271329 and 401644 were the most resistant overall (DI = 2.6 and 2.8, respectively). However, resistant plants exhibiting reaction type (RT) 3 were identified in 68 accessions, and 110 accessions had moderately resistant (RT 2) plants.

scholarly journals Bioactive compound profile of melon leaf extract (Cucumis melo L. ‘Hikapel’) infected by downy mildew

2019 ◽  
Vol 20 (11) ◽  
Author(s):  
Ozie Akbar Pratama ◽  
WORO ANINDITO SRI TUNJUNG ◽  
SUTIKNO SUTIKNO ◽  
BUDI SETIADI DARYONO
Keyword(s):  
Downy Mildew ◽  
Cucumis Melo ◽  
Leaf Extract ◽  
Methyl Ricinoleate ◽  
Insulin Level ◽  
Bioactive Compound ◽  
Pseudoperonospora Cubensis ◽  
Leaf Powder ◽  
Bioactive Content ◽  
Cucumis Melo L

Abstract. Pratama OA, Tunjung WAS, Sutikno, Daryono BS. 2019. Bioactive compound profile of melon leaf extract (Cucumis melo L. ‘Hikapel’) infected by downy mildew. Biodiversitas 20: 3448-3453. Plants express specific secondary metabolites (phytoalexin) in response to infection. Downy Mildew which infects melon plants (Cucumis melo L. ‘Hikapel’) caused by Pseudoperonospora cubensis Rostovtsev. Hikapel is one of superior melon cultivar produced from research in the Laboratory of Genetics, Faculty of Biology, Universitas Gadjah Mada, Yogyakarta, Indonesia. Bioactive content of Hikapel melon leaf under normal condition and infected by Downy Mildew yet to be researched. This research aims to screen bioactive profile of Hikapel leaf extract that has potential as phytomedicine. Leaf extract is compared between healthy plants and infected by Downy Mildew. Dried melon leaf was powdered using mortar and pestle. Leaf powder was extracted using hexane solvent. Extract was analyzed using a Shimadzu GCMS-QP2010S. Analysis found useful compounds like phytol, methyl ricinoleate, methyl linoleate, methyl stearate, and 1-hexacosanol. with therapeutic activity such as antibacterial, antifungal, antioxidant, antiinflammatory, antidiuretic, antidiarrheal, lowering blood LDL-C level, insulin level booster, antiproliferative, and anticancer. Some bioactive compounds are only synthesized in Hikapel melon leaf under stress conditions.

scholarly journals Development of an ecological strategy for the control of downy mildew (Pseudoperonospora cubensis) in cucumber cultivation (Cucumis sativus L.)

Bionatura ◽  
2015 ◽  
Vol 5 (2) ◽  
pp. 1101-1105
Author(s):  
Julio Gabriel-Ortega ◽  
Edwin Pereira-Murillo ◽  
Fernando Ayón-Villao ◽  
Carlos Castro-Piguave ◽  
Isaías Delvalle-García ◽  
...  
Keyword(s):  
Downy Mildew ◽  
Severe Disease ◽  
Significant Loss ◽  
Pseudoperonospora Cubensis ◽  
Systemic Fungicide ◽  
Ecological Strategy ◽  
Cucumis Sativus L ◽  
Profitability Analysis ◽  
Progress Curve ◽  
Trichoderma Sp

Downy mildew is a severe disease of cucumber worldwide. The oomycete Pseudoperonospora cubensis cause it and once it is established in a region, the infection spreads rapidly, causing significant loss of yield and fruit quality. The objective of the research was to develop an ecological strategy for the control of downy mildew in cucumber. The treatments were arranged in a completely randomized experimental design with an alternation of chemical and biological fungicides. The treatments were: T1: systemic fungicide (Ridomil Gold, 2.5 g/l) alternating with a contact fungicide (Bravo 2.5 ml/l), T2: CustomBio 5 (Bacillus-based fungicide, 3ml/l), T3: control (water), T4: Trichoderma sp. (3 ml/l), T5: systemic fungicide (Ridomil Gold 2.5g/l) alternating with CustomBio 5 (3 ml/l), and T6: systemic fungicide (Ridomil Gold 2.5g/l) alternating with Trichoderma sp. (3 ml/l). The following variables were evaluated: stem thickness, plant height, number and weight of fruits, yield, the area under the relative progress curve (AUDPCr), and economic analysis of each treatment. The results showed that the best treatments were T1 and T6, with an AUDPCr of 11.89% and 12.10%, respectively. Treatments T6 and T1 showed the best yield, as well. The profitability analysis showed that all the alternatives were profitable with a Benefit/Cost>1 ratio. However, the treatments T6 and T1 were the most useful. We recommend this control strategy to reduce the use of chemical fungicides and, at the same time, obtain an efficient control of the disease, which guarantees a significant yield of high-quality fruit.

scholarly journals Formation and Infectivity of Oospores of Pseudoperonospora cubensis, the Causal Agent of Downy Mildew in Cucurbits

Plant Disease ◽  
2011 ◽  
Vol 95 (7) ◽  
pp. 874-874 ◽  
Author(s):  
Y. Cohen ◽  
A. E. Rubin ◽  
M. Galperin
Keyword(s):  
United States ◽  
Downy Mildew ◽  
Cucumis Melo ◽  
The United States ◽  
Pseudoperonospora Cubensis ◽  
Prolonged Incubation ◽  
Field Isolates ◽  
F1 Progeny ◽  
Detached Leaves ◽  
Growth Chambers

The oomycete Pseudoperonospora cubensis attacks members of the Cucurbitaceae, causing severe foliage damage especially to cucumber and melon. Recently, new pathotypes of this oomycete appeared in Israel (2) and Italy (1) and highly aggressive isolates appeared in the United States (3). Since oospores of P. cubensis were rarely seen and sexual propagation by oospores was never reported (4), it is assumed that it propagates clonally by sporangia. Here we report on sexual reproduction of P. cubensis under controlled conditions in the laboratory. We found that field isolates belonging to the old pathotype 3 or to the new pathotype 6 (2) inoculated singly onto detached leaves of cucurbits in growth chambers at 15 or 20°C produced no oospores, even after prolonged incubation periods. However, when sporangia of some paired field isolates were mixed together at a 1:1 ratio, similarly inoculated onto detached leaves, and incubated at 15 or 20°C, numerous oospores (up to ~300/cm2) were formed in the mesophyll within 6 to 11 days, depending on the isolates pair, the host inoculated, and temperature. Oospores were also formed at 12.5°C but not at 25°C. Oospores developed in intact plants when kept at 15 or 20°C under a humidity-saturated atmosphere during disease development. Oospores were round, light brown to brown with an average diameter of ~40 μm. Oospores were produced in Cucumis sativum (cvs. Nadiojni and Dalila) and Cucumis melo (cvs. Ananas-Yokneam and Ein-Dor) but not in Cucurbita pepo (cv. Arlika, Beiruti), C. moschata (cv. Dalorit), or C. maxima (cv. Tripoli). To verify that oospores are infective, cucumber or melon leaves containing oospores were homogenized in water. The homogenate was twice brought to dryness at 25 to 30°C in petri dishes to differentially kill the vegetative structures of the pathogen (sporangia, cystospores, zoospores, and mycelia), resuspended in water, and inoculated onto detached leaves of various cucurbits in growth chambers at 15 or 20°C. Downy mildew lesions carrying sporangia appeared within 7 to 20 days in leaves of Cucumis sativum, Cucumis melo, and C. moschata but not in C. pepo or C. maxima. The recombinant origin of the F1 offspring isolates was confirmed by mefenoxam sensitivity tests, random amplified polymorphic DNA, and simple sequence repeat analyses. F1 progeny isolates of some crosses lost pathogenicity to C. moschata or C. maxima, toward which one of their parents was pathogenic, while others gained pathogenicity to Luffa cylindrica or Citrullus lanatus toward which neither parent was pathogenic. Data confirmed that isolates of P. cubensis can mate to produce oospores, especially under constant humidity conditions; such oospores are infective to cucurbits and F1 progeny isolates show altered sensitivity to fungicides or altered host range relative to their parents. To our knowledge, this is the first report of oospore formation by P. cubensis in the laboratory and on their pathogenicity to cucurbits. Reasons for the parallel appearance of new pathotypes of P. cubensis in Israel in 2002 (2) and Italy in 2003 (1) and the reemergence of highly aggressive isolates of the pathogen in the United States in 2004 (3) are not known. They may be related to oospore production and sexual recombination in P. cubensis. References: (1) C. Cappelli et al. Plant Dis. 87:449, 2003. (2) Y. Cohen et al. Phytoparasitica 31:458, 2003. (3) G. J. Holmes et al. Am. Veg. Grower. February, 14-15, 2006. (4) A. Lebeda and Y. Cohen. Eur. J. Plant Pathol.129:157, 2011.

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