Genotyping-by-Sequencing for Analysis of the Genetic Variation of Podosphaera xanthii, Incitant of Cucurbit Powdery Mildew

This research was conducted to identify species causing powdery mildew on cucurbits and to determine genetic variations among isolates of the pathogen. We collected 109 isolates from six cucurbit species hosts (Cucumis melo, Cucumis sativus, Cucurbita maxima, Cucurbita moschata, Cucurbita pepo, and Lagenaria siceraria) in California, Illinois, Indiana, Michigan, New York, Texas, Washington, and Wisconsin in the United States and in Italy. By sequencing the internal transcribed spacer region of the nuclear rDNA of these 109 isolates, Podosphaera xanthii was found as the only species causing powdery mildew on cucurbits in the United States. Genotyping-by-sequencing was applied to these 109 isolates to investigate their genetic diversity, which showed a trend of isolates clustering from New York and Italy. In addition, the virulence of 36 isolates was compared and a significant difference (P < 0.0001) was found among them. Furthermore, results of the virulence tests of 28 isolates from Illinois showed significant effects of collection years, hosts, and locations on the virulence of the isolates.

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First Detection of Boscalid Resistance in Podosphaera xanthii in the United States Associated With Failure to Control Cucurbit Powdery Mildew in New York and New Jersey in 2009

Plant Health Progress ◽

10.1094/php-03-17-0014-br ◽

2017 ◽

Vol 18 (2) ◽

pp. 93-93 ◽

Cited By ~ 2

Author(s):

M. T. McGrath ◽

C. A. Wyenandt

Keyword(s):

United States ◽

New York ◽

Powdery Mildew ◽

Resistance Management ◽

The United States ◽

Management Tool ◽

Podosphaera Xanthii ◽

Resistance Risk ◽

Causal Pathogen ◽

Succinate Dehydrogenase Inhibitor

The most effective management tool for powdery mildew on cucurbit crops is mobile, targeted fungicides having a moderate or high resistance risk and the causal pathogen has proven to be a high-risk organism. Information about occurrence of resistance to a new chemical group and impact on resistance management is important for guiding fungicide programs and contributing to scientific knowledge about resistance development. This brief reports the first known occurrence of resistance to a succinate dehydrogenase inhibitor fungicide in Podosphaera xanthii in the United States.

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First Report of the Cucurbit Powdery Mildew Fungus (Podosphaera xanthii) Resistant to Strobilurin Fungicides in the United States

Plant Disease ◽

10.1094/pdis.2003.87.8.1007a ◽

2003 ◽

Vol 87 (8) ◽

pp. 1007-1007 ◽

Cited By ~ 18

Author(s):

M. T. McGrath ◽

N. Shishkoff

Keyword(s):

United States ◽

New York ◽

Powdery Mildew ◽

The United States ◽

Podosphaera Xanthii ◽

Commercial Use ◽

Strobilurin Fungicides ◽

Research Fields ◽

Cucurbit Powdery Mildew ◽

Dmi Resistance

Resistance to strobilurin fungicides was documented in isolates collected from three fungicide efficacy experiments conducted in research fields in Georgia (GA), North Carolina (NC), and New York (NY). In these fields in 2002, strobilurins (fungicide group 11, quinone outside inhibitors [QoI]) when used alone on a 7-day schedule (use pattern not labeled) did not effectively control cucurbit powdery mildew. Strobilurin efficacy declined dramatically after the second application in New York (3). Efficacy also was reduced in commercial fields in Kentucky and research fields in Arizona, California, Kentucky, Illinois, Michigan, and Virginia in 2002 where strobilurins were used predominantly or exclusively. Isolates were collected on 22 July and 8 and 17 October after the last of four, five, and five applications of strobilurin (trifloxystrobin formulated as Flint or azoxystrobin formulated as Quadris) in experiments conducted by J. D. Moore in Chula, GA, M. McGrath in Riverhead, NY, and G. J. Holmes in Clayton, NC, respectively. A leaf-disk bioassay was used to determine fungicide sensitivity (2). Strobilurin sensitivity was determined using trifloxystrobin at 0, 0.5, 5, 50, and 100 μg/ml. Four of nine NY isolates, 19 of 21 GA isolates, and 13 of 15 NC isolates were resistant to strobilurins (grew well on disks treated with trifloxystrobin at 100 μg/ml). The geometric mean of the azoxystrobin baseline was 0.258 μg/ml for Podosphaera xanthii isolates collected in 1998 and 1999 in North America (4). Poor control with strobilurins under field conditions was associated with reduced sensitivity in vitro. Strobilurin sensitivity appeared to be qualitative as reported elsewhere (1). Two sensitive and three resistant isolates responded similarly when tested in another laboratory using kresoxim-methyl and pyraclostrobin (H. Ypema, personal communication). These findings and experiences elsewhere with QoI-resistant P. xanthii indicate that cross-resistance probably extends among multiple QoI's (1). Strobilurins have been available for commercial use in the United States since 1998, when azoxystrobin received Section 18 registration in some states. Federal registration was granted in March 1999. Strobilurin resistance was detected after 2 years of commercial use elsewhere in the world (1). All isolates tested in the current study were from research fields where selection pressure for resistance could have been higher than in commercial fields where strobilurins are used with demethylation inhibitors (DMIs; fungicide group 3) and contact fungicides in alternation or tank mixtures to prevent or delay resistance development. Resistance in commercial fields will reduce the utility of strobilurins, including those not yet registered, and eliminate an important tool for managing DMI resistance. Strobilurins and DMIs are the only systemic fungicides registered for cucurbit powdery mildew in the United States. Managing DMI resistance may be challenged by multiresistant strains. Strobilurin-resistant isolates also exhibited reduced sensitivity to DMIs, tolerating triadimefon at 50 to 100 μg/ml (2). One suggestion to improve resistance management is to apply a contact fungicide with strobilurins as well as DMIs. References: (1) H. Ishii et al. Phytopathology 91:1166, 2001. (2) M. T. McGrath et al. Plant Dis. 80:697, 1996. (3) M. T. McGrath and N. Shishkoff. Fungic. Nematic. Tests. (In press). (4) G. Olaya et al. Phytopathology (Abstr.) 90 (suppl):S57, 2000.

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Sawadaea tulasnei Powdery Mildew of Norway Maple (Acer platanoides) in North America

Plant Disease ◽

10.1094/pd-90-0830c ◽

2006 ◽

Vol 90 (6) ◽

pp. 830-830

Author(s):

J. Weiland ◽

G. Stanosz

Keyword(s):

United States ◽

New York ◽

North America ◽

Powdery Mildew ◽

Acer Saccharum ◽

The United States ◽

Rdna Its ◽

Maple Leaves ◽

Norway Maple ◽

Genus 2

Norway maple leaves bearing powdery mildew were collected from one location in the fall of 2003 and four locations (as much as 1.5 km apart) in the fall of 2005 in Buffalo, NY. No powdery mildew was observed on leaves collected from sugar maples (Acer saccharum) that were present in the vicinity of affected Norway maples at two locations. Trees were located along streets and in yards. Diseased leaves were present throughout tree crowns but lower leaves were more commonly affected. White mycelium was present in irregular, discrete, scattered spots only on the upper surface of leaves and on both sides of wings of samaras. Typically, <10% of the upper leaf area bore visible mycelium. Cleistothecia were present singly or in groups on the mycelium. Morphology of cleistothecia on leaves collected each year, including simple and bifid appendages with uncinate to circinate apices, was sufficient to identify the pathogen to the genus Sawadaea (1). Other characteristics were not sufficiently distinct to make an identification of S. bicornis or S. tulasnei (1), each a European species found on Acer spp. However, a sample from 2003 was supplied by the authors for use in a study of phylogeny of the genus (2) that served as a first report of the species in the United States. Analysis of nuclear rDNA ITS sequence of this specimen (GenBank Accession No. AB193390) placed the sample in a clade with S. tulasnei specimens from Europe. In the same study, powdery mildew samples from Acer spp. in Ohio and Montreal, Canada also were placed in this clade. Thus, occurrence of S. tulasnei in North America is confirmed. S. bicornis was recently identified (based on morphology) on Norway maple in the western United States (3). Specimens from Buffalo, NY have been deposited in the U.S. National Fungus Collections (BPI 871210). References: (1) U. Braun. The Powdery Mildews (Erysiphales) of Europe. Gustav Fischer Verlag, Jena-Stuttgart-New York, 1995. (2) S. Hirose et al. Mycol. Res. 109:912, 2005. (3) C. Nischwitz and G. Newcombe. Plant Dis. 87:451, 2003.

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First Report of Powdery Mildew Caused by Podosphaera (Sphaerotheca) fusca on Euryops pectinatus in North America

Plant Disease ◽

10.1094/pdis.2000.84.9.1048a ◽

2000 ◽

Vol 84 (9) ◽

pp. 1048-1048 ◽

Cited By ~ 1

Author(s):

G. S. Saenz ◽

S. T. Koike ◽

N. Shishkoff

Keyword(s):

United States ◽

New York ◽

North America ◽

Powdery Mildew ◽

Fungal Growth ◽

The United States ◽

Voucher Specimen ◽

First Report ◽

Humidity Chamber ◽

Powdery Mildew Pathogen

Gray-leaved Euryops (Euryops pectinatus Cass., Asteraceae) is an evergreen shrub that is widely planted in landscapes in the United States. In the fall of 1999, powdery mildew was observed on E. pectinatus planted in landscapes in Redlands (San Bernardino County), CA. Symptoms consisted only of slight cupping of leaves. Fungal growth was observed on stems, leaves, petioles, and pedicels and was ectophytic and amphigenous. The white mycelium was patchy to effuse. Hyphal appressoria were indistinct (1). Conidiophore foot cells were cylindric and sometimes were tapered toward or constricted at the base. Foot cells measured 30 to 50 by 10 to 12 μm and were followed by one to two shorter cells. Conidia were cylindric to slightly doliform, borne in chains of two to three, and measured 26 to 38 by 14 to 18 μm. Conidial length to width ratios ranged from 1.7 to 2.4. Catenate conidia had crenate edge lines (3). Conidia possessed conspicuous fibrosin bodies and from their sides produced short germ tubes without appressoria. Cleistothecia were not observed. Based on these characters, the fungus was identified as Podosphaera fusca (Fr.) U. Braun & N. Shishkoff (Podosphaera sect. Sphaerotheca) (1,2). Pathogenicity was confirmed by gently pressing diseased leaves onto leaves of healthy E. pectinatus plants. Plants were incubated in a humidity chamber at 22 to 24°C and after 12 to 14 days powdery mildew colonies developed. E. pectinatus cv. Viridis, a cultivar that lacks the extensive pubescence of E. pectinatus, also developed disease when inoculated. This appears to be the first report of powdery mildew on E. pectinatus in North America. A voucher specimen has been deposited into the University of California Herbarium (accession # UC1738635). P. fusca was also observed on cv. Viridis in a nursery in New York in 1999. It is unclear where this pathogen originated. P. fusca parasitizes a large number of asteraceous species including dandelion (Taraxacum officinalis) and sowthistle (Sonchus spp.) weeds, which occur in the area and sometimes are infected with powdery mildew. The Euryops powdery mildew pathogen may be a race that is different than those found on other composites in the United States. The fungus was observed on plants in shaded areas but not on plants in full sun. References: (1) U. Braun. Nova Hedwigia 89:1, 1987. (2) U. Braun and S. Takamatsu. Schlechtendalia 4:1, 2000. (3) H. D. Shin and Y. J. La. Mycotaxon 46:445, 1993.

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Poor Control of Cucurbit Powdery Mildew Associated with First Detection of Resistance to Cyflufenamid in the Causal Agent, Podosphaera xanthii, in the United States

Plant Health Progress ◽

10.1094/php-06-18-0029-br ◽

2018 ◽

Vol 19 (3) ◽

pp. 222-223 ◽

Cited By ~ 1

Author(s):

Margaret T. McGrath ◽

Zachary F. Sexton

Keyword(s):

United States ◽

Powdery Mildew ◽

High Resistance ◽

The United States ◽

Management Tool ◽

Common Disease ◽

Podosphaera Xanthii ◽

Resistance Risk ◽

Action Committee ◽

Group Knowledge

This report is about the first known occurrence of resistance to cyflufenamid, a Fungicide Resistance Action Committee (FRAC) code U6 fungicide, in Podosphaera xanthii in the United States. This fungus causes powdery mildew in cucurbit crops, the most common disease of this important crop group. Knowledge about resistance is important for guiding fungicide programs. Mobile, targeted fungicides, which have moderate or high resistance risk, are the most effective management tool for this disease. The pathogen is a documented high resistance risk organism having already developed resistance to fungicides in FRAC groups 1, 3, 7, 11, and 13.

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First Report of Resistance to Quinoxyfen in Podosphaera xanthii, Causal Agent of Cucurbit Powdery Mildew, in the United States

Plant Health Progress ◽

10.1094/php-03-17-0018-br ◽

2017 ◽

Vol 18 (2) ◽

pp. 94-94 ◽

Cited By ~ 3

Author(s):

M. T. McGrath

Keyword(s):

United States ◽

Powdery Mildew ◽

High Resistance ◽

The United States ◽

Management Tool ◽

Common Disease ◽

Podosphaera Xanthii ◽

Effective Management ◽

Group 13 ◽

Resistance Risk

This brief reports the first known occurrence of resistance to quinoxyfen, a quinoline (FRAC Group 13) fungicide, in Podosphaera xanthii in the United States. This fungus causes powdery mildew in cucurbit crops, the most common disease of this important crop group. Mobile, targeted fungicides, which have moderate or high resistance risk, are the most effective management tool for this disease. The pathogen is a documented high resistance-risk organism, having already developed resistance to fungicides in FRAC Groups 1, 3, 7, and 11.

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OIL SPILL RATES IN FOUR U.S. COASTAL REGIONS*

International Oil Spill Conference Proceedings ◽

10.7901/2169-3358-1981-1-677 ◽

1981 ◽

Vol 1981 (1) ◽

pp. 677-683 ◽

Cited By ~ 2

Author(s):

Mary Ann Froehlich ◽

John F. Bellantoni

Keyword(s):

United States ◽

New York ◽

New Jersey ◽

Oil Spill ◽

Oil Spills ◽

Weather Conditions ◽

Hudson River ◽

The United States ◽

Army Corps ◽

Significant Difference

ABSTRACT The incidence of oil spills of more than 10,000 gallons in the years 1974 through 1977 was compared for four regions in the United States that carry heavy oil traffic: Greater New York-New Jersey, Delaware Bay, the Louisiana coast, and the northern Texas coast. The purpose was to determine whether there was any significant difference in oil spill rates among the four regions. The spill data from the study were drawn from the Pollution Incident Reporting System (PIRS), the records of the National Response Center (NRC), and the Commercial Vessel Casualty File. Oil movement data were obtained from the U.S. Army Corps of Engineers, Waterborne Commerce of the United States. A comparison of PIRS and NRC data indicated that neither data source was complete. From the amount of agreement between the two sources and some statistical assumptions, it was estimated that the PIRS data covered about 75 percent of all spills and about 88 percent of all vessel-related spills. The spill rates calculated for the four regions showed no significant differences. However, a significantly higher spill rate was noted for the Hudson River subdivision of the New York-New Jersey region. An examination of the spill reports showed that most of the spills were associated with poor weather conditions, that is, ice or fog.

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Epidemiological Analysis of Avulsion Fractures in Dogs

VCOT Open ◽

10.1055/s-0040-1713123 ◽

2020 ◽

Vol 03 (02) ◽

pp. e60-e65

Author(s):

Alyssa M. Matos Cruz ◽

Mitsunori Kayano ◽

Mizuki Tomihari ◽

Po-Yen Chou ◽

Sun Young Kim ◽

...

Keyword(s):

United States ◽

New York ◽

Epidemiological Data ◽

The United States ◽

Tibial Tuberosity ◽

Teaching Hospitals ◽

Avulsion Fractures ◽

Affected Side ◽

Tibial Tuberosity Fracture ◽

Significant Difference

Abstract Objective This study aimed to analyse the epidemiological data of canine appendicular avulsion fractures from three academic veterinary hospitals in the United States. Study Design A total of 114 avulsion fractures that presented to three study centres (teaching hospitals in New York, California, and Michigan) between 2008 and 2018 were analysed for avulsion type, breed, sex, body weight, age and affected side. Results The mean age for avulsion fractures was 1.6 years (±2.3 standard deviation), and side and sex were comparable (53% females and 54% left sided, only 2% bilateral). Tibial tuberosity fracture was the most common type, comprising 54% of all avulsion fractures, significantly more prevalent in younger and lighter dogs (p < 0.001). There was no significant difference in avulsion type, breed, sex, weight, age and affected side among three study centres (p = 0.66). Conclusion The most common avulsion fractures were tibial tuberosity fractures, which tend to occur in young, small dogs. There is no sex or side predilection for avulsion fractures noted in this study, although the effect of neuter could not be determined. There were no differences in fracture characteristics among the three different geographical locations in the United States.

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Powdery Mildew Resistant Rootstocks that Impart Tolerance to Grafted Susceptible Watermelon Scion Seedlings

Plant Disease ◽

10.1094/pdis-09-17-1384-re ◽

2018 ◽

Vol 102 (7) ◽

pp. 1290-1298 ◽

Cited By ~ 7

Author(s):

Chandrasekar S. Kousik ◽

Mihir Mandal ◽

Richard Hassell

Keyword(s):

United States ◽

Powdery Mildew ◽

Disease Severity ◽

Citrullus Lanatus ◽

The United States ◽

Bottle Gourd ◽

Economic Losses ◽

Podosphaera Xanthii ◽

Lagenaria Siceraria ◽

True Leaf

Powdery mildew (PM) is a major foliar disease causing serious economic losses of cucurbit crops grown in the United States. The pathogen Podosphaera xanthii, which causes PM, is known to infect seedlings, stems, foliage, petioles, and fruit of cucurbit crops. In recent years, grafting watermelon on resistant rootstocks for managing soilborne diseases has been gaining popularity in the U.S.A. However, grafting for managing foliar diseases has not yet received adequate attention. Three greenhouse experiments were conducted during the summer months of 2012, 2013, and 2014 to determine if PM-resistant rootstocks could impart resistance to a susceptible watermelon scion. Susceptible watermelon scion ‘Mickey Lee’ seedlings were grafted onto 25 watermelon (Citrullus lanatus, C. amarus, C. mucosospermus) and four bottle gourd (Lagenaria siceraria) rootstocks. Grafted plants were inoculated with a 2 × 104 conidia ml−1 suspension of P. xanthii conidia and disease severity was rated 14 days after inoculation. Mickey Lee grafted on six PM-resistant watermelon rootstocks had significantly (P ≤ 0.05) lower PM severity on cotyledons, 2nd true leaf, and upper leaves (rating for 3rd to 7th or 8th true leaf) compared with Mickey Lee grafted on susceptible watermelon USVL677-PMS or bottle gourd USVL848-PMS rootstocks. However, some of the resistant watermelon rootstocks did not impart significant resistance to the scion. The resistant bottle gourd rootstocks USVL482-PMR and USVL351-PMR provided significantly greater levels of resistance, compared with many of the resistant watermelon rootstocks. Grafting watermelon on resistant rootstocks may help mitigate the effects of PM on susceptible scion seedlings.

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First Report of Powdery Mildew Caused by Podosphaera xanthii on Sechium edule in the United States

Plant Disease ◽

10.1094/pdis-93-12-1348a ◽

2009 ◽

Vol 93 (12) ◽

pp. 1348-1348 ◽

Cited By ~ 2

Author(s):

R. Singh ◽

D. M. Ferrin ◽

M. C. Aime

Keyword(s):

United States ◽

Powdery Mildew ◽

New Orleans ◽

Dna Analysis ◽

The United States ◽

Abaxial Surface ◽

Internal Transcribed Spacer Region ◽

Voucher Specimen ◽

First Report ◽

Sechium Edule

Sechium edule (Jacq.) Sw., also known as mirliton or chayote, is a perennial, monoecious, cucurbitaceous plant native to Mexico and Central America. It is cultivated worldwide for a variety of uses (4). Mirliton fruit is rich in carbohydrates, has 16 amino acids, and is a traditional staple in New Orleans, LA. During the spring of 2009, the LSU AgCenter's Plant Disease Diagnostic Clinic received diseased mirliton plants from a small commercial grower in New Orleans. Symptoms included yellow, irregular spots on both surfaces of the leaves. Microscopic examination revealed the presence of powdery mildew conidia and conidiophores. Initially, white, cottony mycelial colonies were present on the abaxial surface, but as the disease progressed, white, cottony colonies developed on the adaxial surface, the spots coalesced, and the entire leaf turned yellow and necrotic. Conidia were hyaline, ovoid, borne in long chains with crenate edges, and measured 25.6 to 36.6 μm long (mean = 31.2) × 14.6 to 18.3 μm wide (mean = 17.1). Conidia contained fibrosin bodies and produced a lateral germ tube with a simple appressorium. Conidiophores were erect, simple, unbranched, and measured 54.9 to 76.9 μm long (mean = 66.4) × 11.0 to 14.6 μm wide (mean = 12.9). The cylindrical foot cell had a simple base with basal septum adjacent to the mycelium. No teleomorph was observed. Morphologically, this powdery mildew fits either Podosphaera fusca or P. xanthii so DNA analysis was conducted. We designed Podosphaera-specific primers PFITS-F (5′-CCAACTCGTGCTGTGAGTGT-3′) and PF5.8-R (5′-TGTTGGTTTCTTTTCCTCCG-3′) to amplify and sequence the internal transcribed spacer region (ITS) of the nuclear rDNA. The 331-bp sequence (GenBank Accession No. GQ902939) was identical with haplotype 27 of P. fusca (GenBank Accession No. AB040324) (3), which is now called P. xanthii (1). Pathogenicity tests were conducted by pressing infected leaves against healthy leaves of two vines. A noninoculated vine served as a control. Plants were maintained in a greenhouse at 30°C. Five days after inoculation, yellow, irregular spots appeared on the inoculated vines and white, powdery mildew colonies appeared on the abaxial surface. Spots coalesced and the entire leaf turned yellow 8 days after inoculation and necrotic 12 days after inoculation. No symptoms developed on the controls. On the basis of DNA sequence data, this powdery mildew is identified as P. xanthii sensu (1). Erysiphe cichoracearum has been previously reported to cause powdery mildew on mirlitons in Florida and Hawaii (2). To our knowledge, this is the first report of powdery mildew caused by P. xanthii on mirliton in the United States. A voucher specimen has been deposited in the Bernard Lowy Mycological Herbarium (LSUM 185359). References: (1) U. Braun and S. Takamatsu. Schlechtendalia 4:31, 2000. (2) D. F. Farr and A. Y. Rossman. Fungal Databases. Systematic Mycology and Microbiology Laboratory, SMML, Online publication. USDA-ARS, 2009. (3) T. Hirata et al. Can. J. Bot. 78:1521, 2000. (4) M. Janssens et al. Tropical Crops. ARTS; Field and Vegetable Crops, PTS 130. Bonn, Germany, 2002/03.

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