Erysiphe trifolii Causing Powdery Mildew of Lentil (Lens culinaris)

The taxonomy of the powdery mildew fungus infecting lentil in the Pacific Northwest (PNW) of the United States was investigated on the basis of morphology and rDNA internal transcribed spacer (ITS) sequences. Anamorphic characters were in close agreement with descriptions of Erysiphe trifolii. However, teleomorphs formed chasmothecial appendages with highly branched apices, whereas E. trifolii has been described as producing flexuous or sometimes loosely branched appendages. Branched appendages have been described in Erysiphe diffusa, a fungus reported from species of Lens, Glycine, and Sophora, raising the possibility that the PNW fungus could be E. diffusa. Examination of morphological characters of an authentic specimen of E. trifolii from Austria determined that it included chasmothecial appendages resembling those seen in PNW specimens. Furthermore, ITS sequences from five powdery mildew samples collected from lentils in PNW greenhouses and fields from 2006 to 2008 were identical to one another, and exhibited higher similarity to sequences of E. trifolii (99%) than to those of any other Erysiphe spp. available in GenBank. Parsimony analysis grouped the lentil powdery mildew into a clade with Erysiphe baeumleri, E. trifolii, and E. trifolii–like Oidium sp., but indicated a more distant relationship to E. diffusa. In greenhouse inoculation studies, the lentil powdery mildew fungus did not infect soybean genotypes known to be susceptible to E. diffusa. The pathogenicity of E. trifolii on lentil was confirmed using modified Koch's postulates. This is the first report of E. trifolii infecting lentil. E. diffusa and E. trifolii have different host ranges, so the discovery of E. trifolii on lentil has implications both for determining species of powdery mildews on cool-season grain legumes, and in disease management.

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First Report of Powdery Mildew, Caused by an Oidium sp., on Poinsettia in California

Plant Disease ◽

10.1094/pdis.1998.82.1.128a ◽

1998 ◽

Vol 82 (1) ◽

pp. 128-128 ◽

Cited By ~ 3

Author(s):

S. T. Koike ◽

G. S. Saenz

Keyword(s):

United States ◽

Powdery Mildew ◽

Pacific Northwest ◽

The United States ◽

Euphorbia Pulcherrima ◽

American Phytopathological Society ◽

First Report ◽

The Pacific ◽

Uninoculated Control ◽

Alternative Identification

In December 1996 and January 1997, powdery mildew was observed on potted poinsettia (Euphorbia pulcherrima Willd. ex Klotzsch) plants in Monterey County, CA. Mycelia were observed on stems, petioles, mature and immature leaves, and bracts. Severely diseased leaves became twisted and bent and senesced prematurely. The white mycelia were conspicuous, epiphytic, and amphigenous; hyphae measured 4.6 to 6.9 μm in diameter. Growth initially was in patches but eventually became effused. Appressoria were slightly lobed to lobed and sometimes opposite. Conidiophore foot cells were cylindrical, sometimes bent at the base, and slightly flexuous to flexuous. Foot cells measured 30.0 to 46.2 μm × 5.8 to 6.9 μm and were followed by one to two shorter cells. Conidia were cylindrical to slightly doliform and measured 25.4 to 32.3 μm × 11.6 to 18.5 μm. The length-to-width ratios of conidia generally were greater than 2.0. Conidia were produced singly, placing the fungus in the Pseudoidium-type powdery mildew group. Conidia germinated at the ends, and no fibrosin bodies were observed. Cleistothecia were not found. The fungus was identified as an Oidium species. Pathogenicity was demonstrated by gently pressing infected leaves having abundant sporulation onto leaves of potted poinsettia plants (cvs. Freedom Red, Peter Star Marble, and Nutcracker White), incubating the plants in a moist chamber for 48 h, and then maintaining plants in a greenhouse. After 12 to 14 days, powdery mildew colonies developed on the inoculated plants, and the pathogen was morphologically identical to the original isolates. Uninoculated control plants did not develop powdery mildew. This is the first report of powdery mildew on poinsettia in California. This fungus appears similar to Microsphaera euphorbiae but has longer, slightly flexuous foot cells that do not match the description for M. euphorbiae (1,2). An alternative identification would be Erysiphe euphorbiae; however, there are no available mitosporic descriptions for morphological comparisons (1,2). In the United States, powdery mildew of poinsettia previously has been reported in various states in the Pacific Northwest, Midwest, and Northeast. References: (1) U. Braun. Beih. Nova Hedwigia 89:1, 1987. (2) D. F. Farr et al. 1989. Fungi on Plants and Plant Products in the United States. American Phytopathological Society, St. Paul, MN.

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First Report of Powdery Mildew of Eschscholzia californica (California Poppy) caused by Erysiphe cruciferarum in North America

Plant Health Progress ◽

10.1094/php-2006-1213-01-br ◽

2006 ◽

Vol 7 (1) ◽

pp. 45 ◽

Cited By ~ 1

Author(s):

Dean A. Glawe

Keyword(s):

North America ◽

Powdery Mildew ◽

Pacific Northwest ◽

Ongoing Study ◽

Annual Species ◽

Powdery Mildew Fungus ◽

First Report ◽

California Poppy ◽

The Pacific ◽

Erysiphe Cruciferarum

California poppy is an annual species grown widely in the Pacific Northwest. Once established, populations are self-seeding and require little care. During an ongoing study of Erysiphales, a powdery mildew fungus was collected repeatedly on this species in Seattle, WA. The fungus was determined to be Erysiphe cruciferarum Opiz ex Junell, a species not reported previously on this host in North America. This report documents the occurrence of the disease and provides information on the morphology and identification of the causal agent. Accepted for publication 8 November 2006. Published 13 December 2006.

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Sclerotinia Wilt of Hop (Humulus lupulus) Caused by Sclerotinia sclerotiorum in the Pacific Northwest United States

Plant Disease ◽

10.1094/pdis-12-11-1039 ◽

2012 ◽

Vol 96 (4) ◽

pp. 583-583

Author(s):

S. M. Kropf ◽

M. L. Putnam ◽

M. Serdani ◽

M. C. Twomey ◽

J. L. Woods ◽

...

Keyword(s):

United States ◽

Pacific Northwest ◽

Sclerotinia Sclerotiorum ◽

Pcr Amplification ◽

Soil Surface ◽

The United States ◽

Morphological Characters ◽

Nucleotide Polymorphisms ◽

Foliar Symptoms ◽

The Pacific

In June 2009, wilted hop bines were observed in a yard in Marion County, OR. The wilt was associated with a stem rot that occurred ~1 m from the ground near the point where bines are tied together for horticultural purposes. Samples of affected stems were submitted to the Oregon State University Plant Clinic. White hyphae and large, black sclerotia were present on the stems, with a clear delineation between healthy and diseased tissue. The pathogen was identified as Sclerotinia sclerotiorum based on morphological characters. In June 2011, bine wilting was observed on the same farm but in a different hop yard (cv. Nugget) ~10 km from the 2009 occurrence. Affected plants had upward curled leaves with necrotic margins or wilted bines that were severed at the soil line. Wilted bines tended to have smaller diameters than bines with foliar symptoms only. Of 100 plants examined, 75% displayed some foliar symptoms and 66% had at least one bine that was wilted. Yield loss was estimated at 10 to 20% due to bine wilting before cone development. Unlike the 2009 occurrence, wilted bines did not display aerial signs of S. sclerotiorum. Rather, water-soaked lesions covered in white, cottony mycelium were apparent on affected stems 2.5 to 5 cm below the soil surface, some bearing large, irregularly shaped sclerotia. Isolations made onto potato dextrose agar yielded isolates with rapid growth rates and morphological characters consistent with S. sclerotiorum (1). DNA was extracted (2) and pathogen identity was confirmed by PCR amplification and sequencing of the internal transcribed spacer regions from isolates SS001 and SS002 as described before (4). The amplicons were sequenced bidirectionally and consensus sequences were 100% similar to S. sclerotiorum (GenBank No. AAGT01000678.1). Two nucleotide polymorphisms were present that differentiated the sequences from those of 12 S. trifoliorum accessions in GenBank that could be aligned (2). Greenhouse assays utilizing a toothpick inoculation procedure (3) were conducted to fulfill Koch's postulates. Stems of five 4-week-old hop plants of cv. Agate were pierced with a toothpick colonized with S. sclerotiorum. Five control plants were similarly inoculated with toothpicks without the fungus. Inoculated plants developed symptoms similar to those observed in the field within 11 days; four of five plants inoculated with isolate SS001 and two of five plants inoculated with isolate SS002 completely wilted. S. sclerotiorum was reisolated from all inoculated plants but not the control plants. To our knowledge, this is the first report of Sclerotinia wilt on hop in Oregon or the Pacific Northwest (1), where nearly all commercial hop production occurs in the United States. The disease appears to be localized to a limited number of yards, although given the widespread distribution and host range of S. sclerotiorum, it is plausible that the disease may occur in other yards. Recurrent outbreaks and spread of the disease among yards on the affected farm suggests that Sclerotinia wilt has the potential to become a perennial problem on hop and efforts to limit the introduction of S. sclerotiorum into other yards are warranted. References: (1) D. H. Gent. Page 32 in: Compendium of Hop Diseases and Pests. The American Phytopathological Society, St. Paul, MN, 2009. (2) E. N. Njambere et al. Plant Dis. 92:917, 2008. (3) M. L. Putnam. Plant Pathol. 53:252, 2004. (4) T. J. White et al. PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, 1990.

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First Report of Powdery Mildew Caused by Leveillula taurica on Giant Blazing Star (Mentzelia laevicaulis)

Plant Disease ◽

10.1094/pdis-94-1-0132a ◽

2010 ◽

Vol 94 (1) ◽

pp. 132-132 ◽

Cited By ~ 2

Author(s):

R. K. Sampangi ◽

D. A. Glawe ◽

T. Barlow ◽

S. K. Mohan

Keyword(s):

Powdery Mildew ◽

Pacific Northwest ◽

Host Species ◽

The United States ◽

Similar Species ◽

Voucher Specimen ◽

First Report ◽

Leveillula Taurica ◽

The Pacific ◽

Native Host

Mentzelia laevicaulis (Dougl. ex Hook.) Torr. & Gray (Loasaceae; common names are giant blazing star and smoothstem blazing star) is widely distributed throughout western North America in sites ranging from lowland deserts to mountainous areas in Canada and the United States. During a plant disease survey in June 2007 in the Owyhee Mountains, Canyon County, Idaho, leaves of M. laevicaulis displaying whitish, mycelial growth were collected from plants growing on stream banks and gravelly road embankments. Diseased leaves exhibited localized, chlorotic discolorations associated with signs of a powdery mildew. Of approximately 20 plants at the site, 50% were infected. White mycelia and conidia were more abundant on the adaxial leaf surfaces than on the abaxial surfaces. Severely diseased leaves were buckled and slightly twisted. By August and through September, sporulation was greatest on mature plants, and lowermost leaves were completely covered with flocculose, dense, white mycelia. Dimorphic conidia were lanceolate or cylindrical and measured (44-) 46 to 67 (-71) × (14-) 14.5 to 20 (-21) μm. DNA was extracted and PCR was used to amplify the internal transcribed spacer (ITS) region as described previously (2), except that primers ITS 5 and P3 (4) were used. The resulting 633-bp sequence (GenBank Accession No. GQ860947) included a 616-bp region identical to a sequence reported previously for Leveillula taurica (Lév.) Arnaud from eastern Washington (GenBank No. AY912077), as well as ITS regions from L. taurica previously reported from Iran (GenBank No. AB048350) (2) and Australia (GenBank No. AF 073351) (2). Based on the ITS sequence, the present fungus grouped within Khodaparast et al. (3) Clade 1 that included L. taurica strains they distinguished from other, superficially similar species of Leveillula. On the basis of morphological and sequence data, the fungus was determined to be L. taurica (1,3). A voucher specimen was deposited in the Mycology Herbarium (WSP) at Washington State University. To our knowledge, this is the first report of a named powdery mildew species from a member of the Loasaceae. The only previous report of a powdery mildew on a loasaceous host was an undetermined Oidium sp. on a species of Mentzelia (1). The discovery of L. taurica on a previously unknown native host species is further evidence that this introduced pathogen is becoming endemic to the Pacific Northwest. Native host species, such as M. laevicaulis, may play a role in the epidemiology of powdery mildew diseases caused by L. taurica on crop and ornamental species in the Pacific Northwest. References: (1) U. Braun. Beih. Nova Hedwigia 89:1, 1987. (2) D. A. Glawe et al. Mycol. Prog. 4:291, 2005. (3) S. A. Khodaparast et al. Mycol. Res. 105:909, 2001. (4) S. Takamatsu and Y. Kano. Mycoscience 42:135, 2001.

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A Decade of Hop Powdery Mildew in the Pacific Northwest

Plant Health Progress ◽

10.1094/php-2008-0314-01-rv ◽

2008 ◽

Vol 9 (1) ◽

pp. 33 ◽

Cited By ~ 18

Author(s):

David H. Gent ◽

Mark E. Nelson ◽

Ann E. George ◽

Gary G. Grove ◽

Walter F. Mahaffee ◽

...

Keyword(s):

Powdery Mildew ◽

Pacific Northwest ◽

Sustainable Management ◽

The United States ◽

Future Directions ◽

Loss And Damage ◽

The Pacific ◽

The Us ◽

Management Approaches ◽

First Time

Hop powdery mildew, caused by the fungus Podosphaera macularis, was confirmed for the first time in hop yards in the United States Pacific Northwest in 1997. The US hop industry experienced significantly crop loss and damage from the disease, but new knowledge, grower experience, and management approaches have allowed the industry to survive the introduction of this damaging pathogen. This review provides an overview of research on and progress towards economically sustainable management of hop powdery mildew in the US, and future directions for research and further innovation. Accepted for publication 2 January 2008. Published 14 March 2008.

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First Report of Powdery Mildew of Convolvulus arvensis (Field Bindweed) Caused by Erysiphe convolvuli var. convolvuli in North America

Plant Health Progress ◽

10.1094/php-2003-1021-01-hn ◽

2003 ◽

Vol 4 (1) ◽

pp. 31

Author(s):

Dean A. Glawe ◽

Gwenyth E. Windom ◽

Gary G. Grove ◽

Jennifer S. Falacy

Keyword(s):

North America ◽

Powdery Mildew ◽

Pacific Northwest ◽

Morphological Features ◽

Convolvulus Arvensis ◽

Powdery Mildew Fungus ◽

First Report ◽

The Pacific ◽

Field Bindweed ◽

Noxious Weed

Field bindweed (Convolvulus arvensis L.) is widespread in the Pacific Northwest where it is considered a noxious weed. During 2002, collections of a powdery mildew fungus attacking C. arvensis were made from Pierce, Spokane, Whitman, and Yakima counties, WA. Based on morphological features we determined the fungus to be Erysiphe convolvuli. Accepted for publication 22 September 2003. Published 21 October 2003.

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Discovery and Genetic Mapping of PM1, a Powdery Mildew Resistance Gene in Cannabis sativa L.

Frontiers in Agronomy ◽

10.3389/fagro.2021.720215 ◽

2021 ◽

Vol 3 ◽

Author(s):

Paul D. Mihalyov ◽

Andrea R. Garfinkel

Keyword(s):

Powdery Mildew ◽

Pacific Northwest ◽

Cannabis Sativa ◽

Genetic Resistance ◽

The United States ◽

Snp Markers ◽

The Pacific ◽

Powdery Mildew Pathogen ◽

Lrr Protein

Powdery mildew is among the most common diseases of both hemp- and marijuana-type cultivated Cannabis sativa. Despite its prevalence, no documented studies have characterized sources of natural genetic resistance in this pathosystem. Here we provide evidence for the first resistance (R) gene in C. sativa, represented by a single dominant locus that confers complete resistance to an isolate of the powdery mildew pathogen Golovinomyces ambrosiae, found in the Pacific Northwest of the United States. Linkage mapping with nearly 10,000 single nucleotide polymorphism (SNP) markers revealed that this R gene (designated PM1) is located on the distal end of the long arm of one of the largest chromosomes in the C. sativa genome. According to reference whole genome sequences and Sanger sequencing, the marker was tentatively placed in a cluster of R genes of the nucleotide-binding site (NBS) and leucine-rich repeat (LRR) protein type. PM1's dominant behavior, qualitative penetrance, and a co-segregating qPCR marker to track its inheritance were confirmed in two separate genetic backgrounds totaling 185 recombinant F1 plants. The goal of this study is to provide a foundation for the discovery and characterization of additional sources of genetic resistance to pathogens that infect C. sativa.

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Oidium longipes, A New Powdery Mildew Fungus on Petunia in the USA: A Potential Threat to Ornamental and Vegetable Solanaceous Crops

Plant Disease ◽

10.1094/pdis-92-5-0818 ◽

2008 ◽

Vol 92 (5) ◽

pp. 818-825 ◽

Cited By ~ 15

Author(s):

Levente Kiss ◽

Tünde Jankovics ◽

Gábor M. Kovács ◽

Margery L. Daughtrey

Keyword(s):

United States ◽

New Jersey ◽

Powdery Mildew ◽

The United States ◽

Microscopy Study ◽

Its Sequences ◽

Herbarium Specimens ◽

Powdery Mildew Fungus ◽

Potential Threat ◽

Field Surveys

This is the first North American report of Oidium longipes, an anamorphic powdery mildew species described recently in Europe. It was found on vegetatively propagated petunia grown in a commercial greenhouse in New Jersey, USA, where it caused a rapidly spreading disease. The pathogen might have originated offshore and may have already been distributed in the United States through horticultural trade. During field surveys in Europe, it was found on petunia in Hungary and Austria as well; this is the first report of O. longipes from these two countries. A detailed light microscopy study of American and European specimens of O. longipes, including freshly collected samples and authentic herbarium specimens, revealed that its conidiophore morphology is more variable than illustrated in the original species description or in subsequent works. Microcycle conidiation, a process not yet known to occur in powdery mildews, was repeatedly observed in O. longipes. The rDNA internal transcribed spacer (ITS) sequences were identical in colonies containing different conidiophore types as well as in a total of five specimens collected from petunia in the United States, Austria, Hungary, Germany, and Switzerland. A phylogenetic analysis of the ITS sequences revealed that the closest known relative of O. longipes is O. lycopersici, known to infect tomato only in Australia. Cross-inoculation tests showed that O. longipes from petunia heavily infected tobacco cv. Xanthi, while the tomato and eggplant cultivars tested were moderately susceptible to this pathogen. These results indicate that its spread represents a potential danger to a number of solanaceous crops. Our ad hoc field surveys conducted in 2006 and 2007 did not detect it outside New Jersey in the United States; all the other powdery mildew–infected petunias, collected in New York and Indiana, were infected by Podosphaera xanthii. In Europe, most of the powdery mildew–infected petunias examined in this study were infected by P. xanthii or Golovinomyces orontii. Our multiple inoculation tests revealed that the same petunia plants and even the same leaves can be infected concomitantly by O. longipes, O. neolycopersici, G. orontii, and P. xanthii. Thus, it is at present unclear to what extent O. longipes contributes to the powdery mildew epidemics that develop year after year on solanaceous plants in many parts of the world.

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First Report of Powdery Mildew of Kalanchoe blossfeldiana caused by Sphaerotheca fuliginea (Podosphaera fuliginea) in the Pacific Northwest

Plant Health Progress ◽

10.1094/php-2003-0417-02-hn ◽

2003 ◽

Vol 4 (1) ◽

pp. 39

Author(s):

Dean A. Glawe ◽

Rita Hummel ◽

Grace Jack

Keyword(s):

Powdery Mildew ◽

Pacific Northwest ◽

Sphaerotheca Fuliginea ◽

First Report ◽

Major Disease ◽

The Pacific ◽

Kalanchoe Blossfeldiana ◽

Extension Center ◽

Kalanchoë Blossfeldiana

Kalanchoe blossfeldiana Poelln. is a common ornamental houseplant. Although powdery mildew is a major disease of this species, there are no published reports of it in the Pacific Northwest. In August, 2002, powdery mildew was observed on six indoor K. blossfeldiana plants in an office and adjacent laboratory at the Puyallup Research and Extension Center. Accepted for publication 25 March 2003. Published 17 April 2003.

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First record of Euxestonotus error (Hymenoptera: Platygastridae) in the Pacific Northwest, United States of America

The Canadian Entomologist ◽

10.4039/tce.2016.8 ◽

2016 ◽

Vol 148 (5) ◽

pp. 616-618 ◽

Cited By ~ 2

Author(s):

E.R. Echegaray ◽

R.N. Stougaard ◽

B. Bohannon

Keyword(s):

United States ◽

New York ◽

Pacific Northwest ◽

United States Of America ◽

First Record ◽

The United States ◽

Sitodiplosis Mosellana ◽

Wheat Midge ◽

The Pacific ◽

Northwestern Montana

AbstractEuxestonotus error (Fitch) (Hymenoptera: Platygastridae) is considered part of the natural enemy complex of the wheat midge Sitodiplosis mosellana (Géhin) (Diptera: Cecidomyiidae). Although previously reported in the United States of America, there is no record for this species outside the state of New York since 1865. A survey conducted in the summer of 2015 revealed that E. error is present in northwestern Montana and is likely playing a role in the suppression of wheat midge populations.

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