Browsing by Author "Dugan, F.M."

Now showing 1 - 7 of 7

Erysiphe trifolii Causing Powdery Mildew of Lentil (Lens culinaris)
(Plant Disease, 2009) Attanayake, R.N.; Glawe, D.A.; Dugan, F.M.; Chen, W.
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.
Erysiphe trifolii? a newly recognized powdery mildew pathogen of pea
(Plant Pathology, 2010) Attanayake, R.N.; Glawe, D.A.; McPhee, K.E.; Dugan, F.M.; Chen, W.
Diversity of powdery mildew pathogens infecting pea (Pisum sativum) in the US Pacific Northwest was investigated using both molecular and morphological techniques. Phylogenetic analyses based on rDNA ITS sequences, in combination with assessment of morphological characters, defined two groups of powdery mildews infecting pea. Group I (five field samples and three glasshouse samples) had ITS sequences 99% similar to those of Erysiphe pisi in GenBank and exhibited simple, mycelioid type of chasmothecial appendages typical of E. pisi. Erysiphe pisi is normally considered as the powdery mildew pathogen of pea. Group II (four glasshouse samples and two field samples) had ITS sequences 99% similar to those of E. trifolii and produced chasmothecia with dichotomously branched appendages similar to those of E. trifolii. There are fourteen nucleotide differences in the ITS region between the two groups. The correlation of rDNA ITS sequences with teleomorphic features for each of the two groups confirms their identity. Repeated samplings and artificial inoculations indicate that both E. pisi and E. trifolii infect pea in the US Pacific Northwest. Erysiphe trifolii is not previously known as a pathogen of pea. The existence of two distinct powdery mildew species infecting pea in both glasshouse and field environments may interfere with the powdery mildew-resistance breeding programmes, and possibly explains putative instances of breakdown of resistance in previously resistant pea breeding lines.
First Report of Powdery Mildew of Chickpea (Cicer arietinum) Caused by Leveillula taurica in Washington State
(Plant Health Progress, 2008) Chen, W.; Attanayake, R.N.; Glawe, D.A.; McPhee, K.E.; Dugan, F.M.
In Oct. 2007, powdery mildew was found in chickpea fields in an experimental farm near Pullman, Whitman County, Washington. Although disease signs were observed on all chickpea cultivars in the fields, high incidence was seen only on cvs. Dwelley and Spanish White. To our knowledge this is the first record of powdery mildew caused by Leveillula taurica on chickpea in WA. The pathogen has also been reported from chickpea in California and elsewhere, e.g., Ethiopia, India, Iran, Morocco, Pakistan, Sudan, Turkey, and the former USSR.
Potential alternative hosts for a powdery mildew on pea
(Phytopathology, 2009) Attanayake, R.N.; Glawe, D.A.; Dugan, F.M.; Chen, W.
Powdery mildew of pea (Pisum sativum) is an important disease in the field and in the greenhouse. The most widely documented powdery mildew on pea is Erysiphe pisi, but E. trifolii and E. baeumleri have also been reported. From greenhouse-grown peas, we obtained powdery mildew samples with rDNA ITS sequences nearly identical to previously deposited sequences of E. trifolii. Because detailed studies on host range of this pea powdery mildew in the US Pacific Northwest were lacking, we tested common legume plants from the region as potential alternative hosts. Eleven species were used in greenhouse cross inoculation studies: Lens culinaris, Glycine max, Melilotus albus, M. officinalis, Medicago polymorpha, M. lupulina, M. scutellata, Lathyrus latifolius, Trifolium pratense, Vicia cracca, and V. faba. Except for Glycine max, all the plant species tested developed powdery mildew lesions in 10?14 days after inoculation. Susceptibilities of two of these species (L. culinaris and M. albus) were also confirmed with detached leaf assays. Results showed that all the above legumes (except soybean) are potential alternative hosts for the E. trifolii found on pea. Powdery mildews found on wild legumes (Meliotus albus and Medicago lupulina) were also confirmed to be E. trifolii, suggesting that the wild legumes could be inoculum sources of powdery mildew on greenhouse pea plants during winter months. These findings have implications in managing powdery mildew of pea.
Potential alternative hosts for pea powdery mildew pathogen Erysiphetrifolii
(Pisum genetics, 2010) Attanayake, R.N.; Dugan, F.M.; Glawe, D.A.; McPhee, K.E.
Powdery mildew is an important disease of peas grown in both greenhouses and in the field. The latter is obviously important for commercial production, but greenhouses are often used to increase the number of generations per year in pea breeding programs. Even though Erysiphe pisi (often reported as E. communis or E. polygoni in earlier literature) is the most commonly documented pathogen species causing powdery mildew of peas, E. baeumleri (1) and E. trifolii (2) were recorded as powdery mildew pathogens on peas. It has been presumed that the putative breakdown of resistance in previously resistant pea cultivars observed in the US Pacific Northwest (US PNW) was actually due to the presence of more than one species of Erysiphe (2). Attanayake et al. (2) observed severe disease symptoms caused by E. trifolii on resistant pea cv. 'Lifter' grown in greenhouse conditions. Greenhouse-grown pea breeding materials often get infected with powdery mildew in the US PNW (K. McPhee, personal communication). However, the inoculum source, particularly for greenhouse-grown peas during the winter months, has not been determined. Since during winter months no pea crops are growing in fields in the PNW, inoculum would have to originate from pea debris of the previous growing season, volunteer pea plants or from powdery mildew-infected wild legume plants serving as alternative hosts. Many powdery mildew pathogens are known to have broad host ranges (3). E. trifolii has been reported on peas and lentils in the US PNW (2, 4) and on Trifolium (as the specific epithet indicates) and other genera of the Fabaceae such as Acacia, Arachis, Lathyrus, and Melilotus (5). Species of Arachis, Dolichos, Lathyrus, Lens, Lupinus, Medicago, Melilotus, Phaseolus, Trifolium and Vicia are known hosts for E. pisi (5). The above abbreviated host lists make it clear that E. trifolii and E. pisi have numerous hosts, including some hosts in common. Powdery mildew-infected Medicago lupulina, Melilotus spp., Lathyrus spp. and Vicia spp. plants are abundant along road sides, recreational areas and commercial fields during the periods of July-November in the Palouse region of Idaho and Washington. We hypothesized that these weedy legumes can serve as alternative hosts for E. trifolii. Detailed studies on host range of E. trifolii in the US PNW are lacking, so we tested these common weedy legumes from the region as potential alternative hosts of E. trifolii.
Taxonomic complexity of powdery mildew pathogens found on lentil and pea in the U.S. Pacific Northwest
(Phytopathology, 2008) Attanayake, R.N.; Glawe, D.A.; McPhee, K.E.; Dugan, F.M.; Chen, W.
and field production conditions in the U.S. Pacific Northwest was investigated using morphological and molecular characters. Isolates collected from lentil plants grown in the greenhouse or field displayed morphologies in substantial agreement with descriptions of Erysiphe trifolii, but sometimes with more extensively branched chasmothecial appendages resembling those of E. diffusa. ITS sequences of the lentil fungi were identical to each other, and more similar to GenBank accessions of E. trifolii (99.5%) than of E. diffusa (97%). The data suggest there may be more than one Erysiphe species causing lentil powdery mildew. The fungus on field-grown pea plants was determined to be E. pisi. However, powdery mildew samples obtained from greenhouse pea plants were either E. pisi or E. trofolii depending on the time of sampling and greenhouse location. Therefore, the powdery mildews infecting lentil and pea are more diverse than previously assumed. Powdery mildews from black medic (Medicago sp.) and sweet clover (Melilotus sp.) found near the greenhouses exhibited ITS sequences with 99.9 to 100% similarity to isolates from lentil and pea in the greenhouses, and to isolates from lentil from the field. These weedy legumes could be inoculum sources for powdery mildew of lentil and pea in the greenhouses, and serve as alternative hosts for cultivated legumes.
The Importance of Reporting New Host-Fungus Records for Ornamental and Regional Crops
(Peer-Reviewed by Plant Health Progress, 2009) Dugan, F.M.; Glawe, D.A.; Attanayake, R.N.; Chen, W.
Accurate and timely reports of new host-fungus records are essential for diagnostics and identification, management, and prevention of plant diseases. Important also are venues to publish these reports in a timely manner and the ability to rapidly search for the information contained in these reports. Presented herein are examples of first reports of fungal pathogens on regional crops, including ornamentals and turf grasses, which illustrate how first reports contribute to preparedness, accurate diagnostics, and knowledge of biogeography and host range. We provide a guide to sources of host-fungus records, discuss venues for publishing new records, and review the information important in a new record, including deposition of voucher specimens. We appeal to plant health professionals to increase their efforts of discovering, documenting, and reporting new records.