bluuebunny/crossref_metadata_2025 huggingface dataset:
Occurrence and Partial Characterization of a New Mechanically Transmissible Virus in Mashua from the Ecuadorian Highlands
Authors: Soria S. L. , Vega R. , Damsteegt V. D. , McDaniel L. L. , Kitto S. L. , Evans T. A.
Published: May 2007

Mashua (Tropaeolum tuberosum) is a tuber crop indigenous to the Andean highlands and of economic value to its native people as a food and medicinal crop. Field plants often exhibit symptoms typical of virus infection, including interveinal chlorosis, leaf cupping, distortion, and stunting. Using an herbaceous host range, at least 1 mechanically transmissible virus was detected in each of 10 accessions. All virus isolates tested reacted to potyvirus group antiserum in indirect enzyme-linked immunosorbent assays (ELISA). Results of monoclonal antibody testing using antigen coated plate (ACP) ELISA, where virions are disrupted to expose cryptotopes, indicated that isolate Tt 4 has epitopes in common with maize dwarf mosaic potyvirus A (MDMV-A). Polyclonal antiserum produced to purified preparations of the Tt 4 isolate reacted in indirect ELISA to Tt 4, the common strain of potato potyvirus Y (PVY-C), less strongly to tobacco etch potyvirus (TEV) and potato potyvirus A (PVA), but not to 11 other potyviruses, including MDMV-A. Conversely, the Tt 4 isolate reacted strongly in indirect ELISA to antisera to bean common mosaic potyvirus (BCMV) and watermelon mosaic potyvirus 2 (WMV-2), but not antisera to 12 other potyviruses. Our data suggest that isolate Tt 4 is a distinct potyvirus closely related to and sharing external epitopes with PVY-C, TEV, PVA, WMV-2, and BCMV, and buried epitopes with MDMV-A. The virus has been tentatively named Tropaeolum mosaic potyvirus (TropMV). A survey of T. tuberosum in Ecuador revealed that TropMV was widespread, being detected by ACP-ELISA in 34 of 46 accessions at the National Institute for Agricultural Research's Santa Catalina Research Station, Quito, and all eight production fields surveyed.
Location of Geminiviruses in the Whitefly Bemisia tabaci (Homoptera: Aleyrodidae)
Authors: Hunter W. B. , Hiebert E. , Webb S. E. , Tsai J. H. , Polston J. E.
Published: May 2007

The location of tomato mottle virus (ToMoV) and cabbage leaf curl virus (CabLCV) (Geminiviridae, genus Begomovirus) in the whitefly vector Bemisia tabaci B-biotype (Homoptera: Aleyrodidae) was elucidated using a novel technique incorporating indirect immunofluorescent labeling in freshly dissected whiteflies. Begomoviruses were visualized in the whitefly by indirect-fluorescent-microscopy. Polyclonal and monoclonal primary antibodies were used to successfully detect both ToMoV and CabLCV. Both begomoviruses were located in the anterior region of the midgut and filter-chamber of adult whiteflies, with ToMoV detected in the salivary glands. CabLCV was detected at a greater frequency than ToMoV, with a positive detection of 16% (89 out of 560) for CabLCV and 3% (25 out of 840) for ToMoV. Possible sites involved in geminivirus transport from the gut lumen of whiteflies into the hemocoel were located in the filter-chamber and anterior portion of the midgut. The location of these begomoviruses suggests a possible scenario of virus movement through the whitefly, which is discussed.
First Report of Erwinia amylovora on Crataegus monogyna and Pyrus pyraster in Bulgaria
Authors: Bobev S. G. , Crepel C. , Maes M.
Published: May 2007

Typical symptoms of fire blight, caused by Erwinia amylovora, were observed in late June of 1998 on Crataegus monogyna Jacq. (hawthorn) and Pyrus pyraster Burgsd. (syn. P. caucasia, wild or thorny pear) in the region of Plovdiv. Symptoms observed on hawthorn were shepherd's-crook shoots, necrotic flowers and fruitlets, and dried amber ooze droplets. On thorny pear, only infected shoots were detected. Isolation on King's B medium (2 days, 26°C) resulted in the appearance of whitish, glistening, rounded colonies. Based on their cultural characteristics, positive hypersensitive response (HR) on tobacco leaves, successful laboratory inoculations of hosts' shoots and pear fruitlets, positive serological reaction (slide agglutination), and target-specific polymerase chain reaction (PCR; 23S rDNA), the isolates from both species were placed in the E. amylovora group. The bacterium has also been isolated by the first author from Cydonia oblonga, Pyrus communis, Mespilus germanica, and Malus sylvestris within the 5-year period of 1989-1993 (1). To our knowledge this is the first official report of fire blight on C. monogyna and P. pyraster in Bulgaria.

Reference: (1) S. G. Bobev. 1995. Pages 121–126 in: Jubilee Scientific Session, Higher Agricultural Institute of Plovdiv, vol. 3, bk. 1. (In Bulgarian.)
Powdery Mildew of Field-Grown Tomato in Florida
Authors: Pernezny K. , Sonoda R. M.
Published: May 2007

Powdery mildew was observed affecting mature, field-grown, fresh-market tomatoes in southeastern Florida (St. Lucie, Martin, Palm Beach, and Broward counties). Outbreaks were noted in May of 1996 and throughout the spring of 1997. Affected leaves were generally yellow and, in some cases, developed a purplish cast. Whitish areas of fungal growth were often seen in the middle of lesions, but were less prominent than that reported for powdery mildew of field tomato in Hungary (2). Microscopic examination revealed that conidia were produced in chains, contained no fibrosin bodies, and were not dimorphic. Conidial measurements were 33.2 × 15.6 μm, based on 21 samples of five conidia taken from five different fields. These measurements were similar to those for an Erysiphe sp. causing powdery mildew of greenhouse tomato in New York (1). Greenhouse-grown tomato plants, cv. Sunny, in the fourth-true-leaf stage were inoculated with conidia scraped from lesions gathered in commercial fields. A single-edged razor blade was used to transfer the fungus to the adaxial surface of the test plants. Powdery mildew symptoms were observed within 10 days of inoculation. Morphology and size of conidia taken from greenhouse plants were similar to those for original field samples. This is the first report of powdery mildew of field-grown tomato in Florida.

References: (1) D. M. Karasevicz and T. A. Zitter. Plant Dis. 80:709, 1996. (2) L. Kiss. Plant Dis. 80:224, 1996.
First Report of Downy Mildew (Race 2) of Sunflowers in Italy
Authors: Zazzerini A. , Tosi L.
Published: May 2007

During a survey in the spring of 1997, sunflower (Helianthus annuus L.) plants with characteristic symptoms (stunting and veinal chlorosis of leaves) of downy mildew caused by Plasmopara helianthi Novot. were observed in two experimental fields in the central Italian region of Umbria. In the first field, used to evaluate 58 commercial sunflower hybrids, fewer than 1% of plants displayed typical downy mildew symptoms. In a second field, planted with the old susceptible cultivar Ala, disease incidence was 12%. The inoculum of P. helianthi (one isolate from each field) was obtained either from downy mildew-infected leaves or infested soil (from around the roots of diseased plants). All were collected according to a random distribution. From this collection, two isolates were identified as race 2 by the whole-seedling immersion technique (2) with differential cultivars: HA 89, AD 66, CM 90 RR, RHA 265, RHA 274, HIR 34, DM-2, and HA 335. All differential lines were tested twice with 30 seeds per replicate (four replicates per line). Two weeks after inoculation the percentage of susceptible seedlings (showing sporulation on cotyledons and/or first true leaves) was determined. Race 2 has long occurred in some European countries, but this is the first report of this race from Italy. Extensive field surveys carried out in the last 10 years revealed that race 1 is the only one occurring in central Italy. An isolate apparently comparable to race 2 was reported in experimental plots in 1975 (1) where only Pl1 cultivars were susceptible. Differential lines, at that time, were not available and race identification was not carried out. Italy imposes importation regulations for sunflower seed that include treatment with metalaxyl. In greenhouse trials we have not observed a reduction in sensitivity to this systemic fungicide used as seed treatment against P. helianthi race 2. Consequently, the susceptibility of some commercial hybrids, indicated as resistant to downy mildew by importers, could be attributed to irregularity in the production of seeds. Also, an insufficient seed dressing with metalaxyl does not completely control the pathogen.

References: (1) M. D'Armini et al. Atti Giornate Fitopatol. 1:659, 1975. (2) T. J. Gulya et al. Helia 14:11, 1991.
Southerly Extension of Poplar Leaf Blight (Linospora tetraspora) in the Pacific Northwest
Authors: Newcombe G.
Published: May 2007

Poplar leaf blight caused by Linospora tetraspora G. E. Thompson (Ascomycetes, Valsaceae) is widespread on Populus balsamifera in Canada from Quebec to British Columbia (1). The only United States records of this northerly fungus are from Vermont, Wisconsin, and Alaska (1,2). There are no records of this fungus on the Pacific Coast south of British Columbia, despite the presence of susceptible hosts (i.e., Populus trichocarpa and its hybrids). However, in September of 1997, the disease was observed in a hybrid poplar plantation at latitude 47.9°N and longitude 122.1°W near Snohomish, Washington. Blight affected the lower crown of trees in their second year of growth. Leaf lesions, with their characteristic black stromata, were easily distinguished from symptoms of other diseases. Some individual lesions of L. tetraspora affected entire leaf laminae, but there appeared to be little premature defoliation at the time of observation. Populus trichocarpa × P. deltoides hybrids were more commonly blighted than were P. trichocarpa × P. maximowiczii hybrids (i.e., 13/18 clones affected versus 4/11, respectively). A voucher specimen was deposited in the Herbarium at the Pacific Forestry Centre (DAVFP 25289).

References: (1) M. E. Barr. Mycol. Mem. No. 7:130, 1978. (2) D. F. Farr. et al. 1989. Fungi on Plants and Plant Products in the United States. American Phytopathological Society, St. Paul, MN.
First Report of Cassava Common Mosaic Potexvirus Infecting Chaya (Cnidoscolus chayamansa) in Tuvalu
Authors: Jones P. , Devonshire J. , Dabek A. , Howells C.
Published: May 2007

Chaya (Cnidoscolus chayamansa McVaugh) was introduced into Tu-valu as a leaf vegetable in the early 1990s (1) with the primary objective of alleviating vitamin A and C deficiencies, which at that time were prevalent throughout the population. Although there are no definitive quarantine records, we believe that the crop originated from vegetative cuttings introduced into Funafuti atoll from Kiribati. In the years following its introduction, chaya was distributed as cuttings taken from the original, introduced germplasm, to other islands and atolls of Tuvalu. The occurrence of yellow patches on the mature leaves of chaya cultivated in Funafuti had previously been attributed to iron deficiency, which was the inevitable consequence of growing the crop on coral atoll soils that are well known to be poor sources of metallic ions, notably iron, zinc, and copper. Following heavy cyclonic rains in March 1997, young, emerging chaya leaves were noted to exhibit an angular mosaic of the leaf lamina, characteristic of virus infections. Negatively stained sap from mosaic-affected leaves, when examined in the transmission electron microscope, was found to contain many rod-shaped virus particles similar in morphology to those of the Potexviridae (approximately 510 × 15 nm). The virus was transmitted mechanically to Chenopodium amaranticolor, in which it induced local lesion symptoms. The virus was found to be more closely related serologically to cassava common mosaic potexvirus (CsCMV) from Brazil than to that from Colombia, by immunosorbent electron microscopy with antisera kindly provided by F. Morales. Recently, CsCMV particles have been found in mosaic-affected chaya derived from the original Funafuti mother plants on Vaitupu Island. Similar symptoms have been observed on chaya being cultivated in Nui and Nanumaga islands. We conclude that CsCMV must now have been distributed throughout the atolls and islands of Tuvalu by infected planting material. We believe this to be the first report of the occurrence of CsCMV outside Central America and the first record of a plant virus from Tuvalu.

Reference: (1) C. Howells and M. Bainbridge. 1996. South Pacific Commission, Pacific Island Forests and Trees. Page 10.
Epidemiology of Tomato Spotted Wilt in Pepper and Tomato in Southern Georgia
Authors: Gitaitis R. D. , Dowler C. C. , Chalfant R. B.
Published: May 2007

The spatial distributions of symptomatic tomato and pepper plants infected with tomato spotted wilt virus (TSWV) were mapped over time in field studies in 1990 to 1992. Disease gradients occurred in some tomato transplant beds and pepper fields but were not observed in tomatoes grown to maturity. In 1990 and 1991, an increasing gradient emanated from the eastern edge of tomato transplant beds and led to adjacent tobacco plots containing TSWV-infected plants. In addition, gradients within each block emanating from the edge adjacent to fallow alleys were observed within the primary disease gradient in 1990. A gradient also occurred both down the row and across cultivars in a commercial pepper field in 1990. The gradient failed to flatten over time, a possible indication of lack of secondary disease spread. Tests for aggregation supported the contention that there was limited secondary spread within pepper fields and tomato plots and that most infections arose from primary transmission. Clipped plants from tomato transplant beds had no higher incidence of TSWV in grow-out tests than did nonclipped plants. Reduced yields were significantly correlated with time of first symptom expression in tomato, with plants that were symptomatic earlier in the season yielding less fruit per plant by weight.
Yield and Seed Quality of Soybean Cultivars Infected with Sclerotinia sclerotiorum
Authors: Hoffman D. D. , Hartman G. L. , Mueller D. S. , Leitz R. A. , Nickell C. D. , Pedersen W. L.
Published: May 2007

Sclerotinia stem rot (SSR) is one of the most important diseases of soybean in the United States. Five maturity group III cultivars, Asgrow A3304 STS (A3304), Pioneer Brand 9342 (P9342), Pioneer Brand 9381 (P9381), Probst, and Yale, grown in fields in east-central Illinois, were used to determine the relationship of SSR incidence to yield, 100-seed weight, seed protein and oil content, visual seed quality, and seed germination. In addition, the number of sclerotia in seed samples and the seedborne incidence of Sclerotinia sclerotiorum were determined. For each cultivar, at least 23 two-row plots, 3 m long, that represented a range of SSR incidence from low to high, were used to count the number of plants with and without SSR stem symptoms and were used to estimate yields and evaluate seed quality. Disease incidence ranged from 2 to 45% for Probst, 0 to 65% for P9381, 0 to 68% for P9342, 1 to 93% for Yale, and 0 to 95% for A3304. Regression of yields on SSR incidences for each cultivar was significant (P < 0.05); for every 10% increase in SSR incidence, yields were reduced by 147, 194, 203, 254, and 263 kg/ha for Probst, A3304, P9342, Yale, and P9381, respectively. Disease incidence was negatively correlated (P < 0.05) with seed germination for all cultivars but Probst, and to oil content and seed weight for P9381 and Yale. Disease incidence was positively correlated (P < 0.05) with seed quality for all cultivars and to the number of sclerotia in harvested seeds for P9342, P9381, and Probst. The seedborne incidence of S. sclerotiorum was 0.3, 0.3, 0.3, 0.4 and 0.7% in A3304, P9381, Yale, Probst, and P9342, respectively, and represents a significant potential for further spread of this pathogen and disease.
Efficacy of Various Fungal and Bacterial Biocontrol Organisms for Control of Fusarium Wilt of Tomato
Authors: Larkin Robert P. , Fravel Deborah R.
Published: May 2007

Numerous fungi and bacteria, including existing biocontrol strains with known activity against soilborne fungal pathogens as well as isolates collected from the roots and rhizosphere of tomato plants growing in the field, were tested for their efficacy in controlling Fusarium wilt of tomato. Tomato seedlings were treated with the potential biocontrol agents in the greenhouse and transplanted into pathogen-infested field soil. Organisms tested included nonpathogenic strains of Fusarium spp., Trichoderma spp., Gliocladium virens, Pseudomonas fluorescens, Burkholderia cepacia, and others. Specific nonpathogenic isolates of F. oxysporum and F. solani collected from a Fusarium wilt-suppressive soil were the most effective antagonists, providing significant and consistent disease control (50 to 80% reduction of disease incidence) in several repeated tests. These isolates also were equally effective in controlling Fusarium wilt diseases of other crops, including watermelon and muskmelon. Other organisms, including isolates of G. virens, T. hamatum, P. fluorescens, and B. cepacia, also significantly reduced Fusarium wilt compared to disease controls (30 to 65% reduction), but were not as consistently effective as the nonpathogenic Fusarium isolates. Commercially available biocontrol products containing G. virens and T. harzianum (SoilGard and RootShield, respectively) also effectively reduced disease (62 to 68% reduction) when granules were incorporated into potting medium at 0.2% (wt/vol). Several fungal and bacterial isolates collected from the roots and rhizosphere of tomato plants also significantly reduced Fusarium wilt of tomato, but were no more effective than other previously identified biocontrol strains. Combinations of antagonists, including multiple Fusarium isolates, Fusarium with bacteria, and Fusarium with other fungi, also reduced disease, but did not provide significantly better control than the nonpathogenic Fusarium antagonists alone.
Changes in the Racial Composition ofPhytophthora sojaein Australia Between 1979 and 1996
Authors: Ryley M. J. , Obst N. R. , Irwin J. A. G. , Drenth A.
Published: May 2007

Surveys of commercial soybean fields, disease nurseries, and trial plots of soybean were conducted throughout eastern Australia between 1979 and 1996, and 694 isolates of Phytophthora sojae were collected and classified into races. Fourteen races, 1, 2, 4, 10, 15, and 25, and eight new races, 46 to 53, were identified, but only races 1, 4, 15, 25, 46, and 53 were found in commercial fields. Races 1 and 15 were the only races found in commercial fields in the soybean-growing areas of Australia up until 1989, with race 1 being the dominant race. Race 4 was found in central New South Wales in 1989 on cultivars with the Rps1a gene, and it is now the dominant race in central and southern New South Wales. Races 46 and 53 have only been found once, in southern New South Wales, and race 25 was identified in the same region in 1994 on a cultivar with the Rps1k gene. Only races 1 and 15 have been found in the northern soybean-growing regions, with the latter dominating, which coincides with the widespread use of cultivars with the Rps2 gene. Changes in the race structure of the P. sojae population from commercial fields in Australia follow the deployment of specific resistance genes.
An Exobasidium Disease of Fruit and Leaves of Highbush Blueberry
Authors: Cline W. O.
Published: May 2007

Fruit of highbush blueberries (Vaccinum corymbosum L.) in southeastern North Carolina have been observed to suffer from sporadic outbreaks of distinct green spots on ripe fruit. Though edible, affected fruit are unsightly in market containers of fresh berries. In 1997, this disorder affected over 25% of the berries from a 5.7-ha field of the cv. Wolcott, rendering all fruit from this field unsaleable. In May 1998, the symptom was again observed in a planting of cv. Croatan. Samples were collected on the packing line from hand-harvested fruit and from the field. Sharply delineated green spots were observed on otherwise normal ripe fruit. The spots were 2 to 10 mm in diameter, circular or rarely irregular, not sunken or protruding, and often tinged with red. Affected tissues in ripe fruit extended 2 to 3 mm into the berry and were the texture and color of green, unripe fruit. Sparse white fungal growth was visible on the surface of some affected areas. In the field, spots were observed on fruit and leaves. Incidence was estimated at 5 and 1%, respectively. Spots on affected leaves were circular, 4 to 7 mm in diameter, light green, slightly thickened, and smooth on the upper surface; the underside was covered with dense white fungal growth. Microscopic examination of thinly sectioned berry and leaf tissue in water mounts revealed round basidia bearing 2 to 6 (most often 4) basidiospores (4.0 to 5.2 × 13 to 15 μm). Spores were consistent with descriptions of Exobasidium vaccinii (Fuckel) Woronin (1), being musiform to fusiform, slightly curved, and hyaline with a conspicuous hylar appendage, some with transverse septa. This is the first report of blueberry fruit infection by an Exobasidium species.

Reference: (1) F. L. Caruso and D. C. Ramsdell, eds. 1995. Compendium of Blueberry and Cranberry Diseases. American Phytopathological Society, St. Paul, MN.
Gliricidia Little Leaf Disease in Costa Rica
Authors: Kenyon L. , Harrison N. A. , Richardson P. A.
Published: May 2007

Gliricidia sepium is a multipurpose, legume tree species native to Central America and Mexico with wide social and economic importance. Gliricidia little leaf disease (GLLD) is associated with infection by a phytoplasma and is manifested by one or more symptoms, including leaflet yellowing, leaflet size reduction, shortened internodes, and shoot proliferation, often leading to branch die-back or death of young trees. Trees with symptoms were seen in fences and natural stands in the Nicoya Peninsular and on road sides west of San Jose, Costa Rica. Shoot samples were collected from eight symptom-bearing trees in different locations and from two healthy-looking trees in the southeast where no GLLD symptoms were observed. DNA from each sample was used as template in polymerase chain reaction (PCR) with universal phytoplasma rRNA gene primers P1 and P7 (1). DNA from a GLLD-infected tree from Honduras, and a pigeon pea witches'-broom infected Cajanus cajan from Florida, served as positive controls, while DNA from healthy G. sepium and C. cajan seedlings were used as negative controls. A 1.8-kb PCR product, indicative of presence of phytoplasma DNA, was amplified from all symptom-bearing tree samples and positive control DNAs, but not from DNA from the apparently healthy trees or seedlings. Restriction fragment length pattern analysis of PCR products with a range of endonucleases showed no difference between the Honduran and Costa Rican phytoplasma isolates. The distribution and symptom types observed in Costa Rica suggest that GLLD has recently arrived from Nicaragua and is spreading southeast.

Reference: (1) L. Kenyon et al. Plant Pathol. 47:671, 1998.
First Report of Bipolaris sorghicola on Johnsongrass in Argentina
Authors: Acciaresi H. , Mónaco C.
Published: May 2007

Target leaf spot was found on johnsongrass (Sorghum halepense (L.) Pers.) in La Plata, Argentina (34°54′S, 58°30′W). Up to 80% disease severity was observed in adult plants. In most diseased plants, spots were well defined, delimited by leaf veins, and elongated. Individual lesions ranged in size from small spots (2 to 3 mm) to large lesions (10 to 15 mm). Lesions sometimes coalesced to produce extensive areas of necrosis. Isolates identified as Bipolaris sorghicola (Lefebre & Scherwin) Alcorn (1) grew slowly on potato dextrose agar medium, producing a compact dark brown mycelium. Conidia were 40 to 80 μm long, slightly curved and golden brown, with three to seven pseudosepta. Although germination of conidia was mainly bipolar, lateral germination sometimes was observed. Twenty monoconidial isolates were inoculated at 105 conidia per cm3 on johnsongrass at the 4-leaf stage to confirm the pathogenicity of B. sorghicola. After inoculation, plants were placed in a high-humidity chamber for 24 h; thereafter, they were kept at 25°C day and 18°C night temperatures. Typical lesions developed after 10 days. The pathogen was reisolated from lesions after 15 days. Johnsongrass is one of the most noxious weeds in the world. Due to its potential as a biocontrol agent, further studies are needed to determine the effect of B. sorghicola on johnsongrass.

Reference: (1) J. L. Alcorn. Mycotaxon 27:1, 1983.
An Assessment of Nested PCR to Detect Phytoplasmas in Imported Dormant Buds and Internodal Tissues of Quarantined Tree Fruit Germ Plasm
Authors: Waterworth H. E. , Mock Ray
Published: May 2007

Nested polymerase chain reaction (PCR) assays were evaluated for use on a routine basis in a quarantine program to detect phytoplasmas in dormant fruit tree scionwood collected during the winter season. Phytoplasmas associated with peach yellow leaf roll, Western X, apricot chlorotic leaf roll, plum leptonecrosis, and apple proliferation diseases were detected in all known infected sources. Phytoplasmas in Prunus spp. were readily detected in both dormant bud and internodal tissues. Use of nested PCR versus a single primer pair resulted in electrophoresed PCR products that were easier to interpret. The nested PCR procedure has replaced 3-year tests with grafts on sensitive indicators to detect this group of pathogens.
First Report of Soilborne Rye Mosaic Virus in Rye in Denmark
Authors: Nielsen S. L. , Nicolaisen M. , Koenig R. , Huth W.
Published: May 2007

Soilborne wheat mosaic furovirus (SBWMV)-like particles were detected in rye (Secale cereale) grown in sandy soil in West Zealand during spring 1999. Infected plants showed yellow leaf mosaic and light stunting. Electron microscopy of negatively stained crude sap preparations revealed rigid rod-shaped particles with two average lengths, 296 and 162 nm; average diameter was 23 nm. Sap-inoculation to Chenopodium quinoa and C. amaranticolor produced local leaf lesions when grown at 17°C but none when grown at 22 to 25°C. All the features agree with the description of SBWMV (1). Immunosorbent electronmicroscopy with polyclonal antiserum produced by W. Huth to furovirus-like particles isolated from rye in Germany gave a distinct decoration to particles. Light microscopy of roots cleared with 10% KOH and stained with a 0.5% solution of trypan blue in lactoglycerol revealed resting spores with a morphology and size similar to Polymyxa graminis, a furovirus vector. This is the first record of a furovirus on cereals in Denmark. The complete nucleotide sequence of the isolate was analyzed and compared with data on isolates from wheat. Sequence identity was only 74%. Therefore, the isolate was designated as soilborne rye mosaic virus. SBRMV has been recorded previously in rye and triticale in several regions of Germany (2).

References: (1) M. K. Brakke. 1971. CMI/AAB Descr. Plant Viruses No. 77. (2) W. Huth. Nachrichtenbl. Dtsch. Pflanzenschutzdienstes 50:163, 1998.
Powdery Mildew Caused by an Oidium sp. on Twenty-One Annual Medicago spp. in California
Authors: Graves W. L. , Stuteville D. L. , Johnson R. C. , Greene S. L.
Published: May 2007

Powdery mildew was observed in plots of USDA Plant Introduction accessions of medic plants grown for seed increase at Riverside, CA, from 1995 to 1998. White, diffuse to dense, amphigenous mycelia bearing Oidium conidia appeared on shoots in April each year and remained active until the last plants matured in June. Invaded leaflets became necrotic and dropped prematurely, sometimes leaving a green petiole. However, mildew incidence was low in most plots, and symptomless plants occurred in all species. Conidia were ellipsoid-cylindrical and measured 15 to17 × 39 to 47 µm. A sexual state of the fungus was not observed. Morphological characteristics of the anamorph matched those of Erysiphe pisi (1). In growth chambers, conidia from medic plants caused severe mildew of garden pea (Pisum sativum L. ‘Early Perfection’). Powdery mildew occurred in plots of Medicago ciliaris, M. constricta, M. coronata, M. disciformis, M. doliata, M. granadensis, M. intertexta, M. italica, M. lesinsii, M. littoralis, M. lupulina, M. minima, M. murex, M. noeana, M. orbicularis, M. rigidula, M. rotata, M. rugosa, M. scutellata, M. truncatula, and M. turbinata. We believe this is the first report of naturally occurring powdery mildew on these species in the United States.

Reference: (1) H. J. Boesewinkel. Bot. Rev. 46:167, 1980.
A New Foliar Blight of Douglas-fir, Grand Fir, and Noble Fir Caused by a Binucleate Rhizoctonia-like Fungus
Authors: Putnam M. L.
Published: May 2007

The Oregon State University Plant Clinic received samples in 1996 and 1997 of Douglas-fir (Pseudotsuga menziesii) with web blight from Christmas tree plantations in Douglas, Lane, and Benton counties. Affected needles were 1 or more years old, uniformly brown, with no chlorosis or banding, and had a tendency to hang down from the branches and cling together, bound by mycelial webbing visible at ×10 magnification. In 1998, the disease was found on grand (Abies grandis) and noble (A. procera) firs in Christmas tree plantations as well as in native stands of Douglas-fir. Twigs of grand fir were killed, but not those of Douglas-fir. Brown needles may encompass half the side of a tree, destroying its value. This disease has been severe in Christmas tree plantations. A binucleate Rhizoctonia-like species has been consistently isolated from affected needles from all three tree species. The fungus has hyphae averaging 6.0 μm in diameter, with dolipore septa, slight constriction at the branch points, and acute to right angle branching. No sclerotia are formed, but monilioid cells develop after 2 weeks. Cell nucleation was determined with cotton blue or ethidium bromide. Koch's postulates were fulfilled by inoculating with an isolate obtained from grand fir onto 2-year-old Douglas-fir trees. Plugs (7 mm in diameter) of mycelium growing on potato dextrose agar plates were removed and placed onto the foliage of three trees. Plugs from uninoculated plates were used as a control on three additional trees. Inoculated trees were placed under mist on a greenhouse bench. Symptomatic needles were observed 5 weeks after inoculation. A fungus identical to the inoculum was obtained from symptomatic needles. No Rhizoctonia-like fungi were obtained from needles of the control plants. Further characterization of the fungus is underway. This new disease of Douglas-fir and true firs is potentially devastating, since Douglas-fir is a major component of managed timber forests in western Oregon, and the disease has been found at numerous sites in timber trees in the region.
Development of Polymerase Chain Reaction Primers Highly Specific for Xanthomonas albilineans, the Causal Bacterium of Sugarcane Leaf Scald Disease
Authors: Pan Y.-B. , Grisham M. P. , Burner D. M. , Legendre B. L. , Wei Q.
Published: May 2007

New primers were developed that greatly improved the specificity of the polymerase chain reaction (PCR) protocol for Xanthomonas albilineans, the causal agent of sugarcane leaf scald disease. Length-polymorphic PCR products, amplified under the current PCR protocol from the 16S-23S ribosomal DNA intergenic transcribed spacers (ITS) of X. albilineans and three unidentified sugarcane saprophytic bacterial species, were cloned and sequenced. Fourteen other nonredundant ITS sequences retrieved from the database were highly homologous to the sequence of X. albilineans. Two X. albilineans-specific PCR primers, namely, PGBL1 (5′ CTT TGG GTC TGT AGC TCA GG) and PGBL2 (5′ GCC TCA AGG TCA TAT TCA GC), were designed based on a multiple sequence alignment among these 18 sequences. These two primers permitted specific PCR amplification of a 288-bp DNA product from all 71 diverse X. albilineans strains tested. No amplification product was observed from any other bacterial species tested, including the three unidentified sugarcane saprophytes. The new PCR protocol has been routinely used to detect the leaf scald pathogen from infected sugarcane tissues.
First Report of East African Cassava Mosaic Begomovirus in Nigeria
Authors: Ogbe F. O. , Atiri G. I. , Robinson D. , Winter S. , Dixon A. G. O. , Quin F. M. , Thottappilly G.
Published: May 2007

Cassava (Manihot esculenta Crantz) is an important food crop in sub-Saharan Africa. One of the major production constraints is cassava mosaic disease caused by African cassava mosaic (ACMV) and East African cassava mosaic (EACMV) begomoviruses. ACMV is widespread in its distribution, occurring throughout West and Central Africa and in some eastern and southern African countries. In contrast, EACMV has been reported to occur mainly in more easterly areas, particularly in coastal Kenya and Tanzania, Malawi, and Madagascar. In 1997, a survey was conducted in Nigeria to determine the distribution of ACMV and its strains. Samples from 225 cassava plants showing mosaic symptoms were tested with ACMV monoclonal antibodies (MAbs) in triple antibody sandwich enzyme-linked immunosorbent assay (1). Three samples reacted strongly with MAbs that could detect both ACMV and EACMV. One of them did not react with ACMV-specific MAbs while the other two reacted weakly with such MAbs. With polymerase chain reaction (2), the presence of EACMV and a mixture of EACMV and ACMV in the respective samples was confirmed. These samples were collected from two villages: Ogbena in Kwara State and Akamkpa in Cross River State. Co-infection of some cassava varieties with ACMV and EACMV leads to severe symptoms. More importantly, a strain of mosaic geminivirus known as Uganda variant arose from recombination between the two viruses (2). This report provides evidence for the presence of EACMV in West Africa.

References: (1) J. E. Thomas et al. J. Gen. Virol. 67:2739, 1986. (2) X. Zhou et al. J. Gen. Virol. 78:2101, 1997.
Occurrence of Smut Caused by a Ustilago sp. on Dry-Beans
Authors: Costa J. L. da S. , de Oliveira V. C.
Published: May 2007

In September 1997, after the tropical winter season and following a long warm (28 to 33°C) and rainy (27 mm) period, smut symptoms were observed on two dry-bean (Phaseolus vulgaris) fields in Brazil. Brownish to blackish powdery masses of spores were observed on stems, pods, and roof green and senescent plants. No galls were observed. Hyphae in infected tissue were intercellular; no clamp connections were observed. Typical globose teliospores were observed that measured 7 to 11 μm. Spores were uninucleate or binucleate; predominantly brownish with flattened poles and equatorial band; the exospore wall was thick and surface ornamented (echinulate-type). Teliospores incubated in water drops generated transversely septate promycelia, unbranched, producing terminal and lateral basidiospores. The fungus did not grow well on potato dextrose agar (PDA) medium, generating yeastlike colonies. To confirm pathogenicity of a Ustilago sp., spores collected from field-infected plants were inoculated on 8- and 20-day old seedlings of dry-bean cultivars Rosinha and Perola. Spore suspensions of 105 teliospores were sprayed all over the plants. After inoculation, plants were kept in a moist chamber (relative humidity [RH] 100%) for 2 days. At the third day, inoculated plants were covered with clear polyethylene bags and transferred to the greenhouse (RH 50%, temperature 25 ± 2°C). Noninoculated controls were included for comparisons. Within 2 weeks, all inoculated plants reproduced field symptoms of darkened tissues covered by profuse sori containing teliospores and basidiospores. Eight-day-old plants died 2 weeks after inoculation. Noninoculated plants did not develop any symptoms. Teliospores obtained from dead plants were identical to those used for inoculation, thus completing Koch's postulates. Fischer (1), and later Fischer and Shaw (2), proposed a species concept for Ustilago based on morphology (primarily of the teliospore), symptomatology, and host specialization at the host-family level. Although the teliospores found on dry-beans, in Brazil, are much like those of Ustilago maydis, the fungus did not cause galls on plants, was able to infect roots and kill seedlings. and is very well adapted to a legume plant. Cross inoculation tests indicated that spores from dry-beans cannot cause disease symptoms on maize. We therefore regard the bean smut as a new species. We are not aware of any other Ustilago sp. being reported on a legume host.

References: (1) G. W. Fischer. 1953. Manual of the North America Smut Fungi. (2) G. W. Fischer and C. G. Shaw. Phytopathology 43:181, 1953.
First Report of Macrophomina phaseolina on Cotton (Gossypium hirsutum) in Georgia
Authors: Baird R. E. , Brock J. H.
Published: May 2007

In a field study evaluating the diversity and density of the soilborne mycobiota in a cotton (Gossypium hirsutum L.) production system, Macrophomina phaseolina (Tassi) Goidanich was isolated on potato dextrose agar from dark brown to black lesions on feeder and secondary roots. Multiple proliferations of feeder and secondary roots were also observed. Isolate RB 656 obtained from these lesions was tested for pathogenicity in the greenhouse by mixing 25 ml of 2-week-old cornmeal sand inoculum (3 g of cornmeal, 100 g of sand, and 20 ml of distilled water) with 5 liters of autoclaved soil (Leefield loamy sand, pH 6.2) per pot (40 × 200 cm). Control pots containing autoclaved soil alone were included for comparison. On 17 September, 10 cotton seeds of DPL 90 were sown per pot. Each treatment had five replications. Forty days after planting, plant heights from pots containing M. phaseolina were lower (14.8 cm) than those in the control pots (19.6 cm), but stand counts were similiar. On this date, four plants were left in each pot to allow the remaining seedlings to reach full maturity. On 9 December, the four plants per replicate pot were removed and roots evaluated for damage. Lesions similiar to those seen originally were observed on the secondary and feeder roots of the infested pots, and the characteristic proliferation of feeder and secondary roots was noted. Tap roots in pots containing M. phaseolina were smaller (11.6 cm) than in the control pots (18.6 cm). Isolate RB 656 was reisolated from the damaged roots in the treated pots. This is the first report of M. phaseolina on cotton in Georgia.
Quality Parameters in Small Grains from Minnesota Affected by Fusarium Head Blight
Authors: Jones R. K. , Mirocha C. J.
Published: May 2007

Recent epidemics of Fusarium head blight (FHB) severely damaged the hard red spring wheat and barley crops in Minnesota. Samples of commercial grain were analyzed in 1993 and 1994 to determine the effects of FHB on several quality parameters. Wheat test weight (TW) averaged 832 kg m-3 (55.4 lb/bu), thousand kernel weight (TKW) averaged 27.4 g, and the proportion of visually scabby kernels (VSK) averaged 11.0%. Deoxynivalenol (DON) was detected in 493 of 500 samples (98.6%). The mean concentration was 8.3 μg/g (range = 0.0 to 44.7 μg/g). Scab in wheat could rapidly be estimated using easy-to-prepare visual comparison standards. Scores of percent VSK were correlated with DON concentration at r = 0.897 and 0.908 in 1993 and 1994, respectively. TW and TKW were less effective estimators of DON (r = -0.622 and -0.550, respectively). DON was detected in 100 of 100 six-row barley samples collected during the survey and averaged 10.4 μg/g (range = 0.5 to 39.7 μg/g). DON concentration in barley could not be effectively estimated with grading parameters including TW, TKW, percent plump kernels, or a visual index of kernel discoloration. In 28 samples of oats, DON averaged 1.4 μg/g (range = 0.0 to 6.4 μg/g). Nivalenol was not detected in any of the 628 samples analyzed during the two-year study.
Pythium Species Associated with Root Dysfunction of Creeping Bentgrass in Maryland
Authors: Feng Yan , Dernoeden Peter H.
Published: May 2007

Putting green samples (n = 109) were inspected for the presence of Pythium oospores in roots of plants from golf courses (n = 39) in Maryland and adjacent states. Twenty-eight Pythium isolates were recovered from creeping bentgrass (Agrostis palustris) (n = 25) and annual bluegrass (Poa annua) (n = 3) plants. Most isolates associated with Pythium-induced root dysfunction were from greens less than 3 years of age and were obtained primarily between March and June, 1995 to 1997. Eight Pythium species (P. aristosporum, P. aphanidermatum, P. catenulatum, P. graminicola, P. torulosum, P. vanterpoolii, P. volutum, and P. ultimum var. ultimum) were isolated from creeping bentgrass and two species (P. graminicola and P. torulosum) were from annual bluegrass. All species, except P. catenulatum, were pathogenic to ‘Crenshaw’ creeping bentgrass seedlings in postemergence pathogenicity tests. P. aristosporum (n = 3) and P. aphanidermatum (n = 1) were highly aggressive at a low (18°C) and a high temperature (28°C). P. graminicola (n = 1) was low to moderately aggressive. P. torulosum (n = 12) was the most frequently isolated species, but most isolates were either nonpathogenic or caused very little disease. P. aristosporum (n = 3) and P. aphanidermatum (n = 1) were highly aggressive and were associated with rapid growth at 18 and 28°C on cornmeal agar. P. volutum (n = 1) was highly aggressive at 18°C, but was one of slowest growing isolates. Infected roots were generally symptomless, and the number of oospores observed in roots was not always a good indicator of disease or of the aggressiveness of an isolate. Large numbers of oospores of low or even nonpathogenic species may cause dysfunction of creeping bentgrass roots.
Occurrence of Dactylaria higginsii on Purple Nutsedge in Florida
Authors: Kadir J. B. , Charudattan R.
Published: May 2007

In September 1994, a population of severely diseased purple nutsedge (Cyperus rotundus L.) was found in Gainesville, FL. The symptoms were characterized by necrotic leaf spots, blotches, and foliar blighting. A fungal isolate was consistently recovered from symptomatic leaves and grown in pure culture. Based on the characteristics of conidia (28.6 × 6.6 μm) and conidiophores (45.2 × 7.0 μm at the broadest base), the fungus was identified as Dactylaria higginsii (Luttrell) M.B. Ellis. This fungus was first described as Piricularia [sic] higginsii from Georgia (4) and later redescribed as D. higginsii (2). A Pyricularia sp. and P. grisea (Cooke) Sacc. have been recorded on C. alternifolius L., C. papyrus L., and other Cyperus spp. from Florida, but species of Pyricularia or Dactylaria have not been reported from this state on purple nutsedge (1). Proof of pathogenicity (Koch's postulates) was established in repeated trials in a greenhouse; the disease symptoms were reproduced, and the fungus was reisolated from inoculated plants and confirmed to be the same organism used for inoculations. Four- to six-leaf-stage purple nutsedge and yellow nutsedge (C. esculentus L.) plants were sprayed with a suspension of 1 × 106 conidia per ml amended with 0.02% Silwet L-77 (vol/vol). Control plants were sprayed with 0.02% Silwet L-77 only. Small, water-soaked lesions developed 4 days after inoculation. The lesions coalesced into larger necrotic blotches with grayish centers 8 days after inoculation. Most of the inoculated foliage was blighted within 15 days after inoculation. The disease did not kill nutsedge bulbs or tubers, but reduced shoot and tuber yields. None of the control plants developed any symptoms. The ability of D. higginsii to cause severe disease and reduce the yields of vegetative organs indicates that it has potential as a biological control agent for purple nutsedge and yellow nutsedge, two of the world's worst weeds. This is the first record of occurrence of D. higginsii outside of its original distribution in Georgia (3).

References: (1) S. A. Alfieri, Jr., et al. 1994. Diseases and Disorders of Plants in Florida. Bull. No. 14. Division of Plant Industry, Gainesville, FL. (2) M. B. Ellis. 1976. More Dematiaceous Hyphomycetes. Commonwealth Mycological Institute, Kew, Surrey, England. (3) D. F. Farr et al. 1989. Fungi on Plants and Plant Products in the United States. American Phytopathological Society, St. Paul, MN. (4) E. S. Luttrell. Mycologia 46:810, 1954.
First Report of Soybean Dwarf Virus Infecting Lentil and Beet Western Yellows Virus Infecting Lentil and Chickpea Crops in Ethiopia
Authors: Tadesse N. , Ali K. , Gorfu D. , Abraham A. , Lencho A. , Ayalew M. , Yusuf A. , Makkouk K. M. , Kumari S. G.
Published: May 2007

A survey conducted during November 14–23, 1998, to identify viruses infecting chickpea (Cicer arietinum) and lentil (Lens culinaris) crops in the Shewa province of Ethiopia covered 33 chickpea and 32 lentil fields randomly selected. Identity of the viruses present and virus incidence were determined on the basis of laboratory testing of 100 to 200 randomly collected samples in addition to 15 to 20 symptomatic samples from each field. A total of 5,427 lentil and 3,836 chickpea samples were collected and tested for the presence of 12 different viruses by tissue blot immunoassay (1) at the Plant Pathology Laboratory in Debre Zeit Agriculture Research Center, Ethiopia. All antisera were virus specific, including those for beet western yellows virus (BWYV; ATCC PVAS-647) and soybean dwarf virus (SbDV; ATCC PVAS-650). More than 21% of the samples from 5 chickpea fields were infected; the most common virus was BWYV. Also, at least 21% of the samples from 11 lentil fields were virus positive; the most widespread virus was PSbMV. Highest rates of infection: of lentil in a single field, PSbMV in 58.5% of the samples; in a chickpea field, 41.3% of the samples positive for BWYV. Other viruses such as faba bean necrotic yellows nanovirus (FBNYV) and broad bean wilt fabavirus in chickpea and FBNYV, broad bean stain comovirus, bean yellow mosaic potyvirus, and cucumber mosaic cucumovirus in lentil were detected at very low incidence.

Reference: (1) K. M. Makkouk and A. Comeau. Eur. J. Plant Pathol. 100:71, 1994
Tilletia walkeri on Annual Ryegrass in Wheat Fields in the Southeastern United States
Authors: Cunfer Barry M. , Castlebury Lisa A.
Published: May 2007

Surveys for Tilletia walkeri on annual ryegrass (Lolium multiflorum) were conducted during 1997 and 1998 in the southeastern United States, where suspect teliospores of the Karnal bunt fungus, Tilletia indica, were found in USDA-APHIS surveys of wheat (Triticum aestivum) seed in 1996. T. walkeri is morphologically similar to T. indica. Annual ryegrass is a common weed in wheat fields in the southeastern United States. Between April and June 1997, ryegrass seed samples were collected from 190 fields of wheat in 47 counties in Georgia and from 26 fields in 17 counties in Alabama and south-central Tennessee. In 1998, 70 samples were collected from 40 counties in the same regions of the three states. The teliospores from these samples were 23 to 45 μm in diameter (average about 33 μm) and ranged from light brown to dark reddish brown. They had coarse, widely spaced cerebriform ridges on the surface and were surrounded by a gelatinous sheath. The ryegrass bunt was identified as the recently described species T. walkeri, occurring on ryegrass seed from Australia and Oregon. In 1997, teliospores of T. walkeri were found in 13 samples from eight counties in central Georgia and from one field in Tennessee. In 1998, more teliospores and bunted seeds were found, possibly due to frequent rain in the region throughout the flowering period for ryegrass. Teliospores were found in 26/70 of the samples, and among these, only a small number of bunted seed were found in 12 of 13/70 samples. In one wheat field in Morgan County, Georgia, about 50% of the ryegrass seed collected was partially bunted, and a small percentage was completely bunted. Fields with teliospores were widely distributed and generally matched the locations where teliospores were found in APHIS wheat seed surveys in 1996 to 1998. T. walkeri occurs at very low levels on ryegrass in the Southeast and is the source of teliospores, initially identified as those of T. indica, associated with wheat seed in APHIS surveys. No bunted wheat seeds or teliospores of T. indica were found in the survey.