bluuebunny/crossref_metadata_2025 huggingface dataset:
Melon Rugose Mosaic Virus: Characterization of an Isolate from Sudan and Seed Transmission in Melon
Authors: Mahgoub Hanan A. , Wipf-Scheibel Catherine , Delécolle Brigitte , Pitrat Michel , Dafalla Gasim , Lecoq Hervé
Published: May 2007

Melon rugose mosaic virus (MRMV) was isolated from snake cucumber (Cucumis melo var. flexuosus) in the Kassala region of Sudan in 1993. The host range of the virus was mostly limited to cucurbits, where it induced severe mosaic and leaf deformations. Cytopathological studies revealed severe chloroplast alterations, including vesicles at their periphery and the tendency to aggregate, which are typical of tymovirus infections, providing further evidence that MRMV is a tentative member of the genus Tymovirus. In melon and snake cucumber, MRMV was found to be seed transmitted at rates of 0.9 and 3.8%, respectively. Seed dissection experiments revealed that the virus could be detected in the seed coat, papery layer, and embryo. Seed disinfection treatments did not reduce seed transmission rates, which suggests an internal transmission. A preliminary screening for resistance in melon revealed some resistance in two out of 367 accessions tested.
An Assessment of Fungicide Benefits for the Control of Fungal Diseases of Processing Tomatoes in New York and New Jersey
Authors: Dillard H. R. , Johnston S. A. , Cobb A. C. , Hamilton G. H.
Published: May 2007

Concurrent studies on the benefits of fungicide use for control of fungal diseases of processing tomatoes were conducted in New York and New Jersey in 1993 and 1994. Fungicides (chlorothalonil at 2.5 kg/ha or mancozeb at 1.68 kg/ha) were applied at 7-, 10-, or 14-day intervals to processing tomatoes for control of anthracnose caused by Colletotrichum coccodes, early blight caused by Alternaria solani, and Septoria leaf spot caused by Septoria lycopersici. The New Jersey trial included an additional treatment using the disease-warning system TOM-CAST. All fungicide treatments significantly reduced foliar disease severity (in New York) and anthracnose incidence (New York and New Jersey) in the 2 years of study. Yield of usable fruit was significantly increased by all fungicide treatments with the exception of the TOM-CAST treatment using the cultivar Brigade in 1994 in New Jersey. In New York, usable yield and financial benefit were consistently the highest in plots treated with chlorothalonil on a 7-day interval. In New Jersey, the highest usable yields and the greatest financial benefits occurred in the chlorothalonil 7- and 10-day interval treatments in 1993. At both locations, the yield and financial benefit associated with the fungicide treatments was primarily due to suppression of anthracnose and other fruit rots. Suppression of foliar diseases was less important.
First Report of Potato Powdery Scab, Caused by Spongospora subterranea f. sp. subterranea, in North Dakota
Authors: Draper M. A. , Secor G. A. , Gudmestad N. C.
Published: May 2007

Powdery scab is a serious disease of potatoes (Solanum tuberosum L.) that can cause extensive surface defects on susceptible potato cultivars. The pathogen, Spongospora subterranea (Wallr.) Lagerh. f. sp. subterranea J. A. Tomlinson, is an important concern in seed potato production because current seed certification standards in North Dakota have a zero tolerance for this pathogen. Powdery scab had not previously been identified in North Dakota. Until recently this disease was not thought to be present in U.S. commercial potato-producing areas. Powdery scab has now been shown to be more widely distributed than previously thought (1), having been identified in several locations in eastern and western North America. However, environmental conditions in North Dakota, including high soil pH, low rainfall, and high temperatures, are not considered favorable for powdery scab development. Diseased potatoes were found in a field from Griggs County, ND, in the fall of 1994 and characteristic cystosori were present in erumpent lesions on infected tubers. The field was an irrigated circle planted to three different cultivars. The cultivars Goldrush and Red Norland were symptomless, while cv. Red La-Soda was severely affected. Up to 30% of the tuber surfaces were diseased and disease incidence approached 25%. The infected crop was destroyed. Pathogenicity was confirmed by planting pieces of diseased tuber tissue adjacent to healthy seed pieces of Russet Burbank. Transmission of the obligate parasite occurred naturally by simulating conditions that were favorable for infection, acidic potting mix (Jiffy-Mix) maintained at a high water potential. Progeny plants were found to be infected on both tubers and roots after 60 days. Control plants that were not exposed to diseased tuber pieces were unaffected. North Dakota, a major seed-potato-producing state, ships seed to every other potato-producing area in the U.S. and much of Canada. Infected seed shipped to areas with a favorable environment for disease development may result in crops becoming diseased and unmarketable. The cooler temperatures and higher than normal rainfall during the 1992 to 1995 seasons may account for powdery scab development in North Dakota. Recent increases in irrigated agriculture and potato production in North Dakota could lead to the infestation of new areas, restricting the value of that land for potato production.

Reference: (1) B. Christ et al. Am. Potato J. 65:583, 1988.
First Report of Potato Tuber Necrotic Ringspot Disease Caused by PVYNTN in Portugal
Authors: Serra M. C. , Weidemann H. L.
Published: May 2007

During the last 2 years, potato (Solanum tuberosum L.) tubers displaying superficial necrotic arcs and rings were found in central Portugal. These symptoms increased during storage, and diminished tuber quality of ware (fresh-market) potatoes; however, no internal necrosis, which is typical for infections caused by tobacco rattle virus or potato mop top virus, was observed. The symptoms led to the preliminary diagnosis of potato tuber ringspot disease (PTNRD), caused by a tuber necrosis (TN)-inducing isolate of the tobacco veinal necrosis strain group of potato virus Y (PVYN) that was named PVYNTN. The occurrence of PVYNTN has been reported by a number of European countries. Suspect PTNRD tubers of the cv. Monalisa were obtained from several Portuguese potato growers and were tested with polyclonal antibodies (pabs) that reacted generally with PVY, and with monoclonal antibodies (mabs) raised against PVYN. Serogical tests were carried out in a double antibody sandwich (DAS) enzyme-linked immunosorbent assay (ELISA) with pabs and in a triple antibody sandwich (TAS) ELISA when mabs were used. As a result, the tubers were found to be infected with a virus isolate belonging to the PVYN strain group. Since PVYNTN cannot be distinguished serologically from other members of the PVYN strain group due to the similarities of their coat proteins (1), reverse transcription-polymerase chain reaction combined with immunocapture was applied for diagnostic purposes. The olignucleotide primers used were located in the 5′ non-coding region at nucleotide 103 and in the adjacent P1 protein gene coding region at position 919. This primer pair can be used to distinguish PVYNTN from other members of the PVYN strain group (2). Tests were carried out with plant sap from tubers and from plants grown from eye-cuttings and also from tobacco plants that were inoculated with plant sap of these potato tubers and plants. Control samples included sap from un-infected tobacco plants and from tobacco plants infected with a PVYN isolate and with the PVYNTN type strain “Hungary”. The expected amplification product of 835 bp appeared in the agarose gel with samples originally obtained from the tubers and with the PVYNTN control but not with the PVYNTN control, indicating that the tuber symptoms in potato cv. Monalisa were caused by infections with PVYNTN. This is the first report of the occurrence of PVYNTN in Portugal.

References: (1) T. Dalmay and E. Balazs. Nucleic Acids Res. 18: 6721, 1990. (2) H. L. Weidemann and E. Maiss. Z. Pflanzenkr. Pflanzenschutz 103:337, 1996.
Occurrence and Distribution of Soybean Sudden Death Syndrome in Iowa
Authors: Yang X. B. , Lundeen P.
Published: May 2007

Soybean sudden death syndrome (SDS), caused by blue-pigmented, slow-growing strains of Fusarium solani, is a disease recently reported in Iowa. In 1994 and 1995 the geographic distribution and status of the disease was determined at the state, local, and field levels. An east-to-west decreasing trend of SDS prevalence was found at the state level. No SDS was found in the western part of Iowa. The disease was found in commercial production fields in 4 Iowa crop reporting districts — central, north-central, east-central, and southeastern — with the greatest severity and the most frequent occurrence of SDS found in the east-central district. In two counties along the Mississippi River, disease prevalence was high; more than 50% of soybean fields had SDS in locations where surveys were conducted. Intensive surveys on a local scale were conducted in areas around the fields where the disease was first noticed. In areas where disease prevalence was low, all detected infested fields belonged to the same owners. In areas where disease prevalence was high, no such pattern was found. Disease incidence varied from field to field. Information on SDS occurrence at different geographic scales serves as baseline information to monitor the future development of the disease in Iowa.
Multiple Inoculation with Three Attenuated Viruses for the Control of Cucumber Virus Disease
Authors: Kosaka Y. , Fukunishi T.
Published: May 2007

Multiple inoculation of cucumber seedlings with attenuated isolates of cucumber mosaic virus (CMV), zucchini yellow mosaic virus (ZYMV), and watermelon mosaic virus 2 (WMV-2) somewhat reduced yield loss due to mixed infection by virulent strains of these viruses in field experiments under severe epidemic conditions in 1994 and 1995. In addition, this protective inoculation largely protected grafted cucumber plants from viral wilt syndrome. In greenhouse experiments, no significant differences were observed between single and multiple inoculations in the cross-protection effects of the attenuated viruses against their respective virulent strains. Triply inoculated plants developed synergistic yellow leaf mosaic symptoms and 15% fewer marketable fruits compared with healthy plants. Thus, multiple inoculation is appropriate for the summer-early autumn production, when economic losses due to the concurrent incidence of CMV, WMV-2, and ZYMV are significantly greater than the loss in yield due to the inoculation.
Control of Colletotrichum acutatum in Strawberry Under Laboratory, Greenhouse, and Field Conditions
Authors: Freeman S. , Nizani Y. , Dotan S. , Even S. , Sando T.
Published: May 2007

Various fungicides and a heat treatment were assessed for their ability to control strawberry anthracnose caused by the fungus Colletotrichum acutatum under laboratory, greenhouse, and field conditions. The effective dose causing 50% inhibition of mycelial growth (ED50) was 30.5, 12.2, 0.2, 0.15, 0.05, 0.07, and 0.05 μg/ml for the fungicides folpet, captan, propiconazole, difenoconazole, combined prochloraz-Zn/folpet, prochloraz-Zn, and prochloraz-Mn, respectively. In laboratory experiments, infection in segments of strawberry runners treated with pro-chloraz-Zn reached 60%, which was significantly reduced as compared to combined prochloraz-Zn/folpet (90%), captan, folpet, and water controls (100%). In the greenhouse, numbers of naturally infected transplants killed were significantly reduced by all fungicides and the heat treatment (5 min at 49°C) as compared to the non-treated control. Prochloraz-Zn was the most effective chemical control treatment but did not differ significantly from the heat treatment. In field experiments conducted during 1995 and 1996, numbers of naturally infected strawberry transplants killed were significantly reduced by all fungicide treatments relative to the non-treated control. Percent reduction of transplant mortality in the field was 93.3, 93.1, 66.7, 37.7, and 29.1 for prochloraz-Mn, prochloraz-Zn, combined prochloraz-Zn/folpet, propiconazole, and difenoconazole, respectively.
Potential Use of Benomyl for Control of Ergot (Claviceps africana) in Sorghum A-lines in Zimbabwe
Authors: Frederickson D. E. , Leuschner K.
Published: May 2007

In the absence of a successful practice for the control of ergot on sorghum A-lines (male-steriles) in Zimbabwe, two fungicides, Benlate and Thiram, were tested in greenhouse and field experiments. Fungicides were either applied to sorghum panicles singly, at concentrations of 0.1 or 0.2% a.i., or combined in mixtures at 0.1% a.i. each. Fungicides were applied before inoculation at heading or stigma exsertion, or after disease became visible. Treatment with either Benlate or Thiram was ineffective if applied when disease first became visible. A significant reduction in initial disease severity, rate of disease increase, and final disease severity was achieved with one application of Benlate at 0.2% a.i. at heading or stigma exsertion. At the concentrations tested Benlate and Thiram did not reduce seed-set in R- (restorer) lines.
Complete Resistance by Carnation Cultivars to Fusarium Wilt Induced by Fusarium oxysporum f. sp. dianthi Race 2
Authors: Ben-Yephet Y. , Reuven M. , Shtienberg D.
Published: May 2007

The response of two carnation (Dianthus caryophyllus) cultivars, Arbel and Scarlette, to Fusarium wilt induced by Fusarium oxysporum f. sp. dianthi race 2 was determined in experiments conducted in an infested field and using artificially inoculated plants grown in a net-house. In six field experiments conducted from 1989-90 to 1995-96, and including more than 200 different cultivars, Arbel and Scarlette were the only ones that remained symptomless. The responses of the other cultivars varied markedly, but even those known to be highly resistant, Eveline and Novada, were frequently diseased. In the net-house tests, Arbel and Scarlette were compared with cultivars that ranged in their response to Fusarium wilt from highly resistant to highly susceptible. Due to the conducive conditions for Fusarium wilt prevailing in these tests, disease progressed rapidly, and by the end of the experiments all cultivars except Arbel and Scarlette were severely diseased (incidence of 81.2 to 100%); Arbel and Scarlette remained symptomless. The pathogen did colonize the basal stem parts of all cultivars, including Arbel and Scarlette. The number of colony-forming units (CFU) recovered from the basal stem parts was 105 CFU/g of stem in the other cultivars, 103 CFU/g in Scarlette, and 50 CFU/g in Arbel. Results of our study suggest that Arbel and Scarlette exhibit a novel type of resistance to Fusarium wilt induced by F. oxysporum f. sp. dianthi race 2.
A Comparison Between Serological and Biological Assays in Detecting Grapevine Leafroll Associated Viruses
Authors: Rowhani Adib , Uyemoto Jerry K. , Golino Deborah A.
Published: May 2007

The efficacy of the serological procedure enzyme-linked immunosorbent assay (ELISA) for detecting grapevine leafroll associated viruses (GLRaV types -1, -2, -3, and -4) was compared with indexing on Vitis vinifera L. cv. Cabernet Franc. Results of the biological assays confirmed the infectious nature of all grapevine sources testing positive by ELISA for GLRaV-1 (9 sources), GLRaV-2 (14 sources), and GLRaV-4 (14 sources), and the noninfectious nature of ELISA-negative grapevines (75 sources). However, among 57 sources testing positive by ELISA for GLRaV-3, or 24 sources with multiple infections, 8 and 1 sources, respectively, were negative by Cabernet Franc assays. Serological assays were repeated on all graft-inoculated indicators and only symptomatic ones reacted positively. Also, the 8 original GLRaV-3 sources that had tested positive by ELISA and negative by bioassay were found positive using immuno-capture/reverse transcription-polymerase chain reaction (IC/RT-PCR). The single multiple-infected source was not available for retesting. The distribution of GLRaV in infected grapevines was tested by assaying 20 to 40 samples per source of 36 plants infected with GLRaV-1, -2, -3, or -4. The incidence of GLRaV-positive canes as determined by ELISA ranged from 0 to 100%, suggesting that GLRaV can be unevenly distributed in chronically infected grapevines.
Validation of a Commercial System for Remote Estimation of Wetness Duration
Authors: Gleason Mark L. , Parker Sharon K. , Pitblado Ron E. , Latin Richard X. , Speranzini Donna , Hazzard Ruth V. , Maletta Martha J. , Cowgill Winfred P. , Biederstedt Darvin L.
Published: May 2007

To assess the accuracy of remote, real-time mathematical simulations of wetness duration and air temperature, hourly measurements of wetness duration and air temperature at 18 sites in the United States and Canada from May to September 1995 were compared with simulations for these sites provided by SkyBit, Inc. SkyBit simulations of mean, maximum, and minimum daily air temperatures varied from on-site measurements by less than 0.7°C but underestimated the duration of wet periods by an average of 3.4 h/day. At five of six stations tested, SkyBit underestimates of wetness duration were significantly (P < 0.01) larger on days when no rain was measured than on rainy days, indicating that simulations of dew-period duration were much less accurate than simulations of rain-period duration. The vast majority of hours SkyBit misclassified as dry occurred either when entire wet periods were missed (59.3%) or when the onset of a wet period was detected late (28.4%). The results suggest that revision of SkyBit wetness-simulation models should focus on reducing error rates during dew events. In simulations using two disease-warning models, TOM-CAST and Melcast, with mean values of measured and SkyBit-simulated wetness duration, SkyBit-simulated values resulted in fewer and later fungicide spray advisories than did measured values. The magnitude of these impacts varied with the magnitude of the simulation errors and with differences in the models' decision rules.
First Report of Bean Common Mosaic Necrosis Potyvirus (BCMNV) Infecting Common Bean in California
Authors: Guzman P. , Rojas M. R. , Davis R. M. , Kimble K. , Stewart R. , Sundstrom F. J. , Gilbertson R. L.
Published: May 2007

During the 1996 growing season (June to September) an outbreak of bean common mosaic was detected in a navy bean field (cv. Snow Bunting) in Colusa County, CA. Early field inspections (August 1996) revealed an incidence of 5 to 10% infection, whereas a late field inspection (September) showed an incidence of 70 to 90% infection. Enzyme-linked immunosorbent assay (ELISA) was performed on 18 leaf samples from symptomatic plants collected from this field with two monoclonal antibodies (Mab): Mab I-2, which detects bean common mosaic necrosis virus (BCMNV) strains (previously necrotic or serotype A bean common mosaic potyvirus [BCMV] strains), and Mab 197, which detects BCMV strains (previously non-necrotic or serotype B BCMV strains) and BCMNV (3). ELISA results indicated BCMNV infection in all 18 samples. In order to confirm ELISA results and to further characterize the viral isolate(s), primary leaves of the differential bean cvs. Black Turtle Soup (BTS) T-39, Topcrop, Amanda, and Sutter Pink were inoculated mechanically with sap prepared from the same leaves used for ELISA. Within 1 week, BTS T-39 and Topcrop plants showed necrotic spots on inoculated leaves and systemic necrosis and death (black root rot symptoms), Sutter Pink showed typical systemic mosaic symptoms, and Amanda showed necrotic spots and restricted vein necrosis on inoculated leaves. These reactions were consistent with infection by the NL-3 strain of BCMNV (1). Reverse transcriptase-polymerase chain reaction was used to amplify a portion of the genome of the virus that contains the 3′ end of the coat protein (CP) gene and the 3′ untranslated region (UTR). A DNA fragment of approximately 670 bp was amplified and DNA sequence analysis revealed that the nucleotide sequences of the 3′ end of the CP and the UTR region of the California BCMNV isolate were 98 and 94% similar to those of the Michigan isolate of the BCMNV NL-3 strain (2), respectively. Together, these results suggest that the outbreak of bean common mosaic in the cv. Snow Bunting navy beans was caused by a pathogroup VI BCMNV isolate, and DNA sequence information suggests that it is similar to the NL-3 strain of BCMNV. This is the first report of BCMNV in California.

References: (1) E. Drijfhout et al. Neth. J. Plant Pathol. 84:13, 1978. (2) G. F. Fang et al. Virus Res. 39:13, 1995. (3) G. I. Mink et al. Arch. Virol. S:397, 1992.
First Report from Morocco of Phytophthora infestans Isolates with Metalaxyl Resistance
Authors: Sedegui M. , Carroll R. B. , Morehart A. L. , Arifi A. , Lakhdar R.
Published: May 2007

Late blight of potato (Solanum tuberosum L.) caused by Phytophthora infestans (Mont.) de Bary first appeared in Africa in 1941. It has been observed sporadically in Morocco for decades but only recently became a major problem. Significant losses have been recorded in the last two growing seasons in spite of the use of various disease control programs that included combinations of systemic and protectant fungicides. Phytophthora infestans was cultured from diseased foliage collected from commercial potato fields near Larache, Morocco. Isolates were analyzed to determine pathogenicity on several potato and tomato cultivars, mating type, genotype at two allozyme loci (2), and relative sensitivity to metalaxyl. Responses of the isolates to metalaxyl were assayed by mycelial radial growth on metalaxyl-amended agar, by floating leaves inoculated with P. infestans on metalaxyl solutions, and via potato tuber disks placed on filter paper saturated with metalaxyl solutions (1). Koch's postulates were completed; all isolates were pathogenic to potato and tomato cultivars tested, are consistent with the A1 mating type, and have the same allozyme pattern (Gpi 100/100, Pep 92/100) as US-6 genotype. All tests indicated resistance to metalaxyl up to 250 ppm.

References: (1) K. L. Deahl et al. Am. Potato J. 70:779, 1993. (2) S. B. Goodwin et al. Plant Dis. 79:1181, 1995.
First Report of Rhizoctonia solani AG-7 in Georgia
Authors: Baird R. E. , Carling D. E.
Published: May 2007

During a study to determine the pathogenic fungi overwintering on dead cotton (Gossypium hirsutum L.) roots, two isolates of Rhizoctonia solani Kühn anastomosis group 7 (AG-7) were identified. Isolate #213 was obtained from dead roots near Tifton, GA, and isolate #219 was cultured from cotton roots near Midville, GA. Rhizoctonia solani AG-7 was previously reported in Arkansas, Indiana, and Asia (1). Isolates #213 and #219 were tested in the greenhouse for pathogenicity 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) into 20 × 100 cm pots containing 2.25 liters of sterile soil (Tifton loamy sand, pH 6.1) per pot. Pots with noninfested soil were included as a control. Eight seeds of cotton (Delta and Pineland 90 DPL 90) were sown per pot. Each pot was a replicate and each treatment was replicated five times. At 20 days after planting, plant stands in soil infested with isolate #213 or #219 averaged 2 to 3 or 4 to 5 plants per pot, respectively, while stands in noninfested soil averaged 7 to 8 plants per pot. Brownish colored, sunken lesions were observed on roots, hypocotyles, and cotyledons of plants from pots infested with R. solani AG-7. Isolates #213 and #219 were reisolated from plants grown in their respective treatments. This is the first report of R. solani AG-7 in Georgia.

Reference: (1) R. E. Baird et al. Plant Dis. 80:1421, 1996.
Effect of Intermittent Warming and Modified Atmosphere Packaging on Fungal Growth in Peaches
Authors: Fernández-Trujillo J. P. , Salmerón M. C. , Artés F.
Published: May 2007

Firm-breaker peaches (Prunus persica cv. Paraguayo), treated with 0.25 g liter-1iprodione, were inoculated with 106spores per ml of Alternaria tenuis and stored for up to 3 weeks at 0.5°C. Three intermittent warming (IW) cycles of 1 day at 20°C every 6 days at 0.5°C and modified atmosphere packaging (MAP) were applied. Fungicide treatment was ineffective in controlling growth of A. tenuis and Cladosporium spp. during storage. MAP prevented the growth of both fungal genera. IW alone or combined with fungicide seemed to increase total CFU counts and did not control decay (mainly due to exacerbated Cladosporium spp. development). CFU counts and losses through fungal attack were only occasionally significantly correlated.
Host Range of Streptomycete Strains Causing Common Scab
Authors: Goyer Claudia , Beaulieu Carole
Published: May 2007

Ten Streptomyces isolates from common scab lesions on carrots (Daucus carota) were characterized. Morphological and physiological characterization of the carrot isolates established that they were closely related to S. scabies. DNA-DNA hybridization studies were carried out between DNA from the carrot isolates and DNA from two potato strains belonging to the two genetic clusters of S. scabies. Most of the carrot isolates exhibited a high level of DNA relatedness (average of 90%) to strain EF-54, which belongs to genetic cluster 1 of S. scabies. Three carrot isolates could not be included in either S. scabies genetic cluster 1 or 2. The pathogenicity of six S. scabies isolates from potato or carrot, two isolates of S. caviscabies, and one isolate of S. acidiscabies was determined on potato, carrot, radish, beet, turnip, and parsnip. All S. scabies isolates were pathogenic on carrot and radish, but pathogenicity on beet, parsnip, turnip, and potato was variable. Even though S. acidiscabies and S. caviscabies until now have been isolated only from potato, we demonstrated that isolates of these species also could infect other crops, such as radish, carrot, parsnip, and turnip.
Rapid Evaluation of Pathogenicity in Pseudomonas syringae pv. syringae with a Lilac Tissue Culture Bioassay and Syringomycin DNA Probes
Authors: Scheck Heather J. , Canfield Marilyn L. , Pscheidt Jay W. , Moore Larry W.
Published: May 2007

Losses from diseases caused by Pseudomonas syringae pv. syringae occur on a large number of deciduous woody plants in commercial nurseries in the Pacific Northwest. Bioassays for pathogenicity are one step in the identification of P. syringae pv. syringae and are usually performed on the host of isolation; however, woody plants can take months to develop symptoms. A bioassay with highly susceptible lilac (Syringa vulgaris ‘Sensation’) tissue culture plantlets evaluated pathogenicity in strains of P. syringae pv. syringae isolated from 25 species of deciduous woody plants. DNA colony hybridization with the syrB probe for a syringomycin synthetase gene and the syrD probe for a syringomycin export gene was also evaluated as a method for identifying pathogens. Of 552 strains provisionally identified as P. syringae pv. syringae, 59% were pathogenic in the bioassay and hybridized with the syr probes, while 19% were non-pathogenic and did not hybridize with the syr probes, giving 78% agreement between the two methods. Nine percent of strains were pathogenic in the bioassay but did not hybridize with the syr probes, and 13% were not pathogenic in the bioassay but did hybridize with the syr probes. These methods detected pathogenic strains of P. syringae pv. syringae isolated from diverse woody plants in 5 to 16 days.
Brown Stem Rot Resistance in Soybean Germ Plasm from Central China
Authors: Bachman M. S. , Nickell C. D. , Stephens P. A. , Nickell A. D.
Published: May 2007

Soybean accessions from China were screened in an attempt to identify unique sources of resistance to Phialophora gregata, the cause of brown stem rot. In 1994, over 500 accessions from the USDA Soybean Germplasm Collection, University of Illinois, Urbana-Champaign, were evaluated in the field at Urbana, IL, for reaction to brown stem rot. The accessions originated from nine provinces in central China and ranged in maturity from groups II to IV. Disease assessment was based on incidence of foliar symptoms and severity of stem symptoms produced by infection with natural inoculum. Based on field results, 64 putatively resistant lines were selected and evaluated in the greenhouse by a root-dip inoculation method. Thirteen accessions with levels of resistance equal to those of resistant standards were identified from five provinces. These lines may have value as donors of unique sources of resistance to brown stem rot.
Molecular Evidence for the Presence of Maize Bushy Stunt Phytoplasma in Corn in Brazil
Authors: Bedendo I. P. , Davis R. E. , Dally E. L.
Published: May 2007

Previously, electron microscopy revealed that the corn (Zea mays L.) disease characterized by stunting and leaf reddening and commonly known as “red stunt” in Brazil is associated with plant infection by an unidentified phytoplasma (formerly mycoplasmalike organism) (1). During recent years, corn production in Brazil has been seriously affected by the increasing prevalence of a disease exhibiting symptoms similar to those of “red stunt.” The present investigation was initiated to determine the possible association of a phytoplasma with the current disease problem and to attain definitive molecular identification of any associated phytoplasma. To detect the possible presence of a phytoplasma in diseased corn in Brazil, plants exhibiting symptoms of stunting and leaf reddening in the field in 1995 and 1996 were assayed for the presence of phytoplasma DNA sequences by the use of polymerase chain reactions (PCR). We used primer pairs R16mF2/R16mR1 and R16F2n/R16R2 in nested PCRs (2) to prime phytoplasma-universal amplification of 16S ribosomal (r) DNA. Oligonucleotide pair rpF1/rpR1 (3) was used to prime phytoplasma-universal amplification of ribosomal protein (rp) gene operon sequences. Phytoplasma identification was accomplished by restriction fragment length polymorphism (RFLP) analysis of amplified 16S rDNA and rp gene operon sequences. Primer pair MBS-F1/MBS-R1 (4) was used to prime amplification of a maize bushy stunt (MBS)-specific chromosomal DNA sequence. Preparation of template DNAs, PCR conditions, and RFLP analyses of PCR products were as previously described (2–4). DNA amplification was observed in all PCRs containing template DNAs derived from symptomatic plants, indicating phytoplasmal infection of corn in Brazil. No DNA amplification was observed in PCR containing template DNA from healthy control corn plants. Polymorphisms in amplified 16S rDNA were those characteristic of phytoplasmas classified in 16S rRNA gene group 16SrI, subgroup I-B, of which MBS phytoplasma is a member (3). Collective RFLP patterns of amplified rp gene operon sequences were similar or identical to those observed in parallel tests for a known reference strain of MBS phytoplasma, indicating that the Brazilian corn plants were infected by MBS phytoplasma. Amplification of MBS-characteristic DNA was observed in PCRs containing MBS-specific primer pair MBS-F1/MBS-R1 and DNA from diseased corn, confirming infection of the plants by MBS phytoplasma. This work provides the first firm evidence for association of maize bushy stunt phytoplasma with the current disease problem of corn in Brazil.

References: (1) A. S. Costa et al. Rev. Soc. Bras. Fitopatol. Piracicaba 4:39, 1971. (2) D. E. Gundersen and I.-M. Lee. Phytopathol. Mediterr. 35: 144,1996. (3) D. E. Gundersen et al. Int. J. Syst. Bacteriol. 46:64, 1996. (4) N. A. Harrison et al. Plant Dis. 80:263, 1996.
First Report of Anthracnose on Weeping Willow in Greece
Authors: Tzavella-Klonari K. , Aggelaki M. D. , Karadimos D. A.
Published: May 2007

A serious disease of weeping willow (Salix babylonica) trees in home and public gardens was observed in the Chalkidiki region (northern Greece) during the spring of 1995 and 1996. Purplish-brown or black, small necrotic spots appeared on the leaves and often on leaf veins. Leaves became distorted and fell. Small, light, sunken cankers with dark brown rim and paler center, elongated in shape, appeared on the young shoots and on the leaf petioles. Severely affected shoots lost their weeping habit on which the tree's ornamental value is based. Whitish acervuli covered the leaf spots and the cankers. Masses of conidia emerged from the acervuli under high relative humidity conditions. The conidia were hyaline, clavate to pyriform, two-celled (unequally), measuring 14 to 19 × 4 to 7 μm, and belonged to the fungus Marssonina salicicola (Bres.) Magnus (1), which is the anamorph of the ascomycete Drepanopeziza sphaeroides (Pers.) Hohnel, the cause of anthracnose of weeping willow. The outbreak of the disease can be attributed to the rainy weather (70.5 and 105.5 mm of rain occurred in spring 1995 and spring 1996, respectively) and temperatures of 20°C. The disease is known to cause serious damage in some European countries, Canada, Egypt, Argentina, and New Zealand. This is the first report of the disease in Greece.

Reference: (1) I. Vegh and J. Velastegui. Cryptogam. Mycol. 4:345, 1983.
First Report of Sclerotium rolfsii on Sunflower in Italy
Authors: Infantino A. , Di Giambattista G. , Socciarelli S.
Published: May 2007

During June 1996, 1-month-old sunflower plants (Helianthus annuus. L.) of the cvs. Blue Mix and Romsun × 590, grown at the experimental farm of the Istituto Sperimentale per la Nutrizione delle Piante (Montelibretti, Rome), showed symptoms of wilting, and then gradually dried out. Discolored areas were observed on the crown, where whitish, fan-shaped mycelia were occasionally present. A fungus was isolated on potato dextrose agar from surface-disinfested, diseased stem fragments. It also developed from diseased stem segments incubated in moist chambers. In both cases, round sclerotia developed after 9 days at room temperature. The fungus was identified as Sclerotium rolfsii Sacc. The fungus has been deposited in the ISPaVe collection (no. ER 883). To test pathogenicity, 20-day-old sunflower seedlings of the cvs. Blue Mix and Romsun × 590 were grown singly in an autoclaved peat/soil mixture in 20-cm-diameter plastic pots in a greenhouse at 30 ± 3°C. Plants were inoculated by placing five sclerotia of isolate ER 883 near the crown of each plant about 5 mm below the soil surface. For each cultivar, 10 plants were inoculated and 10 were left uninoculated. Wilting symptoms and stem discoloration appeared after 12 days. Sclerotia were produced at the stem base of some inoculated plants. All inoculated plants died after 20 days. S. rolfsii was consistently reisolated from all the inoculated plants, while no symptoms or signs were observed on the uninoculated plants. This is the first report of S. rolfsii on sunflower in Italy and has important implications for the use of sunflower in crop rotation. An unusual rainy period delayed planting of sunflowers by 1 month in 1996 and this could have favored the disease.
First Report of Aristastoma Leaf Spot on Desert Rose
Authors: McMillan R. T. , Graves W. R. , Leahy R. M.
Published: May 2007

In the spring of 1995, a species of Aristastoma was isolated from foliar lesions of Adenium obesum that originated in a commercial nursery in Dade County, FL, where 100% of the crop was affected. Plant foliage had irregular, oval to circular, rusty brown, necrotic lesions 5 to 15 mm in diameter. Large leaf spots developed tan centers. An undescribed species of Aristastoma was isolated consistently from symptomatic plant material. The identity of the fungus was confirmed by the International Mycological Institute, Egham, England. Both in vivo and in vitro, the fungus has immersed mycelium, pale brown to hyaline, branched and septate. Pycnidia are 160 to 300 μm in diameter with prominent setae 75 to 125 μm surrounding the ostiole, with hyaline, 1 septate, conidia that are 25 to 30 × 3 to 4 μm. Pathogenicity was tested on shadehouse-grown, 8-month-old desert rose plants by spraying plants with a conidial suspension containing 104 conidia per ml. Inoculated plants developed foliar symptoms within 5 to 10 days that were consistent with those originally observed on the diseased plant samples. The pathogen was isolated from symptomatic tissue of inoculated plants. Species of Aristastoma are reported to cause foliar symptoms mostly on leguminous crops, and in Florida Aristastoma oeconomicum causes lesions on Vigna. This is the first report of this or any species of Aristastoma on Adenium obesum or any other member of the Apocynaceae.
Application of RT-PCR for Indexing Avocado Sunblotch Viroid
Authors: Schnell R. J. , Kuhn D. N. , Ronning C. M. , Harkins D.
Published: May 2007

A method for the routine detection of avocado sunblotch viroid (ASBVd) in nucleic acid extracts of infected avocado tissues by reverse transcription-polymerase chain reaction (RT-PCR) was developed using ASBVd-specific primers. Amplified cDNA products were analyzed by electrophoresis on nondenaturing 6% polyacrylamide slab gels. The size of the major RT-PCR product from ASBVd-infected tissue was estimated to be 250 bp. This product was absent from amplified extracts of uninfected tissue. The amplification product from ASBVd was sequenced by the dideoxynucleotide chain termination method, and the sequence was over 97% identical to the published sequence. The RT-PCR assay is sensitive enough to allow viroid detection without requiring large amounts of tissue, highly purified ASBVd, or molecular hybridization.
Evaluation and Identification of Basil Germ Plasm for Resistance to Fusarium oxysporum f. sp. basilicum
Authors: Reuveni Reuven , Dudai Nativ , Putievsky Eli , Elmer W. H. , Wick R. L.
Published: May 2007

Growth chamber evaluation of several cultivars of basil and related herbs examined in the United States revealed that identical cultivars from different sources did not differ in their reactions to artificial inoculation with Fusarium oxysporum f. sp. basilicum. Cultivars differed in susceptibility to the pathogen: “Spicy globe” miniature was the most susceptible, and lemon basil (Ocimum basilicum var. citriodorum), Origanum majorana, and Thymus vulgaris were rated as not susceptible. Twenty isolates of F. oxysporum, originating from stems of diseased basil plants in Israel, were pathogenic on basil in growth chamber and greenhouse tests. Under artificial inoculation, 2 isolates of F. oxysporum f. sp. basilicum from stems were pathogenic to basil but not to 9 species representing Lamiaceae, Cucurbitaceae, Solanaceae, and Compositae indicating the specificity of the pathogen to basil. These isolates were used for additional resistance tests. Ocimum basilicum var. purpurascens (Exotic) and var. citriodorum were rated as not susceptible to the pathogen under artificial inoculation. Resistant germ plasm was identified in several basil plants of a local variety originally introduced from the United States and reselected at Newe Ya'ar. Seeds were planted in the greenhouse in naturally highly infested soil. Symptomless plants that survived in naturally infested soil were the source for F1 seeds of resistant germ plasm, which was confirmed by artificial inoculations with both isolates of the pathogen. Further selection tests to improve resistance were conducted up to the F4 generation in infested soil in the greenhouse. All individuals of the present genetic line remained symptomless, while all individual plants of the original susceptible cultivar defoliated 3 weeks after planting into infested soil, suggesting that the resistance may be a single, dominant gene. The causal organism was reisolated only from the susceptible plants and not from the symptomless resistant plants through all the experiments.
Natural Infection of Eggplant by Puccinia substriata var. indica in the United States
Authors: Wilson J. P. , Williamson W.
Published: May 2007

Eggplant (Solanum melongena) and other Solanum spp. are aecial hosts for Puccinia substriata var. indica, the rust pathogen of pearl millet (Pennisetum glaucum) (2). Although long suspected to be important in epidemic initiation (1), natural infection of eggplant has never been documented in the United States. All previous observations have been the result of deliberate inoculations. Eggplant (cv. Santana) seedlings with sporulating aecia were identified in the inventory of a vegetable transplant producer near Ty Ty, GA, on 22 April 1997. Flats of seedlings were being grown in a greenhouse with adjustable sides for creating an open-air environment for temperature control. Disease incidence was approximately 1.5% in the lot of 10,000 seedlings. Lesions were found most frequently on the first true leaf or less frequently on cotyledons. Aeciospores from 15 arbitrarily selected leaves were used to inoculate pearl millet seedlings in the greenhouse. Each leaf was used to inoculate pearl millet cultivars with no known resistance, and with the Rr1 resistance gene. Infection was obtained on all cultivars with no resistance genes, verifying pathogen identification. Fourteen isolates infected pearl millet with Rr1, revealing that virulence to Rr1 was common in this sample. The nearest point source of exposed pearl millet debris that could serve as a source of basidiospores was located approximately 9.7 km away from the eggplant.

References: (1) H. D. Wells. Plant Dis. Rep. 62:469, 1978. (2) J. P. Wilson et al. Plant Dis. 80:806, 1996.
First Report of Rice Blast Caused by Pyricularia grisea in California
Authors: Greer C. A. , Scardaci S. C. , Webster R. K.
Published: May 2007

Rice blast, caused by Pyricularia grisea (Cooke) Sacc., generally recognized as the most important disease of rice (Oryzae sativa L.) worldwide, was first found in the Sacramento Valley of California in 1996. Symptoms observed in commercial fields during September and October consisted mainly of darkened lesions at the panicle neck node and flag leaf collar. Many of the panicles with neck rot were partially filled or blank. Disease foci were irregular within fields and the most severely affected areas had approximately 50% of the panicle necks with symptoms. Initial identification of P. grisea was made by isolating the fungus from panicle neck nodes and leaf collars on potato dextrose agar. Subsequent identifications were made by placing symptomatic panicle neck nodes or leaf collars on moist filter paper in petri dishes to allow sporulation of the fungus. P. grisea was consistently recovered from these tissues and was identified by conidial morphology. A survey of over 500 rice fields in five Sacramento Valley counties was conducted in September and October 1996. Rice blast was confirmed in 33 commercial fields, which are spread over an area of approximately 460 km2 in Glenn County (27 fields) and northern Colusa County (6 fields). No blast was found in Butte, Sutter, or Yolo counties. P. grisea was recovered from cvs. M-201, M-202, M-204, M-103, M-401, S-102, L-204, and Calmochi-101 and several proprietary lines. To confirm pathogenicity of P. grisea, cv. M-201 was inoculated in the greenhouse 28 days after seeding with a suspension of 20,000 conidia per ml of sterile deionized water, covered with plastic bags for 2 days, and evaluated 7 days later. P. grisea isolates from cvs. M-201, M-202, and M-204 produced typical leaf and collar blast symptoms on inoculated plants, whereas control plants remained asymptomatic. P. grisea was consistently recovered from lesions on inoculated plants. No rice cultivars currently grown in California are known to have resistance to blast.
First Report of a Leaf Blight, Seed Stalk Rot, and Bulb Decay of Onion by Pantoea ananas in Georgia
Authors: Gitaitis R. D. , Gay J. D.
Published: May 2007

In May 1997, sweet onions (Allium cepa L.) grown in Toombs County, GA, displayed symptoms of blighted leaves, bleached and rotted seed stalks, and rotted bulbs. Gram-negative bacteria were isolated from infected tissues on nutrient agar and shown to be from the genus Pantoea on the basis of cell morphology (rod-shaped), yellow pigmentation, utilization of glucose in an oxidative and fermentative manner, presence of catalase, and absence of oxidase. These characteristics are typical of bacterial strains belonging to the Enterobacteriaceae (facultative anaerobes). Initially, these bacteria were thought to be P. agglomerans, a common saprophyte associated with plant material. However, fatty acid analysis, using bacterial identification software (MIDI, Dewark, DE), identified (second choice) some strains as possibly being P. ananas.. Further testing indicated that all strains utilized cellobiose, melibiose, inositol, glycerol, and sucrose, but not pectin, starch, or gelatin. However, those strains identified by fatty acid analysis as P. ananas were differentiated from P. agglomerans on the basis of indole production, lack of phenylalanine deaminase, and lack of nitrate reductase. To confirm pathogenicity, three strains of each species (total of six strains) were grown overnight in nutrient broth shake cultures. Bacterial cells were harvested by centrifugation and suspended in 0.01 M phosphate-buffered saline (0.85%). Inoculum was adjusted to approximately 5 × 108 CFU/ml with a spectrophotometer and misted with a chromatography sprayer onto onion leaves of approximately 10-week-old onion plants in the greenhouse. Onions were predisposed by placing them under plastic bags for 18 h prior to inoculation. Inoculated plants were left covered with plastic bags for an additional 24 h after inoculation. There were two plants per pot, each test had three pots, and the test was conducted twice. The three strains of P. agglomerans and buffer control resulted in no symptoms. The three strains of P. ananas produced severe blighting, rapid collapse of tissues, and rapid drying so that leaves were light tan and dry within 3 days. Disease on plants infected with P. ananas continued to develop until death of all foliage and bulbs shriveled and collapsed. Results were consistent for all replications and both trials. Bacteria recovered from diseased tissues were gram-negative, yellow, and facultative anaerobic, and produced indole but not phenylalanine deaminase or nitrate reductase; i.e., the bacteria demonstrated the same characteristics as P. ananas. Although P. agglomerans has been reported to produce similar symptoms in South Africa (1), our P. agglomerans strains were nonpathogenic. To our knowledge this is the first report of P. ananas causing a disease of onion.

Reference: (1) M. J. Hattingh and D. F. Walters Plant Dis. 65:615, 1981.