bluuebunny/crossref_metadata_2025 huggingface dataset:
Take-All Root Rot of St. Augustinegrass: First Report in Mississippi
Authors: Tomaso-Peterson M. , Trevathan L. E. , Gonzalez M. S.
Published: May 2007

Take-all root rot has been reported as a destructive disease of St. Augustinegrass home lawns in Florida and Alabama (1). In June 1998 and 1999, St. Augustinegrass home lawns in central Mississippi developed chlorotic, thinning patches ranging from 0.5 to 4.5 m in diameter. By August of each summer, plants within affected patches were necrotic and dead. Roots of affected St. Augustinegrass were necrotic and shorter than those of unaffected plants; nodes on stolons were necrotic, and lesions developed on internodes. Ectotrophic runner hyphae and dark brown, lobed hyphopodia were visible on roots and aboveground plant parts, respectively. Symptomatic tissues collected from St. Augustinegrass home lawns were plated onto potato dextrose agar (PDA); the incitant of take-all root rot, Gaeumannomyces graminis(Sacc.) Arx & Olivier var. graminis, was isolated. Verification of G. graminis var. graminis was based on colony morphology and taxonomic identification consistent with the description by Walker (2). G. graminis var. graminis isolated from symptomatic St. Augustinegrass was grown on sterile tall fescue seed and incorporated into sterile sand/peat moss mix. Asymptomatic St. Augustinegrass sprigs were washed, and roots were removed prior to planting in infested and noninfested soil. Plants were cultured in the greenhouse for 60 days. St. Augustinegrass planted into noninfested soil was asymptomatic while plants collected from G. graminis var. graminis-infested soil were symptomatic for take-all root rot. Crowns and roots of affected plants were necrotic; leaves were chlorotic and necrotic. Both runner hyphae and lobed hyphopodia were visible. G. graminis var. graminis was reisolated from symptomatic tissues and confirmed as the incitant of take-all root rot. This is the first report of take-all root rot of St. Augustinegrass in Mississippi.

References: (1) M. Elliott. Plant Dis. 77:206, 1993. (2) J. Walker. Trans. Br. Mycol. Soc. 58:427, 1972.
Pumpkin Fruit Rot in North Carolina Caused by Phytophthora nicotianae
Authors: Holmes G. J.
Published: May 2007

In 1999, during an evaluation of pumpkin (Cucurbita pepo) fruit for susceptibility to naturally occurring postharvest diseases, a soft rot of unknown etiology was noted. No fungal growth or sporulation was seen on the fruit surface and no root or crown rot was observed in the field. When fruit were cross-sectioned, masses of white, floccose mycelium covering large sections of the seed cavity were observed. Rot was observed in 21 fruit (6.4% of the total). The fungus was isolated from symptomatic fruit on a modified P10ARPH agar medium, semi-selective for Phytophthora spp. (2). Isolates from eight fruit formed papillate, ovoid sporangia, abundant chlamydospores, and colonies characteristic of P. nicotianae (1). No oospores were produced. Four sound pumpkin fruit (cv. Early Autumn) were inoculated with four isolates (one isolate per fruit). Each isolate was recovered from a different fruit. Pumpkins were surface sterilized at the point of inoculation by wetting with 70% ethanol. Inoculation was done by removing a small amount of mycelium from pure culture using a sterile, wooden toothpick and inserting it 2 cm deep into opposite sides of the mid section of sound fruit (two inoculations per fruit). Control fruit were punctured with sterile toothpicks (once per fruit). First symptoms appeared 4 days after inoculation at room temperature (22 to 24°C). Symptoms consisted of circular, water-soaked areas originating from the point of inoculation. Average diameter (based on four measurements on two fruit) of the water-soaked lesions were 3 cm at first appearance (i.e., 4 days) and 11 cm 10 days after inoculation. No symptoms developed on controls. When symptomatic fruit were cross-sectioned, masses of white, floccose mycelium were noted. Reisolation of this mycelium onto selective medium yielded P. nicotianae, thus fulfilling Koch's postulates. This is the first report of P. nicotianae causing fruit rot of pumpkins.

References: (1) D. C. Erwin and O. K. Ribeiro. 1996. Phytophthora Diseases Worldwide. The American Phytopathological Society, St. Paul, MN. (2) H. D. Shew. Phytopathology 77:1090, 1987.
First Report of Impatiens necrotic spot virus in the Czech Republic
Authors: Mertelik J. , Mokra V. , Gotzova B. , Gabrielova S.
Published: May 2007

Impatiens necrotic spot virus (INSV) was found for the first time in the Czech Republic in 1999 in Columnea sp. and Curcuma sp. plants that were imported. They were grown in a garden among other ornamental crops. By June 2000, INSV was detected in 17 ornamental plant species in several gardening establishments never having received imported plants. Frankliniella occidentalis thrips were present at the sites of INSV infection. Natural INSV infection was found also in Stellaria media, which is an important weed species in our conditions. INSV was identified by enzyme-linked immunosorbent assay using polyclonal antibodies to INSV from Loewe Biochemica, Germany, and from Bioreba, Switzerland. The virus was transmitted in sap to Nicotiana benthamiana and Datura stramonium (1). Virus particles typical of a tospovirus were detected by electron microscopy. INSV is the second tospovirus member occurring in the Czech Republic. Tomato spotted wilt virus (TSWV) has occurred in this country since 1992 (2) and to date has been detected in more than 100 plant species including ornamentals, vegetables, and weeds. TSWV became a serious problem in glasshouse grown crops. From the epidemiological point of view the situation of INSV dissemination seems to be similar to that of TSWV.

References: (1) M. Daughtrey et al. Plant Dis. 81:1220, 1997. (2) J. Mertelik and V. Mokra. Acta Virol. 42:348, 1998.
First Record of Barley yellow striate mosaic virus, Barley stripe mosaic virus, and Wheat dwarf virus Infecting Cereal Crops in Tunisia
Authors: Najar A. , Makkouk K. M. , Kumari S. G.
Published: May 2007

A survey conducted during April 2000 to identify viruses infecting cereal crops in different regions (Beja, Bizerte, Cap-bon, Jendouba, Kairouan, Siliana, and Zaghouan) of Tunisia covered 15 barley, 21 durum wheat, and 7 bread wheat randomly selected fields. Virus incidences were determined on the basis of laboratory testing of 100 to 200 randomly collected samples from each field. A total of 5,227 random (1,654 barley, 2,546 durum wheat, and 1,027 bread wheat) and 1,430 symptomatic (451 barley, 746 durum wheat, and 233 bread wheat) samples were collected. Samples were tested for the presence of five different viruses by tissueblot immunoassay (TBIA) (1) at the Virology Laboratory of INRAT. Antisera used were for Barley stripe mosaic virus (2), Barley yellow dwarf virus (PAV serotype) (2), Wheat streak mosaic virus (3), Barley yellow striate mosaic virus (BYSMV) provided by E. Luisoni, IFA, Turino, Italy (4), and Wheat dwarf virus (WDV) provided by J. Vacke, Research Institute of Crop Production, Prague, Chech Republic. BYDVPAV was detected in seven barley (from three fields), 25 durum wheat (10 fields), and eight bread wheat (three fields) samples from all except the Siliana region. BYSMV was detected in three barley (three fields), 16 durum wheat (six fields), and four bread wheat (three fields) samples from the Beja, Bizerte, Cap-bon, Jendouba, and Siliana regions. WDV was detected in five barley (three fields), nine durum wheat (four fields), and four bread wheat (one field) samples from the Beja, Cap-bon, and Bizerte regions. BSMV was detected in 49 barley (six fields) and 25 durum wheat (five fields) samples from the Beja, Bizerte, Cap-bon, Kairouan, and Zaghouan regions. This is the first record of BYSMV, BSMV, and WDV infecting cereal crops in Tunisia, but their incidence in fields was less than 1%. However, BSMV incidence was 10.5% in one barley field from the Cap-bon region. Virus incidence in symptomatic plants was a bit higher and ranged from 0.8% for WDV in bread wheat to 6% for BSMV in barley.

References: (1) K. M. Makkouk and A. Comeau. Eur. J. Plant Pathol. 100:71, 1994. (2) K. M. Makkouk and S. G. Kumari. Rachis Newsl. 12(1/2):24, 1993. (3) K. M. Makkouk and S. G. Kumari. Rachis Newsl. 16(1/2):74, 1997. (4) R. G. Milne et al. Intervirology 25:83, 1986.
First Record of Faba bean necrotic yellows virus and Beet western yellows virus Infecting Faba Bean in Tunisia
Authors: Najar Asma , Makkouk Khaled M. , Kumari Safaa G.
Published: May 2007

A survey was conducted in April 2000 to identify viruses infecting faba bean (Vicia faba L.) in seven regions (Beja, Bizerte, Cap-bon, Jendouba, Kairouan, Siliana, and Zaghouan) of Tunisia. Around 4,000 random samples were collected from 34 fields (100 to 200 samples per field). Samples were tested by tissue-blot immunoassay procedure (2) at the Virology Laboratory of INRAT for the presence of 14 different viruses. All antisera used were specific, including those for Faba bean necrotic yellows virus (FBNYV) (1) and Beet western yellows virus (BWYV) (ATCC-PVAS-647). Broad bean mottle, a beetle-transmitted and seedborne virus, was the most abundant with an average incidence of 2.3%. The highest disease incidence occurred with BWYV, which was in 20 and FBNYV in 4 of 98 random samples from a field in the Siliana region; and with BWYV in 7 and BBMV in 21 of 120 samples from a field in the Jendouba region. Other viruses such as broad bean stain, cucumber mosaic, and bean leaf roll were detected rarely (<1%). This is the first record of FBNYV and BWYV infecting faba bean in Tunisia. BWYV was detected in 1.2% of the samples tested collected from 20 fields comprising all seven regions. FBNYV was detected in 0.9% of the samples tested collected from 13 fields comprising all except the Capbon region.

References: (1) A. Franz et al. Ann. Appl. Biol. 128:255, 1996. (2) K. M. Makkouk and A. Comeau. Eur. J. Plant Pathol. 100:71, 1994.
A New Geminivirus Associated with a Yellow Leaf Curl Disease of Pepper in Thailand
Authors: Samretwanich K. , Chiemsombat P. , Kittipakorn K. , Ikegami M.
Published: May 2007

Pepper (Capsicum anuum) plants affected with yellow leaf curl disease were observed at Kanchanaburi in central Thailand in 1995. Three naturally infected pepper plants showing yellow leaf curl were collected and virus cultures maintained in pepper plants. Transmission experiments were carried out with the whitefly vector (Bemisia tabaci Genn.). Acquisition and inoculation threshold periods were 1 h and 30 min, respectively. The latent period was 10 h. Symptoms in cultured plants were the same as those observed in field plants. DNA was extracted from these cultured plants and amplified using polymerase chain reaction (PCR) with geminivirus-specific degenerate primers (1). A PCR product of 2.7 kbp was amplified and cloned. Three independent clones were sequenced and analyzed, and an identical 32-base stem loop region and the unique sequence (TGGGGTC) of putative Rep binding site were found in the intergenic region (IR). The B component could not be detected. The nucleotide sequence of the coat protein gene was compared with 28 well-studied whitefly-transmitted geminiviruses. Our geminivirus showed the highest sequence similarity (85%) with Tomato leaf curl virus from Taiwan (TwToLCV: GeneBank accession number U88692), suggesting that it is a new geminivirus. Therefore, it is designated Pepper yellow leaf curl virus.

Reference: (1) M. R. Rojas et al. Plant Dis. 77: 340, 1993.
Detection of Gaeumannomyces graminis Varieties Using Polymerase Chain Reaction with Variety-Specific Primers
Authors: Fouly H. M. , Wilkinson H. T.
Published: May 2007

The polymerase chain reaction (PCR) was used for detection of Gaeumannomyces graminis, the causal agent of take-all disease in wheat, oats, and turfgrass. NS5 and NS6 universal primers amplified the middle region of 18S ribosomal DNA of Gaeumannomyces species and varieties. Primers GGT-RP (5′ TGCAATGGCTTCGTGAA 3′) and GGA-RP (5′ TTTGTGTGTGAC CATAC 3′) were developed by sequence analysis of cloned NS5-NS6 fragments. The primer pair NS5:GGT-RP amplified a single 410-bp fragment from isolates of G. graminis var. tritici, a single 300-bp fragment from isolates of G. graminis var. avenae, and no amplification products from isolates of G. graminis var. graminis or other species of Gaeumannomyces. The primer pair NS5:GGA-RP amplified a single 400-bp fragment from isolates of varieties tritici and avenae. Two sets of primer pairs (NS5:GGT-RP and NS5:GGA-RP) were used in PCR reactions to detect and identify the varieties tritici and avenae either colonizing wheat, oats, or grass roots, or in culture. No amplification products were observed using DNA extracted from plants infected with eight other soilborne fungal pathogens or from uninoculated plants.
Identification ofWheat streak mosaic virusand Its VectorAceria tosichellain Mexico
Authors: Sánchez-Sánchez H. , Henry M. , Cárdenas-Soriano E. , Alvizo-Villasana H. F.
Published: May 2007

The objective of this study was to identify a pathogen observed in wheat in the Texcoco area (Mexico). The symptoms induced by this pathogen are consistent with those caused by a virus. Identification was based on host range, symptoms, mode of transmission, and on serological and morphological characterization. The pathogen was mechanically transmitted to Triticum aestivum, T. durum, Secale cereale, × Triticosecale, Avena sativa, and Hordeum vulgare. The virus particles were flexuous rods, 700 nm long that produced cylindrical inclusions seen as pinwheel inclusions under the electron microscope. The pathogen reacted with Wheat streak mosaic virus (WSMV) antibodies in enzyme-linked immunosorbent assay. An eriophyoid mite associated with this virus was identified as Aceria tosichella and found to transmit the virus efficiently. Based on its characteristics, the pathogen was identified as WSMV. During this study, the virus appeared sporadically in test plots without causing significant yield losses.
Distribution, Pathogenicity, and Interactions of Two Strains of Rice yellow mottle virus in Forested and Savanna Zones of West Africa
Authors: N'Guessan P. , Pinel A. , Sy A. A. , Ghesquière A. , Fargette D.
Published: May 2007

In Côte d'Ivoire, the S2 strain of Rice yellow mottle virus (RYMV) predominated in the forested zones, including the “rice belt” to the west, in each of the cropping systems where rice was grown. The S1 strain occurred more frequently in the northern Guinean savanna, and only S1 isolates were found further north in the Sahelo-Soudanian zones. In mixed infection, S2 dominated over S1 both in viral capsid and RNA contents under temperature regimes encompassing those observed in savanna and forested zones of Côte d'Ivoire. There was no evidence of interactions in virus accumulation between the West African strains S1 or S2 with the more distantly related East African strain S4. Field trials emphasized the impact of RYMV, which induced yield losses of 40 to 60% in several widely grown cultivars of Oryza sativa indica and O. sativa japonica. We report the high resistance of the O. indica cv. Gigante under field conditions which was apparent with all the S1 and S2 isolates tested. Responses to RYMV infection of several cultivars were isolate dependent. With most differential cultivars, responses were not strain specific, with the exception of the O. japonica cv. Idsa6, in which the S2 isolates always induced higher yield losses than the S1 isolates.
Quantitative Response of Cucumis melo Inoculated with Root Rot Pathogens
Authors: Biernacki M. , Bruton B. D.
Published: May 2007

This experiment quantified the effects of three root rot pathogens on muskmelon (Cucumis melo L., var. cantalupensis) growth traits using computerized image analysis. Plants were grown from seed in sand infested with the soilborne pathogen Monosporascus cannonballus, Acremonium cucurbitacearum, or Rhizopycnis vagum. After 28 days in the growth chamber, images of plants were analyzed to quantify their response. Compared to noninoculated muskmelons, inoculated plants had significantly increased mean root diameter (45%), decreased root length (26%, primarily in roots of <0.5 mm diameter), decreased number of root tips (27%), decreased rhizosphere volume (40%), and decreased cumulative and mean surface area of leaves (24%). Effects of M. cannonballus on muskmelon growth were significantly different compared to A. cucurbitacearum and R. vagum. Isolate effects manifested a greater magnitude of difference on muskmelon traits than those observed at the species level. Multivariate analyses of plant responses were more powerful than univariate analyses to differentiate among effects of pathogen species and pathogen isolates. Discriminant analysis were useful to identify groups of plant traits modified by each fungal species or isolate at low disease levels. Digital image analyses proved to be a useful technique in quantitative assessment of plant damage caused by soilborne root rot pathogens.
Mixed Virus Infections of Garlic Determined by a Multivalent Polyclonal Antiserum and Virus Effects on Disease Symptoms
Authors: Takaichi Miyuki , Nagakubo Takayuki , Oeda Kenji
Published: May 2007

A garlic virus-specific polyclonal antiserum was developed against a mixture of flexuous rodshaped virus particles isolated from mosaic-diseased garlic plants (15). This antiserum was used in Western blot analysis against tissues from mosaic-diseased garlic plants, at least seven viral coat protein (CP) bands (from 38 to 32 kDa) were identified. Using Western blot analysis with Potyvirus-specific antibodies and reverse transcription-polymerase chain reaction (RT-PCR) analysis, we concluded that three of the seven bands corresponded to CPs of Leek yellow stripe virus (LYSV) (38 kDa) and two different Onion yellow dwarf virus (OYDV) strains (35.5 or 34 kDa). The 35 kDa band corresponded to the CP of GV1-Carlavirus, and the other four bands, 36, 35 (not GV1), 33, and 32 kDa, were identified as the CPs of four mite-borne viruses, based on RT-PCR analysis. Based on the molecular weights of CP, mixed infections of Potyvirus, Carlavirus, and mite-borne viruses were characterized. LYSV causes apparent disease symptoms in garlic plants, however, little reduction in bulb weights. Conversely, garlic plants infected with three different mite-borne viruses expressed weak symptoms and yield losses. Mixed infections of OYDV, the mite-borne viruses, and LYSV caused severe disease symptoms and considerable reduction of bulb weights.
Molecular Characterization and Classification of Phytoplasmas Associated with Canola Yellows and a New Phytoplasma Strain Associated with Dandelions
Authors: Wang Keri , Hiruki Chuji
Published: May 2007

DNA isolated from symptomatic canola (Brassica napus, Brassica rapa) and dandelion (Taraxacum officinale) was used to amplify 16S ribosomal DNA fragments by polymerase chain reaction using two pairs of universal primers P1/P6 and R16F2n/R2. Restriction fragment length polymorphism (RFLP) analysis of the amplified DNA fragments using endonucleases AluI, HhaI, HpaII, MseI, RsaI, and Sau 3AI revealed two distinct types of phytoplasmas in canola with similar symptoms. One had the same RFLP profiles as the phytoplasmas in subgroup 16SrI-A, whereas the other one had RFLP profiles similar to those of phytoplasmas in subgroup 16SrI-B. Phytoplasmas were detected in symptomatic dandelion plants that were collected from canola and alfalfa fields where severe alfalfa witches'-broom occurred. Comparative studies indicated that two different phytoplasmas were associated with the dandelion plants. One was identified as a member of subgroup 16SrI-A, whereas another one was classified as a member of a distinct subgroup in the aster yellows group on the basis of the unique RFLP patterns.
Bird's Eye Lesions of Tomato Fruit Produced by Aerosol and Direct Application of Clavibacter michiganensis subsp. michiganensis
Authors: Medina-Mora C. M. , Hausbeck M. K. , Fulbright D. W.
Published: May 2007

Development of the bird's eye fruit lesion of tomato was studied by inoculating flowers and the surface of young tomato fruit with strains of Clavibacter michiganensis subsp. michiganensis. Flowers were sprayed once or twice with C. michiganensis subsp. michiganensis at 108 CFU/ml. The maximum incidence (80%) and severity (12 spots/fruit) of spotted fruit resulted when inoculum was sprayed twice, 3 days apart. Flowers were most susceptible to infection 2 days after anthesis. When a paintbrush was used to apply inoculum to the surface of small fruit, a large number of fruit spots (≤456 spots/fruit) resulted. Even strains determined to be avirulent based on a tomato stem inoculation assay and a hypersensitive response on four-o'clock leaves (Mirabilis jalapa) were able to produce fruit spots, although at a reduced level. The inoculation methods developed in this study can provide opportunities to observe subtle host-pathogen interactions between C. michiganensis subsp. michiganensis strains and tomato and to help formulate methods to quantify infection.
A Technique for Screening Grape Germplasm for Resistance to Meloidogyne incognita
Authors: Cousins P. M. , Walker M. A.
Published: May 2007

A technique to evaluate the root-knot nematode resistance of grape seedlings was developed. Seedlings of rootstock crosses and nematode-susceptible Vitis vinifera cvs. Colombard and Carignane were inoculated with Meloidogyne incognita juveniles. Reproduction of nematodes on individual plants was measured by counting the number of egg masses stained with eosin and the number of eggs present. Egg mass counts were highly correlated with egg counts. Resistant and susceptible cultivars could be clearly distinguished by the number of egg masses produced on vegetatively propagated cuttings. It is concluded that egg mass counting can substitute for the more laborious and time-consuming methods of counting nematode eggs or juveniles in the evaluation of root-knot nematode resistance in Vitis.
Resistance to Mefenoxam and Metalaxyl Among Field Isolates ofPhytophthora capsiciCausing Phytophthora Blight of Bell Pepper
Authors: Parra Gregory , Ristaino Jean Beagle
Published: May 2007

Incidence of Phytophthora blight in bell pepper fields that were sprayed for the first time with Ridomil Gold (mefenoxam) according to labeled recommendations was higher in North Carolina in 1997 than in previous years. Mefenoxam is the more active enantiomer contained in the racemic fungicide metalaxyl. A total of 150 isolates were obtained from 17 fields at eight grower locations. Among isolates from all locations, 30% were classified as sensitive, 10% as intermediate, and 59% were resistant to mefenoxam. Mefenoxam-resistant isolates were found in 82% of the fields sampled (14 of 17 fields). The proportion of resistant isolates in individual (fields ranged from 28 to 100%. The mean effective concentration (EC50) values for mefenoxam-sensitive isolates was 0.568 μg ml-1(ranging from 0.12 to 1.1 μg ml-1), whereas the mean EC50value for mefenoxam-resistant isolates was 366.5 μg ml-1(ranging from 3 to 863 μg ml-1). The mean EC50value for metalaxyl-sensitive isolates was 0.27 μg ml-1(ranging from 0.00002 to 1.3 μg ml-1) and for metalaxyl-resistant isolates was 470.34 μg ml-1(ranging from 10 to 966 μg ml-1). The greatest proportion of resistant isolates came from fields where mefenoxam was used alone rather than in combination with other fungicides. Both mating types were found among resistant isolates, suggesting that these isolates may persist in soil in subsequent years. Field isolates of Phytophthora capsici resistant to mefenoxam on pepper have not been reported previously and now pose new challenges for management of this important disease.
Pathogenic Variability of Puccinia coronata f. sp. avenae and P. graminis f. sp. avenae on Oat in South Africa
Authors: van Niekerk B. D. , Pretorius Z. A. , Boshoff W. H. P.
Published: May 2007

Although crown rust (caused by Puccinia coronata f. sp. avenae) and stem rust (caused by Puccinia graminis f. sp. avenae) are generally considered to be the most widespread and damaging diseases of oat (Avena spp.) in South Africa, pathogenic variability has never been studied. During 1997 and 1998, one dominant crown rust pathotype (SBLL) was identified with virulence to resistance genes Pc40, Pc45, Pc46, Pc51, and Pc54. Four other pathotypes (SGLL, PBBB+Pc35, SDQL, and JBBM+Pc35), occurring at low frequencies and further rendering resistance genes Pc35, Pc39, Pc48, Pc50, Pc52, and Pc64 ineffective, were also detected. Resistance gene Pc40 was postulated in Wisconsin X1588-2; Pc51 in Euro, Maluti, Overberg, OX88I 075-106, Perdeberg, and Swartberg; and Pc39 was confirmed in the cultivar Fidler. During the same period, four stem rust pathotypes were identified with virulence to resistance genes Pg1, Pg2, Pg4, Pg8, Pg9, Pg12,Pg15, and Pga. Resistance gene Pga was postulated in Alpha, OX87 080-1, OX88I 075-106, Sederberg, and W94/4; Pg2 and/or Pg4 in Euro, Perdeberg, Potberg, and Swartberg; and Pg9 in Pallinup and Victorian. Collections of wild oat species Avena fatua, A. byzantina, A. sterilis, and A. barbata were susceptible to all crown rust patho-types, while the four stem rust pathotypes were virulent on all species except A. barbata.
Bacterial Ring Rot of Potatoes Caused by Clavibacter michiganensis subsp. sepedonicus in Lithuania
Authors: Baranauskaite L. , Vasinauskiene M.
Published: May 2007

Bacterial ring rot of potato (Solanum tuberosum L.) was observed for the first time in Lithuania from 1998 to 1999. The disease, caused by Clavibacter michiganensis subsp. sepedonicus, is considered one of the most important bacterial diseases of potato. Nearly all countries that produce potatoes report the presence of the bacterium (1). C. michiganensis subsp. sepedonicus is listed as an A2 quarantine pathogen by the European and Mediterranean Plant Protection Organization. The pathogen has a latent period that can last for several generations of potato production, thus increasing the risk for further dissemination of the disease. Plant wilting and tuber rotting, characteristic symptoms of the disease, were observed in various localities in Lithuania. The disease was found in 12 potato varieties. Disease incidence approached 5% in the field and 5 to 21% in storage. The presence of C. michiganensis subsp. sepedonicus in diseased as well as asymptomatic plant tissue was determined by immunofluorescence cell staining and enzyme-linked immunosorbent assay with the use of monoclonal and polyclonal antibodies, respectively. More than 350 potato samples were tested. Twenty-five samples tested positive by these methods. Pathogenicity tests of 30 samples were conducted on eggplant. Characteristic symptoms were found on 21 plants. The bacteria were reisolated on nutrient dextrose agar medium from 12 inoculated eggplants. For confirmation of six suspicious strains, polymerase chain reaction with a specific Cms50 primer set was employed (2). In three cases, positive results were obtained.

References: (1) I. M. Smith and L. M. F. Charles, eds. 1998. Distribution of Maps of Quarantine Pests for Europe. CAB International, Wallingford, U.K. (2) D. Mills et al. Phytopathology 87:853, 1997.
First Report of Pepino mosaic virus in Canada and the United States
Authors: French C. J. , Bouthillier M. , Bernardy M. , Ferguson G. , Sabourin M. , Johnson R. C. , Masters C. , Godkin S. , Mumford R.
Published: May 2007

During the winter of 2000, tomatoes (Lycopersicon esculentum) with a bright yellow leaf mosaic were observed in a commercial greenhouse in southern Ontario, Canada. Examination of leaf extracts, using leaf dips and immunosorbent absorption electron microscopy (ISEM), showed flexuous rods consistent with the potexvirus group. Polyclonal antibodies raised against the original Peruvian Pepino mosaic virus (PepMV) isolate (1) and commercial antibodies obtained from Deutsche Sammlung von Mikro-organismen und Zellkulturen (DSMZ), GmbH, Braunsweig, Germany, and Plant Research International (PRI), Wageningen, the Netherlands, were used in ISEM. Leaves tested positive in double-antibody sandwich-enzyme-linked immunosorbent assay (ELISA) with antibodies from DSMZ and PRI. A triple-antibody sandwich-ELISA obtained from Adgen Ltd. (Nellies Gate, UK) gave similar results. Potato virus X did not react with PepMV antiserum in ELISA. Positive PepMV ELISA controls were a U.K. and a Dutch isolate supplied by R. Mumford and R. A. A. van Vlugt, respectively, and DSMZ. Using primers generated from a sequence of the RNA polymerase region of a U.K. PepMV isolate (R. Mumford, unpublished data), a reverse transcription-polymerase chain reaction test showed the expected 312-bp amplicon for the Canadian, Dutch, and U.K. isolates. The primer sequences used were forward 5′ CTA TTA CAA CTC CGG AAG CCA 3′ and reverse 5′ TGG TCT GGC CAG GCT TTG AC 3′. The three isolates were maintained in tomato cv. Bush Beefsteak. When mechanically inoculated on L. esculentum cv. Rapsodie, the Canadian isolate caused a bright yellow mosaic in 1 to 2 weeks, while the two European isolates caused a faint yellow mosaic and mild puckering of the leaves. When mechanically inoculated on 17 indicator plants, the Canadian isolate had a host range similar to the U.K. isolate. The most striking difference in symptoms occurred in L. pimpinellifolium, in which the Canadian isolate caused a yellow mosaic, the Dutch isolate caused no symptoms, and the U.K. isolate caused a marked puckering of the leaves, suggesting virus strain differences among the isolates. Tomato fruits originating from the United States were collected during border inspections by the Canadian Food Inspection Agency and tested for PepMV by ELISA with antisera from DSMZ. PepMV was not detected in 7 samples from California, but was detected in 6 of 12 samples from Colorado, 6 of 7 samples from Arizona, and 1 of 5 samples from Texas. PepMV was originally isolated from pepino (Solanum muricatum) in Peru in 1980 (1) and subsequently from tomato in the Netherlands in 1999 (2). To our knowledge, this is the first report of PepMV in North America.

References: (1) R. Jones et al. Ann. Appl. Biol. 94:61, 1980. (2) R. A. A. van Vlugt et al. Plant Dis. 84:103, 2000.
First Record of Barley yellow striate mosaic virus and Cereal yellow dwarf virus-RPV Infecting Wheat in Uzbekistan
Authors: Makkouk K. M. , Kumari S. G. , Kadirova Z. , Zueva A.
Published: May 2007

A preliminary survey to identify virus diseases affecting wheat in Uzbekistan was conducted during May 2001. The survey covered 12 wheat fields from 2 cereal-growing regions (Tashkent-Angren and Tashkent-Samarkand). A total of 250 wheat samples with symptoms suggestive of virus infection were collected and tested for the presence of nine viruses by tissue-blot immunoassay (TBIA) (1) at the Virology Laboratory of ICARDA, Aleppo, Syria, using the following antisera: monoclonal antibodies for Cereal yellow dwarf virus-RPV (CYDV-RPV) (ATCC PVAS-669 [American Type Culture Collection, Manassas, VA]) and Barley yellow dwarf virus-MAV (BYDV-MAV) (ATCC PVAS-673); and polyclonal antibodies for BYDV-SGV and BYDV-RMV (3); BYDV-PAV, Barley stripe mosaic virus, and Wheat streak mosaic virus (from Virology Laboratory, ICARDA); Wheat dwarf virus (provided by J. Vacke, Research Institute of Crop Production, Prague, Czeck Republic); and Barley yellow striate mosaic virus (BYSMV) isolated from Lebanon (2). The most common virus present was BYDV-PAV (detected in 12% of the 250 samples tested), followed by BYDV-SGV (10.8%), BYSMV (5.6%), BYDV-RMV (2.4%), BYDV-MAV (2%), and CYDV-RPV (1.2%). CYDV-RPV was detected in three fields; one field was 50 km southeast of Tashkent, and the other two fields were between Tashkent and Samarkand. The majority of BYSMV-positive samples originated from the same field, ≈40 km northeast of Samarkand. Field symptoms of BYSMV-infected plants included yellow flag leaf and stunting. All samples that produced a positive reaction to BYSMV-Lebanon antiserum were tested against four other rhabdovirus antisera: BYSMV-Italy, BYSMV-Morocco, Cereal chlorotic mottle virus, and American wheat striate mosaic virus. Serological tests showed that 100% of the samples reacted strongly with BYSMV-Italy and BYSMV-Morocco. In sodium dodecyl sulfate-polyacrylamide gel electrophoresis, followed by western blots, extracts from BYSMV-infected plants were found to contain 66- and 47-kDa structural proteins, typical of G and N proteins of rhabdoviruses, both of which reacted strongly with BYSMV-Italy antiserum. To our knowledge, this is the first report of BYSMV and CYDV-RPV in Uzbekistan.

References: (1) K. M. Makkouk and A. Comeau. Eur. J. Plant Pathol. 100:71, 1994. (2) K. M. Makkouk et al. Plant Dis. 85:446, 2001. (3) G. N. Webby and R. M. Lister. Plant Dis. 76:1125, 1992.
First Report of Cucumber leaf spot virus in Spain
Authors: Segundo E. , Janssen D. , Velasco L. , Ruiz L. , Cuadrado I. M.
Published: May 2007

Cucumber leaf spot virus (CLSV), reclassified as a species in the new genus Aureusvirus (family Tombusviridae) (1), has ≈30-nm isometric particles with a ≈4.4-kb positive-sense, single-stranded RNA. CLSV is transmitted by the chytrid fungus Olpidium bornovanus. The virus has been reported in Germany, Great Britain, Greece, Jordan, and Saudi Arabia. During the fall of 2000, abundant chlorotic spots with necrotic centers were observed on the leaves of cucumber plants grown in a commercial greenhouse in Granada (southeastern Spain). When sap from collected leaves was used to mechanically inoculate cucumber, symptoms were reproduced and were suggestive of CLSV. Based on the nucleic acid sequence of CSLV (2), the following specific primers were designed: CLSVU1440 (5′-AAGGTAGGGGAGATCTTG-3′) and CLSVA2160 (5′-GCTTCGGCTGATTCTGA-3′). When used in reverse transcription-polymerase chain reactions (RT-PCR), leaves expressing symptoms yielded amplification products of the expected size (720 bp). These products were cloned into a pGEM-T vector and sequenced (GenBank Accession No. AY038365). The similarity of the nucleic acid and derived amino acid sequences with the one published for CLSV (2) was 94.5 and 99.1%, respectively. The amino acid sequence was 86% identical to that of Pothos latent virus (GenBank Accession No. AJ243370). Ten cucumber plants grown in vermiculite supplemented with rhizosphere soil (1/30, vol/wt) from infected plants developed symptoms on leaves after 1 month and were positive for CLSV when leaf and root tissues were analyzed by RT-PCR and Southern blot hybridization. Plants grown in vermiculite alone did not become infected with CLSV. Microscopic examination of root tissue revealed O. bornovanus only in infected plants. To our knowledge, this is the first record of CSLV in Spain.

References: (1) G. P. Martelli et al. Arch. Virol. 143:1847, 1998. (2) J. S. Miller et al. Virus Res. 52:51, 1997.
Evaluation of Host Resistance and Soil Fumigation for the Management of Black Root Rot of Tobacco in Ontario
Authors: Haji H. M. , Brandle J. E.
Published: May 2007

Black root rot of tobacco, caused by the soilborne fungus Thielaviopsis basicola, is a serious problem in many tobacco (Nicotiana tabacum L.)-growing regions of the world. In Ontario, the disease is favored by cool, wet soil conditions and heavy textured or poorly drained soils. Yield loss can be severe under these conditions and fumigants containing chloropicrin are used extensively for controlling the disease. Usually, fumigants control the disease reasonably well, but they are costly and could cause a negative environmental impact. A 2-year study was conducted to evaluate the performance of resistant (AC Gayed) and moderately susceptible (Delgold) tobacco cultivars and soil fumigation to black root rot. T. basicola reduced yield of the susceptible Delgold cultivar. The interaction between genotype and fumigation was significant for most traits examined, indicating that the two genotypes responded differently. Orthogonal comparisons indicate that yield from nonfumigated AC Gayed was higher than that of nonfumigated Delgold. Yield of nonfumigated AC Gayed was also not significantly different from the yield of AC Gayed treated either with Vorlex Plus (1,3-dichloropropene+methyl isothiocyanate) or with Vorlex Plus CP (1,3-dichloropropene+methyl isothiocyanate+chloropicrin). In contrast, the yield of nonfumigated Delgold was lower than Delgold treated with Vorlex Plus CP.
Effects of Water Stress on Symptomatology and Growth of Parthenocissus quinquefolia Infected by Xylella fastidiosa
Authors: McElrone Andrew J. , Sherald James L. , Forseth Irwin N.
Published: May 2007

A greenhouse study was conducted to test the hypothesis that bacterial leaf scorch symptoms, caused by Xylella fastidiosa, are more severe during periods of drought stress. A two-by-two complete factorial design with two pathogen treatments (control and infected) and two soil moisture levels (high and low) was used with Parthenocissus quinquefolia vines in 1999 and 2000. In each year, a high percentage of P. quinquefolia plants inoculated with X. fastidiosa expressed typical bacterial leaf scorch symptoms, with the outer scorched portion of the leaf separated from green tissue by a chlorotic halo. X. fastidiosa was detected in all symptomatic plants using an immunomagnetic capture and nested polymerase chain reaction technique, and was reisolated and cultured in modified periwinkle wilt liquid media. In both years, symptoms progressed further along the stem and were more severe at corresponding leaf positions in low-water-infected plants compared to high-water-infected plants. Total leaf area, shoot length, and number of nodes on the longest shoot per plant were all reduced due to drought and X. fastidiosa infection. This study is the first to verify the hypothesis that bacterial leaf scorch symptoms are enhanced during drought stress. Maintaining plant vigor with regular watering can be used to sustain plants infected by X. fastidiosa, particularly during periods of water stress.
Molecular Detection and Differentiation of Erwinia pyrifoliae and Host Range Analysis of the Asian Pear Pathogen
Authors: Kim Won Sik , Jock Susanne , Paulin Jean-Pierre , Rhim Seong-Lyul , Geider Klaus
Published: May 2007

The recently described pathogen Erwinia pyrifoliae, isolated from Nashi pear fruit trees in Korea, resembles the fire blight pathogen Erwinia amylovora in some of its properties. The two pathogens were classified into different species by DNA hybridization kinetics and microbiological criteria. From the nucleotide sequences of the 16S rRNA and the internal transcribed spacer (ITS) region as well as extracellular polysaccharide (EPS)-encoding genes, polymerase chain reaction (PCR) primers were designed that specifically detect E. pyrifoliae but not the fire blight pathogen Erwinia amylovora, and these primers were also applied to identify E. pyrifoliae in necrotic plant material. The genomes of several strains were digested with the restriction enzyme SpeI, and the DNA fragments were analyzed by pulsed-field gel electrophoresis (PFGE). Three groups of patterns could be distinguished for the isolated E. pyrifoliae strains, all different from various E. amylovora strains, which produce a relatively homogeneous PFGE pattern after SpeI digests. Typical fire blight host plants were assayed in a growth chamber or an experimental field for their susceptibility to E. pyrifoliae. A strong preference was found for pear varieties, whereas apple, cotoneaster, hawthorn, or raspberry rarely produced necrotic symptoms. E. pyrifoliae was readily detected in samples from pear orchards in South Korea during 1995 to 1998; however, the Asian pear pathogen was not recovered in necrotic plant tissue from 1999 and 2000.
First Report of Resistance to Benomyl Fungicide in Sclerotinia sclerotiorum
Authors: Gossen B. D. , Rimmer S. R. , Holley J. D.
Published: May 2007

Benomyl fungicide (Benlate) is used worldwide to control ascomycete pathogens, but resistance has developed in several pathogen populations (1). On the Canadian prairies, benomyl is used to reduce injury caused by Sclerotinia sclerotiorum (Lib.) de Bary on canola (Brassica napus, B. rapa) and alfalfa (Medicago sativa) seed crops. To determine if populations are resistant to benomyl, isolates of S. sclerotiorum collected from 15 fields (12 alfalfa and 3 canola, one isolate per field) in 2000 were grown on potato dextrose agar amended with benomyl at 0, 0.05, 0.5, 5, 50, and 500 mg/liter. Plugs of mycelium from the margin of an actively growing colony were placed in the center of a 10-cm-diameter petri dish containing 15 ml of test medium and incubated on a laboratory bench. Linear growth (mean of maximum width and right angle) of each colony (three replicates each) was measured after 5 to 6 days. The growth of isolates from 13 fields was inhibited by low concentrations of benomyl (EC50 < 8 mg/liter), but two isolates were very resistant (EC50 > 200 mg/liter). Resistant cultures were isolated from infected canola plants in the only two fields in the study in which reduced efficacy of benomyl was suspected. The distribution and importance of benomyl-resistant populations of S. sclerotiorum in the region remains to be determined.

Reference: (1) T. R. Pettitt et al. Mycol. Res. 97:1172, 1993.
First Report of Erysiphe sedi on Sedum spectabile in North America
Authors: Kiss L. , Daughtrey Margery L.
Published: May 2007

Since 1997, powdery mildew infections have been repeatedly observed on Sedum spectabile plants, cv. Autumn Joy, grown as ornamentals in commercial greenhouses in New York. Circular patches of gray mycelia appeared and spread on upper and occasionally on lower leaf surfaces followed by necrosis of the leaf tissues and defoliation. The new disease reduced the market value of the infected ornamentals and required chemical control. The pathogen produced conidia singly on 2- to 3-celled conidiophores occurring on the ectophytic hyphae. Conidia were subcylindrical, measured 27 to 36 μm × 13 to 17 μm, and contained no fibrosin bodies. Germinating conidia produced a short germ tube, 5 to 30 μm, terminating in a lobed appressorium. Hyphal appressoria were lobed to multi-lobed, opposite or spread along the hyphae. Cleistothecia were not found. Based on conidial characteristics, the pathogen was identified as Erysiphe sedi Braun. To confirm pathogenicity, potted healthy S. spectabile plants were placed near infected plants in the greenhouse. In addition, detached S. spectabile leaves were inoculated with the pathogen by touching them to powdery mildew colonies and then placed in plates filled with one layer of polystyrene balls floated in water. Plates were covered and kept in the laboratory. Uninfected potted plants kept in another greenhouse and noninoculated detached leaves served as controls. After 1 week, powdery mildew appeared on all infected plants and leaves exposed to or inoculated with the pathogen. The pathogen was morphologically identical to the original fungus. No symptoms were observed on the controls. E. sedi is a common Asiatic powdery mildew species infecting many crassulaceous plants (1,2) and was introduced to Eastern Europe from Asia (2). To our knowledge, this is the first report of E. sedi in North America.

References: (1) U. Braun. Beih. Nova Hedwigia 89:1, 1987. (2) U. Braun. The Powdery Mildews (Erysiphales) of Europe. Gustav Fisher Verlag, Jena, 1995.
First Report of Natural Infection by “Candidatus Phytoplasma brasiliense” in Catharanthus roseus
Authors: Montano H. G. , Dally E. L. , Davis R. E. , Pimentel J. P. , Brioso P. S. T.
Published: May 2007

Catharanthus roseus (L.) G. Don (periwinkle) is well known as an experimental host for diverse phytoplasmas that are artificially transmitted to it through the use of dodder (Cuscuta sp.), laboratory vector insects, or grafting. However, few phytoplasma taxa have been reported in natural infections of C. roseus, and the role of C. roseus in phytoplasma dissemination and natural disease spread is not clear. In this study, naturally diseased plants of C. roseus exhibiting yellowing and witches' broom symptoms indicative of phytoplasma infection were observed throughout the year in the state of Rio de Janeiro, Brazil. Shoots and leaves of four diseased plants were assayed for the presence of phytoplasma DNA sequences by nested polymerase chain reactions (PCR) as previously described (2,3). Phytoplasma rDNA was amplified from diseased periwinkle plants in PCR primed by primer pair P1/P7 and was reamplified in nested PCR primed by primer pair R16F2n/R16R2 (F2n/R2). The results indicated the presence of phytoplasma in all four diseased plants. Phytoplasma identification was accomplished by restriction fragment length polymorphism (RFLP) analysis, using 11 restriction enzymes, of 16S rDNA amplified in PCR primed by F2n/R2. Phytoplasmas were classified according to the system of Lee et al. (1). On the basis of collective RFLP patterns of 16S rDNA, the phytoplasma infections in the four periwinkle plants could not be distinguished from one another. Furthermore, the collective RFLP patterns were indistinguishable from those reported previously for hibiscus witches' broom phytoplasma, “Candidatus Phytoplasma brasiliense” (2). The phytoplasma found in C. roseus, designated strain HibWB-Cr, was classified in group 16SrXV (hibiscus witches' broom phytoplasma group). HibWB-Cr is tentatively considered a new strain of “Ca. P. brasiliense”. C. roseus is the first known, naturally diseased alternate plant host of “Ca. P. brasiliense”. The present study identified strain HibWB-Cr in Rio de Janeiro State, where hibiscus witches' broom disease is prevalent (2). How this economically important disease of hibiscus spreads is not known. Our findings raise the possibility that a polyphagous insect vector is involved in the natural transmission of “Ca. P. brasiliense” and that C. roseus or other plant species serve as reservoirs for the spread of this phytoplasma taxon.

References: (1) I.-M. Lee et al. Int. J. Syst. Bacteriol. 48:1153, 1998. (2) H. G. Montano et al. Int. J. Syst. Evol. Microbiol. 51:1109, 2001. (3) H. G. Montano et al. Plant Dis. 84:429, 1999.