bluuebunny/crossref_metadata_2025 huggingface dataset:
First Report of Tomato yellow leaf curl virus Infecting Common Bean (Phaseolus vulgaris) in Greece
Authors: Papayiannis L. C. , Paraskevopoulos A. , Katis N. I.
Published: May 2007

Tomato yellow leaf curl is one of the most devastating virus diseases of tomato (Lycopersicon esculentum Mill) crops worldwide. Several whitefly-transmitted viruses are associated with the disease and all are assigned to the genus Begomovirus, family Geminiviridae. In Greece, Tomato yellow leaf curl virus (TYLCV) was first reported to infect greenhouse and open-field tomatoes in 2000 (2). During 2006, a survey was conducted in the southwestern part of Peloponnese (mainland) within the areas of Kyparissia and Filiatra (Perfecture of Messinia) to identify the prevalence and natural hosts of the disease. During this survey, yellow mosaic, severe leaf curling, and leaf crumple symptoms were observed in greenhouse bean plants (Phaseolus vulgaris) that were cultivated together with tomatoes showing typical TYLCV symptoms. In all affected greenhouses, the incidence of the disease ranged from 1 to 5% in beans and 90 to 100% in tomato plants. Both bean and tomato plants were highly infested with Bemisia tabaci (Gennadius) populations and produced unmarketable fruits. Twenty-four symptomatic bean plants were collected from four greenhouses that tested positive by triple-antibody sandwich-ELISA using TYLCV-specific antibodies purchased from NEOGEN, EUROPE, Ltd. DNA was extracted from all infected bean plants, and a 580-bp fragment of the coat protein gene was amplified by PCR using the TY(+)/TY(-) primer pair (1). Amplified fragments were then analyzed by restriction fragment length polymorphism with Ava II cutter enzyme. Two DNA fragments of 277 and 302 bp in agarose gels were produced from all isolates and the restriction pattern corresponded to TYLCV. The amplified DNA from four infected bean plants was cloned and sequenced. All four sequences were 100% identical (EMBL Accession No. AM418398) and showed 99% nucleotide identity to a TYLCV isolate from Italy (EMBL Accession No. DQ144621). To our knowledge, this is the first report of TYLCV infection of P. vulgaris, which is an important commercial crop in Messinia, Greece. Within the last decade, TYLCV has emerged as an important pathogen for several cultivated plants in many regions and different TYLCV variants have been reported to infect P. vulgaris (3). Bean is often used as an intercrop between tomato crops, and thus, infected plants may serve as a potential reservoir for virus survival and spread (4).

References: (1) G. P. Accotto et al. Eur. J. Plant Pathol. 106:179, 2000. (2) A. D. Avgelis et al. Plant Dis. 85:678, 2001. (3) J. Morris et al. EPPO Bull. 32:41, 2002. (4) J. Navas-Castillo et al. Plant Dis. 83:29, 1999.
Transmission of ‘Candidatus Phytoplasma aurantifolia’ to Bakraee (Citrus reticulata Hybrid) by Feral Hishimonus phycitis Leafhoppers in Iran
Authors: Salehi M. , Izadpanah K. , Siampour M. , Bagheri A. , Faghihi S. M.
Published: May 2007

Witches'-broom disease of lime (WBDL) caused by ‘Candidatus Phytoplasma aurantifolia’ is a devastating disease in the Sultanate of Oman, United Arab Emirates, and southern Iran. The disease primarily affects lime (Citrus aurantifolia), but in Iran, it is also found in bakraee, a natural C. reticulata hybrid. The disease has been experimentally transmitted from lime to several citrus cultivars by grafting and to a number of herbaceous hosts by dodder. However, the natural vector of ‘Ca. P. aurantifolia’ has not been determined. The most common phloem-feeding insect associated with lime trees in the area is the leafhopper Hishimonus phycitis. The WBDL phytoplasma has been detected in the body of this leafhopper by ELISA and PCR (1), but previous attempts to establish its vector status have failed. It was recently reported that the leafhopper can release the phytoplasma into a sugar solution by feeding through a Parafilm membrane (4). Here we report successful transmission of WBDL phytoplasma to bakraee seedlings by H. phycitis. The leafhopper nymphs and adults were collected in a WBDL-infected lime orchard in Minab (Hormozgan Province) in May of 2006. Of more than 100 leafhopper samples tested, at least 70% were positive for the phytoplasma by PCR using P1/P7 primer pair (3). Additional field-collected leafhoppers were caged (five per plant) on bakraee seedlings at the two-leaf stage in pots in the greenhouse in Zarghan (Fars Province). After 8 weeks, the remaining leafhoppers were killed with an insecticide. Six months after inoculation, 3 of 10 inoculated plants showed typical symptoms of WBDL, including bud proliferation, general chlorosis, and stunting. Symptomatic plants were strongly positive in PCR assays using primer pair P1/P7. No amplification was obtained with healthy control lime or nonsymptomatic bakraee seedlings. Amplified P1/P7 primed PCR products (1,800 bp) from experimentally vector-challenged bakraee seedlings, captured H. phycitis, and a naturally infected lime tree from Minab were subjected to restriction fragment length polymorphism (RFLP) analysis using AluI, HhaI, HpaII, RsaI, and TaqI enzymes. RFLP patterns from these sources were identical and similar to those reported earlier (2). These analyses verified the identity of WBDL phytoplasma in experimentally infected bakraee seedlings. To our knowledge, this is the first report of natural transmission of ‘Ca. P. aurantifolia’ by H. phycitis.

References: (1) J. M. Bové et al. Proc. Conf. IOCV 12:342. 1993. (2) A. J. Khan et al. Phytopathology 92:1038, 2002. (3) B. Schneider et al. Pages 369–380 in: Molecular and Diagnostic Procedures in Mycoplasmology. Vol. 2. S. Razin and J. G. Tully, eds. Academic Press, New York, 1995. (4) M. Siampour et al. Iran. J. Plant Pathol. 41:139 (Farsi) and 35 (English), 2006.
First Report of Alternaria dianthicola Causing Leaf Blight on Withania somnifera from India
Authors: Maiti C. K. , Sen S. , Paul A. K. , Acharya K.
Published: May 2007

Withania somnifera (L.) Dunal, a potential medicinal plant used for the treatment of nervous disorders, intestinal infection, leprosy, and cancer, is a perennial herb belonging to Solanaceae and distributed throughout the drier parts of India. Leaf blight disease of this plant generally occurs during March in various districts of South Bengal, India. At the initial stage of infection, symptoms appear as small, light brown spots, gradually becoming irregular, dark brown, concentrically zonate with a diffuse margin, frequently surrounded by light yellow haloes, conspicuous brownish concentric rings in the advance stage of infection. A species of Alternaria was isolated from the lesions. The pathogen was isolated on potato dextrose agar (PDA) media. On PDA, the fungus grew slowly with colonies reaching approximately 35 to 40 mm in diameter in 7 days when incubated at 30°C. Conidiophores arose singly or in groups, straight or flexous, cylindrical, septate, pale to olivaceous brown, as much as 155 μm long, 4 to 5.5 μm thick; conidia were straight, obclavate, pale olivaceous brown, smooth, with up to 15 transverse and rarely 1 or 2 longitudinal or oblique septa and measured 50 to 115 × 5 to 10 μm. Pathogenicity tests were carried out three times on 6-month-old plants (n = 10). Plants were sprayed with a conidial suspension of 105 conidia/ml; control plants were sprayed with sterilized water. Plants were covered with polyethylene bags for 10 days. Disease symptoms appeared after 12 ± 1 day after inoculation. Symptoms on the leaves were similar to those of a naturally occurring diseased plant. The fungal pathogen was consistently reisolated from inoculated plants. The pathogen was identified as Alternaria dianthicola and further confirmed by the Agharkar Research Institute, Pune, India. A literature survey reports the occurrence of some fungal diseases (1), but to our knowledge, this is the first report of A. dianthicola on W. somnifera.

References: (1) P. Sinha et al. Page 14 in: Recent Progress in Medicinal Plants. Vol. 6 Diseases and their Management. Sci Tech Publishing LLC, Houston, TX, 2000.
First Report of Iris yellow spot virus on Onion and Leek in Western Oregon
Authors: Gent D. H. , Martin R. R. , Ocamb C. M.
Published: May 2007

Onion (Allium cepa) and leek (Allium porrum) are grown on approximately 600 ha in western Oregon annually for bulb and seed production. During July and August of 2006, surveys of onion bulb crops and onion and leek seed crops in western Oregon found plants with symptoms of elongated to diamond-shaped, straw-colored lesions characteristic of those caused by Iris yellow spot virus (IYSV) (1–4). Symptomatic plants were collected from fields of an onion bulb crop, an onion seed crop, and two leek seed crops located in Marion County. The onion bulb crop had been planted in the spring of 2006, and the onion and leek seed crops had been planted in the fall of 2005, all direct seeded. Cultivar names were not provided for proprietary purposes. Symptomatic plants in the onion bulb crop and leek seed crop generally were found near the borders of the field. Disease incidence was less than 5% and yield losses in these crops appeared to be negligible. In the onion seed crop, symptomatic plants were found throughout the field and disease incidence was approximately 20%. Approximately 1% of the onion plants in this field had large necrotic lesions that caused the seed stalks (scapes) to lodge. The presence of IYSV was confirmed from symptomatic leaves and scapes by ELISA (Agdia Inc., Elkhart, IN) using antiserum specific to IYSV. RNA was extracted from symptomatic areas of onion leaves and scapes, and a portion of the nucleocapsid gene was amplified by reverse transcription-PCR. The amplicons were sequenced and found to share more than 99% nucleotide and amino acid sequence identity with an onion isolate of IYSV from the Imperial Valley of California (GenBank Accession No. DQ233475). In the Pacific Northwest region of the United States, IYSV has been confirmed in the semi-arid regions of central Oregon (1), central Washington (2), and the Treasure Valley of eastern Oregon and southwest Idaho (3). To our knowledge, this is the first report of the disease on a host crop in the mild, maritime region west of the Cascade Mountain Range and the first report of IYSV on leek seed crops in the United States, which complements a simultaneous report of IYSV on commercial leek in Colorado. The presence of IYSV may have implications for the iris and other ornamental bulb industries in western Oregon and western Washington. This report underscores the need for further research to determine the impact of the disease on allium crops and other hosts and the development of effective management programs for IYSV and the vector, Thrips tabaci.

References: (1) F. J. Crowe and H. R. Pappu. Plant Dis. 89:105, 2005. (2) L. J. du Toit et al. Plant Dis. 88:222, 2004. (3) J. M. Hall et al. Plant Dis. 77:952, 1993. (4) H. F. Schwartz et al. Plant Dis. 91:113, 2007.
Rapid Determination of Rice Cultivar Responses to the Sheath Blight Pathogen Rhizoctonia solani Using a Micro-Chamber Screening Method
Authors: Jia Y. , Correa-Victoria F. , McClung A. , Zhu L. , Liu G. , Wamishe Y. , Xie J. , Marchetti M. A. , Pinson S. R. M. , Rutger J. N. , Correll J. C.
Published: May 2007

An accurate greenhouse screening method has not been developed previously to identify host response to sheath blight disease caused by Rhizoctonia solani Kühn that causes significant economic losses in rice yield worldwide. The unavailability of a robust screening system in the greenhouse has made it difficult to quantify disease reactions to R. solani, and has hampered studies on the genetics of resistance and plant breeding efforts to improve resistance. In an effort to develop a standardized laboratory micro-chamber screening method to quantify resistance to R. solani in rice, five rice cultivars, representing a wide range of observed disease reactions under field conditions, were examined in a blind inoculation test at three locations (Arkansas, Texas, and Colombia). Rice seedlings were inoculated at the three- to four-leaf stage with potato dextrose agar plugs containing mycelium and then covered with a 2- or 3-liter transparent plastic bottle for maintaining high humidity after inoculation. Two cultivars, Jasmine 85 and Lemont, that consistently have shown the highest and lowest levels of resistance, respectively, in previous field and greenhouse studies, were used as standards. Concurrent field experiments in Arkansas and Texas also were performed to compare the greenhouse disease ratings with those observed under field conditions. Overall, the relative disease ratings of the seven test cultivars were consistent between test locations and with field evaluations. Thus, the micro-chamber screening method can be used as an effective approach to accurately quantify resistance to the sheath blight pathogen under controlled greenhouse conditions and should help expedite the selection process to improve resistance to this important pathogen.
Discriminating Between Isolates of PSbMV Using Nucleotide Sequence Polymorphisms in the HC-Pro Coding Region
Authors: Torok V. A. , Randles J. W.
Published: May 2007

The molecular diversity of 14 isolates of Pea seed-borne mosaic virus (PSbMV) from southern Australia, 13 previously described isolates from Pakistan, and a reference isolate from the United States have been studied to determine whether a relatively simple molecular diagnostic assay and classification scheme could be developed for this virus. The Australian isolates were placed into either pathotype P1 or pathotype P4 by bioassay on differential genotypes of Pisum sativum. The Pakistani isolates represented pathotypes P1, P4, U1, and U2, and an undetermined pathotype. The reference US isolate was pathotype P1. A reverse transcription-polymerase chain reaction (RT-PCR) assay based on an amplicon from the variable HC-Pro coding region of potyviruses was shown to distinguish PSbMV from seven other legume infecting potyviruses. Restriction fragment length polymorphisms (RFLPs) generated from the HC-Pro RT-PCR products of all 28 isolates using seven restriction endonucleases placed them into eight groups. A phylogenetic tree based on a Bray-Curtis similarity comparison placed the groups into three clusters. The groups and clusters had no clear association with either pathotype or geographic source. It is concluded that within the range of viruses and isolates tested, the RT-PCR-RFLP method will both specifically identify PSbMV and provide a simple, qualitative, and rapid means for placing PSbMV isolates into groups. Applications could include mapping and tracking isolates in space and time.
Generation and Dissipation of Methyl Isothiocyanate in Soils Following Metam Sodium Fumigation: Impact on Verticillium Control and Potato Yield
Authors: Triky-Dotan Shachaf , Austerweil Miriam , Steiner Bracha , Peretz-Alon Yitzhak , Katan Jaacov , Gamliel Abraham
Published: May 2007

The fate of methyl isothiocyanate (MITC) was studied in agricultural soils following metam sodium (MS) application in a controlled system and under field conditions as it was related to disease control. Soil samples were collected from 34 field sites in Israel with no history of MS application. The generation and dissipation curves of MITC in these soils, under controlled conditions, varied significantly among the soils, as reflected by the concentration by time (C × T) product. This value was significantly related with the mortality level of Fusarium oxysporum f. sp. radicis-lycopersici as a test organism and sand content of the soils. Seven field experiments were conducted in potato fields from 2001 to 2004. The MS treatments significantly reduced Verticillium wilt incidence and severity in five and four experiments, respectively, out of seven. Combining MS with formalin was more effective for controlling disease than MS alone in most cases. A significant relationship was found between mortality of F. oxysporum f. sp. radicis-lycopersici in soil samples to which MS was applied under controlled conditions and the incidence of Verticillium wilt disease in the field, and between CMITC × T products and the incidence of Verticillium wilt disease in the field. These tests can be used for preplant assessment of potential MS efficacy.
First Report of Peanut mottle virus in Forage Peanut (Arachis glabrata) in North America
Authors: Nischwitz C. , Maas A. L. , Mullis S. W. , Culbreath A. K. , Gitaitis R. D.
Published: May 2007

Rhizoma peanut (Arachis glabrata Benth.) is a forage crop with increasing acreage (>10,500 ha) in the coastal plain region of the United States. Peanut mottle virus (PeMoV), a member of the family Potyviridae, is transmitted nonpersistently by aphids and seed-transmitted in A. hypogaea. Important hosts of the virus include peanut, soybean, and pea. During January of 2006 in Tifton, GA, immature rhizoma peanut plants identifier A176 with a lost PI number and PI 243334 exhibiting chlorotic ringspots were tested for viruses (potyviruses, Tomato spotted wilt virus [TSWV] and Cucumber mosaic virus [CMV]) frequently found in crops in the southeastern United States. All symptomatic plants tested were positive in the general potyvirus screen by indirect ELISA (Agdia, Inc., Elkhart, IN) and negative for TSWV and CMV. Leaves from two symptomatic plants of A176 and several asymptomatic genotypes were blotted onto FTA cards (Whatman Inc., Maidstone, UK) to bind viral RNA for preservation and processed according to the manufacturer's protocol. To determine the specific potyvirus identity, punch-outs from the FTA cards were used for reverse transcription (RT)-PCR (3) to test for PeMoV and Peanut stripe virus (PStV), both of which are found in A. hypogaea in Georgia. The forward primer (5′-GCTGTGAATTGTTGTTGAGAA-3′) and the reverse primer (5′-ACAATGATGAAGTTCGTTAC-3′) were specific for PeMoV and the forward primer (5′-GCACACACTTCTTGGC ATGG-3′) and reverse primer (5′-GCATGCCCTCGCCATTGCAA-3′) were specific for PStV (2). The primers are specific to the respective viral coat protein genes. Amplicons of the expected size (327 bp) were produced from symptomatic A176 and PI 243334 samples but not from the asymptomatic genotypes. The resulting PCR product was sequenced and a BLAST search in GenBank confirmed PeMoV (98 to 99% nt identity with Accession Nos. X73422 and AF023848). This finding is of significance because rhizoma peanuts are typically propagated by cuttings. Therefore, maintaining virus-free stock is critical. Although, PeMoV has been found in A. pintoi in Colombia (1), to our knowledge, this is the first report of PeMoV in rhizoma peanut (A. glabrata) peanut anywhere in the world.

References: (1) A. A. Brandt et al. Plant Viruses Online: Descriptions and Lists from the VIDE Database, 2007. (2) R. G. Dietzgen et al. Plant Dis. 85:989, 2001. (3) R. D. Gitaitis et al. Phytopathology (Abstr.) 95(Suppl):S35, 2005.
Phytophthora Blight Caused by Phytophthora capsici on Pumpkin and Winter Squash in Texas
Authors: Isakeit T.
Published: May 2007

Phytophthora blight of pumpkin and squash (Cucurbita spp.) has increased in importance in many production areas of the United States in recent years. This disease was seen on a 36-ha commercial field of several cultivars of pumpkin and winter squash (including Cucurbita maxima cvs. Prizewinner, Atlantic Giant, and Casper and C. pepo cvs. Howden, Festival, Sweet Dumpling, and Magic Lantern) in Yoakum County in the High Plains of Texas during August of 2006. At that time, 2% of the field was affected. A month later, after unusually frequent rain showers and higher-than-average precipitation, 78% of the field was lost in spite of an aggressive fungicide program following the initial diagnosis. Symptoms consisted of white, velvety growth on fruit, fruit rot, leaf blight, and wilt. Sporangia on fruit were papillate, ovoid to ellipsoid, and measured 37 to 40 × 21 to 23 μm. Isolations were made from tissue onto water agar and two isolates used for further study were maintained on corn meal agar. When isolates were paired on V8 agar with two Phytophthora capsici isolates from pepper (3) of opposite mating type, amphigynous antheridia and plerotic oospores 25 to 27 μm in diameter were produced. The morphological characteristics of the isolates were consistent with P. capsici (1). Four-week-old plants of C. maxima cv. Cinderella and C. pepo cvs. Festival and Sweet Dumpling growing in Metro-Mix 366 were inoculated with each isolate by placing 2 cm3 of a 6-week-old culture from lima bean agar (0.2% agar) adjacent to the base of each stem. The soil was then watered to saturation. There were four plants per 2.8-liter pot and two pots per isolate-cultivar combination. Plants were grown in the greenhouse at 18 to 27°C. The test was repeated once. Wilting and stem collapse were seen on inoculated plants 2 to 7 days later, sometimes with production of sporangia on stems. The pathogen was consistently reisolated from symptomatic plants, fulfilling Koch's postulates. These isolates were also pathogenic to pepper (Capsicum annuum). The affected field had been planted to pumpkins and winter squash the previous year when the grower saw similar symptoms on a few plants. In 2004, this field was planted to wheat. There are 1,350 ha of pumpkins produced in Texas, mostly in High Plains counties, and 730-ha squash produced throughout the state. To my knowledge, this is the first report of Phytophthora blight on pumpkin and winter squash in Texas. Phytophthora blight has been a long-standing problem of peppers grown in the Lower Rio Grande Valley of Texas (2), which is 900 km from Yoakum County.

References: (1) D. C. Erwin and O. K. Ribeiro. Phytophthora Diseases Worldwide. The American Phytopathological Society. St. Paul, MN. 1996. (2) G. H. Godfrey. Plant Dis. Rep. 31:8, 1947. (3) B. Villalon. Phytopathology (Abstr.) 86(suppl):S118, 1996.
Blight of English Ivy (Hedera helix) Caused by Sclerotium rolfsii in Sicily
Authors: Pane A. , Raudino F. , Adornetto S. , Russo G. Proietto , Cacciola S. O.
Published: May 2007

English ivy, Hedera helix L. (Araliaceae), an evergreen climbing vine is widely cultivated as an ornamental and foliage plant. In the summer of 2005, a severe blight of ivy plants trained as topiaries and grown in an open field was observed in a nursery near Giarre (eastern Sicily). Foliage of infected plants appeared lighter green and progressively turned bronze and withered. Eventually, the entire plant collapsed. Foliar symptoms were associated with basal stem and root rot. White, cottony mycelium and numerous sclerotia developed externally on the lower stem and on the soil around the affected plants. The disease was randomly distributed, affecting approximately 5% of plants in a stock of 1,500 English ivy plants. Sclerotium rolfsii Sacc. (teleomorph Athelia rolfsii (Curzi) Tu & Kimbrough) was consistently isolated from symptomatic basal stem tissues by disinfecting in 1% NaOCl and plating on potato dextrose agar (PDA) amended with 100 mg/liter of streptomycin sulfate. The isolated fungus was identified on the basis of morphological and cultural characteristics (2). On PDA, it produced a densely, floccose, white mycelium. Mycelium was septate with clamp connections at hyphal septa. Optimum growth temperature was 30 ± 2°C. Numerous small (0.5 to 1.9 mm in diameter) sclerotia developed on the colony surface; they were spherical, occasionally slightly ellipsoidal, quite uniform in size (modal value of the diameter 1.4 mm), with a smooth surface. The surface color of the sclerotia was initially white, turned to pinkish buff, then to olive-brown, and eventually to clove brown as sclerotia matured. Sclerotia were most numerous in the center as well as close to the edge of petri dishes. Pathogenicity of one isolate obtained from infected plants was confirmed by inoculating 10 1-year-old potted English ivy plants by placing mycelium-infested wheat kernels and sclerotia on the soil surface around the collar of each plant. Ten noninoculated plants served as control. Plants were held in a dew chamber for 48 h at 28°C and subsequently placed in a greenhouse where the temperature ranged between 25 and 31°C. Plants showed wilting within 3 weeks after inoculation. Fans of white mycelium and numerous sclerotia were produced on the basal stem of inoculated test plants. Noninoculated controls remained healthy. S. rolfsii was reisolated from infected plants to fulfill Koch's postulates. English ivy has been already reported as a host of S. rolfsii, the causative agent of southern blight in nurseries of ornamentals (1). However, to our knowledge, this is the first report of southern blight on English ivy in Italy. The disease may have been favored by warm summer temperatures and overwatering with a drip irrigation system.

References: (1) A. R. Chase. Compendium of Ornamental Foliage Plant Diseases. The American Phytopathological Society, St. Paul, MN, 1992. (2) J. E. M. Mordue. Corticium rolfsii. No. 410 in: Description of Pathogenic Fungi and Bacteria. CMI. Kew, Surrey, UK, 1974.
Sawadaea Powdery Mildew of Box Elder (Acer negundo) in Wisconsin
Authors: Stanosz G. , Smith D. , Stanosz J.
Published: May 2007

Box elder leaves affected by powdery mildew were collected from a single tree in an urban yard in the fall of 2006 in Madison, WI. As much as half of the area of the leaf blades, when viewed from above or below, was pale green-to-tan and necrotic. Mycelium was not visible to the eye on either the upper or lower leaf surfaces, but very sparse white mycelium was observed on the lower surface of leaves with the aid of a dissecting microscope. Chasmothecia were present singly or in groups of a few on the lower surface of leaves. Morphology of the chasmothecia, including simple and bifid appendages with uncinate to circinate apices, was sufficient to identify the pathogen to the genus Sawadaea (1). Other characters were not sufficiently distinct to make an identification of the species. However, DNA was extracted from the chasmothecia, and analysis of a 542-bp sequence of nuclear rDNA ITS (GenBank Accession No. EF122238) revealed a 100% match with the respective sequence obtained from Genbank for S. bicornis (Accession No. AB193380). A specimen from which these chasmothecia were obtained has been deposited in the U.S. National Fungus Collections (BPI 877328). S. bicornis is a European pathogen of maples, including box elder when grown there (1). Knowledge of the geographic distribution and hosts of Sawadaea powdery mildews in North America is extremely limited. S. bicornis was first reported in North America only recently, occurring in the states of Idaho and Washington on Norway maple (Acer platanoides) (3). The morphologically very similar European powdery mildew pathogen of maples, S. tulasnei, is known only from New York, Ohio, and Montreal, Canada (4), and an unidentified Sawadaea species on box elder has been reported from California (2).

References (1) U. Braun. The Powdery Mildews (Erysiphales) of Europe. Gustav Fischer Verlag, Jena-Stuttgart-New York, 1995. (2) S. Hirose et al. Mycol. Res. 109:912, 2005. (3) C. Nischwitz and G. Newcombe. Plant Dis. 87:451, 2003. (4) J. Weiland and G. Stanosz. Plant Dis. 90:830, 2006.
First Report of Japanese Beetle (Popillia japonica) as a Vector of Southern bean mosaic virus and Bean pod mottle virus
Authors: Wickizer S. L. , Gergerich R. C.
Published: May 2007

The Japanese beetle, Popillia japonica (Coleoptera: Scarabaeidae), was introduced into the United States in New Jersey in 1916 and now commonly occurs in the eastern and mid-western United States. The Japanese beetle has a wide host range and feeds on more than 300 plant species within 79 families (2), but it has not been reported to be a vector of plant viruses. Southern bean mosaic virus (SBMV; genus Sobemovirus) and Bean pod mottle virus (BPMV; family Comoviridae, genus Comovirus) are transmitted by several species of leaf-feeding beetles in the families Coccinelidae and Chrysomelidae (1). Japanese beetles, collected in northwestern Arkansas with a JB Jumbo insect trap (Great Lakes IPM, Inc., Vestaburg, MI), were tested to determine if they are able to transmit SBMV and BPMV. The beetles were given a 24-h acquisition access (individually in plastic petri dishes) to detached trifoliolate leaves of Phaseolus vulgaris ‘Black Valentine’ systemically infected with either BPMV or SBMV. Beetles that had fed on the infected bean leaves (as evidenced by feeding damage to the leaves) were caged individually in clear plastic cups on healthy ‘Black Valentine’ bean seedlings for a 24-h transmission access period. The test plants were grown in the greenhouse for 2 weeks after which they were evaluated for virus infection. In the first trial, BPMV was not transmitted (0 of 11 bait plants with feeding damage), whereas SBMV was efficiently transmitted (6 of 6 bait plants with feeding damage) as determined by agar-gel double-diffusion serology of test plants using polyclonal antibodies to SBMV and BPMV. In a second trial, with a different set of beetles, the transmission rate for BPMV was 3 of 46 (6.5%) and 33 of 43 (77%) for SBMV, and the test plants were evaluated for virus infection using Protein A ELISA. The higher transmission efficiency of SBMV by Japanese beetles when compared with BPMV is characteristic of these two viruses when they are transmitted by other leaffeeding beetles (1). These results are in contrast to an earlier report that Japanese beetles were not able to transmit BPMV from infected soybeans to healthy soybeans in Illinois (3). To our knowledge, this is the first report that the Japanese beetle, an introduced insect with a wide host range in the United States, is a vector of plant viruses.

References: (1) J. P. Fulton et al. Ann. Rev. Phytopathol. 25:111. 1987. (2) D. W. Held. J. Aboricult. 30:328, 2004. (3) T. R. Mabry et al. Plant Dis. 87:1221, 2003.
Branch Dieback of Savin Juniper in Pennsylvania Caused by Diplodia mutila
Authors: Stanosz G. R. , Moorman G. W.
Published: May 2007

Branch dieback of savin juniper (Juniperus sabina L.) was observed on a tree in Dauphin County, PA, in May 1996. The symptomatic tree was in an ornamental planting that had been established approximately 10 years previously. Branches were cankered and girdled, causing yellowing and death of foliage beyond the cankers. Black pycnidia occurred in necrotic bark of cankers. Dark, two-celled conidia obtained from these pycnidia produced pure cultures of Diplodia mutila (Fr.:Fr.) Mont., the anamorph of Botryosphaeria stevensii Shoemaker. The fungus was identified based on pycnidial, conidial, and cultural characteristics, and comparison with known isolates provided by N. A. Tisserat (2). Pathogenicity of a single conidial isolate from Pennsylvania was tested in a greenhouse by wounding and inoculating twigs of potted eastern red cedar (Juniperus virginiana L.) with water agar plugs colonized by mycelium. Cankers formed and enlarged to girdle and kill the inoculated shoots, from which the pathogen was reisolated. No symptoms developed on, nor was the pathogen isolated from, control twigs. B. stevensii has been reported more frequently on angiosperms, such as apple (Malus Mill.) and oak (Quercus L.), than on gymnosperms. However, a canker disease caused by B. stevensii previously has been reported to affect J. scopulorum Sarg. and J. virginiana in Kansas, Missouri, and Iowa (1,2).

References: (1) P. H. Flynn and M. L. Gleason. Plant Dis. 77:210, 1993. (2) N. A. Tisserat et al. Plant Dis. 72:699, 1988.
Occurrence of Downy Mildew on Sunflower in South Africa
Authors: Viljoen A. , van Wyk P. S. , Nowell D. C. , Gulya T. J.
Published: May 2007

Downy mildew, caused by Plasmopara halstedii (Farl.) Berl. & De Toni in Sacc., is an economically important disease of sunflower (Helianthus annuus L.) in Europe and the United States (1). The disease was first noticed in South Africa in a commercial field near Standerton and in a seed production field near Kroonstad during the 1993 to 1994 planting season. During the 1995 to 1996 season, downy mildew was found in experimental hybrids near Heilbron, and in commercial fields near Heil-bron, Marikana, and Potchefstroom. At Heilbron, five hybrids were infected with P. halstedii, whereas three others showed symptoms of downy mildew at Potchefstroom and Marikana. All commercially cultivated hybrids have been developed in South Africa. Disease incidence in all the fields was low, with less than 1% of plants affected by the disease. Diseased plants were dwarfed and displayed veinal chlorosis of leaves typically associated with downy mildew of sunflower. White fungal growth commonly occurred on lower leaf surfaces. Sunflower seedlings inoculated with P. halstedii produced symptoms characteristic of downy mildew. The occurrence of the disease in many geographic areas and on various hybrids in South Africa suggests that the fungus is well established. Recent outbreaks can be attributed to the cool, wet, climatic conditions of the 1993 to 1994 and 1995 to 1996 seasons. The susceptibility of local hybrids suggests that downy mildew is a potentially dangerous disease of sunflower in South Africa.

Reference: (1) J. F. Miller and T. J. Gulya. Crop Sci. 27:210, 1987.
Blueberry Scorch Carlavirus Eliminated from Infected Blueberry (Vaccinium corymbosum) by Heat Therapy and Apical Meristem Culture
Authors: Postman J. D.
Published: May 2007

The incidence of aphid-transmitted blueberry scorch carlavirus (BBSCV) has been increasing in recent years through the blueberry production areas of Oregon and Washington (1). Several infected plants were detected by enzyme-linked immunosorbent assay (ELISA) and removed from the blueberry germ plasm collection at the USDA/ARS National Clonal Germplasm Repository (NCGR) in Corvallis, OR. A virus-free replacement was not available from other sources for one of the infected cultivars. Plants of a highbush blueberry cultivar (Vaccinium corymbosum L. ‘Gem’), infected with BBSCV, were grown at temperatures alternating every 4 h between 30 and 38°C. After 16 or 58 days of heat therapy, apical shoot tips were removed and meristems ranging in size from 0.2 to 1.0 mm were dissected and grown in vitro. Eight plants were successfully regenerated from these meristems: five from shoots that had been heat treated for 16 days and three from shoots heat treated for 58 days. These eight plants were tested for BBSCV by ELISA during the first growing season, and again after growth resumed following winter dormancy. All eight plants consistently tested negative for the virus and Gem is now among the 400 virus-tested Vaccinium clones available at NCGR Corvallis. This is the first report of the successful elimination of BBSCV from infected blueberry plants.

Reference: (1) R. R. Martin and P. R. Bristow. Phytopathology 78:1636, 1988.
First Report of Bacterial Fruit Blotch of Watermelon in Oregon
Authors: Hamm P. B. , Spink D. S. , Clough G. H. , Mohan K. S.
Published: May 2007

Most of the watermelons, Citrullus lanatus (Thunb.) Matsum. & Nakai, consumed in the Pacific Northwest during the summer months are grown in the southern Columbia Basin under dry (<5 cm rainfall), low relative humidity (46 to 57%), and high temperature (29 to 41°C) conditions, using transplants, plastic mulch, and drip irrigation. During May 1996, irregularly shaped, water-soaked lesions were observed on cotyledons and first true leaves of watermelon cv. Sangria transplants growing in a greenhouse. Similar lesions were observed later on older leaves in a commercial field of cv. Millionaire. Microscopic examination of symptomatic tissue revealed bacterial streaming, and isolation on nutrient agar consistently yielded numerous creamy to off-white bacterial colonies. Bacteria from purified, single colonies were Gram negative and rod shaped. Physiological characterization by the Biolog GN Bacterial Identification System (version 3.5) showed a similarity of 0.971 to the Biolog description for Acidovorax avenae subsp. citrulli. Pathogenicity of two strains was confirmed in three separate tests by hypodermic needle infiltration of cotyledons or by stab inoculation into hypocotyls of 12 to 24 21-day-old cv. Crimson Sweet seedlings with aqueous suspensions of bacteria containing approximately 6.0 × 108 CFU/ml. Inoculum was prepared from 48-h-old nutrient agar cultures. Test plants were incubated in the greenhouse at 21°C, under a 16-h photoperiod. Hypocotyl and cotyledon inoculations produced water-soaked lesions within 24 to 48 h on both the hypocotyl and cotyledons or just the cotyledon, respectively, on plants inoculated by either method. No symptoms developed on control plants infiltrated or stabbed with sterile water only. Isolations from three symptomatic seedlings yielded colonies similar in morphology to those used for inoculation. Tests of two purified cultures by Biolog indicated the bacteria were A. avenae subsp. citrulli. The symptomatic test plants were transplanted to fields, and the maturing melons developed large, dark green, water-soaked lesions with irregular margins. Similar fruit symptoms were seen in commercial fields. Labels on seed used in commercial production and in our tests warned of risks related to fruit blotch. This is the first report of bacterial fruit blotch of watermelon in Oregon. This disease may have a significant impact on watermelon production in the Columbia Basin.
Resistance to Stripe Rust in Five Durum Wheat Cultivars
Authors: Ma Hong , Singh Ravi P. , Abdalla Osman
Published: May 2007

Durum wheat (Triticum turgidum) cultivars developed by the International Maize and Wheat Improvement Center (CIMMYT) are currently grown on more than 8 million hectares worldwide. Because of the lack of information on the genetic basis of resistance to stripe rust (caused by Puccinia striiformis), crosses in a diallel arrangement (without reciprocals) were made among five worldwide resistant cultivars and the susceptible cultivar Local Red. Inheritance of resistance was investigated in seedling and adult plant growth stages of F2 populations, and F3lines. The low seedling infection type of each resistant cultivar, namely Kroub 76, Chonta Inia, Sna 3, Syros, and Arena, was based on the additive action of the same two genes. Each of these genes conferred intermediate infection types when present alone. The field resistance of the cultivars was based on the additive action of the two genes identified in the seedlings and one additional, partially effective adult resistance gene. Segregation for plants with stripe rust severities higher than that of the parents in intercrosses of resistant cultivars indicated that some genetic diversity exists for adult genes. The resistance of these cultivars may prove to be long-lasting, since it results from the combined action of at least three genes.
Comparison Between a Culture Plate Method and an Immunoassay to Evaluate Vascular Colonization of Potato by Verticillium dahliae
Authors: Plasencia Javier , Banttari Ernest E.
Published: May 2007

Vascular colonization by Verticillium dahliae of 14 potato (Solanum tuberosum) cultivars was evaluated in field trials by a culture plate method and an indirect competitive enzyme-linked immunosorbent assay (IC-ELISA). Whereas the culture plate technique quantifies fungal propa-gules, the monoclonal antibody-based immunoassay detects the soluble antigen, providing an indicator of fungal biomass. Differences in vascular colonization were evident with both methods; thus, cultivars could be ranked as susceptible, intermediate, or resistant. Linear regression analysis of means of each cultivar showed correlation coefficients (r2) ranging from -0.606 to -0.835. Spearman's rank correlation coefficient (rs) ranged from -0.65 to -0.91. Estimation by IC-ELISA of vascular colonization by V. dahliae in potato is as accurate as that by the culture plate technique, and results can be obtained in 3 days with an approximately 50% reduction in costs of materials and reagents. This quantitative immunoassay can be applied in potato breeding programs to evaluate resistance to Verticillium wilt.
Expression of Inoculum and Family Specific Responses in the Ponderosa Pine-Western Gall Rust Pathosystem
Authors: Walla James A. , Tuskan Gerald A. , Lundquist John E. , Wang Chengguo
Published: May 2007

Host-pathogen interactions in the ponderosa pine-western gall rust pathosystem were studied using seedlings from eight open-pollinated mother-tree families and Peridermium harknessii aeciospores from two geographically separate sources. Pregall symptoms occurred on seedlings by 4 days after inoculation (DAI). Gall occurrence was essentially complete by 230 DAI. Of three measured pigments, light red and dark red pigments on the needles developed most rapidly. Light red pigment on the base of the needles between 21 and 66 DAI was the pregall symptom most often (i) affected by inoculum source and host family, and (ii) correlated to gall width. Pre- and postgall symptoms varied significantly (i) between inocula, and (ii) among mother-tree families. No relationship was found between field resistance ratings of the mother trees and the expression of resistance in their progeny. The inocula varied in pathogenicity, and the seedling families varied in response to infection, as shown by differences in level of incidence and site of development of pigmentation and gall size on inoculated seedlings.
Effect of Dolomitic Lime on Production of Asci and Pseudothecia of Venturia inaequalis and V. pirina
Authors: Spotts R. A. , Cervantes L. A. , Niederholzer F. J. A.
Published: May 2007

An autumn application of dolomitic lime to infected leaves on the orchard floor resulted in a decrease in the percentage of apple and pear leaves with pseudothecia, the number of pseudothecia per leaf, and the number of asci per pseudothecium of Venturia inaequalis and V. pirina. A dolomitic lime application of 5.08 metric tons per hectare reduced the ascospore dose the following spring up to 88% for pear and 92% for apple.
Variation Among Creeping Bentgrass Cultivars in Recovery from Epidemics of Dollar Spot
Authors: Vincelli P. , Doney J. C. , Powell A. J.
Published: May 2007

Dollar spot was allowed to develop from natural inoculum in 15 cultivars of creeping bentgrass (Agrostis palustris) until epidemics were well established. At that time, initial disease intensities were assessed, and one-half of each plot was treated with cyproconazole at 0.3 kg a.i./ha. For each cultivar, disease intensities were assessed 6 to 14 days after treatment in both treated and untreated subplots. Three general patterns of recovery were observed: (i) significant recovery only with fungicide treatment; (ii) some recovery without treatment but greater recovery with treatment; and (iii) equal recovery with or without treatment. Only one cultivar exhibited the same recovery pattern in all 3 years; 10 of 15 cultivars exhibited the same pattern in 2 years of testing. In 1991 and 1993, nearly all cultivars tested recovered more quickly when treated with cyproconazole than when left untreated. In contrast, nearly half of the cultivars in 1992 exhibited the same level of recovery in both treated and untreated subplots. Weather conditions during the 1992 test period were cooler and wetter than during the other years of the study, which probably favored host growth and turfgrass recovery. While some cultivars exhibited partial resistance to dollar spot, no consistent association was found among creeping bentgrass cultivars between the level of partial resistance to, and recuperative ability from, dollar spot. Although the recuperative potential of cultivars varies in different environments, the ability to recover quickly from a disease outbreak could be a valuable cultivar attribute, particularly if it can sometimes occur without a curative fungicide application.
Survey and Characterization of Viruses in Sweetpotato from Zimbabwe
Authors: Chavi Farayi , Robertson A. Ian , Verduin Benedictus J. M.
Published: May 2007

Thirty-one clones of sweetpotatoes collected from some parts of Zimbabwe were used as inoculum sources to mechanically inoculate 13 experimental hosts: Chenopodium amaranticolor, C. quinoa, Cucumis sativus, Datura stramoniumitalic, Gomphrena globosa, Ipomoea purpurea, I. quamoclit, I. rubrocorulea, Nicotiana benthamiana, N. clevelandii, N. glutinosa, N. rustica, and N. tabacum. Systemic vein clearing was observed in N. benthamiana inoculated with buffered sap from nine clones. Purification of the vein clearing inducing agent from one of the sweetpotato clones gave yields ranging from 2 to 17 mg/kg and the A260nm/A280nm was around 1.2. Electron microscopy revealed flexuous filamentous particles with a modal length of 830 nm. Protein analysis of purified virus preparations by sodium dodecyl sulfate polyacrylamide gel electrophoresis revealed a major protein band of 40 kDa, and this was assumed to be the viral coat protein. Minor protein bands of 27, 37, and 46 kDa were also observed. The viral protein degraded upon storage at 4°C over time to yield a protein band of 27 kDa. Polyclonal antiserum was produced against the purified virus. Protein A gold labeling of the purified virus incubated with available antisera; sweetpotato chlorotic stunt virus (SPCSV), sweetpotato feathery mottle virus strain russet crack (SPFMV-RC), sweetpotato feathery mottle virus, sweetpotato mild mottle virus, sweetpotato latent virus, sweetpotato chlorotic fleck virus, and sweetpotato caulimo-like virus resulted in a higher labeling density with the antiserum of SPFMV-RC than with the antiserum of SPCSV, while the other sera did not react. Further characterization of the vein clearing inducing agent was attempted by reverse transcription-polymerase chain reaction amplification of total RNA with degenerate primers for potyviruses and an oligo dT primer and PCR products of correct size were obtained. The nucleotide sequence was determined and the amino acid of the polyprotein deduced. Comparison with other strains of SPFMV showed strong similarity except for an insertion of 22 amino acids at the N-terminus of the coat protein. The coat protein size of 335 amino acids is the biggest SPFMV so far determined.
Survival of Colletotrichum acutatum in Soil and Plant Debris of Leatherleaf Fern
Authors: Norman D. J. , Strandberg J. O.
Published: May 2007

Leatherleaf fern anthracnose is incited by a new pathotype of Colletotrichum acutatum. Fern anthracnose appeared in Florida in 1993, has spread rapidly, and produces losses that approach 100% in some ferneries. To help develop recommendations for control and management of fern anthracnose, the survival of the pathogen in soil and diseased plant material and on clothing was investigated in laboratory and field experiments. Survival of conidia, sclerotia, and conidia in infected leaf debris was studied in soil maintained at five soil moisture levels. Survival of conidia and sclerotia declined rapidly under moist conditions (≥12% moisture, vol/wt), but under dry conditions, viable conidia could be detected up to 12 months after incorporation into soil. Similar results were obtained in field experiments in which infected leaf debris was buried in soil. Viable conidia were recovered for up to 3 months in leaf debris stored under laboratory conditions. Conidia applied to denim fabric were recovered up to 5 weeks after application. This indicated that contaminated clothing could transport conidia effectively within and between ferneries. Inoculating ferns with dilutions of conidia demonstrated that at least 100 conidia per ml is required to infect and colonize leatherleaf fern leaves. This threshold provides an estimate of levels of conidia populations likely to result in disease and levels that sanitation or cultural practices must exceed to be effective management methods.