bluuebunny/crossref_metadata_2025 huggingface dataset:
Breakdown of Cross-Protection of Grapefruit from Decline-Inducing Isolates of Citrus tristeza virus Following Introduction of the Brown Citrus Aphid
Authors: Powell C. A. , Pelosi R. R. , Rundell P. A. , Cohen M.
Published: May 2007

A 21-year-old replicated field planting of 84 ‘Ruby Red’ grapefruit trees cross-protected with three mild isolates of Citrus tristeza virus (CTV) was assessed for decline-inducing and non-decline-inducing isolates of the virus 5 years after the brown citrus aphid (BrCA) (Toxoptera citricida Kirkaldy) first was established in the experimental area. Prior to the introduction of the BrCA, the cross-protecting mild isolates had significantly reduced detectable infection with decline-inducing isolates of CTV for 16 years (average infection of 13% in cross-protected trees compared with 67% in unprotected trees). After the introduction of the BrCA, infections with decline-inducing CTV (measured by enzyme-linked immunosorbent assay) were 57, 81, and 71% for trees protected with three mild isolates, respectively, compared with 95% in unprotected trees. These results suggest that the introduction of BrCA accelerated the breakdown of cross-protection against decline-inducing isolates of CTV in grapefruit.
Temperature-Sensitive Reaction of Winter Wheat Cultivar AGSECO 7853 to Stagonospora nodorum
Authors: Kim Yong-Ki , Bockus William W.
Published: May 2007

Stagonospora blotch is an important foliar and head disease of wheat (Triticum aestivum) in many regions of the world. To determine the reaction of winter wheat cultivars to Stagonospora blotch at different temperatures, seedlings of the hard winter wheat cvs. Newton, AGSECO 7853, and Heyne were inoculated with three isolates of Stagonospora nodorum and exposed to three temperature regimes (high, 29 and 21°C [day and night]; medium, 25 and 17°C; and low, 18 and 10°C). Heyne was resistant at all temperatures in all three experiments. The reaction of AGSECO 7853, when averaged over all isolates, was intermediate between Heyne and Newton at high temperature, as susceptible as Newton at medium temperature, but more susceptible than Newton at low temperature. Therefore, the reaction of AGSECO 7853 relative to Newton was temperature sensitive. This finding is important in the evaluation of wheat lines for resistance to Stagonospora blotch because the relative ranking of one cultivar may differ from another depending upon the temperature.
First Report of White Mold Caused by Sclerotinia sclerotiorum on Persian Buttercup (Ranunculus asiaticus) in Italy
Authors: Garibaldi A. , Minuto A. , Gullino M. L.
Published: May 2007

Persian buttercup (Ranunculus asiaticus L.) is grown in the Albenga Region of northern Italy for cut flower production and exportation to central and northern Europe. During the winter of 2003, sudden wilt was observed in commercial plantings of R. asiaticus. Initial symptoms included stem necrosis at the soil level and yellowing and tan discoloration of leaves. As stem necrosis progressed, infected plants wilted and died. Wilt occurred within a few days on young plants and was characterized by the presence of soft and watery tissues. Necrotic tissues became covered with whitish mycelium that produced dark, spherical sclerotia (1 to 4 mm in diameter). Sclerotinia sclerotiorum (Lib.) de Bary (1) was consistently recovered from infected stem pieces of R. asiaticus that were disinfested for 1 min in 1% NaOCl and plated on potato dextrose agar (PDA) amended with 100 ppm of streptomycin sulfate. Pathogenicity of three isolates obtained from infected plants of persian buttercup was confirmed by inoculating 30-day-old plants grown in containers. Inoculum that consisted of wheat kernels infested with mycelium and sclerotia of each isolate was placed on the soil surface around the base of each of five plants. Noninoculated plants served as controls. The inoculation trial was repeated once. All plants were kept at temperatures ranging between 8 and 22°C and watered as needed. Inoculated plants developed symptoms of leaf yellowing followed by wilt within 15 days, while control plants remained symptomless. White mycelium and sclerotia developed on infected tissues, and S. sclerotiorum was reisolated from inoculated plants. S. sclerotiorum has been previously reported on R. asiaticus in the United States (2) and Japan (3). To our knowledge, this is the first report of wilt of R. asiaticus caused by S. sclerotiorum in Italy and Europe.

References: (1) N. F. Buchwald. Den. Kgl. Veterin.er-og Landbohojskoles Aarsskrift, 1949. (2) D. F. Farr et al. Fungi on Plants and Plant Products in the United States. The American Phytopathological Society, St. Paul, MN, 1989. (3) T. Urushibara et al. Annu. Rep. Kanto-Tosan Plant Prot. Serv. 46:61, 1999.
Current Status and Newly Discovered Natural Hosts of Tomato infectious chlorosis virus and Tomato chlorosis virus in Spain
Authors: Font M. I. , Juárez M. , Martínez O. , Jordá C.
Published: May 2007

Tomato chlorosis virus (ToCV) and Tomato infectious chlorosis virus (TICV) are emergent whitefly-transmitted criniviruses. ToCV and TICV were detected in Spain in 2000 (2) and 2001 (1), respectively. Both viruses infect tomato (Lycopersicon esculentum Mill) crops and cause symptoms of foliar chlorosis. ToCV is prevalent along the southern and eastern regions of Spain (provinces of Sevilla, Málaga, Almería, Murcia, Alicante, and Castellón), Balearic (Mallorca), and the Canary Islands (Tenerife and Gran Canaria). However, TICV only has been detected in the provinces of Murcia, Alicante, and Castellón in Spain. During the summer and autumn of 2002, abnormal interveinal reddening, yellowing symptoms, or both, were observed in plants of Chenopodium album L., C. murale L., and Solanum nigrum L. growing in or around tomato fields in Murcia and Almería provinces. To study the alternative hosts that may serve as virus reservoirs in areas where these viruses are prevalent, 62 samples of 42 common weed species were analyzed by reverse transcription-polymerase chain reaction using specific primers for ToCV and TICV (1). The 439-bp ToCV-specific DNA fragment was amplified in two S. nigrum samples from Alicante and Murcia provinces, and the 501-bp TICV-specific DNA fragment was amplified in one C. murale sample from Murcia, as well as in three C. album samples from Murcia and Alicante provinces. The DNA fragment amplified from the ToCV isolate was sequenced and showed 99 to 98% identity with the ToCV isolates (GenBank Accession Nos. AY048854 and AF234029) from Italy and Portugal, respectively. The DNA fragment amplified from TICV isolates were sequenced and showed 98% identity with the TICV isolate from Spain (GenBank Accession No. AF479662), confirming the diagnosis. Although the number of samples is not sufficient to conclude that we know, in a precise way, the role of weed reservoirs in TICV and ToCV epidemics in Spain, this study might contribute to a better understanding of the epidemiology of these viruses. To our knowledge this is the first report of these weeds as natural hosts of ToCV and TICV in Spain.

References: (1) M. I. Font et al. Plant Dis. 86:696, 2002. (2) J. Navas-Castillo et al. Plant Dis. 84:835, 2000.
Strawberry latent ringspot virus Infecting Roses in India
Authors: Kulshrestha S. , Hallan V. , Raikhy G. , Ram R. , Zaidi A. A.
Published: May 2007

Rose is an economically important crop of India and the world. A survey of rose plantations in and near the Kangra Valley of Himachal Pradesh, India, showed virus-like symptoms, including yellow flecking in young leaves and reduction in leaflet size, while some were symptomless. These symptoms are similar to those for Strawberry latent ringspot virus (SLRSV) (1). Sap inoculation from symptomatic and some symptomless leaves to Chenopodium amaranticolor resulted in chlorotic local lesions followed by systemic chlorosis. SLRSV was detected in this indicator host and six rose cultivars (Happiness, Iceberg, First Prize, Ganga, Pink Panther, and Oklahoma) showing characteristic symptoms of SLRSV using enzyme-linked immunosorbent assay (ELISA) with ELISA kit (DSMZ, Braunschweig, Germany). Reverse transcription-polymerase chain reaction was performed with SLRSV-specific primers (2), and a product of the expected size of ˜181 bp was amplified. The authenticity of the fragment was confirmed by sequencing. Isolated SLRSV was also inoculated to seed-grown rose seedlings and after 20 days postinoculation the same symptoms (yellow flecking in young leaves) were observed. These results established the identity of the virus that caused yellow flecking on rose leaves in India as SLRSV. To our knowledge, this is the first report of SLRSV infecting rose in India.

References: (1) A. F. Murant. Strawberry latent ringspot virus. No. 126 in: Description of Plant Viruses, CMI/AAB, Surrey, U.K., 1974. (2) E. Bertolini et al. J. Virol. Methods 96:33, 2001.
Physiologic Specialization of Puccinia triticina on Wheat in the United States in 2002
Authors: Kolmer J. A. , Long D. L. , Hughes M. E.
Published: May 2007

Collections of Puccinia triticina were obtained from rust-infected wheat leaves by cooperators throughout the United States and from surveys of wheat fields and nurseries in the Great Plains, Ohio Valley, Southeast, California, and the Pacific Northwest, in order to determine the virulence of the wheat leaf rust fungus in 2002. Single uredinial isolates (785 in total) were derived from the wheat leaf rust collections and tested for virulence phenotype on lines of Thatcher wheat that are near-isogenic for leaf rust resistance genes Lr1, Lr2a, Lr2c, Lr3, Lr9, Lr16, Lr24, Lr26, Lr3ka, Lr11, Lr17, Lr30, LrB, Lr10, Lr14a, and Lr18. In the United States in 2002, 52 virulence phenotypes of P. triticina were found. Virulence phenotype MBDS, which is virulent to resistance gene Lr17, was the most common phenotype in the United States. MBDS was found in the Southeast, Great Plains, and the Ohio Valley regions, and also in California. Phenotype MCDS, virulent to Lr17 and Lr26, was the second most common phenotype and occurred in the same regions as MBDS. Virulence phenotype THBJ, which is virulent to Lr16 and Lr26, was the third most common phenotype, and was found in the southern and northern central Great Plains region. Phenotype TLGJ, with virulence to Lr2a, Lr9, and Lr11, was the fourth most common phenotype and was found primarily in the Southeast and Ohio Valley regions. The Southeast and Ohio Valley regions differed from the Great Plains regions for predominant virulence phenotypes, which indicate that populations of P. triticina in those areas are not closely connected. The northern and southern areas of the Great Plains were similar for frequencies of predominant phenotypes, indicating a strong south to north migration of urediniospores.
Viability of Sirococcus clavigignenti-juglandacearum Conidia on Exoskeletons of Three Coleopteran Species
Authors: Stewart J. E. , Halik S. , Bergdahl D. R.
Published: May 2007

Butternut canker, caused by Sirococcus clavigignenti-juglandacearum, is the primary cause of decline of butternut (Juglans cinerea). Conidia of the fungus have been isolated from several insect species. The vector potential of three species of Coleoptera, Astylopsis macula, Eubulus parochus, and Glischrochilus sanguinolentus, was studied during 2001 and 2002. Beetles were collected, rinsed, and artificially inoculated with conidia. All three species carried viable conidia up to 16 days. The mean number of conidia carried per beetle in 2001 was as follows: 3.21 million at 0 h to 11,371 at 384 h for A. macula; 3.91 million at 0 h to 57 at 384 h for E. parochus; and 355,742 at 0 h to 314 at 384 h for G. sanguinolentus. In 2002, the numbers were: 1.42 million at 0 h to 2,814 at 384 h for A. macula; 1.29 million at 0 h to 85 at 384 h for E. parochus; and 72,342 at 0 h to 0 at 192 h for G. sanguinolentus. Using scanning electron microscopy, conidia were observed on the abdomen, thorax, and legs of artificially inoculated individuals of each species and on the thorax and abdomen of field-collected A. macula and E. parochus. These data suggest that all three species are potential vectors of S. clavigignenti-juglandacearum; however, A. macula and E. parochus may be more effective vectors.
Control of Potato Tuber Rots Caused by Oomycetes with Foliar Applications of Phosphorous Acid
Authors: Johnson Dennis A. , Inglis Debra A. , Miller Jeffrey S.
Published: May 2007

Phosphorous acid for control of tuber rots caused by Phytophthora infestans, P. erythroseptica, and Pythium ultimum was applied to foliage of potato cultivars at various application timings and rates under growing conditions in the Pacific Northwest at Othello and Mount Vernon, WA, and Bonners Ferry and Aberdeen, ID in 2001 to 2003. Efficacy was assessed by artificially inoculating harvested tubers. Mean incidence and severity of late blight tuber rot in tubers inoculated with US-8 and US-11 isolates of Phytophthora infestans usually were significantly less when the foliage from which the tubers were obtained was treated with phosphorous acid than when it was not treated at all locations. With two applications of phosphorous acid, late blight tuber rot in the tuber-resistant cv. Umatilla Russet was significantly less than for Ranger Russet. For phosphorous acid at a rate of 9.37 kg a.i./ha, late blight tuber rot control achieved with two applications at 2-week intervals was not consistently improved across locations by making an additional application 2 weeks later. In 2003, incidence and severity of late blight tuber rot did not differ significantly between the rates of 7.49 and 9.37 kg a.i./ha at both Othello and Mount Vernon. Late blight tuber rot incidence and severity were significantly less at a rate of 7.49 kg a.i./ha when the application schedule began at initial tuber bulking rather than when the first application was made 4 weeks after initial tuber bulking at Othello, but not Mount Vernon. Incidence of pink rot was significantly less in inoculated tubers from plots treated with three applications of phosphorous acid than in tubers from nontreated control plots at Mount Vernon in 2002 and 2003, Bonners Ferry in 2002, and Aberdeen in 2003. Pink rot severity was reduced significantly by both two and three phosphorous acid applications at Mount Vernon in 2002. Pink rot incidence, but not severity, was reduced significantly at all timings when either 7.49 or 9.37 kg a.i./ha was applied at Mount Vernon in 2003. Control of Pythium spp. by phosphorous acid was not evident in this study. Total tuber yield at harvest did not differ significantly among the phosphorous acid treatments and the nontreated control at Othello and Mount Vernon in 2001 and 2002.
First Report of Botrytis cinerea on Pansy Flowers in Buenos Aires
Authors: Rivera M. C. , Lopez S. E.
Published: May 2007

Pansy (Viola × wittrockiana) is an ornamental annual plant produced as a potted plant in greenhouses around Buenos Aires, Argentina. Flower rot with signs of gray mold was observed on pansy cv. Crown during the autumn of 2003. Diseased tissues were surface sterilized by immersion in 2% NaOCl for 1 min, placed on 2% potato dextrose agar (PDA), and incubated at 22°C. Fungal mycelia were initially white and became gray after 72 h. After 4 days, colonies were 4 cm in diameter and sporulated profusely. Black sclerotia developed after 7 days. Mycelia were septate with dark branched conidiophores bearing unicellular, ellipsoid, hyaline conidia that measured 8 to 12 × 6 to 8 μm in botryose heads. These characteristics agree with Botrytis cinerea Pers.:Fr. (1). Pathogenicity tests were performed by spraying 10 healthy pansy plants during bloom with 3 ml of a conidial suspension (106 conidia per ml) per plant. Controls were treated with sterilized distilled water only. Plants were covered with plastic bags for 2 days and incubated at 18 to 22°C. The flowers developed water-soaked lesions between 4 and 6 days after inoculation. Fifty percent of the flowers were pendulous because flower blight reached the peduncle. The pathogen was reisolated from diseased flowers after superficial sterilization with 2% NaOCl and isolated on PDA. Gray mold has a rapid development during bloom, and the pathogen was able to enter undamaged flower tissues. No disease symptoms were observed on leaves. This report adds pansy as a new host of B. cinerea to a previous list of ornamentals grown in Argentina where gray mold was observed.

Reference: (1) M. V. Ellis and J. M. Waller. Sclerotinia fuckeliana (condial state: Botrytis cinerea). No. 431 in: Descriptions of Pathogenic Fungi and Bacteria, CMI, Kew, Surrey, UK, 1974.
First Report of Phytophthora cinnamomi on Ilex glabra in Virginia
Authors: Moorman G. W. , Hong C. X. , Richardson P. A.
Published: May 2007

During 2002, two nurseries in southeastern Virginia reported losses exceeding 75% of container-grown inkberry holly (Ilex glabra) cv. Shamrock. The development of necrotic leaf spots and blotches followed initial symptoms of leaf yellowing and wilting. Affected leaves rapidly turned brown and fell. Dark brown-to-black roots were washed and plated on agar media. Phytophthora cinnamomi Rands was consistently isolated and identified on the basis of its morphology (2) and single-stranded conformational polymorphism fingerprint (1). The organism had nonpapillate, internally proliferating, noncaducous, ovoid to ellipsoid sporangia that formed only in water. It did not grow at 35°C and had abundant botryose hyphal swellings, coralloid hyphae, and grape-like clusters of chlamydospores. The isolate, determined to be the A2 mating type, produced elongate cylindrical, amphigynous antheridia and oogonia with a tapered base. A pine bark potting mix amended with V8 juicetreated vermiculite colonized by the suspected pathogen was placed in 12-liter containers. Two inkberry holly cv. Shamrock liners were planted in each of three containers and two 1-yr-old plants were planted in each of three additional containers during April 2004. An identical set of six containers of noninoculated plants was also established. During June 2004, inoculated plants exhibited symptoms identical to those observed in nurseries, and P. cinnamomi was isolated. Noninoculated check plants did not develop symptoms. Japanese holly (I. crenata) was previously known as a host, but to our knowledge, this is the first report of inkberry holly (I. glabra) susceptibility.

References: (1) P. Kong et al. Fungal Genet. Biol. 39:238, 2003. (2) D. J. Stamps et al. Mycol. Pap. No. 162. CAB International Mycological Institute, Wallingford, UK, 1990.
Histopathology of Red Stripe of Rice
Authors: Kaku Hisatoshi
Published: May 2007

A histological study of red stripe of rice was conducted to elucidate the mode of infection of the causal bacterium Microbacterium sp. When pin-point-sized spots first appeared at 3 days after inoculation, the bacterial cells had entered through stomata and multiplied in the intercellular spaces of substomatal parenchymatous tissues. With the early appearance of small yellow spots at 4 to 5 days after inoculation, the bacterium was detected in some xylem vessels as well as in parenchymatous tissues, and it had apparently translocated directly from parenchymatous tissues to transverse vascular systems through spiral vessel walls. With the appearance of typical red stripe symptoms comprised of orange lesions and halos at 8 days after inoculation, bacterial masses were present in transverse and longitudinal vascular bundles in areas with orange lesions. In the areas with orange to light brown spots, granules that stained dark blue using Stoughton's method appeared in the protoplasm of the host parenchymatous cells, which later became necrotic. In halo areas, bacterial masses were observed only in some cases, and chloroplasts were disorganized. Bacterial infection was also confirmed by observing sections of naturally infected samples, and the distribution of bacteria was much more extensive than in artificially inoculated samples.
First Report of Cucumber mosaic virus in Eryngium yuccifolium (Rattlesnake Master) in Ohio
Authors: Whitten K. R. , Nameth S. G. P.
Published: May 2007

Rattlesnake master (Eryngium yuccifolium) is a wildflower that is native to Ohio. In recent years, native wildflowers have become very popular with home gardeners, and conservationists have begun to reestablish these plants in their native ranges. As native perennial wildflowers become more common, it is important to determine if they might serve as possible perennial reservoirs of viruses. A plot of 20 species native to Ohio was established on the Waterman Agricultural and Natural Resources Laboratory, The Ohio State University, Columbus, Ohio. In the summers of 1999 and 2001, random samples were collected from established plantings. Some sampled plants did not show symptoms of virus infection; however, all samples of E. yuccifolium appeared chlorotic, slightly mottled, and stunted. Using double-stranded RNA (dsRNA) analysis (1), these plants were assayed for viral infection. dsRNA profiles obtained from symptomatic E. yuccifolium resembled that of Cucumber mosaic virus (CMV). These results were confirmed with an enzyme-linked immunosorbent assay (ELISA; Agdia Inc., Elkhart, IN) for CMV. dsRNA-containing samples of E. yuccifolium produced ELISA absorbance values (A405) of 0.231 to 0.713 when compared with the negative control. All 14 samples of E. yuccifolium tested positive for CMV. To our knowledge, this is the first report of CMV in E. yuccifolium, which should serve as the basis for a more extensive survey, since CMV can potentially infect a wide variety of ornamental and nonornamental hosts.

Reference: (1) R. Valverde et al. Plant Dis. 74:255, 1990.
Benomyl Sensitivity of Isolates of Colletotrichum acutatum and C. gloeosporioides from Citrus
Authors: Peres N. A. R. , Souza N. L. , Peever T. L. , Timmer L. W.
Published: May 2007

Postbloom fruit drop (PFD) of citrus, caused by Colletotrichum acutatum, produces orange-brown lesions on petals and results in premature fruit drop and the retention of calyces. C. gloeosporioides is common in groves and causes postharvest anthracnose on fruit. Both diseases are controlled effectively by the fungicide benomyl in research fields and commercial orchards. Highly sensitive and resistant isolates of C. gloeosporioides were found, whereas all isolates of C. acutatum tested were moderately resistant. In preliminary studies conducted in vitro with three isolates of each, mycelial growth of sensitive isolates of C. gloeosporioides was inhibited completely by benomyl (Benlate 50 WP) at 1.0 μg/ml, whereas resistant isolates grew well at 10 μg/ml. Growth of all isolates of C. acutatum was inhibited by about 55% at 0.1 μg/ml and by 80% at 1.0 μg/ml. Spore germination of C. acutatum was inhibited more at 0.1 μg/ml than at 1.0 μg/ml or higher concentrations. In all, 20 isolates of C. acutatum from 17 groves and 20 isolates of C. gloeosporioides from 7 groves were collected from locations with different histories of benomyl usage in São Paulo, Brazil, and Florida, United States. Benomyl at 1.0 μg/ml completely inhibited growth of 133 isolates of C. gloeosporioides, with the exception of 7 isolates that were highly resistant to the fungicide, whereas all isolates of C. acutatum were only partially inhibited at 0.1 and 1.0 μg/ml. Analysis of variance indicated that the sensitivity of the isolates of C. acutatum was not affected by benomyl usage or grove of origin, and country of origin had only minor effects. No highly resistant or sensitive isolate of C. acutatum was recovered. Partial sequencing of the β-tubulin gene did not reveal nucleotide substitutions in codons 198 or 200 in C. acutatum that usually are associated with benomyl resistance in other fungi.
Seedling Resistance Genes to Leaf Rust in Soft Red Winter Wheat
Authors: Wamishe Yeshi A. , Milus Eugene A.
Published: May 2007

Seedling and adult-plant resistance have been used to manage leaf rust, caused by Puccinia triticina, but there is little information on resistance genes in contemporary cultivars and advanced breeding lines of soft red winter wheat (Triticum aestivum). Lack of information on the genetic basis for resistance leads to uncertainty about durability of resistance and makes pyramiding resistance genes more difficult. The objective of this study was to determine the genetic basis for race-specific seedling resistance to leaf rust among the 116 contemporary lines from the 1998-99 Arkansas Wheat Cultivar Performance Test and the Uniform Eastern and Southern Soft Red Winter Wheat Nurseries. To postulate the presence of genes for leaf rust resistance (Lr genes), seedlings of each line and 24 isolines in a Thatcher background were evaluated for infection type in growth chambers at 22/18°C (day/night) or constant 17 or 18°C using 22 races of P. triticina. A computer program was used to analyze infection type data and facilitate identification of Lr genes. Genes Lr1, 2a, 2c, 3, 3ka, 9, 10, 11, 14a, 18, 20, 23, 24, and 26 were identified among the lines tested. Genes Lr3, 10, and 11 were the most common. Genes Lr15, 28, and 30 were postulated as possibly present in some lines but were not likely to be important among the lines. Genes Lr16, 17, 21, 32, 36, 38, and 39 were not detected. Fifty-four lines had one or more unidentified Lr genes that were not included in the set of 24 isolines. Only four lines (Agripro Marion, APD94-5282, NC94-7197, and VA97W-375) were resistant to all races used in this study, and these were postulated to have the combination of Lr9, 24, and 26.
Effects of Choline, Betaine, and Wheat Floral Extracts on Growth of Fusarium graminearum
Authors: Engle Jessica S. , Lipps Patrick E. , Graham Terry L. , Boehm Michael J.
Published: May 2007

Fusarium head blight has been more severe when infection occurs during anthesis, indicating that floral organs may be important infection courts. Choline acetate and glycinebetaine have been extracted from wheat and reported to be growth stimulants of Fusarium graminearum. They are hypothesized to enhance infection and tissue colonization. Growth of F. graminearum was examined on media amended with extracts from floral parts of nine wheat genotypes with various Fusarium head blight resistance levels. Results indicated no significant effect of anther, palea, or lemma extracts on radial growth when compared with unamended controls. Effects on spore germination and hyphal growth of F. graminearum by choline, betaine, and an equimolar mixture at concentrations ranging from 0.01 to 1,000 μM also were examined. Spore germination was not significantly (P ≤ 0.05) affected by choline, betaine, or a combination of the compounds compared with unamended controls. Radial hyphal growth also was not consistently affected (P ≤ 0.05) by choline or betaine when compared with controls. Equimolar mixtures of the two compounds showed significant slight reduction in growth rate at higher concentrations when compared with controls. The reduction in growth rate was due to higher concentrations of betaine. Results of this study indicate that endogenous compounds in floral parts may not be associated with wheat resistance to F. graminearum.
Response of Chile Pepper to Phytophthora capsici in Relation to Soil Salinity
Authors: Sanogo S.
Published: May 2007

The response of chile pepper to salinity and infection by Phytophthora capsici was assessed under greenhouse conditions in plants susceptible or resistant to P. capsici. Additionally, the effect of salinity on mycelial growth and production of sporangia and zoospores by P. capsici was evaluated in the laboratory. Salinity treatments consisted of varying levels of electrical conductivity (from 1.8 to 14.4 dS/m) achieved by amending irrigation water or growth media with a mixture of sodium chloride and calcium chloride. In plants susceptible to P. capsici, disease severity increased by approximately 1.3 to 2.7-fold with increasing salinity level, whereas no such effect was observed in plants resistant to P. capsici. Mycelial dry weight increased by 8 to 16%, and radial growth of mycelium was augmented by 5 to 30% with increase in salinity level. Production of sporangia and zoospore formation were reduced by approximately 3 to 85 and 1 to 93%, respectively, under saline conditions. These results indicate that salinity may predispose susceptible chile pepper plants to infection by P. capsici.
Development and Field Evaluation of a Model to Estimate the Maturity of Pseudothecia of Pleospora allii on Pear
Authors: Llorente I. , Montesinos E.
Published: May 2007

The effect of temperature and of two levels of relative humidity (RH) on maturity of pseudothecia of Pleospora allii (teleomorph of Stemphylium vesicarium) was studied under controlled environmental conditions at temperatures of 5, 10, 15, 20, 25, and 30°C and high (≥98%) and low (≈60%) RH. Pseudothecia developed only at high RH, and the optimum temperature was between 10 and 15°C. A regression model of the form ln(1/1 − y) = 0.12550 + 0.005048x, which related the proportion of mature pseudothecia (y) to cumulative degree-days (x), was developed with data from two controlled environment experiments. Maturation of pseudothecia also was studied in leaf debris in pear orchards affected by brown spot of pear in seven field trials during 4 years. Asci with mature ascospores were observed in leaf debris from mid-January to May. A significant linear relationship was observed between the predicted values according to the monomolecular model and observed values of the percentage of mature pseudothecia in the field trials (r 2 = 0.91, intercept=8.718, and slope=0.903). This model can be used to predict the onset of ascospore discharge and for determining the initiation of fungicide applications to control the primary inoculum and prevent primary infections.
Iris Yellow Spot Virus in Onion Bulb and Seed Crops in Washington
Authors: du Toit L. J. , Pappu H. R. , Druffel K. L. , Pelter G. Q.
Published: May 2007

The geographic distribution of Iris yellow spot virus (IYSV, Genus Tospovirus, Family Bunyaviridae) in onion (Allium cepa L.) crops in the western United States has increased with the most recent report in Colorado (1,4). Furthermore, the incidence of IYSV has increased significantly in onion crops in the Treasure Valley of southern Idaho and eastern Oregon, where the disease was first detected in the United States (1,2). Surveys of onion seed crops in Washington during the past 2 years showed the presence of plants with symptoms characteristic of IYSV infection, including distinct diamond-shaped chlorotic or necrotic lesions, as well as indistinct circular to irregular, chlorotic or necrotic lesions of various sizes on the scapes of flowering plants. To date, symptomatic plants have been observed in five seed crops in Washington, at incidences ranging from <1% to approximately 20% in individual seed crops. Enzyme-linked immunosorbent assays carried out directly on symptomatic onion samples collected in July 2002, and on Nicotiana benthamiana plants mechanically inoculated with sap from these symptomatic plants, did not detect the presence of IYSV. In late July 2003, symptomatic plants were collected from an onion seed crop in Grant County and tested for IYSV infection by reverse transcription-polymerase chain reaction (RT-PCR). Total nucleic acid was extracted from symptomatic areas of the scapes with the procedure described by Presting et al. (3). Primers specific to the nucleocapsid (NP) gene of IYSV were designed based on sequences in GenBank: 5′-TCA GAA ATC GAG AAA CTT-3′ and 5′-TAA TTA TAT CTA TCT TTC TTG G-3′ (sense and antisense polarity, respectively). The RT-PCR assay produced an amplicon of the expected size (approximately 700 bp) that was cloned and sequenced. Comparison with the GenBank IYSV gene sequences showed 98% sequence identity of the NP gene. In August 2003, symptoms of IYSV infection were observed in two onion bulb crops, each located within 2 miles of the symptomatic onion seed crop in Grant County. The presence of IYSV in these crops was confirmed by RT-PCR with cloning and sequencing of the amplicon, as described for the seed crop samples. To our knowledge, this is the first confirmation of IYSV in onion bulb and seed crops in Washington, where 16,000 to 18,000 acres of onion bulb crops and 700 to 900 acres of onion seed crops are grown annually (USDA National Agricultural Statistics Service). The increase in prevalence of IYSV in the Pacific Northwest highlights the need for additional research to clarify the epidemiology of this potentially significant pathogen and to develop a regional management program for iris yellow spot.

References: (1) J. M. Hall et al. Plant Dis. 77:952, 1993. (2) J. W. Moyer et al. (Abstr.) Phytopathology 93(suppl.):S115, 2003. (3) G. G. Presting et al. Phytopathology 85:436, 1995. (4) H. F. Schwartz et al. Plant Dis. 86:560, 2002.
First Report of Xylella fastidiosa Associated with Leaf Scorch in Black Oak in Washington, D.C.
Authors: Huang Q.
Published: May 2007

Bacterial leaf scorch caused by Xylella fastidiosa has been reported in 17 species of oak including bur, pin, red, scarlet, shingle, and white oaks (3). In September 2002, a leaf scorch symptom characterized by marginal necrosis of leaves bordered by a darker brown band was observed in a mature black oak (Quercus velutina Lam.) at the U.S. National Arboretum in Washington, D.C. The leaf petiole of the black oak was processed in general extraction buffer (Agdia, Inc., Elkhart, IN) contained in a FastDNA lysing matrix tube using the FastPrep FP120 instrument (Qbiogene, Inc., Carlsbad, CA) (1). The leaf petiole extract reacted with an antiserum specific for X. fastidiosa (Agadia, Inc.) in an enzyme-linked immunosorbent assay (ELISA). A slow-growing bacterium was cultured from leaf petioles of the affected black oak tree by soaking the surface-sterilized, finely cut leaf petioles in sterile water for 30 min, followed by spreading the bacterial suspension on periwinkle wilt plates (1). When the cultured bacterium was subjected to polymerase chain reaction (PCR) with primers specific for X. fastidiosa (2), a 472-bp PCR product was detected. The PCR product was confirmed to be the predicted X. fastidiosa product by sequencing and sequence comparison with the reported genomic sequence of X. fastidiosa. ELISA and bacterial isolation from leaf petioles of a nearby symptomless white oak (Q. alba L.) tree were negative. To our knowledge, this is the first report of X. fastidiosa associated with leaf scorch in black oak in the United States, expanding the host range of the bacterium in economically important landscape tree species.

References: (1) Q. Huang and J. L. Sherald. Curr. Microbiol. 48:73, 2004. (2) M. R. Pooler and J. S. Hartung. Curr. Microbiol. 31:377, 1995. (3) J. L. Sherald. Xylella fastidiosa, A bacterial pathogen of landscape trees. Page 191 in: Shade Tree Wilt Diseases, C. L. Ash, ed. The American Phytopathological Society, 2001.
Effect of Inoculum Density of Sclerotium cepivorum on the Ability of Trichoderma koningii to Suppress White Rot of Onion
Authors: Metcalf D. A. , Dennis J. J. C. , Wilson C. R.
Published: May 2007

Amendment of soil with Trichoderma koningii strain Tr5 grown on autoclaved white millet grain provided between 63 and 79% control of white rot of onion when added to soil containing 10, 25, 50, or 100 sclerotia of Sclerotium cepivorum per kilogram of soil at the time of onion seed sowing. There was no significant difference in the proportion of S. cepivorum infections suppressed among the different sclerotial density treatments. Rhizosphere colonization by T. koningii Tr5 was assessed by incubating onion roots sampled from plants growing in soil with the appropriate density of sclerotia, on a Trichoderma selective medium (Rose bengall-Allisan-streptomycin-Previcur agar) developed for the purpose of the study. Trichoderma spp. isolated were typed by comparison of culture morphology as well as polygalacturonase (PG) (EC 3.2.1.15) and pectinesterase (PE) (EC 3.1.1.11) isozyme profiles to the series of one PG and two PE isozymes known to be produced by T. koningii Tr5. The method was used successfully to assess rhizosphere colonization. Three rates of a millet grain formulation colonized by T. koningii Tr5 were added to soil (1,590, 3,180, and 4,770 kg/ha). At the lowest of these rates, 97% of roots were found to be colonized by isolates which could not be distinguished from T. koningii Tr5, whereas 8% of the roots from nontreated controls were colonized by such isolates. An objective of the study was to determine whether the ability of T. koningii Tr5 to suppress S. cepivorum infections was influenced by increased concentrations of both S. cepivorum sclerotia and T. koningii Tr5-colonized millet grain, and it was found that no further improvements in the percentage of disease suppression were recorded as a result of adding T. koningii Tr5-colonized millet to the soil at more than 1,590 kg/ha at any of the sclerotium concentrations tested.
Effect of Temperature on Sporulation of Botryosphaeria dothidea, B. obtusa, and B. rhodina
Authors: Copes W. E. , Hendrix F. F.
Published: May 2007

Three Botryosphaeria spp. were grown on autoclaved apple and peach stems in cotton-plugged tubes with constant moisture at 6, 12, 18, 24, and 30°C to determine the effect of temperature on sporulation. Number of conidia per pycnidium was determined weekly from 4 to 10 weeks after inoculation. The experiment was repeated three times. Maximum sporulation occurred at 24°C with B. dothidea and at 18 and 24°C with B. obtusa. Spore production of both fungi showed a quadratic curvilinear response to temperature. Pycnidia were erumpent, typical of their habit in nature. Maximum sporulation of B. rhodina occurred at 12, 24, and 30°C instead of at a distinctive peak. Of the three fungi, B. rhodina produced the greatest number of conidia per pycnidium at all temperatures. Mycelia and pycnidia of B. rhodina grew on top of the bark, which is atypical of their habit in nature. For spore production by B. dothidea, there was a significant interaction between temperature and time. Maximum sporulation over the 10-week period occurred in week 4 and/or 6 for B. dothidea at 12, 18, and 24°C, with a linear response at 12 and 24°C (P ≤0.05). Conidial maturation of B. obtusa and B. rhodina had a quadratic curvilinear response due to temperature, with a maximum maturation at 12, 18, and 24°C with B. obtusa and at 24°C with B. rhodina. Spore maturation would affect longevity of conidial viability. Maximum spore production over time and percent pigmented spores over time by B. obtusa, and spore maturation over time by B. rhodina occurred in weeks 8, 9, and 10 with a significant linear response (P ≤ 0.05). All three Botryosphaeria spp. produced conidia over the 6 to 30°C range and over the 7-week period (weeks 4 to 10), with maximum sporulation or spore maturation at 18 to 24°C.
Fusarium Wilt of African Daisy (Osteospermum sp.) Caused by Fusarium oxysporum in Italy
Authors: Garibaldi A. , Minuto A. , Gullino M. L.
Published: May 2007

During the fall of 2002, African daisy (Osteospermum sp.) plants showing symptoms of a wilt disease were observed in a commercial, nonheated glasshouse in Albenga in northern Italy. Wilted plants were first observed when outside temperatures were between 15 and 28°C. Symptoms were first observed on seedlings 40 days after they had been transplanted into pots. The vascular tissues of affected plants appeared brown. These plants were stunted and developed yellowed leaves with brown or black streaks in the vascular system. The vascular streaks in the yellow leaves extended from the crown and were continuous with a brown discoloration in the vascular system of the crown and upper taproot. Fusarium oxysporum was consistently and readily isolated from symptomatic vascular tissue onto a Fusarium-selective medium (1). Healthy, rooted, 40-day-old plants were inoculated by root-dip with a conidial suspension (1 × 107 CFU/ml) of three isolates of F. oxysporum obtained from infected plants and transplanted into pots filled with steam-sterilized soil. Noninoculated plants served as control treatments. Plants (10 per treatment) were grown in a glasshouse at an average temperature of 25°C (minimum of 12°C and maximum of 39°C). Wilt symptoms and vascular discoloration in the roots, crown, and veins developed within 20 days on each inoculated plant, while noninoculated plants remained healthy. F. oxysporum was consistently reisolated from infected plants. The pathogenicity test was conducted twice. To our knowledge, this is the first report of F. oxysporum on Osteospermum sp. in Italy or elsewhere in the world.

Reference: (1) H. Komada. Rev. Plant Prot. Res. 8:114, 1975.
First Report of Powdery Mildew on Potato Caused by Golovinomyces cichoracearum in California
Authors: Romberg M. K. , Nuñez J. J. , Farrar J. J.
Published: May 2007

In October 2003, potato plants in three fields (cv. Desiree, Satina, Midas, and Mondial) in Lancaster, California exhibited symptoms and signs of powdery mildew. Disease symptoms were most severe on cvs. Desiree and Santina. Disease expression was greater along sprinkler lines and in localized areas from which the disease spread to surrounding plants. Severely affected plants began collapsing just prior to water cutoff. Early symptoms comprise small dark areas on the adaxial surface of leaves, along the veins, and at the petioles. Dark lesions consisting of mycelia and conidiophores were also visible on the main stems of affected plants. As the disease progressed, leaves were covered by a gray powdery fungal mass, and older leaves became necrotic. Conidial chains arising from the hyaline, epiphytic mycelia consisted of two to eight conidia. The cylindric to doliform conidia measured 16.8 to 22.8 μm wide (mean = 19.2, standard error = 0.36, N = 30) × 28.8 to 45.6 μm long (mean = 32.4, standard error = 0.75, N = 30). No cleistothecia were observed. Identification of the causal agent as Golovinomyces cichoracearum (synonyms G. orontii and Erysiphe cichoracearum) based on morphology was confirmed by internal transcribed spacer (ITS)-polymerase chain reaction (PCR). Conidia were washed off the affected leaves, concentrated by filtration and centrifugation, and sonicated to release genomic DNA. PCR was performed on the sonicated conidia with primers ITS4 and ITS5 (2), and the resulting amplicon was purified and sequenced. BLAST analysis of the ITS sequence revealed a 99% homology to E. cichoracearum from an Ambrosia sp. (GenBank Accession No. AF011292). Pathogenicity was confirmed on potato seedlings cv. Red La Soda. Inoculations were performed twice on six plants (three pots) each time. A sterile brush was used to transfer conidia from the affected leaves to seedlings consisting of two to three fully expanded leaves. A plastic bag was placed around each pot containing two seedlings for 1 to 2 days and then removed. Noninoculated controls were stroked with a sterile brush, placed in a plastic bag for 1 to 2 days, and kept in the greenhouse on a separate bench. Two control plants were included for each inoculation. Plants were maintained in a greenhouse at approximately 25 to 28°C and 40 to 60% relative humidity. After 7 days, dark spots were visible on the leaves of all inoculated plants, and conidiophores with conidia identical to those of the isolate used as the inoculum source were apparent after 10 days. The controls showed no disease symptoms or signs. To our knowledge, this is the first report of powdery mildew caused by G. cichoracearum on potato in California. The first field report of the disease was from Washington in 1950 (1), with subsequent reports from Utah and Ohio.

References: (1) J. D. Menzies. Plant Dis. Rep. 34:140, 1950. (2) T. J. White et al. PCR Protocols. Academic Press, New York, 1990.
Fusarium Wilt of Gerbera in Soil and Soilless Crops in Italy
Authors: Garibaldi A. , Minuto A. , Bertetti D. , Gullino M. L.
Published: May 2007

In 2002, gerbera (Gerbera jamesonii cv. Kaiki) plants that were grown for cut flowers in a soilless cultivation system (rockwool substrate) at Albenga (Savona) in northern Italy were observed exhibiting symptoms of a wilt disease. During the summer of 2002, in a commercial gerbera farm in the province of Imperia (northern Italy), a similar wilt was also observed on cvs. Red Bull, Anedin, and Gud finger that were grown in soil. In both cases, the planting material originated from the Netherlands. During 2003, wilted plants (cvs. Red Bull, Basic, and Cirill) were repeatedly observed in other commercial greenhouses located in the same area. Affected plants were stunted and developed yellowed leaves with initially brown and eventually black streaks in the vascular system. The vascular streaks in the yellow leaves were continuous with a brown discoloration in the vascular system of the crown and upper taproot. In some cases, the leaves of affected plants turned red. From these plants, Fusarium spp. were consistently and readily isolated from symptomatic vascular tissue onto a Fusarium-selective medium (2). Colonies were identified as F. oxysporum after subculturing on potato dextrose agar. Healthy rooted 30-day old plants (cv. Dino) were inoculated by dipping roots into a conidial suspension (5 × 107 conidia per ml) in one of six test isolates of F. oxysporum. Plants were transplanted (1 plant per pot) into pots (3.5 l vol) containing rockwool-based substrate. Noninoculated plants served as control treatments. Plants (21 per treatment) were grown in a glasshouse with an average day temperature of 31°C and night temperature of 25°C (minimum of 20°C and maximum of 42°C). Wilt symptoms and vascular discoloration in the roots, crown, and veins developed within 30 days on each inoculated plant, while noninoculated plants remained healthy. F. oxysporum was consistently reisolated from infected plants. The pathogenicity test was conducted twice. To our knowledge, this is the first report of the presence of F. oxysporum on gerbera in Italy. A wilt of gerbera was described in the Netherlands in 1952 (1) but its presence was not confirmed in further observations (3).

Reference: (1) J. Arx and J. A. von Tijdschr. PlZiekt. 58:5, 1952 (2) H. Komada. Rev. Plant Prot. Res. 8:114, 1975. (3) G. Scholten. Neth. J. Plant Pathol. 76:212, 1970.
Identification and Detection of a Virus Associated with Strawberry Pallidosis Disease
Authors: Tzanetakis Ioannis E. , Halgren Anne B. , Keller Karen E. , Hokanson Stanley C. , Maas John L. , McCarthy Paul L. , Martin Robert R.
Published: May 2007

The etiology of pallidosis, a disease of strawberry identified more than 45 years ago, remains unknown. We report a putative agent of the disease, a virus belonging to the Crinivirus genus of the Closterovirideae family. A sensitive reverse transcription-polymerase chain reaction (RTPCR) test has been developed. Polyclonal antibodies that can be used to detect the virus in petiole tissue blots were developed using a recombinant virus coat protein. The nucleotide sequences of regions of the viral genome that encode the heat shock protein 70 homolog and the major coat protein were obtained. Alignments of the major coat protein show that the virus isolated from strawberry plants positive for pallidosis is most closely related to Cucumber yellows virus (syn. Beet pseudo-yellows virus) and Cucurbit yellow stunt disorder virus, members of the Crinivirus genus.
Conventional and Real-Time PCR-Based Assay for Detecting Pathogenic Alternaria brassicae in Cruciferous Seed
Authors: Guillemette Thomas , Iacomi-Vasilescu Béatrice , Simoneau Philippe
Published: May 2007

Alternaria brassicae is an important seedborne pathogenic fungus responsible for the black spot disease of crucifers. Sanitary control of commercial seed is necessary to limit the spread of this pathogen. Current detection methods, based on culture and morphological identification of the fungus, are time consuming, laborious, and not always reliable. Therefore, a polymerase chain reaction (PCR)-based assay was developed with A. brassicae-specific primers designed on the basis of the sequence of two clustered genes potentially involved in pathogenicity. Two sets of primers were selected for conventional and real-time PCR, respectively. In both cases, A. brassicae was specifically detected using DNA extracted from seed. The real-time PCR-based method presented here can be automated easily and preliminary results indicate that it is efficient for quantitative estimation of seed infection.