bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular Characterization of a Distinct Begomovirus Associated with Tomato Leaf Curl Disease in Arusha of Tanzania
Authors: Shih S. L. , Tsai W. S. , Green S. K. , Lee L. M.
Published: May 2007

Mild leaf curling and yellowing symptoms were observed in approximately 5% of 1-month-old tomato plants (Solanum lycopersicum) in a farmer's field in Tengeru, Arusha, Tanzania in January 2006. DNA was extracted from four symptomatic and five asymptomatic plants and tested for the presence of begomovirus by polymerase chain reaction (PCR) using primer pair PAL1v1978/PAR1c715 (4). All asymptomatic samples were negative. Two of four symptomatic samples yielded the expected 1.4-kb DNA-A fragment for begomovirus. DNA-B was not detected in these two samples by PCR using the DNA-B degenerate primer pairs DNABLC1/DNABLV2 and DNABLC2/DNABLV2 (2), and PBL1v2040/PCRc1 and PBL1v2040/PCRc154 (4). DNA-beta was also not detectable using DNA-beta specific primers (1). The 1.4-kb PCR product from one sample was cloned and sequenced. On the basis of the sequence of the 1.4-kb DNA product, specific primers were designed to complete the DNA-A sequence. The DNA-A consisted of 2,766 nucleotides (Genbank Accession No. DQ519575) and was found to contain the geminiviral conserved nanosequence-TAATATTAC in the intergenic region and the six predicted open reading frames (V1, V2, C1, C2, C3, and C4). BLAST analysis was conducted with geminivirus sequences available in GenBank, and MegAlign software (DNASTAR, Inc, Madison, WI) was used for further comparisons. Highest sequence identity (84%) was with the partially sequenced Tomato leaf curl Tanzania virus found in Makutupora, Tanzania in 1994 (1,523 nucleotides, Genbank Accession No. U73498) in the 1,919 nt to 679 nt region. Low sequence identity (78%) was noted with Tomato yellow leaf curl Sardinia virus (Genbank Accession No. X61153) that is reportedly prevalent in Arusha, Morogoro, Dodoma, Iringa, Kilimanjaro, and Dar es Salaam of Tanzania (3). Comparison of the nucleotide sequence of this new virus with those of full-length begomoviral DNA-A available in GenBank indicated highest sequence identity (81%) with Tomato leaf curl Mayotte virus (EMBL Accession No. AJ865341). On the basis of the DNA-A sequence comparisons and the International Committee on Taxonomy of Viruses proposed species demarcation of 89% sequence identity, the tomato leaf curl virus from Arusha, Tanzania constitutes a distinct begomovirus and the name Tomato leaf curl Arusha virus is proposed.

References: (1) R. W. Briddon et al. Mol. Biotechnol. 20:315, 2002. (2) S. K. Green et al. Plant Dis. 85:1286, 2001. (3) B. D. Kashina et al. Arch. Phytopathol. Plant Prot. 35:255, 2002 (4) M. R. Rojas et al. Plant Dis. 77:340, 1993.
First Report of Ramularia cercosporelloides on Carthamus tinctorius in Northwestern Mexico
Authors: Huerta-Espino J. , Constantinescu O. , Velásquez C. , Herrera-Foessel S. A. , Figueroa-Lopez P.
Published: May 2007

Severe yield losses caused by an unidentified fungal disease occurred on safflower in Sonora, Mexico from 2001 to 2006. Leaf spots were pale at the beginning and became sunken lesions, spots turned brown, and diseased tissue became necrotic. Under continuous presence of dew, new infections occurred and the number of lesions increased, coalesced, and eventually the entire leaf and plant turned brown and dried up. The fungus appears as a whitish mold covering the lesions. Observations with a dissecting microscope revealed fungal growth on both leaf surfaces. Spots had minute, gray-to-pink tufts emerging from the host tissues. Stromata were roughly spherical, 35 to 55 μm in diameter, developed under the epidermis near the edge of the spots from which conidiophores arose. Fascicles of conidiophores emerged through stomata from colorless or slightly yellowish stroma and were simple, colorless, or slightly yellowish, as much as 85 μm long and 2.5 to 3 μm wide, with a pigmented scar at the tip. Conidia, formed in chains at scar sites on conidiophores, were colorless, obclavate, 0 to 1 septate, approximately 24 to 32 μm long, and 4.5 to 7 μm wide at the broadest part with a pigmented scar either at the base or at both ends. On the basis of symptoms and fungal morphology, the pathogen was identified as Ramularia cercosporelloides U. Braun & Crous (=Cercosporella carthami) (1). Seven specimens were deposited at the Uppsala University Herbarium as Nos. UPS F-119998 to 120004. Conidia were transferred to water agar plates from symptomatic leaves after 8 days in a humid chamber. Ten single conidia were plated onto a Septoria tritici medium (4 g each of malt extract, yeast extract, and sucrose, and 18 g of agar per liter of water). Colonies of the fungus were white-to-light pink with irregular margins and very slow in growth. Inoculum was produced by transferring 2 ml of distilled water containing conidia onto petri plates filled with Septoria medium. Plates were incubated at 18°C for 12 days. Water suspension was amended with two drops of Tween 20 per liter of inoculum. Pathogenicity of five isolates was confirmed by spraying a suspension of 1.0 × 105 conidia/ml onto five pots of four direct-seeded adult plants of cv. S-518 per isolate. Plants were kept in a dew chamber (20°C) for 48 h under 16 h of darkness and 8 h of light and then in a greenhouse (20 to 24°C). After 2 weeks, leaves developed the characteristic spots, and R. cercosporelloides was isolated from symptomatic tissue. To our knowledge, this is the first report of R. cercosporelloides on safflower, not only in Mexico, but also on the American continent.

Reference: (1) U. Braun. A monograph of Cercosporella, Ramularia and allied genera (Phytopathogenic Hyphomycetes). Vol 2. IHW-Verlag. Eching bei Munchen, 1998.
First Report of Phytophthora capsici Causing Wilt on Hydropronically Grown Cucumber in Mexico
Authors: Fernández-Pavía S. P. , Rodríguez-Alvarado G. , López-Ordaz A. , Fernández-Pavía Y. L.
Published: May 2007

During August 2005, wilted cucumber (Cucumis sativus cv. Tasty Green) plants were observed in a commercial greenhouse with a closed hydroponic system in the state of Mexico. Disease incidence was 50%. Diseased plants were detected 15 days after transplanting, when plants were overwatered. Yield was severely reduced when disease affected mature plants. Wilted plants showed basal stem lesions and root rot. Phytophthora capsici was consistently isolated from diseased tissue on corn meal agar (CMA) with tartaric acid. Oomycete identification was based on sporangial and gametangial characteristics (2). Sporangia produced on blocks of CMA at 25°C were spherical, broadly ellipsoid or obovoid with one papillae, and deciduous with a long pedicel (1). The isolates were heterothallic, and oogonia with amphigynous antheridia were observed in pairings with an A1 isolate of P. capsici, therefore, the isolates were determined to be an A2. Pathogenicity tests were conducted on 2-month-old cucumber seedlings under controlled conditions (25°C). Inoculation was performed by placing small pieces of agar with mycelium of 5- to 7-day-old cultures on the stem base and wrapping with Parafilm. Control plants were inoculated with CMA agar. No symptoms were observed on the control. Plants inoculated with the P. capsici isolated from the diseased cucumbers showed a basal stem lesion, followed by wilting and death 7 to 14 days after inoculation. The isolate was also pathogenic on tomato and eggplant that were grown at the same time in the commercial greenhouse sharing the nutrient solution. P. capsici sporangia were observed on the roots of both hosts. To our knowledge, this is the first report of P. capsici affecting cucumber in a hydroponics system in Mexico.

References: (1) M. Aragaki and J. Y. Uchida. Mycologia 93:137, 2001. (2) D. C. Erwin and O. K. Ribeiro. Phytophthora Diseases Worldwide. The American Phytopathological Society. St. Paul MN, 1996.
Re-emergence of Cassava Brown Streak Disease in Uganda
Authors: Alicai T. , Omongo C. A. , Maruthi M. N. , Hillocks R. J. , Baguma Y. , Kawuki R. , Bua A. , Otim-Nape G. W. , Colvin J.
Published: May 2007

During November 2004, veinal chlorosis on mature cassava leaves, typical of cassava brown streak disease (CBSD), was observed at Mukono in central Uganda. Five out of 11 cultivars at the site showed CBSD symptoms (incidence range 4 to 64%). In a survey of farmers' fields, CBSD was observed in Wakiso and Mukono districts. Incidence of cassava mosaic disease was also recorded and averaged 60% for landraces (range 16.7 to 100%) and 20% for resistant varieties (range 0 to 65%). Leaf samples of plants with CBSD symptoms produced an amplicon of 222 bp using reverse transcription-polymerase chain reaction with primers that amplify a fragment of the coat protein (CP) gene of Cassava brown streak virus. Sequence comparisons based on the amplified CP gene fragment indicated that the isolates have 77 to 82.9% nucleotide and 43.9 to 56.8% amino acid identity with those from Mozambique and Tanzania. There was 95.9 to 99.5% nucleotide and 85.1 to 90.5% amino acid identity among the Ugandan isolates. These results confirm the re-emergence of CBSD in Uganda after it was first observed in the 1930s in cassava introduced from Tanzania and controlled by eradication. Prior to this report, CBSD was known to be restricted to the coastal lowlands of East Africa.
Virulence Variability of Puccinia coronata f. sp. avenae Isolates Collected in Three Counties from Rio Grande do Sul State, Brazil
Authors: Vieira E. A. , Carvalho F. I. F. , Chaves M. S. , de Oliveira A. Costa , Benin G. , Hartwig I. , Silva J. A. G. , Bertan I. , Martins A. F. , Martins L. F.
Published: May 2007

Using isolates collected in three counties of Rio Grande do Sul State, Brazil, the goals of this work were to determine (i) the pattern of virulence or avirulence of the isolates to 25 Pc resistance genes, (ii) the similarity in virulence among Puccinia coronata f. sp. avenae isolates considering their pattern of virulence or avirulence, (iii) the race code for each isolate by the North American system of nomenclature, and (iv) the supplemental Pc genes potentially useful as local differentials for P. coronata f. sp. avenae races. The results indicate that the southern Brazilian rust isolates presented a high level of virulence, because 66% of inoculations manifested the high infection type. Only the Pc 68 gene was effective against all tested isolates. In general, each isolate presented a different pattern of virulence or avirulence, which indicates the high variability for virulence that the fungus presents at the sampled sites. However, the North American system of nomenclature was not completely sufficient in distinguishing southern Brazilian races. Thus, the genes Pc 36, Pc 53, Pc 55, and Pc 63 represent a possible gene combination to be incorporated into the North American system of nomenclature.
Host-Parasite Relationships in Fall-Sown Sugar Beets Infected by the Stem and Bulb Nematode, Ditylenchus dipsaci
Authors: Castillo Pablo , Vovlas Nicola , Azpilicueta Andrea , Landa Blanca B. , Jiménez-Díaz Rafael M.
Published: May 2007

Stunted growth of fall-sown sugar beets (Beta vulgaris) associated with high incidence of crownroot infections and large soil infestations by Ditylenchus dipsaci were observed at the end of the crop growing season in southern Spain by early June 2005. The largest proportion (75%) of the nematode life-stages in plant and soil was the fourth-stage juvenile. The large number (up to 3,750 nematodes per gram of fresh tissue) of D. dipsaci individuals and severe anatomical alterations observed in storage sugar beet roots suggest that the stem and bulb nematode is the causal agent of the impaired growth of sugar beets observed in commercial fields. Observed morphological traits of nematode specimens and results of specific polymerase chain reaction (PCR) and phylogenetic analyses confirmed that the population of D. dipsaci infecting sugar beet belongs to the normal (nongiant) biological type of the nematode. Results of host-range bioassays indicated that the population of D. dipsaci infecting sugar beet in southern Spain reproduces on pea (including seeds and pods), onion, potato, spinach, and tomato, but not on bean, cotton, maize, and tobacco. These results indicate that D. dipsaci may be an important constraint for sugar beet crops in the affected area, but also for other important crops commonly used in rotation with them.
Effects of Host Resistance and Inoculum Density on the Suppression of Fusarium Wilt of Watermelon Induced by Hairy Vetch
Authors: Zhou X. G. , Everts K. L.
Published: May 2007

Hairy vetch (Vicia villosa) used as a soil amendment is a newly described potential management tool for the suppression of Fusarium wilt of watermelon (Citrullus lanatus). However, the effect of inoculum density and the level of resistance in the host on the level of suppression are not understood. In this study, hairy vetch-induced wilt suppression was evaluated in the greenhouse on 12 watermelon cultivars with different levels of wilt resistance and in 16 naturally infested soil samples collected from commercial watermelon fields. Wilt suppression occurred in all but two cultivars and with the trend that suppression increased as the level of resistance in cultivars increased. Fusarium wilt suppression was 22, 53, and 63% in hairy vetch-amended soil compared with nonamended soil on cultivars ranked as susceptible, moderately resistant, and highly resistant, respectively. Suppression also occurred in nine of the soils that contained populations of Fusarium oxysporum f. sp. niveum below 1,100 CFU/g of soil. However, at this level or higher, significant wilt suppression was not observed. The magnitude of disease suppression decreased with the increase of inoculum in the soils. The induced wilt suppression appeared to be correlated with an increase in bacterial populations in soil. Hairy vetch-induced suppression to Fusarium wilt in watermelon is dependent on the resistance level of cultivars and is overcome by high inoculum level of F. oxysporum f. sp. niveum in soil.
Phytophthora Species Associated with Diseased Woody Ornamentals in Minnesota Nurseries
Authors: Schwingle B. W. , Smith J. A. , Blanchette R. A.
Published: May 2007

Phytophthora species are responsible for causing extensive losses of ornamental plants worldwide. Recent international and national surveys for the detection of P. ramorum have led to the finding of previously undescribed Phytophthora species. Since no previous Phytophthora surveys have been carried out in Minnesota, surveys of ornamental nurseries were performed over 4 years to isolate and identify the Phytophthora species causing diseases of woody plants in Minnesota. Species were identified by direct sequencing of internal transcribed spacer (ITS) rDNA, β-tub, and mitochondrial coxI genes. Species associated with diseased ornamental plants include P. cactorum, P. cambivora, P. citricola, P. citrophthora, P. hedraiandra, P. megasperma, P. nicotianae, and the previously identified but undescribed taxon P. Pgchlamydo. The most common species encountered were P. cactorum, P. citricola, and P. citrophthora. Two additional isolates obtained did not match known species. One was similar to P. alni subsp. alni, and the other appeared to be a new species and is referred to as P. sp. MN1. In addition, species are reported for the first time from several hosts. Results indicated that several Phytophthora species were more widespread in the nursery industry than previously thought, and undescribed species were causing disease in Minnesota ornamental nurseries.
Occurrence, Distribution, and Relative Incidence of Seven Viruses Infecting Greenhouse-Grown Cucurbits in Iran
Authors: Massumi Hossain , Samei Asghar , Pour Akbar Hosseini , Shaabanian Mehdi , Rahimian Heshmetollah
Published: May 2007

Greenhouse-grown cucurbit crops in several Iranian regions were surveyed for the incidence of Cucumber mosaic virus (CMV), Squash mosaic virus (SqMV), Papaya ring spot virus-type W (PRSV-W), Watermelon mosaic virus-2 (WMV-2), Zucchini yellow mosaic virus (ZYMV), Cucumber necrosis virus (CuNV) and Tomato spotted wilt virus (TSWV) from September 2002 to June 2004. In all, 1,304 random and 1,085 symptomatic leaf or fruit samples were collected. Samples were analyzed for virus infection by enzyme-linked immunosorbent assay. CMV and ZYMV were the viruses most frequently detected, accounting for 21.2 and 18% of the infected plants, respectively. WMV-2 was detected with 4.3% incidence in 15 regions and TSWV with 1.25% incidence only in 2 regions. CuNV, SqMV, and PRSV-W were not detected in any samples. Double and triple infections involving different combinations of CMV, ZYMV, WMV-2, and TSWV were noted in 117 and 4 samples, respectively. Natural infection of cucumber with TSWV and ZYMV is reported for the first time from Iran. Of 16 plant species from 14 genera, growing in or around greenhouse facilities, 6 were found infected with ZYMV, TSWV, WMV-2, and CMV and may act as reservoirs of the viruses. Four species are reported as new hosts of these viruses.
Wheat streak mosaic virusin Australia: Relationship to Isolates from the Pacific Northwest of the USA and Its Dispersion Via Seed Transmission
Authors: Dwyer Geoffrey I. , Gibbs Mark J. , Gibbs Adrian J. , Jones Roger A. C.
Published: May 2007

Wheat streak mosaic virus (WSMV) was found for the first time in Australia in 2002. It subsequently was found widely dispersed around the continent and was shown to be seedborne in wheat. The coat protein (CP) gene sequences of nine WSMV isolates from eastern and southwestern Australia are reported, one obtained directly from infected wheat seed, three from seedlings grown from infected wheat seed, and five from infected wheat plant samples. These sequences were compared with those of 66 WSMV CP sequences, including eight previously sequenced Australian isolates. All 17 Australian sequences formed a closely knit monophyletic cluster as part of the D1 subclade of WSMV previously only reported from the Pacific Northwest of the United States. The close phylogenetic relationships of these sequences indicate that the Australian outbreak arose from a single incursion, the source of which appears to be the Pacific Northwest. Three Australian CP sequences were identical, one from the location of the post-entry quarantine facility at Tamworth, New South Wales, and two from seed that had originally been propagated at that facility. These three sequences were closest to the Pacific Northwest sequences and differed from them by as little as eight nucleotides (0.76%). The sequence of a third seedborne isolate originally from the same source differed from the other two seedborne isolates by two nucleotides, indicating that the immigrant WSMV population may have been variable. The other Australian sequences differed from the three identical ones by only one to four nucleotides. The phylogenetic pattern and small number of nucleotide differences between individual isolates from different geographic locations fit the scenario that the virus was introduced once in seed of wheat breeding material, multiplied where it was introduced, and then was dispersed over long distances around the Australian continent along standard distribution routes for wheat breeding lines, germ plasm, and crop seed. These conclusions provide a cautionary tale indicating the importance of effective monitoring of imported plant materials for exotic virus diseases during post-entry quarantine.
Efficacy of Germination Stimulants of Sclerotia of Sclerotium cepivorum for Management of White Rot of Garlic
Authors: Davis R. M. , Hao J. J. , Romberg M. K. , Nunez J. J. , Smith R. F.
Published: May 2007

The ability of soil-applied garlic powder and diallyl disulfide to stimulate germination of sclerotia of Sclerotium cepivorum, the cause of white rot of onion and garlic, was evaluated in four field trials. Because sclerotia germinate in response to exudation of specific volatile sulfides and thiols from allium roots, sulfides applied to the ground in the absence of an allium crop cause death of the sclerotia after they germinate and exhaust nutrient reserves. In this study, garlic powder and a synthetic garlic oil, diallyl disulfide, were incorporated into the soil in commercial fields naturally infested with S. cepivorum. Methyl bromide was included as a chemical control. Within 3 months after treatment, over 90% of the sclerotia died in the plots treated with the germinationstimulants, which was similar to the reduction of viable sclerotia achieved with an application of methyl bromide. The degree of sclerotial mortality in plots treated with garlic powder at 112 kg/ha or more was almost equal to that achieved by diallyl disulfide at 0.5 ml/m2 or methyl bromide at 448 kg/ha. Despite the efficacy of the stimulants and methyl bromide to reduce populations of sclerotia, the pathogen caused substantial root rot and yield losses in subsequent garlic crops planted about a year after soil treatment. However, germination stimulants have utility because the reduction of the vast majority of sclerotia in a field reduces the risk of spread of the pathogen to neighboring fields.
Postharvest Decay Management for Stone Fruit Crops in California Using the “Reduced-Risk” Fungicides Fludioxonil and Fenhexamid
Authors: Förster H. , Driever G. F. , Thompson D. C. , Adaskaveg J. E.
Published: May 2007

In laboratory studies and experimental packingline trials that closely simulated fungicide treatments under commercial conditions, the “reduced-risk” fungicides fenhexamid and fludioxonil were highly effective in managing postharvest brown rot and gray mold decays of peach, nectarine, and plum caused by Monilinia fructicola and Botrytis cinerea, respectively. Tebuconazole was more effective against brown rot than against gray mold. Additionally, fludioxonil and tebuconazole significantly reduced the incidence of Rhizopus rot caused by Rhizopus stolonifer. In laboratory studies, the QoI fungicide azoxystrobin was not consistent in its decay control activity. The high efficacy of fenhexamid and fludioxonil against brown rot and gray mold was substantiated by low effective concentrations necessary (≤0.063 mg/liter)for 50% inhibition of mycelial growth in vitro. In general, fungicides applied 14 to 16 h after wound inoculation were significantly more effective than those applied before inoculation. These results indicate that the fungicides act mainly as protectants that do not penetrate deeply enough into the fruit to prevent decay from wounds that extend below the fruit epidermis. Laboratory treatments of plum fruit generally were less effective than those of peach or nectarine fruit. Comparative studies using either low-volume spray or high-volume, in-line drench applications over a roller bed demonstrated that drench applications were significantly more effective in reducing postharvest decaysof inoculated plum fruit. Decay incidence using fenhexamid or fludioxonil was ≤1.1%, whereas incidence after the spray applications was between 25.2 and 40.4% for brown rot, between 12.0 and 24.3% for gray mold, or 62.6% for Rhizopus rot (fludioxonil only). This research identified effective replacements for iprodione, a fungicide voluntarily canceled by the manufacturer in 1996.
Comparison of Muscodor albus Volatiles with a Biorational Mixture for Control of Seedling Diseases of Sugar Beet and Root-Knot Nematode on Tomato
Authors: Grimme E. , Zidack N. K. , Sikora R. A. , Strobel G. A. , Jacobsen B. J.
Published: May 2007

A biorational synthetic mixture of organic components mimicking key antimicrobial gases produced by Muscodor albus was equivalent to the use of live M. albus for control of seedling diseases of sugar beet (Beta vulgaris) caused by Pythium ultimum, Rhizoctonia solani AG 2-2, and Aphanomyces cochlioides. The biorational mixture provided better control than the live M. albus formulation for control of root-knot nematode, Meloidogyne incognita, on tomato (Lycopersicon esculentum). The biorational mixture provided control of damping-off equal to a starch-based formulation of the live fungus for all three sugar beet pathogens, and significantly reduced the number of root-knot galls on tomato roots compared with a barley-based formulation. Rate studies with the biorational mixture showed that 2 and 0.75 µl/cm3 of soil were required to provide optimal control of Rhizoctonia and Pythium damping-off of sugar beet, respectively. Five microliters of biorational mixture per milliliter of water was required for 100% mortality in 24 h for Meloidogyne incognita in in vitro studies. In in vivo studies, 1.67 µl of the biorational mixture/cm3 of sand resulted in fewer root-knot galls than a Muscodor albus infested ground barley formulation applied at 5 g/liter of sand.
First Report of a Canker Disease of Walnut Caused by Botryodiplodia theobromae in Egypt
Authors: Haggag W. M. , Abou Rayya M. S. M. , Kasim N. E.
Published: May 2007

Botryodiplodia spp. are known to produce cankers and dieback of several woody hosts. Botryodiplodia diseases were observed in 7-year-old orchards in Rhafah, north of Sinai, Egypt, in July 2005 and 2006. Symptoms appeared as dieback and cankers with dead leaves that were covered mostly with grayish white fungal growth; black pycnidia appeared on the surface of the infected branches. Plant foliage was discolored and partially or completely dry. When the outer bark was removed, the affected tissue appeared dark brown, in contrast to the yellowish green of healthy inner bark. On the basis of morphological characteristics (3), these fungi were identified as Botryodiplodia theobromae Pat. by the Plant Pathology Department, National Research Centre. Sporulating lesions were black and had a rough surface caused by the erumpent, confluent arrangement of pycnidia formed in infected tissue. The pycnidia were smallest in naturally infected twigs in nutritionally rich medium such as oatmeal agar (190 to 887 × 155 to 705 μm). Conidia were initially hyaline and unicellular, subovoid to ellipsoidal with a granular content. Mature conidia were two-celled, cinnamon to light brown, and often with longitudinal striations. Conidia measured 20 to 30 × 12 to 15 μm. Pathogenicity of isolates from symptomatic branches was determined by branch inoculations on rooted cuttings made from 7-year-old walnut trees growing in plastic pots. One isolate was inoculated on wounded and unwounded twigs using 100 μl of a suspension of 5 × 105 conidia per ml. Control branches were sprayed with water. All inoculated and control plants were kept in a greenhouse and watered as needed. There were three replicate plants for each isolate and inoculation technique that was used. After 3 weeks, cankers and grayish necrotic lesions developed on all inoculated plants. Samples of tissue from 10 infected walnut branches were plated on water agar. B. theobromae was recovered from all sampled plants. Control plants did not display any symptoms. B. theobromae has been reported on species of walnut from the Hermosillo Coast of Mexico (1) and India (2). To our knowledge, this is the first report of walnut dieback and canker caused by this pathogen in Egypt.

References: (1) J. A. Arredondo. Rev. Mex. Fitopatol. 12:138, 1994. (2) B. Kusum. Indian J. Mycol. Plant Pathol. 21:295, 1991. (3). S. Masilamani and J. Muthumary. Mycol. Res. 100:1383, 1996.
Association of Ophiostoma novo-ulmi with Scolytus schevyrewi (Scolytidae) in Colorado
Authors: Jacobi W. R. , Koski R. D. , Harrington T. C. , Witcosky J. J.
Published: May 2007

The smaller European elm bark beetle, Scolytus multistriatus, has been the primary vector of the Dutch elm disease fungus, Ophiostoma novo-ulmi, in elm trees in Colorado since 1948. An exotic from Asia, the banded elm bark beetle, Scolytus schevyrewi, was found in Siberian elm, Ulmus pumila, in Colorado in April of 2003; this was the first report of S. schevyrewi in North America. S. schevyrewi is now found throughout much of Colorado and in at least 21 other states. The similarities in breeding and feeding habits between S. schevyrewi and S. multistriatus have raised concerns about the ability of S. schevyrewi to serve as a vector for O. novo-ulmi. The objective of this preliminary study was to determine if O. novo-ulmi could be isolated from adult S. schevyrewi emerging from diseased elm trees. S. schevyrewi and S. multistriatus were allowed to infest diseased stem segments of American elm, Ulmus americana. The infested stem segments were caged and isolations were made from the adult brood that emerged. O. novo-ulmi was isolated from most of the adults of both beetle species, showing that S. schevyrewi could acquire the pathogen as effectively as S. multistriatus. Future studies are needed to determine if S. schevyrewi can effectively transmit the pathogen to healthy trees.
Characterization of Rhizoctonia-Like Fungi Isolated from Agronomic Crops and Turfgrasses in Mississippi
Authors: Tomaso-Peterson M. , Trevathan L. E.
Published: May 2007

Twenty-three isolates of Rhizoctonia spp. from agronomic crops and turfgrasses were characterized by cytological and pathological methods in order to establish the identity, pathogenicity, and virulence of Rhizoctonia spp. and anastomosis groups that occur on these hosts in Mississippi. Twelve isolates were identified as R. solani, including the five anastomosis groups (AGs) AG-1-IB, AG-2-2, AG-4, AG-5, and AG-13. Rhizoctonia zeae, R. oryzae, and eight binucleate Rhizoctonia sp., including R. cerealis, also were identified. R. solani AG-4 isolates were consistently the most virulent isolates on all hosts in pathogenicity evaluations. Pathogenicity of AG-2-2 and AG-5 isolates, binucleate Rhizoctonia spp., and R. oryzae varied between hosts. Two AG-2-2 isolates from bermudagrass or wheat were determined to be clonal isolates, with numerous self-anastomosis reactions. R. solani (AG-1-IB) was pathogenic on all graminaceous hosts. R. cerealis produced sharp eyespot symptoms on wheat and corn and minimal symptoms on cotton and soybean. This is a first report of R. cerealis as a pathogen of corn. R. zeae isolates were pathogenic on all hosts, including cotton and soybean. These results indicate that a diverse group of Rhizoctonia spp. occurs as pathogens on a wide variety of agronomic crops and turfgrasses in Mississippi.
Evaluation of Maize Inbred Lines for Resistance to Fusarium Ear Rot and Fumonisin Accumulation in Grain in Tropical Africa
Authors: Afolabi C. G. , Ojiambo P. S. , Ekpo E. J. A. , Menkir A. , Bandyopadhyay R.
Published: May 2007

Fusarium ear rot and fumonisin contamination is a major problem facing maize growers worldwide, and host resistance is the most effective strategy to control the disease, but resistant genotypes have not been identified. In 2003, a total of 103 maize inbred lines were evaluated for Fusarium ear rot caused by Fusarium verticillioides in field trials in Ikenne and Ibadan, Nigeria. Disease was initiated from natural infection in the Ikenne trial and from artificial inoculation in the Ibadan trial. Ear rot severity ranged from 1.0 to 6.0 in both locations in 2003. Fifty-two inbred lines with disease severity ≤3 (i.e., ≤ 10% visible symptoms on ears) were selected and reevaluated in 2004 for ear rot resistance, incidence of discolored kernels, and fumonisin contamination in grain. At both locations, ear rot severity on the selected lines was significantly (P < 0.0020) higher in 2004 than in 2003. The effects of selected inbred lines on disease severity were highly significant at Ikenne (P = 0.0072) and Ibadan (P < 0.0001) in 2004. Inbred lines did not affect incidence of discolored kernels at both locations and across years except at Ikenne (P = 0.0002) in 2004. Similarly, significant effects of inbred lines on fumonisin concentration were observed only at Ikenne (P = 0.0201) in 2004. However, inbred lines 02C14585, 02C14593, 02C14603, 02C14606, 02C14624, and 02C14683 had consistently low disease severity across years and locations. Fumonisin concentration was significantly correlated with ear rot only at Ikenne (R = 0.42, P < 0.0001). Correlation between fumonisin concentration and incidence of discolored kernels was also significant at Ikenne (R = 0.39, P < 0.0001) and Ibadan (R = 0.35, P = 0.0007). At both locations, no significant inbred × year interaction was observed for fumonisin concentration. Five inbred lines, namely 02C14585, 02C14603, 02C14606, 02C14624, and 02C14683, consistently had the lowest fumonisin concentration in both trials. Two of these inbred lines, 02C14624 and 02C14585, had fumonisin levels <5.0 μg/g across years in trials where disease was initiated from both natural infection and artificial inoculation. These lines that had consistently low disease severity are useful for breeding programs to develop fumonisin resistant lines.
First Report of Tomato chlorotic dwarf viroid in Petunia hybrida from the United States of America
Authors: Verhoeven J. Th. J. , Jansen C. C. C. , Werkman A. W. , Roenhorst J. W.
Published: May 2007

In November 2005, 13 accessions of Petunia hybrida from the United States of America entered the post-entry quarantine station of the Plant Protection Service in the Netherlands. The plants were inspected and tested for quarantine organisms according to Directives 95/44 and 97/46 of the European Union. No virus and viroid symptoms were observed in the imported plants or in mechanically inoculated plants of Chenopodium quinoa, Nicotiana benthamiana, and N. occidentalis-P1 (3). Testing for pospiviroids by return-polyacrylamide gel electrophoresis (1) and reverse transcriptase-PCR with universal pospiviroid primers Pospi1-RE/FW (2) indicated the presence of pospiviroids in 3 and 11 P. hybrida accessions, respectively. The 196-bp amplicons of six accessions were sequenced. Sequence analysis showed the highest identity for all amplicons to both isolates of Tomato chlorotic dwarf viroid (TCDVd) in NCBI GenBank, Accession Nos. AF162131and AY372399, from Canada and the United States, respectively. Additional RT-PCRs with the Pospi1-RE/FW primers in opposite order and the semi-universal pospiviroid primers Vid-RE/FW (2) for one isolate, followed by sequence analysis, confirmed the identity as TCDVd. The isolate consisted of 359 nucleotides (GenBank Accession No. DQ859013) and showed sequence identities of 98.6 and 96.1% to the Canadian and American tomato isolates of this viroid, respectively. The next highest sequence identity was 90.0% to two accessions of Potato spindle tuber viroid (GenBank Accession Nos. AJ593449 and AY962324). On the basis of these results, the viroid from P. hybrida was identified as TCDVd. To our knowledge, this is the first report of TCDVd in this plant species.

Reference: (1) J. W. Roenhorst et al. EPPO Bull. 30:453, 2000. (2) J. Th. J. Verhoeven et al. Eur. J. Plant Pathol. 110:823, 2004. (3) J. Th. J. Verhoeven and J. W. Roenhorst. EPPO Bull. 33:305, 2003.
Occurrence of Meloidogyne spartinae on Spartina alterniflora in Connecticut and Massachusetts
Authors: LaMondia J. A. , Elmer W. H.
Published: May 2007

Meloidogyne spartinae (Rau & Fassuliotis, 1965) was described from roots of smooth cordgrass (Spartina alterniflora Loisel) in Florida, Georgia, North and South Carolina, New Jersey, and New York (1,2). Affected plants were sampled in declining saltwater marshes at the Cape Cod National Seashore in Wellfleet, MA in May 2006 and Hammonassett State Park in Madison, CT in August 2006. Plants in adjacent, healthy stands were also sampled. Females, males, juveniles, and eggs of nematodes identified as M. spartinae were visible in roots stained with acid fuschin or were dissected from terminal galls at the root apex and from pockets in the root cortex where no galling was evident. The circular to ovoid terminal galls typically stopped root elongation. Morphological characteristics were used to identify this nematode as M. spartinae. Mature females in the root cortex were visible under a discolored lesion that appeared to result from a split in the cortex, probably from female expansion during development. Females were oval to lemon shaped with the neck protruding markedly to one side. Females also exhibited protruding perineal regions. In terminal galls, females were oriented toward the root tip; however, in the root cortex they were oriented either toward the root tip or toward the crown, with no obvious pattern. Egg masses were not observed and the eggs were deposited freely inside the gall or root cortex. Second-stage juveniles were long (730.3 μm, n = 60) with an elongate tail terminus. Males (2,203 μm, n = 40) were present in galls containing females. No morphological differences were observed between nematodes from the terminal galls or root cortex. M. spartinae was widespread in declining and adjacent healthy S. alterniflora. To our knowledge, this is the first report of M. spartinae from Connecticut and Massachusetts and the first report of M. spartinae development within root cortical tissues without gall formation. The role of this nematode in the sudden wetland dieback phenomenon (3) is being investigated.

References: (1) J. D. Eisenback and H. Hirschmann. Nematology 3:303, 2001. (2) G. J. Rau and G. Fassuliotis. Proc. Helminthol. Soc. Wash. 32:159, 1965. (3) E. C. Webb and I. A Mendelssohn. Am. J. Bot. 83:1429, 1996.
First Report of a 16SrI-B Group Phytoplasma Associated with a Yellows-Type Disease Affecting Tomato Plants in the Baja California Peninsula of Mexico
Authors: Holguín-Peña R. J. , Vázquez-Juárez R. C. , Martínez-Soriano J. P.
Published: May 2007

Since 2000, a phytoplasma-like disease (locally known as “permanent yellowing”) was observed on tomatoes (Lycopersicon esculentum Mill.) grown in the Valle de San Quintín in northern Baja California Peninsula. Affected plants showed general chlorosis, severe stunting, upwardly rolled leaves, bronzing of mature leaves, purple discoloration of veins, “little leaf”, abnormal floral structures, and excessive branching of axillary shoots. Total DNA extracted from symptomatic and asymptomatic plants was used in nested (n)-PCR assays driven by phytoplasma-universal primer pair P1/P7 (3), followed by primer pair R16F2n/R16R2 (1) targeting the 16S ribosomal RNA gene of the putative phytoplasma. PCR conditions (direct and nested) were conducted as previously described (l,3). Restriction fragment length polymorphism (RFLP) patterns of nPCR-amplified products (≈ 1.25-kbp 16S rDNA fragments) digested with enzymes AluI, MseI, HhaI, and HpaII showed that 85% (17 of 20) of PCR-positive tomato samples had restriction patterns typical of phytoplasmas belonging to the aster yellows group, subgroup B (16SrI-B) “Candidatus Phytoplasma asteris” (2). Only 10% (2 of 20) of the samples were associated with a phytoplasma related to the 16SrXIII-A Mexican periwinkle virescence group (formerly group 16SrI, subgroup I). None of the symptomless plants tested positive. Subsequently, these results were confirmed by nPCR using 16SrI specific primer pair P1/Aint (4) and specific primers rp(I-B)F1/rp(I-B)R1 that amplify the ribosomal protein (rp) gene operon of aster yellows phytoplasma subgroup B (16SrI-B[rp-B]) (1). The presence of the phytoplasmas in symptomatic plants was confirmed by scanning electron microscopy. Characteristic yellow symptoms could be experimentally reproduced by graft inoculation of tomato seedlings (cv. Maya) with tissue of field-infected plants. Symptoms similar to those of field-grown diseased plants were observed consistently in most of the plants, and when graft transmitted from tomato to periwinkle (Catharantus roseus (L.) G. Don), symptoms of virescencent, small flowers were observed. In contrast, no symptoms were observed on plants grafted with tissues from healthy plants. In Baja California, it appears that at least two distinct phytoplasmas are involved in the disease complex. To our knowledge, this is the first molecular evidence of the presence of a phytoplasma associated with yellows-type diseases in the major tomato cultivation areas of the peninsula.

References: (1) I.-M. Lee et al. Phytopathology 93:1368, 2003. (2) I.-M. Lee et al. Int. J. Syst. Evol. Microbiol. 54:1037, 2004. (3) B. Schneider et al. Page 369 in: Molecular and Diagnostic Procedures in Mycoplasmology. Academic Press, San Diego, CA, 1995. (4) C. D. Smart et al. Appl. Environ. Microbiol. 62:2988, 1996.
Xylella fastidiosa Detected in New Mexico in Chitalpa, a Common Landscape Ornamental Plant
Authors: Randall J. J. , Radionenko M. , French J. M. , Olsen M. W. , Goldberg N. P. , Hanson S. F.
Published: May 2007

Different strains of Xylella fastidiosa cause a variety of significant disease problems in agricultural and ornamental plants, including Pierce's disease in grapes, oleander leaf scorch, pecan bacterial leaf scorch, and alfalfa dwarf disease. X. fastidiosa has never been reported in New Mexico but is known to exist in surrounding states (California, Arizona, and Texas). During the summer of 2006, several chitalpa (Chitalpa tashkinensis) hybrid trees with leaf scorch symptoms and branch die back were observed in Las Cruces, NM and they tested positive for X. fastidiosa by ELISA. Additional samples from these plants and others were analyzed by ELISA, PCR (2), and cultured on XfD2 medium (1). Known positive and negative oleander samples from Arizona were included as controls. Fifteen of thirty tested chitalpa were PCR and ELISA positive, indicating that they were infected with X. fastidiosa. Bacterial colonies that were PCR positive were also recovered from 10 of the XF positive samples that were plated. DNA sequences of PCR products amplified from chitalpa and isolated bacterial colonies (GenBank Accession Nos. EF109936 and EF109937) were identical to each other, 97% similar to X. fastidiosa strain JB-USNA, and 96% similar to the Temecula 1 strain. Independent ELISA testing (Barry Hill, California Department Food and Agriculture, Sacramento, CA) confirmed our ELISA and PCR results. On the basis of these results, we conclude that X. fastidiosa is present in New Mexico and that the common landscape ornamental chitalpa is a host for X. fastidiosa. Additional work is required to determine if X. fastidiosa is pathogenic to chitalpa and to examine the relevance of this potential X. fastidiosa reservoir to agricultural production in New Mexico and other areas where chitalpa is grown.

References: (1) R. P. P. Almeida et al. Curr. Microbiol. 48:368, 2004. (2) M. R. Pooler et al. Lett. Appl. Microbiol. 25:123, 1997.
First Report of the Presence of Tomato apical stunt viroid on Tomato in Sénégal
Authors: Candresse T. , Marais A. , Ollivier F. , Verdin E. , Blancard D.
Published: May 2007

Tomato apical stunt viroid (TASVd) was initially discovered in the Ivory Coast (2). It was later reported in Indonesia and more recently was found to be responsible for severe outbreaks in protected tomatoes in Israel (1) and Tunisia (3). Although not of quarantine status, TASVd is included in the EPPO alert list. In 2005, severe arrest of apical growth and leaf chlorosis were observed in tomato samples from northern Sénégal. Tomato yellow leaf curl virus was initially identified in some samples, but since the symptoms observed were reminiscent of those associated with viroid infection, samples were analyzed by return-polyacrylamide gel electrophoresis and molecular hybridization with a Potato spindle tuber viroid (PSTVd) probe. Positive results prompted a reanalysis by reverse transcription-PCR assays specific for PSTVd or TASVd. Positive amplification was only obtained with the TASVd-specific primers (Vir+ GGGGAAACCTGGAGGAA and Vir- GGGGATCCCTGAAGGAC), and the identity of the viroid confirmed by sequencing of the amplified fragment. The complete genome sequence obtained (GenBank Accession No. EF051631) shows 94 to 96% identity with other TASVd sequences in the databases, the highest homology being with the original Ivory Coast isolate (96%, 11 mutations, and 4 indels for the 362-nt genome). These results provide new information on the diversity of TASVd and of its detrimental potential for tomato crops and represent, to our knowledge, the first report of the presence of TASVd in Sénégal.

References: (1) Y. Antignus et al. Phytoparasitica 30:502, 2002. (2) C. R. Walter. Acad. Sci. 292:537, 1981. (3) J. Th. J. Verhoeven et al. Plant Disease 90:528, 2006.
First Report of the Presence of Plum pox virus Rec Strain in Turkey
Authors: Candresse T. , Svanella-Dumas L. , Gentit P. , Caglayan K. , Çevik B.
Published: May 2007

Plum pox virus (PPV) is a detrimental virus in stone fruit crops. Six strains of PPV are recognized, one of which, PPV-Rec, represents a group of isolates sharing a unique founding recombination event (2). This strain has been reported only from central and south-central Europe. Its distribution is of interest because PPV-Rec is reported to induce only weak and transient symptoms in GF305 peach seedlings, which may complicate its detection using this widely used indicator (2). During a field trip in May 2006, a Japanese plum (Prunus salicina) tree showing leaf symptoms reminiscent of PPV infection was identified in Isparta, Turkey. A leaf sample tested by a serological lateral flow PPV Pocket Diagnostic (Central Science Laboratory, Sand Hutton, UK) gave a weak positive reaction. The presence of PPV was confirmed by grafting onto GF305 peach and by PCR amplification and sequencing of a short P3M-P4b PCR product (1; positions 8446 to 8912 on PPV-BOR3; GenBank Accession No. AY028309) spanning the end of the NIb gene and the N-terminal hypervariable end of the coat protein gene. Comparison of the sequence obtained (GenBank Accession No. EF051630) with databases unambiguously identified the isolate as belonging to the Rec strain because it contained all the PPV-Rec specific mutations in the amplified region. In keeping with this identification, the symptoms observed in GF305 were very weak, consisting only of slight vein clearing on a few leaves. This is, to our knowledge, the first report of the presence of PPV-Rec in Turkey.

References: (1) T. Candresse et al. Phytopathology 88:198, 1998. (2) M. Glasa et al. J. Gen. Virol. 85:2671, 2004.
Evaluation of Essential Oils and Their Components for Broad-Spectrum Antifungal Activity and Control of Late Leaf Spot and Crown Rot Diseases in Peanut
Authors: Kishore G. Krishna , Pande S. , Harish S.
Published: May 2007

Clove oil, cinnamon oil, and five essential oil components (citral, eugenol, geraniol, limonene, and linalool) were tested for growth inhibition of 14 phytopathogenic fungi. Citral completely inhibited the growth of Alternaria alternata, Aspergillus flavus, Curvularia lunata, Fusarium moniliforme, F. pallidoroseum, and Phoma sorghina in paper disc agar diffusion assays. Cinnamon oil, citral, and clove oil as low as 0.01% (vol/vol) inhibited the spore germination of Cercospora arachidicola, Phaeoisariopsis personata, and Puccinia arachidis by >90% in vitro. Limonene and linalool were observed to be the least antifungal against the test fungi and were not used in further studies. Clove oil (1% vol/vol) applied as a foliar spray 10 min before Phaeoisariopsis personata inoculation reduced the severity of late leaf spot of peanut up to 58% when challenge inoculated with 104 conidia ml-1. This treatment was more effective (P = 0.01) than 0.5% (vol/vol) citral, cinnamon oil, or clove oil and 1% (vol/vol) eugenol or geraniol. Seed treatment with the test compounds had no effect on the incidence of crown rot in peanut in Aspergillus niger-infested soil. However, soil amendment with 0.25% (vol/wt) clove oil and cinnamon oil reduced the preemergence rotting by 71 and 67% and postemergence wilting by 58 and 55%, respectively, compared with the nontreated control. These two treatments were more effective (P < 0.01) than geraniol on preemergence rotting, and more effective than citral, eugenol, and geraniol on postemergence wilting. All treatments significantly outperformed the nontreated control but none were as effective as thiram treatment.