bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of Rhizoctonia spp. Recovered from Crop Plants Used in Rotational Cropping Systems in the Western Cape Province of South Africa
Authors: Tewoldemedhin Y. T. , Lamprecht S. C. , McLeod A. , Mazzola M.
Published: May 2007

Isolates of Rhizoctonia spp. associated with barley, canola, clover, lucerne, lupin, annual Medicago spp. (medic), and wheat were recovered during the conduct of a 4-year (2000 to 2003) crop rotation trial in the Western Cape province of South Africa. These isolates were characterized by determining their anastomosis group (AG), in vitro optimum growth temperature, and pathogenicity toward emerging and 14-day-old seedlings of all the aforementioned crops. During the 4-year rotational trial, 428 Rhizoctonia isolates, in all, were obtained. The most abundant multinucleate AG was AG-4 HG-II (69%), followed by AG-2-1 (19%), AG-3 (8%), AG-2-2 (2%), and AG-11 (2%). The population of binucleate Rhizoctonia spp. comprised AG-K (53%), AG-A (10%), AG-I (5%), and unidentified AGs (32%). The optimal time for isolating Rhizoctonia spp. was found to be at the flowering or seedpod stage (20 to 22 weeks after planting). Temperature studies showed that isolates belonging to AG-2-2, AG-4 HG-II, and AG-K had significantly higher optimum growth temperatures than those from other AGs. In pathogenicity assays conducted on emerging as well as 14-day-old seedlings, isolates of AG-2-2 and AG-4 HG-II were the most virulent on all crops. Rhizoctonia solani AG-2-1 was highly virulent on canola, moderately virulent on medic and lupin, weakly virulent on lucerne and barley, and nonpathogenic on wheat. AG-11 isolates were moderate to weakly virulent on all crops, with the exception of barley and wheat. AG-3 was weakly virulent on canola, lupin, and medic. AG-K was the only binucleate Rhizoctonia sp. capable of inciting disease in our assays. This is the first comprehensive study to elucidate the identity and potential importance of Rhizoctonia spp. as a yield limiting factor in crop production systems in the Western Cape province of South Africa.
First Report of Leek yellow stripe virus in Garlic in the State of Guanajuato, Mexico
Authors: Pérez-Moreno L. , Córdova-Rosales Z. , Barboza-Corona E. , Ramírez-Malagón Rafael , Ramírez-Lúa J. , Ruiz-Castro S. , Silva-Rosales L.
Published: May 2007

Garlic (Allium sativum L.) can be affected by a virus complex (1) consisting of two potyviruses, Onion yellow dwarf virus (OYDV) and Leek yellow stripe virus (LYSV), and two carlaviruses, Garlic common latent virus (GCLV) and Shallot latent virus (SLV) (1). To identify the components of the virus complex that could be present in garlic plants in Guanajuato State, which is the second largest garlic producer in the country and where presumptive viral symptoms were initially observed in December 2004, a survey was carried out in six locations: San Miguel de Allende and San Luis de la Paz in northern Guanajuato; Irapuato and Villagrán in the central region; and Salamanca and Valle de Santiago in the southern part of the state. Enzyme-linked immunosorbent assay (ELISA) was carried out to detect LYSV, OYDV, GCLV, and SLV in 195 garlic leaf samples collected during January 2005 from plants with leaf yellow stripe, mosaic, enation, deformation, or dwarfism symptoms. A set of primers, previously reported and specific to the coat protein cistron of LYSV (1), were synthesized and used in a reverse transcriptase-polymerase chain reaction (RT-PCR). The amplified product (1,020 nucleotides) was cloned into plasmid pGEM T-Easy (Promega, Madison, WI) and sequenced (Gen-bank Accession No. DQ841554). Sequence analysis showed that the cloned DNA fragment shared 97% similarity with the coat protein cistron of LYSV isolate no. 3 from Okinawa (GenBank Accession No. AB194632). The fragment was then radioactively labelled and used as a probe in the RNA blot analysis of all samples to confirm the ELISA results of LYSV. Of the 195 samples, 64 tested positive by RNA blot analysis. Forty-one of these were also positive by ELISA for LYSV. Preliminary, positive ELISA results were also obtained for OYDV, GCLV and SLV. To our knowledge, this is the first report of LYSV in the State of Guanajuato and in Mexico. The correct identification of viruses present in garlic will help to use the appropriate strategies to reduce viral incidence in this garlic-producing region.

Reference: (1) T. V. M. Fajardo et al. Fitopatol. Bras. 26:619, 2001.
A New Report of Cymbidium spp. Pseudobulb Rot Orchestrated by Erwinia carotovora, Fusarium oxysporum, and Mucor hiemalis f. sp. hiemalis
Authors: Sen S. , Acharya R. , Saha A. , Acharya K.
Published: May 2007

Cymbidium spp. is an orchid of great horticultural value cultivated extensively in Eastern Himalaya, India. Since 1995, growers have experienced huge crop losses in every monsoon month because of pseudobulb rot. Pseudobulbs initially turned soft and pulpy followed by oozing of a dark brown liquid with a foul odor (early phase). With increasing severity, the bulbs and roots lose weight as the internal tissues gradually disintegrate (middle phase). Finally, the bulb becomes hollow, fibrous, and dry causing death of the plant (later phase). Surveys from 2002 to 2005 showed that disease incidence ranged from 60 to 100%. Rotted tissue was plated on nutrient agar and potato dextrose agar media. Three organisms were consistently isolated from 50 samples collected from 30 different localities. They were identified as Erwinia carotovora (2), Fusarium oxysporum (3), and Mucor hiemalis f. sp. hiemalis (1) and were predominant at the earlier, middle, and later stages of disease, respectively. Identifications were further confirmed by the Agricultural Research Institute (ARI), Pune, India. Pseudobulbs were surface sterilized with 0.5% sodium hypochlorite for 1 min, washed by sterile distilled water, and dipped separately into three different spore/cell suspensions (105 CFU/ml) for 1 min. Another set of sterilized bulbs was dipped first into E. carotovora, then into F. oxysporum 12 days later, and then into M. hiemalis f. sp. hiemalis 15 days after the second dip. For the control set, bulbs were dipped into sterile distilled water. Samples were incubated aseptically at 20°C with a relative humidity of 80%, and all inoculated bulbs were evaluated for disease 47 days after the first inoculation. When samples were inoculated separately, E. carotovora exhibited maximum (70%) tissue disintegration followed by F. oxysporum (30%) and M. hiemalis f. sp. hiemalis (10%), but none of the individual pathogens caused 100% tissue disintegration. Complete destruction was observed after 47 days of first inoculation when these three pathogens were inoculated consecutively according to their serial occurrence. It is an interesting report on host-pathogen combination as three pathogens act in sequence toward ultimate demolition of the host. We report this rot as a synergistic activity of three pathogens to cause an uncontrolled epidemic disease of Cymbidium spp.

References: (1) J. C. Gilman. Page 37 in: A Manual of Soil Fungi. Iowa State College Press. Ames, IA, 1945. (2) J. G. Holt. Page 469 in: Bergey's Manual of Systematic Bacteriology. Vol. I. Williams and Wilkins. Baltimore/London, 1984, (3) C. V. Subramaniam. Page 657 in: Hyphomycetes. Indian Council of Agricultural Research (ICAR). New Delhi, 1971.
First Report of Grapevine leafroll associated virus-3 in American Vitis spp. Grapevines in Washington State
Authors: Soule M. J. , Eastwell K. C. , Naidu R. A.
Published: May 2007

Washington State is the largest producer of juice grapes (Vitis labruscana ‘Concord’ and Vitis labrusca ‘Niagara’) and ranks second in wine grape production in the United States. Grapevine leafroll disease (GLD) is the most wide spread and economically significant virus disease in wine grapes in the state. Previous studies (2) have shown that Grapevine leafroll associated virus-3 (GLRaV-3) is the predominant virus associated with GLD. However, little is known about the incidence and economic impact of GLD on juice and table grapes. Because typical GLD symptoms may not be obvious among these cultivars, the prevalence and economic impact of GLD in Concord and Niagara, the most widely planted cultivars in Washington State, has received little attention from the grape and nursery industries. During the 2005 growing season, 32 samples from three vineyards and one nursery of ‘Concord’ and three samples from one nursery of ‘Niagara’ were collected randomly. Petiole extracts were tested by single-tube reverse transcription-polymerase chain reaction (RT-PCR; 3) with primers LC 1 (5′-CGC TAG GGC TGT GGA AGT ATT-3′) and LC 2 (5′-GTT GTC CCG GGT ACC AGA TAT-3′), specific for the heat shock protein 70 homologue (Hsp70h gene) of GLRaV-3 (GenBank Accession No. AF037268). One ‘Niagara’ nursery sample and eleven ‘Concord’ samples from the three vineyards tested positive for GLRaV-3, producing a single band of the expected size of 546 bp. The ‘Niagara’ and six of the ‘Concord’ RT-PCR products were cloned in pCR2.1 (Invitrogen Corp, Carlsbad, CA) and the sequences (GenBank Accession Nos. DQ780885, DQ780886, DQ780887, DQ780888, DQ780889, DQ780890, and DQ780891) compared with the respective sequence of a New York isolate of GLRaV-3 (GenBank Accession No. AF037268). The analysis revealed that GLRaV-3 isolates from ‘Concord’ and ‘Niagara’ share nucleotide identities of 94 to 98% and amino acid identities and similarities of 97 to 98% with the Hsp70h gene homologue of the New York isolate of GLRaV-3. Additional testing by double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) using antibodies specific to GLRaV-3 (BIOREBA AG, Reinach, Switzerland) further confirmed these results in the ‘Niagara’ and two of the ‘Concord’ isolates. GLRaV-3 has previously been reported in labrusca cvs. Concord and Niagara in western New York (4) and Canada (1), but to our knowledge, this is the first report of GLRaV-3 in American grapevine species in the Pacific Northwest. Because wine and juice grapes are widely grown in proximity to each other in Washington State and grape mealybug (Pseudococcus maritimus), the putative vector of GLRaV-3, is present in the state vineyards, further studies will focus on the role of American grapevine species in the epidemiology of GLD.

References: (1) D. J. MacKenzie et al. Plant Dis. 80:955, 1996. (2) R. R. Martin et al. Plant Dis. 89:763, 2005. (3) A. Rowhani et al. ICGV, Extended Abstracts, 13:148, 2000. (4) W. F. Wilcox et al. Plant Dis. 82:1062, 1998.
Genetic Relationships Among Magnaporthe poae Isolates from Turfgrass Hosts and Relative Susceptibility of ‘Penncross’ and ‘Penn A-4’ Creeping Bentgrass
Authors: Tredway L. P.
Published: May 2007

Isolates of Magnaporthe poae from turfgrass hosts were analyzed for mating type, genetic relatedness according to ITS sequences, reaction to a previously developed species-specific poly-merase chain reaction (PCR) assay, and virulence on two creeping bentgrass cultivars in growth chamber experiments. Analysis of internal transcribed spacer (ITS) sequences revealed three clades, designated A, B, and C. Clade A contained isolates of both mating types from creeping bentgrass, annual bluegrass, and Kentucky bluegrass. Clade B contained only mating type ‘A’ isolates from annual bluegrass, whereas Clade C contained only mating type ‘a’ isolates from creeping bentgrass. The M. poae PCR assay failed to positively identify several North Carolina isolates from annual bluegrass and creeping bentgrass. M. poae isolates from Kentucky blue-grass were most virulent toward creeping bentgrass in growth chamber experiments. Although isolates of M. poae are not host specific, certain ITS clades may have a limited host or geographical range. The improved creeping bentgrass cv. Penn A-4 was more susceptible to summer patch than cv. Penncross. Additional research is needed to develop methods for accurate diagnosis of summer patch and other patch diseases in creeping bentgrass and to determine how creeping bentgrass cultivars vary in their susceptibility to these root pathogens.
First Report of Blueberry Leaf Spot Caused by Cylindrocladium colhounii in China
Authors: Luan Y. S. , Feng L. , An L. J.
Published: May 2007

During late July and early August of 2005, leaf spot symptoms were observed in a blueberry nursery at a plantation in Dalian, which to our knowledge, lies within the largest blueberry-production area in China. Symptoms were observed primarily on lowbush species, for example Blomidon, as well as half-highbush cultivars. A slow-growing, white mycelium from the margin of necrotic leaf spots was recovered on potato dextrose agar (PDA). The following morphological traits were observed: erect conidiophores that branch twice and were terminated in a stiped, clavate phialide; hyaline, cylindrical, four-celled conidia; and globose, reddish brown, aggregated chlamydospores. Conidiophores (including stipes and terminal phialides) were 305 to 420 × 5 to 9 μm; primary branches were 9 to 45 × 5 to 6.3 μm; secondary branches were 9 to 17.3 × 3.1 to 4.5 μm; phialides were 7.8 to 17.5 × 2.5 to 6 μm; stipes (from the highest branch area to vesicle) were 150 to 270 μm long; and vesicles were 13 to 30 × 2 to 4.5 μm. Conidia were 50 to 72 × 4 to 5.5 μm. Chlamydospores were 15 to 20 μm in diameter. Koch's postulates were fulfilled by spray inoculating two healthy cultivars with conidiophores homogenized in axenic water. As a control, two healthy plants were sprayed with axenic water. Plants were placed inside plastic bags to maintain humidity and incubated in a growth chamber at 26°C under fluorescent light for 14 h and 20°C in darkness for 10 h. After 2 days, the plastic bags were removed and plants were maintained under the same conditions. After 4 days, small-to-medium brown spots with purplish margins were observed on the adaxial side of leaves from inoculated plants, but not from control plants. Fungi isolated from these lesions had the same morphological traits as the ones isolated previously from field plants. The morphological descriptions and measurements were similar to Cylindorocladium colhounii (2). The 5.8S subunit and flanking internal transcribed spacers (ITS1 and ITS2) of rDNA and the β-tubulin gene were amplified from DNA extracted from single-spore cultures using the ITS1/ITS4 primers and T1/Bt2b primers, respectively, and sequenced (1). The ITS and β-tubulin gene sequences were similar to C. colhounii STE-U 1237 (99%; GenBank Accession No. AF231953) and C. colhounii STE-U 705 (99%; GenBank Accession No. AF231954), respectively. The morphology, secondary conidiation, and sequences of ITS and β-tubulin gene identify the causal fungus as C. colhounii. To our knowledge, this is the first report of C. colhounii on blueberry in China or in the world.

References: (1) P. W. Crous et al. Can. J. Bot. 77:1813, 1999. (2) T. Watanabe. Page 222 in: Dictorial Atlas of Soil and Seed Fungi. CRC Press, Inc., Boca Raton, Fl, 1994.
Prunus Host Range of Plum pox virus (PPV) in the United States by Aphid and Graft Inoculation
Authors: Damsteegt V. D. , Scorza R. , Stone A. L. , Schneider W. L. , Webb K. , Demuth M. , Gildow F. E.
Published: May 2007

Plum pox (Sharka) is a serious virus disease of stone fruits caused by the Plum pox virus (PPV). To determine which species could function as potential hosts and virus reservoirs, we used aphid transmission and bud or chip grafting to evaluate the susceptibility of commercial, ornamental, and wild Prunus species to isolates of PPV found in Pennsylvania, USA. Following inoculation, test trees were observed for symptoms, analyzed by enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR), back-assayed to healthy peach, and followed through at least four cold-induced dormancy (CID) cycles over 4 years. Thirty-one of 33 Prunus species and cultivars were systemically infected following aphid transmission. Systemic infection could not be detected in P. cerasus (sour cherry) and P. × ‘Snofozam’ (Snow Fountains) despite repeated aphid inoculation attempts. Following grafting of PPV-infected budwood, all 40 species and varieties became infected, although species differed in their susceptibility. Within most species, some individual plants remained PPV negative throughout the study despite repeated inoculations. Infection in some species could be detected only through quantitative reverse transcription (RT)-PCR. Most species displayed clear symptoms, were highly positive by ELISA and RT-PCR, and could be back-inoculated into peach seedlings following CID. Our results indicate that a wide range of native and ornamental Prunus species are susceptible to U.S. isolates of PPV-D.
Evaluation of DNA Amplification Methods for Improved Detection of “Candidatus Liberibacter Species” Associated with Citrus Huanglongbing
Authors: Li Wenbin , Hartung John S. , Levy Laurene
Published: May 2007

Citrus huanglongbing (HLB), also known as citrus greening or citrus yellow shoot, is considered the most serious disease of citrus worldwide. The disease has Asian, African, and American forms caused by “Candidatus Liberibacter asiaticus”, “Ca. L. africanus”, and “Ca. L. americanus”, respectively, which can be spread efficiently by the psyllid vectors Diaphorina citri and Trioza erytreae and through contaminated plant materials. Infected citrus groves are usually destroyed or become unproductive in 5 to 8 years. The presumed low concentration and uneven distribution of the pathogens in citrus plants and vector insects make the phloem-limited bacterium difficult to detect consistently. In this study, we compared and validated four conventional polymerase chain reaction (PCR)-based protocols, one loop-mediated isothermal amplification (LAMP) protocol, and three TaqMan real-time PCR protocols. The detection sensitivity of the validated conventional PCR assays reported are improved compared with the original protocols. All of the validated conventional and the newly developed real-time methods were reliable for confirmatory tests for the presence of “Ca. Liberibacter spp.” in symptomatic samples. There were no differences in assay specificity among the standard format PCR-based methods evaluated. The TaqMan real-time PCR was 10- to 100-fold more sensitive than conventional PCR and LAMP, showing the potential to become a valuable tool for early detection and identification of “Ca. Liberibacter spp.” prior to the appearance of disease symptoms. The methods validated in this study will be very useful for regulatory response, effective management of infected trees, and development of a “Ca. Liberibacter spp.”-free nursery system.
Molecular Detection of Plasmodiophora brassicae, Causal Agent of Clubroot of Crucifers, in Plant and Soil
Authors: Cao Tiesen , Tewari Jalpa , Strelkov Stephen E.
Published: May 2007

Clubroot of crucifers, caused by Plasmodiophora brassicae, recently has been identified in canola (Brassica napus) fields in Alberta, Canada. An effective strategy for managing the disease is to avoid planting cruciferous crops in P. brassicae-infested soil, because the pathogen produces resting spores that can remain infectious for many years. A simple, one-step polymerase chain reaction (PCR) protocol was developed to detect the pathogen in plant and soil samples. The primers TC1F and TC1R, based on a P. brassicae partial 18S ribosomal RNA (rRNA) gene sequence from GenBank, yielded a 548-bp product in the optimized PCR. A second pair of primers, TC2F and TC2R, which amplified a fragment of the 18S and internal transcribed spacer (ITS) 1 regions of the rDNA repeat, also was tested and produced a 519-bp product. Neither set of primers amplified any DNA fragment from noninfected plant hosts, noninfested soil, or common soil fungi and bacteria tested in this study. Quantities of 100 fg or less of total P. brassicae DNA, or 1 × 103 resting spores per gram of soil, could be detected consistently using these primers and PCR protocol, corresponding to an index of disease of 11% or lower when the soil was bioassayed. The protocol also enabled detection of P. brassicae in symptomless root tissue 3 days after inoculation with the pathogen. Therefore, the PCR assay described in this study could provide a reliable diagnosis for routine detection of P. brassicae in plant and soil materials in a specific and rapid manner.
Seed Transmission of Dahlia mosaic virus in Dahlia pinnata
Authors: Pahalawatta V. , Druffel K. , Pappu H. R.
Published: May 2007

Dahlia is an economically important ornamental crop in the United States and several other countries in the world. Among the viral diseases that affect dahlia, Dahlia mosaic virus (DMV) is considered to be the most widespread and to have the greatest impact on flower production. Using grow-out tests followed by polymerase chain reaction (PCR)-based testing of the seedlings, dahlia seed obtained from three different sources were shown to contain DMV. Additionally, the distribution of DMV in various parts of the dahlia seed was determined by PCR. Growout tests revealed a high rate of seed transmission. DMV was detected in cotyledons and, rarely, in the seed coat. The virus also was detected in pollen collected from infected plants. In addition to vegetative propagation, seedborne infection could be contributing to the spread of DMV in dahlia. Use of virus-free seed and vegetative material would result in reduced incidence of the disease.
Phytophthora infestans Mating Types on Tomato (Solanum lycopersicum) in Southern Spain
Authors: Segura J. M. , de Cara M. , Santos M. , Tello J.
Published: May 2007

During 2004, an unusual spread of Phytophthora infestans on tomato plants in greenhouses located in Almería and Granada provinces, southern Spain, was observed. Infected plants had water-soaked, brown spots on leaves and stems and necrotic areas with white mold on the surface of fruits. Three isolates were obtained by plating diseased tissue on V8 juice agar medium and maintained on rye agar at 18°C. These isolates were analyzed for the mating type. Crosses were carried out using V8 juice agar and rye agar. The two parental isolates US1 (A1) and US8 (A2) were both provided by W. E. Fry, Cornell University, Ithaca, NY. Two of the Spanish isolates were homothallic and the other isolate belonged to the uncommon mating type A1A2. To confirm the occurrence of the two mating types, 43 single-sporangium progeny were produced and analyzed from the A1A2 mating type. Thirty eight isolates were A1, two were A2, one was A1A2 mating type, and two were sterile. Assessment of five single-sporangium progeny from the homothallic type resulted in two A1, two homothallic, and one sterile isolate. A1A2 isolates produced oospores when crossed with either A1 or A2, but not when self-crossed. Previously, the A1A2 mating type has been found in Israel in the field and was obtained from oospores produced on tomato seeds (2,3). Since 2003, mating types of P. infestans isolates recovered from potato (60) and tomato (8) in southern Spain have been characterized. Seventy-five percent of the isolates recovered from potato were A1 and 25% were A2 mating types. Isolates recovered from tomato were 50% A1 and 50% A2 (1). To our knowledge, this is the first report of the occurrence of the A1A2 mating type and homothallic P. infestans isolates on tomato in Spain.

References: (1) E. Andujar et al. Congr. Sociedad Española de Fitopatol. 12:244, 2004. (2) E. Rubin and Y. Cohen. Phytoparasitica 32:237, 2004. (3) E. Rubin and Y. Cohen. Plant Dis. 90:741, 2006.
First Report of Tomato (Lycopersicon esculentum) Pith Necrosis Caused by Pseudomonas fluorescens and P. corrugata in the Kingdom of Saudi Arabia
Authors: Molan Y. , Ibrahim Y.
Published: May 2007

From 2002 to 2004, tomato (Lycopersicon esculentum) plants with external stem lesions, adventitious roots, and necrotic pith that was hollowed or chambered were received by the Clinical Lab of the Plant Protection Department from eight greenhouses in the Riyadh, Abha, and El-Kharj regions of Saudi Arabia. Bacteria were isolated on nutrient agar or King's medium B (KMB) from the stems of tomato plants cv. Red Gold, the cultivar most commonly grown in greenhouses. Gram-negative, rod-shaped bacteria were consistently isolated from stems with symptoms of pith necrosis. They were identified as Pseudomonas fluorescens (biotype I) and P. corrugata on the basis of morphological, physiological, and biochemical tests (2). Isolates of P. fluorescens isolated from Abha and El-Kharj were fluorescent on KMB, aerobic, and positive for oxidase, arginine dihydrolase, and gelatin liquefaction. Furthermore, all isolates produced levan-type colonies on sucrose nutrient agar and utilized glucose, 2-ketogluconate, sucrose, and sorbitol. They were negative for tobacco hypersensitivity and nitrate reduction. The strains of P. corrugata isolated from Riyadh were nonfluorescent, aerobic, and positive for oxidase, nitrate reductase, arginine dihydrolase, and utilization of malonate, alanine, trehalose, arginine, mannitol, and m-inositol. They were negative for levan, pectinase, tobacco hypersensitivity, and utilization of cellobiose and sorbitol. The identity of bacterial species was confirmed by Biolog analysis (carbon source utilization at 37°C), with a similarity index of 0.75 for P. corrugata and 0.71 for P. fluorescens. Four-week-old tomato plants (cv. Red Gold) were inoculated by injecting 50 μl of a bacterial suspension into the axils of the first true leaves. The bacterial suspension was prepared from 24-h-old cultures with sterile distilled water. Sterile distilled water was used as the negative control. After inoculation, plants were covered with polyethylene bags for 24 h to maintain high humidity at 25°C (1). Necrotic lesions surrounding injection points were observed 14 days after inoculation. At 4 weeks after inoculation, all inoculated plants showed symptoms of necrotic pith similar to those observed on the samples received. Control plants injected with water remained healthy throughout the experiments. Isolates of P. fluorescens (biotype I) and P. corrugata were reisolated from inoculated plants and were identical to the original strains on the basis of Biolog analysis. To our knowledge, this is the first report of tomato pith necrosis in Saudi Arabia.

References: (1) G. Demir. J. Turk. Phytopathol. 19:63, 1990. (2) R. A. Lelliott and D. E. Stead. Methods for the Diagnosis of Bacterial Diseases of Plants. Blackwell Scientific Publications. Oxford, UK, 1987.
Tobacco ringspot virus Found in the Cardboard Cycad (Zamia furfuracea) in Florida
Authors: Baker C. A. , Adkins S.
Published: May 2007

Zamia furfuracea (Zamiaceae) is native of coastal Mexico. It is a popular houseplant and easy to grow outdoors in warm climates. In November 2005, a plant of Z. furfuracea, originally from Texas, was received at the Division of Plant Industry in Gainesville, FL. The plant had numerous chlorotic spots on the leaves that eventually became necrotic. Leaves were ground in phosphate buffer (pH 7.2) with Carborundum and used to inoculate a host range that included Chenopodium amaranticolor, C. quinoa, Gomphrena globosa, Datura stramonium, and Nicotiana benthamiana. Systemic symptoms were seen in C. quinoa (necrotic lesions), G. globosa (stunting), D. stramonium (chlorotic ringspots), and N. benthamiana (wavy line patterns) 1 to 2 weeks after inoculation. C. amaranticolor showed only small necrotic local lesions. In further host range studies, systemic infections of Beta vulgaris, D. metaloides, Lactuca sativa, N. clevelandii, Pisum sativus, Petunia hybrida, Zinnia elegans (symptomless), and Cucumis sativa were observed. However, no infection of Zea mays, Verbena hybrida, Glycine max, Phaseolus vulgaris, Catharanthus roseus, Arachis hypogaea, Trifolium spp., Vigna unguiculata, Vicia faba or Digitalis spp. was detected. Inclusions observed in leaf strips of N. benthamiana and D. stramonium indicated a possible infection of this plant with a nepovirus (1). A 337-bp fragment was amplified from total RNA isolated from an inoculated D. stramonium using reverse transcription-PCR with nepovirus group primers provided by Agdia Inc. (Elkhart, IN). Sequence analysis indicated that the nucleotide (nt) and deduced amino acid (aa) sequences of the fragment were 89 to 91% and 91 to 95% identical, respectively, to sequences of the RNA-dependent RNA polymerase gene for Tobacco ringspot virus (TRSV) contained in GenBank (Accession Nos. U50869 and AJ698718). This region was only 50% (nt) and 38% (aa) identical to Cycas necrotic stunt virus (GenBank Accession No. NC_003791), a nepovirus previously reported to infect cycads (2). The original plant, symptomatic inoculated hosts, and the symptomless zinnia tested positive by double-antibody sandwich-ELISA using commercially available antiserum for TRSV (Agdia, Inc.), further confirming the presence of TRSV. Although the virus infecting Z. furfuracea has a more restricted host range than that reported for TRSV, the serology and gene sequence indicates that this virus is a unique isolate of TRSV.

References: (1) J. R. Edwardson and R. G. Christie. University of Florida, Institute of Food and Agricultural Sciences, Bull. 894. 1996. (2) S. S. Han et al. Arch. Virol. 147:2207, 2002.
Management of Xiphinema americanum and Soybean Severe Stunt in Soybean Using Crop Rotation
Authors: Evans T. A. , Miller L. C. , Vasilas B. L. , Taylor R. W. , Mulrooney R. P.
Published: May 2007

Soybean severe stunt (SSS), caused by the Soybean severe stunt virus (SSSV), is a soilborne virus disease affecting soybean (Glycine max) first described in Delaware in 1988. Lack of breeding programs directed at incorporating resistance to SSSV in new cultivar releases necessitated alternative methods of SSS control. The effect of crops in 2-year rotations on the dagger nematode (Xiphinema americanum), the putative nematode vector of SSSV, and SSS severity were examined. Two years of continuous corn or grain sorghum, wheat followed by ‘HT-5203’ soybean, or 2-year fallow, reduced both dagger nematode density in the soil and SSS severity. Crop rotation to the SSSV-tolerant HT-5203 soybean as a single crop for 2 years increased dagger ematode populations and SSS severity. Greenhouse studies indicated that corn, wheat, marigold, castor, and fallow treatments reduced dagger nematodes the most after 14 weeks compared with ‘Essex’ and HT 5203 soybean.
First Report of Trichodorus similis from the Czech Republic (Nematoda: Trichodoridae)
Authors: Kumari S. , Vohanka J. , Decraemer W.
Published: May 2007

Members of the Trichodoridae can cause substantial crop losses directly by feeding on plant roots and indirectly as vectors of tobraviruses; both vector and virus are polyphagous. Although trichodorid nematodes are important pests of agricultural crops, no data are available on the presence or extent of these nematodes in the Czech Republic. In June 2005, three soil samples from the rhizosphere of a Quercus sp. at Cerveny Vrch yielded a population of Trichodorus similis Seinhorst, 1963. Specimens were extracted from soil by a decanting-sieving method, heat killed, and fixed in triethanolamine formalin (TAF), and processed and mounted in anhydrous glycerin. Nematodes were identified by morphological and morphometrical characters (2). Classical identification of these nematodes was further verified by molecular study. A single, male specimen was temporarily mounted in distilled water on a glass slide and relaxed with gentle heat. Measurements and photographs were taken, and the specimen was transferred to a 0.5-ml Eppendorf tube containing 0.25 M NaOH. Total genomic DNA was prepared by a rapid technique (4). Morphometric data of the male specimen used for DNA study are: body length 867 μm; body width 81 μm; onchiostyle length 44 μm; spicule length 36 μm; distance of anterior cervical papilla (CP)1 from anterior end 39 μm, CP1 to CP2 25 μm, CP2 to CP3 22 μm; posterior precloacal supplement (SP1) to cloacal opening 27 μm, distance SP1 to SP2 32 μm, distance SP2 to SP3 39 μm. The following primers were used in the PCR reaction: species-specific sense primer SIMIREV2 (5′-CACTCGTCGGACTCAAACC-3′) and universal antisense primer UNIVERSAL (5′-CCCGTCGCTACTACCGATT-3′) (1). A single fragment of approximately 452 bp was amplified. The D2 and D3 expansion regions of the large subunit 28S rDNA were amplified using the primer D2A (5′-ACAAGTACCGTGAGGGAAAGTTG-3′) and D3B (5′-TCGGAAGGAACCAGCTACTA-3′ (3). The region was sequenced after purification of PCR products from the gel slice with a Qiagen gel purification kit (Qiagen Inc., Valencia, CA). The obtained sequence was deposited in Genbank (Accession No. DQ832183). The obtained sequence was compared by BLAST in NCBI and the results showed strong similarities with T. similis (Accession No. AM180730). To our knowledge, this is the first report of T. similis associated with a deciduous forest in the Czech Republic. Taking into account the agricultural importance of trichodorids and tobraviruses as plant pathogens, there is a need for a comprehensive survey of these taxa in the Czech Republic. The damage level threshold is in the case of virus vector species equivalent to a single nematode. Therefore, information on these plant parasites would be useful for developing nematode management strategies.

References: (1) K. Boutsika et al. Plant Pathol. 53:110, 2004. (2) W. Decraemer and P. Baujard. Fundam. Appl. Nematol. 21:37, 1998. (3) P. De Ley et al. Nematology 2:591, 1999. (4) J. M. Stanton. Australas. Plant Pathol. 27:112, 1998.
Effects of Row Pattern, Seeding Rate, and Inoculation Date on Fungicide Efficacy and Development of Peanut Stem Rot
Authors: Sconyers L. E. , Brenneman T. B. , Stevenson K. L. , Mullinix B. G.
Published: May 2007

Two field studies were conducted in 2000, 2001, and 2002 to determine the effects of row pattern (91.4-cm single or 20.3-cm twin) and seeding rate (single: 12.5, 17.4, or 22.6 seed m-1or twin: 6.2, 8.9, or 11.5 seed m-1) on peanut stem rot (Sclerotium rolfsii) development. The first study was conducted in a naturally infested field and relative efficacy of azoxystrobin (Abound 2.08 F, applied at a rate of 0.3 kg a.i. ha-1 at 60 and 90 days after planting [DAP]) also was evaluated. In this study, stem rot incidence was significantly greater (P < 0.05) in single rows planted at high seeding rates than in twin rows planted at any of the seeding rates. Row pattern did not affect azoxystrobin efficacy, and disease incidence was nearly half as much in twin rows treated with fungicide than incidence in single rows treated with fungicide. In the second field study, individual peanut plants in fumigated plots were inoculated once with S. rolfsii at 50, 70, or 90 DAP. Stem rot incidence at harvest was significantly greater on plants inoculated 50 DAP than plants inoculated 70 or 90 DAP. The incidence of spread to adjacent rows was higher in plots where plants were inoculated at 50 than at 90 DAP. Plants inoculated 90 DAP had less disease at harvest, but often developed more severe symptoms within the first week after inoculation compared with plants inoculated 50 or 70 DAP. Symptoms were more severe in single than in twin rows, and at the higher seeding rates. Data from these studies suggest that the physical spacing between plants is a critical factor in stem rot development both on individual plants and in plant populations.
Identification and Characterization of a Novel Tobamovirus from Tropical Soda Apple in Florida
Authors: Adkins Scott , Kamenova Ivanka , Rosskopf Erin N. , Lewandowski Dennis J.
Published: May 2007

Foliar symptoms suggestive of virus infection were recently observed on the noxious weed tropical soda apple (Solanum viarum) in Florida. An agent was mechanically transmitted to Nicotiana benthamiana, and virions were isolated from systemically infected leaves. Rod-shaped particles ~300 nm in length were observed in the partially purified preparations by electron microscopy. The host range determined by mechanical inoculation with purified virions included all tested plants in the Solanaceae (16 species including the important vegetable crops, pepper and tomato) and Chenopodiaceae (2 species) but excluded all tested plants in the Ama-ranthaceae, Apocynaceae, Brassicaceae, Caryophyllaceae, Cucurbitaceae, Fabaceae, Lamiaceae, Malvaceae, and Tropaeolaceae, including several common virus indicator hosts. Comparisons of the coat and movement protein nucleotide and deduced amino acid sequences of this putative tobamovirus with recognized members of this genus, indicate that it is a novel tobamovirus that shares the highest level of sequence identity with Pepper mild mottle virus followed by other members of the Solanaceae-infecting subgroup of tobamoviruses. The virus, for which the name Tropical soda apple mosaic virus (TSAMV) is proposed, was found to be widespread in tropical soda apple in peninsular Florida during an initial survey. TSAMV contamination of seed from infected tropical soda apple plants was found, suggesting that seed transmission may be important for TSAMV dissemination and epidemiology.
Relative Ratio of Mature Pustules: A Simple Method to Assess Partial Resistance of Barley to Puccinia hordei
Authors: Jiang Guo-Liang , Marcel Thierry C. , Martínez Fernando , Niks Rients E.
Published: May 2007

In plant breeding and germplasm evaluation, large-scale assessment of quantitative resistance is desirable, but feasible only if a simple and accurate measure is available. In several plant-pathogen systems, latent period (LP) is a parameter that is well correlated with the level of partial resistance observed in field trials. However, measuring LP or relative LP (RLP), i.e., relative to the reference accessions, is laborious. We investigated the value of relative ratio of mature pustules (RRMP, relative to the susceptible control) as a simple and rapid alternative to replace LP estimation in barley to barley leaf rust (Puccinia hordei). A set of 103 F9 recombinant inbred lines (RILs) derived from a cross L94 × Vada was sown in a greenhouse compartment, and was inoculated at the seedling stage with isolate Uppsala or 24, and at the adult plant stage with isolate 24. In demarcated sections of leaves, the number of mature pustules was counted several times after inoculation. The ratio of mature pustules (RMP) and LP50 were calculated to assess RRMP and RLP, respectively, and to identify the quantitative trait loci (QTLs) contributing to the genetic variation. The contrasts in RRMP among accessions were highest when the susceptible reference line had developed 70 to 90% mature orange pustules, the immature infection sites being visible as pale flecks. At this optimal time of observation, the correlation between RRMP and RLP in both the seedling stage and the adult plant stage was highly significant (r = -0.82 ~-0.98). Compared with RLP, RRMP was much easier and simpler to measure and still showed good correspondence with RLP in the identification of QTLs for partial resistance. In another experiment at the seedling stage with 25 barley cultivars and lines inoculated with isolate 1.2.1, the coefficient of correlation between RRMP and RLP was -0.98. Therefore, we conclude that RRMP should have great application potential in breeding programs and germplasm screening and could be used in fundamental studies as well.
First Report of Canker Disease Caused by Botryosphaeria parva on Cork Oak Trees in Italy
Authors: Linaldeddu B. T. , Franceschini A. , Luque J. , Phillips A. J. L.
Published: May 2007

A survey was carried out in the spring of 2003 to study the fungi associated with declining trees in a cork oak (Quercus suber L.) forest located in Sassari Province, Sardinia, Italy (40°52′N, 9°01′E) at an altitude of 150 m (above sea level). Several isolates obtained from live twigs and branches showing sunken necrotic bark lesions were identified as Fusicoccum parvum Pennycook & Samuels (teleomorph Botryosphaeria parva Pennycook & Samuels). Neither pycnidia nor ascomata were observed on the symptomatic samples collected. On potato dextrose agar (PDA) at 25°C, the isolates developed an aerial and compact mycelium, initially white but becoming gray after 4 to 6 days, and produced pycnidia after 1 month on sterile cork oak twigs placed on the surface of PDA. Conidia from culture were hyaline, ellipsoidal to fusiform, externally smooth, thin walled, nonseptate, 12 to 19 (15.5) × 5.5 to 8.5 (6.5) μm, with length/width ratio of 2.4 ± 0.1 (mean ± standard error). Identity was confirmed by analysis of the nucleotide sequences of the internal transcribed spacer (ITS) from the rRNA repeat and the translation elongation factor 1-alpha (EF1-α), as done elsewhere (1,4). BLAST searches at GenBank showed a high identity with reference sequences (ITS: >99%; EF1-α: 100%). Representative sequences of both regions were deposited at GenBank (ITS: Accession No. DQ487157; EF1-α: Accession No. DQ487158). Pathogenicity tests were carried out on seven 2-year-old cork oak seedlings maintained in a greenhouse at 14 to 26°C with the B. parva strain CBS 119937 obtained in this study. A mycelial plug (3 to 4 mm2) taken from the margin of an actively growing colony on PDA was put in a shallow wound made by a scalpel on the basal part of the stem of each seedling. Sterile PDA plugs were placed into similar wounds on three control seedlings. The inoculation points were wrapped in Parafilm to retain moisture for 1 week. After 4 weeks, all seedlings inoculated with B. parva died and showed a collapse of the stem cortical tissues associated with dark brown discolorations and vascular necrosis measuring 10.9 ± 0.4 cm. No symptoms were visible in the control seedlings. The pathogen was reisolated from all the inoculated seedlings, thus fulfilling Koch's postulates. The results confirm the virulence of this fungus and point to its possible involvement in the aetiology of cork oak decline. B. parva is a cosmopolitan, plurivorous pathogen causing disease in several hosts of economic importance, such as grapevine (3), kiwi (2), and Eucalyptus spp. trees (1). To our knowledge, this is the first report of B. parva causing canker disease on cork oak trees.

References: (1) A. Gezahgne et al. S. Afr. J. Bot. 70:241, 2004. (2) S. R. Pennycook and G. J. Samuels. Mycotaxon 24:445, 1985. (3) A. J. L. Phillips. Phytopathol. Mediterr. 41:3, 2002. (4) B. Slippers et al. Mycologia 96:83, 2004.
First Report of Blueberry scorch virus in Black Huckleberry in British Columbia
Authors: Wegener L. A. , Punja Z. K. , Martin R. R.
Published: May 2007

Blueberry scorch virus (BlScV), an aphid-borne carlavirus, causes a serious disease of highbush blueberry (Vaccinium corymbosum L.) in North America and Europe. Symptoms of BlScV infection on highbush blueberry include necrosis of flower blossoms and young leaves, shoot blight, and chlorosis. Currently, cranberry (Vaccinium macrocarpon L.) is the only other natural host of BlScV. In July 2004, wild black huckleberry (Vaccinium membranaceumL.) was sampled in the Kootenay Region of southeastern British Columbia. Foliar tissues were sampled during 2004 from 11 bushes from a clearing on the side of a mountain near Crawford Bay, BC, Canada and tested by double-antibody sandwich-ELISA using polyclonal antiserum (Agdia Inc., Elkhart, IN). BlScV was detected in 6 of the 11 bushes sampled and in the positive control (BlScV-infected blueberry leaf tissue) and was not detected in the negative control (healthy blueberry leaf tissue). To confirm the presence of the virus, total nucleic acid was extracted from ELISA-positive huckleberry samples according to an established protocol (A. Rowhani et al. Proc. Int. Counc. Stud. Viruses Virus-Like Dis. Grapevine, Extended Abstr. 13:148, 2000). Reverse transcription-PCR was performed using pd(T)12-18 random primer (Amersham Biosciences, Piscataway, NJ) for reverse transcription and BlScV-specific primers developed against the published NJ-2 sequence of BlScV (GenBank Accession No. NC_003499). Using the forward primer, BS708F, (5′-TCAATCCGTGGTGCTACGAG-3′), and the reverse primer, BS1188R, (5′-ACAGTGCGCAATGTTCCAGT-3′), a 480-bp amplicon was obtained from each of the ELISA-positive samples, while no ampli-cons were observed for the negative control (ELISA-negative huckleberry tissue). Direct sequencing of one selected amplicon revealed 90, 84, and 77% nucleotide sequence identity and 97, 96, and 88% amino acid sequence identity with strains NJ-2, BC-1 (GenBank Accession No. AY941198) and BC-2 (GenBank Accession Nos. AY941199), respectively. BlScV-infected huckleberries were asymptomatic. The presence of BlScV in alternate hosts has implications for disease epidemiology. Testing for BlScV in Vaccinium species in and around commercial highbush blueberry plantings, as well as lowbush blueberry (V. angustifolium Aiton), rabbiteye blueberry (V. ashei Reade), other native Pacific Northwest species (V. ovatum Pursh and V. parvifolium Smith), and ornamental Vaccinium species is warranted. To our knowledge, this is the first report of BlScV infecting black huckleberry.
Reduced Incidence of Bacterial Rot on Transgenic Insect-Resistant Maize in the Philippines
Authors: Dalmacio Samuel C. , Lugod Tomas R. , Serrano Emmanuel M. , Munkvold Gary P.
Published: May 2007

In the Philippines and parts of Southeast Asia, Asian corn borer (Ostrinia furnacalis) is a serious pest of maize, and injury from this insect often is associated with the occurrence of bacterial stalk and ear rot (caused by Erwinia chrysanthemi pv. zeae). The effect of transgenic insect protection on the incidence of bacterial stalk and ear rot was studied in the Philippines with seven field trials in Mindanao and two trials in Laguna. Three transgenic hybrids (expressing Bt protein Cry1Ab) and their conventional near-isogenic counterparts were included in Mindanao, and one transgenic/conventional hybrid pair was used in Laguna (Los Banos). In the Mindanao trials, bacterial stalk rot was rated on a 1 to 9 scale approximately 2 weeks before harvest, while in Laguna, bacterial rot mortality and bacterial ear rot incidence were assessed 10 days before and at harvest, respectively. In all trials, the number of Asian corn borer tunnels was assessed by splitting stalks at harvest. Results of the trials showed significant differences between the transgenic hybrids and their conventional counterparts in terms of bacterial stalk and ear rot incidence, number of Asian corn borer tunnels, and yield. Transgenic hybrids invariably showed significantly lower bacterial stalk rot mortality and ear rot incidence, no Asian corn borer infestation, and higher yield compared with their conventional counterparts. Average yield advantage of transgenic hybrids ranged from 1.2 to 5.1 t/ha. Results confirm the important role of Asian corn borer in the initiation and spread of bacterial stalk and ear rot in maize; hence, the use of transgenic insect-resistant hybrids will have an added value in areas where this disease is prevalent.
Considerations for Verticillium Wilt Resistance Evaluation in Potato
Authors: Frost K. E. , Rouse D. I. , Jansky S. H.
Published: May 2007

Verticillium wilt (Vw), caused by the soilborne fungi Verticillium dahliae and V. albo-atrum, is an important disease of potato (Solanum tuberosum). Host plant resistance is a promising method of Vw control. Culture-based methods that quantify the pathogen in host tissue often are used for Vw resistance screening. To evaluate the processing time, accuracy, and precision of these methods, 46 clones were planted in a field naturally infested with V. dahliae to collect data on visual disease symptoms, pathogen colonization, and yield. In 2002, disease severity explained 4.34% of the variability of yield loss, but the linear relationship between stem colonization and yield loss was not significant. In 2003, stem colonization explained 57.5% of the variability of yield loss, whereas disease severity explained 1.7% of the variability of yield loss. Correlations comparing clone ranks from repeated pathogen measurements indicated that culturing sap from individual stems or bulked stems generated more repeatable clone rankings than culturing dried stems. Clone rankings were more repeatable between years if pathogen measurements were made earlier in the growing season. The results indicate a need to characterize the effect of the environment on the relationship among pathogen population sizes in planta, disease symptoms, and yield loss.