bluuebunny/crossref_metadata_2025 huggingface dataset:
Potato Tuber Necrotic Ringspot Disease Occurring in Japan: Its Association with Potato virus Y Necrotic Strain
Authors: Ohshima Kazusato , Sako Kazuya , Hiraishi Chikako , Nakagawa Akio , Matsuo Kazutoshi , Ogawa Tetsuji , Shikata Eishiro , Sako Nobumichi
Published: May 2007

Unfamiliar necrotic symptoms on or within potato tubers of cultivars Nishiyutaka and Dejima were observed in Nagasaki prefecture, Japan, in 1992. Symptoms were typically on the surface of the tuber, which either protruded at first and then became sunken, or showed necrotic spots, with necrosis within the tubers. Symptoms sometimes appeared at harvesting but more often appeared after storage for several months. Investigations revealed that the causal agents of the disease were isolates of Potato virus Y necrotic strain (PVYNTN) and the disease was potato tuber necrotic ringspot disease (PTNRD), previously reported in Europe and Lebanon. Five potato cultivars were inoculated with an isolate from necrotic tubers. The highest percentage of progeny tubers showing PTNRD was found in cv. Nishiyutaka (23.3%). In contrast, cvs. Shima-bara, Mayqueen, and Danshaku showed a low percentage of PTNRD. Additional potato tubers with PTNRD were also observed after storage of the tubers. To investigate the relatedness between isolates of PVYNTN and of necrotic strain PVYN, previously isolated in Japan, Nishiyu-taka was inoculated with an isolate of PVYN, which also induced PTNRD. Nucleotide sequences of coat protein (CP) genes of six PVYNTN isolates were determined. The CPs were 267 amino acids in length, with a substitution of one or no amino acid among each of the six isolates. The phylogenetic relationship based on nucleotide sequences of CP genes showed that these six PVYNTN isolates clustered together with PVYN isolates. This is the first report of PTNRD caused by PVYNTN isolates in Asia.
Influence of Sub- Versus Top-irrigation and Surfactants in a Recirculating System on Disease Incidence Caused by Phytophthora spp. in Potted Pepper Plants
Authors: Stanghellini M. E. , Nielsen C. J. , Kim D. H. , Rasmussen S. L. , Rorbaugh P. A.
Published: May 2007

Zoospores of Phytophthora capsici spread from inoculated source plants to healthy potted pepper plants located on separate ebb-and-flow benches when the recycled nutrient solution originated from a common reservoir. Amending the recirculating nutrient solution with a surfactant, which selectively kills zoospores, resulted in 100% control of the spread of the pathogen in an ebb-and-flow and a top-irrigated cultural system. Without a surfactant in the recirculating nutrient solution, all plants in an ebb-and-flow cultural system died within 6 weeks. In contrast, all plants in a top-irrigated cultural system died within 2 weeks after inoculation of source plants. These results suggest that the use of recycled irrigation water in an ebb-and-flow cultural system is less conducive to pathogen spread than its use in a top-irrigated cultural system, but may still serve as efficient means of inoculum movement in the absence of control measures.
Petal Blight of Sunflower Caused by Itersonilia perplexans
Authors: Seijo T. E. , McGovern R. J. , Marenco de Blandino A.
Published: May 2007

In February 1999, a cut-flower grower from Florida reported post-harvest losses of approximately 25% in Helianthus annuus (sunflower) cvs. Sunrich Orange and Sunbright. Symptoms began as small, pinpoint brown lesions on the petals, which enlarged and coalesced, leading to necrosis of the entire blossom. Symptomatic petals were surface disinfested for 30 sec with 0.5% NaOCl and suspended over plates containing acidified 25% potato-dextrose agar. Petals adhered to lids of the petri dishes by the surface tension of the water on the petals. Itersonilia perplexans Derx was consistently isolated. Inoculation of sunflower with I. perplexans was achieved using three detached, mature blossoms of the cv. Sundance Kid with their pedicels placed in sterile water. Each blossom was inoculated with 3.5 ml of a spore suspension (1 × 105 spores/ml) applied as a spray. Three noninoculated control blossoms were sprayed with sterile, distilled water. Blossoms were incubated in a controlled environment chamber at near 100% RH, a constant temperature of 18°C, and a 12-h photoperiod. Three days following inoculation all of the inoculated blossoms were symptomatic, with necrosis ranging from 50 to 100% on individual petals. I. perplexans was recovered from all of the inoculated blossoms. Noninoculated controls remained symptomless, and I. perplexans was not recovered. I. perplexans has been reported to cause lesions on the cotyledons, first true leaves, and the hypocotyl region of sunflower seedlings in Canada and Uruguay (1,2). However, this is the first report of post-harvest petal blight in sunflower caused by I. perplexans and the first report in the United States of infection of sunflower by I. perplexans.

References: (1) W. E. Sackston. Can. Phytopath. Soc. 1952:22, 1953. (2) W. E. Sackston. Phytopathology. 48:108, 1958.
Occurrence of Bacterial Brown Spot on Dry Beans in Zimbabwe
Authors: Fourie D. , Mukoko O.
Published: May 2007

A previously unreported leaf spot disease was observed in dry bean variety trials in Harare, Zimbabwe, during March 2000. It was subsequently noticed on the cultivars Ex-Rico and C20 in commercial fields. The irregular, brown, necrotic lesions (0.5 to 5 mm in diameter) resembled typical symptoms of bacterial brown spot. A fluorescent bacterium was isolated from diseased leaf samples on King's B medium. LOPAT tests (2) classified the bacterium as a Group 1a fluorescent plant pathogenic pseudomonad. Agglutination with a specific antibody reagent, from the Adgen Express test kit, positively identified the bacterium as Pseudomonas syringae pv. syringae, the causal organism of bacterial brown spot. The pathogen was distinguished from P. syringae pv. phaseoli, the halo blight organism, by its ability to utilize mannitol, inositol, and sorbitol and its ability to grow on KBC medium (3). The utilization of sucrose as a sole carbon source distinguished the pathogen from P. viridiflava. Pathogenicity of isolates was verified by inoculating young attached pods of the cultivar Teebus, using the method of Cheng et al. (1). Control plants were inoculated with a sterile syringe needle dipped in sterile distilled water. Inoculated plants were maintained in a greenhouse at 28°C day/18°C night for 4 days before being evaluated for symptom development. P. syringae pv. syringae was consistently recovered from typical lesions that developed on inoculated pods. No symptoms developed on control pods. This is the first report of bacterial brown spot caused by P. syringae pv. syringae on dry beans in Zimbabwe. P. syringae pv. syringae was, however, isolated in South Africa from extracts of bean seed received from Zimbabwe in 1996, although it is uncertain whether the disease actually occurred in the field during that specific season.

References: (1) G. Y. Cheng et al. Plant Dis. 73:419, 1989. (2) R. A. Lelliott et al. J. Appl. Bacteriol. 29:470, 1966. (3) S. K. Mohan and N. W. Schaad. Phytopathology 77:1390, 1987.
Effect of Powdery Mildew on Apple Yield and Economic Benefits of Its Management in Virginia
Authors: Yoder Keith S.
Published: May 2007

Plots were established in a ‘Ginger Gold’ apple orchard to test the effects of different powdery mildew levels on cumulative yields. Disease pressure was heaviest in 1997 but yield effects were detected each year. Primary infection in 1997 and 1998 was correlated to previous foliar mildew incidence. Five myclobutanil applications followed by three of triadimefon (M5-T3) reduced primary infections in 1997 to 19% of those on trees not receiving a mildewcide (Ck). M5-T3 gave the most reduction in mildew incidence and severity but a schedule with two less applications (M3-T3) than M5-T3 gave the highest yield. Yields were lowest on trees not receiving a mildewcide. In 1998, the weakest and the strongest treatments had two and four times more flower clusters per tree, respectively, than Ck trees. Yield of the weakest mildew treatment (six applications of sulfur, S6), was about twice that of the Ck trees; several treatments yielded more than 2× S6. Increasing the number of sulfur applications from six to eight increased mildew control and yield. Most of the treatments resulted in yields higher than the nontreated control over a 3-year period. The M3-T3 treatment regime resulted in the highest 3-year yield, whereas a slightly more effective M5-T3 regime yielded slightly less. An economic analysis of cumulative treatment benefits, using local price inputs, is included.
Comparison of Sanitation and Fungicides for Management of Botrytis Fruit Rot of Strawberry
Authors: Mertely J. C. , Chandler C. K. , Xiao C. L. , Legard D. E.
Published: May 2007

To determine the effects of sanitation on yield and incidence of Botrytis fruit rot (Botrytis cinerea) in annual strawberry, replicated experiments were conducted during the 1995-96, 1996-97, and 1998-99 seasons. Leaf sanitation (removal of senescent and necrotic leaves) and fruit sanitation (removal of unmarketable fruit from alleys between beds) were compared to a standard fungicide control program (weekly applications of captan plus four bloom applications of iprodione) and combined sanitation and fungicide treatments. Leaf sanitation reduced Botrytis fruit rot incidence from 12.6 to 8.2% over the entire 1996-97 season, and from 17.6 to 11.8% during the latter half of the 1998-99 season, compared to untreated controls. However, sanitation did not increase marketable yield. Supplementing fungicides with leaf sanitation or leaf and fruit sanitation did not improve disease control and frequently reduced yield. Fruit sanitation had no significant effect on Botrytis incidence or yield. Losses to Botrytis fruit rot in the sanitation treatments were significantly higher (P ≤ 0.05) than in the fungicide treatments each season; marketable yields were significantly lower in 1996-97 and 1998-99. Under Florida conditions, fungicides control Botrytis fruit more effectively and economically than does sanitation.
Effect of a Select Group of Seed Protectant Fungicides on Growth of Sclerotinia minor In Vitro and Its Recovery from Infested Peanut Seed
Authors: Bowen C. , Melouk H. A. , Jackson K. E. , Payton M. E.
Published: May 2007

Potato-dextrose agar containing 100 μg of streptomycin sulfate per milliliter of medium (SPDA) was amended to establish levels of 0, 2, 4, 6, 8, and 10 μg/ml of the fungicides thiophanate-methyl, carboxin, dicloran, captan, pentachloronitrobenzene (PCNB), or thiram. Fresh mycelial plugs, dry mycelial fragments, and sclerotia of Sclerotinia minor were placed onto the amended media, and mycelial growth and sclerotial germination were determined for 7 days. Thiophanate-methyl was the most effective chemical in inhibiting growth of S. minor, followed by PCNB and dicloran. Thiophanate-methyl was the only chemical that prevented germination of sclerotia of S. minor. Peanut seed naturally infested with S. minor was treated with the fungicides alone or in various combinations; control seed was treated with talcum powder. Seed was stored in polyethylene bags for 12 weeks at 24°C. To determine the incidence of viable S. minor in treated seed, seed was removed from bags, washed for 1 min in 0.2% unscented, liquid soap solution, rinsed twice in distilled water, and then dried for 15 min prior to plating on SPDA. The incidence of S. minor in talcum and thiophanate-methyl treated seed was 3.68 and 0.0%, respectively. Incidence of S. minor in seed treated with the other compounds ranged from 0.40 to 0.56%. Subsequent tests were performed using thiophanate-methyl and some of the above chemicals, in combinations or alone. These tests confirmed that thiophanate-methyl was the only compound that consistently reduced recovery of S. minor from infested seed. Germination of thiophanate-methyl treated seed equaled that of seed treated with talcum.
First Report of Leaf Blight and Stem Dieback of St. John's-Wort Caused by Diploceras hypericinum in Oregon
Authors: Putnam M. L.
Published: May 2007

St. John's-wort, Hypericum perforatum L., was formerly considered a noxious weed in the Pacific Northwest and is now grown commercially for its medicinal properties. In May 1999, plants from a 5-ha field in Jefferson County, OR, were observed with yellowing leaves and stem dieback. Lower leaves showed marginal necrosis or circular, expanding, uniformly brown, unremarkable leaf lesions that appeared randomly over the lamina and consumed from a quarter to nearly the entire leaf area. Remaining leaf tissue was chlorotic, and affected leaves eventually abscised. Infection of the stems resulted in girdling lesions 0.5 to 1.0 cm in length that caused chlorosis, wilting, and eventual dieback of tissues distal to the lesion. Diploceras hypericinum (Cesati) Diedicke was sporulating on affected stems and leaves. The fungus was isolated from surface-disinfested tissue onto 1.5% water agar. A single-spore isolate was used to inoculate 10-month-old plants raised from seed in sand. Spores from 6-week-old cultures grown on 50% potato-dextrose agar were harvested, suspended in phosphate buffer with 0.2% gelatin (PBG), and sprayed onto three plants using a DeVilbiss atomizer. Inoculum concentration was 7 × 103 and 3 ml per plant were used (plants were 8 to 10 cm tall). Three control plants were sprayed with sterile PBG. Inoculated and control plants were separately bagged to retain moisture and maintained at 22 to 25°C. Four days later, inoculated plants exhibited leaf spots similar to those originally observed, followed by stem dieback. D. hypericinum was isolated from all inoculated plants but not from control plants. The known distribution of D. hypericinum is France, Germany, Portugal, Sweden, Greece, and Ontario, Canada (1,2). This is the first report of D. hypericinum causing leaf blight and stem dieback of St. John's-wort in the United States.

References: (1) D. F. Farr et al. 1989. Fungi on Plants and Plant Products in the United States. American Phytopathological Society, St. Paul, MN. (2) T. R. Nag Raj. 1993. Coelomycetous Anamorphs with Appendage-bearing Conidia. Mycologue Publications, Waterloo, Canada.
Responses of Six EurasianUlmusCultivars to a North American Elm Yellows Phytoplasma
Authors: Sinclair W. A. , Townsend A. M. , Griffiths H. M. , Whitlow T. H.
Published: May 2007

Elms (genus Ulmus) of six clonal cultivars representing Eurasian species and hybrids were grafted when 2 to 3 years old with bark patches from U. rubra infected with an elm yellows phytoplasma or were left untreated as controls. The cultivars were U. glabra × minor ‘Pioneer’, U. minor × parvifolia ‘Frontier’, U. parvifolia ‘Pathfinder’, U. wilsoniana ‘Prospector’, and the complex hybrids ‘Homestead’ and ‘Patriot’. Trees were evaluated for infection and symptoms 1 or 2 years after inoculation. Infection was detected via the 4′,6-diamidino-2-phenylindol e·2HCl (DAPI) fluorescence test in 26 of 86 grafted trees representing five cultivars. Infection of selected trees was confirmed by polymerase chain reaction (PCR) amplification of a fragment of phytoplasmal rDNA, and the phytoplasma was identified by restriction fragment length polymorphism (RFLP) analysis of the amplified DNA using restriction enzymes AluI, RsaI, and TaqI. Elm yellows phytoplasma was also identified by nested PCR and RFLP analysis in two of seven inoculated, healthy-appearing, DAPI-negative trees and one noninoculated control tree. All RFLP profiles were identical to that of reference strain EY1. Phytoplasma-associated symptoms, observed in five cultivars, included suppressed growth, progressive size reduction of apical shoots and leaves, chlorosis, foliar reddening, witches'-brooms, and dieback. Phyto-plasma was not detected in cv. Homestead. Possible resistance of this cultivar to elm yellows phytoplasma was indicated by localized phloem necrosis in stems below inoculum patches.
Evidence thatXylella fastidiosaCan Cause Leaf Scorch Disease of Pecan
Authors: Sanderlin R. S. , Heyderich-Alger K. I.
Published: May 2007

The disease known as pecan fungal leaf scorch has been reported to be either caused by or associated with several fungi since it was first recognized in 1972. Data are presented that indicate the disease is initiated by the fastidious xylem-limited bacterium Xylella fastidiosa. X. fastidiosa was found consistently associated with fungal leaf scorch disease of pecan (Carya illinoinensis) in commercial orchards in Louisiana. It was generally not detected in symptomless trees. The disease was reproduced by inoculation of greenhouse seedlings and grafted trees with cultures of the bacterium obtained from leaves with fungal leaf scorch. The bacterium was reisolated from symptomatic tissue of inoculated pecan seedlings, but not from symptomless plants inoculated with water to complete Koch's postulates. It is proposed that the name of the disease be changed to pecan bacterial leaf scorch because fungi do not appear to be necessary for symptom development.
Light, Temperature, and Moisture Effects on Apothecium Production of Sclerotinia sclerotiorum
Authors: Sun P. , Yang X. B.
Published: May 2007

The purpose of this study was to quantify the effects of light, moisture, and temperature on apothecium production of Sclerotinia sclerotiorum. Sclerotia were placed in sand beds in crispers and exposed to two light intensities. For each light intensity, sclerotia were subjected to five temperature levels and three moisture levels. The results showed that the optimal temperature and temperature range for germination of sclerotia were affected by both light intensity and the moisture level of the sand. At light intensity of 80 to 90 mol m-2 s-1 (low light intensity treatment), the optimal temperatures were in the range of 12 to 18°C regardless of moisture level. At light intensity of 120 to 130 mol m-2 s-1 (high light intensity treatment), the optimal temperature was shifted to 20°C when the soil moisture level was high. Under high light intensity, only a few days were needed for initials to develop into apothecia. Under low light intensity, several weeks were needed for initials to develop into apothecia. The frequency with which initials developed into apothecia was high under high light intensity (80%) but low under low light intensity. The initials produced at low light intensity and high temperature (25 to 30°C) were thinner and longer. The apothecia also were smaller at low light intensity than those produced at high light intensity at any temperature. The periods for apothecium production were longer under lower temperature treatments. The relationship between apothecium production and degree days was analyzed. Apothecium production began at about 160 degree days and ceased at about 900 degree days at high light intensity. However, production began at about 760 degree days and ceased at 1,720 degree days at low light intensity. Nonlinear regression equations which describe the relationship between cumulative formation of apothecia and degree days were highly significant. The deviation between the observed value and the predicted value increased as degree days increased.
A Putative Defective Interfering RNA from Bean pod mottle virus
Authors: Sundararaman Vijaya P. , Strömvik Martina V. , Vodkin Lila O.
Published: May 2007

A putative defective interfering (DI) RNA from the Bean pod mottle virus (BPMV) was discovered by screening of random cDNA clones in a soybean cDNA library. This was unexpected because the library was constructed from mRNA of visually healthy soybean pods. The insert in the cDNA clone, VS-16, is not present in the soybean genome but showed strong mRNA expression in pod tissue of soybean and in bean leaf beetles collected in the field. Analysis of the VS-16 sequence reveals that it has significant homology to the 3.66-kb BPMV RNA-2. A 2-kb region has been deleted in VS-16, and other regions of the viral RNA genome have been rearranged to yield a putative defective interfering RNA (DI RNA) of 1.35 kb. The three regions of VS-16 are 95.8, 77.8, and 85.6% identical at the nucleotide level to the corresponding regions of BPMV RNA-2. This is the first report of a DI RNA from the comovirus group of plant viruses. It may be helpful in antivirus efforts for soybean, especially since there are increasing numbers of reports of BPMV in soybeans in the midwestern United States.
Effects of Shredding or Treating Apple Leaf Litter with Urea on Ascospore Dose ofVenturia inaequalisand Disease Buildup
Authors: Sutton Donald K. , MacHardy William E. , Lord William G.
Published: May 2007

Ascospores produced on diseased leaves in the leaf litter constitute the primary inoculum causing scab in commercial apple orchards in the northeastern United States. Two sanitation practices, shredding the leaf litter with a flail mower and urea application, were evaluated for their potential to reduce the risk of primary scab. Three measures of a treatment's potential were made: leaf litter density was evaluated to determine reduction of the source or primary inoculum; trapped ascospores were counted to measure the reduction of primary inoculum; and scab lesions on trees and seedlings were counted to determine reduction in disease incidence and severity on leaves and fruit. The results show that in the northeastern United States, shredding the leaf litter in November or April will reduce the risk of scab by 80 to 90% if all of the leaf litter is shredded. If 10 to 35% of the leaf litter cannot be shredded because of the limited offset of the flail mower and spread of the tree canopy, then the risk of scab is reduced by 50 to 65%. Urea applied to the leaf litter in November (when approximately 95% of the leaves had fallen) reduced the number of ascospores trapped by 50%. Urea applied to the leaf litter in April (before bud break) reduced the number of ascospores trapped by 66%. The reductions are discussed in relation to a sanitation action threshold that links sanitation to a strategy that reduces the fungicide dose to control primary scab in an orchard assessed with a moderate amount of foliar scab the previous autumn.
The Effect of Wounding, Temperature, and Inoculum on the Development of Pink Rot of Potatoes Caused by Phytophthora erythroseptica
Authors: Salas B. , Stack R. W. , Secor G. A. , Gudmestad N. C.
Published: May 2007

The effect of wounding, temperature, and inoculum on the development of pink rot caused by Phytophthora erythroseptica, was studied for its potential impact on postharvest infection. Tissue plugs cut from pink rot infected tubers and plugs of similar size from laboratory cultures of the pathogen were highly effective inoculum sources on wounded tubers. Severe wounding, temperatures of 15 to 25°C, and high inoculum density affected the infection risk. Regardless of source or amount of inoculum, any degree of wounding greatly increased incidence of infection of tubers by P. erythroseptica. Infections in unwounded tubers started at 15°C, whereas in wounded tubers infection started at 10°C. Incidence of pink rot was high when two or three of the factors (severe wounding, high temperature, high inoculum level) were favorable. Incidence of pink rot was intermediate when only one factor was favorable. Incidence of pink rot was low or absent without a favorable factor (no wounding, low temperature, and low inoculum), Since infected tuber tissue may serve as potential inoculum source for postharvest infection of tubers by P. erythroseptica, the removal of pink rot infected tubers at harvest is desirable. Avoidance of wounding and rapid cooling of storage bins to 10°C may also help control pink rot.
Virulence of Puccinia triticina on Wheat in the United States from 1996 to 1998
Authors: Long D. L. , Leonard K. J. , Hughes M. E.
Published: May 2007

Isolates of Puccinia triticina were obtained from wheat leaf collections made by cooperators throughout the United States and from surveys of wheat fields and nurseries in the Great Plains, Ohio Valley, and Gulf Coast states in 1996, 1997, and 1998. Virulence-avirulence phenotypes were determined on 14 host lines that are near-isogenic for leaf rust resistance. We found 31 phenotypes among 277 single uredinial isolates in 1996, 56 phenotypes among 989 isolates in 1997, and 43 phenotypes among 989 isolates in 1998. As in previous surveys, regional race distribution patterns showed that the central United States is a single epidemiological unit distinct from the eastern United States. The distinctive racial composition of collections from the southeast, northeast, and Ohio Valley indicate that populations of P. triticina in those areas are not closely connected, suggesting that epidemics originate from localized overwintering sources.
First Report of a Tospovirus on Sunflower (Helianthus annus L.) from India
Authors: Subbaiah K. Venkata , Sai Gopal D. V. R. , Krishna Reddy M.
Published: May 2007

Virus-like symptoms were observed on sunflower in and around Tirupati during January 1998. Infected plants exhibited severe mosaic, systemic necrosis along the stem and floral heads, leaf distortion, and ringspots on leaves. The causal virus, mechanically transmissible from sunflower to sunflower cvs. Morden, MHSF8, MHSF18, KBHS1, and Cargil, developed symptoms like those in the original plant. The virus caused chlorotic and necrotic spots on Chenopodium amaranticolor, chlorotic and necrotic rings on cowpea cv. C-152, chlorotic spots on Datura metal and Petunia hybrida, chlorotic rings and systemic infection on Gomphrena globosa, tarlike symptoms on Catharanthus roseus, and local brown lesions on Cassia tora (1). Virus was isolated from infected sunflower leaves (2), and particles in negatively stained preparations were enveloped and 80 to 90 nm in diameter. Cytopathic effects included accumulation of virus particles in the endoplasmic reticulum, the formation of viroplasm, and aggregates consisting of nonenveloped viral nucleocapsids in the cytoplasm of ultrathin sections of infected sunflower leaves. Sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis of capsid protein resolved as a single band of 31 kD. The dsRNA isolated from infected sunflower leaves resolved as three bands of 9, 4.9, and 3 kb in 2% agarose gel electrophoresis. In enzyme-linked immunosorbent assay, the purified virus reacted with homologous and Peanut bud necrosis virus (PBNV-ICRISAT, India) antisera and not to polyclonal antibodies to Iris yellow spot virus (Netherlands), Tomato spotted wilt virus-T (Georgia), Impatiens necrotic spot virus, and several isolates of Cucumber mosaic virus (CMV-B, CMV-C, CMV-To). In western blotting analysis, the virus coat protein reacted with homologous and PBNV antisera corresponding to coat protein band of 31 kD. In reverse transcription polymerase chain reaction, the viral RNA was amplified by using primers derived from NP gene sequence of PBNV and Watermelon silver mottle virus (WSMV). Based on these properties, the virus causing sunflower mosaic followed by necrosis in India was identified as a tospovirus, which may be as a distinct isolate of sero group IV.

References: (1) A. A. Brunt et al. Viruses of Plants Online. 1996. Australian National University, Canberra, 1996. (2) D. V. R. Reddy et al. Bud necrosis virus: A disease of peanut caused by Tomato spotted wilt virus. ICRISAT Inf. Bull. No. 31, 1991.
Dicentra, Epimedium, and Heuchera: New Perennial Ornamental Hosts of Tobacco rattle virus in the United States
Authors: Lockhart B. E. L.
Published: May 2007

Yellow ringspotting and concentric line patterns in plants of Dicentra (bleeding heart), Epimedium (barrenwort), and Heuchera (coral bells) from commercial nurseries and home gardens in Minnesota, Michigan, and Massachusetts were associated with infection by Tobacco rattle virus (TRV), which was identified by particle morphology, enzyme-linked immunosorbent assay and immunosorbent electron microscopy. No other viruslike particles were observed by electron microscopy in partially purified preparations of TRV-infected leaf tissue, and TRV was not detected in asymptomatic plants. This is the first report of TRV occurrence in Dicentra in the United States and the first report of TRV occurrence in Epimedium and Heuchera. In previous reports (1,2) we have called attention to the increasing incidence of TRV in vegetatively propagated perennial ornamental plant species in the United States and to the potential for virus spread to crops such as potato, in which TRV has not been reported in the midwestern United States. It is possible that increased international trade in vegetatively propagated ornamental plants may be resulting in the introduction of TRV and other exotic viruses into the United States and elsewhere. It is also possible that the natural occurrence of TRV in North America may be actually more widespread than has been reported.

References: (1) B. E. Lockhart et al. Plant Dis. 79:1249, 1995. (2) B. E. Lockhart and J. A. Westendorp. Plant Dis. 82:712, 1998.
A New Ilarvirus Isolated from Grapevine in Greece
Authors: Girgis S. M. , Bem F. , Kyriakopoulou P. E. , Dovas C. I. , Sklavounos A. P. , Avgelis A. , Katis N. , Tzortzakaki S. , Tsagris M.
Published: May 2007

In 1994, characteristic viruslike symptoms on grapevine were reported in the collection of the Grapevine Institute in Athens, Greece, on the hybrid Baresana × Baresana. The symptoms were sharp angular mosaic, leaf crinkle, and little leaf. The affected vines showed gradual decline and severe stunting or death. Such vines produced abortive flowers or very few berries with smaller, wrinkled, and nongerminating seeds. Serological testing, by enzyme-linked immunosorbent assay (ELISA), of the affected vines against the most common grapevine viruses Alfalfa mosaic, Arabis mosaic, Grapevine fanleaf, Grapevine fleck, Grapevine A, Rasberry ringspot, and grapevine leafroll-associated viruses gave negative results. A virus was isolated from affected grapevine young leaves by mechanical inoculation of Gomphrena globosa and single lesioned. The virus host range included G. globosa (local and systemic dark red or necrotic lesions), Chenopodium quinoa (necrotic local lesions and systemic mottle), and three tobacco cultivars (sharp necrotic local lesions, 1 to 3 mm in diameter). Pollination of C. quinoa with pollen from infected plant gave about 30% infected seedlings. The virus was purified from C. quinoa by differential centrifugation using 0.02 M phosphate buffer pH 8.0, containing 0.01 M DIECA and 0.01 M sodium thioglycolate as extraction buffers. In a purified preparation, quasisphaerical virus particles of about 29 nm were observed. Electrophoretic mobility of the viral coat protein showed a molecular weight of 30 kDa. Using purified preparations, an antiserum was obtained with a titer of 1:1024 in microprecipitin test and an optimum IgG dilution in ELISA of 1:10,000 for maximum absorption at OD405 nm Using degenerate primers designed from homologous regions in RNA-2 corresponding to a fragment of the polymerase gene of Ilarviruses, the expected 381-bp polymerase chain reaction product was obtained. This product was cloned and sequenced. Comparisons with sequence data from the homologous regions of RNA-2 of other known Ilarviruses, showed that the sequence of the above 381-bp amplicon shared 72% sequence similarity with Tobacco streak virus, 67% of Citrus variegation virus and Spinach latent virus, 66% of Asparagus virus 2 and Elm mottle virus, and 65% of Citrus leaf rugose virus. Based on the above data, it is concluded that the isolated virus is an Ilarvirus with closest similarity to Tobacco streak virus. From the relative bibliography (1–3) it appears that the virus reported here is different from Grapevine line pattern virus, a possible Ilarvirus, previously reported from Hungary.

References: (1) J. Lehoczky et al. Kertgazdasag 19:61, 1987. (2) J. Lehoczky et al. Phytoparasitica 17:59, 1989. (3) J. Lehoczky et al. Phytopathol. Medit. 31:115, 1992.
Detection and Partial Characterization of Tenuiviruses from Black Spruce
Authors: Castello J. D. , Rogers S. O. , Bachand G. D. , Fillhart R. C. , Murray J. S. , Weidemann K. , Bachand M. , Almond M. A.
Published: May 2007

Filamentous viral ribonucleoproteins (RNPs) 12 to 16 nm in diameter and 100 to 1,260 nm in length, and characteristic of the genus Tenuivirus, were detected by transmission electron microscopy in purified extracts of needles collected from two mature, asymptomatic black spruce (Picea mariana) trees in New York, but not in extracts of needles from nursery seedlings. Purified RNPs from one tree had a buoyant density in CsCl = 1.39 g/cm3 and an A 260/280 = 1.436. Four ssRNA segments of 1.3, 2.1, 2.3, and 3.5 kb, but not the 8- to 9-kb fragment characteristic of most tenuiviruses, were detected in purified RNA extracts. Amplification products of the expected size were observed when RNA extracts from the two spruce trees and Maize stripe tenuivirus (MStpV), but not from tobacco, Chenopodium quinoa, or spruce seedlings were subjected to reverse transcription-polymerase chain reaction (RT-PCR) using primers to the p3 open reading frame (ORF) of MStpV vRNA 3. However, only MStpV amplified when primers to the nucleocapsid ORF (pc3 ORF on vcRNA 3) were used. Similarly, only MStpV amplified by immunocapture polymerase chain reaction (PCR) using antiserum to MStpV and primers to the p3 ORF. Sequence comparisons suggest that two distinct tenuiviruses occur in black spruce, one more closely related to MStpV than the other. One of these tenuiviruses was detected in one of 10 additional black spruce trees tested, but not in trees of six other coniferous species sampled in the Adirondack Mountains of New York.
Cytology of Fibrous Roots from Citrus Blight-Affected Trees
Authors: Lindbeck A. G. C. , Brlansky R. H.
Published: May 2007

Citrus blight is an economically important decline disease of citrus in various areas of the world. The cause of citrus blight is unknown, but transmission via root grafting has been demonstrated. Root tissue from fibrous roots of citrus blight-affected and healthy citrus trees were compared. Amorphous plugs of the type previously observed in the trunk xylem and large roots of blighted trees were also found in the fibrous roots. The plugs were yellow to light gold in color, gave a positive staining reaction for the presence of lignin, and were retained when kept overnight in water. With scanning electron microscopy the amorphous plugs appeared to be solid, occluding part or all of the vessel. These plugs have previously been implicated in the reduction of water transmission in blighted trees.
First Report of Oleander Leaf Scorch Caused by Xylella fastidiosa in Florida
Authors: Wichman R. L. , Hopkins D. L. , Wichman T. A.
Published: May 2007

During the spring of 1998, mature oleanders (Nerium oleander L.), pruned to form a 2-m-high hedge along an interstate highway in Orlando, FL, were observed declining and dying. Numerous plants along a 200-m section of highway were in various stages of decline. Symptoms began as chlorotic mottling along the edges of leaves and as the disease progressed, mottling became more severe and leaf margins became necrotic. Scorched leaves died, and symptoms spread throughout the plants, resulting in defoliation. New growth from the base of affected plants was stunted and severely mottled. Petioles and leaf midribs were taken from leaves with mottling symptoms and assayed for the presence of Xylella fastidiosa by polymerase chain reaction (PCR) and culturing on periwinkle wilt agar medium. For PCR assay, infected tissue from three plants was extracted by grinding in SCP buffer (1.0 g of trisodium citrate and 1.0 g of disodium succinate per liter, in 0.015 M phosphate buffer, pH 7.0) containing 0.02 M sodium ascorbate and 5% acid-washed polyvinylpyrrolidone. Amplification was performed with primers RST31 and RST33, as previously described, for specific detection of X. fastidiosa strains (1). A X. fastidiosa-specific amplification product was produced from all three extracts. For culturing, petioles and leaf midribs were cut into 0.5-cm sections, and sap was extracted from the tissue by squeezing with a forceps. Sap was blotted directly onto the medium and incubated at 28°C. Colonies typical of X. fastidiosa were observed after 10 to 14 days of incubation, and single colonies were transferred to fresh periwinkle wilt agar. The colonies were confirmed as X. fastidiosa by PCR assay. Two of the oleander strains were used to inoculate three red and three white 18-month-old oleanders by needle-puncture of the stem through a cloudy drop of bacterium in SCP buffer (108 CFU/ml). For controls, three red and three white oleanders were inoculated with SCP buffer alone. After 9 weeks in a screenhouse, marginal leaf mottling was observed in both the red and white oleanders inoculated with X. fastidiosa, and the bacterium was reisolated from leaves as described above, completing Koch's postulates. Control plants remained symptomless. Oleander leaf scorch caused by X. fastidiosa has been described previously in California and Texas (2). This is the first report of oleander leaf scorch in Florida and the eastern United States.

References: (1) G. V. Minsavage et al. Phytopathology 84:456, 1994. (2) A. H. Purcell et al. Phytopathology 89:53, 1999.
First Report of Phomopsis Fruit Rot of Strawberry in Ohio
Authors: Ellis M. A. , Nita M. , Madden L. V.
Published: May 2007

During spring (May and June) 1999, ≈30% of the fruit in a 0.5-ha commercial planting of strawberry (Fragaria × ananassa ‘Allstar’) was lost to an unknown fruit rot. The planting was established on black plastic (plasticulture) during summer 1998. Plasticulture is a relatively new system of perennial strawberry production in Ohio that is rapidly gaining popularity among growers (2). It was observed that the plastic beneath the plants in the plasticulture planting was covered with a layer of dead leaves from the previous season's growth, and virtually all rotted fruits were in contact with dead leaves. Fruit rot was rarely observed on fruits that were not in direct contact with dead leaves, and fruits of the same cultivar grown in the traditional matted-row system in an adjacent field did not show rot symptoms. It was postulated that infested dead leaf material could serve as an inoculum source for infection. Fruit rot symptoms were identical to those described for Phomopsis soft rot (1). Isolations were made from infected berries. Berries were soaked in 70% ethanol for 60 s, and tissue sections were placed on potato dextrose agar and incubated at room temperature (≈20 to 22°C). A fungus was isolated consistently from infected tissue. The fungus produced pycnidia in culture, and the fruiting structure and conidia conformed to the description of Phomopsis obscurans (Ellis & Everh.) Sutton (synamorph Dendrophoma obscurans (Ellis & Everh.) H.W. Anderson). Pathogenicity studies were conducted by placing one drop (20 μl) of a conidial suspension (9 × 106 conidia per ml) obtained from 2-week-old cultures on each of five ripe (red) and five immature (pink) detached strawberry fruits. Inoculated fruits were placed on screens in plastic moisture chambers. Five uninoculated fruits served as controls. Within 3 days, whitish lesions appeared on all inoculated fruit; within 8 days, the symptoms observed in the field were reproduced, and lesions were covered by pycnidia. No fruit rot developed on control fruit. The fungus was reisolated from infected fruit to complete Koch's postulates. Although the incidence of Phomopsis leaf blight is increasing in many Ohio strawberry plantings and is becoming a concern to growers, this is the first observation and report of Phomopsis fruit rot in Ohio. Unlike leaf blight, for which it is difficult to directly relate economic loss to disease incidence or severity, losses due to fruit rot can be high, as in this field. As the number of strawberry plantings under plasticulture continues to increase, the importance of Phomopsis leaf blight and fruit rot also may increase.

References: (1) J. L. Maas, ed. 1998. Compendium of Strawberry Diseases, 2nd ed. The American Phytopathological Society, St. Paul, MN. (2) E. B. Poling. HortTechnology 3:384, 1993.
First Report of Leaf Blight Caused by Pseudomonas syringae on Cornus mas
Authors: Mmbaga M. T. , Sheng H.
Published: May 2007

Cornellian cherry (Cornus mas) is an enduring dogwood that is primarily grown as an ornamental plant in North America, but in parts of Europe, its fruit is eaten fresh or pickled or made into soft drinks, wine, and liqueur. Cornellian cherry has demonstrated longevity and adaptability and has had no previous disease or pest problems. In Tennessee, a leaf blight was first observed during spring 1996 in nursery plants imported from Europe. The disease quickly spread to other C. mas plants within the nursery and has caused severe damage for three consecutive years. The disease affected mostly leaves and young shoots, causing dark brown necrotic lesions and some die back. In early stages, leaf infection consisted of discrete lesions, angular in shape and surrounded by a chlorotic halo. These lesions eventually coalesced to form large dark necrotic patches that covered a large portion of the leaf or the entire leaf. Disease symptoms were restricted to early spring during wet and cool weather; later in the season new growth was free of symptoms. A bacterium was isolated from infected plants and tested for pathogenicity on C. mas ‘Redstone’ and C. florida. Symptoms were reproduced on C. mas but not on C. florida. The bacterium was reisolated from inoculated plants, was characterized as gram-negative and rod-shaped, and produced fluorescent pigment on King's medium B agar. The bacterium had a positive reaction to the Levan test and negative reactions to potato rot and arginine dihydrolase tests and was identified as Pseudomonas syringae (1). Samples of the bacterium were sent to Texas A&M University, College Station, for fatty acid analysis, and the results confirmed the identity of P. syringae. P. syringae has caused severe damage in C. florida in the northwestern United States (2); however, this is the first report of P. syringae on C. mas.

References: (1) N. W. Schaad, ed. 1988. Laboratory Guide for Identification of Plant Pathogenic Bacteria. The American Phytopathological Society, St. Paul, MN. (2) W. A. Sinclair et. al. 1987. Diseases of Trees and Shrubs. Cornell University Press, Ithaca, NY.
New Hosts of Corynespora cassiicola in Sri Lanka
Authors: Silva W. P. K. , Wijesundera R. L. C. , Karunanayake E. H. , Jayasinghe C. K. , Priyanka U. M. S.
Published: May 2007

Corynespora cassiicola is the causal organism of the most devastating leaf disease of rubber in Sri Lanka. Cotton, cowpea, cucumber, eggplant, sesame, soybean, tobacco, and tomato also have been reported as hosts of C. cassiicola. In Sri Lanka, however, the fungus has been reported only on rubber, soybean, winged bean, and tomato (1). During this investigation, C. cassiicola was isolated from cocoa, tomato, papaya, winged bean, sweet potato, and manihot. The pathogenicity of each isolate on the host from which it was isolated was established by following Koch's postulates. This is the first record of Corynespora leaf disease on cocoa, papaya, sweet potato, and manihot in Sri Lanka. Using an aqueous spore suspension (5 × 104 spores per ml), rubber leaves were inoculated separately with each isolate. Inoculation studies indicated that, except for the isolate from papaya, all isolates also were pathogenic on rubber. In Sri Lanka all the host plants listed are commonly cultivated in and around rubber plantations. Therefore, the existence of C. cassiicola infections on other hosts should be taken into account when developing control measures for Corynespora infection on rubber.

Reference: (1) P. Shivanathan and R. S. Y. de Silva. 1989. Plant pests of Sri Lanka. Rep. Plant Quarantine Div. 1989. Plant Quarantine Division, Peradeniya. Sri Lanka.
Evaluation of Graft-Transmissible Isolates from Dwarfed Citrus Trees as Dwarfing Agents
Authors: van Vuuren S. P. , da Graça J. V.
Published: May 2007

The dwarfing characteristics of four isolates (CD 4, CD 8, CD 9, and CD 10), derived from healthy-looking dwarfed field citrus trees, were evaluated. Each was bud inoculated to cv. Delta Valencia trees on cv. Yuma citrange rootstock prior to planting in the field. At 5 years after planting, isolates CD 4 and CD 9 reduced canopy volumes by 60%, and CD 10 by 30%, without any detrimental effects. No citrus viroids (CVds) were detected biologically or by sequential polyacrylamide gel electrophoresis in these three isolates. Isolate CD 8, however, contained two viroids, citrus exocortis viroid and a Group-III CVd, but had no deleterious effects on the Yuma citrange rootstock. Citrus tristeza virus (CTV) was the only other pathogen detected in all of the isolates. Indexing for cachexia, psorosis, impietratura, and tatter leaf were negative. The dwarfing abilities of the isolates are therefore attributed to CTV. Fruit yield was according to tree size and the yield efficiency of the inoculated trees was equal to that of the uninoculated control trees. External and internal fruit quality was not affected. The trees became naturally infected with huanglongbing (greening) 5 years after planting, but the disease incidence remained low for several years in trees with isolate CD 4.
Variation in Aggressiveness of Ash Yellows Phytoplasmas
Authors: Sinclair W. A. , Griffiths H. M.
Published: May 2007

Twelve strains of phytoplasmas belonging to the ash yellows (AshY) group, from across the known range of AshY and representing six host species, were assessed for differences in ability to suppress growth and cause chlorosis in graft-inoculated Fraxinus pennsylvanica (green ash) and Catharanthus roseus (periwinkle). In each of two experiments with ash and one with periwinkle, different strains caused significantly different degrees of growth suppression and loss of foliar greenness. These growth and color impacts were positively and significantly correlated among experiments and between ash and periwinkle, indicating strain variation in aggressiveness. After two strains that differed in aggressiveness were coinoculated to periwinkle plants, polymerase chain reaction/restriction fragment length polymorphism (PCR/RFLP) assays of DNA from leaves remote from the inoculation sites revealed the presence of the aggressive strain sooner and more frequently than that of the less aggressive strain. Thus, aggressiveness was associated with more rapid multiplication and/or movement than was achieved by the less aggressive strain. When either strain was inoculated 11 weeks before the other into the same plant, only the initial strain could be detected after a further 12 weeks of incubation. Thus, the initial strain or its effect on the host may have interfered with multiplication and/or long-distance movement of the second strain. A concept of preemptive dominance is proposed to account for detection by primary PCR of only single phytoplasma strains in plants that may harbor two or more strains.