bluuebunny/crossref_metadata_2025 huggingface dataset:
Stem Smut (Ustilago hypodytes) on Intermediate Wheatgrass in Canada
Authors: Chang K. F. , Howard R. J. , Gossen B. D. , Hwang S. F.
Published: May 2007

Intermediate wheatgrass (Thinopyrum intermedium [Host] Barkworth & D.R. Dewey) (syn. Agropyron intermedium [Host] Beauv.) is becoming an important forage grass species in Alberta, Canada. Severe losses in seed yield due to stem smut (Ustilago hypodytes [Schlecht.] Fr.) were noted in a 70-acre field near Warner, AB, in 1999. The crop had been established in 1993 and harvested for seed each year. Smut symptoms (5% incidence) were noted initially in 1997. Incidence, determined by counting the number of symptomatic stems, increased to 10% in 1998 and 50% in 1999. The symptoms usually appeared in the first week of June. Brown sori developed on infected stems, especially between the uppermost node and the leaf below the flag leaf, and gradually became black during the period of seed filling, which is characteristic of stem smut (1). Teliospores were smooth, spherical to oval, light to dark brown, and 4.5 to 5.0 × 5.0 to 6.8 μm in dimension, which is also consistent with previous descriptions of U. hypodytes. Infected stems occasionally flowered, but did not set seed, so seed yield losses were proportional to disease incidence. Plants infected with stem smut were often stunted. Tissues in the smutty stem often became sunken and stems became twisted and thinner than normal due to the propagation of sori in the stem over time. Stem smut has been reported on crested wheatgrass and slender wheatgrass in other parts of Canada (2) and on T. intermedium in the United States (3). This is the first report of stem smut affecting commercial grass seed production in Alberta, Canada. This disease could also have a significant impact on the seed production of intermediate wheatgrass elsewhere.

References: (1) G. W. Fischer. 1953. Manual of the North American Smut Fungi. Ronald Press, New York. (2) B. D. Gossen and D. Regnier. Can. Plant Dis. Surv. 71:88–89, 1991. (3) J. F. Karn and J. M. Krupinsky. Phytopathology 73:1152–1155, 1983.
First Report of Plum Pox Potyvirus in Ontario, Canada
Authors: Thompson D. , McCann M. , MacLeod M. , Lye D. , Green M. , James D.
Published: May 2007

Plum pox potyvirus (PPV) causes plum pox (sharka) disease, which is considered the most serious disease of stone fruits including peach, plum, nectarine, and apricot (2). The disease may cause losses as high as 80 to 100% of some crops (2). A survey was initiated in the Niagara region of Ontario, Canada, after it was reported that PPV was detected in Pennsylvania (1). The initial survey focused on Prunus material imported into Canada from the Pennsylvania region. Where imported trees could be identified, every tree was sampled. In cases where the imported trees were growing in mixed blocks with plants from other sources, 25% of the trees were sampled and tested as composites of four trees. PPV was detected in three symptomless Fantasia nectarine (Prunus persica var. nectarina) trees by triple-antibody sandwich (TAS) ELISA using the REAL Durviz kit (Valencia, Spain), which contains the universal PPV monoclonal 5B. PPV infection was confirmed by western blot analyses (a PPV polyclonal antibody and PPV 5B monoclonal were used as primary antibodies), reverse transcription polymerase chain reaction (RT-PCR), and TC/RT-PCR. In western blot analyses, the coat protein subunit sizes of the Canadian PPV isolates were estimated at 32 kDa based on electrophoretic mobility in 12% SDS-PAGE. RFLP analysis of the 243-bp fragment amplified using PPV specific primers P1 and P2 (4) indicated the presence of RsaI and AluI enzyme restriction sites, which is characteristic of PPV D strains. In RT-PCR analysis using D and M specific primers (3), only the D specific primers amplified a fragment 198 bp in size. This data provided conclusive evidence that the PPV isolates detected in Canada were PPV D, similar to the strain detected in Pennsylvania. The survey is continuing and is being expanded to determine the extent of spread and the exact distribution of the virus.

References: (1) L. Levy et al. Phytopathology (Abstr.) 90:46, 2000. (2) M. Nemeth. Virus, Mycoplasma, and Rickettsia Diseases of Fruit Trees. Akademiai Kiado, Budapest. (3) A. Olmos et al. J. Virol. Methods 68:127–137, 1997. (4) T. Wetzel et al. J. Virol. Methods 33:355–365, 1991.
Genetic Variation Among Fusarium oxysporum Isolates Associated with Root Rot of Amaranthus hybridus in South Africa
Authors: Chen Wei-Qun , Swart W. J.
Published: May 2007

Thirty isolates of Fusarium oxysporum were recovered from six substrates: (i) tap roots of Amaranthus hybridus showing symptoms of root rot, (ii) side roots of A. hybridus showing symptoms of root rot, (iii) soil surrounding plants of A. hybridus, (iv) pigweed weevils (Hypolixus haerens) that feed on A. hybridus, (v) rhizosphere of maize plants growing adjacent to a field of amaranth, and (vi) rhizosphere of dry bean plants growing adjacent to a field of amaranth. The isolates were characterized by means of pathogenicity tests, isozyme analysis, and vegetative compatibility group (VCG) tests. In the pathogenicity tests, toothpick tips were infested with F. oxysporum and inserted into amaranth stems. All 30 isolates were pathogenic on A. hybridus, with significant differences in pathogenicity based on lesion length measured 4 weeks after inoculation. The isolates were grouped into nine VCGs by complementation tests using nitrate nonutilizing mutants. Self-incompatibility was not observed for any of the isolates. The most common VCG was VCG1, which comprised 20 of the 30 isolates tested. The second most common group was VCG3, which included three isolates, while the remaining seven VCGs each consisted of a single isolate. The results indicate that the population of the amaranth root rot pathogen examined in this study is relatively homogeneous. Results of the isozyme analysis supported the results of VCG tests. Three major groups were delineated within the 30 isolates of F. oxysporum following cluster analysis of electrophoretic phenotypic values for seven isozymes (EST, IDH, G6PDH, ACP, PEP1, PEP2, and PEP3) tested. No relationship was found between isozyme phenotype and the substrate from which the isolates were recovered.
Response of Ancestral Soybean Lines and Commercial Cultivars to Rhizoctonia Root and Hypocotyl Rot
Authors: Bradley C. A. , Hartman G. L. , Nelson R. L. , Mueller D. S. , Pederson W. L.
Published: May 2007

Rhizoctonia root and hypocotyl rot is a common disease of soybean caused by Rhizoctonia solani. There are no commercial cultivars marketed as resistant to Rhizoctonia root and hypocotyl rot, and only a few sources of partial resistance to this disease have been reported. Ninety ancestral soybean lines, maturity groups (MGs) 000 to X, and 700 commercial cultivars, MGs II to IV, were evaluated for resistance to R. solani under greenhouse conditions. Most of the ancestral lines and cultivars evaluated were susceptible; however, 21 of the ancestral lines and 20 of the commercial cultivars were partially resistant. Of the 21 ancestral lines, CNS, Mandarin (Ottawa), and Jackson are in the pedigree of cultivars previously reported as being partially resistant to R. solani. In an additional study, dry root weights of 21 soybean cultivars were evaluated after inoculation with R. solani. Variation in dry root weight occurred among cultivars, but there was not a significant (P = 0.05) correlation between dry root weight and disease severity.
First Record of Xiphinema pacificum from a Peach Orchard in Georgia
Authors: Nyczepir A. P. , Lamberti F.
Published: May 2007

In April 2000, a Xiphinema sp. was found in a peach (Prunus persica (L.) Batsch) orchard during a longidorid nematode survey in Concord, GA. The nematode was recovered from the rhizosphere of healthy and dying peach trees established on Lovell rootstock. Following a comparative microscope study, the species was identified as X. pacificum Ebsary, Vrain, & Graham, a putative species of the X. americanum group (2). All morphometric measurements coincided with the original description (1). In North America, this group of nematodes are natural vectors of four economically important nepoviruses that are responsible for causing substantial damage to a wide variety of crops. In spring 1999, tree death from bacterial canker (Pseudomonas syringae pv. syringae) occurred within this then 2-year-old orchard. Samples showed that populations of X. pacificum and Pratylenchus sp. were greater under dying trees (34 and 143/100 cm3 of soil) than under healthy trees (19 and 30/100 cm3 of soil), respectively. Samples taken during the 2000 survey contained 10 X. pacificum per 100 cm3 soil under apparently healthy trees. This nematode was originally described from British Columbia, Canada, where it seemed to be restricted in its distribution to vineyards in the south Okanagan Valley. To our knowledge, this is the first report of X. pacificum in the United States.

References: (1) B. A. Ebsary et al. Can. J. Zool. 67:801, 1989. (2) F. Lamberti et al. Russian J. Nematol. 8:65, 2000.
First Report of Phoradendron macrophyllum on Populus tremuloides
Authors: Gilbertson R. , Mathiasen R.
Published: May 2007

Phoradendron macrophyllum (Engelm.) Cockerell (Viscaceae) is a common mistletoe found on at least 60 hardwood tree species, including several species of cottonwood (Populus spp.) (1), and is distributed from northern Mexico through Arizona and New Mexico into central California (1). R. Gilbertson recently received a specimen of what appeared to be P. macrophyllum parasitizing a planted aspen (Populus tremuloides Michx.) on the Wear Ranch near Fort Grant, Graham County, AZ (T. 11 S., R. 21 E., Section 11). A large swelling on a branch bearing a few small mistletoe plants measuring less than 5 cm high indicated the infection. Comparison of the mistletoe leaf trichomes with those of P. macrophyllum (trichomes with two branches from a common base) and P. coryae Trel. (trichomes stellate with secondary and tertiary branching) indicated that the specimen was definitely P. macrophyllum (2). To our knowledge, this is the first report of P. macrophyllum, or any other mistletoe, on aspen.

References: (1) R. Scharpf and F. Hawksworth. USDA For. Serv. Pest Leafl. 147, 1974. (2) D. Wiens. Brittonia 16:11, 1964.
First Report of Daylily Rust in the United States
Authors: Williams-Woodward J. L. , Hennen J. F. , Parda K. W. , Fowler J. M.
Published: May 2007

In August 2000, rust symptoms were observed on the leaves of daylily plants (Hemerocallis sp. cv. Pardon Me) at a nursery in Dearing, GA. Based on urediniospore characters, the pathogen was tentatively identified as Puccinia hemerocallidis Thuem. Urediniospores were globose to ellipsoid and measured 19 to 30 × 17 to 22 μm (average size of 22 × 19 μm), corresponding to the previously reported description from Japan (1). Teliospores were absent from the sample but were found on daylily plants (cv. Star Struck) with symptoms similar to cv. Pardon Me from the same nursery in Dearing beginning in October 2000. However, the teliospores differed from those in the published description in that many one-celled teliospores (i.e., mesospores), measuring 32 to 43 × 14 to 19 μm (average size of 38 × 16 μm), were produced in addition to two-celled teliospores, which measured 41 to 53 × 16 to 21 μm (average size of 46 × 18 μm). Similar mesospores were present in a slide from an isotype specimen of P. hemerocallidis (US 72719) housed in the U.S. National Fungus Collection (Beltsville, MD). Daylily plants (cv. Pardon Me) were reinoculated with urediniospores by shaking infected plants over uninfected plants and exposing plants to 100% relative humidity for 24 h. Initial symptoms of small, discrete, yellow spots and streaks on the upper surfaces of leaves developed within 3 to 7 days, and uredia with urediniospores were evident at 7 to 14 days after inoculation. Daylily rust is native to Asia and may have been introduced into Georgia on plant materials sent from Central America. The original source of daylily rust is unclear because Central American producers also purchase and import plants from the United States for propagation and then sell divisions back to U.S. growers. Daylily rust is a disease of major concern for both daylily producers and gardeners.

References: (1) N. Hiratsuka, et al. The Rust Flora of Japan. Tsukuba Shuppankai, Ibaraki, Japan, 1992.
First Report of Shoot Blight of Grapevine Caused by Sclerotinia sclerotiorum in Chile
Authors: Latorre B. A. , Guerrero M. J.
Published: May 2007

Grapevine (Vitis vinifera L.), cv. Red Globe, in Northern Chile was found with symptoms of shoot blight early in the spring. Symptoms consisted of elongated cankered lesions surrounded by water-soaked tissues that developed mainly at the base of new shoots. The distal part of the shoots withered. Symptoms were similar to the shoot blight caused by Botrytis cinerea Pers. early in the spring, except that superficial gray sporulation was always absent. Isolation on acidified potato dextrose agar (APDA) consistently yielded a fungus that produced white mycelium and black spherical to elongated sclerotia (2 to 10 mm in diameter); the fungus was identified as Sclerotinia sclerotiorum (Lib.) de Bary (2). New shoots were inoculated by inserting a 4-mm plug of mycelium from actively growing cultures on APDA into a cut made at the base of each of five shoots per cultivar with a sterile scalpel. Inoculated wounds were sealed with Parafilm tape to avoid rapid dehydration. Inoculated plants and an equal number of wounded but not inoculated plants of each cultivar were left as controls and maintained in a screenhouse. Inoculations of grapevine cvs. Thompson Seedless, Flame Seedless, Red Globe, Ribier, and Chardonnay with S. sclerotiorum isolates SC-1, SC-2, and SC-3 and B. cinerea (isolate BC1-3 from grapevine) resulted after 7 days of incubation in canker lesions that were similar to those observed in the field. Cankers caused by S. sclerotiorum varied significantly (P < 0.05) in length from 13.3 to 28.7 mm on ‘Red Globe’, 5.3 to 20.7 mm on ‘Thompson Seedless’, 4.0 to 17.7 mm on ‘Flame Seedless’, 2.0 to 11.3 mm on ‘Ribier’, and 0.0 to 7.6 mm on ‘Chardonnay’. Mature berries of ‘Flame Seedless’ table grapes were surface-disinfected with 1% NaOCl for 1 min, punctured with a sterile needle, and inoculated with a mycelium plug. All S. sclerotiorum isolates and the B. cinerea isolate were pathogenic on mature berries, which developed a soft rot and superficial mycelium after 5 days of incubation at 25°C in humid chambers. Reisolations from diseased shoots and rotten berries were successfully performed on APDA. We concluded that S. sclerotiorum and B. cinerea could cause canker lesions on new shoots early in the spring. S. sclerotiorum has been previously associated with soft rotting of mature berries of grapes worldwide (1), but to our knowledge, this is the first confirmed report demonstrating that S. sclerotiorum can cause shoot blight. Considering that grapevines are cultivated on 2-m-high trellises in Chile, we speculate that wind disseminated ascospores may infect shoots. However, ascocarps have not yet been found in vineyards in Chile.

References: (1) W. B. Hewitt. Berry rots and raisin molds. Pages 26–28 in: Compendium of Grape Diseases. R. C. Pearson and A. C. Goheen, eds. The American Phytopathological Society, St. Paul, MN, 1994. (2) L. Kohn. Phytopathology 69:881, 1979.
Resistance to Bacterial Canker in Tomato (Lycopersicon hirsutumLA407) and its Progeny Derived from Crosses toL. esculentum
Authors: Francis David M. , Kabelka Eileen , Bell Julia , Franchino Barb , St. Clair Dina
Published: May 2007

Bacterial canker caused by Clavibacter michiganensis subsp. michiganensis causes significant yield losses on tomatoes grown in a humid environment. This study was conducted to identify a source of resistance that could be easily crossed to cultivated tomato and to study the inheritance of resistance. Diverse bacterial strains representative of the major DNA fingerprint classes endemic to North America were used to screen germ plasm and populations derived from wide crosses. Partial resistance to genetically characterized and distinct strains of C. michiganensis subsp. michiganensis was identified in a wild relative of cultivated tomato, Lycopersicon hirsutum Lycopersicon accession (LA)407. The level of resistance in LA407 was not significantly different from that of the resistant L. peruvianum control, LA2157. Resistance from LA407 was recovered in lines from a BC2S4 inbred backcross (IBC) population in both greenhouse and field trials. Linear correlations between field and greenhouse resistance scores were significant, though correlation coefficients tended to be low. Variance components for genetic and environmental variation in resistance were used to estimate broad-sense heritability in the IBC population. These estimates were moderate to high, ranging from 0.34 to 0.85. The number of genes contributing to resistance was estimated from four trials, with most estimates falling in the range of one to three loci. Two lines from the IBC population, IBL 2353 and IBL 2361, were identified as sources that retain resistance in a genetic background that has a theoretical L. esculentum genome content of 87.5%.
Effects of Spore Availability, Spore Germinability, and Shoot Susceptibility on Gall Rust Infection of Pine
Authors: Moltzan B. D. , Blenis P. V. , Hiratsuka Y.
Published: May 2007

Temporal changes in three factors (shoot susceptibility, spore availability, and spore germinability) were evaluated to estimate their effects on the infection of lodgepole pine (Pinus contorta var. latifolia) by Endocronartium harknessii. Germinability of rust spores from sori free of hyperparasites remained above 80% during the growing season and thus would not have significantly limited infection. In contrast, there was a slight, but statistically insignificant, increase in estimated susceptibility as infection increased from 94% of maximum at 45% shoot elongation to maximum susceptibility at 90% shoot elongation. This was followed by a precipitous decline in estimated susceptibility to 57% of maximum when shoots were 95% elongated. Spore availability was 24% of maximum when shoots were 45% elongated, and thus may have been limiting at the beginning of the growing season. At the end of the growing season, spore availability declined prior to, or simultaneous with, the decline in susceptibility. The combined effect of both factors drastically reduced the number of infections estimated to occur once shoots are more than 95% elongated. As shoots elongated, relatively more infections formed higher on the shoot, supporting the hypothesis that periderm is important in limiting infection.
A New Bacterial Leaf Spot Disease of Broccolini, Caused by Pseudomonas syringae pathovar maculicola, in California
Authors: Cintas N. A. , Bull C. T. , Koike S. T. , Bouzar H.
Published: May 2007

In 1998, a new disease was detected on 3-week-old commercial broccolini (Brassica oleracea L. var. botrytis × B. alboglabra) transplants in a Salinas Valley, Monterey County, CA greenhouse. Initial symptoms were small (2 to 4 mm diameter) circular to angular, water-soaked spots. As the disease progressed, spots remained relatively small, but turned tan to brown. When diseased tissues were macerated and streaked on King's medium B, a blue-green fluorescent pseudomonad was consistently isolated. Strains were levan positive, oxidase negative, and arginine dihydrolase negative. Strains did not rot potato slices, but induced a hypersensitive reaction on tobacco (Nicotiana tabacum L. ‘Turk’). Fatty acid methyl ester analysis (MIS-TSBA, version 4.10, MIDI Inc., Newark, DE) indicated that strains had a high similarity index (0.82 or higher) to Pseudomonas syringae, and GN (version 3.50, Biolog, Inc., Hayward, CA) profiles also identified strains as P. syringae. The bacterium associated with the disease, therefore, was identified as P. syringae van Hall. Pathogenicity was demonstrated by growing inoculum in nutrient broth shake cultures for 48 h, misting the broth cultures (1×106 CFU/ml) onto broccolini (cv. Aspabrock), and subjecting the plants to 48 h of high humidity. Control plants were misted with sterile nutrient broth. After 4 to 5 days in a greenhouse, leaf spot symptoms developed on all inoculated broccolini plants, and reisolated strains were characterized and found to be P. syringae. Control plants remained symptomless. The results of two sets of pathogenicity tests were the same. Repetitive sequence-based polymerase chain reaction using the BOXA1R primer resulted in identical banding patterns for the broccolini pathogen and for known isolates of P. syringae pv. maculicola from crucifers. In host range testing, P. syringae pv. maculicolawas pathogenic to broccolini plants. The broccolini isolates and P. syringae pv. maculicola isolates had the same pathogenicity results when crucifers and tomatoes were tested as hosts; broccoli and cauliflower (B. oleracea var. botrytis) were infected, and tomato results were variable. These tests suggest that the broccolini pathogen is the bacterial leaf spot pathogen, Pseudomonas syringae pv. maculicola, that occurs on broccoli and cauliflower transplants (1). To our knowledge, this is the first report of this pathogen causing a disease on commercially grown broccolini.

Reference: (1) S. T. Koike et al. Plant Dis. 82:727, 1998.
First Report of Fusarium crookwellense Causing Tip Blight on Cones of Hop
Authors: Pethybridge S. J. , Hay F. S. , Wilson C. R. , Sherriff L. J. , Leggett G. W.
Published: May 2007

Hop (Humulus lupulus L.) is grown primarily for the alpha and beta acids produced in the strobile (cone) and used for bittering beer. In late summer (March) 2001, necrotic lesions covering the tips of cones of cvs. Agate, Nugget, and Willamette at hop farms in Tasmania, Australia, were observed. The necrotic lesions encompassed the proximal tips and affected between 5 and 60% of the cone; however, all bracts in the whorl were always affected. Diseased cones were observed in all seven gardens included in the survey. The incidence of plants with cone tip blight in ‘Nugget’ ranged from 5 to 30% in three gardens, in ‘Agate’ ranged from 3 to 10% in three gardens, and in the only ‘Willamette’ garden 30% of cones were affected. Pieces of infected hop cones (N = 55) were surface-treated for 1 min in 2% sodium hypochlorite, placed on 2% water agar, and incubated at 22 ± 2°C. Fusarium crookwellense Burgess, Nelson, & Toussoun was isolated from 95% of the cones (1). F. crookwellense was identified on carnation leaf agar by L. Burgess, University of Sydney, Australia. Koch's postulates were fulfilled by inoculating detached mature hop cones of cvs. Nugget and Willamette (N = 20 for each cultivar) with an atomized conidial suspension (3.5 × 105 spores of a single F. crookwellense isolate per milliliter) until runoff and incubated at 20 ± 2°C in a sealed container on plastic mesh over tissue wetted with sterile distilled water. Symptoms first appeared 5 days after inoculation and were identical to those found in the field. No disease symptoms were observed on cones subjected only to sterile distilled water. The pathogen was reisolated from diseased tissue on inoculated cones, completing Koch's postulates. Similar disease symptoms on hop cones have been described in Oregon and were associated with infection by F. sambucinum and F. avenaceum (C. Ocamb, personal communication). To our knowledge, this is the first report of the infection of hop cones by F. crookwellense.

Reference: (1) L. W. Burgess et al. Laboratory Manual for Fusarium Research, 3rd ed. University of Sydney, Australia, 1994.
Occurrence of Bacterial Leaf Spot of Escarole Caused by Pseudomonas cichorii in the Everglades Agricultural Area of Southern Florida
Authors: Pernezny K. , Raid R. N.
Published: May 2007

In the fall of 1997, 1998, and 2000, a leaf spot disease of escarole (Cichorium endivia L.) was widespread among commercial plantings in the Everglades Agricultural Area (EAA), south and east of Lake Okeechobee, FL. Symptoms consisted of dry, dark gray-to-black lesions that expanded to ≈4 cm in diameter. Concentric rings were often observed in mature lesions. Growers and scouts in the area consistently identified this disease as Alternaria leaf spot, because the symptoms closely resembled Alternaria leaf spots seen on a number of other vegetables. Prolific bacterial streaming occurred when cut portions of lesions were observed microscopically. A fluorescent bacterium was consistently isolated when a sterile inoculation needle was pushed through lesions. Eight bacterial strains were isolated, restreaked to obtain pure cultures, and characterized. All strains were aerobic, gram-negative rods that were oxidase positive and arginine dihydrolase negative. Negative reactions were recorded for levan formation and rotting of potato slices. All strains utilized glucose, mannitol, and m-tartrate and were negative for sucrose, sorbitol, benzoate, d-arabinose, l-rhamnose, and cellobiose. Results for utilization of D-aspartate were variable. Based on these results, the causal agent of bacterial leaf spot of escarole was identified as Pseudomonas cichorii. Greenhouse-grown plants of escarole, cv. Full Heart, and Cos lettuce, cv. Tall Guzmaine, were mistinoculated with a suspension (107 CFU/ml) of each test strain from escarole and P. cichorii strain Pc28, originally isolated from celery (1). Plants were bagged for 3 days after inoculation. Symptoms characteristic of this disease were evident on escarole inoculated with all test strains and Pc28 6 days after inoculation. Pure cultures of P. cichorii were recovered from lesions on King's B medium. Three test strains produced mild leaf spot symptoms in Cos lettuce, but the symptoms were distinctly different from those associated with the common bacterial leaf spot of lettuce in Florida caused by Xanthomonas campestris pv. vitians (2). To our knowledge, this is the first report of P. cichorii causing this unusual target spot symptom on escarole in the EAA.

References: (1) K. Pernezny et al. Plant Dis. 78:917, 1994. (2) K. Pernezny et al. Plant Dis. 79:359, 1995.
First Report of Tomato chlorosis virus in Italy
Authors: Accotto G. P. , Vaira A. M. , Vecchiati M. , Finetti Sialer M. M. , Gallitelli D. , Davino M.
Published: May 2007

During winter 2000-2001, an unusual disease of tomato was observed in some greenhouses in Sardinia, Sicily, and Apulia, in southern Italy. Plants were chlorotic and reduced in size, expanded leaves showed interveinal yellowing, and older leaves developed interveinal reddish-bronze necrosis and downward rolling. The symptoms resembled those recently reported from Portugal (1) as induced by Tomato chlorosis virus (ToCV) (family Closteroviridae, genus Crinivirus), a whitefly-transmitted virus new to Europe. Symptomatic leaf tissues were extracted and analyzed by reverse transcription-polymerase chain reaction as described by Louro et al.(1). The 439-bp ToCV-specific DNA fragment was amplified in samples collected from 6 of 14 greenhouses in Sardinia, 2 of 5 greenhouses in Sicily, and 1 of 1 greenhouse in Apulia. The sequence of the fragment obtained from a Sicilian isolate (GenBank Accession No. AY048854) showed more than 99% identity to ToCV isolates (Accession Nos. AF024630 and AF234029) from the United States and Portugal, respectively. Infestations of Trialeurodes vaporariorum and Bemisia tabaci have been reported in autumn. To our knowledge, this is the first report of ToCV in Italy. Although we found the virus in three regions of the country, its distribution is likely to be wider, since the symptoms can be mistaken for those of a physiological disorder or of Tomato infectious chlorosis virus, another crinivirus infecting tomato.

Reference: (1) Louro et al. Eur. J. Plant Pathol. 106:589, 2000.
Occurrence and Geographical Distribution of Tospovirus Species Infecting Tomato Crops in Argentina
Authors: Williams L. V. , Lambertini P. M. López , Shohara K. , Biderbost E. B.
Published: May 2007

“Peste negra” is a disease, caused by tospoviruses, that affects tomato crops in Argentina. Knowledge of the diversity, frequency, and distribution of different tospoviruses is essential for developing a rational control program based on genetic resistance sources. A study of the geographical distribution of tospoviruses affecting tomato crops in Argentina is presented in this paper. The areas surveyed were between the Tropic of Capricorn and 40°S and between longitude 58°W and 70°W. Tospovirus species were identified through double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA), using polyclonal antisera against Tomato spotted wilt virus (TSWV), Groundnut ringspot virus (GRSV), and Tomato chlorotic spot virus (TCSV). From tomato samples that reacted positively with any of the used antisera, 63% were GRSV, 28.2% were TCSV, and 8.8% were TSWV. A differential geographical distribution of tospoviruses was determined. Every plant that tested positive for GRSV was from central and northwest Argentina, while every plant TCSV-positive was from the northeast. TSWV was found only in the Río Negro Valley region in the south of the country. The wide dispersion of GRSV may be related to the spread of Frankliniella shultzei, which transmits this virus more efficiently than other vectors.
Temperature-Dependent Growth and Survival of Xylella fastidiosa in Vitro and in Potted Grapevines
Authors: Feil Helene , Purcell Alexander H.
Published: May 2007

Xylella fastidiosa is a xylem-inhabiting bacterium that causes Pierce's disease (PD) of grapevine. Growth rates of X. fastidiosa in a rich liquid medium were determined by culturing methods at various temperatures. The slope of the regression line between the points of 18 and 28°C was similar to that reported for Escherichia coli between 12 and 30°C and for Erwinia amylovora between 9 and 18°C. For three PD strains, two almond strains, and an oleander strain, X. fastidiosa grew fastest at 28°C but did not grow at 12°C. Grape seedlings kept at 5, 10, 17, or 25°C for 18 days, beginning 2 weeks postinoculation at 25°C, had 230-fold lower populations of X. fastidiosa when kept at 5°C, but populations did not change significantly over time at the other temperatures. In planta populations of X. fastidiosa decreased 3 days after placing the seedlings at 5 and 37°C, and subsequent samples yielded no culturable bacteria at 37°C. Based on in vitro and in planta studies, it appears that temperatures between 25 and 32°C may be critical for the epidemiology of Pierce's disease because of its rapid growth rate at these temperatures, whereas temperatures below 12 to 17°C and above 34°C may affect the survival of X. fastidiosa in plants.
Gladiolus Corm Rot Caused by Sclerotium rolfsii in Argentina
Authors: Rivera M. C. , Wright E. R. , Capucchio S.
Published: May 2007

In 2000, rot was observed on Gladiolus sp. corms produced and stored in a production locale of the Province of Corrientes, Argentina. Symptoms were associated with the development of whitish mycelial strands and light brown 0.8- to 1.5-mm-diameter globose sclerotia typical of Sclerotium rolfsii Sacc. The fungus was isolated on potato dextrose agar. Pathogenicity tests were done by placing plugs of agar media containing mycelium and sclerotia on corms previously wounded with a scalpel. The corms were planted in sterilized soil, incubated at 20 ± 3°C, and watered frequently. Wilt symptoms were observed 40 days after planting. Basal leaves turned yellow and crown and corm rot developed. Thirty-eight percent of the plants failed to emerge due to corm rot. The pathogen was reisolated from inoculated corms that had become diseased. Control corms, which had been inoculated with sterile agar plugs, did not become diseased. The causal agent of the disease was confirmed as S. rolfsii. To our knowledge, this is the first documentation of gladiolus rot caused by S. rolfsii in Argentina.
First Report of Alfalfa Witches Broom Disease in Oman Caused by a Phytoplasma of the 16Sr II Group
Authors: Khan A. J. , Azam K. M. , Deadman M. L. , Al-Subhi A. M. , Jones P.
Published: May 2007

Alfalfa (Medicago sativa L.) is a primary forage crop in the Sultanate of Oman. A new disease of alfalfa in Oman is characterized by proliferation of shoots and yellowing of leaves in 1- to 2-year-old plants and tillering of stems in 4- to 5-year-old plants. Annual losses due to this disease are estimated at more than US$ 23 million. Samples of healthy and infected alfalfa plants were collected from different regions. Total DNA was extracted according to Khadhair et al. (1), with minor modifications. Amplification of 16S rDNA was done using a nested polymerase chain reaction (PCR) approach with primers P1/P7 and R16F2n/R16R2. DNA from healthy leaves and sterile water was used as a negative control, while DNA from periwinkle infected with faba bean phyllody (16SrII-C), aster yellows (16SrI), tomato big bud (16SrII-D), sweet potato little leaf (16SrII-D), catharanthus phyllody (16SrVI), and sesame phyllody (16SrII-A) were used as positive controls and for restriction fragment length polymorphism (RFLP) comparisons. Nested 1.25-kb PCR products from infected plant samples were subjected to RFLP analysis with restriction endonucleases RsaI, AluI, HaeIII, HhaI, EcoRI, TaqI, Tru9I, and Sau3AI. The analysis showed that the alfalfa witches' broom phytoplasma (AWBP) belonged to the 16SrII group (peanut witches' broom) and that the AWBP was most similar to sweet potato little leaf (16SrII-D) but distinct from “Candidatus Phytoplasma aurantifolia,” the cause of lime witches' broom in Oman. Other phytoplasmas infecting alfalfa have been reported from Europe and North America (1,3), but they belong to the 16SrVI (clover phyllody) and 16SrI (aster yellows) groups. An alfalfa witches' broom reported from Italy (2) forms a separate grouping (4). To our knowledge, this is the first report of a phytoplasma from the peanut witches' broom group infecting alfalfa in the Sultanate of Oman.

References: (1) A. H. Khadhair et al. Microbiol. Res. 152:259, 1997. (2) C. Marcone et al. J. Plant Pathol. 79:211, 1997. (3) R. D. Peters et al. Plant Dis. 83:488, 1999. (4) E. Seemuller et al. J. Plant Pathol. 80:3, 1998.
Disease of Floral Buds of Kiwifruit in Spain Caused by Pseudomonas syringae
Authors: González A. J. , Ávila M.
Published: May 2007

In 1999 and 2000, decay of floral buds of Actinidia deliciosa was observed in plantations in the Principality of Asturias, Spain. Bud decay led to a decrease (up to 40%) in the production of kiwifruit. Floral buds with symptoms of browning and necrosis were collected from different areas (Villaviciosa, Grado, and Pravia) and processed for microbiological analysis. A fluorescent bacterium was recovered on King's B medium and identified as Pseudomonas syringae by the LOPAT scheme and Hugh-Leifson reaction (2). Other biochemical features included esculin and gelatin hydrolysis and acid production from mannitol, erythritol, sorbitol, and m-inositol, which are features associated with P. syringae (2). Three isolates from different samples were selected to test pathogenicity using Koch's postulates. Overnight broth cultures of each isolate (109 CFU/ml) were used to infect A. deliciosa in the trials by the following procedures: (i) atomization on branches and buds; (ii) bud injection (1 ml in each bud); and (iii) bud cutting with a scalpel dipped in the suspension. Branches and buds inoculated with sterile water were used as controls. The inoculated parts were enclosed in plastic bags for 48 h. Assays were repeated at least twice. Disease symptoms appeared 2 days later, initially as dark brown spots that developed into an extensive bud rot in all inoculated cases, while no symptoms occurred in controls. P. syringae was successfully recovered from infected samples but not from control samples. The data support the pathogenicity of P. syringae on A. deliciosa. Although P. syringae was previously reported in Italy as the causal agent of disease on floral buds of A. deliciosa (1), to our knowledge, this is the first report of infection of kiwifruit by this pathogen in Spain.

References: (1) G. M. Balestra and L. Varvaro. J. Phytopathol. 145:375, 1997. (2) MAPA, Manual de laboratorio, MAPA, Madrid, Spain, 1991.
First Report of Tomato spotted wilt virus and Impatiens necrotic spot virus in Slovenia
Authors: Mavrič I. , Ravnikar M.
Published: May 2007

In July 2000, concentric necrotic rings and patterns were observed on greenhouse-grown pepper (Capsicum anuum L. ‘Blondi’). Symptoms were present only on lower leaves, not on young leaves or fruits. Typical tospovirus particles using electron microscopy were observed in leaf-dip preparations of symptomatic leaves. Impatiens necrotic spot virus (INSV) was detected in symptomatic but not in asymptomatic tissues using double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) with polyclonal antiserum (Loewe Biochemica, Sauerlach, Germany). Nicotiana benthamiana, N. rustica, and Petunia sp. were mechanically inoculated with sap of symptomatic leaves. Local and systemic symptoms were observed only on N. benthamiana. Tomato spotted wilt virus (TSWV) infections were later confirmed in some pepper and tomato plants with distinct systemic symptoms and in greenhouse-grown chrysanthemums, calla lilies, cyclamen and spatiphylum using DAS-ELISA with polyclonal antiserum. Severe systemic symptoms were observed only on some chrysanthemum cultivars, where the infection rate of TSWV was between 80 and 100%. Such TSWV-infected plants were not marketable. Symptomless infections by the same virus were also found. At one location, calla lilies were heavily infected by TSWV, but only local symptoms on leaves were observed. INSV was also confirmed using DAS-ELISA on different chrysanthemum cultivars. Mixed infections of TSWV and INSV were detected using DAS-ELISA on calla lilies with local necrotic rings and patterns on leaves and on Impatiens walerana with systemic necrosis. A limited number of weeds from the vicinity of greenhouses containing symptomatic plants were tested for the presence of TSWV using DAS-ELISA, and only Artemisia vulgaris was infected. Both viruses, TSWV from chrysanthemum and INSV from pepper, were isolated on test plants, and their identity was confirmed using DAS-ELISA. For further verification of TSWV and INSV infection, immunocapture reverse-transcription polymerase chain reaction was performed using general tospovirus primers (1). Amplification products of the expected size were detected and sequenced. Comparison of nucleic acid sequences of amplification products with viral sequence databases confirmed the identities of both viruses. To our knowledge, this is the first report of TSWV and INSV infection in ornamental and vegetable plants in Slovenia.

Reference: (1) R. J. Weekes et al. Acta Hortic. 431:159, 1996.
First Report of Tubakia dryina in Buds and Shoots of Quercus cerris and Quercus robur
Authors: Gennaro M. , Gonthier P. , Nicolotti G. , Cellerino G. P.
Published: May 2007

Tubakia dryina (Sacc.) Sutt. (teleomorph Dicarpella dryina Belisario & Barr) is a widespread leaf pathogen in northern temperate zones and is mainly associated with Quercus spp. During 2000, T. dryina was isolated from seasonal samplings of endophytic fungal communities of Turkey (Q. cerris L.) and English (Q. robur L.) oaks. Samples were taken from healthy and declining trees showing no symptoms of T. dryina in a coppice with saplings in Piedmont (northwestern Italy). Fragments of freshly opened buds (1-year-old shoots) and leaves were surface-sterilized by immersion in 75% ethanol for 1 min, in a NaClO solution (3 to 4% active ingredient) for 3 min, and in 75% ethanol for 30 s, then plated on potato dextrose agar. T. dryina was found in all sampled tissues. Its frequency in buds was higher in healthy trees than in declining trees (≈25 versus 12%; analysis of variance test P < 0.05), whereas no difference was found in shoots. T. dryina was also isolated from asymptomatic leaves, but more often from declining trees than from healthy ones (≈40 versus 10%; P < 0.05). No differences were observed when comparing the two oak species. The fungus was previously reported in buds of Q. nigra L. in North America (2), and it has also been isolated from symptomatic leaves of Q. cerris in a 5-year-old plantation (1). T. dryina was found in other studies in leaves and dead twigs of Q. robur. To our knowledge, this is the first report of T. dryina in buds and shoots of European oak species, suggesting an important role of this fungus as either an endophyte or a latent pathogen associated with oak decline.

References: (1) A. Belisario. Plant Dis. 77:647, 1993. (2) Y. C. Zhang and J. T. Walker. Plant Dis. 79:568, 1995.
A New Semi-Selective Medium forXanthomonas campestrispv.vitians, the Causal Agent of Bacterial Leaf Spot of Lettuce
Authors: Toussaint V. , Morris C. E. , Carisse O.
Published: May 2007

A semi-selective medium containing maltose, methyl green, and antibiotics (MMG) was developed for the isolation of Xanthomonas campestris pv. vitians. The semi-selective medium was evaluated based on plating efficiency of X. campestris pv. vitians in cell suspensions of pure cultures from leaves and soil. MMG medium allowed recovery of 5.7 to 30.6% of the X. campestris pv. vitians colonies recovered on nutrient agar and 0.1 to 8.4% of those recovered on 1/10-strength tryptic soy agar. MMG inhibited growth of most background bacteria and allowed reliable identification of X. campestris pv. vitians. The semi-selective medium contained (per liter) maltose (10 g), tryptone (5 g), K2HPO4(3.5 g), KH2PO4(2.75 g), trace elements (0.02 to 1.0 mg), methyl green (2 ml of a 1% aqueous solution), amoxicillin (32 mg), cephalothin (32 mg), cycloheximide (50 mg), and agar (15 g).
Effect of Temperature and Water Potential on Survival and Mycelial Growth ofPhaeomoniella chlamydosporaandPhaeoacremoniumspp.
Authors: Whiting E. C. , Khan A. , Gubler W. D.
Published: May 2007

Phaeomoniella chlamydospora, a species of Phaeomoniella, and two species of Phaeoacremonium, P. inflatipes and P. aleophilum, have been associated with young grapevine decline in major production regions of California. Phaeomoniella chlamydospora has been isolated from healthy vines and inoculated but non-symptomatic vines and rooted cuttings. Effects of temperature and water potential on fungal response in culture were investigated to find effective control strategies for nurseries. Mycelial growth rates at temperatures 5 to 37°C showed a quadratic response with optimum growth rates for Phaeomoniella chlamydospora and P. aleophilum at 25°C and at 30°C for P. inflatipes. Response to water potential varied by isolates within a species, but isolates of Phaeomoniella chlamydospora were not sensitive to decreasing water potential. A conidial suspension and plugs of agar with mycelia were placed in glass vials and incubated in hot water for 15 to 120 min. Conidia were sensitive to hot-water treatment after 15 and 30 min. Nevertheless, mycelia of P. inflatipes from agar plugs grew on potato dextrose agar at 22°C after 120 min incubation at 51°C. Because the fungi were not killed by incubation in glass vials at 51°C, methods other than hot-water treatment may be more effective in eliminating Phaeomoniella chlamydospora and Phaeoacremonium spp. from dormant vine cuttings.
First Report of Citrus leprosis virus in Panama
Authors: de Dominguez Fanny Saavedra , Bernal Antonio , Childers Carl C. , Kitajima Elliot W.
Published: May 2007

Citrus is a rapidly expanding fruit crop in Panama with a planted area of approximately 14,000 ha, with the crop destined for both table and juice industries for local and foreign markets. Chiriqui Province in extreme western Panama borders Costa Rica and grows 4,300 ha of citrus that consists primarily of Valencia and navel oranges with the remainder grown throughout other provinces. Some plants in commercial groves in Potrerillos and Boquete in Chiriqui Province were found with leaf (chlorotic spots or rings), stem (necrosis), and fruit (localized ringlike or depressed lesions) symptoms similar to those caused by Citrus leprosis virus (CiLV) (3). In Potrerillos, wood samples about 3 years old were identified in two of the citrus groves, indicating that the infection was established on or before 1996. The mite Brevipalpus phoenicis (Geijskes) (Acari: Tenuipalpidae) was collected in all leprosis-infected or suspected groves in both Potrerillos and Boquete. CiLV is known to be transmitted by B. obovatus Donnadieu and B. phoenicis in Argentina and Brazil, respectively (3). To confirm the presence of this virus, 20 samples (12 from Boquete [B] and 8 from Potrerillos [P]) of leaf and fruit lesions were fixed in a modified Karnovsky solution and sent to Brazil for electron microscopic examination of thin sections. In 8 samples (2 from B and 6 from P) cytopathic effects were found characterized by a dense viroplasm in the cytoplasm and short, bacilliform particles (50 to 60 × 100 to 110 nm) in the lumen of the endoplasmic reticulum, features similar to those reported by Colariccio et al. (1). In 6 samples (5 from B, and 1 from P), the cytopathic effects were similar to those observed in Orchid fleck virus (OFV)-infected cells (2), with an intranuclear, electron lucent viroplasm and short, rodlike particles (40 to 50 nm × 100 nm) either within the nucleus or in the cytoplasm, as also previously reported for a sample of CiLV in Brazil (4). The symptomatology, presence of the mite vector, characteristic cytopathic effects, and presence of virions are considered to be evidence that CiLV is present within a 100 km2 area of Potrerillos and 25 km2 of Boquete in Chiriqui Province. This is the first report of the presence of CiLV in Central America, suggesting that the virus has spread northward from South America.

References: (1) A. Colariccio et al. Fitopatol. Bras. 20:208, 1995. (2) Y. Doi et al. AAB/CMI Description of Plant Viruses No. 183, 1977. (3) S. M. Garnsey and C. M. Chagas. 2000. Pages 57–58 in: Compendium of Citrus Diseases, 2nd Ed. L. W. Timmer et al, eds. APS Press, St.Paul, MN. (4) E. W. Kitajima et al. Virology 50:254, 1972.
Alternaria alternata Flower Blight of Zinnia acerosa in Texas
Authors: Colbaugh P. F. , Mackay W. A. , George S.
Published: May 2007

Zinnia acerosa (D.C.) Gray, is a Southwest native flowering plant frequently observed in the Trans-Pecos desert and desert grasslands of Arizona, Texas, and New Mexico. The plant is valued for producing an abundance of distinctive 2.0 cm diameter white flowers on greenish and sparsely leaved stems. Selections of Z. acerosa from West Texas are under evaluation as a water conserving plant species for use in arid landscapes of the Southwest. During April through June, Z. acerosa plants in TAMU, Dallas field plots were observed with small, brown flower spots that enlarged to include whole petals, causing conspicuous flower blighting. Microscopic examination of lesions from infected flower blossoms demonstrated the presence of short beaked, cylindrical spores near the smaller lesions on flower petals. Isolations from symptomatic flower petals consistently yielded cultures of an Alternaria sp. with long chains of conidia. Typical conidia contained 3 to 5 transverse walls and 1 to 2 longitudinal walls and measured 43 μm length by 15 μm width. The fungus was identified as A. alternata (Fries) Keissler consistent with the description in Ellis (1). Pathogenicity tests were conducted on plants maintained on a greenhouse bench by spraying spore suspensions obtained from 16-day-old A. alternata cultures on potato-dextrose agar. Inoculations produced light brown lesions on blossoms typical of field disease symptoms of the disease. This disease is important as a flower blight, however, infections on the leaves are also apparent but limited. Outbreaks of the disease are frequently observed during periods of rainfall during the summer months. This is the first report of Alternaria alternata causing a floral blight on Z. acerosa.

References: (1) M. B. Ellis. 1971. Dematiaceous Hyphomycetes. Commonwealth Mycological Institute, Kew, Surrey, England.