bluuebunny/crossref_metadata_2025 huggingface dataset:
Evidence for Induced Systemic Protection to Fusiform Rust in Loblolly Pine by Plant Growth-Promoting Rhizobacteria
Authors: Enebak S. A. , Carey W. A.
Published: May 2007

Trials conducted in 1997 and 1998 tested eight strains of plant growth-promoting rhizobacteria (PGPR) for their capacity to induce systemic protection in loblolly pine to the causal agent of fusiform rust. Pine seeds were treated with bacteria at time of sowing, and seedlings were artificially inoculated with basidiospores of Cronartium quercuum f. sp. fusiforme 1 month later. Six months after basidiospore inoculation, seedlings were evaluated for the fusoid swelling or galls characteristic of rust infection. Compared with seedlings from seed not treated with bacteria, two bacterial isolates, Bacillus pumilus (SE34) and Serratia marcescens (90–166), significantly (P = 0.05) reduced the number of galls in 1997 and 1998. Combined data from 1997 and 1998 resulted in two additional isolates, B. pumilus (INR7) and B. pumilus (SE52), significantly (P = 0.05) reducing the number of galls. Averaged over both years, 31% of control seedlings were infected with fusiform rust, while those seedlings treated with bacterial strains SE34, 90–166, INR7, and SE52 had 13, 14, 15, and 16% infection, respectively. These four PGPR strains appear to have induced systemic resistance to fusiform rust in loblolly pine, resulting in less infection over nontreated control seedlings.
Pathogenicity of Toxigenic Fusarium proliferatum from Date Palm in Saudi Arabia
Authors: Abdalla M. Y. , Al-Rokibah A. , Moretti A. , Mulè G.
Published: May 2007

Fusarium proliferatum was isolated for the first time from roots and leaves of declining date-palm trees (Phoenix dactylifera L.) in the Al-Qassim and Al Medina Al Monawara regions in Saudi Arabia. The disease symptoms caused by F. proliferatum, which include wilt and dieback, were similar to those caused by F. oxysporum f. sp. albedinis, the causal agent of Bayoud, the most important disease of date palm found in North Africa. Koch's postulates were completed by stem injection of date-palm seedlings using two strains of F. proliferatum. The pathogenicity tests, performed on local cv. Succary using two strains of F. proliferatum isolated from roots, produced severe symptoms of disease. The identity of F. proliferatum was confirmed by comparing the data obtained by partial sequences of a large subunit of rDNA to American and European Gene Bank data. All nine F. proliferatum strains isolated from diseased plants were shown to belong to mating population D of Gibberella fujikuroi. Finally, the strains were also tested for the production of beauvericin, fumonisin B1, fusaproliferin, fusaric acid, and moniliformin. Two strains out of nine were able to produce all five toxins and all strains produced at least three of them. This is the first time that toxigenic F. proliferatum strains known to belong to mating population D of G. fujikuroi were isolated from diseased date-palm plants.
Biological Control of Cyclamen Soilborne Diseases by Serratia marcescens Strain B2
Authors: Someya N. , Kataoka N. , Komagata T. , Hirayae K. , Hibi T. , Akutsu K.
Published: May 2007

Cyclamen plants were treated with a highly chitinolytic bacterium, Serratia marcescens strain B2, and then challenge inoculated with Rhizoctonia solani sclerotia or Fusarium oxysporum f. sp. cyclaminis conidia. The bacterium suppressed these fungal diseases of cyclamen plants, especially the damping off caused by R. solani, in a greenhouse. Strain B2 survived at approximately 106 to 107 CFU/g in soil for 4 months after the initial application under greenhouse conditions. Chitinolytic enzymes and antifungal low-molecular-weight compounds were present in filtrates of S. marcescens B2, which suppressed germination of R. solani sclerotia in vitro.
Characterizing the Sphaceloma Fungus, Causal Agent of Superelongation Disease in Cassava
Authors: Alvarez Elizabeth , Molina Martha L.
Published: May 2007

The fungus Sphaceloma manihoticola causes superelongation disease in cassava, a starchy root crop grown widely in the tropics. Isolates were collected from infected plants grown in six localities of Colombia. Morphological analyses of the fungus showed that colony growth and color are not stable characteristics over time. Pathogenicity studies, using the susceptible cassava variety M Col 22 and the resistant M Ven 77, showed that M Col 22 was tolerant of 29% of pathogen isolates studied and had an intermediate reaction to 71%. Variety M Ven 77 also showed tolerance of 16.2% of the isolates, had an intermediate reaction to 80.6%, and was susceptible to 3.2%. Significant cultivar × isolate interactions indicated pathogenic specialization. This study is the first to describe this pathogen's molecular characteristics. A homogeneous and reporducible band of about 545 bp was obtained with polymerase chain reaction which, when digested by restriction enzymes, showed an equal pattern of bands for all isolates. The isolates thus belonged to one species. Random amplified polymorphic DNA analysis revealed intraspecific genetic diversity. By better understanding the pathogen, we can apply more appropriate disease management strategies, such as selection of germ plasm tolerant of superelongation disease.
Influence of Meloidogyne incognita and Thielaviopsis basicola Populations on Early-Season Disease Development and Cotton Growth
Authors: Walker N. R. , Kirkpatrick T. L. , Rothrock C. S.
Published: May 2007

Microplot studies were used to examine the effect of various population densities of Meloidogyne incognita and Thielaviopsis basicola on cotton-plant development and disease severity. Plots were infested with 0, 20, or 100 T. basicola chlamydospores/g and 0, 5, or 10 M. incognita eggs and juveniles/cm3 of soil in a factorial arrangement in 1997 and 1998. Combinations of M. incognita and T. basicola reduced plant survival in both years compared to the noninfested control, except in 1998 for the high rate of T. basicola over all nematode rates. Plant height-to-node ratios were reduced by pathogen combinations compared to the noninfested control or to either pathogen alone. Plant dry weight was reduced by M. incognita in 1998 and the high rate of T. basicola in 1997. Root necrosis was increased by increasing rates of T. basicola in 1997 and by M. incognita over all rates of T. basicola in both years. Colonization of root tissue by T. basicola was increased by the low inoculum density of the nematode at 20 CFU/g soil in 1997 and 100 CFU/g in 1998. Nematode reproduction with the high M. incognita treatment rate was reduced in both years of the study by the high T. basicola rate. This study suggests the importance of population level of each pathogen to the severity of disease and confirms the potential of this disease interaction to impact cotton production.
A Widely Distributed Lineage ofXanthomonas oryzaepv.oryzaein India May Have Come from Native Wild Rice
Authors: Yashitola J. , Reddy A. P. K. , Sonti Ramesh V.
Published: May 2007

Xanthomonas oryzae pv. oryzae causes bacterial leaf blight, a serious disease of rice. We have collected leaf blight-affected samples from wild rice (Oryza nivara) plants growing naturally at 22 locations in five revenue districts (Nalgonda, Ranga Reddy, Medak, Nizamabad, and Adilabad) in the Telangana Region of Andhra Pradesh, India. Pathotype analysis on a set of differential rice cultivars and DNA fingerprinting with two multilocus restriction fragment length polymorphism probes indicated that the X. oryzae pv. oryzae strains from the O. nivara plants belonged to a pathotype and lineage previously widely distributed among cultivated rice in India. This suggests that the lineage may be native to wild rice and may have been transferred subsequently to cultivated rice plants.
First Report of Ovulariopsis on Lupinus havardii
Authors: Fernández-Pavía S. P. , Valenzuela-Vázquez M.
Published: May 2007

In 1998 and 1999 a severe powdery mildew was observed in Las Cruces, NM, on Big Bend Bluebonnets (Lupinus havardii) grown in the greenhouse for cut flowers and vase life studies. An undescribed powdery mildew has been reported on L. havardii (2), but it has been observed only occasionally on leaves and has not cause a severe problem. The powdery mildew observed in Las Cruces began in March and caused severe infection from May through July. The disease spread rapidly due to movement of the pathogen during pruning operations and the close proximity of plants. Plants were heavily infected when no fungicide was applied. Plants were sprayed with the fungicide azoxystrobin, with best control obtained at 687 mg/liter of water. When an infected plant was used as a source of inoculum, disease spread rapidly to healthy plants placed around the infected plant. Infected leaves had chlorotic lesions that later became necrotic. Mycelia, conidiophores, and conidia of the pathogen were observed on leaves and occasionally on petioles and stems. Ellipsoid cylindrical-to-clavate conidia were hyaline, one-celled, and measured 49 to 68.1 μm × 12.2 to 14.7 μm. Conidia were produced on upright, simple conidiophores measuring 171 to 245 μm × 4.9 to 7.3 μm. Fibrosin bodies and cleistothecia were not found. The fungus was identified as an Ovulariopsis sp. (1). This is the first documented report of an Ovulariopsis sp. on L. havardii.

References: (1) U. Braun. Beih. Nova Hedwigia 89:1, 1987. (2) W. A. Mackay and T. D. Davis. HortScience 33:348, 1998.
Races of Phytophthora sojae on Soybean in Illinois
Authors: Leitz R. A. , Hartman G. L. , Pedersen W. L. , Nickell C. D.
Published: May 2007

Phytophthora root rot of soybean (Glycine max (L.) Merr.), caused by Phytophthora sojae M. J. Kauffmann & J. W. Gerdemann, has been isolated throughout the soybean-producing regions of the United States. There are more than 39 identified races of P. sojae pathogenic on soybean, and 13 host resistance alleles have been identified at 7 loci (1). None of these alleles confers resistance to all races of P. sojae. The most commonly used resistance allele, Rps1k, confers resistance to the greatest number of races (2). The objective of this study was to identify races of P. sojae in Illinois soybean fields to determine whether the currently used resistance alleles are effective against the P. sojae races found in Illinois. Soybean breeders must be aware of the existence and distribution of races to incorporate appropriate sources of genetic resistance into cultivars. From 192 soil samples collected throughout Illinois in 1997, 33 isolates were obtained and identified to race by inoculating Rps isolines of soybean cv. Williams. A new race with virulence to the Rps1d and Rps7 alleles, designated as race 54, accounted for 48% of the isolates. Another new race with virulence to Rps1d, Rps3a, Rps3c, Rps4, Rps5, Rps6, and Rps7 alleles, designated race 55, was identified in one sample. One isolate, identified as race 41, was obtained from a diseased plant with the Rps1k allele. Another isolate, identified as race 43, was obtained from a diseased plant with the Rps1c allele. Based on virulence patterns of P. sojae, most of the isolates obtained from Illinois soils were races 1, 3, and 4 or variants of these races, such as race 54, with added virulence to the Rps1d allele.

References: (1) A. F. Schmitthenner. 1999. Compendium of Soybean Diseases. 4th ed. G. L. Hartman, J. B. Sinclair, and J. C. Rupe, eds. The American Phytopathological Society, St. Paul, MN. pp. 39‐42. (2) A. F. Schmitthenner, M. Hobe, and R. G. Bhat. Plant Dis. 78:269, 1994
Outbreaks of Stem and Leaf Blight of Eustoma grandiflorum Caused by a Phomopsis sp. in Florida
Authors: McGovern R. J. , Seijo T. E. , Harbaugh B. K. , Schubert T. S.
Published: May 2007

Between November 1997 and May 1998, numerous lisianthus (Eustoma grandiflorum) cultivars exhibited severe stem and leaf blight at two pot-flower production sites in Hillsborough and Dade counties, FL. Blight occurred in mature plants and ranged in incidence from 3 to 5% in Dade County and from 40 to 80% in Hillsborough County. Initial stem necrosis was rapidly followed by leaf blight and production of numerous dark pycnidia in diseased tissue. As stem blight progressed, infected plants collapsed and died. Pycnidia contained biguttulate, 7.2 × 2.2-μm spores typical of Phomopsis alpha conidia; beta conidia were not observed. A Phomopsis sp. was isolated consistently when pycnidia from symptomatic stems were placed on acidified 25% potato dextrose agar after surface-disinfestation in 0.5% NaOCl; only alpha conidia were observed in culture. Pathogenicity was confirmed using a suspension of hyphae, pycnidia, and conidia made by comminuting one 95-mm-diameter acidified carnation leaf agar plate containing a 4-week-old colony of the Phomopsis sp. in 100 ml of deionized water. Six plants of lisianthus ‘Maurine Blue’ (three wounded at the crown, three nonwounded) each were inoculated with 10 ml of the fungal suspension. An equal number of noninoculated lisianthus (three wounded, three nonwounded) served as controls. After inoculation, plants were maintained in a greenhouse with average high and low temperatures of 38 and 25°C, respectively. Stem and leaf blight symptoms were observed in two of three wounded plants and in all nonwounded plants within 11 and 15 days after inoculation, respectively. Infection by a Phomopsis sp. was confirmed by reisolation from symptomatic tissue. Although this Phomopsis sp. has been detected previously in lisianthus exhibiting leaf and stem lesions (1), this report establishes the ability of the of the fungus to act as a primary pathogen and to cause extensive losses in this crop.

Reference: (1) Alfieri et al. 1994. Diseases and Disorders of Plants in Florida. Bull. No. 14. Division of Plant Industry, Gainesville, FL.
First Report of Tomato spotted wilt virus in Common Agapanthus
Authors: Wilson C. R. , Wilson A. J. , Pethybridge S. J.
Published: May 2007

Common agapanthus (Agapanthus praecox subsp. orientalis), native to South Africa, is a popular ornamental flowering bulb species belonging to the Amaryllidaceae and is commonly found in residential gardens. Roots from some Agapanthus sp. also are used in traditional medicine in Africa. Common agapanthus collected from a residential property in Hobart, Tasmania, Australia, showed leaf symptoms of concentric ring and line patterns, irregular chlorotic blotches, and streaks. Symptomatic plants were severely stunted and failed to flower. Symptomatic leaves prematurely senesced, but young foliage subsequently produced was symptomless. Similar symptoms have been reported in other members of the Amaryllidaceae and are associated with infection by Tomato spotted wilt virus (TSWV; e.g., Nerine and Hippeastrum spp.) or Cucumber mosaic virus (CMV; e.g., Hippeastrum sp.) (2). The presence of TSWV and absence of CMV in symptomatic plants of common agapanthus was determined by enzyme-linked immunosorbent assay. Confirmation of TSWV infection was provided by reverse-transcription polymerase chain reaction assay with primers specific to the nucleocapsid protein gene of TSWV, with nucleic extracts from symptomatic plants producing an expected ≈800-bp amplicon (1). This is the first report of TSWV infection of any species within the Amaryllidaceae in Australia and the first report of the occurrence of TSWV in common agapanthus.

References: (1) R. K. Jain et al. Plant Dis. 82:900, 1998. (2) G. Loebenstein et al. 1995. Virus and Virus-like Diseases of Bulb and Flower Crops. John Wiley & Sons, Chichester, U.K.
Pittosporum tobira: A New Host for Tomato spotted wilt virus
Authors: Gera A. , Kritzman A. , Cohen J.
Published: May 2007

In July 1998, Pittosporum tobira shrubs, grown in a nursery in the Sharon Valley of Israel, developed foliar ring spots, mild mosaic, and tip necrosis. Of 15 samples tested for the presence of Tomato spotted wilt virus (TSWV) with a commercially available enzyme-linked immunosorbent assay (ELISA) kit (Loewe Biochemica, Otterfing, Germany), 14 were positive for TSWV. Virus in crude sap extracted from symptomatic tissue was mechanically transmitted to Emilia spp., Petunia hybrida, Nicotiana glutinosa, N. benthamiana, and N. rustica plants, which developed symptoms characteristic of TSWV infection (1). ELISA tests of leaf sap extracted from naturally infected P. tobira and mechanically inoculated indicator plants gave a strong positive reaction to TSWV. Leaf samples of P. tobira were analyzed by transmission electron microscopy in leaf-dip preparations and thin sections of leaf tissues. Virus particles typical of a tospovirus were observed only in samples taken from symptomatic leaves. Primers specific to the nucleocapsid gene of TSWV were used in a reverse transcription-polymerase chain reaction (RT-PCR) assay to verify the presence of TSWV. RT-PCR gave an expected PCR product of ≈850 bp. The amplicon was cloned in the pGEM-T vector, and the recombinant clone was sequenced. The sequence of the cloned PCR product confirmed the identity of TSWV, verifying TSWV infection of P. tobira. This is the first report of infection of P. tobira by TSWV.

Reference: (1) Y. Antignus et al. Phytoparasitica 25:319, 1997.
Spatial Analyses of Viral Epidemics in Australian Hop Gardens: Implications for Mechanisms of Spread
Authors: Pethybridge Sarah J. , Wilson Calum R. , Ferrandino Francis J. , Leggett Grey W.
Published: May 2007

Plant-to-plant spread of Hop mosaic virus (HpMV), Hop latent virus (HpLV), and Prunus necrotic ringspot virus (PNRSV) were monitored in two commercial hop gardens of cv. Victoria in Australia. At site 1, the cultural practice of mowing to remove excess basal growth operated exclusively along rows, while at site 2, mowing occurred both along and across rows. Other cultural practices such as stringing, bine-training, spraying, and harvesting were directed along rows at both sites. Spatial aggregation within and across rows was assessed by ordinary runs analysis, and by radial correlation analysis using the program 2DCORR. The dominant spread mechanism of carlaviruses differed between sites. At site 1, along-row aggregation of both HpLV and HpMV in 1997 reflected the importance of basal-growth intertwining for virus transmission, either due to mechanical transmission or movement of apterous or alatae vectors along rows. At site 2, the random incidence of HpLV and HpMV reflected spread by alatae vectors. The spread of PNRSV at both sites was associated with mowing direction. This study reports the first use of a modified version of radial correlation analysis.
Evaluation of a Disease Warning System for Downy Mildew of Grapes
Authors: Madden L. V. , Ellis M. A. , Lalancette N. , Hughes G. , Wilson L. L.
Published: May 2007

An electronic warning system for grape downy mildew— based on models for the infection of leaves of Vitis lambrusca, production of sporangia by Plasmopara viticola in lesions, and sporangial survival—was tested over 7 years in Ohio. Grapevines were sprayed with metalaxyl plus mancozeb (Ridomil MZ58) when the warning system indicated that environmental conditions were favorable for sporulation and subsequent infection. Over the 7 years, plots were sprayed from one to four times according to the warning system, and from four to 10 times according to the standard calendar-based schedule (depending on the date of the initiation of the experiment). The warning system resulted in yearly reductions of one to six sprays (with median of three sprays). Disease incidence (i.e., proportion of leaves with symptoms) in unsprayed plots at the end of the season ranged from 0 to 86%, with a median of 68%. Incidence generally was very similar for the warning-system and standard-schedule treatments (median of 7% of the leaves with symptoms), and both of these incidence values were significantly lower (P < 0.05) than that found for the unsprayed control, based on a generalized-linear-model analysis. Simplifications of the disease warning system, where sprays were applied based only on the infection or sporulation components of the system, were also effective in controlling the disease, although more fungicide applications sometimes were applied. Effective control of downy mildew, therefore, can be achieved with the use of the warning system with fewer sprays than a with a standard schedule.
Mechanism of Suppression of Meloidogyne hapla and Its Damage by a Green Manure of Sudan Grass
Authors: Widmer T. L. , Abawi G. S.
Published: May 2007

Meloidogyne hapla is a continuing problem on vegetables in the state of New York. Sudan grass has been demonstrated to suppress infection and damage to susceptible vegetables caused by this nematode when incorporated as a green manure. Some Sudan grass cultivars contain the cyanogenic glucoside dhurrin that is degraded through an intermediate step to p-hydroxybenzal-dehyde (p-HBA) and HCN. Incubating M. hapla eggs in Sudan grass extract resulted in a 55% reduction in the number of juveniles (J2) penetrating lettuce roots. Juveniles exposed to the extracts were not affected. Sudan grass extract affected egg maturation by delaying development, but did not affect hatching. Exposing eggs to a 0.1 ppm CN- solution reduced the number of nematodes that penetrated the roots by 48%, while exposing J2 to the same concentration reduced nematode infection by only 4%. However, exposure of eggs to p-HBA did not reduce J2 penetration into roots. After purifying Sudan grass extract through size-exclusion resin, only the fractions collected that contained cyanide suppressed infection of lettuce roots by M. hapla J2 when eggs were exposed to these fractions. These results suggest that CN- is the primary factor involved in the suppression of M. hapla by a green manure of Sudan grass.
First Report of Stem Canker of English Walnut Caused by Fusarium solani in South Africa
Authors: Chen W. , Swart W. J.
Published: May 2007

Cultivation of English walnut (Juglans regia L.) has considerable economic potential in South Africa. In February 1999, die-back of walnut trees was observed on ≈30% of trees in an orchard in Gauteng Province, South Africa. Die-back was associated with characteristic cankers and discoloration of the cambial tissue of twigs and young branches. Fifty pieces of discolored tissue from the margins of cankers of five trees were transferred to potato dextrose agar (PDA) after surface-sterilization with 0.5% NaOCl. Fungal colonies emerged from all 50 pieces of diseased tissue. Fungi recovered included Fusarium solani (74.5%), Alternaria tenuissima (17.3%), and a Phoma sp. (6.2%). Small pieces of sterile cheesecloth (10 × 5 mm) were cultured on PDA with an isolate of F. solani from infected walnut trees. Colonized pieces of cheesecloth were applied to stems (≈5-mm diameter) of nine potted J. regia plants in a glasshouse. Each stem was wounded by lightly scraping off a length of bark (5 × 5 mm). Colonized cheesecloth was wrapped around the wound and covered with Parafilm to prevent desiccation of mycelia in the cheesecloth. Nine walnut stems were similarly treated with sterile cheesecloth pieces to serve as control treatments. After 4 weeks, die-back of foliage was observed in all plants artificially inoculated with F. solani. Cheesecloth pieces and surrounding bark were removed, and the length and width of each cambial lesion was measured. The mean area of cambial lesions (length by width) resulting from artificial inoculations was 27.3 × 8.5 mm. None of the control plants developed any symptoms. Koch's postulates were confirmed by consistently reisolating F. solani from inoculated plants. A similar disease of black walnut (J. nigra) was reported by Carlson et al. (1) from five central states in the United States. Our findings represent the first report of F. solani as a causal agent of stem canker of English walnut in South Africa.

Reference: (1) J. C. Carlson et al. N. J. Appl. For. 10:1, 1993.
First Reports of Aphelenchoides fragariae on Royal Fern and on Hosta and Other Hosts in South Carolina
Authors: Williamson M. R. , Blake J. H. , Jeffers S. N. , Lewis S. A.
Published: May 2007

In September 1999, royal ferns (Osmunda regalis L.) at a South Carolina wholesale nursery were found to be infected by foliar nematodes. Lesions were brown, vein-limited, and often fan shaped. As severity increased, affected leaflets became totally necrotic. Nematodes were extracted by excising and dicing symptomatic leaf sections and placing them in water for up to 24 h. Ten adult nematodes from each of two fern plants were examined microscopically and determined to be Aphelenchoides fragariae (Ritzema Bos) Christie. This is the first report of this nematode infecting royal fern. In August 1996, leaves from several cultivars of Hosta spp. with yellow to tan, vein-limited lesions were submitted from The South Carolina Botanical Garden (Clemson, SC) to the Clemson University Plant Problem Clinic for diagnosis. Nematodes were extracted and examined as described above and identified as A. fragariae. This is the first report of this nematode infecting Hosta spp. in South Carolina. Since 1996, foliar nematodes have been recovered from hostas at several wholesale nurseries in South Carolina. Aphelenchoides spp. also have been detected previously in commercially produced ornamental plants in South Carolina, including a Begonia sp. in 1988; Polygonum bistorta L. ‘Super-bum’ (snakeweed) in 1997; and a Polystichum sp. (holly fern) in 1997. All plants exhibited angular or vein-limited, necrotic lesions typical of foliar nematode infections.
Outbreak of Eremothecium coryli Fruit Rot of Tomato in California
Authors: Miyao G. M. , Davis R. M. , Phaff H. J.
Published: May 2007

A ripe fruit rot of tomato (Lycopersicon esculentum) associated with stink bug (Euschistus conspersus) feeding caused extensive losses in the Sacramento Valley of California in 1998. Portions of several fields were abandoned at harvest due to fruit rot levels >30%. Symptoms included a soft, water-soaked rot often surrounding a firm, dark green island. Entire fruit sometimes became watery and soft. The ascomycetous yeast, Eremothecium coryli, characterized by spindle-shaped ascospores with long, thin, whip-like terminal appendages (1), was consistently isolated from diseased tissue plated on V8 or potato dextrose agar amended with tetracycline. Ripe tomato fruit were inoculated with a 0.1-ml suspension of 1.5 × 105 ascospores per ml injected to a depth of ≈4 mm to simulate stink bug probing. Fruit were placed in plastic containers and, in initial tests, were held at room temperature. In subsequent tests, inoculated fruit were maintained at constant temperatures of 20, 25, 30, or 35°C. Controls included inoculum either placed on the fruit surface or injected with sterilized water. Each treatment consisted of one to four fruit in two to four replications. All experiments were repeated. Lesions were visible within 5 days after inoculation and were >25 mm in diameter after 7 days. Progression of rot occurred at all temperatures but was fastest at 30 and 35°C. Controls remained symptomless. E. coryli was reisolated from infected fruit. This is the first documentation of field-level losses caused by E. coryli associated with stink bug feeding. Isolates are maintained in the Herman J. Phaff Collection of Yeast and Yeast-like Microorganisms at the University of California, Davis.

Reference: (1) G. S. de Hoog et al. 1998. Eremothecium Borzi emend. Kurtzman. Pages 201-208 in: The Yeasts—A Taxonomic Study. C. P. Kurtzman and J. W. Fell, eds. Elsevier Scientific Publishers, Amsterdam.
First Report of Barley yellow streak mosaic virus-Infected Barley in Alaska
Authors: Robertson N. L. , Brumfield S. K.
Published: May 2007

Barley yellow streak mosaic virus (BaYSMV) was first described and reported in Montana and Alberta, Canada, more than 17 years ago (1). Since then, it has been detected in two other locations: Pocatello Valley, ID (3), and across the border in Utah. BaYSMV has now been found in the Alaskan interior. In July 1999, dry-land barley (Hordeum vulgare L.) growing in University of Alaska-Fairbanks experimental plots exhibited symptoms similar to those described for BaYSMV, including parallel chlorotic streaks and leaf banding. Mechanical inoculation of Nicotiana benthamiana with diseased barley sap produced systemic mosaic symptoms. As previously reported for BaYSMV sap-transmission tests (2), parallel inoculations to barley plants yielded no symptoms. Electron microscopy of leaf dips and minipurifications of infected N. benthamiana revealed long filamentous particles that matched the size and shape reported for BaYSMV (1). Ultrathin sections of diseased barley and N. benthamiana leaves displayed characteristic virus particles. BaYSMV was confirmed by immuno-sorbent electron microscopy assays (4) and western blot analysis with polyclonal antiserum. Long filamentous BaYSMV particles appeared only on grids coated with BaYSMV antiserum and exposed to diseased N. benthamiana sap. Total protein extracts from diseased barley tissue and inoculated N. benthamiana, as well as with protein extracted from partially purified preparations, were applied to a 12% sodium dodecyl sulfate-polyacrylamide gel electrophoresis minigel and stained with Coomassie blue. Diseased samples, but not healthy controls, contained a protein of ≈33 kDa that was within the size range of a previously described protein from partially purified BaYSMV particles (2). Western blot analysis with an Immuno-Blot alkaline phosphatase assay system (Bio-Rad Laboratories, Hercules, CA) confirmed that the protein reacted with polyclonal BaYSMV. This is the first serological documentation of a BaYSMV-specific protein and that the ≈33-kDa protein is the main antigen recognized by the BaYSMV polyclonal antiserum. Based on virus particle shape and size, symptomology, mechanical transmission host range, and serology, we conclude that BaYSMV is associated with the barley disease observed. Barley yellow streak mosaic virus disease outbreaks are associated with recurring drought and are accompanied by infestations of the brown wheat mite vector, Petrobia latens Müller (1), so it is not surprising that this report coincides with abnormally dry conditions occurring throughout the 1990s in the interior of Alaska.

References: (1) N. L. Robertson and T. W. Carroll. Science 240:1188, 1988. (2) N. L. Robertson and T. W. Carroll. Plant Dis. 75:839, 1991. (3) J. S. Skaf et al. Plant Dis. 76:861, 1992. (4) J. S. Skaf and T. W. Carroll. Plant Dis. 79:1003, 1995.
First Report of Pestalotiopsis populi-nigrae on Poplar in North America
Authors: Newcombe G.
Published: May 2007

Black acervuli were observed on abaxial surfaces of leaves of hybrid poplar (Populus trichocarpa Torr. & A. Gray × P. deltoides Marsh.) collected during fall 1998 in western Washington. Melampsora uredinia also were present but may be coincidental. When incubated in a moist petri dish, leaves became necrotic, and acervuli produced black masses of fivecelled, appendage-bearing conidia. Average conidia length was 25 µm. Three median versicolorous cells averaged 17.5 µm long and 6 µm wide; the upper two were darker than the lower one. There were typically three apical setulae, averaging 20 µm long. The average basal pedicel was 5 µm long. The fungus fits the description of Pestalotiopsis populi-nigrae (Sawada et Ito) Morelet. Originally described as an opportunistic pathogen on poplar in Japan (1), P. populi-nigrae was subsequently found on poplar in Europe (2). It is also the cause of cane blight of Rosa spp. in Japan (2), but it has never been reported in North America. A specimen has been deposited in the U.S. National Fungus Collections (BPI 746460). I did not observe P. populi-nigrae in 1997 to 1999 collections of rusted poplar leaves from the Southeast, western Kentucky, Minnesota, and Iowa nor in other Pacific Northwest collections. This was not a comprehensive survey for P. populi-nigrae but may indicate that the fungus is rare in North America. It also is possible that BPI 746460 represents an undescribed, uncommon species native to North America that is morphologically indistinguishable from P. populi-nigrae. Further research is required to test this hypothesis.

References: (1) K. Ito. Bull. Gov. For. Exp. Stn. 45:135, 1950. (2) E. Kimishima et al. Ann. Phytopathol. Soc. Jpn. 62:502, 1996.
First Report of Colletotrichum gloeosporioides on Strawberry in Northwestern Argentina
Authors: Mónaco M. E. , Salazar S. M. , Aprea A. , Ricci J. C. Díaz , Zembo J. C. , Castagnaro A.
Published: May 2007

Colletotrichum gloeosporioides was isolated from symptomatic strawberry (Fragaria × ananassa Duch. ‘Chandler’) growing in Lules (Tucumán, Argentina). Isolates were characterized based on several criteria. Potato dextrose agar (PDA) was used to evaluate cultural and morphological characteristics of the isolates. After 10 days on PDA at 28°C under continuous white light, colonies showed abundant aerial, cottony white to pale beige growth, with orange asexual fruiting bodies in older colonies. Isolates displayed cylindrical conidia, rounded at both ends, averaging 10.4 × 3.9 µm (length by width). A sexual phase (perithecia) was observed in all isolates in 2-month-old cultures on PDA at 28°C under continuous white light. Pathogenicity tests were conducted with healthy plants of cvs. Pájaro and Chandler. Spray inoculation with conidial suspensions (106 conidia per ml) resulted in disease symptoms (petiole and crown lesions with wilting of crown-infected plants) 7 days after inoculation. Infection progressed at a higher rate in Pájaro than in Chandler. Reisolations from infected strawberry lesions yielded isolates with characteristics identical to the isolate used to inoculate the host. Based on morphological and cultural characteristics, isolates were identified as C. gloeosporioides Penz. & Sacc. (teleomorph Glomerella cingulata Spauld & H. Schenk) (1). This is the first report of C. gloeosporioides causing strawberry anthracnose in northwestern Argentina.

Reference: (1) P. S. Gunnell and W. D. Gubler. Mycol. 84:157, 1992.
Outbreak of Smut Caused by Tilletia maclaganii on Cultivated Switchgrass in Iowa
Authors: Gravert C. E. , Tiffany L. H. , Munkvold G. P.
Published: May 2007

Switchgrass (Panicum virgatum L.), a prairie grass native to Iowa, is cultivated for forage and biomass production. During the late 1990s, biomass and seed yields of switchgrass grown in southern Iowa began to decline, and the reduction has been attributed to unidentified diseases. In 1999, many plants in previously low-yielding fields were stunted and flowered prematurely. Glumes had an uncharacteristic purple pigmentation, and seeds had been replaced by fungal spores. A smut fungus identified as Tilletia maclaganii (Berk.) G.P. Clinton (1) was associated consistently with fields that yielded poorly. Teliospores were red-orange when immature and turned dark brown as they matured. Teliospores were globose to slightly irregular, ≈18 to 25 µm in diameter, finely verrucose, with a thick exospore. True sterile cells also were present. T. maclaganii infects switchgrass and has been reported previously in Iowa (2), although it is found only occasionally on the state's native switchgrass. The prevalence and incidence of disease was surveyed in late August 1999. A weighted random sampling procedure was used to select switchgrass production fields from 60 fields involved in the Chariton Valley Biomass Project. Fields were located in Appanoose, Lucas, Monroe, and Wayne counties in southern Iowa. The sampling procedure was designed so the probability of each field being chosen was proportional to its area. This resulted in samples being taken from 17 fields representing ≈50% of the total area of the 60 fields. All sampled fields were planted with the predominant cultivar, Cave-in-Rock. In each field, five 1-m2 samples (≈60 to 250 tillers) were taken from arbitrary points. The incidence of smut (percentage of tillers with smut) was calculated for each sample. Smut was found in 15 of 17 fields. We estimated that 50 to 82% of the area in switchgrass production in these counties was infested with T. maclaganii. The mean incidence of smut was estimated at 10.1% of all tillers in the area. Incidence in individual fields ranged from 0 to 70%. Fields with incidence >50% yielded less than half of the expected biomass. Some infested seed-production fields were a total loss in 1999. This disease presents a serious threat to the cultivation of switchgrass for biomass production in southern Iowa. The disease cycle for T. maclaganii is poorly documented, but because switchgrass is a perennial species, it is likely that affected fields will have recurring epidemics. Susceptibility of other cultivars is unknown but needs to be investigated.

References: (1) G. W. Fischer. 1953. Manual of the North American Smut Fungi. Ronald Press, NY. (2) J. C. Gilman and W. A. Archer. The fungi of Iowa parasitic on plants. Iowa State College J. Sci. 3:299, 1929.
Effects of Gypsum on Zoospores and Sporangia of Phytophthora cinnamomi in Field Soil
Authors: Messenger B. J. , Menge J. A. , Pond E.
Published: May 2007

Sporangial production of Phytophthora cinnamomi buried in gypsum-amended avocado soil for 2 days was reduced by as much as 74% in greenhouse trials. P. cinnamomi sporangial volume was reduced an average of 64% in gypsum-amended soil. Soil extracts from gypsum-amended soil reduced in vitro sporangial production and volume. Irrigation with gypsum solutions of buried mycelium in unamended soil also reduced sporangial production and volume. Zoospore production and colony-forming units of P. cinnamomi were reduced in soil amended with calcium sulfate, calcium nitrate, or calcium carbonate. Zoospore encystment or passive movement through soil was not significantly affected by gypsum soil amendments.
Environmental Factors Affecting the Severity of Alternaria Brown Spot of Citrus and Their Potential Use in Timing Fungicide Applications
Authors: Timmer L. W. , Darhower H. M. , Zitko S. E. , Peever T. L. , Ibáñez A. M. , Bushong P. M.
Published: May 2007

Alternaria brown spot affects many tangerines and their hybrids, causing lesions on leaves, twigs, and fruit resulting in reduced yield and fruit quality. Field studies were conducted in a severely affected Minneola tangelo grove in central Florida from 1996 to 1998 to determine the environmental factors associated with infection of field trees and potted trap plants. Conidial production peaked following large flushes of new leaves, which were heavily infected. Most infections occurred during the summer rainy season, but trap plants became infected nearly every week of the year. When plants were exposed for 1-week periods, linear regression analysis indicated that disease severity on trap plants was positively related to the amount of rainfall, duration of leaf wetness, and average daily temperatures, and negatively related to the number of conidia trapped. Similar relationships occurred with trap plants exposed for 24-h periods on 141 different dates, except that temperature was not a significant factor. Nevertheless, these factors individually or combined in stepwise multiple regressions explained only a low percentage of the variability in disease severity with both weekly and daily trap plant sampling. When daily environmental data were categorized as: (i) rain versus no rain, (ii) <10 h or >10 h leaf wetness duration, and (iii) average temperature <20°C, 20 to 28°C, and >28°C, relationships to disease severity on trap plants were clearer. Disease severity on days with rain was nearly double that of days without rain, but considerable infection occurred on days with >10 h leaf wetness duration and no rain. Infection was greatest on days with temperatures of 20 to 28°C and slightly less at lower or higher temperatures. A point system, called the ALTER-RATER, was designed whereby each day would be assigned a severity value according to the prevailing environmental conditions. A fungicide application would be made after a predetermined number of points had accumulated. Simulated spray programs based on accumulation of 50, 75, 100, and 150 points from historical weather data at several locations indicated that from 8 to 15, 6 to 8, 5 to 6, or 3 to 4 sprays, respectively, would be needed depending on year and location in Florida. Such a weather-based control system could reduce the number of fungicide applications and improve control of Alternaria brown spot of tangerine.
Proficiency Testing in a Laboratory Accreditation Program for the Bacterial Ring Rot Pathogen of Potato
Authors: De Boer S. H. , Hall J. W.
Published: May 2007

Variability of enzyme-linked immunosorbent assay (ELISA) and immunofluorescence tests for the detection of Clavibacter michiganensis subsp. sepedonicus in potato tissue was analyzed to determine the magnitude of repeatability (within analyst variation) and reproducibility (among analyst variation) components. The analysis was based on data generated by analysts in eight laboratories testing proficiency panel samples distributed under a laboratory accreditation program. The standard deviation for repeatability of the ELISA test was small but increased at higher absorbance readings, while the standard deviation for reproducibility was larger and also increased at high absorbances. For immunofluorescence, the standard deviation for repeatability and reproducibility were similar to one another and increased with increasing bacterial concentration, as might be expected for count data and the inherent subjectivity of the test. The reproducibility standard deviation provided the basis for calculating “z-scores” by the Association of Official Analytical Chemists' procedure to evaluate proficiency of chemical analyses. More than 90 and 80% of the z-scores for samples tested in this study by ELISA and immunofluorescence, respectively, were in the acceptable range. The rescaled sums of z-scores for individual analysts were used as single combination scores to evaluate each analyst's results over all samples of a proficiency panel. This measure may be useful for tracking analyst performance on process control charts as part of a quality control system.
Biosynthesis of Deoxynivalenol in Spikelets of Barley Inoculated with Macroconidia of Fusarium graminearum
Authors: Evans C. K. , Xie W. , Dill-Macky R. , Mirocha C. J.
Published: May 2007

This research examined the biosynthesis of deoxynivalenol (DON) and 15-acetyldeoxynivalenol (15-ADON) in barley spikelets inoculated with macroconidia of Fusarium graminearum (Group-II). Investigations were conducted to determine if these toxins were present in macroconidia of the pathogen prior to inoculating barley spikelets. Extracts of macroconidia cultured from mung bean agar were analyzed using gas chromatography-mass spectrometry. Neither DON or 15-ADON was detected in three isolates' macroconidia when compared with macroconidia-DON-matrix standards adjusted to 100, 200, 300, and 400 ng/g with a detection limit of 100 ng/g. Mean recovery of DON that was added to macroconidia was 89.5%. The same isolates were pathogenic on barley cultivars Robust (moderately susceptible) and Chevron (moderately resistant) and produced DON (0 to 3.69 ng/g) and 15-ADON (detected but not quantified) when grown in rice culture. Greenhouse experiments were performed to determine when DON and 15-ADON were detectable after inoculation and to quantify their amount in inoculated barley spikelets. The three isolates of F. graminearum were separately inoculated to a central spikelet on heads of barley cultivars Robust and Chevron. Both toxins were detected in spikelets 48 h postinoculation (PI). DON increased dramatically after 72 h and did not diminish thereafter. Accumulation of 15-ADON peaked at 72 to 120 h and decreased by 240 h PI. There were no statistical differences between cultivars or among fungal isolates for accumulation of either toxin when averaged over the time intervals. Differences of toxin accumulation at each sampling interval were significant (P < 0.0001) when averaged over isolates and cultivars. Spikelets of six cultivars and lines were sampled at inoculation and 18, 36, 54, 72, and 90 h PI. DON and 15-ADON were detected at 36 h PI, but differences among the cultivars and lines were not significant. Yield of DON in inoculated spikelets of 31 barley cultivars and lines at 72 h PI ranged from 0.14 to 1.26 μg per spikelet, and differences among the cultivars and lines were significant (P < 0.002). The data demonstrate a useful range of variability for toxin accumulation in inoculated spikelets among germ plasm in the Minnesota breeding program. Macroconidia with no detectable DON or 15-ADON could be used for in vitro studies of toxin biosynthesis. Establishing when DON and 15-ADON are synthesized facilitates studying the effects of promising fungicides, biocontrol organisms, and new or novel genetic resistance mechanisms and if or how they may prevent or delay the biosynthesis of toxins.
Incidence of Phytophthora Root Rot of Fraser Fir in North Carolina and Sensitivity of Isolates of Phytophthora cinnamomi to Metalaxyl
Authors: Benson D. M. , Grand L. F.
Published: May 2007

A survey of Fraser fir Christmas trees in North Carolina for incidence of Phytophthora root rot was conducted during 1997 and 1998. Field sites (7- to 13-year-old trees) and nursery transplant beds (4- to 5-year-old trees) selected at random were surveyed based on foliar symptoms of Phytophthora root rot. Field sites were surveyed with a random transect method (>3,000 trees/field) or by counting all trees (<3,000 trees/field). Overall, incidence of Phytophthora root rot averaged 9% over the 58 field sites sampled, with a range of 0 to 75%. No relationship was found between number of years Fraser fir had been planted in the field site and disease incidence. Disease incidence did not increase as field sites were rotated through second or third crops of Fraser fir. Phytophthora spp. were recovered from 1.8% of asymptomatic trees sampled from 58 field sites across the state. P. cinnamomi accounted for 91% of the Phytophthora isolates recovered. In nursery transplant beds where a systematic sampling procedure was used, incidence of diseased trees averaged 2%, with a range of 0 to 12% across 16 locations. Recovery of Phytophthora spp. averaged 1.2% from root samples collected from 50 asymptomatic seedlings at each location. Isolates collected from the field and nursery transplant beds were grown on cornmeal agar incorporated with 0, 1, 1.25, 10, or 100 μg a.i. metalaxyl/ml. All 166 isolates of P. cinnamomi tested were sensitive to metalaxyl at 1 or 1.25 μg a.i. metalaxyl/ml. Although incidence of Phytophthora root rot has not increased in the state compared to a survey done in 1976 to 1977, the disease continues to limit production of Fraser fir in North Carolina.
Influence of Soil Saturation and Temperature on Erwinia chrysanthemi Soft Rot of Carrot
Authors: Farrar J. J. , Nunez J. J. , Davis R. M.
Published: May 2007

In 1998, soft rot caused by Erwinia chrysanthemi resulted in an estimated loss of 1,800 tons of carrots in California. The disease appeared to be related to unusually high temperatures and excessive irrigation. To determine the optimum conditions for development of soft rot under controlled conditions, pots of carrots inoculated with E. chrysanthemi were saturated with water and incubated at 20, 25, 30, or 35°C. Plants were harvested and examined for disease 12, 24, 36, 48, 72, and 96 h after inoculation. Negligible disease occurred after 12 h. Disease severity and incidence increased with increasing temperature and duration of saturation from 24 to 96 h. In a second experiment, carrot disks were inoculated with three isolates each of E. chrysanthemi and E. carotovora subsp. carotovora and incubated at 15, 20, 25, 30, and 35°C. After 48 h, the disks were washed to remove rotted tissue and reweighed. Neither bacterium reduced carrot disk weight at 15°C. In general, moderate weight reduction occurred at 20 and 25°C. The greatest degree of soft rot was caused by E. chrysanthemi at 30 and 35°C. E. carotovora subsp. carotovora isolates were relatively less virulent than E. chrysanthemi at 30°C and none of the E. carotovora subsp. carotovora isolates reduced carrot disk weight at 35°C. This is the first report of E. chrysanthemi causing soft rot of carrot in California. Based on these results, growers should limit the length of time carrot roots are exposed to saturated soil, especially at high soil temperatures.