bluuebunny/crossref_metadata_2025 huggingface dataset:
First Report of an Isolate of Pelargonium zonate spot virus in Commercial Glasshouse Tomato Crops in Southeastern France
Authors: Gebre-Selassie K. , Delecolle B. , Gognalons P. , Dufour O. , Gros C. , Cotillon A. C. , Parrella G. , Marchoux G.
Published: May 2007

In summer 2000, symptoms similar to Pelargonium zonate spot virus (PZSV) were observed for the first time on tomato plants in southeastern France. The plants were from commercial glasshouse fresh-market crops. Symptoms observed were chlorotic mottling with bright yellow distinct rings on leaves and curved line patterns on stems. Fruit symptoms included chlorotic and necrotic spotting, marked concentric ring patterns, and distortions. Diagnosis was made from symptomatic leaves and fruits by mechanical inoculation on a set of host plants. Local chlorotic and necrotic lesions were observed on Chenopodium amaranticolor, C. quinoa, Cucumis sativus cv. Marketer, Cucumis melo cv. Vedrantais, Phaseolus vulgaris cv. Pinto, Vicia faba cv. D'Aguadulce, Vigna unguiculata cv. Black Eye, and systemic symptoms were observed on Capsicum annuum cvs. Yolo Wonder, Yolo Y, Florida VR2, and Criollo de Morelos 334, Datura stramonium, Lycopersicon esculentum cvs. Momor and Stevens, L. hirsutum (PI 134417 and PI 247087), Nicotiana benthamiana, N. clevelandii, N. tabacum cv. Xanthi nc, Ocimum basilicum cv. Latino, Petunia hybrida cv. Rose du ciel, and Physalis floridana. No reaction was observed on Pisum sativum cv. Douce Provence, Salvia splendens cv. Etna, or Zinnia elegans cv. Liliput. Symptoms on tomato of PZSV, Parietaria mottle virus (PMoV), and Tomato spotted wilt virus (TSWV) are similar, particularly those elicited in fruits. Therefore, the field samples were checked using double-antibody sandwich enzyme-linked immunosorbent assay against antisera of the type-strain of PZSV and tomato strain of PMoV and their homologous antigenes, which were supplied by D. Gallitelli and P. Roggero respectively, and our antiserum of TSWV. Electron microscopy of negatively stained preparations from leaves of tomato and D. stramonium showed that the sap contained very few paraspheric shaped particles, 26 to 29 nm in diameter. Three isolates collected from two different regions (Vaucluse and Bouches du Rhône) showed a very close serological relationship with the Italian type-strain of PZSV and tested negative against antisera of PMoV and TSWV. The French isolates were biologically different from the type-strain, but were similar to the Spanish strain of PZSV because they infected D. stramonium, N. benthamiana, O. basilicum, and V. unguiculata (2). Moreover, in transverse tissue sections, virions were not observed in the nucleus and tubular structures, unlike the Italian isolates, (1) but were present in the cytoplasm and particularly in the mesophyll cells. There are only a few records of the occurrence and distribution of PZSV in Mediterranean countries.

References: (1) M. A Castellano and G. P Martelli. Phytopathol. Mediterr. 20:64, 1981. (2) M. Luis-Arteaga. Plant Dis. 84:807, 2000.
Growth and Nutrition of Mollicute-Infected Maize
Authors: de Oliveira Elizabeth , Magalhães Paulo C. , Gomide Reinaldo L. , Vasconcelos Carlos A. , Souza Isabel R. P. , Oliveira Charles M. , Cruz Ivan , Schaffert Robert E.
Published: May 2007

Maize bushy stunt phytoplasma (MBSP) and corn stunt spiroplasma (CSS) diseases are widespread in Brazil. The leafhopper Dalbulus maidis is the insect vector for these pathogenic mollicutes. The effects of these diseases on the development of maize plants and the possible interaction of soil water availability on these effects were evaluated in two experiments carried out on potted plants. Experiment 1 was carried out in a 2 × 4 factorial, where factor 1 corresponded to healthy and mollicute-infected plants and factor 2 to the maintenance of 40, 60, 80, and 100% of the total soil water availability. Leafhoppers collected from a field with high incidence of these diseases were used to inoculate plants with mollicutes. There were three treatments in experiment 2: healthy plants, plants infected with phytoplasma, and plants infected with spiroplasma. MBSP was predominant in experiment 1. The infected plants grew less and lowered nutrient uptake, in distinct proportions, indicating a differential effect of mollicutes on nutrient uptake independent of available soil water. Soil water availability did not significantly affect plant growth and nutrient uptake or mollicute infection. The results indicated that plants infected by mollicutes contained less protein than healthy plants. Experiment 2 showed a reduction in growth of plants infected with mollicutes and less nutrient uptake by spiroplasma-infected plants. The results showed a detrimental effect of the spiroplasma on Mg uptake. Both experiments showed more water retention by infected plants than by healthy ones. These experiments clearly demonstrated that reduced plant growth and nutrient uptake are major effects on plants infected with MBSP and CSS.
First Report of Sweet potato leaf curl virus in Peru
Authors: Fuentes S. , Salazar L. F.
Published: May 2007

Leaf curling symptoms have been reported in sweet potato (Ipomoea batatas) plants infected with a geminivirus (1). Leaf curl disease appeared in Peru after the 1997 to 1998 El Niño, when the population and activity of whiteflies (Bemisia tabaci, B. argentifolii, and B. afer) increased. Approximately 6% of plants in farmers' commercial fields in San Ramón, Junín (September 2000) and Cañete, Lima (February 2001) showed typical leaf curling symptoms. Seventeen plants in total were collected from both places, and stem scions from those plants were graft-inoculated to I. setosa, which developed symptoms of leaf curling, interveinal chlorosis, and stunting. Total nucleic acid was obtained from infected sweet potato and I. setosa plants using cetyltrimethylammoniumbromide (CTAB) extraction, and primers PW285-3 (5′-CGT CGT TAG CAG TCT GCA GGC CTC CTC TAG-3′) and PW285-4 (5′ -AAC TGT AAA TAC GGA ACT GCA GTT CGA ATT-3′) for Sweet potato leaf curl virus (SPLCV), developed and provided by R. Valverde and C. Clark of Louisiana State University (2), were used to amplify SPLCV by polymerase chain reaction (PCR). Expected DNA fragments of ca. 900 bp (in all samples) and 2.4 kp (in some samples), characteristic of the subgenomic and genomic DNAs of SPLCV respectively, were obtained from symptomatic but not from symptomless (uninfected) plants. This 2.4-kb fragment was amplified in relatively small amounts compared to the 900-bp fragment. Presence of SPLCV was also confirmed by nucleic acid spot hybridization using a full-length clone of SPLCV-US. Fourteen of 17 plants infected with SPLCV were also infected with Sweet potato chlorotic stunt virus (determined by nitrocellulose membrane enzyme-linked immunosorbent assay serological test), which is also transmitted by whiteflies. These viruses now seem to be common in farmers' fields in San Ramón and Cañete. To our knowledge, this is the first report of SPLCV in Peru.

References: (1) P. Lotrakul et al. Plant Dis. 82:1253, 1998. (2) P. Lotrakul and R. A. Valverde. Cloning of a DNA-A like genomic component of sweet potato leaf curl virus: nucleotide sequence and phylogenetic relationships. Molecular Plant Pathology On-Line ( http://www.bspp.org.uk/mppol/1999/0422lotrakul/paper.htm ), 1999.
PCR and DNA Hybridization Methods for Specific Detection of Bean-Infecting Begomoviruses in the Americas and Caribbean
Authors: Potter J. L. , Nakhla M. K. , Mejía L. , Maxwell D. P.
Published: May 2007

Begomoviruses are a major problem for common bean production in the tropics and subtropics of the Americas and the Caribbean. Multiplex polymerase chain reaction (PCR) primer pairs and nucleic acid hybridization probes have been developed to differentiate five bean-infecting begomoviruses and were used to assay reference and field-collected bean samples from Florida, Mexico, Central America, the Caribbean, and Brazil. Bean golden mosaic virus was found in Brazil, Bean calico mosaic virus in Mexico, and Bean golden yellow mosaic virus in Central America, the Caribbean, and Florida. Bean dwarf mosaic virus was not detected in any of the field samples. Tomato yellow leaf curl virus was found only in tomato samples from the Caribbean. These detection methods will provide tools to assist in the understanding of the epidemiology and diversity of geminiviruses as well as to facilitate resistance breeding, cultivar selection, and development of strategies for control.
Effects of Sequential Calcium Chloride, Ziram, and Yeast Orchard Sprays on Postharvest Decay of Pear
Authors: Sugar D. , Benbow J. M. , Powers K. A. , Basile S. R.
Published: May 2007

The most effective nutritional, fungicidal, and biological control treatments previously evaluated for control of postharvest decay in pear were evaluated for 3 years as factorial treatments to determine the best combinations for an integrated program. Calcium chloride sprays during the growing season reduced incidence of side rot in each year and of blue mold in 1 year, while ziram was effective against side rot in 1 year and blue mold in 2 years. Ziram, but not calcium chloride, provided control of gray mold and bull's-eye rot. Application of the yeast Cryptococcus infirmominiatus to pear fruit 1 week before harvest at a concentration of 1.0 to 1.5 × 108 CFU/ml resulted in establishment of large populations of yeast on fruit surfaces, but did not reduce postharvest fungal decay incidence in 3 years of testing. In 1 year, ziram sprays applied 2 weeks before harvest significantly reduced yeast populations on fruit subsequently treated with C. infirmo-miniatus. Sequential treatments with calcium chloride and ziram are indicated in an integrated program to take advantage of their differential effectiveness to broaden the range of control of pear postharvest decay pathogens.
First Report of Infection of Bermudagrass by Bipolaris sorokiniana in the Southeastern United States
Authors: Pratt R. G.
Published: May 2007

Bipolaris sorokiniana (Sacc.) Shoemaker is a major foliar and root-infecting pathogen of cool-season forage and turf grasses and small grains in the southeastern United States (2). In North America, B. sorokiniana has been reported from bermudagrass (Cynodon dactylon [L.] Pers.) once in California in 1961 (1), and rarely from other warm-season grasses in the southeastern United States. In May, July, September, and October 2002, B. sorokiniana sporulation was observed on leaves of common bermudagrass exhibiting necrotic lesions and dieback in waste application fields on three commercial swine farms in Chickasaw, Lowndes, and Webster counties, MS. Leaves were collected (50 per farm per month), surface-disinfested, plated on water agar, and observed for fungal sporulation on leaf surfaces after 7 to 10 days (3,4). The pathogen was detected on 1 to 3 farms each month in leaves that were infected with numerous other dematiaceous hyphomycetes (3,4). Three randomly selected single-spore isolates of B. sorokiniana from each of bermudagrass and annual ryegrass (Lolium multiflorum Lam.), collected at the Webster County farm, were compared for select features of morphology and pathogenicity on bermudagrass. Isolates differed significantly in growth rates, amount of sporulation, and spore sizes on cornmeal agar, but differences were not consistently related to hosts of origin. In plants inoculated by atomizing equal quantities of spores (2.8 × 104/ml) onto foliage, isolates of B. sorokiniana from bermudagrass and ryegrass both caused significantly (P = 0.05) more severe foliar necrosis after 10 days than B. cynodontis (5 pots of seeded plants per treatment in each of two experiments). B. sorokiniana was reisolated from disinfested, symptomatic bermudagrass leaf tissue following inoculations. To our knowledge, this is the first report of B. sorokiniana on bermudagrass in North America outside of California (1) and indicates that this pathogen is highly virulent on bermudagrass in the southeastern United States (3,4). Of potentially greater importance is the fact that one of the most common and widespread forage and turf grass species in the southeastern United States can serve as an alternate host for maintenance and increase of inoculum of B. sorokiniana during summer months.

References: (1) R. M. Endo. Plant Dis. Rep. 45:869, 1961. (2) D. F. Farr et al. Fungal Databases. Systematic Botany and Mycology Laboratory, On-line publication. ARS, USDA, 2003. (3) R. G. Pratt. Agron. J. 92:512, 2000. (4) R. G. Pratt. Plant Dis. 85:1206, 2001.
Regional Frequencies of Virulence in Oat Crown Rust in the United States from 1990 Through 2000
Authors: Leonard K. J.
Published: May 2007

More than 2,000 isolates of Puccinia coronata f. sp. avenae collected in national virulence surveys were analyzed to determine regional patterns of virulence on 28 single-gene oat lines. From 1990 to 2000, frequencies of virulence to eight differentials increased significantly in Texas, and virulence frequencies of four of the eight also increased in the northern Great Plains. No significant changes occurred for the other 20 differentials. Isolates from northern states from the Dakotas to New York had similar patterns of virulence frequencies on these 20 differentials. The pattern of virulence frequencies in the north differed from that of southern states from Texas to the Carolinas. There was a gradient of similarity values in state by state comparisons from Texas to the Atlantic Coast. Isolates from California were distinctly different from those elsewhere in the United States. Isolates from the South and from California had greater mean virulence complexity than isolates from northern states. Collections from the central Great Plains were intermediate between northern and southern isolates. Uredinial isolates from oat and aecial isolates from the alternate host Rhamnus cathartica in Minnesota had similar frequencies of virulence, as did isolates from cultivated oat and wild Avena fatua in North Dakota. Maintenance of large numbers of stable virulence polymorphisms with different regional allele frequencies is consistent with the operation of some form of stabilizing selection.
Near-Harvest Applications ofMetschnikowia fructicola, Ethanol, and Sodium Bicarbonate to Control Postharvest Diseases of Grape in Central California
Authors: Karabulut Ozgur Akgun , Smilanick Joseph L. , Gabler Franka Mlikota , Mansour Monir , Droby Samir
Published: May 2007

The yeast Metschnikowia fructicola, ethanol, and sodium bicarbonate (SBC), alone or in combinations, were applied to table grapes on vines 24 h before harvest to control the incidence of postharvest diseases. In four experiments, all significantly reduced the total number of decayed berries caused by Botrytis cinerea, Alternaria spp., or Aspergillus niger after storage for 30 days at 1°C followed by 2 days at 20°C. In three experiments, a mean gray mold incidence (caused by B. cinerea) of 34.2 infected berries per kilogram among untreated grape was reduced by Metschnikowia fructicola at 2 × 107CFU/ml, ethanol at 50% (vol/vol), or SBC at 2% (wt/vol) to 12.9, 8.1, or 10.6 infected berries per kilogram, respectively. Ethanol, SBC, and SO2generator pads were similarly effective. M. fructicola effectiveness was not improved when combined with ethanol or SBC treatments. Ethanol and yeast treatments did not harm the appearance of the grapes. M. fructicola and SBC left noticeable residues, and SBC caused some visible phytotoxicity to the rachis and berries. Ethanol applied at 50% (vol/vol) reduced epiphytic fungal and bacterial populations by about 50% compared with controls. M. fructicola populations persisted on berries during storage when applied alone or after ethanol treatments, whereas SBC reduced its population significantly.
Durability of Field Resistance to Black Pod Disease of Cacao in Papua New Guinea
Authors: Saul-Maora J. , Namaliu Y. , Cilas C. , Blaha G.
Published: May 2007

Black pod disease of cacao, caused by various species of Phytophthora, is one of the most serious causes of cacao yield losses worldwide. In Papua New Guinea, such losses on local smallholdings are estimated at more than 40% of annual production. Genetic improvement of cacao resistance is the most promising way of reducing the impact of these pathogens. Field infection of 25 selected Trinitario × Upper Amazonian hybrid progenies in a factorial design (5 by 5) was monitored for five consecutive years at the Cocoa and Coconut Research Institute in Papua New Guinea. The resistance durability of the various hybrids was analyzed using a factorial split-plot model with years as the main factor. The reaction of the hybrid progenies remained stable and similar throughout the 5 years. Similarly, the general combining ability ranking of the parents was also the same for each year. Moreover, data accumulated over several years provided a clearer distinction between the parents. The analyses clearly showed female inheritance under field conditions, and the progenies from what are believed to be resistant females showed good resistance.
Soil Fumigant Effects on Three Genera of Potential Soilborne Pathogenic Fungi and Their Effect on Potato Yield in the Columbia Basin of Oregon
Authors: Hamm Philip B. , Ingham Russell E. , Jaeger Joy R. , Swanson William H. , Volker Kurt C.
Published: May 2007

During three years of trials in commercial production fields, populations of three genera of potato pathogens, Fusarium spp, Pythium spp, and Verticillium dahliae, were followed before and after the single or combination use of 1,3-dichloropropene (1,3-D), 1,3-D + 17% chloropicrin (1,3-D + chloropicrin), or metam sodium (MS). Populations of these fungi did not always increase during the growing season but the relative population at a soil depth of 0 to 30 cm was nearly always higher than at 30 to 60 cm, regardless of year, sampling time, or fungal pathogen. The use of MS alone or in combination with 1,3-D generally suppressed recovery of all three genera and also increased yields. 1,3-D or 1,3-D + chloropicrin did not reduce fungal populations, but 1,3-D increased yield in 1 of 3 years. Reduced rates of MS and 1,3-D used in combination were as effective as higher rates of MS used alone. Multiple regression analysis comparing yield with fungal populations before planting indicated that population size was correlated negatively with yield. Propagules of V. dahliae had the greatest impact in reducing yield, but propagules of Pythium spp. and Fusarium spp. may have been important when populations of V. dahliae were low. Soil populations of Fusarium spp. and Pythium spp. have not been reported previously to be associated with yield reductions in potato grown in the Columbia Basin. Threshold estimates suggested that yield of number one tubers was reduced by 1 metric ton/ha for each 0.6 to 3.0 V. dahliae CFU/g dry soil present at planting.
Resistance of Pre- and Post-epidemic Strains of Agaricus bisporus to Trichoderma aggressivum f. aggressivum
Authors: Chen X. , Ospina-Giraldo M. D. , Wilkinson V. , Royse D. J. , Romaine C. P.
Published: May 2007

Since the early 1990s, the epidemic of green mold on the cultivated mushroom Agaricus bisporus in North America has been caused by Trichoderma aggressivum f. aggressivum. The findings of earlier research suggested that the microevolutionary emergence of T. aggressivum f. aggressivum coincided with the onset of the epidemic. This hypothesis was tested further by determining the disease susceptibility of mushroom strains grown widely before the epidemic manifested. The results of complementary methods of analysis, which entailed a grain protection assay and cropping trials, established that two pre-epidemic strains were more susceptible to green mold than three post-epidemic strains being cultivated at the time of the epidemic. Thus, if T. aggressivum f. aggressivum had been present within cultivated mushrooms prior to the epidemic, it should have been detected. It still appears to be true that T. aggressivum f. aggressivum emerged during the 1990s in a manner that remains unclear.
Identification of Tomato mosaic virus Infection in Lisianthus in Taiwan
Authors: Jan F.-J. , Chen C.-C. , Hsu H. T.
Published: May 2007

In recent years, Lisianthus (Eustoma russellianum (Don.) Griseb) has become popular as potted plants and cut flowers in Taiwan. They are grown in the central and southern regions of the island. Since 1998, diseased plants with mosaic symptoms, followed by necrosis of leaf tissues, were observed in commercial greenhouses and field-grown lisianthus. Newly emergent leaves were curled and smaller compared with those on healthy plants. These symptoms greatly decreased the commercial value of the crop. Rigid rods similar to tobamoviruses that measured 300 × 18 nm were found consistently associated with symptomatic plants. In July 2002, a virus culture was isolated from diseased lisianthus from Chiayi County, Taiwan and established and maintained in systemic hosts Nicotiana tabacum L. and N. benthamiana Domin. Chlorotic and necrotic spots developed on lisianthus leaves 1 to 2 weeks after inoculation with the virus; symptoms eventually became systemic. Virions were purified from inoculated N. tabacum. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis showed that the virus contained one 18-kDa (Mr) polypeptide. The virus reacted positively in agar gel double diffusion tests and enzyme-linked immunosorbent assays with antisera prepared to Tobacco mosaic virus (TMV) or Tomato mosaic virus (ToMV) (gifts of S. D. Yeh, National Chung Hsing University, Taichung, Taiwan). A viral coat protein (CP) gene approximately 0.5 kb was amplified by reverse transcription-polymerase chain reaction from total RNA prepared from infected N. benthamiana using 5′-GCGAGCCATGGATTCTTACTCAATTACT as a forward primer and 5′-ACTCTCGGATCCTTAAGATGCAGGTGCAGA as a reverse primer. Comparison of the 480-nt CP gene region with that of ToMV-OM (GenBank Accession No. X02144) (3) revealed 99.2% nucleotide identity and 99.4% amino acid identity. It shares, however, 74.4% nucleotide identity and 83.9% amino acid identity with CP genes of TMV-U1 (GenBank Accession No. AX040174) and TMV-vulgare (GenBank Accession No. J02415) (1). The virus induced local lesion responses similar to ToMV on inoculated N. tabacum cv. White Burley, N. sylvestris Speg. & Comes, and Datura stramonium L. Inoculation of TMV, however, resulted in a systemic infection in these plants. Results from sequence analysis and diagnosis based on host reaction to the virus inoculation indicated that the tobamovirus infecting lisianthus in Taiwan is an isolate of ToMV. The virus is economically important to lisianthus and tomato in Taiwan. To our knowledge, this is the first report of ToMV causing disease on lisianthus in Taiwan. The disease was previously observed on lisianthus in Italy (2).

References: (1) P. Goelet et al. Proc. Natl. Acad. Sci. USA 79:5818, 1982. (2) V. Lisa and A. Gera. Lisianthus. Pages 443–448 in: Virus and Virus-like Diseases of Bulb and Flower Crops. G. Loebenstein et al. eds. John Wiley and Sons, West Sussex, U.K., 1995. (3) T. Ohno et al. J. Biochem. 96:1915, 1984.
First Report of Blight on Buxus spp. Caused by Cylindrocladium buxicola in Belgium
Authors: Crepel C. , Inghelbrecht S.
Published: May 2007

In the fall of 2000, a new blight disease was observed on Buxus spp. in private gardens in Belgium. Since then, more and similar disease samples from other Belgian sites, nurseries, and several garden centers have been received, indicating that this disease is spreading. Similar observations have been made in the U.K. and France, where the disease is widespread and losses are sometimes dramatic (1). Diseased plants have dark brown-to-black leaf spots and streaky, black stem lesions which lead, in some cases, to complete defoliation. On some infected plants new leaves grew in defoliated areas, hiding the original blight symptoms. Infection was mainly observed on Buxus sempervirens cv. Suffruticosa, but B. sempervirens cv. Latifolia raculata, B. microphylla cv. Compacta, and B. microphylla var. japonica cv. Faulkner were also infected. In the U.K., infections have additionally been reported on varieties of B. sempervirens, B. sinica, and B. microphylla (1). On the basis of observed symptoms and comparison of the symptoms with descriptions by Henricot and Culham (2), we identified that this new form of Buxus blight in Belgium is caused by Cylindrocladium buxicola. Sporulating cultures on potato dextrose agar (PDA) had macroconidiophores with stipe extensions terminating in broadly ellipsoidal vesicles with pointed or papillate apices (6.5 to 11 μm in diameter) and a penicillate arrangement of fertile branches each terminating in two to five phialides. Phialides produced clusters of cylindrical conidia (42 to 68 × 4 to 6 μm) that were rounded at both ends and had a single septum. Pathogenicity of the isolate was demonstrated by inoculation of healthy stems and leaves of four 3-year-old plants of B. sempervirens cv. Suffruticosa. On each plant, agar pieces of 1-week-old cultures grown on PDA were placed on five stems and five leaves that had been wounded with a sterile scalpel, then sealed with Parafilm. As a control, five wounded stems and leaves from another B. sempervirens cv. Suffruticosa plant were inoculated with sterile agar plugs. Inoculated plants were incubated in humid chambers (approximately 95% relative humidity) on the laboratory bench. Two weeks after inoculation, no symptoms were visible on the control plant. The inoculated plants showed symptoms as previously described, and C. buxicola was successfully reisolated from diseased tissue completing Koch's postulates. To our knowledge, this is the first record of C. buxicola on Buxus spp. in Belgium.

References: (1) B. Henricot et al. Plant Pathol. 49:805, 2000. (2) B. Henricot and A. Culham. Mycologia 94(6):980, 2002.
Weed Species as Hosts of Sclerotinia minor in Peanut Fields
Authors: Hollowell J. E. , Shew B. B. , Cubeta M. A. , Wilcut J. W.
Published: May 2007

Bleached stems and sclerotia were observed on winter annual weed species growing in harvested peanut fields in northeastern North Carolina in March 2001. Each field had a history of Sclerotinia blight caused by Sclerotinia minor. Symptomatic plants were collected and brought back to the laboratory for identification and isolation. S. minor was isolated and Koch's postulates were fulfilled to confirm pathogenicity of S. minor on nine weed species. They included Lamium aplexicaule (henbit), Cardamine parviflora (smallflowered bittercress), Stellaria media (common chickweed), Cerastium vulgatum (mouse-ear chickweed), Coronopus didymus (swinecress), Oenothera laciniata (cutleaf eveningprimrose), Conyza canadensis (horseweed), Brassica kaber (wild mustard), and Arabidopsis thaliana (mouse-ear cress). This is the first report of these species as hosts of S. minor in the natural environment. All isolates of S. minor obtained from the weed species were pathogenic to peanut.
Relationships Between Reactions of Sweet Corn Hybrids to Stewart's Wilt and Incidence of Systemic Infection by Erwinia stewartii
Authors: Michener P. M. , Freeman N. D. , Pataky J. K.
Published: May 2007

Relationships between the reactions of sweet corn hybrids to Stewart's wilt and the incidence of natural, systemic infection by Erwinia stewartii differed among trials in which the prevalence of Stewart's wilt differed. Systemic Stewart's wilt infection was assessed for 262, 296, and 245 hybrids planted in seven trials in central Illinois in June and July 1998, 1999, and 2000, respectively. Incidence of systemic infection was calculated in each trial for all hybrids in each of nine categories of Stewart's wilt reactions (i.e., 1 = resistant and 9 = susceptible). When mean incidence was about 5%, incidence ranged from about 1 to 8% on resistant to moderately susceptible hybrids, but incidence was nearly 30% on susceptible hybrids. When mean incidence ranged from 10 to 16%, the relationships between hybrid reactions and incidence were explained by exponential or polynomial regressions. Incidence was less than 10% for hybrids with resistant and moderately resistant reactions, and incidence was greater than 15% for moderately susceptible to susceptible hybrids. When mean incidence was near 50%, the relationship was linear. Incidence was about 18% for resistant hybrids and about 80% for susceptible hybrids. Incidence increased about 8% for each class of hybrid reaction from 1 to 9. The influence of resistance on the development of systemic infection at very early seedling growth stages also was evaluated in six greenhouse trials. A highly resistant hybrid, Bonus, was systemically infected in two of six greenhouse trials when seedlings were inoculated prior to the V3 growth stage; however, systemic infection was not as severe as on a susceptible hybrid, Jubilee. Systemic infection was more severe on Bonus when plants were inoculated at earlier growth stages between VE and V3. The resistant hybrid Bonus was not systemically infected when inoculated after the V4 growth stage except for one greenhouse trial when all Stewart's wilt ratings were higher than usual. Hybrid reactions to Stewart's wilt affected the incidence of systemic infection in field situations and they affected the growth stage at which resistance effectively prevented systemic movement of E. stewartii within plants in greenhouse trials. This information can be used to determine more effectively when to apply other control measures, such as insecticidal seed treatments.
Incidence of Viruses Infecting Winter Wheat in Alabama
Authors: Bowen Kira L. , Murphy John F. , Flanders Kathy L. , Mask Paul L. , Li Ruhui
Published: May 2007

The most important viral diseases of wheat are caused by Barley yellow dwarf virus (BYDV, strains PAV and MAV) and Cereal yellow dwarf virus (CYDV, strain RPV). Starting in 2000, winter wheat crops growing in northern, central, and southern Alabama were evaluated for the occurrence of BYDV-PAV and CYDV-RPV. In addition to these viruses, samples were tested for the presence of Soilborne wheat mosaic virus (SBWMV), Wheat spindle streak mosaic virus (WSSMV), and Wheat streak mosaic virus (WSMV). BYDV-PAV and CYDV-RPV were found throughout the state, alone or as co-infections, in 14.6% of the samples collected in 2000 and 12.2% of samples in 2001. PAV was found at a lower incidence than RPV (4.3 and 9.9%, respectively) in 2000; however, in 2001, PAV was detected in 8.2% and RPV in 1.9% of the samples. There was less rainfall than the 30-year average during the 1999-2000 growing season, and this may have contributed to differences in the relative incidence of PAV and RPV between the 2 years. SBWMV, WSSMV, and WSMV also were detected in Alabama in 2, 7.8, and 5.4% of the samples collected in 2000, respectively, and in 9.6, 34.3, and 18.5% of the samples collected in 2001, respectively. This is the first report of WSMV in Alabama winter wheat.
Effect of Partial Resistance on Phytophthora Stem Rot Incidence and Yield of Soybean in Ohio
Authors: Dorrance A. E. , McClure S. A. , St. Martin S. K.
Published: May 2007

Phytophthora root and stem rot of soybean commonly causes losses in both stand and yield in Ohio. Environmental conditions which favor the pathogen typically occur in many areas of the state during late spring and summer. This study examined the performance of 12 soybean cultivars with partial resistance, with or without Rps genes, to different populations of Phytophthora sojae and various levels of disease pressure. The soybean cultivars were evaluated in seven field environments with and without metalaxyl over 4 years. There was a highly significant genotype-environment interaction which was due in part to variable disease pressure. The incidence of Phytophthora stem rot in subplots ranged from 0 to 10 plants in the most susceptible cultivar, Sloan, while significantly less stem rot developed in cultivars with high levels of partial resistance or partial resistance combined with an Rps gene in three of the seven environments. Metalaxyl applied in-furrow had a significant effect on early and final plant populations as well as yield (P < 0.001) in two of the seven environments, and for yield (P = 0.05) in one environment. This indicates that at these two environments, 2001 Lakeview and VanBuren, early season Phytophthora disease was controlled with the in-furrow fungicide treatment. When diverse populations of P. sojae were present, yields from soybean cultivars with high levels of partial resistance were significantly higher than those with low levels of partial resistance. Soybean cultivars with specific resistance genes Rps1k, Rps1k + Rps6, or Rps1k +Rps3a had higher yields than plants with only partial resistance in environments where race determination indicated that the populations of P. sojae present were not capable of causing disease on plants with the Rps1k gene. However, in an environment with very low disease pressure, yields of soybean cultivars with partial resistance were not significantly different from those with single Rps genes or Rps gene combinations. These results demonstrate that genetic traits associated with high levels of partial resistance do not have a negative effect on yield. Soybean cultivars that had the most consistent ranking across environments were those with moderate levels of partial resistance in combination with either Rps1k or Rps3a.
First Report on White Smut of Gaillardia × grandiflora Caused by Entyloma polysporum in Virginia
Authors: Hong C. X. , Banko T. J.
Published: May 2007

Disease samples of Gaillardia × grandiflora cvs. Goblin and Baby Cole were received at the Hampton Roads Agricultural Research and Extension Center in Virginia Beach in early April 2002. Samples were from a nursery in eastern Virginia, and most diseased plants had several to more than a dozen, round, flat, white to tan spots with indistinct margins up to 1 cm in diameter on their leaves. The spots later turned brown and necrotic, followed by necrosis of the entire leaf. Leaves of ‘Baby Cole’ were beginning to wilt and were more spotted than those of ‘Goblin’. Fungal fruiting bodies were not observed on the surface of diseased leaves. However, microscopic examination of internal leaf tissues revealed masses of round, double-walled, pale green-to-yellow spores approximately 12 μm in diameter and typical of the ustilospores of Entyloma polysporum (2,3). Inoculum for pathogenicity tests was prepared by blending 10 diseased leaves in 200 ml of sterile distilled water (SDW) for 2 min in a blender at low speed. The spore suspension was adjusted to 5 × 105 spores per ml with SDW. Healthy ‘Goblin’ gaillardia plants were obtained from a nursery where smut symptoms had never been seen. Four plants in one-gallon containers were inoculated by spraying them to runoff with the spore suspension. Four control plants were sprayed with SDW only. All plants were maintained in a greenhouse (15 to 35°C) and covered with a clean polyethylene plastic sheet overnight (14 h) to maintain high humidity and separated to avoid potential cross contamination. Inoculated and uninoculated plants were hand-watered separately, with application of water to the foliage to enhance spread of the disease. Typical white smut symptoms were observed on inoculated plants 2 weeks after inoculation, and numerous spores of E. polysporum were observed in the diseased tissues. No disease symptoms were seen on control plants. White smut has been reported on gaillardia in a few other states (1), but to our knowledge, this is the first report of the disease on gaillardia in Virginia. Growers at the affected nursery reported observing white smut symptoms on gaillardia in previous years, but in the spring of 2002, almost the entire gaillardia crop was destroyed. The disease has not been seen on gaillardia in any other nurseries, but it could have significant impact on production if it spreads.

References: (1) D. F. Farr et al. Fungi on Plants and Plant Products in the United States. The American Phytopathological Society, St. Paul, MN, 1989. (2) W. Fischer. Manual of the North American Smut Fungi. Ronald Press, New York, 1953. (3) D. B. O. Savile. Can. J. Res. 25(C):109,1947.
First Report of Choke Disease Caused by Epichloë baconii in the Grass Agrostis castellana
Authors: Vaquero M. Romo , de Aldana B. R. Vázquez , Ciudad A. García , Criado B. García , Zabalgogeazcoa I.
Published: May 2007

Agrostis castellana is common in semiarid natural grasslands of the province of Salamanca, Spain. In this area, plants showing fungal stromata in their stems were observed in July of 2001. These symptoms are typical of choke disease, caused by Epichloë species in several grasses (3). In this disease, external fungal stromata develop around the leaf sheath of the flag leaf during the reproductive cycle of the plant host. As a result, the inflorescence does not emerge. In natural populations of A. castellana, less than 1% of plants showed disease symptoms, and all the stems of infected plants were sterilized by stromata. Intercellular endophytic mycelium was observed by microscopy in stem pith of diseased plants, but not on samples of 30 apparently healthy plants (1). Ergovaline, a fungal alkaloid, was not detected in lyophilized samples of infected plant tissue (2). In a fungal culture obtained from surface-disinfected leaf sheaths of a diseased plant (1), reniform conidia and conidiophores characteristic of the genus Epichloë were observed (4). To determine the fungal species, the nucleotide sequence of the ITS1-5.8SrRNA-ITS2 region and the three first introns of the beta-tubulin gene were obtained (EMBL Accession Nos. AJ490938 and AJ490939). When compared to those of other Epichloë species, these sequences identified the fungus from A. castellana as E. baconii (3). This fungus has been previously described as a pathogenic fungal endophyte in other Agrostis and Calamagrostis species (3,4). The fact that all stems of infected plants were diseased, infection incidence was low, and no alkaloids were detected in plants suggests that this grass-endophyte interaction is pathogenic and not mixed or mutualistic.

References: (1) E. Clark et al. J. Microbiol. Methods 1:149, 1983. (2) N. Hill et al. Crop Sci. 33:331, 1993. (3) A. Leuchtmann et al. Mycol. Res. 102:1169, 1998. (4) J. White Jr. Mycologia 85:444, 1993
First Report of Bremia lactucae Causing Downy Mildew on Helichrysum bracteatum in Italy
Authors: Garibaldi A. , Minuto A. , Gilardi G. , Gullino M. L.
Published: May 2007

Helichrysum bracteatum, also known as strawflower, is commonly grown for the production of dried flowers and, more recently, as a potted plant. This latter cultivation system is becoming increasingly important on the Liguria Coast in northern Italy. During the spring of 2002, severe oubreaks of a previously unknown disease were observed in commercial farms in the area of Albenga (northern Italy) on several cultivars of H. bracteatum. Leaves of infected plants appeared curled and blistered; the infected portions of leaves turned chlorotic. On the lower leaf surface of chlorotic areas, a dense, whitish growth was evident. Infected leaves eventually wilted without dropping. Basal leaves with poor air circulation were the most severely affected. Certain cultivars of H. bracteatum (such as ‘Florabella Pink’) were most seriously affected, while others (‘Florabella Gold’ and ‘Florabella White’) had less disease. Microscopic observations revealed sporangiophores emerging from the stomata that were dichotomically branched, ending with 4 to 7 sterigmata. The sporangia were globose and measured 15.5 to 16.8 μm in diameter. The pathogen was identified as Bremia lactucae based on the morphological characteristics. Pathogenicity was confirmed by inoculating healthy H. bracteatum (100-day-old ‘Florabella Gold’) as well as Lactuca sativa (25-day-old ‘Salad bowl’) plants with a sporangial suspension (1 × 105 sporangia/ml). Five plants of H. bracteatum and 10 of lettuce were used as replicates. Noninoculated plants served as controls. Inoculated and uninoculated plants were maintained in a growth chamber at 20°C and 90 to 95% relative humidity. After 7 to 10 days, typical symptoms of downy mildew developed on H. bracteatum and lettuce plants artificially inoculated. Bremia lactucae was observed on infected leaves. Uninoculated plants did not show symptoms. To our knowledge, this is the first report of Bremia lactucae on H. bracteatum in Italy. B lactucae was previously reported as the causal agent of downy mildew on H. bracteatum in several countries including the United Kingdom (3), the United States (1), and Egypt (2).

References: (1) S. A. Alfieri et al. Index of plant diseases in Florida. Bull No. 11, 1984. (2) H. Elarosi and M. W. Assawah. Rev. Plant Prot. Res., 39:583, 1959. (3) W. C. Moore. British Parasitic Fungi. Cambridge University Press, Cambridge, 1959.
First Report of Phytophthora ramorum on Canyon Live Oak in California
Authors: Murphy S. K. , Rizzo D. M.
Published: May 2007

During August 2002, Phytophthora ramorum S. Werres & A.W.A.M. de Cock was isolated from branches <2.0 cm in diameter on a canyon live oak (Quercus chrysolepis) in Mt. Tamalpais State Park, Marin County, CA. The shrub was a cluster of stems <1 m in diameter and 1 m high. Similar cankers were observed on small branches of adjacent canyon live oaks and there was dieback of the branches distal to the lesions. Many tanoak (Lithocarpus densiflorus), California bay laurel (Umbellularia californica), and evergreen huckleberry (Vaccinium ovatum) were also infected by P. ramorum at this site. The isolate was identified as P. ramorum by its abundant chlamydospores and caducous, semi-papillate sporangia and internal transcribed spacer (ITS) rDNA sequences identical to those of isolates of P. ramorum from Quercus spp., tanoak, and Rhododendron (1,3). To test for pathogenicity, two greenhouse trials (5 seedlings per trial plus controls) were conducted on 20- to 24-month-old canyon live oak seedlings. Coast live oak (Q. agrifolia, section Lobatae) seedlings were included in the trials as a comparison because the species is known to be susceptible (1). Stems (approximately 1 cm in diameter) were wound inoculated (1). After 6 weeks, lesion lengths in the cambium of canyon live oak averaged 17.2 mm (range 16 to 30 mm), which was significantly greater (analysis of variance [ANOVA], P < 0.05) in both trials than those of control inoculations (mean = 6 mm). Coast live oak seedlings inoculated at the same time had mean lesion lengths of 22.6 mm (range 15 to 30 mm). P. ramorum was recovered from 100% of inoculated stems. Canyon live oak has a wide geographic range within California, but is not common in the areas currently affected by P. ramorum. We have not observed disease symptoms or unusual mortality on overstory canyon live oaks. Although a number of understory canyon live oaks at the site on Mt. Tamalpais were apparently infected, the long-term effect of P. ramorum infection on understory trees remains unclear. To our knowledge, this is the first report of infection by P. ramorum of an oak species outside of the section Lobatae (red oaks); canyon live oak is classified in the section Protobalanus (intermediate or golden cup oaks) (2). Oaks in the section Quercus (white oaks) have not been observed to be infected by P. ramorum in the field.

References: (1) D. M. Rizzo et al. Plant Dis. 86:205, 2002. (2) P. Manos et al. Mol. Phylogenet. Evol. 12:333, 1999. (3) S. Werres et al. Mycol. Res. 105:1155, 2001.
Pea Tissue Necrosis Induced by Cucumber mosaic virus Alone or Together with Watermelon mosaic virus
Authors: Fukumoto F. , Masuda Y. , Hanada K.
Published: May 2007

Necrotic diseases of the stems, petioles, and leaves of pea plants (Pisum sativumL.), leading to wilting and death, occur in the Wakayama and Mie Prefectures of Japan. Based on host range, symptomatology, electron microscopy, and serological relationships, Watermelon mosaic virus (WMV) and three Cucumber mosaic virus (CMV) isolates (PE2, PE3A, and PB1) were isolated from diseased plants in the Wakayama Prefecture. In the Mie Prefecture, CMV (PEAN) also was isolated from pea plants with similar symptoms. Single infection with CMV (PB1 or PEAN) caused stem necrosis and eventual death of pea plants. Similar symptoms developed after double infection with WMV and PE2 or PE3A, whereas single infection with PE2 and PE3A induced symptomless infection in pea plants. We concluded either CMV alone or synergistic effects of mixed infection with CMV and WMV induced pea plant stem necrosis.
Occurrence ofBotrytis cinereaand Subsequent Disease Expression at Different Positions on Leaves and Bunches of Grape
Authors: Holz Gustav , Gütschow Minique , Coertze Sonja , Calitz Frikkie J.
Published: May 2007

The occurrence of Botrytis cinerea and subsequent disease expression at different positions on leaves and bunches of grape was determined from 1996 to 2000. Different techniques were used to detect viable inoculum on material obtained from table (cvs. Barlinka and Dauphine) and wine grape (cv. Merlot) vineyards. Isolations were made from berry skins on Kerssies' B. cinerea selective medium or on water agar medium supplemented with paraquat. Leaves and parts of bunches bearing three to seven berries on a short rachis section were used untreated or treated with paraquat, or were frozen for 1 h at -12°C. Paraquat and freezing were used to terminate host resistance and to promote the development of the pathogen from the tissues. The material was used untreated to detect the pathogen on the surface, or were surface-sterilized to detect mycelia (latent infection) in the tissue. B. cinerea occurred in a consistent pattern in leaves and bunches in all vineyards. Based on the combined data for tissues exposed and unexposed to paraquat, B. cinerea occurred predominantly in bunches and was mostly associated with the bases of the berry and the pedicel. Overall, approximately 30% of the berries yielded B. cinerea at these positions. The next prominent positions occupied were leaf blades, rachises, and laterals, of which approximately 20% yielded B. cinerea. The pathogen occupied the petioles less often (10%), and the berry cheek infrequently (5%). The stylar end of the berries, on the other hand, was virtually free (0.02%) of the pathogen. Disease expression in bunches displayed the pattern showed by the inoculum ecology, and symptoms consistently developed first at the berry-pedicel attachment zone. The isolation studies showed that the pathogen seldom occurred on the surface or in the skin tissue near the base, cheek, or stylar end of berries. Latent infections in the berry base were also few at véraison and harvest. Collectively, the findings indicate that conidia dispersed in early season in bunches, and residing superficially at the berry-pedicel attachment zone, are a major factor in B. cinerea bunch rot.
Distribution of Pathotypes of Rhynchosporium secalis and Cultivar Reaction on Barley in Alberta
Authors: Xi K. , Turkington T. K. , Helm J. H. , Briggs K. G. , Tewari J. P. , Ferguson T. , Kharbanda P. D.
Published: May 2007

Forty-four barley accessions and commercial cultivars with different levels of resistance to scald caused by Rhynchosporium secalis were evaluated for scald reaction from 1997 to 1999 at various sites in Alberta. The accessions Hudson, Atlas, Atlas 46, Atlas 68, Abyssinian, and Kitchin that have the major resistance genes were resistant to pathotypes of R. secalis at all sites. Although scald levels were low for these accessions, they were significantly different among years. Pathotypes of R. secalis and environmental conditions affected diseases levels on 32 commercial cultivars, resulting in significantly different scald reactions among sites and seasons. Resistance in commercial cultivars, AC Stacy, Kasota, and Seebe, held up at most sites with the majority of cultivars being intermediate to moderately susceptible. Cultivars that were previously considered resistant were intermediate in reaction and became increasingly susceptible at some sites from 1997 to 1999. Pathogen virulence was more diverse at the sites where the cultivars became increasingly susceptible compared with sites where the same cultivars were resistant. Scald reactions of the commercial cultivars depended on location, which reflected the presence of different pathotypes, as well as variation in environmental conditions. Consequently, scald management via cultivar choice will be dependent on location.