bluuebunny/crossref_metadata_2025 huggingface dataset:
Assessment of Phenotypic Variability in Erwinia stewartii Based on Metabolic Profiles
Authors: Wilson W. J. , Dillard H. R. , Beer S. V.
Published: May 2007

One hundred twenty-four bacterial isolates originating from sweet corn or corn flea beetles in the northeastern, midwestern, and mid-Atlantic United States were verified as Erwinia stewartii (Pantoea stewartii subsp. stewartii) and characterized phenotypically by their respiratory response to 91 carbon sources. The unweighted pair group method of averages (UPGMA) was used to construct a dendrogram that revealed homogeneous metabolic profiles at 93% similarity. Two-thirds of the isolates formed 18 separate groups, each sharing the same metabolic profile. One-third of the isolates had distinct metabolic profiles. Most groups shared either isolation source, geographical location, and/or year of isolation. Members of some groups persisted through time and had been isolated from diverse geographical locations. Four representative strains of the proposed Pantoea stewartii subsp. indologenes were also characterized; their metabolic profiles were most similar to those of Erwinia herbicola (Pantoea agglomerans).
Influence of Crop Rotation on the Incidence ofPythium- andRhizoctonia-Induced Carrot Root Dieback
Authors: Davis R. M. , Nunez J. J.
Published: May 2007

The influence of various crop rotations on population densities of Pythium spp. and Rhizoctonia solani, subsequent carrot yields, and incidence of carrot root dieback was investigated. Carrots followed crops of alfalfa, barley, carrots, cotton, onions, or fallowed soil in two independent trials. Populations of Pythium spp. were greater following alfalfa and barley than other crops in one of the 2 years of the study. Populations of R. solani were generally greater following alfalfa and cotton than other crops in each of the 2 years of the study. In 1 year, yields of marketable carrots were reduced following the alfalfa crop; no other cropping pattern influenced carrot yields. The incidence of root dieback, which resulted in mature carrots with misshapen or multiple taproots, was generally greater following alfalfa and barley than other crops in one trial, and greater following alfalfa and cotton in the other trial.
Control of Postharvest Decay in Pear by Four Laboratory-Grown Yeasts and Two Registered Biocontrol Products
Authors: Sugar David , Spotts Robert A.
Published: May 2007

Control of blue mold decay in Bosc pears was studied with the laboratory-grown yeasts Rhodotorula glutinis, Cryptococcus infirmo-miniatus, and two strains of Cryptococcus laurentii, as well as registered biocontrol products Aspire, containing the yeast Candida oleophila, and Bio-Save 11 (now Bio-Save 110), containing the bacterium Pseudomonas syringae. Both thiabendazole (TBZ)-sensitive and TBZ-resistant strains of Penicillium expansum were used. Aspire treatment reduced the average lesion diameter by approximately 65 and 45%, and reduced decay incidence by 27 and 9% with TBZ-resistant and TBZ-sensitive P. expansum, respectively, in the first year of the study, but did not result in significant decay control in the second year. Bio-Save 11 reduced decay lesion diameter by 32 to 72% and incidence by 21 to 40% over the 2 years. In both years, TBZ-sensitive P. expansum was completely controlled by the combination of either C. laurentii (both strains), R. glutinis, or C. infirmo-miniatus with 100 ppm TBZ. With TBZ-resistant P. expansum, control of wound infection with these yeasts alone or with 100 ppm TBZ ranged from 62.9 to 100%. In a packinghouse trial, control by Bio-Save 110 + 100 ppm TBZ and Aspire + 100 ppm TBZ was not different than control by TBZ at 569 ppm, the maximum label rate. The amount of decay following Aspire + 100 ppm TBZ treatment was significantly less than the amount of decay following Bio-Save 110 + 100 ppm TBZ treatment.
Isolation of Pythium Species from Zoysia Grass and Their Effect on Severity of Large Patch Disease
Authors: Aoyagi A. , Kageyama K. , Hyakumachi M.
Published: May 2007

Pythium periplocum, P. rostratum, P. torulosum, and P. vanterpoolii were predominant Pythium species isolated from nine sites with a history of large patch disease of zoysia grass. Rhizoctonia solani AG2-2 LP and the Pythium species were isolated from 21 sod samples of zoysia grass exhibiting large patch symptoms in five golf courses. R. solani AG2-2 LP was obtained from all samples, while P. periplocum, P. rostratum, P. torulosum, and P. vanterpoolii were obtained from 14, 6, 11, and 8 samples, respectively. At least one of the four Pythium species was recovered from 19 samples. To verify pathogenicity of these four species of Pythium on zoysia grass, they were inoculated alone and together with R. solani AG2-2 LP on zoysia grass. When individual isolates were used to inoculate zoysia grass, R. solani AG2-2 LP, P. periplocum, and P. vanterpoolii were moderately aggressive, while P. torulosum and P. rostratum caused little or no disease. Symptoms produced by R. solani AG2-2 LP included orange discoloration of the sheath, and the sheath was easily pulled from the crown. P. periplocum and P. vanterpoolii induced only sheath chlorosis, and the sheath was not easily removed from the crown. In coinoculation tests, the combination of R. solani AG2-2 LP and P. torulosum intensified disease severity on zoysia grass and induced more rapid symptom development than did R. solani AG2-2 LP alone. The combination of R. solani AG2-2 LP and P. periplocum or P. vanterpoolii resulted in sheath necrosis and bare patches, similar to large patch symptoms observed on golf courses.
Reactions of Processing Sweet Corn Hybrids to Gibberella Ear Rot
Authors: du Toit Lindsey J. , Pataky Jerald K.
Published: May 2007

Gibberella ear rot has increased in prevalence recently on late-season processing sweet corn grown in the Midwestern United States. Little information is available about the reactions of hybrids currently grown for processing. A total of 52 processing hybrids were evaluated in 1996 and 1997 for reactions to Gibberella zeae following one of two methods of inoculation: inserting an infested toothpick or injecting a spore suspension in the silk channel 7 days after the mid-silk growth stage. Ratings of ear rot severity ranged from 2.4 to 8 on a scale of 1 to 9. Severity of ear rot differed among hybrids, but none of the hybrids was highly resistant, nor did the hybrids display a great degree of variation for reaction to G. zeae. Severity of ear rot was consistently lower for cvs. Sprint and HMX 5372 than for the other hybrids. Ear rot ratings also were lower for cvs. GH 1834 and GH 2690 in three of four comparisons. Severity of ear rot was consistently higher for cv. GH 2628 in all comparisons and for cvs. Empire, Excalibur, GG 42, GH 1861, Jubilee, Rival, and WSS 3680 in three of four comparisons. Ranks of some hybrids changed between inoculation methods, years, or both, but most hybrids were ranked similarly in at least three of four comparisons. Coefficients of variation were approximately 5% higher for the injection method of inoculation in 1996 than for the other trials. The toothpick method of inoculation required less labor and ranked hybrids as consistently or more consistently than the injection method.
A Simple Quantitative Procedure for Inoculation of Safflower with Teliospores of the Rust Fungus, Puccinia carthami
Authors: Bruckart William L.
Published: May 2007

A procedure is needed to determine susceptibility of safflower seedlings to teliospore inoculations of foreign accessions of Puccinia jaceae, a candidate agent for biological control of Centaurea solstitialis (yellow starthistle). The indigenous safflower rust pathogen, P. carthami, served as both model and basis for a future comparative study of these two rust fungi on safflower. The procedure involves inoculation of 2-day-old safflower seedlings on the hypocotyl near the base of the cotyledons with a known number of teliospores suspended in a 1-μl drop of a 0.1% water agar and wetting agent carrier. Advantages of this procedure include (i) quantification, by spore type, of inoculum applied to each seedling, (ii) precise placement of inoculum on test plants, and (iii) conservation of inoculum. Results were verified in studies with two safflower cultivars inoculated with 0, 15, 60, or 240 teliospores of either of two isolates of P. carthami. Plant height and dry weight data collected 6 weeks after inoculation revealed significant interactions for cultivar × inoculum concentration and for isolate × inoculum concentration. Similar results were achieved when safflower seeds were rolled in dry teliospores of P. carthami but not when seedlings grew through teliospore-infested sand. The latter two approaches (dry teliospore and infested sand inoculation) require much more inoculum and are only semiquantitative. The microliter drop procedure has potential usefulness in host range and quantitative studies involving other pathogens, including bacteria, fungi, and nematodes.
Incidence-Severity Relationships in the Pathosystem Coffea arabica-Hemileia vastatrix
Authors: Silva-Acuña R. , Maffia L. A. , Zambolim L. , Berger R. D.
Published: May 2007

Incidence-severity relationships for coffee rust were studied to determine if the easily assessed incidence could be used to evaluate host resistance and fungicide treatment. At two locations in each of 3 years, the incidence of rust on 300 leaves was compared with two assessments of severity: (i) the average number of sporulating pustules per leaf, and (ii) the estimated leaf area with rust. For nine or 10 assessments in time at one location and pooled over 3 years, the average number of sporulating pustules per leaf (Y sp) was well related with the incidence of leaves with rust (X) as Y sp = 0.02982+ 0.017035X +0.000573X 2; R 2 = 0.87. The leaf area with rust (Y la) was also well related with incidence of leaves with rust as Y la = 0.001 − 0.01076X +0.008376X 2; R 2 = 0.92. For two independent data sets from a second location obtained over two seasons, the above models satisfactorily fit the relationships for the average sporulating pustules per leaf (R 2 = 0.97 and 0.96) and for the estimated leaf area with rust (R 2 = 0.95 and 0.98). Therefore, the readily determined incidence can be used to estimate both measures of disease severity of coffee rust.
First Report of Powdery Mildew Caused by an Oidium sp. on Banana Shrub (Michelia figo)
Authors: Holcomb G. E.
Published: May 2007

Banana shrub (Michelia figo (Lour.) Spreng.) is an evergreen grown in southern landscapes in hardiness zones 7 to 9. A powdery mildew disease has been observed sporadically on this plant for several years in the Baton Rouge area during fall months, but symptoms were always mild. During the summer and fall of 1998, banana shrub plants were observed with moderately severe powdery mildew infections that resulted in leaf chlorosis, distortion, and some defoliation. An Oidium sp. was present on both leaf surfaces, but sporulation was more abundant on the abaxial surfaces. Conidia were ellipsoid, produced in chains, devoid of conspicuous fibrosin bodies, and averaged 37 × 19 μm. No sexual stage was found. Conidia brushed from infected leaves to healthy leaves of a potted banana shrub maintained in a greenhouse caused new infections in 5 to 8 days. Factors responsible for the increased severity of the disease in 1998 are unknown, but the unusually dry summer may have contributed to the increased incidence of this disease. An Oidium sp. was listed on M. figo in Australia and the United States (1), but no other reports were found to confirm this. This is the first report of the occurrence of a powdery mildew on M. figo in the United States.

Reference: (1) K. Amano. Host Range and Geographical Distribution of the Powdery Mildew Fungi. Japan Scientific Press, Tokyo, 1986.
First Report of Erysiphe cichoracearum Infecting Hedera canariensis var. azorica in Italy
Authors: Nali C.
Published: May 2007

A powdery mildew disease of variegated ivy (Hedera canariensis L. var. azorica) was observed on the Tyrrhenian coast in Tuscany (Italy) in spring 1998. Symptoms began as small, nearly circular reddish spots that later enlarged and coalesced. The hyaline mycelium produced abundant, ellipsoid conidia in long chains that ranged from 20 to 40 μm in length and from 12 to 25 μm in width. Cleistothecia were globose (100 to 120 μm diameter), dark brown (when mature) with a basal ring of mycelioid appendages, and contained several (up to 20) ovate asci, each generally containing two ascospores. Ascospores were hyaline, one-celled, ellipsoid (20 to 35 μm in length and 10 to 20 μm in width). The morphological characteristics of this fungus were those given for Erysiphe cichoracearum DC. Infection also was found on English ivy (Hedera helix L.). It is reported that this species is, occasionally, subject to powdery mildew caused by E. cichoracearum (1). Conidia from infected leaves were shaken onto leaves of melon (Cucumis melo L.), cucumber (Cucumis sativus L.), watermelon (Citrullus lanatus [Thunb.] Matsum. & Nakai), lettuce (Lactuca sativa L.), tomato (Lycopersicon esculentum Mill.), tobacco (Nicotiana tabacum L.) and variegated and English ivy. After 7 days, the disease was observed on cucumber, melon, watermelon, tobacco, and variegated ivy. Examination confirmed that test plants were infected with E. cichoracearum. This is the first report of E. cichoracearum on variegated ivy in Italy.

Reference: (1) P. P. Pirone. 1970. Diseases and Pests of Ornamental Plants. The Ronald Press, New York.
Effect of Registered Potato Seed Piece Fungicides on Tuber-borne Phytophthora infestans
Authors: Inglis D. A. , Powelson M. L. , Dorrance A. E.
Published: May 2007

Curative applications of thiophanate-methyl + mancozeb to blighted seed pieces of three potato (Solanum tuberosum) cultivars significantly reduced the amount of surface area colonized by Phytophthora infestans compared with treatment with thiophanate-methyl or no fungicide under laboratory conditions. Percent blighted tuber surface area over six tests averaged 3.5, 11.4, and 21.2% for the three treatments, respectively. Seed pieces inoculated with P. infestans US-8 or US-11 incubated, and then treated with the same fungicides and planted at Oregon and Washington field sites, respectively, had higher emergence across locations for thiophanate-methyl + mancozeb than for thiophanate-methyl (30 versus 12.5%). Emergence of healthy thiophanate-methyl + mancozeb-treated seed pieces averaged 93%. When protective applications of these fungicides, mancozeb, or fludioxinil were made to healthy potato seed pieces prior to inoculation with P. infestans, plant emergence in the greenhouse was significantly increased with thiophanate-methyl + mancozeb compared with fludioxinil (92 versus 36%) in Oregon and with thiophanate-methyl or fludioxinil (90 versus 20 and 24%) in Washington. Inoculation of healthy seed pieces reduced plant stand in all greenhouse tests; however, treatment with thiophanate-methyl + mancozeb or mancozeb alone prior to inoculation resulted in sprout emergence similar to that of the noninoculated control. In a late blight management program, treatment of seed pieces with a registered fungicide that has activity against P. infestans contributes to an increase in plant emergence and improved crop uniformity. However, for maximum benefit, the fungicide must be in place before coming in contact with the pathogen.
Efficacy of Sodium Tetrathiocarbonate and Propiconazole in Managing Armillaria Root Rot of Almond on Peach Rootstock
Authors: Adaskaveg James E. , Förster Helga , Wade Layne , Thompson David F. , Connell Joseph H.
Published: May 2007

The efficacy of sodium tetrathiocarbonate (STTC or Enzone 31.8%, a liquid formulation that releases carbon disulfide) and the demethylation inhibiting (DMI) fungicide propiconazole (Alamo 1.1EC) was evaluated for management of Armillaria root rot of almond grown on Lovell peach rootstock. After 12 months, pre-/post-plant STTC (189 liters of 3,850 and 500 mg/liter/3 m2 treatment site, respectively) or tarped pre-plant methyl bromide (Dowfume 98%, 454 g a.i./3 m2) soil fumigation treatments significantly (P < 0.05) reduced the recovery of Armillaria mellea from naturally infected root segments at 0.3 and 1.2 m soil depths, compared with control sites. Tarped methyl bromide treatments eradicated the fungus from infested root segments at both depths; however, nontarped sites significantly reduced the recovery only at the 1.2 m depth. Pre-plant STTC (189 liters of 3,850 mg/liter/3 m2) reduced the recovery of the fungus but was not as effective as the pre-/post-plant STTC treatment. Recovery of the fungus in post-plant treatments with STTC (189 liters of 500 mg/liter/3 m2) was not significantly (P > 0.05) different from control sites. Additionally, mortality of almond tree replants from phytotoxicity was significantly higher in post-plant applications of STTC, compared with the other treatments or with the control trees. A gel formulation of 31.8% STTC (1,800 ml of 318,000 mg of STTC per liter per tree stump) applied in wells that were drilled into tree stumps eradicated the fungus from trunk and primary roots but not secondary or tertiary roots, whereas liquid formulations of STTC and metam-sodium (Vapam - 32.7% sodium N-methyldithiocarbamate) eradicated the fungus from only trunks but not roots. Treatments with STTC (189 liters of 500 mg/liter/3 m2) were not effective in preventing mortality of A. mellea-infected, mature, 7- to 8-year-old almond trees. Propiconazole (Alamo 1.1EC) was shown to be toxic to mycelial growth of A. mellea grown on potato dextrose agar with an EC50 value of 0.15 mg/liter. Therapeutic, passive injections of propiconazole into 7- to 8-year-old almond trees (Lovell peach rootstock) were successful in reducing mortality of infected trees during two growing seasons, compared with infected control trees treated with water.
Baseline Sensitivities of Venturia inaequalis Populations to the Strobilurin Fungicide Kresoxim-methyl
Authors: Olaya Gilberto , Köller Wolfram
Published: May 2007

The efficacies of the new strobilurin fungicide kresoxim-methyl for the protection of apple leaves from infection by baseline populations of Venturia inaequalis were uniform across five major apple growing regions in North America. The mean ED50 value determined for 25 populations was 0.35 μg ml-1, with values ranging from 0.11 μg ml-1 to 0.75 μg ml-1. The mean level of scab control achieved at the kresoxim-methyl dose of 4 μg ml-1 was 93%. For one of the five orchards sampled in each region, kresoxim-methyl sensitivities of germinating conidia were determined. Sensitivities of 250 isolates were broadly distributed, with ED50 values ranging from 0.003 μg ml-1 to 0.14 μg ml-1 and a mean of 0.02 μg ml-1. This broad range of in vitro sensitivities was not reflected for the in vivo efficacy of kresoxim-methyl in the protection of apple leaves from scab infections. The discrepancy between in vivo and in vitro sensitivities implies that in vivo tests are more useful for the monitoring of kresoxim-methyl sensitivities of orchard populations. Because it can be expected that only isolates resistant under both test conditions will be prone to future selection, such isolates will contribute to increased frequencies of the least sensitive isolates described in this baseline study. Testing of in vitro isolate sensitivities will, therefore, provide an additional tool in the monitoring of kresoxim-methyl resistance development.
Morphological, Pathogenic, and Genetic Comparisons of Colletotrichum graminicola Isolates from Poaceae
Authors: Browning Marsha , Rowley Lisa V. , Zeng Peiyu , Chandlee Joel M. , Jackson Noel
Published: May 2007

Isolates of Colletotrichum graminicola from annual blue grass and creeping bent grass were investigated for their morphological characteristics, host specificity, and genetic relatedness. One isolate from maize and one from sorghum (C. sublineolum) were included for comparison. Recently isolated cultures of C. graminicola from annual blue grass were readily distinguished from those isolated from creeping bent grass on the basis of pigmentation. Differences in appressoria size and shape were found only between the turf grass isolates and those from maize and sorghum. Spore length varied significantly between host groups. Differences in host range and virulence were also apparent. In general, isolates from creeping bent grass incited disease on both creeping bent grass and annual blue grass, while those from annual blue grass essentially were limited to host. Random amplified polymorphic DNA (RAPD) marker analysis of C. graminicola isolates from turf grass revealed that a high degree of genetic similarity exists among isolates recovered from the same host, but exceptions were found. Therefore, an absolute distinction between isolates recovered from two turf grass hosts could not be made based on RAPD markers.
Efficacy of Solarization and Cabbage Amendment for the Control of Phytophthora spp. in North Florida
Authors: Coelho L. , Chellemi D. O. , Mitchell D. J.
Published: May 2007

The effects of soil solarization with or without cabbage leaf amendments on the survival of Phytophthora spp. were evaluated in several North Florida soils. Soil temperature under solarization treatments reached a maximum of 47°C at a 10-cm depth, but only 41°C at 25 cm. Solarization with a clear, gas-impermeable film was as effective as methyl bromide in reducing populations of P. nicotianae at a 10-cm depth but had no effect on populations at a depth of 25 cm. Populations of P. capsici after solarization with either a clear, low-density polyethylene or a clear, gas-impermeable film were similar to methyl bromide treatment at the 10-cm depth, while at the 25-cm depth, no reduction in populations was observed. Incorporation of cabbage into the soil at a rate of 6.6 to 8.9 kg/m2 did not enhance the effectiveness of solarization in reducing populations of either Phytophthora sp.
First Report of Black Sigatoka in Florida
Authors: Ploetz R. C. , Mourichon X.
Published: May 2007

Black Sigatoka, caused by Mycosphaerella fijiensis, is widely recognized as the most important disease of banana, Musa spp. It has spread rapidly in the Western Hemisphere since it first appeared in Honduras in 1972, and is now found in the Caribbean basin in Cuba, Jamaica, and the Dominican Republic, and on the mainland from central Mexico south to Bolivia and northwestern Brazil (2). In October 1998, symptoms of black Sigatoka (2) were observed on several different cultivars in a collection at the University of Florida's Tropical Research and Education Center (TREC) in Homestead (25°30′ N, 80°30′ W). During preliminary surveys, the disease was found at four of eight locations in a 15 km2 area to the north of TREC. Disease severity, rated as the youngest leaf spotted (YLS), averaged 4.8 on the most susceptible cultivar, Rajapuri, at one of the locations. The extent and history of damage at this site indicated that black Sigatoka had been there for at least 3 to 4 years. The prevailing east to west winds in the Caribbean, and highly variable incidence and severity of the disease also suggested that the pathogen had been introduced to the area on infected seed pieces (suckers) rather than by wind or rain-blown ascospores from Cuba or other affected areas (1). The presence of the disease was confirmed after the following characteristics of the pathogen's anamorph, Paracercospora fijiensis, were observied on affected leaves: simple conidiophores occurring singly or in groups of two to six with one to several septa, scars, and usually a broadened base; and conidia much more abundant on lower leaf surfaces, straight to variously bent with one to several septa and a conspicuous scar at the base. Single-ascospore cultures were recovered from Rajapuri and are stored at CIRAD/FLHOR in Montpellier. This is the first time black Sigatoka has been reported in the continental United States. Banana is a minor but significant tropical fruit crop in southern Florida, with fruit valued at over $2.5 million per annum. Production from Hua moa, Silk, and other important cultivars will probably be affected as the disease becomes established in this part of the state.

References: (1) R. H. Stover. Plant Dis. 64:750, 1980. (2) J. C. Tejerina et al. Plant Dis. 81:1332, 1997.
First Report of Tomato Bushy Stunt Virus Isolated from Lettuce
Authors: Liu H.-Y. , Sears J. L. , Obermeier C. , Wisler G. C. , Ryder E. J. , Duffus J. E. , Koike S. T.
Published: May 2007

In recent years a disease causing dieback and necrosis of Romaine and leaf lettuce has become increasingly important in California and incidence is becoming more widespread. This disease has been primarily found in areas where soil has been dredged from a river or in flooded land. Tomato bushy stunt virus (TBSV) isolates have been isolated from roots and leaves of symptomatic lettuce. The particles are isometric with a diameter of 30 nm. Double-stranded RNA (dsRNA) profiles are identical to the tomato and Prunus isolates of TBSV. However, spurs are formed in agar double diffusion tests when antisera to the tomato and Prunus isolates were used. A similar dieback disease of lettuce was observed in several counties of California during the mid-1980s. Symptoms of this disease are very similar to those described for the “brown blight” disease of lettuce reported in the 1920s (1), including severe stunting of plants and extensive chlorosis, mottling, and necrosis of older leaves. Plants infected early in their development may die. Although inoculation under greenhouse conditions has not reproduced the dieback disease in lettuce, TBSV has been consistently isolated from field-grown, symptomatic lettuce. The question of whether this new dieback disease of lettuce is caused only by lettuce isolates of TBSV or if some other viruses are also involved needs further studies.

Reference: (1) I. C. Jagger. Phytopathology 30:53, 1940.
First Report of the Presence of a Phytoplasma in Tomato in Mauritius
Authors: Dookun A. , Aljanabi S. , Saumtally S. , Autrey L. J. C.
Published: May 2007

In recent years, tomato plants (Lycopersicon esculentum Mill., cultivar MST 32/1) grown in Mauritius were observed with symptoms characteristic of a phytoplasmal infection. Young plants exhibited stunted growth, with a bunchy top symptom on one or more stems. The leaves were small with a curled margin, sometimes were purplish, and were clustered as a rosette. On older plants, other leaf symptoms, such as necrotic vein, mosaic, and vein clearing, that were typical of viral infection were observed. In March to June 1998, research was initiated to determine whether a phytoplasma or a virus was associated with the problem. Virus screening was carried out by double antibody sandwich enzyme-linked immuno-sorbent assay (DAS-ELISA) with the following antisera: tomato mosaic virus (TMV), tomato leaf curl virus (TLCV), tomato spotted wilt virus (TSWV), cucumber mosaic virus (CMV), potato virus X (PVX), potato virus Y (PVY), and potato leaf roll virus (PLRV). The presence of a phytoplasma was assayed by the polymerase chain reaction (PCR) with universal primers that amplify the 16S rDNA sequences. Oligonucleotide pairs RU3 and FU5 (1) and P1 and P6 (2) were evaluated separately. Template DNA was prepared from young leaves with the Nucleon Phyta-Pure Plant DNA extraction kit (catalog no. RPN 8511, Amersham Life Science, Buckinghamshire, U.K.). Amplification of a 880-bp or a 1,400-bp product with the two primer pairs confirmed the presence of a phyto-plasma in the tomato plants with the bunchy top symptoms. No amplification was obtained from plants that had both bunchy top and necrotic symptoms on the leaves and that were found to be infected with PVY by ELISA. To determine whether phenolics and other inhibitors from the virus-induced necrotic tissue interfered with the detection of phytoplasmas, plant DNA from these tissues was spiked with known phytoplasmal DNA. Amplification was not successful, confirming the presence of PCR inhibitors. Further purification of the DNA with phenol/chloroform before precipitation helped to obtain DNA of a purer quality from which a positive band representing the sequence of a phytoplasma was amplified. This is the first report of a phytoplasma in tomato in Mauritius.

References: (1) U. Ahrens and E. Seemüller. Phytopathology 82:828, 1992. (2) S. Deng and D. Hiruku. J. Microbiol. Methods 14:53, 1991.
Species-Specific Detection of the Maize Pathogens Sporisorium reiliana and Ustilago maydis by Dot Blot Hybridization and PCR-Based Assays
Authors: Xu M. L. , Melchinger A. E. , Lübberstedt T.
Published: May 2007

Head smut of maize, caused by Sporisorium reiliana, may substantially reduce grain yield. The objective of the present study was to develop a highly specific and sensitive DNA-based assay for detection of S. reiliana and its differentiation from Ustilago maydis, a maize fungus inducing the symptomatically similar common smut disease. Plasmid libraries of S. reiliana and U. maydis were constructed using a shotgun cloning procedure. Clones containing strongly hybridizing species-specific DNA were selected by screening libraries with their own labeled genomic DNA, followed by cross-hybridization with genomic DNA of maize and other maize-pathogenic fungi. The selected clones were used to generate subclones with short insert fragments to facilitate PCR amplification for labeling and primer design for a PCR assay. Using Dig-dUTP labeled inserts, detection of less than 0.16 ng of fungal DNA was possible by dot blot hybridization. Sequences of insert fragments were determined to design primer pairs for a PCR-based assay. Primer pairs SR1 and SR3 are species-specific for S. reiliana, and UM11 is species-specific for U. maydis. The PCR-based assays can detect fungal DNA of less than 1.6 pg using SR1 and SR3, and 8 pg using UM11, irrespective of the presence of maize DNA. Use of SR1 and SR3 allowed detection of S. reiliana in the extracts of pith, node, and shank from S. reiliana-infected plants, but not in leaves. Thus, both the dot blot hybridization and the PCR-based assays provide a highly sensitive and reliable tool for detection and differentiation of corn smut caused either by S. reiliana or by U. maydis.
Fusarium Wilt Disease Caused by Fusarium oxysporum f. sp. phaseoli on a Common Bean Cultivar, G 2333, in Rwanda and the Democratic Republic of Congo
Authors: Buruchara R. A. , Pastor-Corrales M. A. , Scheidegger U.
Published: May 2007

The common bean (Phaseolus vulgaris L.) is an important source of dietary protein for poor resource families in Rwanda and the Kivu region of the Democratic Republic of Congo (DRC). During the second season of 1990, symptoms consisting of chlorosis, premature defoliation, stunting, wilting, and vascular discoloration were observed for the first time on an improved popular climbing bean cultivar, G 2333, in the prefectures of Butare and Gikongoro, in southwest Rwanda. Between 1991 and 1994, surveys to determine disease occurrence were conducted in the two prefectures and in Kigali North, Gitarama, Cyangugu, and Kibuye in Rwanda, and in the south Kivu region of the DRC. Aseptic isolation from diseased plant samples yielded the fungus Fusarium oxysporum f. sp. phaseoli. Pathogenicity tests on G 2333 seedlings by the root-dip inoculation method resulted in symptoms similar to those observed in the field, and recovery of the fungus, fulfilling Koch's postulate. Control seedlings gave no symptoms. Disease incidence was 44 and 53% in Butare and Gikongoro, respectively, during the first season of 1991 and 50 and 70% in the second season, while crop loss in some fields was as high as 100%. Between 1992 and 1994 the disease was also observed in the four other prefectures in Rwanda, and in south Kivu. Climbing bean cultivars Gisenyi-2-bis, G 865, Flora de Mayo, and Puebla 444 Criollo, and several bush local varietal mixtures grown where the disease occurred, were unaffected. CIAT bean Fusarium wilt differentials IPA 1, RIZ 30, A 211, Mortiño, Diacol Calima, BAT 477, HF 465-63-1, and Ecuador 650, and lines A 300 and XAN 112, were inoculated with three isolates (FOP-RW1, FOP-RW2, FOP-RW3) from Rwanda. Only IPA 1, RIZ 30, and A 211 were susceptible, indicating the isolates' likeness to the Brazilian race (1). This was the first report of Fusarium wilt disease on G 2333 in the two countries despite the cultivar having been grown for about 5 years.

Reference: (1) R. L. D. Ribeiro and D. J. Hagedorn. Phytopathology 69:272, 1979.
New Record of Ceratocystis fimbriata Causing Wilt of Pomegranate in India
Authors: Somasekhara Y. M.
Published: May 2007

Wilt of pomegranate (Punica granatum L.) was first noticed in two areas of the Bijapur district (16°49′N; 75°43′E) of India in 1990. Around 1993, rapid spread of this disease was observed in the entire Bijapur district. The cause was not identified until 1995. Initial symptoms were yellowing and wilting of leaves on one to several branches leading to death of affected plants in a few weeks. Cross sections of diseased plants revealed brown discoloration in the outer xylem from roots to the main trunk. A survey of 44 locations from 1995 to 1998 showed an approximate loss of Rs. 30 lakhs (ca. US$69,770) and 7.5% (3,474 of 47,096 plants wilted) of the crop. At 13 locations, plants also were severely infested with shot hole borer (Xyleborus spp.). In 1996, the fungus, a Ceratocystis sp., was isolated from discolored stem, root, and branch tissues on wilted plants collected from various locations, e.g., A. Sangapur, Bagalkot, Bijapur, Bilagi, Kanamadi, Tajpur, and Tikota. The fungus isolated from Bagalkot was confirmed by the International Mycological Institute (UK) as C. fimbriata Ellis & Halst. (Specimen No. W 5496, PBUR) in 1997; the strain of this fungus, i.e., Latin American group, was identified in 1998 by T. C. Harrington (Iowa State University). Morphological characteristics of mycelium, conidia, conidiophore, chlamydospores, perithecia, and ascospores were similar to those described previously (1). Pathogenicity of this fungus was confirmed by inoculating wounded roots. This is the first report of C. fimbriata causing wilt on pomegranate.

Reference: (1) Anonymous. C.M.I. Descriptions of Pathogenic Fungi and Bacteria. No. 141. CAB, Surrey, England.
Analysis of DNA Polymorphism and Virulence in Philippine Strains of Xanthomonas oryzae pv. oryzicola
Authors: Raymundo A. K. , Briones A. M. , Ardales E. Y. , Perez M. T. , Fernandez L. C. , Leach J. E. , Mew T. W. , Ynalvez M. A. , McLaren C. G. , Nelson R. J.
Published: May 2007

Molecular tools were used to analyze the genetic diversity and population structure of Xanthomonas oryzae pv. oryzicola, the bacterial leaf streak pathogen of rice in the Philippines. Representative pathogen strains were selected and used to assess resistance in rice germplasm. A partial genomic library of X. oryzae pv. oryzicola was constructed, and a 459-bp clone containing the repetitive DNA element R41 was selected as a probe for restriction fragment length polymorphism (RFLP) analysis and sequenced. R41 shared 44% sequence homology with the putative transposase gene of IS1112, an insertion element cloned from X. oryzae pv. oryzae. Using R41 as a probe for RFLP analysis, 26 band profiles were discerned in a collection of 123 strains of X. oryzae pv. oryzicola. Analysis of PstI digestion patterns of DNA from the same collection resolved 36 haplotypes. Several clusters of strains were detected after grouping of data based on either pR41 as a probe or Pst1 digestion patterns. However, based on bootstrap analysis, the clusters were not robust. Genetic diversity was high for the entire collection as well as within spatially and temporally defined subsets of strains. Even a set of strains collected from a single site at a single time was highly diverse. Strains representing the different DNA types were inoculated to a set of diverserice cultivars. Consistent rice varietal groupings were obtained from disease reaction data, but there was no correlation between pathogen isolate cluster and host reaction across inoculation trials. Isozyme group I of rice, representing tropical japonica and javanica germplasm, is a promising source of resistance to bacterial leaf streak.
First Report of Tomato Yellow Leaf Curl Virus in Tomato in South Georgia
Authors: Momol M. T. , Simone G. W. , Dankers W. , Sprenkel R. K. , Olson S. M. , Momol E. A. , Polston J. E. , Hiebert E.
Published: May 2007

In October 1998, symptoms characteristic of tomato yellow leaf curl virus (TYLCV) were observed on fresh market tomato (Lycopersicon esculentum Mill.) in four production fields, two in Decatur County, Georgia, and two in Gadsden County, Florida. Symptoms observed were plant stunting, reduced leaf size, yellow leaf margins, and mottling. The incidence of symptomatic plants was less than 1% in all fields examined. In most cases, symptoms were observed only on the upper portion of plants, suggesting these plants had been infected by secondary spread from an unknown source. Nuclear inclusions characteristic of geminiviruses were observed by light microscopy in leaf tissue from symptomatic plants (1). To identify the geminivirus, total DNA from infected plants was extracted from six symptomatic tomato plants (two from Georgia and four from Florida) for polymerase chain reaction (PCR; J. E. Polston, personal communication). DNA was amplified with geminivirus DNA A degenerate primer set PAL1v1978 and PAR1c496 (2) from these extracts in addition to extracts from a known TYLCV-infected, a tomato mottle virus (ToMoV)-infected, and a healthy tomato plant. A PCR product of 1.4 kb was obtained from plants with TYLCV-like symptoms, while a 1.4-kb product and a 1.1-kb product were obtained from extracts of the known TYLCV-infected and ToMoV-infected tomato plants, respectively. No PCR product was obtained from extracts of healthy tomato plants. The 1.4-kb PCR products from one Georgia sample and one Florida sample were compared with those of TYLCV and ToMoV by restriction enzyme (RE) digestion with EcoRI and ClaI. The RE pattern of the 1.4-kb fragment from both samples was identical to the RE pattern of TYLCV and different from that of ToMoV. Adult and immature whiteflies collected from the fields where TYLCV was found were identified as Bemisia tabaci, the vector of TYLCV, but the biotype was not established. This report of TYLCV in south Georgia and north Florida extends the geographic range of TYLCV in the U.S. northward approximately 100 km. Georgia is the second state in which TYLCV was found since its initial detection in south Florida in July 1997 (J. E. Polston, personal communication). Monitoring of silverleaf whitefly populations and detection of TYLCV on alternate hosts will continue in order to estimate the potential impact of this virus on south Georgia and north Florida agriculture.

References: (1) R. G. Christie and J. R. Edwardson. Plant Dis. 70:273, 1986, (2) M. R. Rojas et al. Plant Dis. 77:340, 1993.
Fungicide Application for Late Blight Management: A Boom Attached to a Center Pivot Irrigation System
Authors: Geary Brad , Johnson Dennis A. , Hamm Philip B. , Cummings Thomas F.
Published: May 2007

Chlorothalonil was applied to commercial potato fields of cvs. Russet Norkotah and Russert Burbank in replicated trials through either a center-pivot irrigation system or a spray-boom-attached-to-the-pivot system. Water rates were 26,192 and 675 liters/ha for the center pivot and attached boom, respectively. Three crop canopy levels were sampled within 2 h and again after 6 days following fungicide applications made at 7-day intervals. Efficacy of the two application methods was tested by inoculation of individual excised leaves with an isolate of strain US-1 or US-8 of Phytophthora infestans and by chemical residue analysis. Severity of late blight did not differ between the two fungicide application methods 2 h after application but, after 6 days, disease severity was significantly less on leaves where chlorothalonil was applied by the attached boom. Fungicide residues were three times higher on leaves where chlorothalonil was applied by the attached boom than with the center-pivot system. Significantly more disease occurred on fungicide-treated and non-treated leaves inoculated with the US-8 than the US-1 strain. Severity of late blight on inoculated leaves was inversely related to the amount of chlorothalonil residue on leaves.
Evidence of Cross-Protection Between Beet Soilborne Mosaic Virus and Beet Necrotic Yellow Vein Virus in Sugar Beet
Authors: Mahmood T. , Rush C. M.
Published: May 2007

A high degree of reciprocal cross-protection occurred in sugar beets between beet soilborne mosaic virus (BSBMV) and beet necrotic yellow vein virus (BNYVV) in greenhouse experiments. The incidence of cross-protection depended on the interval between inoculations with protecting and challenging virus; longer inoculation intervals enhanced the incidence of cross-protection. Cross-protection was most effective when the inoculation interval was between 5 and 10 days, a period during which virus accumulated to a maximum level in plants singly infected with BSBMV or BNYVV. Results obtained by enzyme-linked immunosorbent assay (ELISA) and Western blotting were consistent and indicated that cross-protection affected viral capsid protein accumulation. RNA of both protecting and challenging viruses was detected in doubly infected plants by using reverse transcription-polymerase chain reaction (RT-PCR), indicating that RNA of the challenge virus was present in protected plants, but capsid protein was undetected by serological tests. BSBMV is a closely related but serologically distinct virus that provides an excellent system for studies of cross-protection with BNYVV.
Identification of Fusarium oxysporum f. sp. basilici Isolated from Soil, Basil Seed, and Plants by RAPD Analysis
Authors: Chiocchetti Annalisa , Ghignone Stefano , Minuto Andrea , Gullino M. Lodovica , Garibaldi Angelo , Migheli Quirico
Published: May 2007

Fifty-two isolates of Fusarium oxysporum, obtained from infected basil plants, seed, flower residues, and soil from different growing areas in Italy and Israel, were analyzed by random amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR), coupled to a DNA extraction protocol from colonies grown on Fusarium-selective medium. In a pathogenicity assay, 35 isolates caused 32 to 92% disease on seedlings of the highly susceptible basil cultivar Fine verde, while 17 isolates were nonpathogenic on basil. Thirty of the F. oxysporum f. sp. basilici isolates obtained from soil or wilted plants gave identical amplification patterns using 31 different random primers. All tested primers allowed clear differentiation of F. oxysporum f. sp. basilici from representatives of other formae speciales and from nonpathogenic strains of F. oxysporum. RAPD profiles obtained from DNA of isolates extracted directly from cultures grown on Fusarium selective medium were identical to those obtained from DNA extracted from lyophilized mycelia.
A New Root and Crown Rot Disease of Heath in California Caused by Cylindrocladium pauciramosum
Authors: Koike S. T. , Henderson D. M. , Crous P. W. , Schoch C. L. , Tjosvold S. A.
Published: May 2007

Heath (Erica capensis Salter) is a woody, evergreen plant used in Cali-fornia as a landscape shrub or ground cover. In 1997, a new root and crown disease was found in commercial nursery plantings of potted heath. A similar disease was found in 1998 on heath transplants being grown as liners. In both situations, roots were necrotic and crown tissue turned brown. Affected plants became gray-green in color, withered, and died. A Cylindrocladium species was consistently isolated from roots, crowns, and lower stems of symptomatic plants. Isolates were characterized by having penicillate conidiophores terminating in obpyriform to broadly ellipsoidal vesicles. Conidia were hyaline, 1-septate, straight with rounded ends, (30-) 45 to 55 (-60) × (3.5-) 4 to 5 μm, placing it in the Cylindrocladium candelabrum Viégas species complex. Ten single-conidial isolates produced perithecia with viable progeny of Calonectria pauciramosa C.L. Schoch & Crous when mated on carnation leaf agar with tester strains of Cylindrocladium pauciramosum C.L. Schoch & Crous (1). Matings with tester strains of all other species in this complex proved unsuccessful. Pathogenicity of 8 representative isolates was confirmed by applying 3 ml of a conidial suspension (3.0 × 105 conidia per ml) to the crowns of potted, 6-month-old, rooted heath cuttings that were subsequently maintained in a greenhouse (23 to 25°C). After 2 weeks, plant crowns and roots developed symptoms similar to those observed in the field, and plants later wilted and died. C. pauciramosum was reiso-lated from all plants. Control plants, which were treated with water, did not develop any symptoms. The tests were repeated and the results were similar. This is the first report of C. pauciramosum as a pathogen of heath, and the first record of this pathogen from North America.

Reference: (1) C. L. Schoch et al. Mycologia 91:286, 1999.
Isolation of Trichoderma harzianum Th2 from Commercial Mushroom Compost in Spain
Authors: Hermosa M. R. , Grondona I. , Monte E.
Published: May 2007

Trichoderma spp. are associated with green mold of mushrooms. This fungal disease has caused severe losses in mushroom production in countries such as Ireland, the United Kingdom, Canada, and the United States. This disease is caused by two biotypes of T. harzianum (Th2, Europe; Th4, North America) (1,2). Both biotypes have not been detected in mushrooms or other material in Spain previously. However, during 1998, green mold was detected at facilities dedicated to produce compost, as well as in facilities used to produce Agaricus bisporus (Lange) Imbach. Three compost samples were isolated from commercial bags with mushroom substrate and three more samples were taken from mushroom yards. Several spores were isolated by the dilution plate method. Initial identification of the pathogenic fungi was made by examining cultures grown on potato dextrose agar. Morphological characteristics of all isolates coincided with the description of T. harzianum (3). The following amounts of CFU per g were found in commercial compost samples: 1.2 × 108, 5.5 × 107, and 1.4 × 107 per g; whereas 3 × 108, 12.4 × 107, and 2.2 × 106 were obtained from mushroom yards. The fragment containing the internal transcribed spacer (ITS1) was amplified and sequenced for each of the six samples obtained. The ITS1 sequence (201 bp) was identical in all samples, and the sequence was aligned, with Clustal W, with Th2 and Th4 biotype sequences of the EMBL data base. The ITS1 sequence showed 0.55% divergence from Th2 isolates and more distance, 3.3%, with Th4 isolates. The ITS1 sequence obtained with all Spanish samples studied, EMBL accession number AJ1321550, was identical to that described for the Irish isolate Th2I (#63), with accession number U78880 in the EMBL data base (1). This is the first description of the Th2 biotype in Spain.

References: (1) M. D. Ospina-Giraldo et al. Mycologia 90:76, 1998. (2) D. L. Rinker et al. Mushroom World 8:71, 1997. (3) D. A. Seaby. Plant Pathol. 45:905, 1996.