bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of Sampling Strategies for Determining Incidence of Cranberry Fruit Rot and Fruit Rot Fungi
Authors: McManus P. S. , Caldwell R. W. , Voland R. P. , Best V. M. , Clayton M. K.
Published: May 2007

Two sampling strategies were compared and sources of variability in the sampling protocols analyzed to optimize sampling methods for studies of cranberry fruit rot that occurs in the field (i.e., field rot). For the first method, fruit were dry picked by hand from randomly assigned quadrats; for the second method, fruit were scooped from harvest floodwaters. Rot incidence, which ranged from 1.8 to 9.7%, did not differ significantly between upland and lowland sites or, in general, between dry-picked and wet-harvested samples. There were no consistent differences between upland and lowland sites in the frequency of isolation of any fungus from either rotten or sound fruit. The incidence of certain saprophytic and soilborne fungi was greater in wet-harvested compared with dry-picked fruit. In general, rot incidence and incidence of various fungal taxa isolated from fruit varied more among samples within sites than among sites. Site type (i.e., upland or lowland) was never a major source of variability. These findings suggest that if the goal were to assess the occurrence of cranberry fruit rot within a region, intensive within-site sampling would be necessary, but site type would not be an important consideration, at least in Wisconsin, where this study was conducted.
First Report of Cucurbit yellow stunting disorder virus in Commercial Cucumber Greenhouses in France
Authors: Desbiez C. , Lecoq H. , Girard M. , Cotillon A. C. , Schoen L.
Published: May 2007

In autumn 2001, severe yellowing symptoms were observed on greenhouse-grown cucumbers near Perpignan (southern France). Leaf samples were collected from two sites where plants displayed symptoms ranging from limited yellowing of the older leaves to severe, complete yellowing of the whole plant. Cucurbit aphid-borne yellows virus, a polerovirus that causes similar symptoms was not detected in doubleantibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) using a specific antiserum. Total RNA was extracted from fresh leaf tissues and used in reverse transcription-polymerase chain reaction (1) with primers specific for two whitefly-borne viruses also inducing yellows and occurring in the Mediterranean basin (1): Beet pseudo yellows virus (BPYV, genus Closterovirus) transmitted by Trialeurodes vaporariorum (West.) and Cucurbit yellow stunting disorder virus (CYSDV, genus Crinivirus) transmitted by Bemisia tabaci (Genn.). No BPYV was detected in this survey, but CYSDV was present in all samples. In subsequent surveys conducted in the spring and summer of 2002, BPYV and CYSDV were detected, sometimes in mixed infections, in samples collected from the same region. The complete CYSDV coat protein gene was amplified by PCR using specific primers (2), yielding the expected-size fragment of 756 bp. The French isolate (GenBank Accession No. AY204220) shared 99.6 to 100% nucleotide sequence identity in the sequenced CP fragments (700 nt) with isolates of the most common, highly homogenous subgroup of CYSDV that has emerged recently in the Middle East, southwestern Europe (Spain and Portugal), United States, and Morocco (2). To our knowledge, this is the first report of CYSDV in France and it shows the threat represented by the current emergence of B. tabaci-transmitted viruses.

References: (1) I. C. Livieratos et al. Plant Pathol. 47:362, 1998. (2) L. Rubio et al. J. Gen. Virol. 82:929, 2001.
Characterization ofVerticillium albo-atrumField Isolates Using Pathogenicity Data and AFLP Analysis
Authors: Radišek Sebastjan , Jakše Jernej , Simončič Andrej , Javornik Branka
Published: May 2007

Since 1997, hop wilt induced by a virulent pathotype of Verticillium albo-atrum has caused considerable economic losses in hop fields in Slovenia. In all, 20 isolates of V. albo-atrum, including 12 from plants affected with the lethal form (PG2) of hop wilt, 6 from plants with the mild form (PG1), 1 from cucumber, and 1 from petunia, as well as 1 isolate of V. dahliae each from hop and green pepper, were analyzed by amplified fragment length polymorphism (AFLP). Differences in the virulence of hop isolates were confirmed by pathogenicity tests on hop cultivars. The AFLP method was optimized for analysis of these fungi and 7 of 39 primer combinations tested were used for the analysis of polymorphism among isolates. Cluster analysis of AFLP data divided the isolates into two, well-separated V. albo-atrum and V. dahliae clusters, confirming that the two species are genetically distinct. Within the V. albo-atrum cluster, isolates were further separated into two distinct groups: the A1 group contained PG1 hop pathotype and cucumber and petunia isolates, and the A2 group all hop isolates of the PG2 pathotype. Minor genetic variation was detected within pathotype-associated AFLP groups, but the clear separation of V. albo-atrum hop isolates according to their level of virulence shows genetic differentiation among hop V. albo-atrum pathotypes.
Populations of Botrytis cinerea and Penicillium spp. on Pear Fruit, and in Orchards and Packinghouses, and Their Relationship to Postharvest Decay
Authors: Lennox Cheryl L. , Spotts Robert A. , Cervantes Louis A.
Published: May 2007

The aims of this study were to examine the sources and population sizes of Botrytis cinerea and Penicillium spp. in ‘d'Anjou’ pear orchards, packinghouses, and storage, and to determine the relationship between population sizes and postharvest decay. Densities of B. cinerea ranged from nondetectable to 4.0 CFU/cm2 on fruit, nondetectable to 3.1 CFU/liter in orchard air, and nondetectable to 1,167 CFU/g in orchard litter. The majority of packinghouse air and orchard soil samples collected yielded no B. cinerea inoculum. Densities of Penicillium spp. ranged from nondetectable to 2.7 CFU/cm2 on pear fruit, nondetectable to 3.13 CFU/liter in orchard air, nondetectable to 11.8 CFU/liter in packingline air, nondetectable to 3.9 CFU/liter in cold-storage air, 38 to 431 CFU/g in orchard soil, and 131 to 1,128 CFU/g in orchard litter. The mean incidence of gray mold in stored d'Anjou pear fruit ranged from 0.7 to 10.7%. Incidence of blue mold ranged from 0 to 16.5%. Significant positive correlations were observed between decay and fruit surface populations of B. cinerea and Penicillium spp. In conclusion, inoculum levels of these important postharvest pathogens in orchard and packinghouse air, and orchard soil and litter, cannot be used as indicators of postharvest decay; whereas the inoculum level on fruit surfaces may be a useful predictor of decay.
First Report of a Leaf Blight of Onion Caused by Xanthomonas spp. in Georgia
Authors: Sanders F. H. , Langston D. B. , Brock J. H. , Gitaitis R. D. , Curry D. E. , Torrance R. L.
Published: May 2007

In October of 2001 and 2002, a leaf blight was reported affecting Vidalia onion (Allium cepa) cvs. Pegasus and Sweet Vidalia, respectively, in one field each. Lesions on onion seedlings began as a water-soaked, tip dieback that gradually blighted the entire leaf. Symptoms on onion transplants appeared as elongated, water-soaked lesions that typically collapsed at the point of initial infection. In both cases, disease was very severe on seedlings, and disease incidence was 50% or more in both fields. Warm temperatures combined with overhead irrigation and above average rainfall likely enhanced the severity and spread of disease. Disease was not detected on more mature onions once cool, dry conditions occurred later in the season, and no significant economic loss occurred. Seed was tested from seed lots of the aforementioned cultivars and Xanthomonas spp. were not found. Diseased tissue was macerated in sterile, phosphate-buffered saline, and 10 μl of the resulting suspension was streaked on nutrient agar plates. Yellow-pigmented, gram-negative, rod-shaped bacteria were isolated routinely from diseased tissue. Bacteria were catalase-positive, cellulolytic, oxidase-negative, amylolytic, proteolytic, and utilized glucose in an oxidative manner. Analysis of whole cell, fatty acid methyl esters (FAME) using the Microbial Identification System (MIS, Sherlock version 3.1; MIDI, Inc., Newark, DE) identified four representative strains of the bacterium as a pathovar of Xanthomonas axonopodis (similarity indices 0.75 to 0.83). Known Xanthomonas spp. from onion from Colorado and Texas (1,2) had similar FAME profiles when analyzed by the MIDI system. Onion plants were grown under greenhouse conditions for 2 months and inoculated by injecting the base of a quill with 1.0 ml of bacterial suspensions (1 × 107 CFU ml-1) of the Xanthomonas sp. isolated from Georgia, and negative controls were inoculated with 1 ml of sterile water. Disease symptoms developed on plants inoculated with bacterial suspensions in 4 to 7 days and Xanthomonas sp. was isolated from the lesions produced. Disease symptoms occurred when the same suspension was sprayed on onion foliage. No symptoms occurred on plants inoculated with 1 ml of sterile water. To our knowledge, this is the first report of Xanthomonas spp. affecting Vidalia onions.

References: (1) T. Isakeit et al. Plant Dis. 84:201, 2000. (2) H. F. Schwartz and K. Otto. Plant Dis. 84:922, 2000.
First Report of Anthracnose of Gaultheria procumbens Caused by Colletotrichum gloeosporioides
Authors: Elmhirst J. F. , Hudgins E. J.
Published: May 2007

In 2001, a stem canker and dieback associated with a Colletotrichum sp. was observed on Gaultheria procumbens L. (wintergreen) seedlings grown from seed in soilless potting mix at four commercial nurseries in coastal British Columbia, Canada. Black, water-soaked lesions developed into tan cankers girdling stems and petioles, and a black rot extended into the base of leaves. In 2002, a Colletotrichum sp. was isolated from similar stem cankers from wintergreen plants. One flat of healthy, 13-week-old seedlings of G. procumbens (one- to three-leaf stage; approximately 380 seedlings per flat) was inoculated with a mycelial and spore suspension of one of the Colletotrichum sp. isolates at 108 CFU/ml using a hand atomizer. The flat was covered with black plastic for 24 h after inoculation and maintained in a growth chamber at 22°C with overhead watering. After 7 days, 98% of seedlings in the inoculated flat were necrotic with abundant sporulation of the Colletotrichum fungus on stem and petiole lesions. Plants in noninoculated flats remained healthy. Reisolation of the fungus from symptomatic tissues confirmed the causal agent to be Colletotrichum gloeosporioides (Penz.) Penz. & Sacc. in Penz, based on morphology (1,2) and polymerase chain reaction (PCR) using the species-specific primer CgInt (3). Cylindrical, hyaline, aseptate conidia measuring 16 to 20 × 4 to 6 μm were produced in acervuli with setae. Perithecia of the teleomorph, Glomerella cingulata, observed on the plants and in culture, measured 100 to 128 μm in diameter and contained acsi measuring 56 to 60 × 8 to 10 μm. Ascospores were hyaline, unicellular, slightly curved, and measured 18 to 20 × 4 to 6 μm. Subsequently, a single-spore isolate of the fungus was used to inoculate 21-week-old seedlings in the greenhouse as described above. Four inoculated and four noninoculated half-flats containing an average of 160 seedlings each were randomized on the greenhouse bench and maintained at 22°C with daily overhead misting. Stem and petiole cankers appeared on 65.1% of inoculated seedlings at 10 days after inoculation (mean of four inoculated half-flats); increasing to 90.5% at 14 days. At 14 days, 5.9% of seedlings in four noninoculated half-flats were also symptomatic, possibly from spore contamination as a result of overhead watering. To our knowledge, this is the first confirmation of the causal agent of wintergreen seedling death in seed propagation nurseries in British Columbia.

References: (1) J. E. M. Mordue. Glomerella cingulata. No. 315 in: Descriptions of Pathogenic Fungi and Bacteria. CMI, Kew, Surrey, UK, 1971. (2) B. C. Sutton. The Coelomycetes. CAB International Publishing, New York, 1980. (3) P. Talhinhas et al. Phytopathology 92:986, 2002.
Development of Fungicide Cross Resistance inHelminthosporium solaniPopulations from California
Authors: Cunha M. G. , Rizzo D. M.
Published: May 2007

Helminthosporium solani populations on potato from the Tulelake area in California frequently have been exposed to thiophanate-methyl but not benomyl. Assessment of three H. solani populations found that 182 of 238 isolates were resistant to both thiophanate-methyl and benomyl and 56 isolates were sensitive to both fungicides. None of the isolates exhibited a differential reaction to the two fungicides. The effective concentrations that reduced growth by 50% for resistant isolates of H. solani were approximately 400 mg/liter for thiophanate- methyl and 35 mg/liter for benomyl. Two point mutations were detected in the β-tubulin gene from H. solani isolates from California; however, only the mutation at the 455-nucleotide position (codon 198) was strongly associated with thiophanate-methyl resistance. This mutation led to a change of glutamic acid to alanine at codon 198. Independent of fungicide resistance, a mutation at the 836-site was detected in all California isolates. A polymerase chain reaction (PCR)-based restriction fragment length polymorphism (RFLP) assay was used to identify thiophanate-methyl resistance in H. solani; resistant isolates exhibited two DNA fragments of 390 and 482 bp, whereas sensitive isolates had three fragments of 62, 390, and 420 bp. Every isolate assigned either as resistant or sensitive by the PCR-based RFLP assay correlated 100% with the results of the assay on fungicide-amended medium.
Temperature and Wetness-Duration Requirements for Grape Leaf and Cane Infection by Phomopsis viticola
Authors: Erincik O. , Madden L. V. , Ferree D. C. , Ellis M. A.
Published: May 2007

In 1998 and 1999, controlled-environment studies were conducted in growth chambers to determine the temperature and wetness-duration parameters required for leaf and cane infection of grape by Phomopsis viticola. Greenhouse-grown ‘Catawba’ (Vitis labrusca) and ‘Seyval’ (French hybrid) grapes were inoculated with P. viticola and incubated at constant temperatures of 5, 10, 15, 20, 25, 30, and 35°C and at wetness durations of 5, 10, 15, and 20 h for each temperature. Data from each cultivar were analyzed by nonlinear regression analysis to determine the relationship between disease severity and temperature and wetness duration. A generalized form of the Analytis Beta model was found to provide the best fit to the data. Disease severity on leaves and canes increased with increasing wetness duration at most temperatures. Minimum and maximum temperatures for infection were around 5 and 35.5°C, respectively. Optimum temperatures for leaf and cane infection were between 16 and 20°C. In the 2000 and 2001 growing seasons, the generalized Beta model was validated in ‘Catawba’ and ‘Seyval’ vineyards by inoculating vines during natural rain events. Average temperature and hours of wetness for each event and inoculation were recorded and used in the model equation to predict disease severity on leaves and internodes. Correlation coefficients between observed disease severities following field inoculations and predicted disease severities for both cultivars were between 0.71 and 0.81 and always significant (P < 0.01). These results indicate that the model reliably predicted leaf and cane infection on both cultivars over a wide range of wetness durations and temperatures. The model may be useful in developing disease-forecasting systems for Phomopsis cane and leaf spot on grapes.
Etiology of Phytophthora drechsleri and P. nicotianae (=P. parasitica) Diseases Affecting Floriculture Crops
Authors: Lamour K. H. , Daughtrey M. L. , Benson D. M. , Hwang J. , Hausbeck M. K.
Published: May 2007

Phytophthora nicotianae and P. drechsleri isolates (n = 413) recovered from eight floricultural hosts at 11 different production sites were described according to compatibility type, resistance to mefenoxam, and amplified fragment length polymorphism (AFLP) profiles. Sample sizes ranged from 2 to 120. In all cases, isolates recovered from a single facility had the same compatibility type and resistance to mefenoxam. AFLP analysis indicated that six clonal lineages of P. nicotianae and two clonal lineages of P. drechsleri were responsible for the 11 epidemics and that isolates recovered from the same facility were identical. A single clone of P. nicotianae was recovered from snapdragons at two field production sites in the southeastern United States receiving seedlings from the same source. This clone persisted at one site from 2000 to 2001. Another clone was recovered from verbena at three separate greenhouse facilities where one facility was supplying verbena to the other two. These results suggest that asexual reproduction of these pathogens plays an important role in epidemics and spread may occur between distant facilities via movement of plants.
First Report of Meloidogyne incognita Infecting Spinach in Southern Spain
Authors: Castillo P. , Jiménez-Díaz R. M.
Published: May 2007

Severe plant yellowing and decline were recently observed in two commercial fields of spinach (Spinacia oleracea cv. Polka) in Encinarejo (Córdoba), southern Spain. Disease surveys revealed severe infections of main and feeder roots and a large soil population of the southern root-knot nematode Meloidogyne incognita. The nematode population was extracted and quantified from soil and root samples according to Barker (1) and identified by female perineal pattern, phenotype esterases, and host-differential test (3,4). M. incognita was found in 100% of soil samples and 85.7% of root samples with nematode population densities ranging from 44 to 378 eggs and second-stage juveniles (J2s) per 100 cm3 of soil and 162 to 725 eggs and J2s per 5 g of fresh roots. Infected roots showed large, regular galls on root tips and also along the main root axis and secondary feeder roots. Galling of root tips prevents further root growth into deeper soil layers and induced proliferation of secondary roots. The severe infections in roots of spinach suggest that parasitism of spinach roots by the nematode must contribute to stunting, yellowing, and decline of spinach as previously reported (2). To our knowledge, this is the first report of M. incognita infecting spinach in Spain.

References: (1) K. R. Barker. Nematode extraction and bioassays. Page 19 in: An Advanced Treatise on Meloidogyne. Vol. II, Methodology. K. R. Barker, C. C. Carter, and J. N. Sasser, eds. North Carolina State University Graphics, Raleigh, 1985. (2) J. C. Correll et al. Plant Dis. 78:653, 1994. (3) P. R. Esbenshade and A. C. Triantaphyllou. J. Nematol. 22:10, 1990. (4) K. M. Hartman and J. N. Sasser. Identification of Meloidogyne species on the basis of differential host test and perineal pattern. Page 69 in: An Advanced Treatise on Meloidogyne. Vol. II, Methodology. K. R. Barker, C. C. Carter, and J. N. Sasser, eds. North Carolina State University Graphics, Raleigh, 1985.
First Report of Mundulla Yellows on Eucalyptus spp. Outside Australia
Authors: Hanold D. , Randles J. W.
Published: May 2007

Mundulla Yellows (MY) is a newly recognized lethal dieback of unknown etiology affecting Eucalyptus spp. in Australia (1). Progression of symptoms, unlike other disorders described for eucalypts, starts as foliar interveinal chlorosis on one branch followed by branch dieback advancing toward the main trunk. Epicormic shoots with symptomatic leaves typically develop proximal to the dying zone. Continuing dieback leads to tree death in 5 to 20 years. MY trees occur singly or in small foci and do not recover even if affected branches are removed. MY-like symptoms developed on seedlings grafted with bark patches from MY trees (1). There is no evidence for a fungal, phytoplasma, or other bacterial etiology. In a search for a putative virus-like agent we have identified an electrophoretic pattern (2) of several single-stranded RNAs with apparent size of 200 to 600 nt that is consistently associated with MY and absent from disease-free trees (unpublished). The RNAs are not yet characterized, but the pattern can be used as a preliminary confirmatory “fingerprint” for MY. We report here that MY-like symptoms occur in southern Spain and the Spanish island of Ibiza. RNA fingerprints closely resembling those of MY, were detected in symptomatic trees (4 of 4 of E. camaldulensis and 1 of 1 of E. globulus) from Valencia, Spain. MY therefore, appears not to be limited to Australia.

References: (1) D. Hanold et al. Landscope 17(4):41, 2002. (2) J. W. Randles. Strategies for implicating virus-like pathogens as the cause of diseases of unknown etiology. Pages 315–332 in: Diagnosis of Plant Virus Diseases, CRC Press, Boca Raton, FL, 1993.
First Report of Leaf and Sheath Spot Caused by Rhizoctonia zeae Affecting Panicum tennesseense in Rhode Island
Authors: Mitkowski N. A.
Published: May 2007

Panicum tennesseense Ashe is a perennial, coarse-textured, cool-season grass (similar in appearance to many warm-seasoned grasses), which grows in the southern coastal areas of New England and is commonly found in home lawns, roadsides, and meadows. In August 2002, a large stand of P. tennesseense with significant leaf spotting was identified in Washington County, RI. Lesions were excised, surface sterilized with 0.6% sodium hypochlorite, and plated on one-half-strength potato dextrose agar (PDA). Cultures were incubated at 25°C, and mycelia quickly covered plates within 3 days. After 2 weeks in darkness, plates were covered with white, aerial mycelium. When placed under near-UV light, no aerial mycelium was produced, and mycelia were a salmon color. After 5 weeks, separate, spherical, 0.5-mm-diameter beige sclerotia were produced submerged throughout the media and turned red within a few days. Sclerotia were not produced in the absence of near-UV light. Spores were not produced, and right-angled branching, characteristic of Rhizoctonia spp., was observed. Monilioid hyphae were also produced in culture. At the optimal growth temperature of 32°C, mycelia grew an average of 33.6 mm/day. Cells were stained using safranin, and the number of nuclei observed within young hyphal cells was five or seven. On the basis of the described mycelial and sclerotial characterisitics, the isolated fungus was identified as Rhizoctonia zeae (1,2). To demonstrate pathogenicity, plugs of isolated fungi were cut from PDA plates, placed on leaf blades at the junction with leaf sheaths, and incubated in a greenhouse humidity chamber at an average temperature of 32°C and 80% humidity. After 3 days, significant disease was observed and included blighting of newly emerged shoots, blighting and spotting on leaf sheaths, and severe spotting on leaf lamina. Whereas Rhizoctonia solani has been reported as a pathogen on P. tennesseense, to our knowledge, this is the first report of R. zeae induced leaf and sheath spot on this host (1).

References: (1) H. Couch. Diseases of Turfgrasses. Krieger Publishing Co., Malabar, FL, 1995. (2) B. Sneh et al. Identification of Rhizoctonia species. The American Phytopathological Society, St. Paul, MN. 1991.
Development of a Weather-Based Advisory Program for Scheduling Fungicide Applications for Control of White Rust of Spinach
Authors: Sullivan M. J. , Damicone J. P. , Payton M. E.
Published: May 2007

Weather-based advisory programs were developed and evaluated for timing of fungicide applications to control white rust of spinach (Spinacia oleracea) in three field trials using a susceptible cultivar. The advisory programs were based on previous studies that defined periods of temperature (T) and wetness (relative humidity ≥90%, W) that favored disease development. The protectant fungicides mancozeb or maneb (ethylene bisdithiocarbamates; EBDCs) and the systemic fungicide azoxystrobin were applied after 3, 6, 12, 24, and 36 cumulative hours of wetness weighted by temperature (T*W). T*W programs were compared with an advisory program based on 12 h of continuous wetness (12-h W), a 7-day calendar program, and a nonsprayed control treatment. Except for the 3-h T*W program, the number of fungicide applications per trial was reduced for all advisory programs compared with the 7-day program. Averaged over the three trials, applications were reduced from 2.7 per trial for the 6-h T*W program to 3.7 per trial for the 36-h T*W and the 12-h W programs. For the EBDC fungicides, all advisory programs except the 36-h T*W and 12-h W programs reduced incidence and severity of white rust compared with the nonsprayed control. Disease incidence and severity for the 3-h and 6-h T*W programs did not differ from the 7-day program. Compared with the EBDC fungicides, azoxystrobin resulted in reduced disease incidence for each of the spray programs and reduced disease severity for all spray programs except the 7-day program. For azoxystrobin, all advisory programs reduced disease incidence and severity compared with the nonsprayed control. Incidence and severity of white rust did not differ from the 7-day program for the 3-h, 6-h, and 12-h T*W programs. Based on reductions in the number of fungicide applications and the level of disease control, the 6-h and 12-h T*W programs were most efficient advisory programs for the EBDC fungicides and azoxystrobin, respectively.
Effect of Chemical Defoliation, Irrigation Water, and Distance From the Pivot on Late Blight Tuber Rot in Center-Pivot Irrigated Potatoes in the Columbia Basin
Authors: Johnson Dennis A. , Martin Mel , Cummings Thomas F.
Published: May 2007

Chemical desiccation of potato foliage 2 to 3 weeks prior to harvesting tubers is commonly recommended to reduce late blight tuber rot. Observations in commercial fields indicate that this practice may not be needed to manage tuber rot in the semiarid environment of the Columbia Basin. Potatoes in this region are mostly grown under center pivot irrigation, and a relatively high volume of irrigation water is often delivered near the pivot in center-pivot irrigated fields. This study evaluated the effect of chemical desiccation of potato foliage on late blight tuber rot and quantified the incidence of late blight tuber rot in relation to distance from the pivot and the amount of irrigation water applied in center-pivot irrigated fields. Potato foliage was chemically desiccated or not desiccated within 41 to 76 m of the pivot of center-pivot irrigated potato fields 2 to 3 weeks before harvest in replicated plots in five field trials during 3 years. Incidence of late blight tuber rot did not differ significantly between the defoliated and nondefoliated plots in all five trials. Incidence of tuber rot significantly increased as amount of irrigation water applied increased, and was significantly greater within 30 m of the center pivot than at greater distances in two trials in 1998 and two trials in 1999. Tuber rot did not develop in a fifth trial in 2000 where a water gradient did not occur among the plots. The largest percentage of tubers infected with late blight was observed within 30 days of harvest at a storage temperature of 9°C. Chemical desiccation of potato foliage in the semiarid environment of the Columbia Basin was not beneficial in reducing late blight tuber rot, but growing potatoes within 30 m of the pivot will likely increase the number of infected tubers going into storage.
Histology of White Pine Blister Rust in Needles of Resistant and Susceptible Eastern White Pine
Authors: Jurgens Joel A. , Blanchette Robert A. , Zambino Paul J. , David Andrew
Published: May 2007

White pine blister rust, Cronartium ribicola, has plagued the forests of North America for almost a century. Over past decades, eastern white pine (Pinus strobus) that appear to tolerate the disease have been selected and incorporated into breeding programs. Seeds from P. strobus with putative resistance were collected from Oconto River Seed Orchard, Nicolet National Forest, WI. Seedlings were grown for 5 months and artificially inoculated with basidiospores of C. ribicola in two replicated greenhouse experiments. Needles from infected seedlings were fixed, sectioned, and stained with a variety of histological reagents, and rate of mortality for the remaining seedlings was monitored. The most susceptible families suffered 50% mortality in approximately half the time of the more resistant families. Extensive inter- and intracellular hyphae were observed in needles from seedlings of susceptible families, whereas hyphal proliferation was restricted in needles of resistant seedlings. Needles from resistant families had pronounced responses to infection. Phenolics, observed with phloroglucinol-HCl staining, were deposited around infection sites where dense mycelial masses were present. Abnormal host cell growth and rapid cell death in the immediate area of infection were also observed in some eastern white pine families.
Pathogenicity of a Novel Biotype of Limonomyces roseipellis in Tall Fescue
Authors: Burpee L. L. , Mims C. W. , Tredway L. P. , Bae J. , Jung G.
Published: May 2007

An unusual and undescribed foliar blight of tall fescue was observed in a home lawn and in turf grass research plots near Griffin, GA in May and June, 2000 and 2001. Isolation from lesions yielded mycelium of a basidiomycete with hyphal characteristics (binucleate cells, absence of clamp connections) associated with Laetisaria and Limonomyces spp. Isolates from blighted tall fescue and an isolate of Limonomyces roseipellis formed a clade distinct from isolates of Laetisaria fuciformis based on ribosomal DNA sequences. These data, in conjunction with cultural morphology, indicate that the basidiomycete from tall fescue represents a biotype of Limonomyces roseipellis that lacks clamp connections. In a controlled environment, isolates of the biotype induced foliar blight in the fescue cvs. Kentucky 31 and Rebel III. Histological observations revealed that the fungus colonized leaf surfaces as branched hyphae and aggregated hyphal strands. Penetration occurred via stomatal pores on the abaxial leaf surface. Colonization of leaf tissues was inter- and intracellular, with no evidence of papilla formation in response to invading hyphae. The name “cream leaf blight” is proposed for this new disease of tall fescue.
First Report of Association of Tomato leaf curl virus-New Delhi with Yellow Mosaic Disease of Luffa cylindrica in India
Authors: Sohrab S. S. , Mandal B. , Pant R. P. , Varma A.
Published: May 2007

Sponge gourd (Luffa cylindrica), an important cucurbitaceous vegetable in India, is affected by a disease (2) causing yellow spots on newly emerged leaves, mosaic, mild leaf curling and distortion, small leaves, and misshapen fruits. Nearly 100% of sponge gourd plants were symptomatic in Delhi. Geminivirus-like particles were observed with electron microscopy of uranyl acetate-stained leaf-dip preparations of the diseased plants collected from experimental fields at the Indian Agricultural Research Institute in New Delhi during May and June of 2002. The virus was transmitted by the whitefly (Bemisia tabaci) to sponge and ridge gourd (L. acutangula) after an acquisition and inoculation access period of 24 h each. Whitefly-inoculated plants produced typical yellow mosaic symptoms and contained geminate particles. Nucleic acid extracted from the field-infected and experimentally infected plants hybridized with 32P-labeled probe to DNA-A of Indian cassava mosaic virus, suggesting association of a begomovirus. The viral DNA, isolated by the alkali denaturation method (1) from the experimentally infected sponge gourd plants, was cloned in pBS SK+ at the EcoRI site. A clone with an insert of 2,658 bp was sequenced (GenBank Accession Nos. AJ557219, AJ555488, and AY309957) which shared 89.6 to 95.1% identity with the DNA-A of different strains of Tomato leaf curl virus-New Delhi (ToLCV-NDe). The highest sequence identity (95.1%) was with the severe strain of ToLCV-NDe (GenBank Accession No. U15015). The data suggest that the begomovirus associated with the yellow mosaic disease of L. cylindrica in India is a putative strain of ToLCV-NDe.

Reference: (1) K. M. Srivastava et al. J. Virol. Methods 51:297, 1995. (2) A. Varma and B. K. Giri. Virus diseases. Pages 225–245 in: Cucurbits. N. M. Nayar and T. A More, eds. Oxford and IBH Publishing House Private Ltd., New Delhi, India, 1998.
Occurrence of the Root-Knot Nematodes Meloidogyne incognita and M. hapla in Slovenia
Authors: Širca S. , Urek G. , Karssen G.
Published: May 2007

The root-knot nematode Meloidogyne incognita (Kofoid & White) Chitwood is one of the most harmful species within the genus Meloidogyne. It has been detected regularly in greenhouses throughout Europe, while in the field it is restricted to the southern parts of Europe (4). M. incognita is able to parasitize more than 700 plant species and varieties, including the majority of our economically important crops (1). It has been recorded in most parts of the world, including former Yugoslavia; however, there is no data about its presence in Slovenia. In late summer of 2002, large galls were observed on roots of pepper, Capsicum annuum L., grown in a greenhouse located in Portorož near the Adriatic Coast of Slovenia. Different root-knot nematode stages, i.e., males, females, and second-stage juveniles, were isolated and morphologically identified as M. incognita (2). Additional isozyme gel electrophoresis confirmed this (3). To our knowledge, this is the first report of M. incognita from Slovenia. In addition, M. hapla Chitwood was found for the first time in a field in Slovenia. Previously, it had been detected on different host plants, all restricted to greenhouses. In October 2002, M. hapla was isolated and identified from relatively small galls of sweet pepper, C. annuum L., grown in a field near Ljubljana, located in central Slovenia. Additional resampling of the soil comfirmed the presence of M. hapla in this field.

References: (1) J. D. Eisenback. Root-Knot Nematode Taxonomic Database. CD-ROM, CABI, Wallingford, UK, 1998. (2) J. D. Eisenback and H. Hirschmann Triantaphyllou. Root-knot nematodes: Meloidogyne species and races. Pages 191–274 in: Manual of Agricultural Nematology. W. R. Nickle, ed. Marcel Dekkers, Inc., New York, 1991. (3) P. R. Esbenshade and A. C. Triantaphyllou. J. Nematol. 17:6, 1985. (4) G. Karssen. Revision of the European root-knot nematodes III on mono- and dicotyledons. Pages 119–121 in: The Plant-Parasitic Nematode Genus Meloidogyne Göldi, 1892 (Tylenchida) in Europe. Koninklijke Brill NV, Leiden, the Netherlands, 2002.
A Survey of Viruses Affecting Faba Bean (Vicia faba) in Tunisia Includes First Record of Soybean dwarf virus
Authors: Najar Asma , Kumari Safaa G. , Makkouk Khaled M. , Daaloul Abderazzek
Published: May 2007

A survey was conducted in April 2003 to identify viruses infecting faba bean (Vicia faba L.) in six regions (Beja, Bizerte, Cap-bon, Le Kef, Siliana, and Zaghouan) in Tunisia. A total of 292 faba bean samples with symptoms of viral infection (leaf rolling, yellowing, and mosaic) were collected. The samples were tested at the virology laboratory of the International Center for Agricultural Research in the Dry Areas (ICARDA), Syria, for 11 viruses using the tissue-blot immunoassay procedure (3). Specific rabbit polyclonal antisera were used to test for Chickpea chlorotic dwarf virus (CpCDV) (provided by H. J. Vetten, BBA, Braunschweig, Germany), Alfalfa mosaic virus (AMV), Bean yellow mosaic virus (BYMV), Broad bean mottle virus (BBMV), Broad bean stain virus (BBSV), Cucumber mosaic virus (CMV), and Pea seedborne mosaic virus (PSbMV) (ICARDA, Aleppo, Syria). In addition, four specific monoclonal antibodies were used to detect Bean leaf roll virus (BLRV) (4B10) (2), Beet western yellows virus (BWYV) (ATCC PVAS-647; American Type Culture Collection, Manassas, VA), Faba bean necrotic yellows virus (FBNYV) (3-2E9) (1), and Soybean dwarf virus (SbDV) (ATCC PVAS-650). Serological tests showed that BBMV, a beetle-transmitted and seedborne virus identified in 23.3% (68 samples) of the samples tested, was the most common. BLRV, FBNYV, BWYV, BYMV, SbDV, and PSbMV were detected in 56, 33, 31, 10, 5, and 1 sample(s) of 292 samples tested, respectively. AMV, BBSV, CMV, and CpCDV were not detected in any samples tested. In Tunisia, BLRV, BWYV, BYMV, FBNYV, and PSbMV have previously been reported in faba bean (4), but to our knowledge, this is the first record of SbDV affecting faba bean in Tunisia, where it was detected in two fields in the Cap-bon Region. In sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by western blots, extracts from SbDV-infected plants were observed to contain 23-kDa structural proteins, which reacted strongly with SbDV monoclonal antibodies. Transmission tests showed that the samples, which reacted with SbDV monoclonal antibodies, were transmitted to faba bean plants by the pea aphid (Acyrthosiphon pisum Harris) in a persistent manner. To our knowledge, this is the first report of SbDV naturally infecting faba bean in Tunisia and it could cause a serious problem to other leguminous crops grown in Tunisia, such as French bean and peas, which are hosts for the virus.

References: (1) A. Franz and K. M. Makkouk Ann. Appl. Biol. 128:255, 1996. (2) L. Katul. Characterization by serology and molecular biology of bean leaf roll virus and faba bean necrotic yellows virus. PhD thesis. University of Gottingen, Gottingen, Germany, 1992. (3) K. M. Makkouk and A. Comeau. Eur. J. Plant Pathol. 100:71, 1994. (4) A. Najar et al. Phytopathol. Mediterr. 39:423, 2000.
Viruses Infecting Cassava in Kenya
Authors: Were H. K. , Winter S. , Maiss E.
Published: May 2007

A survey of cassava viruses was conducted in major cassava-growing regions of Kenya. A total of 185 leaf samples and 62 stem cuttings from plants with viral disease symptoms were collected and analyzed by biological, electron microscopy, enzyme-linked immunosorbent assay, and polymerase chain reaction. All samples from western Kenya had cassava begomoviruses (African cassava mosaic virus [ACMV], East African cassava mosaic virus [EACMV], and Uganda variant [EACMV-UG]) in either single or in mixed infection. However, all samples from the Coast region were infected with only EACMV, a begomovirus. In addition, 15 samples had mixed infections of EACMV and three other hitherto unidentified filamentous viruses. The viruses observed were 200, 500, 650, and 750 nm long, respectively. In addition to rod-shaped and some flexuous viruses, as seen in a crude sap preparation, pinwheels also were observed, indicating a possible association of some of the viruses with the Potyviridae family. The symptoms induced by these viruses in Nicotiana benthamiana were very severe and often caused about 50% death of the test plants. Back inoculation onto cassava resulted in 100% infections. This finding provides evidence that, other than begomoviruses that cause serious diseases of cassava in Africa, filamentous viruses also are present and, despite their limited distribution, they could reach local significance and, most probably, be as serious as begomoviruses. The implications of these findings are discussed and recommendations for future work suggested.
First Report of Peronospora farinosa f. sp. spinaciae Race 5 Causing Downy Mildew on Spinach in Florida
Authors: Irish B. M. , Correll J. C. , Raid R. N. , Morelock T. E.
Published: May 2007

Downy mildew, caused by Peronospora farinosa f. sp. spinaciae, is an economically important disease in most areas where spinach is grown. This disease has become increasingly important in production fields for prepackaged salad mixes where plant densities typically are very high. In Florida, spinach production for these markets has reached approximately 200 ha. Currently, seven physiological races of the downy mildew pathogen have been described (1). Downy mildew was observed in several commercial spinach fields in the Everglades agricultural area of Palm Beach County, Florida in January 2003 on cvs. Unipak 151 and Merlo Nero. Symptoms appeared as chlorotic and necrotic leaf spots. Disease incidence reached approximately 25% in some field locations. Economic losses were significant, since entire plantings in several fields were not harvested as a result of diminished quality. The race of a field isolate recovered from the cv. Unipak 151 was determined following greenhouse inoculation procedures and using differentials outlined by Irish et al (1). Greenhouse inoculation tests were conducted twice. Disease reactions on a U.S. and international set of differentials indicated that the isolate was race 5. To our knowledge, this is the first report of race 5 occurring outside of the California/Arizona spinach production area in the United States. There are commercial spinach lines with resistance to race 5, as well as the other described races (1).

References: (1) B. M. Irish et al. Plant Dis. 87:567, 2003.
First Report of Basal Stem Rot of Golden Barrel Cactus Caused by Fusarium oxysporum f. sp. opuntiarum in Italy
Authors: Polizzi G. , Vitale A.
Published: May 2007

Golden barrel cactus (Echinocactus grusonii Hildm.) is the most common landscape cactus in southern Italy. During 2000, 2001, and 2002, a basal stem rot of golden barrel cactus was observed in several plastichouses located in eastern Sicily with disease levels of nearly 100% on young plants (up to 15 cm in diameter). On the basal crown area, the plants showed pale brown or yellow-orange, sunken lesions bordered by a reddish orange strip up to 1 mm wide. A water-soaked rot or white mycelium at the soil line was also observed. Thirty pieces (0.5 to 1 cm) from the edge of symptomatic tissues were surface disinfected for 2 min in 0.8% (wt/vol) NaOCl, washed with sterile distilled water (SDW), and placed on potato dextrose agar (PDA). In addition, 20 pieces of affected tissue were ground in 400 μl of SDW (1:3, wt/wt), and the resulting suspensions were streaked by loops on PDA supplemented with 1.1 μl/ml of lactic acid (pH 4.4). A Fusarium sp. was consistently isolated from affected tissue pieces and streaks. Koch's postulates were performed at 25°C by inoculating 24 golden barrel cactus plants in 12-cm-diameter pots (12 plants previously sterile needle wounded) with 10 ml per plant of three suspensions (106 CFU/ml) of three isolates sprayed onto the basal stem. One milliliter per ten g of soil of each suspension was also added in the crown portion of golden barrel cacti. Twelve control cacti (six wounded) were sprayed only with SDW. Further pathogenicity tests were carried out on Thanksgiving cactus (Schlumbergera truncata (Haw.) Moran), devil's tongue barrel cactus (Ferocactus latispinus (Haw.) Britton & Rose), peruvian old man cactus (Espostoa lanata (Kunth) Britton & Rose), and Parodia spp. by inoculating eight plants for each host (four wounded) by placing 9-day-old 6-mm mycelial plugs at the base of the healthy cacti. An equal number of plants (four wounded) was inoculated only with a PDA plug. All cacti were maintained in polyethylene bags (90 to 95% for 72 hr) at 25°C. After 12 to 15 days, all wounded inoculated golden barrel, devil's tongue barrel, and peruvian old man cacti exhibited similar symptoms observed in the plastichouses. Typical symptoms were visible also in nonwounded and inoculated cacti 15 days later. Yellow-orange, tan, sunken, and roughly circular lesions were observed on the wounded and inoculated Thanksgiving and Parodia sp. cacti. Control plants were symptomless. The causal fungus was always reisolated from infected cacti. On the basis of 3-septate macroconidia (27 to 35 μm long × 3 to 4 μm wide [average 31.45 × 3.18 μm]), microconidia aseptate, single or double chlamydospores, and monophialide conidiophores observed on carnation leaf agar, and considering the susceptibility of all other inoculated hosts, the fungus was identified as F. oxysporum Schlechtend. f. sp. opuntiarum (Speg.) (1). To our knowledge, this is the first report of basal stem rot of golden barrel cactus in Italy.

Reference: (1) W. Gerlach. Phytopathol. Z. 74, 197, 1972.
First Report of Petunia Root Rot Caused by Rhizoctonia solani in Argentina
Authors: Wright E. R. , Rivera M. C. , Asciutto K. , Gasoni L. , Barrera V. , Kobayashi K.
Published: May 2007

Common garden petunias (Petunia × hybrida Hort. Vilm.-Andr.) are herbaceous annual plants with brightly colored flowers up to 10 cm in diameter. During the winter of 2002, crown and root rot were observed on plants (cv. Ultra) growing in five greenhouses in Buenos Aires. Affected plants were randomly distributed in the greenhouses, and mean disease incidence in all the greenhouses was 26%. Basal leaves turned yellow and gradually became necrotic, and infected plants were often killed. Small pieces of affected tissues were disinfested in 2% sodium hypochlorite for 1 min and plated on 2% potato dextrose agar (PDA). Fifteen isolates identified to the genus Rhizoctonia were obtained. Fungal colonies were initially white, turned brown with age, and produced irregularly shaped, brown sclerotia. Hyphal branched at right angles, were constricted at the base of the branch near the union with main hyphae, and septate near the constriction. Basidia were not observed in the greenhouses or on the plates. Isolates were cultivated on water agar and incubated at 25°C for 3 days. Hyphal cells were determined to be multinucleate when stained with 1% aniline blue solution (2) and examined at ×400. Anastomosis group of one isolate was determined by using AG-4 HG II, AG-1 IA, AG-1 IB, AG-1 IC, AG-2 2-1, and AG-2 2IIIB tester strains of Rhizoctonia solani that includes isolates reported to be pathogenic on ornamentals (1). Anastomosis was observed only with strains of AG-4 HG II. Pathogenicity on this isolate was conducted on potted, healthy, adult plants that were 10 to 22 cm high and flowering. Thirty-five plants were inoculated by placing 1 cm2 pieces of PDA from 7-day-old mycelial cultures near the base of the stem. Twelve control plants were treated with 1 cm2 PDA plugs. Plants were kept at 22 to 24°C, >95% relative humidity, and 12 h of fluorescent light. Wilt symptoms due to basal stem rot appeared 7 days after inoculation, and all the inoculated plants died within 27 days. Control plants remained disease free. The pathogen was reisolated from symptomatic tissues, completing Koch's postulates. To our knowledge, this is the first report of R. solani causing disease on petunia in Argentina.

References: (1) D. M. Benson and D. K. Cartwright. Ornamental diseases incited by Rhizoctonia spp. Pages 303–314 in: Rhizoctonia species: Taxonomy, Molecular Biology, Ecology, Pathology and Disease Control. B. Sneh et al., eds. Kluwer Academic Publishers, London, England, 1996. (2) C. C. Tu and J. W. Kimbrough. Mycologia 65:941, 1973.