bluuebunny/crossref_metadata_2025 huggingface dataset:
First Report of Armillaria mellea s. str. in Hardwood Forests of Southern Ontario
Authors: McLaughlin J. A.
Published: May 2007

Armillaria mellea sensu stricto (Vahl:Fr.) Kummer has been found infrequently in studies conducted in northeastern North America (2) and it was not found in an earlier survey of northern Ontario (3). In a 1999 survey of Armillaria spp. conducted in central and southern Ontario, A. mellea s. str. was found at four of 110 locations surveyed, two approximately 100 km west and southwest of Ottawa, one 15 km north of Belleville, and one on the Niagara Peninsula in the Balls Falls Conservation Area. At the Ottawa area sites, A. mellea s. str. was found on red oak (Quercus rubra L.) and beech (Fagus grandifolia Ehrh.) stumps. A. ostoyae (Romagn.) Herink and A. gallica Marxmuller & Romagn. were also found on these sites. At the Belleville site, it was found on a dead co-dominant white birch (Betula papyrifera Marsh.), while at the Niagara Peninsula site it was found on a dead, suppressed beech. A. gallica was also found at these latter sites. Sites ranged from moisture regimes fresh to moist, and from sandy to silty soil from both calcareous and non-calcareous parent material. Four isolates were obtained from infected wood and rhizomorphs and identified by the polymerase chain reaction, yielding restriction fragment length polymorphism (RFLP) products of 500 and 183 base pairs. These fragment sizes are similar to findings reported in an earlier study (4). The identification was confirmed by haploid/diploid pairing. The Balls Falls Conservation Area is in close proximity to extensive fruit orchards and the presence of A. mellea is cause for concern, especially in light of its proven pathogenicity to fruit trees (1). This is the first confirmation of A. mellea s. str. in Ontario.

References: (1) J. E. Adaskaveg and J. M. Ogawa. Plant Dis. 74:341–352, 1990. (2) J. T. Blodgett and J. J. Worrall. Plant Dis. 76:166–170, 1992. (3) M. T. Dumas. Can. J. For. Res. 18:872–874, 1988. (4) T. C. Harrington and B. D. Wingfield. Mycologia 87:280–288, 1995.
Latent Infection of Austrian and Scots Pine Tissues by Sphaeropsis sapinea
Authors: Flowers J. , Nuckles E. , Hartman J. , Vaillancourt L.
Published: May 2007

This study documents latent infection of Austrian and Scots pine tissues by Sphaeropsis sapinea, the causal agent of Sphaeropsis tip blight disease. Symptomless shoots from diseased or apparently healthy Austrian and Scots pine trees were cultured and analyzed for the presence of S. sapinea. Nearly half of the sampled Austrian and Scots pine trees that appeared to be completely healthy had detectable latent S. sapinea infections. More than half of the symptomless shoots on visibly diseased Austrian and Scots pine trees were also latently infected with S. sapinea. S. sapinea was isolated from symptomless shoot stems, needles, buds, immature cones, and male flowers. In symptomless infected shoots, the fungus was primarily associated with the bark and phloem tissues. Six isolates of S. sapinea from symptomless Austrian and Scots pine shoot tissues were pathogenic on Austrian pine seedlings in the greenhouse. The presence of S. sapinea in symptomless tissues of tip blight-diseased trees has important implications for disease management.
Effect of Host Plant Resistance and Reduced Rates and Frequencies of Fungicide Application to Control Potato Late Blight
Authors: Kirk W. W. , Felcher K. J. , Douches D. S. , Coombs J. , Stein J. M. , Baker K. M. , Hammerschmidt R.
Published: May 2007

Field experiments were conducted during 1998 to 2000 to determine the response of commercial potato cultivars and advanced breeding lines (ABL) differing in susceptibility to foliar late blight (caused by Phytophthora infestans) to reduced rates and frequencies of residual, contact fungicide applications. When environmental conditions were most favorable for the development of late blight, the lowest application rate of the fungicides chlorothalonil or fluazinam (33% of the manufacturers' recommended application rate [MRAR]) gave unsatisfactory control of potato late blight. Under conditions moderately conducive for late blight development, effective control was achieved with 33 to 66% MRAR with either fungicide. The Michigan State University advanced selection, MSG274-3, was the least susceptible ABL tested and, during 1998 to 2000, late blight was effectively managed using reduced rates of fungicides. Application rates of chlorothalonil (33 to 100% MRAR) significantly reduced late blight in the cultivar Snowden (5-day application interval) compared with the nontreated control; whereas, late blight was not effectively controlled in Snowden even at 100% MRAR of chlorothalonil at either 10- or 15-day application intervals in 1999 or 2000. The ABL MSG274-3 was the least susceptible of all cultivars and ABL used in this study, and required minimal chemical protection against late blight. The study demonstrates that ABL with reduced susceptibility to late blight can be managed with reduced fungicide rates and longer application intervals, thus offering more economical control of this disease.
Molecular Identification of a Phytoplasma Associated with Witches'-Broom Disease of Black Raspberry in Oregon and Its Classification in Group 16SrIII, New Subgroup Q
Authors: Davis R. E. , Dally E. L. , Converse R. H.
Published: May 2007

Plants of Rubus occidentalis (black raspberry) ‘Munger’ exhibiting symptoms of black raspberry witches'-broom (BRWB) disease were observed in commercial fields in Oregon (1). Symptoms were often severe, leading to death of infected plants, and a phytoplasma (mycoplasmalike bodies) was observed in ultrathin sections of diseased plants (1). In the current work, the association of phytoplasma with BRWB was assessed using the polymerase chain reaction (PCR) for specific amplification of phytoplasmal rDNA. DNA template for use in the PCR was extracted from plants as described elsewhere (2). Phytoplasmal 16S rDNA was amplified from diseased black raspberry plants in PCR primed by primer pair P1/P7 and reamplified in nested PCR primed by primer pair R16F2n/R2 (F2n/R2) by a method described previously (2). These results indicated the presence of a phytoplasma, designated BRWB phytoplasma, in the diseased plants. Identification of BRWB phytoplasma was accomplished by restriction fragment length polymorphism (RFLP) analysis of DNA amplified in PCR primed by F2n/R2. Phytoplasma classification was done according to the system of Lee et al. (3). On the basis of collective RFLP patterns of the amplified 16S rDNA, the BRWB phytoplasma was classified as a member of group 16SrIII (group III, X-disease phytoplasma group). The HhaI RFLP pattern of BRWB 16S rDNA differed from that of its close relative, clover yellow edge (CYE) phytoplasma. The RsaI RFLP pattern of BRWB rDNA differed from that of rDNA from all phytoplasmas previously described in group III. Based on these results, BRWB phytoplasma was classified in a new subgroup, designated subgroup Q (III-Q) within group III. The 1.8 kbp DNA product of PCR primed by primer pair P1/P7 was cloned and its nucleotide sequence determined. The sequence was deposited in GenBank under Accession no. AF302841. Results from putative restriction site analysis of the cloned and sequenced rDNA were in excellent agreement with the results from enzymatic RFLP analysis of uncloned rDNA amplified from BRWB diseased black raspberry. Sequence similarity between the 1.8 kbp rDNA of BRWB phytoplasma and that of CYE phytoplasma was 99.4%. The nucleotide sequence data support the conclusion that the BRWB phytoplasma is related to, but is distinct from, other strains that are classified in group III. These findings contribute knowledge about the diversity of phytoplasmas affiliated with group III and provide information to aid the diagnosis of BRWB disease.

References: (1) R. H. Converse et al. Plant Dis. 66:949, 1982. (2) R. Jomantiene et al. Int. J. Syst. Bacteriol. 48:269, 1998. (3) I.-M. Lee et al. Int. J. Syst. Bacteriol. 48:1153, 1998.
First Occurrence of Powdery Mildew Caused by Leveillula taurica on Pepper in New York
Authors: McGrath M. T. , Shishkoff N. , Bornt C. , Moyer D. D.
Published: May 2007

Powdery mildew was observed for the first time on pepper (Capsicum annuum L.) in western New York in August 1999 and on Long Island, NY, in August 2000. Infected plants were found in commercial fields planted with transplants from Georgia and Florida. Powdery mildew was not found in nearby commercial fields in either year, and it was not found in 2000 in western New York. Symptoms included white sporulation on the undersurfaces of leaves, causing yellow lesions on upper surfaces that turned necrotic and led to premature defoliation. The pathogen was confirmed to be Leveillula taurica (Lév.) G. Arnaud, a species complex that infects more than 1,000 plant species in 74 families, including pepper, tomato and eggplant. Only the Oidiopsis stage was found. Conidia were 47.3 to 74.3 μm × 10.5 to 20.3 μm (average 64.0 × 16.8 μm (N = 71). Symptoms were observed on all cultivars of bell and chili pepper in the Long Island field but not on tomato (Lycopersicon esculentum) and eggplant (Solanum melongena var. esculentum) in adjacent rows. Powdery mildew of pepper was first observed in North America in 1971 in southwest Florida (1). Symptoms were found on field-grown peppers in Florida in April 2001 at the time that transplants were being produced for New York. Considering the latent period is 18 to 21 days and symptoms tend to be initially subtle, diseased seedlings could easily go undetected. This disease is a problem on tomatoes and peppers in California (2), Arizona, Utah, and Nevada. Powdery mildew of pepper was reported in Puerto Rico in 1992, in Idaho on greenhouse-grown pepper in 1998, in north-central Mexico in 1998, and in both Canada and Oklahoma on greenhouse-grown pepper in 1999. Powdery mildew of peppers has not been seen in Connecticut, Massachusetts, New Jersey, North Carolina, or Ohio.

References: (1) C. H. Blazquez. Phytopathology 66:1155, 1976. (2) R. F. Smith et al. Calif. Agric. 53:40, 1999.
Outbreak of Tomato spotted wilt virus in Tomato in Kenya
Authors: Wangai A. W. , Mandal B. , Pappu H. R. , Kilonzo S.
Published: May 2007

Tomato spotted wilt virus (TSWV) of the genus Tospovirus, family Bunyaviridae (1), causes an economically important virus disease in tomato in several parts of the world. The virus has a wide host range that includes numerous crops and weeds and is transmitted by at least seven species of thrips. Tomato crops in the Subukia, Bahati, and Kabazi areas of the Nakuru District in Kenya were affected by a disease suggestive of TSWV infection during the November 1999 to March 2000 tomato-growing season. Farmers reported up to 80% losses of their potential yields. Characteristic symptoms were noticed on fruits, especially when they were green. Distinct concentric rings on fruits, which later turned into brown, uneven ripening, were the most visible symptoms. Foliage did not develop pronounced symptoms, but mild bronzing was observed in a few cultivars. However, foliage senesced prematurely, starting with older leaves. Foliar symptoms were mistaken for blight infection, and as a result, excessive fungicides were applied that failed to manage the disease. To test for TSWV infection, tomato leaf samples collected from the fields were tested initially with a TSWV test kit (HortiTech, Horticulture Research International, Wellesbourne, UK), and the results were confirmed by double-antibody sandwich-enzyme-linked immunosorbent assay with antibodies from Agdia Inc. (Elkhart, IN). Further molecular characterization was done using reverse transcription-polymerase chain reaction (RT-PCR). Total RNA was extracted from symptomatic leaves of tomato cv. Money Maker using the RNeasy mini kit (Qiagen Inc., Valencia, CA). Using primers 5′ TTAAGC AAGTTCTGTGAG 3′ and 5′ ATGTCTAAGGTTAAGCTC 3′ specific to the nucleoprotein (N) gene of TSWV, the N gene was amplified by RT-PCR (2). A 777-bp product of the expected size was obtained from symptomatic plants, whereas no amplification was obtained from noninfected tomato. The PCR product was cloned into pGEM-T Easy (Promega, Madison, WI) and sequenced. A search of GenBank revealed a sequence identity of 95 to 99% with the N genes of known TSWV isolates. To our knowledge, this is the first report TSWV infection of tomato in Kenya. Considering its wide host range, future surveys should be directed toward estimating its incidence in tomato and other TSWV-susceptible crops, such as Irish potatoes, pepper, peanut (groundnut), beans, and a wide variety of ornamental cut flowers in Kenya.

References: (1) J. W. Moyer. Tospoviruses (Bunyaviridae). Pages 1803–1807 in: Encyclopedia of Virology. A. Granoff and R. G. Webster, eds. Academic Press, San Diego, CA, 1999. (2) Jain et al. Plant Dis. 82:900, 1998.
Optimization of Chemical Suppression of Alternaria dauci, the Causal Agent of Alternaria Leaf Blight in Carrots
Authors: Ben-Noon E. , Shtienberg D. , Shlevin E. , Vintal H. , Dinoor A.
Published: May 2007

Alternaria leaf blight, caused by Alternaria dauci, is a major constraint to carrot production in Israel. Israeli carrot growers apply prophylactic sprays at 3- to 10-day intervals throughout the season until harvest, up to 30 sprays in a growing season. In this study, we attempted to optimize the chemical suppression of the disease, in order to reduce fungicide use. The efficacy of nine fungicides was determined in two field experiments. All fungicides reduced disease severity, but there were significant differences in efficacy among them. The most effective were difenoconazole and chlorothalonil; less effective were copper hydroxide, tebuconazole, trifloxystrobin, and mancozeb; the least effective in our experiments were flutrifol, propineb, and iprodione. The effect of the time of spray initiation on fungicide efficacy was determined in three field experiments. Qualitative (analysis of variance) and quantitative (regression) analyses of the data revealed that initiating sprays after disease onset reduced control efficacy. Thus, an action threshold model could not be developed for A. dauci in carrots. The time before harvest at which sprays could be terminated was tested in two field experiments and it was found that terminating sprays 14 days before harvest did not significantly affect the overall control efficacy. The main conclusions derived from these experiments were tested and corroborated in two additional field experiments.
Detection of Sugarcane yellow leaf virus in Quarantine and Production of Virus-free Sugarcane by Apical Meristem Culture
Authors: Chatenet M. , Delage C. , Ripolles M. , Irey M. , Lockhart B. E. L. , Rott P.
Published: May 2007

Sugarcane yellow leaf virus (SCYLV) was detected for the first time in 1996 in the Centre de Coopération Internationale en Recherche Agronomique pour le Développement (CIRAD) sugarcane quarantine at Montpellier by reverse transcription-polymerase chain reaction (RT-PCR) in varieties from Brazil, Florida, Mauritius, and Réunion. Between 1997 and 2000, the virus was found by RT-PCR and/or tissue-blot immunoassay (TBIA) in additional varieties from Barbados, Cuba, Guadeloupe, Indonesia, Malaysia, Philippines, Puerto Rico, and Taiwan, suggesting a worldwide distribution of the pathogen. An excellent correlation was observed between results obtained for the two diagnostic techniques. However, even though only a few false negative results were obtained by either technique, both are now used to detect SCYLV in CIRAD's sugarcane quarantine in Montpellier. The pathogen was detected by TBIA or RT-PCR in all leaves of sugarcane foliage, but the highest percentage of infected vascular bundles was found in the top leaves. The long hot water treatment (soaking of cuttings in water at 25°C for 2 days and then at 50°C for 3 h) was ineffective in eliminating SCYLV from infected plants. Sugarcane varieties from various origins were grown in vitro by apical bud culture and apical meristem culture, and the latter proved to be the most effective method for producing SCYLV-free plants.
Development of Wilt in Mint in Response to Infection by Two Pathotypes of Verticillium dahliae and Co-infection by Pratylenchus penetrans
Authors: Johnson Dennis A. , Santo Gerald S.
Published: May 2007

Two isolates of Verticillium dahliae in vegetative compatibility group (VCG) 2B and one isolate in VCG 4A were tested for aggressiveness on peppermint, Scotch spearmint, and native spearmint alone and in combination with the lesion nematode Pratylenchus penetrans. The VCG 2B isolates were more aggressive than the VCG 4A isolate on all three mint species. Severity of wilt was greatest on peppermint and scotch spearmint with the VCG 2B isolates, and CFU of V. dahliae recovered from infected stems were greater in Scotch spearmint when inoculated with V. dahliae and P. penetrans than when inoculated with VCG 2B alone. Wilt severities and CFU in peppermint and Scotch spearmint were not increased when inoculated with VCG 4A and P. penetrans compared with VCG 4A alone. These data indicate that V. dahliae isolates from VCG 2B but not VCG 4A interact synergistically with P. penetrans on Verticillium isolate-susceptible mints. The resistance to Verticillium isolates in native spearmint was not affected by the presence of lesion nematodes.
Detection of Poinsettia mosaic virus Infecting Poinsettias (Euphorbia pulcherrima) in Venezuela
Authors: Carballo O. , Izaguirre M. L. , Marys E.
Published: May 2007

Poinsettia mosaic virus (PnMV), a putative member of the tymoviruses, was detected in several cultivars of vegetatively propagated poinsettias grown in commercial nurseries in Estado Miranda, Venezuela. Symptoms associated with the affected plants consisted of severe mottling and distortion of leaves and bracteoles. The suspect virus was mechanically transmitted to Nicotiana benthamiana. Leaf extracts and thin sections of affected leaf tissue were analyzed by transmission electron microscopy. Spherical virus particles (30 nm diameter) were observed in samples from symptomatic poinsettia plants. Ultrastructural analyses of virus-infected cells revealed aggregates of virus particles in the cytoplasm and central vacuole. The virus was purified twice from infected N. benthamiana, resulting in yields as high as 12 mg/100 g. Dissociated coat protein contained a single 24-kDa protein species. The virus was not serologically related to Carnation mottle, Bean rugose mosaic, Cowpea mosaic, Cucumber mosaic, Pea enation mosaic, Prunus necrotic ringspot, Apple mosaic, Tobacco streak, Maize rayado fino, Tomato ringspot, Bean southern mosaic, Sowbane mosaic, Andean potato latent, Belladona mottle, Scrophularia or Turnip yellow mosaic viruses, but did react positively in enzyme-linked immunosorbent assay and western blot analysis with antiserum (ATCC PVAS-476) to PnMV. Based on these results, the virus is considered to be PnMV. To our knowledge, this is the first report of PnMV infecting poinsettias in Venezuela.
Report of Leaf Spot of Spinach Caused by Stemphylium botryosum in Maryland and Delaware
Authors: Everts K. L. , Armentrout D. K.
Published: May 2007

In October 2000, leaf spot symptoms were observed on spinach (Spinacia oleracea L. ‘Seven R’) at the University of Maryland Lower Eastern Shore Research and Education Center in Salisbury. In April 2001, a similar leaf spot disease was observed in two commercial spinach fields (cv. Vancouver) in Dorchester County, MD, and Sussex County, DE. Symptomatic plants occurred in foci, and overall disease incidence in the research and commercial fields was <10% of plants with lesions. However, low disease incidence may reduce the value of a spinach crop by requiring additional hand-sorting (fresh market) or lowering the grade (processing). Leaf spot lesions were small (0.2 to 0.7 cm), circular, tan, and papery and lacked visual signs of fungal infestation. Lesions resembled a new leaf spot of spinach reported in California (1) caused by Stemphylium botryosum Wallr. Plating surface-disinfested lesion margins on 0.25-strength potato dextrose agar consistently yielded S. botryosum. Single conidial cultures of three isolates were grown on V8 agar in a growth chamber with a 12 h light/dark regime at 21°C and were used for the pathogenicity test. Conidia were collected from 7-day-old colonies to test pathogenicity. Conidia were suspended in distilled water (1.1 × 105 conidia per milliliter), and sprayed on 4-week-old spinach plants (with four to six true leaves) of cvs. Seven R, Vancouver, and Melody. Noninoculated control plants were sprayed with deionized water. Plants were incubated for 72 h in a dew chamber (18°C, 9 to 15 h light/dark regime where dew formed during the dark periods) and then placed on a greenhouse bench (23°C) for 2 weeks. Plants that had been inoculated with any of the three isolates developed the aforementioned leaf spot lesions after 4 days in the greenhouse. Plants sprayed with deionized water were symptomless. One week after inoculation, more lesions were observed on ‘Seven R’ and ‘Vancouver’ than on ‘Melody’ (41, 39, and 1 lesion per plant, respectively; P< 0.0030), and the lesions were 1.5, 1.2, and 0.5 mm in diameter, respectively (P< 0.0001). S. botryosum was consistently reisolated from leaf spot lesions. The pathogenicity test was repeated with similar results. Isolates grown on V8 agar and incubated for ≈10 days produced conidia with mean dimensions of 31 × 19 μm. To our knowledge, this is the first report of leaf spot of spinach caused by S. botryosum in Maryland and Delaware.

Reference: (1) S. T. Koike et al. Plant Dis. 85:126, 2001.
Sensitivity of Mycosphaerella fijiensis from Banana to Trifloxystrobin
Authors: Chin K. M. , Wirz M. , Laird D.
Published: May 2007

An ascospore germination method was developed and validated to assess the sensitivity of bulk samples of Mycosphaerella fijiensis to trifloxystrobin. Using this method, the sensitivity of 142 ascospore samples from banana plantations not treated with strobilurins was analyzed to establish a baseline of pathogen sensitivity. A bulk method was utilized for monitoring purposes because it avoids potential complications due to the isolation and propagation of single-spore isolates and enables the testing of larger samples. Following intensive use of strobilurins (6 to 11 applications per year) over 4 years, under conditions of high disease pressure and the absence of sanitary measures at a development site in Costa Rica, bulk samples with 50% effective concentration (EC50) resistance factors (RFs) in excess of 500 compared with the mean baseline sensitivity were detected. Single-ascospore isolates derived from spores germinating at the discriminatory dose of 3 μg/ml were also resistant, suggesting that the frequency of resistant individuals in bulk samples could be estimated from the relative numbers of ascospores growing at this dose. The resistance of selected isolates was confirmed in planta. In vitro tests with four resistant and two sensitive single-ascospore isolates collected from different locations and times indicated possible cross-resistance of trifloxystrobin to azoxystrobin, famoxadone, and fenamidone, but not to propiconazole.
Evidence of a Naturally Occurring Recombinant Between Tomato yellow leaf curl virus and Tomato yellow leaf curl Sardinia virus in Spain
Authors: Monci F. , Navas-Castillo J. , Moriones E.
Published: May 2007

Tomato yellow leaf curl virus (TYLCV, formerly TYLCV-Is) and Tomato yellow leaf curl Sardinia virus (TYLCSV, formerly TYLCV-Sar) are geminivirus species of the genus Begomovirus that cause the disease known as tomato yellow leaf curl. In Spain, TYLCV and TYLCSV have coexisted in field and greenhouse tomato (Lycopersicon esculentum) crops since 1996 (2). TYLCV is also the causal agent of the leaf crumple disease of common bean (Phaseolus vulgaris) (1), a species that TYLCSV is unable to infect (2). Analysis of field samples from common bean plants affected by leaf crumple disease collected in Almería (southeastern Spain) during 1999 showed that, unexpectedly, several samples hybridized with TYLCV- and TYLCSV-specific probes prepared to the intergenic region (IR) as previously described (1). Polymerase chain reactions (PCR) performed with total nucleic acids extracted from one of these samples (ES421/99) using primer pairs specific to the IR of TYLCV (MA-30/MA-31) or TYLCSV (MA-14/MA-15) (1) gave no amplification product. However, the combination of MA-30 (5′ end of TYLCV IR) and MA-15 (3′ end of TYLCSV IR) produced a PCR DNA product of the expected size (351 bp). Direct DNA sequencing of this product (GenBank Accession No. AF401478) indicated the presence of a chimeric IR in ES421/99. Comparison of the obtained sequence with those available for isolates reported from Spain showed that the 5′ side (149 nt) from the stem-loop structure conserved in the IR of all geminiviruses was 99% identical to the corresponding region of TYLCV (GenBank Accession No. AF071228) and only 62% identical to TYLCSV (GenBank Accession No. Z25751). In contrast, the 3′ side (124 nt) from the stem-loop was 98% identical to the corresponding region of TYLCSV and only 57% identical to TYLCV. The 33-nt region involved in the stem-loop was 100% identical to TYLCV and showed one nucleotide change in the loop with respect to TYLCSV. Therefore, this DNA sequence data showed evidence of the occurrence in ES421/99 of a natural recombination between TYLCV and TYLCSV. The biological and epidemiological consequences of the presence of this new interspecific recombinant have yet to be determined.

References: (1) J. Navas-Castillo et al. Plant Dis. 83:29, 1999. (2) S. Sánchez-Campos et al. Phytopathology 89:1038, 1999.
Mosaic Disease of Calla Lily Caused by a New Potyvirus in Taiwan
Authors: Chang Y.-C. , Chen Y.-L. , Chung F.-C.
Published: May 2007

In 1998, a new mosaic disease of calla lily (Zantedeschia spp.) was found in Taichung County, Taiwan. Primary symptoms were mosaic and green islands on leaves and discolored spots on flowers. Symptomatic plants were negative in double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) for Dasheen mosaic virus (DsMV) polyclonal antibody (Agdia Inc., Elkhart, IN), but were positive in indirect ELISA using an anti-potyvirus group monoclonal antibody. Extracts from these plants were infective by mechanical inoculation to seedlings of calla lily and Philodendron selloum, which expressed veinal chlorosis, mosaic, and green island symptoms. Transmission electron microscopic analysis indicated that the virus particles purified from inoculated P. selloum were 695 to 845 nm long. In addition, potyvirus-specific cytoplasmic inclusions were observed in epidermal cells of infected calla lily. The 3′-terminal region of the virus was amplified by reverse-transcription polymerase chain reaction from total RNA or viral RNA using a potyvirus-specific degenerate primer and an oligo(dT) primer. A 1.6-kb amplified fragment was cloned, and three independent clones were sequenced. The sequences included a portion of NIb gene, the coat protein (CP) gene, the 3′ untranslated region (3′UTR) and the poly(A) tail. This nucleotide sequence (GenBank Accession No. AF332872) was checked against the international sequence databases using the BLAST program (provided by National Center for Biotechnology Information online at www.ncbi.nlm.nih.gov/blast/ ). The highest identity of the CP amino acid sequences between this unknown virus and other potyviruses is 68%. Amino acid sequence homologies for the CPs between individual potyviruses are 38 to 71%, while those between strains of a potyvirus are more than 90% (1). Therefore, this Zantedeschia-infecting virus is a previously undescribed potyvirus and is herein designated as Zantedeschia mosaic virus (ZaMV). In further analyses, the amino acid sequence identities of the CP gene between ZaMV and 13 other aphid-transmitted potyviruses were 46 to 61% and 9 to 23% for the nucleotide sequence of the 3′UTR. ZaMV and DsMV showed 46% identity in the CP amino acid sequence and 12% identity in the 3′UTR nucleotide sequence, indicating that they are two distinct members of the genus Potyvirus. To our knowledge, this is the first report of natural infection of Zantedeschia spp. by ZaMV, a new potyvirus identified in Taiwan.

Reference: (1) D. D. Shukla and C. W. Ward. Arch. Virol. 106:171, 1989.
Virulence of Puccinia triticina on Wheat in Nebraska during 1997 and 1998
Authors: Watkins J. E. , Schimelfenig J. , Baenziger P. S. , Eskridge K. M.
Published: May 2007

Urediniospore isolates of Puccinia triticina were obtained from wheat leaf collections made in three wheat-growing regions in Nebraska in 1997 and in four regions in 1998. Using 16 Thatcher lines that are near-isogenic for leaf rust resistance, 17 virulence phenotypes were found among 121 single uredinial isolates in 1997, and 42 virulence phenotypes were found among 178 isolates in 1998. The most prevalent phenotype in 1997 was MDRR (virulent on Lr1, 3, 3ka, 10, 11, 18, 23, 24, and 30). In 1998, virulence phenotypes MDRR and MDRM (virulent on Lr1, 3, 3ka, 10, 11, 23, 24, and 30) were the most prevalent. In both years, virulence frequency was above 80% to genes Lr1, 3, 3ka, 10, 11, 23, 24, and 30 and below 21% to Lr2a, 17, and 26. Virulence frequency to Lr2c was 37% in 1997 and 22% in 1998. No virulence was found to Lr9, 16, or 21 in either year. New virulence phenotypes were detected in 1998 that were not found in 1997. In 1998, virulence was less frequent on Lr2a, 2c, 3ka, 18, 24, and 26 and more frequent on Lr17 than in 1997.
Role of Crop Debris and Weeds in the Epidemiology of Bacterial Leaf Spot of Lettuce in California
Authors: Barak Jeri D. , Koike Steven T. , Gilbertson Robert L.
Published: May 2007

Bacterial leaf spot of lettuce (BLS), caused by Xanthomonas campestris pv. vitians, has increased in importance in California over the past 5 years. The pathogen can be seedborne, but it was not recovered from selected commercial lettuce seed lots planted during this time. Survival of X. campestris pv. vitians in association with plant debris was investigated in a 3-year field experiment in Salinas, CA. The initial lettuce spring crop was spray inoculated with X. campestris pv. vitians, which resulted in 100% disease incidence. Spring crops were followed by a 1-month summer fallow period, whereas fall crops were followed by a 5-month winter fallow period. High populations of X. campestris pv. vitians (up to 106CFU/g) were recovered from lettuce plant debris after the 1-month summer fallow and BLS developed on all subsequent fall lettuce crops. During the winter fallow period, X. campestris pv. vitians populations associated with plant debris declined and, by 2 months after harvest, only small populations were detected. Spring crops also developed BLS, but at reduced levels. X. campestris pv. vitians was recovered from leaves of several symptomless weed species collected around commercial infested fields, but not from weeds collected around previously infested fields during fallow periods. During the course of this study, an X. campestris pv. vitians-specific polymerase chain reaction primer pair was developed.
A PCR-Based Assay to Detect Rhynchosporium secalis in Barley Seed
Authors: Lee H. K. , Tewari J. P. , Turkington T. K.
Published: May 2007

A polymerase chain reaction (PCR)-based diagnostic assay was developed to detect Rhynchosporium secalis, the barley scald fungus, in barley seed. Species-specific primers were designed based on sequence data of a region consisting of the 5.8S RNA gene and internal transcribed spacers 1 and 2 of R. secalis. The sequenced regions showed 100% homology between the two R. secalis isolates and 93% homology between R. secalis and R. orthosporum. Five sets of synthesized oligonucleotide primers were tested for their specificity using 29 isolates of R. secalis of diverse geographic origins and from different barley cultivars. In addition, DNA extracts from 22 species of microbes either taxonomically related to or from the same niche as R. secalis were tested as negative controls. Among five sets of primers, a primer set, RS8 and RS9, was selected for use in detecting R. secalis because it amplified a 264-bp fragment from the DNA of all R. secalis isolates but not the DNA from other species used for validation of the specificity of this primer set. This primer set was also used to detect R. secalis in barley seed and successfully amplified the predicted size of the DNA fragment in the infected material. PCR detection of as little as 1 to 10 pg of R. secalis DNA was possible. The method described here requires 1 day for completion, compared to 10 days required for the cultural method.
First Report of Broad Bean Canker Caused by Pestalotiopsis disseminata in India
Authors: Singh N. Iboton , Devi R. K. Tombisana
Published: May 2007

A canker disease of broad bean (Vicia faba L.) pods was observed annually from February to April every year since 1995. Disease incidence ranged from 45 to 100% in commercial fields and experimental plots at the Central Agricultural University, Imphal, Manipur. Initial symptoms on young pods appeared as bright yellow, scattered spots 1 to 2 mm in diameter that later became raised, black, and corky within 12 days. As the disease progressed, the lesions coalesced and formed large cankers, which resulted in unmarketable pods. Surface-sterilized symptomatic tissues were plated on potato-dextrose agar (PDA) and the fungus that grew out was identified as Pestalotiopsis disseminata. One culture was deposited at the Indian Type Culture Collection, Division of Plant Pathology, Indian Agricultural Research Institute, New Delhi. Pathogenicity of the fungus was determined by pipetting two drops of a 3 × 103 conidia/ml spore suspension on each of five healthy young pods and repeating on each of 10 plants. A similar five pods inoculated with sterile water served as controls. Inoculated broad bean plants were covered with plastic bags for 48 h and placed into the open under shade having a temperature range of 25 to 28°C. Corky lesions similar to those originally observed developed within 16 days on inoculated pods. Symptoms did not appear on control pods. Necrotic tissues from artificially induced broad bean cankers were plated on PDA and consistently yielded P. disseminata. This is the first report of P. disseminata on broad bean in India.
A Population of Meloidogyne javanica in Spain Virulent to the Mi Resistance Gene in Tomato
Authors: Ornat C. , Verdejo-Lucas S. , Sorribas F. J.
Published: May 2007

A population of Meloidogyne javanica virulent to Mi-gene in tomato was identified in Spain. It reproduced similarly on resistant and susceptible tomato cultivars in the greenhouse, microplots, and in the field. In monoxenic cultures, reproduction of the virulent M. javanica was higher than that of an avirulent population on resistant but not on susceptible tomatoes. The virulent population suppressed tomato yield of both resistant and susceptible tomatoes by 29% in microplots. Initial population density (Pi) was inversely correlated with Pf (final population density)/Pi on both resistant and susceptible tomatoes in the field. A negative correlation was found between Pi and tomato yield for the susceptible but not for the resistant cultivar.
Management of Tomato spotted wilt virus in Flue-Cured Tobacco with Acibenzolar-S-Methyl and Imidacloprid
Authors: Csinos A. S. , Pappu H. R. , McPherson R. M. , Stephenson M. G.
Published: May 2007

Tomato spotted wilt virus (TSWV) continues to be a major production constraint in flue-cured tobacco in Georgia. Pretransplant applications of acibenzolar-S-methyl (Actigard) and imidacloprid (Admire and Provado) were evaluated in field trials, singly and in combination, in four locations in 1999. Acibenzolar-S-methyl was also evaluated for its effect on growth and yield, potential phytotoxicity, and activity against tobacco blackshank incited by Phytophthora parasitica var. nicotianae. Acibenzolar-S-methyl alone and with imidacloprid significantly reduced TSWV incidence in all four locations, but the disease incidence in the imidacloprid-treated plots was lower in only one of the four sites. Applications of acibenzolar-S-methyl starting at 4 weeks posttransplant had no effect on TSWV incidence, size, or yield of tobacco compared with nontreated plots. Acibenzolar-S-methyl did not reduce blackshank in a field trial. In the greenhouse, rates of acibenzolar-S-methyl ranging from 0.25 to 8 g a.i. per 7,000 plants showed reductions in growth that did not seem to be related to rate. Pretransplant applications of acibenzolar-S-methyl were critical to the suppression of TSWV, while initial applications made posttransplant had no effect, suggesting that plants must be protected prior to introduction into the field.
Vegetative Compatibility and Pathogenicity of Verticillium dahliae from Spearmint and Peppermint
Authors: Douhan L. I. , Johnson D. A.
Published: May 2007

The vegetative compatibility of 128 isolates of Verticillium dahliae from spearmint and peppermint in the western and midwestern United States was determined. Nit mutants were used to assign isolates to vegetative compatibility groups (VCGs). All isolates were assigned to VCG 2B except for one assigned to VCG 2A and two assigned to VCG 4A. VCG 2 isolates were found in all commercial mint growing regions, while the two VCG 4A isolates originated from southern Idaho. Pathogenicity assays on mint were performed using isolates from mint and other hosts, and pathogenicity assays were conducted on the potato cultivar Russet Norkotah using mint and potato isolates. Isolates originating from mint were significantly more aggressive on mint than were other host isolates, indicating that mint isolates were host-adapted. VCG 4A isolates from mint and potatoes were significantly more aggressive on potato than VCG 4B potato isolates and VCG 2B mint isolates. We speculate that the low VCG diversity of mint isolates may be due to the introduction of a single aggressive strain into Washington State mint fields via infected rhizomes.
Spatio-Temporal Analysis of Soybean Root Colonization by Fusarium solani f. sp. glycines in Fields
Authors: Luo Y. , Chong S. K. , Myers O.
Published: May 2007

Soybean roots were sequentially collected from two no-till fields from June 1997 through December 1998. Roots were ground to isolate and enumerate the fungus Fusarium solani f. sp. glycines, the causal agent of soybean sudden death syndrome (SDS), to obtain CFU per gram of root. The log CFU [log10(CFU + 1)] versus sampling time was used to produce the pathogen population curve, and the area under the pathogen population curve (AUPC) was calculated for each plot. The average log CFU from all plots for each sampling date was used to fit the logistic equation. Plot data of log CFU at each sampling time of the growing season, AUPC, and foliar disease index (FDX) were correlated with each other. Correlations among the log CFU in root residue in the winter of 1997, the log CFU and FDX in the 1998 growing season were also conducted. Geostatistics was applied to determine the spatial dependence in root colonization for different lag distance in the fields using semiviograms. Spatio-temporal autocorrelations of root colonization were studied using a computer model STAUTO. During the growing season, pathogen population in roots followed logistic growth in both fields. Pathogen populations in root residue decreased during the winter of 1997 and increased slightly in the spring of 1998 prior to planting. AUPC significantly correlated with FDX in both fields in 1997. Pathogen populations in root residue at three sampling dates in the winter of 1997 significantly correlated (r = 0.47 - 0.53) with FDX of the 1998 growing season in one field. No spatial dependence in root colonization was detected early in the growing season. However, some spatial dependence in certain directions of the fields was detected later in the growing seasons. Spatial dependence in AUPC in the across-rows direction was detected in both fields in 2 years. Spatial lag orders 0 and 1 were significantly correlated with temporal lag order 1 in both within-row and across-row directions in field 1 in 1997.
Response of Heterodera glycines and Soybean Cultivar to Tillage and Row Spacing
Authors: Chen S. Y. , Stienstra W. C. , Lueschen W. E. , Hoverstad T. R.
Published: May 2007

Heterodera glycines, commonly known as the soybean cyst nematode (SCN), has become a major factor in soybean production in the Midwest United States. The influence of five tillage treatments and two treatments of row spacing on SCN population dynamics and yield of SCN-resistant and -susceptible soybean cultivars was investigated in a corn-soybean rotation system in southern Minnesota from 1993 to 1996. No effects of tillage and row spacing were observed on nematode population density. As expected, the susceptible cultivar Sturdy consistently supported higher nematode densities than did the resistant cultivar Bell in 1993 to 1995 and Freeborn in 1996. Nematode reproduction varied among years. Predicted nematode density at equilibrium was 3,800, 13,000, 12,000, and 27,000 eggs per 100 cm3 of soil in plots with the susceptible cultivar and 480, 240, 430, and 700 eggs per 100 cm3 of soil in plots with the resistant cultivars in 1993, 1994, 1995, and 1996, respectively. The effects of tillage and row spacing on soybean yield were inconsistent. The resistant cultivars yielded 653, 195, and 435 kg/ha more (P < 0.05) than the susceptible cultivar in 1994, 1995, and 1996, respectively, but no yield difference between susceptible and resistant cultivars was observed in 1993. Planting resistant cv. Bell increased the yield of the following susceptible cv. Sturdy compared with continual planting of the susceptible cultivar. A sequence with continued resistant cultivar or cultivars, however, produced a higher overall yield and lower nematode density at the end of the 4-year rotation cycle than any sequence in which the susceptible cultivar was included. Yield of resistant and susceptible cultivars was negatively related to the SCN initial population density.
Characterization ofSeiridiumspp. Associated with Cypress Canker Based on ß-Tubulin and Histone Sequences
Authors: Barnes Irene , Roux Jolanda , Wingfield Michael J. , Coetzee Martin P. A. , Wingfield Brenda D.
Published: May 2007

Cypress canker is a serious disease that has devastated Cupressus spp. in many parts of the world. In Mediterranean Europe it has caused the deaths of millions of trees. Three species of Seiridium, S. cardinale, S. cupressi, and S. unicorne, are associated with cypress canker. Considerable debate surrounds the taxonomic status of these fungi. They have been viewed as a single morphologically variable species, three distinct taxa; or two species based on the presence or absence of conidial appendages. Studies based on ribosomal DNA (ITS1, ITS2, and 5.8S gene) sequence failed to separate the cypress canker fungi. In an attempt to distinguish between the species associated with cypress canker we used histone and partial ß-tubulin sequences of fourteen isolates of Seiridium spp. from cypress. Analysis of sequence data showed Seiridium isolates from Cupressus spp., residing in two major clades. One clade accommodated S. unicorne isolates from Portugal and South Africa. The other major clade consisted of two subclades containing non-appendaged S. cardinale isolates. We believe the larger second clade, represents the cypress canker pathogens while the other clade contains the less pathogenic S. unicorne, which has a host range beyond Cupressus. This study thus provides strong evidence to support previous morphological data suggesting three distinct species are associated with cypress canker.
First Recognition of Issatchenkia orientalis in Mature Citrus Fruits in Spain
Authors: Tuset J. J. , Perucho R.
Published: May 2007

During the first four months of 2000, mature fruit of clementine cvs. Clemenules and Hernandina, mandarin cvs. Ortanique and Fortune, and orange cv. Navelina from several packinghouses located in Valencia Province were affected by a soft, watery, colorless or very light brown decay. The incidence of the decay was 5 to 12% in clementines and mandarins and 0.2 to 0.8% in oranges. A yeast was isolated consistently on potato-dextrose agar from affected tissues and from the juice of decayed fruits. Colonies of this yeast were butyrous, light cream in color, and smooth with a dry surface (or with a flattened center) and lobed margins with sparse, branched pseudohyphae. Some isolates that were light pink in color later turned cream colored. Yeast cells were ovoid to elongate, single or in pairs, with one or two buds at one end (multilateral budding). The cells were 1.1 to 5.7 μm × 3.2 to 12.8 μm. Ascospores were not observed. Fermentation and growth on carbon sources (several carbohydrates), growth on nitrogen sources (nitrate, cadaverine, L-lysine, etc.), requirement for vitamins, and growth at 40°C were used for identification. Based on the results of such tests and morphological characteristics, the fungus was identified as Issatchenkia orientalis Kudryavtsev (anamorph: Candida krusei (Castellani) Berkhout) (2). To satisfy Koch's postulates in pathogenicity tests, cells from pure cultures on agar or in orange juice were inoculated by hypodermic injection into the peel and flesh of oranges, clementines, mandarins, grapefruits, and lemons. After 10 to 20 days in a moist chamber at 24°C, a decay resembling symptoms that occurred in the packinghouse were observed in the inoculated fruits (1,3). The lemon fruits were the most affected. The fungus reisolated from decayed fruits was identical to the original isolates. This is the first report of this yeast as a decay of citrus produced in Europe. Climatic conditions (rainfall in spring and dry in summer and autumn) in citrus-growing areas in Spain, together with the presence of the Mediterranean fruit fly, may have been factors in disease development. A similar decay is caused by Geotrichum candidum, and previously this may have been mistaken for decay caused by I. orientalis.

References: (1) P. R. Harding. Plant Dis. Rep. 52:433, 1968. (2) C. D. Kurtzman. 1998. The Yeasts, A Taxonomic Study. 4th ed. Elsevier Science, Amsterdam. (3) K. V. Shankhapal and V. G. Hatwalne. Plant Dis. Rep. 60:237, 1976.
Okra (Hibiscus esculentus)—A New Host of Turnip mosaic virus in Israel
Authors: Gera A. , Lampel M. , Cohen J. , Rosner A.
Published: May 2007

In July 1999, Hibiscus esculentus plants, grown in garden plots in Galilee, Israel, exhibited chlorosis, vein clearing accompanied by necrosis, and growth reduction. All samples (n = 10) tested positive for Turnip mosaic virus (TuMV) in enzyme-linked immunosorbent assay (ELISA), using a polyclonal antibody produced in our laboratory against purified virus. Virus in crude sap extracted from symptomatic tissue was mechanically transmitted to Chenopodium quinoa, C. amaranticolor, Nicotiana tabacum Xanthi nc and White Burley, N. clevelandii, N. benthamiana, N. sylvestris, and N. rustica, all of which developed symptoms characteristic of TuMV infection (1). ELISA testing of leaf sap extracted from mechanically inoculated indicator plants gave a strong positive reaction to TuMV. Leaf dip preparations of H. esculentus were analyzed by transmission electron microscopy. Filamentous virus particles typical of a potyvirus were observed in samples from symptomatic leaves. General primer pairs, which cover the complete 3′-end of the potyvirus genome were used in a reverse transcription-polymerase chain reaction assay (RT-PCR), gave an expected amplification product of approximately 300 bp. The nucleotide sequence of the PCR product was 97% identical to the CP sequence of other TuMV, thus verifying TuMV infection of H. esculentus. This is the first report of H. esculentus infection by TuMV.

Reference: (1) A. Gera et al. J. Phytopathol. 145:289-293, 1997.