bluuebunny/crossref_metadata_2025 huggingface dataset:
A Cowpea Seed Rot Disease Caused by Fusarium equiseti Identified in Nigeria
Authors: Aigbe S. O. , Fawole B. , Berner D. K.
Published: May 2007

Fusarium equiseti (Corda) Sacc., reported on cowpea (Vigna unguiculata (L.) Walp.) seeds in India (2), was isolated for the first time in Nigeria from naturally infected cowpea seeds. Cowpea, cv. IT90K-76, seeds (400) from plants grown in Nigeria were surface-disinfested in 0.05% NaOCl and placed on moist filter paper in petri dishes (10 seeds per dish) and then in a dark incubator for 4 days at 27°C. After incubation, some seeds had fungal mycelia growing on their surfaces. When cultured on potato dextrose (PDA) and Spezieller Nährstoffarmer (SNA) agars, the fungi produced macroconidia characteristic of F. equiseti (1). Septate macroconidia were three to six celled with extended apical and distinctive foot-shaped basal cells. F. equiseti was recovered from 4.25% of seeds, and incidence correlated positively with development of seed rot symptoms. To confirm pathogenicity, 80 cowpea seeds were surface-disinfested with NaOCl, and 40 were soaked for 6 h in a suspension of 3 × 105 conidia of F. equiseti per ml of water. The remaining seeds were soaked in sterile distilled water. After incubation, white mycelia developed on 87.5% of seeds soaked in the conidial suspension and rotted without germinating. Only 5% of seeds soaked in sterile water developed seed rot symptoms. When cultured on PDA and SNA, fungi isolated from artificially infested seeds with rot symptoms again were identified as F. equiseti.

References: (1) P. E. Nelson et al. 1983. Fusarium species: An illustrated Manual for Identification. Pennsylvania University Press, University Park. (2) O. K. Sinha and M. N. Khare. Seed Sci. Technol. 5:721, 1977.
First Report of Acidovorax avenae subsp. citrulli as a Pathogen of Cucumber
Authors: Martin H. L. , O'Brien R. G. , Abbott D. V.
Published: May 2007

In March 1999, a foliar bacterial disease was observed in a commercial crop of cucumber (Cucumis sativus L.) cv. Jetset in Gumlu in northern Queensland, Australia. Initial symptoms consisted of angular, chlorotic, water-soaked lesions that later dried to necrotic areas of light brown, dead tissue. White bacterial ooze was commonly found on the undersides of young water-soaked lesions. Lesions were delimited by veins and distributed uniformly over leaf surfaces, and more than 20% of the crop was affected. No symptoms were observed on plant stems or fruits. Bacterial streaming from the edges of freshly cut young lesions was clearly visible in a droplet of water under ×100 magnification in the laboratory. Isolations were made from young lesions on King's medium B (1). A slow-growing, white, gram-negative, nonfluorescent bacterium was consistently isolated. Three isolates of the bacterium were identified, using the Biolog software program (Biolog, Hayward CA), and in each instance, the bacterium was confirmed as Acidovorax avenae subsp. citrulli, with a similarity of >0.80. Koch's postulates were completed with 8-day-old glasshouse-grown cucumber (cv. Jetset) seedlings. Seedlings were misted until runoff with a bacterial suspension of 3 × 108 CFU/ml and enclosed in plastic bags for ≈30 h at 22°C. Water-soaked lesions were observed on cucumber cotyledons 4 days after inoculation. This is the first report of A. avenae subsp. citrulli as a pathogen of cucumber.

Reference: (1) E. O. King et al. J. Lab. Clin. Med. 44:301, 1954.
First Report on Natural Occurrence of Tomato Spotted Wilt Tospovirus in Basil (Ocimum basilicum)
Authors: Holcomb G. E. , Valverde R. A. , Sim J. , Nuss J.
Published: May 2007

Virus-like symptoms were observed on basil plants (Ocimum basilicum L. ‘Mrs. Burns Lemon’ [MBL]) growing in containers and a demonstration plot at the Louisiana State University Burden Research Plantation, Baton Rouge, during July 1998. Symptoms consisted of ring spots, leaf distortion, and severe mosaic. Mechanical transmission of the suspect virus by sap inoculation from infected MBL to basil cvs. MBL, Aussie Sweet, Cinnamon, Siam Queen, and Sweet Dani was successful. Symptoms were similar to those on infected MBL. Nicotiana benthamiana Domin. reacted with local chlorotic spots followed by severe yellows, necrosis, and death. Electron microscopy of thin sections of infected basil revealed virus inclusions but no virus particles. However, infected N. benthamiana revealed the presence of 82-nm membrane-bound particles in the cytoplasm. The virus was identified from basil and N. benthamiana as the common strain of tomato spotted wilt tospovirus (TSWV) by enzyme-linked immunosorbent assay (Agdia, Elkhart, IN). An outbreak of thrips insects during the summer drought in 1998 was probably responsible for the occurrence of TSWV in basil. This is the first report of the occurrence of TSWV in basil (1).

Reference: (1) A. A. Brunt et al., eds. 1996. Plant Viruses Online: Descriptions and Lists from the VIDE Database. Published online by Australian National University, Canberra.
First Report of Fusarium oxysporum f. sp. lycopersici Race 2 on Tomato in Italy
Authors: Stravato V. M. , Buonaurio R. , Cappelli C.
Published: May 2007

During the summer of 1997, symptoms of Fusarium wilt were observed on tomato (Lycopersicon esculentum Mill.) cvs. Monica F1 and PS 110, which bear the I gene for resistance to race 1 of Fusarium oxysporum Schlechtend.:Fr. f. sp. lycopersici (Sacc.) W.C. Snyder & H.N. Hans., in two commercial production greenhouses in Latium (Fondi) and one greenhouse in Sardinia (Oristano). Infected plants showed yellowing, stunting, vascular discoloration, and premature death. A fungus from tomato stems with discolored vascular tissue was consistently isolated on potato dextrose agar (PDA) and, based on morphological features, was identified as F. oxysporum. To verify the pathogenicity of four fungal isolates, cv. Bonny Best tomato plants, which do not carry genes for Fusarium wilt resistance, were inoculated by dipping roots of 2-week-old seedlings in a suspension of 105 microconidia per ml for 30 s. Inocula were obtained from 1-week-old fungal cultures grown on PDA. Roots of control plants were dipped in water. Seedlings were transplanted to pots containing peat and river sand (1:1, vol/vol) and placed in a greenhouse at 20 to 25°C. One month after inoculation, all fungal isolates provoked wilting of inoculated plants. No symptoms were observed on control plants. The morphological features of the fungus reisolated from diseased plants were similar to those of the original isolates. Based on the pathogenicity test, we concluded that the fungal isolates belong to F. oxysporum f. sp. lycopersici. To determine the races of the fungal isolates, differential tomato lines VFN8 (I gene for resistance to race 1), Florida MH-1 (I and I2 genes for resistance to races 1 and 2), and I3R (I, I2, and I3 genes for resistance to races 1, 2, and 3) were inoculated with the four fungal isolates, using the same procedure described for the pathogenicity test. Because disease symptoms were detected on VFN8 but not on Florida MH-1 and I3R, we deduced that the fungal isolates belong to F. oxysporum race 2. This is the first report of F. oxysporum f. sp. lycopersici race 2 in Italy. Previous research indicated that race 1 is present in Italy (1). Currently, many commercially acceptable cultivars resistant to races 1 and 2 are available to Italian greenhouse growers.

Reference: (1) M. Cirulli. Phytopathol. Mediterr. 4:63, 1965.
First Report of Potato Spindle Tuber Viroid in Costa Rica
Authors: Badilla R. , Hammond R. , Rivera C.
Published: May 2007

During 1997 to 1998, symptoms of leaf roll, dwarfism, chlorosis, and occasional leaf necrosis were observed on Solanum tuberosum in several plots in Cartago, the principal potato-production region of Costa Rica. Because of the known association between potato leafroll virus (PLRV) and viroids (1) and previous reports of PLRV in Costa Rica, the presence of potato spindle tuber viroid (PSTVd) was suspected. Leaf samples from 122 symptomatic potato plants, cvs. Atzimba, Floresta, Idiafrit, and Birris, were collected from 10 plots. Total nucleic acids (TNAs) were extracted and purified (2) from collected symptomatic samples and six healthy potato controls. TNAs were spotted on nylon membranes and hybridized to a digoxigenin-labeled DNA probe specific for PSTVd. Of 122 symptomatic plants, 71 were positive for PSTVd based on dot blot hybridization. TNAs from 12 positive potato samples, including at least 1 sample from each cultivar, were used to inoculate Lycopersicum esculentum cv. Super Marmande. Eleven of twelve inoculated tomato plants showed symptoms of dwarfism, leaf deformation, and grayish foliage, often with a dull surface. TNAs were extracted from inoculated tomato and hybridized to the PSTVd probe. All inoculated symptomatic plants were positive for PSTVd based on dot blot hybridization. This is the first report of PSTVd in Costa Rica.

References: (1) M. Querci et al. J. Gen. Virol. 78:1207, 1997. (2) W. Villalobos et al. Rev. Biol. Trop. 45:983, 1997.
First Report of Tomato Yellow Leaf Curl Geminivirus in Morocco
Authors: Peterschmitt M. , Granier M. , Aboulama S.
Published: May 2007

In July 1998, shortened internodes, reduced leaf size, leaf curling, and bushy plants were observed in tomato crops in the coastal region near Casablanca, Morocco. The symptoms were similar to those described for tomato yellow leaf curl virus (TYLCV) disease. During September, the disease was present in more than 130 ha of outdoor and protected crops. Economic losses ranged between 20 and 100%. Similar symptoms were observed in tomato crops in the northeastern region of Morocco. During the same period, high populations of Bemisia tabaci (Gennadius) were observed on tomato, sweet pepper, and several weeds, including Sonchus oleraceus L., Chenopodium sp., Malva parviflora L., and Datura stramonium L. Attempts to control whiteflies with insecticides generally were unsuccessful. Using a pair of degenerate primers (3) that are expected to amplify a region of the A component of begomoviruses between the intergenic conserved nonanucleotide sequence and the first 5′ quarter of the capsid protein gene, an expected size product of 500 bp was obtained from six tomato leaf samples collected near Casablanca: four were obtained from symptomatic plants and two from apparently symptomless plants. A product of the same size was obtained from a sample of tomato infected with a TYLCV isolate from Reunion Island, France (2), but not from a sample from symptomless tomato plants from Reunion. The polymerase chain reaction (PCR) product obtained from one symptomatic sample from Morocco was cloned and sequenced (2). The resulting sequence (EMBL no. AJ133491) was at least 95.2% identical to sequences of TYLCV isolates from the Dominican Republic (EMBL no. AF024715), Cuba (EMBL no. AJ223505), Israel (EMBL no. X15656; EMBL no. X76319 for the mild clone), Spain (EMBL no. AF071228), and Reunion (EMBL no. AJ010790). Based on sequence comparisons, the tomato leaf sample was infected by a geminivirus isolate belonging to the Israeli species of TYLCV and was most closely related to the Dominican Republic isolate (98.4% nucleotide identity). In symptomless plants from which a 500-bp PCR product was obtained, infection may have been in an early stage. This is consistent with the fact that in the 2-ha field from which tomato samples were collected, only 4% of the plants exhibited TYLCV symptoms at the time of collection, whereas at least 70% of plants showed symptoms later, requiring the farmer to abandon the crop. The presence of the Eastern Mediterranean TYLCV species in a Western Mediterranean country is not a new observation; this virus has been described in Spain and Portugal (1). In Morocco, TYLCV symptoms were observed during the 1996 to 1997 growing season, following importation of grafted tomato plants from the Netherlands, by a farmer from the Casablanca region.

References: (1) J. Navas-Castillo et al. Plant Dis. 83:29, 1999. (2) M. Peterschmitt et al. Plant Dis. 83:303, 1999. (3) P. Umaharan et al. Phytopathology 88:1262, 1998.
Cross-Protection of Grapefruit from Decline-Inducing Isolates of Citrus Tristeza Virus
Authors: Powell C. A. , Pelosi R. R. , Rundell P. A. , Stover E. , Cohen M.
Published: May 2007

The ability of three mild isolates of citrus tristeza virus (CTV) to prevent natural infection of 84 Ruby Red grapefruit on sour orange rootstock by aphid-transmitted, decline-inducing isolates of CTV was assessed by symptoms and verified by enzyme-linked immunosorbent assay (ELISA) after 16 years. Of 21 trees in each of four treatments protected by the DD 102 bb, Guettler HS, and DPI 1-12-5-X-E mild CTV isolates, 14, 10, and 14% were infected by severe isolates (MCA13 monoclonal antibody reactive) compared with 67% for unprotected control trees. The health of trees protected by the DD 102 bb CTV isolate was significantly better than that of unprotected control trees as measured by decline, tree ratings, and tree height. These data suggest that infection by certain mild isolates of CTV can cross-protect grapefruit trees on sour orange rootstock from decline-inducing isolates of CTV that are prevalent in the Indian River region of Florida.
Effects of Seedborne Potato Leafroll Virus on Russet Norkotah Potato
Authors: Hamm P. B. , Hane D. C.
Published: May 2007

Tuber yield and quality of cv. Russet Norkotah potato plants grown from seed infected with potato leaf roll virus (PLRV) were compared with tuber yield and quality of adjacent plants grown from virus-free seed. Plants from PLRV-infected seed produced at least 60% less total yield and 88% less marketable yield (tubers >85 g) than plants grown from healthy seed. PLRV-infected seed also produced plants with fewer and smaller tubers than plants grown from healthy seed. No compensatory yield was measured in plants grown from PLRV-free seed growing adjacent to plants from PLRV-infected seed.
First Report of Capsicum annuum Plants Infected by Tomato Yellow Leaf Curl Virus
Authors: Reina J. , Morilla G. , Bejarano E. R. , Rodríguez M. D. , Janssen D.
Published: May 2007

Infection of tomato crops by tomato yellow leaf curl virus (TYLCV) has occurred annually in southern Spain since 1992. In 1997, TYLCV also was reported in common bean (Phaseolus vulgaris) (2) in southern Spain. During the summer of 1999, we observed pepper plants (Capsicum annuum) from a greenhouse in Almería (Spain) exhibiting clear leaf internervial and marginal chlorosis and upward curling of the leaflet margin. Total nucleic acids were extracted from five plants with symptoms and analyzed by Southern blot hybridization and polymerase chain reaction (PCR). As a probe, we used a plasmid (pSP72/97) encompassing the complete genome of the Spanish isolate of TYLCV-IS (1). A positive signal was obtained from three samples. A pair of primers (OTYA3/OTYA6) designed to amplify TYLCV was used for detection in samples (OTYA3: GGGTCGACGTCATCAATGACG; OTYA6: CTACATGAGAATGGGGAACC). Using PCR, we were able to obtain fragments of the expected sizes (649 bp for OTYA3/OTYA6) from four of five samples analyzed. Amplified fragments were later analyzed by restriction fragment length polymorphism with three cutter enzymes (AluI, RsaI, and HinfI). The restriction pattern obtained in all cases corresponded with the Spanish isolate of TYLCV-IS. One of the fragments amplified with OTYA3/OTYA6 was fully sequenced. The sequence was 100% identical to that previously reported for the Spanish isolate of TYLCV-IS. This is the first report of TYLCV infection in C. annuum, which is one of the most important commercial crops in southeastern Spain. Work is in progress to determine whether the presence of TYLCV-IS in pepper plants is responsible for the symptoms described here.

References: (1) J. Navas-Castillo et al. Plant Dis. 81:1461, 1997. (2) J. Navas-Castillo et al. Plant Dis. 83:29, 1999.
Characterization ofAgrobacterium vitisStrains Isolated from FeralVitis riparia
Authors: Burr T. J. , Reid C. L. , Adams C. E. , Momol E. A.
Published: May 2007

Agrobacterium vitis was isolated from roots of 41 of 66 feral Vitis riparia vines collected in three different regions of New York State. Two of the regions were more than 150 km from commercial vineyards. The strains were highly diverse as determined by DNA fingerprinting of the chromosomal region lying between the 16S and 23S rRNA genes. Of 24 strains examined, 15 different fingerprints were generated, and none was identical to fingerprints generated by previously identified groups of tumorigenic A. vitis strains. Results of physiological tests that were done to characterize strains from V. riparia conformed closely to those expected for A. vitis, except that 23 of 26 strains did not utilize tartrate. All strains were nontumorigenic, did not hybridize with a probe consisting of T-DNA genes, did not utilize octopine or nopaline, and carried zero to three plasmids. Of 26 strains, 7 inhibited A. vitis strain K306 from causing galls at wound sites on grape as well as or better than a previously studied nontumorigenic A. vitis strain, F2/5, that is known to have biological control activity.
First Report of Powdery Mildew on Dollar-plant (Crassula ovata) Caused by an Oidium sp.
Authors: Kiss L.
Published: May 2007

Dollar-plant (Crassula ovata) is a perennial, succulent ornamental grown worldwide. In 1998, powdery mildew colonies were observed on the adaxial leaf surfaces of a 4-year-old specimen maintained outdoors. Symptoms included necrosis of the infected tissues and defoliation 2 months after the appearance of the first colonies. Conidia were produced in chains on unbranched conidiophores. Hyphal appressoria were lobed to multi-lobed, mostly opposite or spread. Conidia were ellipsoid to cylindrical, measured 34 to 48 μm × 17 to 26 μm, and contained no fibrosin bodies. On water agar, conidia produced a single germ tube from the end of the conidium. Germ tubes were either very short with lobed appressoria, or were two to three times longer than conidia, and terminated in lobed or unlobed appressoria. Cleistothecia were not produced. The pathogen was identified as an Oidium sp. belonging to the genus Erysiphe sect. Galeopsidis (1). To confirm pathogenicity, small, potted C. ovata plants were placed near the diseased plant in the laboratory. After 2 weeks, powdery mildew appeared on the small plants, and the pathogen was morphologically identical to the original fungus. This is the first report of a powdery mildew fungus on C. ovata, and it is different from both species of the Erysiphaceae identified on other Crassula spp. (1,2). Infected C. ovata leaves were deposited at the Department of Botany of the Hungarian Natural History Museum in Budapest under the accession number BP 91732.

References: (1) U. Braun. 1995. The Powdery Mildews (Erysiphales) of Europe. Gustav Fischer Verlag, Jena. (2) D. F. Farr et al. 1989. Fungi on Plants and Plant Products in the United States. American Phytopathological Society, St. Paul, MN.
First Report of the Teleomorph of an Oidium sp. Causing Powdery Mildew on Flowering Dogwood in South Carolina
Authors: Williamson M. R. , Blake J. H.
Published: May 2007

Prior to 1994, powdery mildew had rarely been reported on flowering dogwood (Cornus florida) in the southeastern U.S. That year, and every year since, epiphytotics of powdery mildew have occurred. Leaf symptoms include distortion and necrotic areas on young leaves and an increase in red pigmentation surrounding infection sites. Young seedlings may be stunted by this disease and growth of older trees may be slowed (2). In early November, 1996, dogwood (C. florida) trees at 10 locations each in Anderson, Oconee, and Pickens counties in northwestern South Carolina were surveyed for the presence of powdery mildew. Leaves with signs of powdery mildew (white, powdery patches of mycelium, conidiophores, and conidia) were examined with a ×10 hand lens and leaves with cleistothecia were collected and taken back to the laboratory. Numerous leaves from each site were first examined at ×50 on a dissecting microscope to observe gross morphological features of cleistothecia. Then, approximately 10 cleistothecia from each of two sites were examined on a compound microscope at ×100 or higher to make further observations and measurements. Cleistothecial diameter ranged from 75.0 to 92.5 μm (average 81.8 μm). Appendages, which averaged 6 to 11 per cleistothecium, were 110 to 140 μm long (average 125.7 μm) or 1.54 times the cleistothecial diameter. The apices of appendages were dichotomously branched 2 to 3 times and the tips were distinctly re-curved. The stalks were aseptate and hyaline. Cleistothecia contained 3 to 5 asci. Each ascus contained 2 to 6 ascospores measuring 18 to 28 × 13 to 15 μm. Based on these characteristics, the teleomorph was tentatively identified as Microsphaera pulchra. Cleistothecia were found to be slightly smaller and the number of appendages fewer than Braun's lectotype (1), but these differences were judged to be of minor importance. Therefore, we conclude that the teleomorph of the Oidium sp., herein reported on flowering dogwood for the first time in South Carolina, is Microsphaera pulchra

References: (1) U. Braun. Nova Hedwigia 89:1, 1987. (2) L. A. Klein et al. Plant Dis. 82:383, 1998.
First Report of Phoma herbarum and Phoma exigua as Pathogens of Dandelion in Southern Ontario
Authors: Neumann Brebaum S. , Boland G. J.
Published: May 2007

Diseases of dandelion (Taraxacum officinale) were surveyed in southern Ontario from 1993 to 1997 to identify promising pathogens for biological weed control. Two new pathogens of dandelion, Phoma herbarum Westend. and Phoma exigua Desm., were recovered and characterized from small necrotic lesions on dandelion foliage. Both Phoma spp. were frequently isolated from multiple locations and during various years of the survey, indicating that they were endemic and widespread on T. officinale in southern Ontario. Pathogenicity was assessed by inoculating detached leaves or seedlings with colonized agar disks (6 mm in diameter) or spore suspensions (1 × 106 conidia per ml). Inoculated leaves and seedlings were incubated at 22°C and 48 h of continuous leaf wetness. Lesion diameters were measured 3 days post-inoculation. Isolates that gave rise to necrotic lesions were reisolated from leaves and grown in pure culture. Their growth characteristics were compared with those of the initial isolate. Spores were ellipsoid, hyaline, and 5 × 2 μm for both species. Identification of representative isolates of both species was confirmed by the Centraalbureau voor Schimmelcultures, Oosterstraat 1, 3742 SK Baarn, The Netherlands. This is the first report of these two species as pathogens of dandelion in North America (1,2).

References: (1) I. L. Conners 1967. An Annotated Index of Plant Diseases in Canada. Research Branch, Canada Dept. Agric. Pub.1251. (2) D. F. Farr et al. 1989. Fungi on Plants and Plant Products in the United States. American Phytopathological Society, St. Paul, MN.
Specific Detection of Cherry Mottle Leaf Virus Using Digoxigenin-Labeled cDNA Probes and RT-PCR
Authors: James D. , Jelkmann W. , Upton C.
Published: May 2007

Cherry mottle leaf virus (CMLV)-associated double-stranded RNA (dsRNA) was isolated from the propagation host Chenopodium quinoa. The dsRNA band, with a molecular weight estimated at 7.0 × 106 Da, was used to produce cDNA. Two recombinant plasmids from the cloned cDNA library were identified that specifically bound with CMLV-associated RNA in dot blot hybridization studies. The cDNA inserts were sequenced, and oligonucleotide primers were designed that specifically amplify an 848-bp fragment of the CMLV genome by reverse-transcription polymerase chain reaction. Also, a poly(T) primer was reliably used for reverse transcription, with specific amplification using the CMLV primers, suggesting polyadenylation of the virus genome. Search of the database revealed some sequence homology of the partially characterized genome of CMLV with that of apple chlorotic leafspot virus. Additional sequence data are required, however, to establish the taxonomic position of the filamentous CMLV.
Foliar Fungicides as Protective Seed Piece Treatments for Management of Late Blight of Potatoes
Authors: Powelson Mary L. , Inglis Debra A.
Published: May 2007

Fungicides receiving Section 18 emergency exemptions for management of the foliar phase of late blight of potato were evaluated as protective treatments for control of tuberborne inoculum of Phytophthora infestans in greenhouse and field studies. Three Section 18 products, Acrobat MZ (dimethomorph + mancozeb), Curzate M-8 (cymoxanil + mancozeb), and Tattoo C (propamocarb hydrochloride + chlorothalonil), when applied to the seed piece prior to inoculation with P. infestans, significantly (P ≤ 0.05) increased sprout emergence, compared with the inoculated water control. Of the three Section 18 products, Curzate M-8 was frequently the most effective. The increase in plant emergence with the protective seed piece treatment was seen with cultivars that differ in susceptibility to late blight, two genotypes (US-8 and US-11) of P. infestans, zoospore and sporangial inocula, and at different inoculation sites on the seed piece. In greenhouse studies, percent emergence with the protective seed piece treatments averaged 74% for cv. White Rose and 44% for cv. Shepody, compared with 9 and 8% for the inoculated water control of the respective cultivars. In field studies, when inoculum was placed either adjacent to or 4 cm away from the sprout, plant emergence of the inoculated water control was 12 and 36%, respectively. Application of the fungicides to the seed piece prior to inoculation increased emergence by an average of 700 and 212% for the respective inoculation sites. There was no evidence for translocation of the fungicides to the emerging foliage in concentrations high enough to prevent foliar infection from airborne inoculum of P. infestans. Control of tuberborne inoculum of P. infestans with appropriate seed piece treatments will result in an increase in plant emergence and improved crop uniformity.
First Report of Sinaloa Tomato Leaf Curl Geminivirus in Costa Rica
Authors: Idris A. M. , Rivas-Platero G. , Torres-Jerez I. , Brown J. K.
Published: May 2007

In October 1998, geminivirus-like symptoms were widespread in tomato plantings near Turrialba, Costa Rica. Isolates from several fields were experimentally transmitted to tomato seedlings with whiteflies from a Bemisia tabaci (Genn.) colony maintained at CATIE, which resulted in interveinal chlorosis and leaf curling symptoms indistinguishable from those observed in the field. Total DNA was extracted from leaves of 16 of these experimentally inoculated plants and assayed by polymerase chain reaction (PCR) for the presence of begomovirus DNA with the degenerate primers AV324 and AC889 (2) to amplify the core region of the coat protein gene (core Cp). PCR yielded the expected size core Cp fragment (576 bp) from 16 of 16 samples. The core Cp fragments of six samples were cloned and sequenced. A comparison of the core Cp sequences with reference begomovirus sequences indicated all Costa Rican isolates were >95% identical to Sinaloa tomato leaf curl geminivirus reported in 1994 from Sinaloa, Mexico (STLCV-SINALOA). Virus identity was confirmed by multiple sequence alignments of the viral coat protein gene (Cp) and the common region (CR) sequences of A and B components (CR-A and CR-B), respectively, with analogous reference begomovirus sequences. Cp and CRs were obtained by PCR, and amplicons were cloned and sequenced as described (1). The Cp open reading frame (ORF; 756 nucleotides) (AF110515) identified within the A component amplicon shared 92.9% sequence identity with STLCV-SINALOA Cp (AF040635). The CR sequences of the A (AF1150516) and B (AF110517) components (163 nucleotides) shared 98.2% sequence identity with each other, suggesting that they were amplified from the cognate A and B components of the same virus. Further, the CR-A and CR-B components contained the same putative Rep binding site, TGGGGT-AA-TGGGGT, which was also identical to that of STLCV-SINALOA. The mean percent divergences between viral Cp and CR amplicons (n = 6+) ranged from 98 to 100%. Collectively, STLCV-like symptoms in tomato, >92% identity between viral Cp sequences, and identical CR iterons indicate that the Costa Rican tomato virus is STLCV, or a closely related strain. This is the first report of an STLCV-like begomovirus in tomato in Costa Rica (STLCV-CR).

References: (1) A. M. Idris and J. K. Brown. Phytopathology 88:648, 1998. (2) S. D. Wyatt and J. K. Brown. Phytopathology 86:1288, 1996.
First Report of Chino del Tomate and Pepper Hausteco Geminivurses in Greenhouse-Grown Tomato in Sonora, Mexico
Authors: Idris A. M. , Lee S. H. , Brown J. K.
Published: May 2007

Tomato plants grown in commercial greenhouses in Sonora, Mexico, developed either yellow mosaic, leaf curling, and stunting (phenotype 1; 20 to 35%) or chlorosis and a feathery appearance of leaves (phenotype 2; 15 to 25%) in December 1997 and again in October 1998. Polymerase chain reaction (PCR) with diagnostic primers (prAV324 and prAC889) that amplify an approximately 576-bp fragment of the coat protein (CP) gene of whitefly-transmitted geminiviruses indicated the presence of a begomovirus. Biolistic inoculation of tomato seedlings with RNase-treated extracts of three symptomatic tomato samples, each, resulted in reproduction of disease symptoms. With PCR primers prAV2644 and prAC1154 (1), the entire CP (approximately 776 bp) and its flanking sequences were amplified from extracts of symptomatic tomato, and amplicons were cloned and sequenced. Comparisons of a minimum of three CP gene sequences from each phenotype revealed the presence of at least two begomoviruses. The phenotype 1-associated CP gene shared 92.6, 86.2, and 85.3% identity with the CP sequence of chino del tomate (CdTV) [AF106936], tomato mottle, and abutilon mosaic geminiviruses, respectively. The CP sequence associated with phenotype 2 was 94.6, 77.1, and 77.1% identical to pepper hausteco (PHV) [X70418], bean golden mosaic-Guatemala (BGMV-GU), and Texas pepper (TPV) gem-iniviruses, respectively. Previously, CdTV was reported from tomato in Chiapas, Morelos, Sinaloa, and Tamaulipas, Mexico, while PHV has been identified in Guanajuato, Quintana Roo, Sinaloa, and Tamaulipas, Mexico, and in Texas (2). This is the first report of CdTV-like (>92% identity) and PHV-like (>94% identity) geminiviruses associated with greenhouse-grown tomatoes in Sonora, Mexico.

References: (1) A. M. Idris and J. K. Brown. Phytopathology 88:648, 1998; (2) I. Torres-Pacheco et al. Phytopathology 86:1186, 1996.
First Report of Yellow Leaf Syndrome of Sugarcane in Morocco
Authors: Abdelmajid Nadif , Mohamed Akalach , Cronje Pieter , Jones Phil
Published: May 2007

Yellow leaf syndrome of sugarcane (Saccharum officinarum L.) has been described from a number of cane-growing countries. Symptomatic leaves were collected from the CTCS and other localities of the Gharb region. The first symptoms were observed on cv. CP 66-346 as a reddening of the adaxial leaf surface; in other cultivars, particularly cv. CP 72-1210, the older leaf midribs turned bright yellow, followed by yellowing of the blade starting from the leaf tip and spreading downward. The older leaves dried out and in severe cases the plant died. The disease is widespread in both the Gharb and Loukkos cane-growing regions. Severe symptoms were observed in the spring of 1998 following a 5-month drought and an atypical flowering of the cane (in Morocco cane has not flowered for the past 25 years). Sugarcane yellow leaf phytoplasma was identified by the amplification of a band of the expected size of approximately 1,250 bp following nested PCR (polymerase chain reaction) with universal primers in samples of CP 66-346, LCP 85-384, and clones originated from fuzz, but not in cultivars CP 74-383 and CP 72-1210. This is the first report of yellow leaf syndrome on sugarcane in Morocco.
First Report of Bean Leafroll Luteovirus Infecting Pea in Italy
Authors: Larsen R. C. , Webster D. M.
Published: May 2007

Approximately 5,000 ha of processing peas (Pisum sativum L) are cultivated annually in the Po River Valley of northern Italy. During the 1998 growing season, affected pea plants in this region were observed that exhibited mild chlorosis and mottling, leaf rolling, and stunting symptoms. High aphid populations and disease levels of nearly 100% were observed in susceptible varieties. Samples from affected fields were analyzed for the presence of bean leafroll virus (BLRV). Nonviruliferous pea aphids (Acyrthosiphon pisum Harris) received a 48-h acquisition access period on symptomatic leaves. Aphids were then transferred to Puget pea and Diana faba bean for a 72-h inoculation access period. Leaf samples were also macerated in 0.05 M potassium phosphate pH 7.4, and inoculated mechanically to pea, faba bean, chickpea (Cicer arietinum L.), Chenopodium quinoa Willd., and C. amaranticolor Coste & Reyn. Symptoms typical of those observed in the original field plants appeared 10 to 14 days after aphid transmissions in both pea and faba bean inoculated with pea aphids. No symptoms were observed in any of the hosts that were inoculated mechanically. Total nucleic acid extracts from the original pea samples, and from leaf tissue of pea and faba bean plants inoculated with aphids, served as templates in reverse-transcriptase polymerase chain reaction assays. Primers BLR-V157 and BLR-C546, which flanked a 400-bp fragment, were designed with available sequence data for the coat protein gene of BLRV (1). An amplification product of the expected size was generated from symptomatic plants but not from healthy controls. Sequence analysis of the cloned fragments revealed a 99% nucleic acid homology with the published sequence for BLRV and an isolate obtained from alfalfa in Washington State (R. Larsen, unpublished). This is the first report of BLRV in Italy.

Reference: (1) B. Brill et al. Nucleic Acids Res. 18:5544, 1990.
Soybean Varietal Response and Yield Loss Caused by Sclerotinia sclerotiorum
Authors: Yang X. B. , Lundeen P. , Uphoff M. D.
Published: May 2007

Soybean Sclerotinia stem rot, caused by Sclerotinia sclerotiorum, has recently emerged from being a minor problem in areas where soybeans of maturity groups 0 to I are grown to a significant cause of soybean yield losses in the north-central region, which produces 80% of soybean in the United States. Studies were conducted in Iowa to quantify varietal response to S. sclerotiorum for cultivars of maturity groups I to III in fields that had uniform infestation histories. Over the course of the study, disease incidence was generally high at the northern Iowa sites but low in central Iowa, with disease incidence of susceptible standards >60% and <30%, respectively. Regression analysis showed that maturity class significantly affected disease incidence, with greater effects in environments where susceptible standard cultivars had high disease incidences. Consistency of varietal response among the environments was quantified using Pearson correlation analysis. When disease incidence was high, varietal responses measured by disease ratings and yield were consistent among locations, but the responses were inconsistent when disease incidence was low. Pearson correlation coefficients ranged from 0.80 to 0.94 for disease incidence and 0.58 to 0.81 for yield among the experiments having high disease incidence in susceptible standards. The relationship between disease incidence and yield was well described by linear regression models with coefficients of determination (r2) ranging from 0.59 to 0.83. Based on regression slopes (significant at P < 0.0001), yield losses are estimated to range from 170 to 335 kg/ha for each 10 percentage points of disease incidence. Regression analysis also showed that maturity groups had a linear relationship with disease incidence (r2 = 0.18 to 0.39, P < 0.01).
Survival of Colletotrichum dematium in Soil and Infected Mulberry Leaves
Authors: Yoshida S. , Shirata A.
Published: May 2007

Overwinter survival of Colletotrichum dematium, the causal agent of mulberry anthracnose, was examined in Japan. Conidia and infected mulberry leaves were mixed with soil and placed on the ground in early December. Viability of conidia declined rapidly under field conditions—they could not be recovered within 30 days—whereas conidia placed indoors or outdoors under a roof protected from rain and snow survived longer. When a suspension of soil infested with conidia was used to inoculate detached healthy leaves, no infection was detected after 65 days of incubation, suggesting that conidia in soil are not a significant form of overwintering inoculum. When infected or latently infected leaves incubated in soil under field conditions were used as inoculum on leaves, it was shown that the fungus remained viable for at least 150 days. The fungus in infected leaves maintained under laboratory conditions at different temperatures survived for at least 90 days at 25 and 35°C and for 600 days at 0°C. These results suggest that C. dematium can overwinter in infected or latently infected leaves, and that these leaves can be a source of primary inoculum the following year. Hence, the elimination of fallen leaves in the field in autumn may be an effective way to prevent occurrence of the disease the following year.
Cayaponia tibiricae: New Host of Zucchini Yellow Mosaic Virus in Brazil
Authors: Yuki V. A. , Rezende J. A. M. , Kitajima E. W. , Barroso P. A. V. , Kuniyuki H. , Groppo G. A. , Pavan M. A.
Published: May 2007

Cayaponia tibiricae Cogn. (CT) is a wild Cucurbitaceae species found in secondary forests in the State of São Paulo, Brazil. The species has indefinite growth and bears oblong dark green fruits, 15 to 20 mm long (1,2). CT plants showing yellow mosaic symptoms were found in Atibaia County. Extracts from symptomatic plants were rub inoculated to zucchini squash (Cucurbita pepo L.) and Chenopodium amaranticolor Coste & Reyn. Zucchini squash plants developed severe yellow mosaic with intense leaf malformation, while C. amaranticolor showed necrotic local lesions. Extracts from naturally infected CT, zucchini squash, and C. amaranticolor were tested by plate trapped antigen-enzyme-linked immunosorbent assay (PTA-ELISA) with antisera against papaya ringspot virus type W (PRSV-W), zucchini yellow mosaic virus (ZYMV), zucchini lethal chlorosis virus (ZLCV), watermelon mosaic virus 2 (WMV-2), and cucumber mosaic virus (CMV). All samples were positive in PTA-ELISA only with ZYMV antiserum. Also, in Western blot (immunoblot) assay, ZYMV antiserum labeled a protein of approximately 36 kDa. Electron microscopic examination of ultrathin sections from infected CT tissue revealed the presence of pinwheel inclusions typical of potyvirus (type 1) infection in the cytoplasm of the cell. CT seedlings were susceptible to mechanical inoculation with the ZYMV isolated from this species. This is the first report of CT as a natural host for ZYMV in Brazil.

References: (1) A. Cogniaux. Flora Brasiliensis 6:1, 1878. (2) M. Pio Corrêa. 1926. Diccionário das plantas úteis do Brasil e das exóticas cultivadas. Vol 1. Ministério da Agricultura, Rio de Janeiro, Brazil.
Effect of Soybean Growth Stage at the Time of Inoculation with Diaporthe phaseolorum var. meridionales on Stem Canker Development and Yield
Authors: Rupe J. C. , Sutton E. A. , Becton C. M. , Gbur E. E.
Published: May 2007

Infections at early stages of plant development followed by a long incubation period before symptoms appear during reproductive stages is characteristic of the disease cycle of stem canker of soybean, caused by Diaporthe phaseolorum var. meridionales. To determine the effect of plant growth stage at the time of infection on symptom development and yield components, soybean plants (cv. Walters) were grown in microplots and inoculated with a suspension of ascospores (106/ml) at the V1, V4, V6, V10, or R2 growth stage. Noninoculated plants served as controls. Development of foliar symptoms was quantified weekly after flowering (R2), and yields and seed weights were determined. The experiment was conducted twice, in 1992 and 1994. Foliar symptoms of stem canker developed for all treatments except the noninoculated control. Foliar symptoms appeared at the R2 to R5 growth stage and reached 90 to 100% incidence for most treatments. Disease development was delayed for the R2 inoculation, suggesting that a minimum incubation period of 34 to 41 days is necessary before foliar symptoms develop. Disease (area under the disease progress curve) was greater and yield, seed number, and seed weight were less in 1994 than in 1992. Quadratic equations significantly related these variables to time of inoculation and reached maximum or minimum values between 40.9 and 43.3 days after planting. This corresponded to the V6 growth stage. Yield and seed number were affected by disease development during pod formation (R2 to R5) in both years, while yield and seed weight were affected by disease development during seed formation (R5 to R6) in 1992.
First Confirmation of Phytophthora lateralis in Europe
Authors: Hansen E. M. , Streito Jean-Claude , Delatour Claude
Published: May 2007

Phytophthora lateralis, a pathogen of Chamaecyparis lawsoniana (Port-Orford cedar or Lawson's cypress), was confirmed in France, but isolates from Germany identified as P. lateralis or “similar to” P. lateralis proved to be P. gonapodyides. Previously, P. lateralis was known only from western North America, where it has been destructive in nurseries, ornamental plantings, and the forest since its introduction about 1920 (1). Reports from other locations have proved to be misidentifications or impossible to confirm. In France, P. lateralis was isolated and identified from C. lawsoniana on two occasions (1996 and 1998) in different parts of the country, probably stemming from a single original infestation of young, potted, greenhouse-propagated cedars in a commercial nursery. German isolates were from an old culture collection and from irrigation water in a nursery growing a wide range of woody ornamentals. Identifications were confirmed by comparison (2) with authentic isolates. P. lateralis isolates from France and Oregon formed laterally proliferating, elongated obpyriform sporangia that under the conditions of our tests could be dislodged by agitation, leaving a short pedicel. Also, brown chlamydospores formed laterally on the hyphae or terminally on a short stalk and oospores were not formed on standard media. Radial growth was about 2 mm per day. In contrast, sporangia of German isolates and known P. gonapodyides isolates were similar. They exhibited nested pro liferation, were broader than P. lateralis sporangia, and were not readily dehiscent. Some P. gonapodyides isolates, including those from Germany, formed chlamydospores, but these were nearly all catenulate and not lateral, and isolates grew faster (3 to 4 mm per day). Pathogenicity was tested by stem inoculation of C. lawsoniana. P. lateralis from France and Oregon produced lesions averaging 4.7 cm after 2 months (range 2.0 to 8.1 cm, six replicates per isolate, five isolates) while the six replicates of the two German isolates averaged 1.2- and 1.6-cm lesion lengths. Furthermore, sequences of internal transcribed spacer (ITS) DNA from French and Oregon P. lateralis isolates were identical, while sequences of German isolates were similar to P. gonapodyides (J. Duncan and D. Cooke, personal communiation). P. lateralis is a dangerous pathogen of C. lawsoniana and is also pathogenic to Taxus spp. (1), although less aggressive on this host. If established, it would be a serious threat to the widespread ornamental plantings and scattered forest plantations of C. lawsoniana in Europe.

References: (1) E. M. Hansen and K. J. Lewis. Compendium of Conifer Diseases. American Phytopathological Society, 1997. (2) C. M. Tucker and J. A. Milbrath. Mycologia 34:94, 1942.
Yellow Vine of Watermelon and Pumpkin in Tennesse
Authors: Bost S. C. , Mitchell F. L. , Melcher U. , Pair S. D. , Fletcher J. , Wayadande A. , Bruton B. D.
Published: May 2007

Yellow vine (YV) is a recently recognized decline of cucurbits expressed as plant yellowing, phloem discoloration, and death of vines as fruit approach maturity. In severely affected fields, YV incidence can range from 50 to 100% with similar yield loss. The disease has been associated with a phloem-limited, walled bacterium belonging to the gamma-3-proteobacteria (1), for which specific polymerase chain reaction (PCR) primers have been developed and used in diagnosis (2). First observed in 1988 in Oklahoma and Texas squash and pumpkin, YV was not detected in watermelon and cantaloupe until 1991. The disease has never been detected in cucumber. Efforts to date have been unsuccessful in transmitting the disease with dodder, grafting, or selected insects. Initially, the geographic range of the disease appeared to be generally confined to central and northeastern Oklahoma and north central Texas, an area known as the Cross Timbers Region. In 1997 to 1998, YV was diagnosed in commercial fields of watermelon and muskmelon from east Texas (Post Oak Savannah) and all cucurbit-growing areas of Oklahoma. In late summer 1998, symptoms similar to those of YV were observed in one watermelon (Hardeman County) and three pumpkin (Rhea and Morgan counties) fields in Tennessee where the leaves turned yellow and chlorotic and affected plants exhibited phloem discoloration. Estimated incidence of YV ranged from less than 1 to 20% of the plants in affected fields. PCR, with the YV-specific primers (2), amplified a band of the expected size (409 bp) from all watermelon and pumpkin plants exhibiting phloem discoloration. In contrast, no bands were amplified from asymptomatic (no phloem discoloration) watermelon or pumpkin. The nucleotide sequence of the DNA fragment amplified from a Tennessee watermelon and pumpkin plant was identical to that of the YV bacterium. The occurrence of YV outside of the Cross Timbers Region, and in a location as distant as Tennessee, suggests that the disease may be much more widespread than previously recognized. Diagnosis and monitoring of YV in all cucurbit-growing areas is critical for determining the geographic distribution and losses caused by this emerging disease.

References: (1) F. J. Avila et al. Phytopathology 88:428, 1998. (2) U. Melcher et al. (Abstr.) Phytopathology. 89(suppl.):S95, 1999.