bluuebunny/crossref_metadata_2025 huggingface dataset:
DNA Analysis Confirms Macroptilium lathyroides as Alternative Host of Bean golden yellow mosaic virus
Authors: Bracero V. , Rivera L. I. , Beaver J. S.
Published: May 2007

The leguminous weed Macroptilium lathyroides is considered a potential host of the Bean golden yellow mosaic virus (BGYMV; BGMV = Mesoamerican isolates). To determine if M. lathyroides could be a host for BGYMV, an infectivity cycle was established between this weed and Phaseolus vulgaris. Virus transmission was carried out using the whitefly, Bemisia argentifolli, as a vector. Inoculated plants of both species were examined for symptoms such as mosaic, stunting, and leaf distortion. P. vulgaris and M. lathyroides showed golden yellow mosaic symptoms during all infectivity cycle stages. Symptomatic plants of both species were tested for BGYMV using polymerase chain reaction (PCR) and nucleotide sequence analysis. Two degenerate primers sets were used for PCR to detect viral DNA: PAL1v1978/PAR1c715 and PCRc2/PBL12039. PCR analysis using primers PCRc2/PBL12039 amplified viral DNA for component B from both plant species. Nucleotide sequence analysis revealed a 93% identity between the virus isolated from M. lathyroides and the Puerto Rican isolate of BGYMV. These results confirmed that M. lathyroides could serve as an alternative host of BGYMV and that an infectivity cycle of BGYMV could possibly occur between P. vulgaris and M. lathyroides in Puerto Rico.
Evaluation of the Alter-Rater Model for Timing of Fungicide Applications for Control of Alternaria Brown Spot of Citrus
Authors: Bhatia Alka , Roberts P. D. , Timmer L. W.
Published: May 2007

Alternaria brown spot, caused by Alternaria alternata, results in serious yield losses of tangerines and their hybrids in Florida. The Alter-Rater model predicts the need for fungicide applications based on daily cumulative points that are assigned on the basis of rainfall, leaf wetness, and temperature. Previously, Alter-Rater threshold or trigger values of 50, 75, 100, and 150 points for application of copper fungicides were suggested for groves with different cultivars and disease histories. In this study, we evaluated thresholds of 50, 100, and 150 points in four Minneola tangelo and Murcott tangor groves in 2000 and 2001. For comparison, copper fungicides were applied according to the DISC Copper Model in 2000 and according to calendar sprays in 2001. Use of the Alter-Rater model resulted in fewer sprays in three of the four groves in 2000 and better fruit quality in the other grove than the Copper Model. Compared to a calendar spray schedule in 2001, use of the Alter-Rater model resulted in fewer sprays in two of the four groves but more sprays in one grove. The results confirmed that the Alter-Rater is a valuable tool for timing fungicide applications and that its use results in better disease control or fewer sprays.
Suitability of Southern Pines, Other Selected Crops, and Nutsedge to aLongidorussp. Associated with Stunting of Loblolly Pine Seedlings
Authors: Fraedrich S. W. , Cram M. M. , Handoo Z. A.
Published: May 2007

An undescribed needle nematode (Longidorus sp.) has been associated with severely stunted loblolly pine seedlings at a south Georgia nursery. Containers with selected crop and weed species were infested with 100 or 200 adults and juveniles of the Longidorus individuals to evaluate host suitability. Nematode populations increased in containers with slash, loblolly, and longleaf pine seedlings. The Longidorus sp. significantly reduced the dry root weights of slash (P = 0.008) and loblolly (P = 0.047) but not longleaf (P = 0.095) pine compared with controls. Populations of Longidorus decreased on nutsedge and small grains, including wheat, rye, oat, sorghum, and millet; and, in most experiments, populations decreased to levels found in fallow containers. Populations decreased on tomato and cabbage but increased slightly on red oak. The periodic removal of fields from pine production to grow cover crops consisting of small grains or to maintain fallow fields may be an important practice for management of this Longidorus sp.
First Report on Molecular Detection of Phytoplasmas in Papaya in Cuba
Authors: Arocha Y. , Horta D. , Peralta E. , Jones P.
Published: May 2007

Phytoplasmas and rickettsias have been associated with recent nonviral papaya diseases (1,2). Forty leaf samples with symptoms similar to papaya bunchy top (PBT) (1) and Australian papaya diseases (2) were collected from surveys done in Cuban papaya areas of Havana and Villa Clara provinces. Thirty nine plants showed typical PBT symptoms, while 35 plants also exhibited symptoms previously described for phytoplasma diseases (2) such as yellowing, crinkling, necrosis and deformation of older leaves, phyllody, virescence, short internodes, reduced latex flow, stunted crown leaves, and abscission of the fruit. Samples were evaluated by transmission electron microscopy, nested polymerase chain reaction (nPCR) with 16S ribosomal RNA phytoplasma primers SN910601/DH6-R16F2n/R16R2, PCR with rickettsial succinate dehydrogenase gene (sdhA) primers PBT1/PBT2, HaeIII, RsaI, and AluI enzyme restriction, and phytoplasma intergenic sequence analyses. Rickettsia PCR amplifications of 750 bp were obtained for samples with PBT symptoms, while the 35 phytoplasma-infected samples yielded amplifications of 1,250 bp. Restriction profiles and a 98% homology in the intergenic sequence (GenBank Accession No. AY257547) confirmed the presence of apple proliferation phytoplasma group. Electron microscopy analysis evidenced the presence of particles similar to rickettsia and phytoplasma pleomorfic bodies in more than 50% of samples analysed. Also, those similar to potyvirus and rhabdovirus were observed in 22.5%. To our knowledge, these results are the first report on the molecular detection of phytoplasmas in papaya in Cuba and suggest a possible concomitance among phytopathogens detected.

References: (1) M. Davis et al. Curr. Microbiol. 36:80, 1998. (2) K. Gibb et al. Plant Dis. 80:174, 1996.
First Report of Powdery Mildew of Greenhouse Pepper Caused by Leveillula taurica in British Columbia, Canada
Authors: Cerkauskas R. F. , Buonassisi A.
Published: May 2007

In 2003, powdery mildew of greenhouse pepper (Capsicum annuum L.) was reported simultaneously in two commercial greenhouses at two separate locations near Langley in southern British Columbia. Trace amounts of mildew on the foliage of cv. Zamboni in one operation, and 10 to 80% of the foliage of cv. Triple Four was affected in an organic operation, with losses in fruit yield of 2 to 4 kg/m2, were noted. The greenhouse pepper industry in British Columbia in 2001 comprised 76 ha with sales of $41.3 million (Canadian). Affected areas appeared as a white, powdery coating on the abaxial leaf surface of older foliage while diffuse chlorotic spots were present at corresponding locations on the adaxial surface. In some cases, pale yellow spots appeared on the adaxial portion of the affected foliage during later stages of disease development (2). Hyaline, single-celled pyriform and cylindrical conidia were present in 40:60 proportion, respectively. Both conidia had a network of crests and granules sometimes with tiny thorn-like projections on the surface. These projections were evident also on the lower half of conidiophores. Pyriform conidia ranged in length from 53.8 to 79.5 μm (mean = 68.0, SE = 0.8), and in width from 12.9 to 28.0 μm (mean = 20.1, SE = 0.6, n = 50) with a mean length to width ratio of 3.5. Cylindrical conidia had a length from 48.2 to 84.0 μm (mean = 66.0, SE = 0.9), and in width from 13.4 to 25.2 μm (mean = 18.6, SE = 0.4, n = 50) with a mean length to width ratio of 3.6. Short conidial chains borne on conidiophores consisted of a basal pyriform conidium followed by cylindrical conidium. No cleistothecia were observed. Stomatal penetration and extensive endophytic mycelial growth in the mesophyll layer were evident in foliar tissue cleared with glacial acetic acid/EtOH (1:2) and stained with lactophenol cotton blue. To confirm pathogenicity, a suspension of 2 × 104 conidia/ml from infected pepper leaves was applied onto the abaxial and adaxial leaf surfaces of 60-, 42-, and 28-day-old greenhouse pepper cv. Cubico, tomato cv. Trust, and cucumber cv. Corona, respectively. Plants were maintained in a growth chamber at 25/21°C day/night temperature and 80% relative humidity. Control plants in the same chamber were treated identically but not inoculated. After 21 days, inoculated pepper plants developed foliar powdery mildew symptoms on the abaxial surface, including sporulation similar to that of naturally infected plants. Occurrence of the fungus on the abaxial surface of pepper foliage, presence of endophytic mycelium, and the morphological characteristics of the imperfect state confirm the identity of the fungus (2). To our knowledge, this is the first report of Leveillula taurica (Lév.) G. Arnaud on pepper in British Columbia. The disease was first reported in Ontario, Canada in 1999 (1).

References: (1) R. Cerkauskas et al. Plant Dis. 83:781,1999. (2) J. Palti. Bot. Rev. 54:423, 1988.
Adaptation of Fire Blight Forecasting to Optimize the Use of Biological Controls
Authors: Johnson K. B. , Stockwell V. O. , Sawyer T. L.
Published: May 2007

We investigated adaptation of fire blight forecasting concepts to incorporate and optimize the use of biological agents for disease suppression. The effect of temperature on growth of the bacterial antagonists, Pseudomonas fluorescens A506 and Pantoea agglomerans C9-1S, and of the pathogen Erwinia amylovora153N, on pear and apple blossoms was evaluated in growth chamber and screenhouse experiments. New blossoms were inoculated with the strains and subsequent growth was measured over 96 h. Bacterial growth rates on blossoms were described as functions of temperature. A degree hour-based “bacterial growth index” (96-h moving total of degree hours >10°C) was created to assess conduciveness of orchard environments for antagonist colonization. A comparison of this index to a disease risk index indicated that biocon-trol treatments could be timed such that the antagonists could be expected to grow to an effective population size before the disease index shifted from “low” to “moderate” risk. For six pear- and apple-production areas of Oregon and Washington, regression of actual values of the bacterial growth and disease risk indices on index values derived from 4-day temperature forecasts resulted in coefficients of determination that averaged 0.75. The “bacterial growth index” and its estimation via temperature forecasts were incorporated into a decision matrix designed to guide optimal treatment timing.
Survival of Teliospores of Tilletia indica in Soil
Authors: Babadoost M. , Mathre D. E. , Johnston R. H. , Bonde M. R.
Published: May 2007

This study was conducted to assess survival of Tilletia indica teliospores in a location in the northern United States. Soils differing in texture and other characteristics were collected from four locations, equilibrated to -0.3 MPa, and infested with teliospores of T. indica to give a density of 103 teliospores per gram of dry soil. Samples (22 g) of the infested soil were placed in 20-μm mesh polyester bags, which were sealed and placed at 2-, 10-, and 25-cm depths in polyvinyl chloride tubes containing the same field soil as the infested bags. Tubes were buried vertically in the ground at Bozeman, MT, in October 1997. Soil samples were assayed for recovery and germination of T. indica teliospores 1 day and 8, 20, and 32 months after incorporation of teliospores into soil. The rates of teliospores recovered from soil samples were 90.2, 18.7, 16.1, and 13.3% after 1 day and 8, 20, and 32 months after incorporation of teliospores into soil, respectively, and was significantly (P < 0.01) affected by soil source. The percentage of teliospore recovery from soil was the greatest in loam soil and lowest from a silt loam soil. The rate of teliospores recovered from soil was not significantly affected by depth of burial and the soil source-depth interaction during the 32-month period. The percentage of germination of teliospores was significantly (P < 0.01) affected by soil source and depth of burial over the 32-month period. The mean percentage of teliospore germination at 1 day, and 8, 20, and 32 months after incorporation into soils was 51.3, 15.1, 16.4, and 16.5%, respectively. In another experiment, samples of silty clay loam soil with 5 × 103 teliospores of T. indica per gram of soil were stored at different temperatures in the laboratory. After 37 months of incubation at 22, 4, -5, and -18°C, the rates of teliospore recovered from soil were 1.6, 2.0, 5.7, and 11.3%, respectively. The percentage of spore germination from soil samples was highest at -5°C. Microscopy studies revealed that disintegration of teliospores begin after breakdown of the sheath-covering teliospore. The results of this study showed that teliospores of T. indica can survive in Montana for more than 32 months and remain viable.
First Report of Alternaria Leaf Blight of Aralia japonica Caused by Alternaria panax in Europe
Authors: Garibaldi A. , Gilardi G. , Gullino M. L.
Published: May 2007

Aralia japonica (synonym Fatsia japonica), belonging to the Araliaceae family, is a foliage plant highly valued in Italy for landscape and interior decoration. In the fall of 2002, a leaf blight disease was observed on plants grown in pots that were maintained under shade at a density of 15 to 20 pots per m2 at a nursery located in central Italy (Teramo Province). Typical symptoms were tan-to-dark brown leaf spots and rapid blighting of foliage under moist conditions. Chlorotic zones around necrotic lesions were common, and considerable leaf drop was associated with the disease. Affected plants were rarely killed, but the presence of lesions on mature plants reduced aesthetic quality and market value. The disease occurred on 70% of the plants. A fungus identified morphologically as Alternaria panax (2) was consistently isolated from infected leaves on potato dextrose agar (PDA). The fungus grows slowly and sparsely on PDA and produces a light brown mycelium, a characteristic red diffusible pigment in the agar medium, and rare conidia under 12-hr photoperiods. Measurements were carried out on conidia formed from single-spore isolates grown on autoclavated host tissue on water agar (LWA) at 24°C for 10 days. In LWA culture, conidia were borne singly or in chains of two to four conidia. Conidia produced in culture were smaller than those formed on the host and were highly variable in shape. They appeared obclavate, ellipsoidal, and obpyriform and pale to dark brown with relatively short or false beaks. Conidial bodies were 14.4 to 48.0 μm long (average 30.5 μm) and 7.2 to 12.0 μm wide (average 9.9 μm) with 3 to 10 transverse and a few longitudinal septa. Length of appendages was 9.6 to 26.0 μm (average 16.0 μm). Pathogenicity tests were performed by inoculating leaves of healthy Aralia japonica and Schefflera actinophylla plants by placing mycelial disks (5 mm in diameter) directly on wounded leaf tissues. Uninoculated, wounded plants served as controls. Four plants of each species were used. Plants were covered for 72 h with plastic bags and maintained in a growth chamber at 20°C (12 hours per day of fluorescent light). Control plants were maintained similarly. The first lesions developed on leaves of inoculated plants of both species after 7 days. A. panax was consistently reisolated from the lesions. The pathogenicity test was carried out twice. The presence of A. panax on Aralia japonica has been reported in Japan, Korea (2), and the United States (1) but to our knowledge, this is the first report of A. panax on Aralia japonica in Europe.

References: (1) S. Alfieri et al. Index of plant diseases in Florida. Bull. 11:52, Florida Department of Agriculture and Consumer Services, 1984 (2) S. H. Yu et al. Ann. Phytopathol. Soc. Jpn. 50:313, 1984.
First Record of Barley yellow striate mosaic virus Affecting Wheat Summer-Nurseries in Syria
Authors: Makkouk Khaled M. , Kumari Safaa G. , Ghulam Widad , Attar Nouran
Published: May 2007

A limited survey to identify virus diseases affecting wheat in summer nurseries in agricultural stations in southern Syria was conducted during October 2002. A total of 94 bread and durum wheat samples with symptoms suggestive of virus infection (stripping, stunting, and yellowing) were collected. All samples were tested for the presence of four viruses by tissue-blot immunoassay (2) at the Virology Laboratory of ICARDA, Aleppo, Syria using the following polyclonal antibodies: Barley stripe mosaic virus (BSMV); Barley yellow dwarf virus-PAV (BYDV-PAV) and Wheat streak mosaic virus (WSMV) from the Virology Laboratory at ICARDA; and Barley yellow striate mosaic virus (BYSMV) isolated from Italy (BYSMV-Italy) and provided by M. Conti, Instituto di Fitovirologia applicata, Turino, Italy. Serological results obtained indicated that BYSMV was the most commonly encountered virus (78.7%) followed by BYDV-PAV (22.3%), whereas, BSMV and WSMV were not detected in any of the samples tested. In sodium dodecyl sulfate-polyacrylamide gel electrophoresis, followed by western blots, purified BYSMV preparations were observed to contain a 47-kDa structural protein typical of the N protein of Rhabdoviruses that reacted strongly with three BYSMV antisera (BYSMV-Italy, BYSMV-Lebanon [4], and BYSMV-Morocco [1]). Samples that reacted with BYSMV antisera were transmitted from wheat to wheat, barley, and oat plants by the planthopper Laodelphax striatella (Fallen) (Hemiptera: family Delphacidae) in a persistent manner, and the major symptoms of BYSMV on cereal crops were stripping and stunting. BYDV-PAV has been reported from Syria earlier (3) but to our knowledge, this is the first report of BYSMV affecting wheat in Syria.

References: (1) B. E. Lockhart et al. Plant Dis. 70:1113, 1986. (2) K. M. Makkouk and A. Comeau. Eur. J. Plant Pathol. 100:71, 1994. (3) K. M. Makkouk et al. Phytopathol. Mediterr. 28:164, 1989. (4) K. M. Makkouk et al. Plant Dis. 85:446, 2001.
First Report of Fusarium oxysporum Causing Vascular Wilt of Lamb's Lettuce (Valerianella olitoria) in Italy
Authors: Garibaldi A. , Gilardi G. , Gullino M. L.
Published: May 2007

Lamb's lettuce (Valerianella olitoria), also known as corn salad, is increasingly grown in Italy and used primarily in the preparation of mixed processed salad. In the summer of 2003, plants of lamb's lettuce cvs. Trophy and Palmares exhibiting wilt symptoms were observed in several commercial greenhouses near Bergamo in northern Italy. Wilted 30-day-old plants were observed first during the month of June, at the time of thinning when temperatures ranged between 28 and 35°C. Disease was generally uniform in the greenhouses and 30 to 50% of the plants were affected. Vascular tissue of affected seedlings appeared red or brown but later turned brown or black. Affected plants were stunted and developed yellowed leaves. Vascular discoloration was continuous from the upper taproot through the crown to the leaf. Fusarium oxysporum was consistently isolated from symptomatic vascular tissue onto a Fusarium-selective medium (1). Seeds of the same cultivars (Trophy and Palmares) affected by the wilt in the field were artificially inoculated by dipping them for 15 min into spore suspensions (1 × 106 conidia per ml) of three isolates of F. oxysporum obtained from infected plants. Noninoculated seeds served as control treatments. Forty seeds per treatment were sown in pots (1-liter volume) containing steam-sterilized soil and maintained at 25°C in a growth chamber programmed for 12 hours of light per day. Wilt symptoms developed on both cultivars 20 days after seeding, and F. oxysporum was consistently reisolated from infected plants. The plants obtained from noninoculated seeds remained healthy. The pathogenicity test was carried out twice with similar results. To our knowledge, this is the first report of F. oxysporum causing vascular wilt of lamb's lettuce and may warrant a new forma specialis designation.

Reference: (1) H. Komada. Rev. Plant Prot. Res. 8:114, 1975.
First Report of Onion Rust Caused by Puccinia allii on Allium pskemense and A. altaicum
Authors: Lupien S. L. , Hellier B. C. , Dugan F. M.
Published: May 2007

In June 2003, uredinial and telial pustules were seen on leaves of accession W6-12755 Allium pskemense B. Fedtsch. originating from Uzbekistan and grown for germplasm increase in Pullman, WA. W6-18947 A. altaicum Pall., originating from Mongolia, displayed similar symptoms in the same garden in June 2000. A. altaicum is a wild onion exploited for food in its native range and is ancestral to A. fistulosum L., bunching onion (2). A. pskemense is a wild perennial sometimes propagated under cultivation (2). Both species have been exploited for research in breeding and systematics of Allium and used to a lesser degree in screening for pest or disease resistance. Clustered, golden orange, amphigenous uredinia were approximately 1 × 0.5 mm and surrounded by stromatic, subepidermal, blackish telia of variable size. Urediniospores (thick-walled, pale orange, echinulate, (25-) 27 to 32 (-34) × (19-) 21 to 25 μm, with as many as 10 scattered, indistinct pores), teliospores (two-celled, smooth, golden brown, 42 to 65 × 18 to 26 μm), and mesospores (27 to 42 × 15 to 21 μm, and approximately 30% as frequent as teliospores) all approximated the description for P. allii Rudolphi (4), but were more strongly congruent with the description of Puccinia blasdalei Diet. & Holw. (1), now considered a synonym (4). Specimens are deposited with WSP, Washington State University, Pullman. P. allii or its synonyms have been recorded from over 30 species of Allium (1,3,4), but to our knowledge, this is the first report of this rust on A. pskemense or A. altaicum.

References: (1) J. C. Arthur. Manual of the Rusts in United States and Canada, Hafner Publishing, N.Y., 1962. (2) J. L. Brewster. Onions and Other Vegetable Alliums. CABI, Wallingford, Oxon, U.K, 1994. (3) D. F. Farr et al. Fungal Databases, Systematic Botany and Mycology Laboratory, On-line publication. ARS, USDA, 2003. (4) G. F. Laundon and J. M. Waterston. Puccinia allii. No. 52 in: Descriptions of Pathogenic Fungi and Bacteria. CMI, Kew, Surrey, U.K., 1965.
Genes for Adult-Plant Resistance to Leaf Rust in Soft Red Winter Wheat
Authors: Wamishe Yeshi A. , Milus Eugene A.
Published: May 2007

Host plant resistance in wheat (Triticum aestivum) has been the principal means of managing leaf rust caused by Puccinia triticina. The need for durable resistance has changed the focus from the use of seedling resistance to adult-plant resistance. The objectives of this study were to determine the genetic basis for adult-plant resistance and to determine the most effective method to identify adult-plant resistance genes Lr12, 13, and 34 among 116 contemporary soft red winter wheat cultivars and breeding lines. Adult-plant resistance was detected by inoculating flag leaves with a race that was virulent on seedlings. Approximately 90% of the lines expressed resistance under controlled conditions. It was postulated that the adult-plant resistance in 67 lines was due in part to either Lr12, 13, or 34; the adult-plant resistance detected in 17 lines was attributed to Lr12 based on a distinctive low infection type very similar to that on the isoline TcLr12; the adult-plant resistance in 27 lines was attributed to Lr34, as all of these lines expressed a “leaf tip necrosis” in the field (a phenotype controlled by a gene known to be tightly linked with Lr34); and the adult-plant resistance in 23 lines was attributed to Lr13 based on a high infection type at 18.1°C and low infection type at 25.5°C with one or more pathogen isolates that were virulent on Lr13 at 18.1°C and avirulent on Lr13 at 25.5°C. The adult-plant resistance detected in the remaining 40% of the lines was due to one or more unidentified genes for adult-plant resistance. In a 4-year field study at several locations, nearly 29% of the lines were resistant at all locations, no line was susceptible at all locations, and only 30% of the lines were susceptible at one or more locations. Given that many of the lines in this study were resistant to all known races of P. triticina before being released as cultivars, the high frequency of adult-plant resistance in this study demonstrates that adult-plant resistance can be incorporated even in the presence of highly effective seedling resistance.
Hydrangea macrophylla Flower Spot Caused by Botrytis cinerea in Buenos Aires
Authors: Rivera M. C. , Morisigue D. E. , Lopez S. E.
Published: May 2007

During the spring of 2003, flower spots were observed on French hydrangea (Hydrangea macrophylla (Thunb.) DC) in CETEFFHO-INTA-JICA experimental greenhouses in Castelar, Argentina. Brown, irregular spots randomly distributed on petals were detected on an old, whiteflowering variety of unknown origin, cultivated by growers. Small pieces of diseased tissue were surface disinfested with 2% NaOCl, plated on 2% potato dextrose agar (PDA) with pH 7, and incubated at 22 to 24°C. Dense, whitish mycelium developed within 48 h and turned gray after 72 h. Conidia were ellipsoid, hyaline, nonseptate, and formed in botryose heads. Spores from 10-day-old colonies that were developed on PDA in test tubes were removed with 4 ml of sterile water per tube. Prior to inoculation, inflorescences were detached and placed in water-filled glass vases. To test pathogenicity, eight healthy inflorescences were sprayed with a 5-ml suspension (2 × 104 conidia per ml of sterile distilled water). Another eight healthy inflorescences were sprayed with sterile distilled water. The inflorescences were maintained at 21°C and covered with polyethylene bags that were removed after 3 days. Brown, circular-to-irregular spots appeared on petals 5 days after inoculation, became coalescent, and covered 50 to 60% of each inflorescence in 8 days. Gray mold consisting of black conidiophores and gray-in-mass conidia was observed 3 days after the development of the symptoms. Controls remained symptomless. The same pathogen was recovered from inoculated flowers and was identified as Botrytis cinerea Pers.:Fr. (1). To our knowledge, this is the first report of this fungus on Hydrangea macrophylla in Argentina.

Reference: (1) M. V. Ellis and J. M. Waller. Sclerotinia fuckeliana (condial state: Botrytis cinerea).No. 431 in: Descriptions of Pathogenic Fungi and Bacteria, CMI, Kew, Surrey, UK, 1974.
Detection and Characterization of a New Strain of Citrus Canker Bacteria from Key/Mexican Lime and Alemow in South Florida
Authors: Sun Xiaoan , Stall Robert E. , Jones Jeffrey B. , Cubero Jaime , Gottwald Tim R. , Graham James H. , Dixon Wayne N. , Schubert Tim S. , Chaloux Paul H. , Stromberg Verlyn K. , Lacy George H. , Sutton Bruce D.
Published: May 2007

In the Wellington and Lake Worth areas of Palm Beach County, FL, citrus canker appeared on Key/Mexican lime (Citrus aurantiifolia) and alemow (C. macrophylla) trees over a period of about 6 to 7 years before detection, but nearby canker-susceptible citrus, such as grapefruit (C. × paradisi) and sweet orange (C. sinensis), were unaffected. Colonies of the causal bacterium, isolated from leaf, stem, and fruit lesions, appeared similar to the Asiatic group of strains of Xanthomonas axonopodis pv. citri (Xac-A) on the nutrient agar plate, but the growth on lima bean agar slants was less mucoid. The bacterium produced erumpent, pustule-like lesions of typical Asiatic citrus canker syndrome after inoculation into Key/Mexican lime, but brownish, flat, and necrotic lesions on the leaves of Duncan grapefruit, Madame Vinous sweet orange, sour orange (C. aurantium), citron (C. medica), Orlando tangelo (C. reticulata × C. × paradisi), and trifoliate orange (Poncirus trifoliata). The bacterium did not react with the Xac-A specific monoclonal antibody A1 using enzyme-linked immunosorbent assay (ELISA) and could not be detected by polymerase chain reaction (PCR)-based assays using primers selected for Xac-A. DNA reassociation analysis confirmed that the pathogen, designated as Xac-AW, was more closely related to Xac-A and Xac-A* strains than X. axonopodis pv. aurantifolii or the citrus bacterial spot pathogen (X. axonopodis pv. citrumelo). The strain can be easily differentiated from Xac-A and Xac-A* using ELISA, PCR-based tests, fatty acid analysis, pulsed-field gel electrophoresis of genomic DNA, and host specificity.
Development of PCR-Based Assays for Detecting Xanthomonas campestris pv. carotae, the Carrot Bacterial Leaf Blight Pathogen, from Different Substrates
Authors: Meng X. Q. , Umesh K. C. , Davis R. M. , Gilbertson R. L.
Published: May 2007

Detection of the carrot bacterial leaf blight pathogen, Xanthomonas campestris pv. carotae, was achieved using polymerase chain reaction (PCR) along with primer pairs developed from sequences of cloned random amplified polymorphic DNA (RAPD) fragments. Primer pairs 3S and 9B directed the amplification of ∼350-bp and ∼900-bp (or ∼2 kb) DNA fragments, respectively, from genomic DNA of all known X. campestris pv. carotae strains tested, but not from that of 13 other X. campestris pathovars or other bacterial species, including yellow non-xanthomonad bacteria isolated from carrot tissues and seeds. In tests conducted with an extensive collection of X. campestris pv. carotae-like strains isolated from different substrates from California, Idaho, Oregon, Washington, and Canada, the 3S primer pair directed the amplification of the ∼350-bp target fragment from all strains. These results indicated that the 3S primer pair is highly specific for X. campestris pv. carotae detection. Using the 3S primer pair, PCR assays were developed for detection of X. campestris pv. carotae from colonies on agar media, carrot leaf and stem tissues, and seeds. These tests could be performed in a single day. The PCR-based seed assay detected X. campestris pv. carotae from lots with contamination rates ranging from 2 × 102 to 2.3 × 108 CFU per gram of seed. This assay gave results similar to a seed-wash dilution plating assay and proved more sensitive than an enzyme-linked immunosorbent assay (ELISA)-based assay.
Proactive Control of Petri Disease of Grapevine Through Treatment of Propagation Material
Authors: Fourie Paul H. , Halleen Francois
Published: May 2007

Petri disease is a vascular disease associated with decline and dieback of young grapevines. A major means of spread of the causal organisms, Phaeomoniella chlamydospora and Phaeoacremonium spp., is via infected propagation material. Since no curative control measures are known, proactive measures must be taken in grapevine nurseries to manage this disease. To study this aspect, semicommercial trials with naturally infected rootstock material were performed in grapevine nurseries in South Africa. Prior to grafting, rootstocks were treated as follows: 1-h drench in suspensions of benomyl, phosphoric acid, different bacterial and Trichoderma formulations, water, or hot water treated (HWT; 30 min at 50°C). Grafted cuttings were planted and grown in a greenhouse and two commercial field nurseries and uprooted 8 months later. In instances where rootstocks were treated with benomyl or Trichoderma formulations, the incidences of Phaeomoniella and Phaeoacremonium in grafted cuttings and uprooted nursery vines were significantly lower than that of the water treatment. However, the reduction was most consistent and noteworthy in vines on rootstocks that received HWT prior to grafting. HWT of dormant nursery vines effected a similar reduction in Phaeomoniella and Phaeoacremonium incidence. Root-stock drenches in benomyl and/or Trichoderma formulations could thus be integrated with HWT for the proactive management of Petri disease in grapevine nurseries.
Effect of Pathogen Aggressiveness and Vinclozolin on Efficacy of Rhodotorula glutinis PM4 Against Botrytis cinerea on Geranium Leaf Disks and Seedlings
Authors: Buck J. W. , Jeffers S. N.
Published: May 2007

Efficacy of the yeast Rhodotorula glutinis isolate PM4 as a biological control agent against 29 isolates of Botrytis cinerea obtained from greenhouse-grown ornamentals was assessed in vitro on geranium leaf disks. Isolates of B. cinerea varied in aggressiveness in the absence of either biological or chemical controls; diameters of lesions produced on leaf disks ranged from 0.8 to 12.3 mm. Efficacy of R. glutinis PM4 against the different isolates of B. cinerea varied greatly; lesion diameters ranged from 0.2 to 10.3 mm when the yeast was present. The yeast significantly reduced lesion development by 16 B. cinerea isolates in each of two replicate trials and by 9 isolates in one of the trials; however, 3 isolates were not inhibited by the yeast on geranium leaf disks. The yeast significantly reduced lesion development by B. cinerea isolate 01, used as a standard for comparison, in four of six trials. Fourteen of the B. cinerea isolates were inoculated onto geranium seedlings and produced a range of lesion sizes (2.9 to 16.4 mm), similar to that produced on leaf disks. Efficacy of the yeast in combination with a reduced rate (0.1×) of the fungicide vinclozolin (50 μg of active ingredient ml-1) was evaluated on geranium seedlings against 10 isolates of B. cinerea that were resistant to vinclozolin. Addition of vinclozolin to the yeast significantly reduced lesion diameter by five of the isolates compared with diameters of lesions produced in the presence of the yeast alone. Lesions produced by nine of the resistant isolates were 2.6 mm or smaller in both trials on plants treated with the mixture of yeast and vinclozolin. The effect of vinclozolin concentration (0 to 500 μg a.i. ml-1) on biocontrol efficacy of R. glutinis PM4 was evaluated using three resistant isolates of B. cinerea and geranium seedlings. Disease control was significantly better at higher concentrations of fungicide for two of the isolates. Linear regression of lesion diameter against vinclozolin concentration showed a significant effect on yeast biocontrol efficacy with B. cinerea isolate FL-2-b (y = 6.20 – 0.63x; r2= 0.74) and isolate BR-1 (y = 4.10 – 0.32x; r2 =0.28) but there was no significant effect with isolate GG-2-b. Overall, PM4 exhibited biocontrol activity on both geranium leaf disks and seedlings against a number of isolates of B. cinerea that varied in aggressiveness. Variability in biocontrol efficacy against isolates resistant to vinclozolin usually was reduced by the addition of vinclozolin.
Genetic Diversity of Sclerotinia homoeocarpa Isolates from Turfgrasses from Various Regions in North America
Authors: Viji G. , Uddin W. , O'Neill N. R. , Mischke S. , Saunders J. A.
Published: May 2007

Sixty-seven isolates of Sclerotinia homoeocarpa, causing dollar spot disease in creeping bentgrass, annual bluegrass, Bermudagrass, and perennial ryegrass turf, collected from 23 golf courses in various geographical regions of the United States and Canada between 1972 and 2001, were characterized by vegetative compatibility, genetic diversity, and pathogenicity. Eleven vegetative compatibility groups (VCGs A to K) were identified among the isolates tested in this study, and five of them (VCGs G to K) were new. VCG B was the most predominant group, typifying 33 isolates (51%) tested. S. homoeocarpa isolates collected from golf courses in Pennsylvania belonged to seven VCGs (A, B, E, F, G, I, and K), whereas three groups were observed in those collected from New York (B, E, and G) and New Jersey (E, H, and I). Two isolates, one each from Pennsylvania and Canada, were incompatible when paired with the tester isolates in all possible combinations, and did not fall into any known VCG. An isolate collected from Canada was compatible with tester isolates from two VCGs (C and D). Genetic analyses using amplified fragment length polymorphism (AFLP) showed the presence of two genetically distinct groups, designated as major group and the minor group. The major group included 36 isolates collected from various golf courses in the United States and Canada. Two isolates collected from bermudagrass in Florida formed a separate cluster, the minor group. Isolates that belonged to the major group were further divided into two subgroups (1 and 2). Subgroup 1 consisted of all the isolates that belonged to VCGs A, E, G, H, and I. Three of the four isolates that belonged to VCG K also were clustered with isolates of subgroup 1. Subgroup 2 consisted of all the isolates from VCG B, and one each from VCGs F and K. Pathogenicity assays on Penncross creeping bentgrass showed significant differences (P = 0.05) in virulence among the isolates. Overall, a relationship between virulence and VCGs was observed, in which certain virulence groups corresponded to specific VCGs; however, such a relationship was not observed between virulence and AFLPs. Close similarity among isolates of S. homoeocarpa collected from different locations in the United States and Canada suggests that isolates of the same genotype could be involved in outbreaks of dollar spot epidemics at multiple locations.
First Report of Powdery Mildew of Cashew Caused by Oidium anacardii in South Africa
Authors: Swart W. J.
Published: May 2007

The cashew plant (Anacardium occidentale L.) (family Anacardiaceae) is native to Brazil. It was introduced in East Africa by the Portuguese in the 16th century where it is now widely cultivated, especially in Tanzania, Kenya, and Mozambique. The processed kernels are the most important product derived from the plant, although in Brazil and India, juices, jam, and alcoholic and soft drinks are also made from the pear-shaped edible receptacle. The plant is currently being evaluated in South Africa for commercial production. During May 2002, at least 25% of 5-year-old cashew trees grown from seed in the northern KwaZulu-Natal Province of South Africa were infected with powdery mildew. Signs included extensive growth of white, superficial mycelium bearing upright conidiophores on young shoots with tender leaves, inflorescences, and young receptacles. In severely affected trees, approximately 35% of young shoots and 45% of young receptacles displayed signs of powdery mildew. Severely infected young leaves were brown and deformed in contrast to older leaves that were unaffected. Microscopic examination of diseased tissue revealed hyaline, cylindrical-to-slightly doliform, single-celled conidia (10 to 17.5 × 2.5 to 5 μm) borne in chains. The pathogen was subsequently identified as Oidium anacardii Noack on the basis of morphology (1). No other species of powdery mildew fungi have been reported on cashew. A pathogenicity test was conducted by gently pressing a heavily diseased leaf onto two healthy leaves of each of 10 cashew plants maintained in pots on open benches in the glasshouse at 22 to 25°C and mean relative humidity of 65%. Control treatments entailed pressing an asymptomatic leaf onto each of two healthy leaves per plant. The experiment was conducted three times. After 14 days, at least one powdery mildew colony had developed on 80% of inoculated leaves but were absent from all replications of the control treatment. The source of inoculum for this reported outbreak is unknown, although O. anacardii is known to occur in southern Mozambique less than 100 km from the infected site. Cashew powdery mildew was first officially reported in Tanzania in 1979 where significant crop losses, partially attributable to the pathogen, have been recorded since (3). No significant damage to production has been recorded in Brazil (2). To our knowledge, this is the first report of O. anacardii occurring on cashew in South Africa.

References: (1) E. Castellani and F. Casulli. Rivista di Agricoltura Subtropicale e Tropicale 75:211, 1981. (2) F. C. O. Freire et al. Crop Prot. 21:489, 2002. (3) P. J. Martin et al. Crop Prot. 16:5, 1996.
First Report of Phaeomoniella chlamydospora on Vitis vinifera and French American Hybrids in Chile
Authors: Auger J. , Esterio M. , Pérez I. , Gubler W. D. , Eskalen A.
Published: May 2007

Phaeomoniella chlamydospora (W. Gams, Crous. M.J. Wingfield & L. Mugnai) Crous & Gams (= Phaeoacremonium chlamydosporum) was isolated during the growing seasons of 2003-2004 from roots, trunks, and cordons of grapevines, including cvs. Cabernet Sauvignon, Merlot, Pinot noir, Thompson seedless, Ruby seedless and root stock 3309C, and Kober 5BB, from 10 locations in V, VI, VII, and metropolitan regions of Chile. P. chlamydospora was isolated from 82% of samples from vines 2 to 18 years old that showed decline symptoms in the field. Isolates were identified on the basis of a previous description (1) and internal transcribed spacer (ITS1-5.8S-ITS2) rDNA sequences identical to those of P. chlamydospora isolated from Vitis vinifera (culture CBS 22995, GenBank Accession No. AF 197973). P. chlamydospora is established as a member of the petri and esca disease complex and as a pathogen of grapevines (2,3). Pathogenicity tests were completed by injecting into the pith of 50 single-node, rooted cuttings of Pinot noir and 3309C, approximately 20 μl of a 106 conidia per ml suspension, obtained from four isolates from Chile and one from California. Ten control cuttings of Pinot noir and 3309C were injected with an equal volume of sterile distilled water. Twenty-four weeks after inoculations, all P. chlamydospora-inoculated cuttings exhibited dark streaking of the vascular tissue extending 40 to 45 mm from the point of inoculation. The vascular streaking observed in inoculated plants was identical to symptoms observed in declining vines in the vineyard. No symptoms were observed in the controls. P. chlamydospora was isolated from the region of vascular streaking in 85% of inoculated cuttings. P. chlamydospora was not isolated from the water-treated controls. The reisolated P. chlamydospora was verified with means of morphological characters and polymerase chain reaction amplification with the species-specific primers (3). P. chlamydospora is widespread and readily isolated from declining grapevines in Chile and other grape growing regions of the world. To our knowledge, this is the first report of P. chlamydospora from the cultivars cited above in Chile.

References: (1) M. Groenewald et al. Mycol. Res. 105:651, 2001. (2) L. sparapano et al. Phytopathol. Mediterr. (Suppl.)40:376, 2001. (3) S. Tegli et al. Phytopathol. Mediterr. 39:134, 2000.
First Report of Soybean Cyst Nematode (Heterodera glycines) on Soybean in North Dakota
Authors: Bradley C. A. , Biller C. R. , Nelson B. D.
Published: May 2007

During August 2003, soybean (Glycine max) plants from Richland County, North Dakota with white-to-yellow, lemon-shaped structures on the roots were brought to the North Dakota State University Plant Diagnostic Laboratory. To confirm that the structures were females of a cyst nematode, they were crushed and observed microscopically to determine if nematode eggs and second-stage juveniles were present. Morphology of the second-stage juveniles was consistent with Heterodera glycines, the soybean cyst nematode (SCN). A survey was conducted in soybean fields in 34 km2 around the field in which the samples originated. Ten of twenty fields surveyed had visible females on the roots of plants. Symptoms observed in those fields included patches of stunted, chlorotic, and dead plants. Soil samples were collected from selected areas within eight fields, eggs were extracted using standard soil sieving techniques, and egg numbers were determined. Egg numbers ranged from 550 to 20,000 eggs per 100 cm3 of soil. SCN collected from two different fields, designated as Dwight and LaMars, were used to determine their HG Type. Standardized procedures (1) were used in a growth chamber set at 27°C with 16-h days. Pots in the test were organized in a completely randomized design with three replicates; the test was repeated over time. After 30 days, females were extracted from roots and counted, and a female index (FI) was calculated for each indicator line (1). The mean number of females on susceptible standard cv. Lee 74, was 110. The Dwight SCN population had an FI of 5.3 on plant introduction (PI) 88788, 1.5 on PI 209332, 5.8 on PI 548316 (Cloud), and 0 on all other indicator lines. The LaMars population had an FI of 1.0 on PI 88788, 3.1 on PI 548316 (Cloud), and 0 on all other indicator lines. These results indicate that both SCN populations tested are HG Type 0. To our knowledge, this is the first report of SCN on soybean in North Dakota. Because other hosts of SCN, as well as soybean, are economically important in North Dakota, such as dry edible bean (Phaseolus vulgaris) and dry pea (Pisum sativum), this disease could adversely impact several commodities throughout the state.

Reference: (1) T. L. Niblack et al. J. Nematol. 34:279, 2002.
Causal Agent of Red Stripe Disease of Rice
Authors: Elazegui F. A. , Castilla N. P. , Dalisay T. U. , Mew T. W.
Published: May 2007

A variety of methods that included natural and synthetic media for isolating bacteria and fungi were used to isolate the causal agent of the red stripe disease of rice. A fungus was isolated consistently from leaves with red stripe symptoms using the blotter method. In this method, surface-sterilized leaves were placed on sterile petri plates, lined with moistened filter paper, and the plates were incubated for 14 days at 28 to 30°C. The fungal isolate was reisolated from the lesions of inoculated plants and reinoculated on test plants that became symptomatic, thus fulfilling Koch's postulates. Based on the morphological characteristics of the fungus, the causal agent of red stripe was identified as a species of Gonatophragmium. Colonies of the latter are slow-growing, reaching an average of 29.0 ± 0.9 mm in diameter after incubation on potato dextrose agar (PDA) for 18 days at 28 to 30°C in the dark. It can be overgrown easily by saprophytes when infected leaves are incubated using the blotter method without sterilization. Yellow-orange pigmentation was observed on PDA with mycelial growth and on filter paper with infected leaves, a unique characteristic which facilitates the isolation of the fungus. Studies are in progress using traditional and molecular techniques to identify the pathogen to the species level.