bluuebunny/crossref_metadata_2025 huggingface dataset:
Cucumber Mosaic Virus, Tobacco Streak Virus, and Cucumber Mosaic Virus Satellite RNA Associated with Mosaic and Ringspot Symptoms in Ajuga reptans in Ohio
Authors: Fisher J. R. , Nameth S. T.
Published: May 2007

Creeping bugleweed (Ajuga reptans L.) is a perennial ornamental commonly grown as a ground cover in temperate climates. Commercial samples of the A. reptans cultivars Royalty, var. Atropurpurea Bronze, Bronze Beauty, and Burgundy Glow showing mosaic and ringspot symptoms were tested for the presence of virus infection by direct antibody sandwich enzyme-linked immunosorbent assay (ELISA) and viral-associated double-stranded (ds) RNA analysis. Cucumber mosaic cucumovirus (CMV) was detected by ELISA and dsRNA analysis in symptomatic samples of all cultivars tested. ELISA values were considered positive if the absorbance values were twice the negative control. Negative control values were established with asymptomatic tissue of the cv. Bronze Beauty. Tobacco streak ilarvirus (TSV) was detected only by ELISA in symptomatic samples of all cultivars except Royalty. No dsRNA suggestive of TSV was detected. Alfalfa mosaic virus (AMV) was detected by ELISA and dsRNA analysis in symptomatic samples of all cultivars tested except Royalty and var. Atropurpurea Bronze. dsRNA analysis also indicated the presence of a low molecular weight, possible satellite (sat) RNA associated with all symptomatic and asymptomatic Royalty and var. Atropurpurea Bronze plants tested. Northern (RNA) blot analysis with a digoxigenin-labeled full-length clone of the (S) CARNA-5 (-) CMV satRNA (ATCC no. 45124) confirmed that the low molecular weight RNA associated with the Royalty and var. Atropurpurea Bronze cultivars was indeed CMV satRNA. Only AMV has been previously reported in A. reptans in the United States (1). This is the first report of CMV and its satRNA, as well as TSV, in A. reptans in the United States.

Reference: (1) W. T. Schroeder and R. Provvidenti. Plant Dis. Rep. 56:285, 1972.
Recent Outbreak of Stem Canker (Diaporthe phaseolorum var. meridionalis) of Soybean in Santa Fe, Argentina
Authors: Pioli R. , Gattuso S. , Prado D. , Borghi A.
Published: May 2007

This disease was first noted in the area in February 1993 (2), when a soybean (Glycine max (L.) Merr.) disease survey was conducted in several localities of southern Santa Fe province, the core soybean region of Argentina. At that time, its incidence ranged from 5 to 8% in isolated fields. However, in March 1997, stem canker reached a dramatic 70 to 100% incidence, probably helped by the extensive use of susceptible cultivars, favorable climatic conditions, and inoculum availability from no-till fields. Observed symptoms on stems consisted of V-shaped longitudinal lesions at petiole insertion, with reddish brown margins and discolored centers, where the pycnidia of the anamorph Phomopsis phaseoli (Desmaz.) Sacc. meridionalis Morgan-Jones were found. The lesions coalesced and consequently the main stem and branches died. Foliage symptoms started as yellow blotches, later developing into interveinal chlorosis and necrosis. Perithecia of the teleomorph Diaporthe phaseolorum (Cooke & Ellis) Sacc. var. meridionalis F. A. Fernandez (1) were obtained from infected stems in several crop seasons. Once ripe, the ascospores were cultured on potato dextrose agar (PDA) acidified with lactic acid (0.2%), amended with streptomycin (100 mg/liter), and maintained in darkness at 20 to 25°C. Yellowish white colonies were obtained, later becoming tan and developing perithecia. Perithecia had a beak length of 868 ± 183 μm, neck width of 126.2 ± 17 μm, the asci of 36.7 ± 4.7 μm length and bicellular biguttulate ascospores of 10.2 ± 1 μm length and 3 ± 0.13 μm width. All features match the available descriptions of the pathogen (1). Pathogenicity trials were performed on seedlings of resistant and susceptible cultivars up to second trifoliar leaf stage; these cultivars were classified according to inoculations and field behavior. Plants were wounded with a scalpel in the cotyledonary node and inoculated with a 3-mm-diameter PDA mycelial plug, covered with vaseline. Control seedlings were either not wounded or similarly wounded and covered with vaseline but no PDA plugs were applied. Symptom development was observed within 4 days from inoculation in the top leaf, and in 7 days most seedlings of susceptible cultivars were dead. Resistant cultivars survived and showed only reddish discoloration in wounds. The control seedlings were symptomless and the pathogen was not isolated from them. Conversely, inoculated seedlings with visible symptoms consistently yielded D. phaseolorum var. meridionalis from stem sections at different distances from the inoculation point.When cultured on water agar, alpha conidia from pycnidia and ascospores from the perithecia were obtained.

References: (1) F. A. Fernandez and R. T. Hanlin. Mycologia 88:425, 1996. (2) R. N. Pioli et al. Comun. Biol. 11:156, 1993.
Resistance of Transgenic Prunus domestica to Plum Pox Virus Infection
Authors: Ravelonandro M. , Scorza R. , Bachelier J. C. , Labonne G. , Levy L. , Damsteegt V. , Callahan A. M. , Dunez J.
Published: May 2007

Transgenic plum trees (Prunus domestica) containing the plum pox potyvirus coat protein (PPV-CP) gene were inoculated with PPV by aphid feeding or chip budding. Infection was monitored by evaluation of virus symptoms, DAS-ELISA, and immunoblot assays. Based on observations and analyses over 3 years including two dormancy cycles, one out of five transgenic clones (C-5), was found to be resistant to infection whether inoculated by aphids or by chip budding. PPV could not be detected in any inoculated plants of the C-5 clone by immunoblot or immunocap-ture-reverse transcriptase-polymerase chain reaction assays. To our knowledge, this is the first P. domestica clone resistant to PPV infection produced by genetic engineering.
Genetic Diversity Among Geminiviruses Associated with the Weed Species Sida spp., Macroptilium lathyroides, and Wissadula amplissima from Jamaica
Authors: Roye Marcia E. , McLaughlin Wayne A. , Nakhla Medhat K. , Maxwell Douglas P.
Published: May 2007

Genetic diversity among geminiviruses associated with three common weeds in Jamaica was studied using digoxigenin-labeled geminiviral DNA probes, polymerase chain reaction with degenerate primers for DNA-A and DNA-B, nucleic acid sequencing, and derived amino acid sequences. Geminiviruses with bipartite genomes were found in Sida spp., Macroptilium lathyroides, and Wissadula amplissima. The geminiviruses detected in Sida spp. and M. lathyroides were nearly identical and were both designated Sida golden mosaic geminivirus (SidGMV-JA), whereas the geminivirus in W. amplissima was sufficiently different to be designated Wissadula golden mosaic geminivirus (WGMV). Nucleotide sequence comparisons of the common regions and the N-terminal regions of the AC1 (rep) and AV1 ORFs, together with the derived amino acid sequence comparisons of the N-terminal parts of BC1 and BV1 ORFs were used to determine their similarities to other geminiviruses. SidGMV-JA was most similar to potato yellow mosaic geminivirus (PYMV). We propose that these two geminiviruses (SidGMV-JA and PYMV) define a new geminivirus cluster, the potato yellow mosaic virus (PYMV) cluster. WGMV was most similar to members of the Abutilon mosaic virus cluster but is not likely to be included in the Abutilon phylogenetic group because of the divergent sequence of the common region. These results indicate that geminiviruses infecting some weeds in Jamaica are distinct from crop-infecting geminiviruses in Jamaica and define a new geminivirus cluster.
Sudden Wilt of Melons in Southern Israel: Fungal Agents and Relationship with Plant Development
Authors: Pivonia S. , Cohen R. , Kafkafi U. , Ze'ev I. S. Ben , Katan J.
Published: May 2007

Fungi belonging to five genera, Monosporascus sp., Pythium aphanidermatum, Rhizoctonia solani, Olpidium sp., Fusarium solani, and F. proliferatum, were the species most frequently isolated from the root systems of wilted melon. Diseased plants were collected from 24 fields in the northern and central Arava region of southern Israel during the fall seasons of 1994 and 1995. In pathogenicity tests conducted under field conditions, in artificially inoculated microplots, the first wilt symptoms were observed at various stages of fruit maturation. High mortality levels (73 to 97%) were recorded for inoculation combinations in which Monosporascus sp. was involved. Inoculations with the other fungi listed resulted in lower incidences of wilt. The combination of F. solani and P. aphanidermatum resulted in higher mortality than that caused by each pathogen alone. Monosporascus sp. seems to be the primary pathogen, although other fungi could also induce wilt. The dry weight of plants grown in naturally infested soil ceased to accumulate 33 days after transplanting, in contrast to plants grown in methyl bromide-treated soil. At this stage, the first wilt symptoms were observed. Fruit load affected wilt incidence. At the end of the growing season, 98% mortality was recorded for plants having the normal fruit load (2.5 fruits per plant) compared with 75 and 12% for plants that had their fruits thinned to one or zero per plant, respectively.
Inheritance of Resistance to Race 0 of Phytophthora parasitica var. nicotianae from the Flue-Cured Tobacco Cultivar Coker 371-Gold
Authors: Carlson Shawn R. , Wolff Mary Anne F. , Shew H. D. , Wernsman E. A.
Published: May 2007

Black shank, caused by Phytophthora parasitica var. nicotianae, is a widespread and severe disease of tobacco throughout the southeastern United States. Partial resistance derived from the cigar tobacco cultivar Florida 301 has been the primary means of reducing losses to the disease for many years. The recently released tobacco cultivar, Coker 371-Gold (C 371-G), was found to provide an additional source of resistance to P. parasitica var. nicotianae. Although the resistance in C 371-G is being used widely by breeders, the origin and inheritance of this resistance mechanism was unknown. Two populations of doubled haploid lines derived from C 371-G were used to determine that C 371-G possesses a single, dominant gene designated Ph, which confers a very high level of resistance to race 0 of P. parasitica var. nicotianae. A greenhouse inoculation procedure was developed that provided an efficient means of screening for the presence of this resistance gene prior to selection in the field, and confirmed that Ph provides complete resistance to race 0 but no resistance to race 1 of P. parasitica var. nicotianae. Because Florida 301 resistance is effective against both races of the pathogen that occur in the major tobacco growing areas of the United States, combination of these two sources of resistance should provide enhanced protection of new tobacco cultivars to P. parasitica var. nicotianae.
Pathotypes of Cochliobolus sativus on Barley in North Dakota
Authors: Valjavec-Gratian M. , Steffenson B. J.
Published: May 2007

Spot blotch, caused by Cochliobolus sativus, has become an important disease on two-rowed barley cultivars in North Dakota. Information on the variability of virulence in C. sativus is essential for the development of spot blotch-resistant barley germ plasm. To establish the number and distribution of C. sativus virulence types in North Dakota, 22 isolates from the state were evaluated for their virulence on three differential barley genotypes: ND 5883, Bowman, and ND B112. Eleven additional isolates from Minnesota, South Dakota, Nebraska, Colorado, Japan, and China were included for comparison. Three pathotypes were identified from the thirty-three isolates tested based on the infection responses of the three host genotypes. These pathotypes were designated 0, 1, and 2 according to the coded triplet system of nomenclature. In North Dakota, pathotype 0 (exhibits low virulence on all three differentials) comprised 65%, pathotype 2 (exhibits high virulence on Bowman and low virulence on ND 5883 and ND B112) comprised 25%, and pathotype 1 (exhibits high virulence on ND 5883 and low virulence on Bowman and ND B112) comprised 10% of the total number of barley isolates examined. Within North Dakota, pathotype 1 was found in the east-central and northeastern region only, whereas pathotypes 2 and 0 were distributed throughout the state where samples were taken. Isolates with the pathotype 1 virulence pattern were identified in Colorado, Nebraska, Japan, and China. The remaining isolates collected outside North Dakota were pathotype 0. The information obtained from this study will facilitate the deployment of effective resistance to C. sativus in barley.
Characterization of Grapevine Rugose Wood Disease Sources from Italy
Authors: Credi R.
Published: May 2007

A collection of 27 sources of grapevine rugose wood (RW) disease from a viticultural region in northern Italy was analyzed by graft-inoculating vines of three selective Vitis indicators (V. rupestris cv. St. George, V. berlandieri × V. riparia cv. Kober 5BB, and hybrid cv. LN 33). On the basis of stem reactivity, different groups were identified among the selected RW inoculum sources: nine isolates induced pitting only on cv. St. George, whereas four induced grooving only on cv. Kober 5BB. These two groups were classified as isolates of rupestris stem pitting and Kober stem grooving. Three of the remaining isolates induced wood abnormalities on cvs. LN 33 and Kober 5BB, seven induced wood abnormalities on cvs. St. George and Kober 5BB, and four induced symptoms on all three indicators. These groups may represent RW sources with various disease combinations. RW-affected grapevine clones used as inoculum sources also were tested for virus infections by enzyme-linked immunosorbent assay (ELISA). ELISA revealed the presence of grapevine fleck virus, grapevine leafroll-associated closterovirus 1 and 3, and grapevine trichovirus A. These viruses infected most of the selected RW sources. However, eight of the latter were ELISA-negative. The findings are discussed, and the biological and etiological complexity of the RW phenomena in grapevine is confirmed.
First Report of Root-Knot Nematodes (Meloidogyne spp.) on Sunflowers in Mozambique
Authors: Zazzerini A. , Tosi L. , Vicente P. M.
Published: May 2007

Sunflower (Helianthus annuus L.) recently was reintroduced to Mozambique because of renewed interest in oil-seed production for domestic consumption. In April 1997, disease surveys were carried out in two fields in southern Mozambique (Maputo region). Several plants of Pan 735, a South African cultivar, showed yellowing of the leaves and stunting. These plants wilted during the day but recovered their turgidity at night. Diseased plants were easily pulled from the soil due to almost complete destruction of the root system. Numerous galls were found on affected roots, compared with healthy plants. Meloidogyne javanica (Treub) Chitwood and M. incognita (Kofoid & White) Chitwood were identified by M. Di Vito (personal communication) based on 20 female perineal patterns observed with a light microscope. M. incognita was more prevalent than M. javanica. Also observed were Alternaria helianthi (Hansf.) Tubaki & Nishihara and Sclerotium bataticola Taub. Root-knot nematodes (Meloidogyne spp.), common on sunflower, cause severe damage and reduce both seed yield and seed oil content (1). These two nematode species have also been observed on sunflower in other African countries (Zambia, South Africa, Egypt) but this is the first report of root-knot nematode on sunflower in Mozambique.

Reference: (1) M. Di Vito et al. Nematol. Medit. 24:109, 1996.
First Report of Choke, Caused by Epichloe typhina, on Orchardgrass in Oregon
Authors: Alderman S. C. , Pfender W. F. , Welty R. E. , Mellbye M. E. , Cook R. L. , Spatafora J. W. , Putnam M.
Published: May 2007

During July 1997, Epichloe typhina (Pers.:Fr.) Tul. in Tul. & C. Tul., the cause of choke disease, was found in four fields of an unnamed, experimental cultivar of orchardgrass (Dactylis glomerata L.) grown for seed near Halsey, OR. Disease occurrence in each of three fields was estimated by counting choked tillers in about 50 quadrats, 1 × 0.3 m, taken at 30-m intervals along three or four diagonal transects. In two fields, the disease was present in most quadrats (3% tillers infected). In the third field, choke was clustered in two areas, each with 1 to 8% infected tillers. A collection of E. typhina was deposited at the Oregon State University Mycological Herbarium (accession number 56,395). The disease had not been previously observed in commercial cultivars grown for seed in Oregon, with the exception of an infected tiller collected from an orchard-grass seed field during 1996. This is the first report of choke in Oregon on orchardgrass. Choke is an important disease in France, where it reduces seed yields of orchardgrass. Ten Oregon cultivars of orchardgrass were evaluated under field conditions in France in 1993 and 1994 for susceptibility to E. typhina. All cultivars were found susceptible to the disease; incidence of infected tillers ranged from 4 to 11%, with a mean of 7% (G. Sicard and R. E. Welty, unpublished). During 1996, several fragments of stroma of E. typhina were found among seed from a seed lot submitted to the Oregon State University Seed Lab for purity testing. This indicates that stroma may occur as a contaminant with seed, although it is not known if E. typhina would survive with the seed. E. typhina has not been reported to be seed-borne in orchardgrass.
Distribution of Thiabendazole-Resistant Colletotrichum musae Isolates from Guadeloupe Banana Plantations
Authors: de Lapeyre de Bellaire L. , Dubois C.
Published: May 2007

In Guadeloupe, anthracnose of bananas, caused by Colletotrichum musae, is commonly controlled by postharvest thiabendazole treatments. A survey was conducted in 45 banana packing stations of Guadeloupe to determine the proportion of isolates that were resistant to thiabendazole. Isolates resistant to thiabendazole concentrations of 1 μg/ml (R1), 5 μg/ml (R5), and 50 μg/ml (R50) were detected. Most of the resistant isolates were R1 or R5, and of 1,350 isolates, the proportion of resistant isolates (R1 + R5 + R50) was 23%, ranging from 0 to 70% depending on the location. The presence of resistant isolates was correlated with the exclusive use of benomyl as foliar aerial sprays from 1972 to 1982 to control Sigatoka disease. Isolates resistant to concentrations of 1 and 5 μg/ml were as pathogenic as the susceptible isolates and were not controlled satisfactorily by postharvest thiabendazole treatments. Alternative control measures and the importance of resistance in terms of anthracnose control in Guadeloupe are discussed.
Distribution and Seasonal Population Dynamics of Phytophthora citrophthora and P. parasitica in Arizona Citrus Orchards and Effect of Fungicides on Tree Health
Authors: Matheron M. E. , Porchas M. , Matejka J. C.
Published: May 2007

The distribution and seasonal population dynamics of Phytophthora citrophthora and P. parasitica within citrus orchards in southwestern and central Arizona were determined over a multiple-year period. In central Arizona, P. citrophthora alone, P. parasitica alone, or both pathogens together were recovered from 7, 37, and 41% of sampled orchards, respectively, whereas in the southwestern production area, the same pathogens alone or in combination were recovered from 17, 50, and 17% of sampled orchards, respectively. For a 6-year period, the average population density of P. parasitica in southwestern Arizona was 16.7 propagules/g of dry soil. For 2 of 3 years, the population density of P. citrophthora at the 10-cm soil depth was significantly higher in the spring than in the preceding winter or the following autumn season. There were no significant seasonal multiple-year differences in population levels of P. parasitica. Propagule densities of both pathogens, as well as root densities, generally decreased as soil depth increased from 10 to 60 cm. No consistent significant correlation was detected between propagule density of either pathogen and soil temperature or soil moisture at the time of collection. A multiple-year treatment program with fosetyl-Al or metalaxyl resulted in significantly healthier tree canopies and higher root densities compared to nontreated trees; however, population densities of P. citrophthora and P. parasitica did not differ significantly when nontreated trees were compared to those receiving fungicide treatments.
Comparison of Resistance Level to Tomato Yellow Leaf Curl Virus Among Commercial Cultivars and Breeding Lines
Authors: Lapidot Moshe , Friedmann Michael , Lachman Oded , Yehezkel Avidan , Nahon Saadia , Cohen Shlomo , Pilowsky Meir
Published: May 2007

The effect of tomato yellow leaf curl virus (TYLCV) on total yield and yield components of various resistant F1 tomato cultivars and new breeding lines was evaluated in the field. Seeds of the F1 hybrids 8484, 3761, Fiona, and Tyking and the new breeding lines TY172 and TY197 were sown in an insect-proof greenhouse. When the seedlings reached the first-leaf stage, they were inoculated with TYLCV by means of the whitefly vector Bemisia tabaci. Noninoculated plants of the same cultivar or line which were exposed to nonviruliferous whiteflies served as controls. After a short recovery period, the plants were transplanted to the field. The inoculated plants of each cultivar or line were compared with their respective control, noninoculated plants, in terms of total yield, average fruit weight and number, and plant fresh weight. Disease symptom development and virus accumulation in the inoculated plants were monitored. There were substantial differences among the different entries tested in the extent of yield loss relative to the corresponding noninoculated control plants as well as viral DNA accumulation levels. Plants of TY172 and TY197 suffered the least relative yield loss and contained the lowest level of viral DNA. Therefore, these two lines exhibited the highest level of resistance. These results clearly demonstrate the ability of the various resistant tomato cultivars and lines to inhibit the effects of the virus, even following inoculation at a very early stage of plant development.
Aspergillus Colonization and Aflatoxin Contamination in Peanut Genotypes with Resistance to Other Fungal Pathogens
Authors: Holbrook C. Corley , Wilson David M. , Matheron Michael E. , Anderson William F.
Published: May 2007

Indirect selection tools would be valuable in the development of peanut (Arachis hypogaea) cultivars with resistance to aflatoxin contamination. The objective of this study was to determine whether resistance to other fungi could be used as an indirect selection tool for resistance to colonization of peanut by Aspergillus flavus group fungi or aflatoxin contamination. Nine peanut genotypes with resistance to late leaf spot (Cercosporidium personatum) or white mold (Sclerotium rolfsii) were evaluated for 2 years at Tifton, GA, and Yuma, AZ. Plots were subjected to late-season heat and drought stress. None of the genotypes exhibited less colonization of shells or kernels by A. flavus group fungi than cv. Florunner when tested in Georgia or Arizona. None of the genotypes showed a reduced level of aflatoxin contamination in comparison to Florunner at either location. These results indicate that the mechanisms of resistance to other fungi operating in these genotypes are not effective in providing resistance to colonization by A. flavus group fungi or reducing aflatoxin contamination. Therefore, resistance to these fungi cannot be used as an indirect selection tool for resistance to aflatoxin contamination.
Use of Bicarbonates to Inhibit in vitro Colony Growth of Botrytis cinerea
Authors: Palmer Cristi L. , Horst R. Kenneth , Langhans Robert W.
Published: May 2007

Fungicide resistance in Botrytis cinerea has caused increased concerns about losses due to gray mold on many important agricultural and horticultural crops. Since bicarbonates have been reported to be an effective control of powdery mildew on greenhouse roses, the purpose of this research was to determine the effectiveness of bicarbonates against B. cinerea. Assessments were made of in vitro fungal colony growth in response to ammonium, potassium, and sodium bicarbonates. Bicarbonates inhibited colony growth at concentrations as low as 20 mM. In addition, comparisons of several ammonium, potassium, and sodium salts were conducted to determine whether cation or anion is the active moiety. Although the bicarbonate anion primarily affected growth, the ammonium cation also contributed greatly to fungal growth inhibition. With the exception of dibasic phosphate, only salts with high pKa values or that are reducing agents, or both, decreased colony growth. The effect of pH on B. cinerea was then examined. Since bicarbonate anion concentration is related to pH, this parameter was examined in combination with several salts to separate pH effects from bicarbonate effects. As pH increased from 7.0 to 8.5, colony growth decreased with bicarbonates and phosphates, but not with ammonium sulfate. Since bicarbonates and phosphates decreased colony growth more than could be accounted for from pH alone, and since both have buffering characteristics, buffering capacity was examined and found to decrease colony growth but not as much as bicarbonate. Therefore, bicarbonates control B. cinerea colony growth in vitro, and both pH and buffering capacity contribute to, but are not solely responsible for, growth inhibition.
Reaction of Selected Onion Cultigens to Pink Root under Field Conditions in New York
Authors: Coleman P. M. , Ellerbrock L. A. , Lorbeer J. W.
Published: May 2007

Levels of pink root, caused by Phoma terrestris, were assessed on onion (Allium cepa) growing in organic soils on farms in three New York counties during 1987 to 1990. Both commercial cultivars and lines from the USDA breeding program (collectively = cultigens) were evaluated for pink root incidence early in the season and for pink root severity later in the season. Onions were infected by P. terrestris as early as 6 to 8 weeks after field seeding. At maturity, portions of the root systems of all onions in all cultivars had turned pink. The cultigens with fewest symptoms were Sweet Sandwich, Keepsweet II, Spartan Banner 80, and inbred line MSU5785B.
Efficacy of Bacterial Seed Treatments for Controlling Pythium Root Rot of Winter Wheat
Authors: Milus E. A. , Rothrock C. S.
Published: May 2007

Pythium root rot, caused by various Pythium spp., is a widespread disease of wheat. The objective of this study was to identify bacterial strains from wheat roots in Arkansas that suppressed Pythium root rot and to compare their efficacy with that of bacterial strains from other areas. Bacterial strains (applied as seed treatments) that suppressed Pythium root rot in growth chamber assays were evaluated further for in vitro antibiosis against three Pythium spp. and for efficacy under field conditions. Pseudomonas fluorescens strain 2-79R, Burkholderia cepacia strain 1-23, and Pseudomonas sp. strain 1-30 were the most effective for suppressing Pythium root rot under field conditions and significantly (P = 0.10) increased yield in one experiment. Strains that were effective in the field also expressed in vitro antibiosis to at least two of three Pythium spp.; however, strains expressing the highest levels of antibiosis were not effective in the field. In the field, root rot suppression and yield enhancement were inconsistent across experiments and generally small in magnitude. Therefore, these strains have little potential for commercial use under the conditions in which they were tested.
First Report of Pratylenchus neglectus in New York
Authors: Timper P. , Brodie B. B.
Published: May 2007

Soil samples were collected from a field in Wyoming County near Portageville, NY, on 29 October 1992 and 23 November 1993. The field was planted with winter wheat (Triticum aestivum L.) from September 1991 to August 1992, and with potato (Solanum tuberosum L.) cv. Superior from May 1993 to September 1993. Thirty-nine and 45 samples were collected along three transects in 1992 and 1993, respectively. Two species of Pratylenchus were identified, P. neglectus (Rensch) Filipjev & Sch. Stek. (identification confirmed by A. M. Golden) and P. penetrans (Cobb) Filipjev & Sch. Stek. Their combined population densities were 134 ± 18 (mean ± SE per 100 cm3 soil) in 1992 and 195 ± 12 in 1993. P. neglectus was found in all samples, whereas P. penetrans was found in 33 and 78% of the samples in 1992 and 1993, respectively. Where both species occurred together, the density of P. neglectus was 7 to 8 times that of P. penetrans. In both years, spores of a nematode-pathogenic bacterium (probably a Pasteuria sp.) were found attached to the cuticle of P. penetrans (68% with spores in 1993) but were rarely attached to P. neglectus (less than 1% with spores). Although both Pratylenchus spp. are widespread in North America, this is the first report of P. neglectus in New York. Its dominance in the field was unexpected because P. penetrans and P. crenatus Loof are typically the dominant Pratylenchus spp. in potato production regions of northeastern North America (1). The presence of the bacterium, which appeared to be host-specific for P. penetrans, may help explain the dominance of P. neglectus.

Reference: (1) R. N. Huettel et al. Am. Potato J. 68:345, 1991.
Phyllosticta multicorniculata on Abies spp. in the Northeastern U.S.
Authors: Wenner N. G. , Merrill W.
Published: May 2007

Several needle blight fungi affect natural regeneration and Christmas tree plantations of Abies spp. in northeastern North America. Of these, Phyllosticta multicorniculata Bissett & Palm has been reported from A. balsamea (L.) Mill. in Ontario and Prince Edward Island, and from A. concolor (Gordon & Glend.) Lindl. ex Hildebr. in Wisconsin (1). In Quebec, P. multicorniculata was reported as an endophyte on symptomless needles of A. balsamea (2). In 1994, we collected this fungus in Grafton County, NH, defoliating lower branches of A. balsamea Christmas trees. In July and August 1996, we examined infected A. concolor Christmas trees in Lamoille County, VT. In July, approximately 50% of the 1996 needle complement on the lower 1 m of the crowns was infected and by August the incidence of infection on these branches increased to 75 to 100%. Less severe blighting occurred up to 1.5 m. Dead needles of the 1995 complement bore abundant, mostly empty, pycnidia of P. multicorniculata. The dead and dying distal ends of the 1996 needle complement bore abundant pycnidia of P. multicorniculata in various stages of maturation. This is the first report of this pathogen on Abies spp. in the northeastern U.S. The conidia from actively-sporulating pycnidia bore more numerous and longer appendages (1 to 16, average 7, up to 38 µm long) than the dried herbarium specimens of various ages used in the species description (1 to 5, up to 7 µm long) (1), or similarly reported from culture (2).

References: (1) J. Bissett and M. E. Palm. Can. J. Bot. 67:3378, 1989. (2) L. Petrini et al. Sydowia 43:148, 1991.
Detection of Phytoplasmas in Declining Pears in Southern Australia
Authors: Schneider B. , Gibb K. S.
Published: May 2007

Forty-nine pear tree samples collected in Victoria, most of them showing decline symptoms, were tested by polymerase chain reaction (PCR) analysis to detect phytoplasmas. Two universal phytoplasma-specific primer pairs, fP1/rP7 and fU5/rU3, were tested, but only fU5/rU3 amplified the phytoplasma DNA adequately. Nested PCR with universal and group-specific primers, however, proved more effective. Thirty pear trees reacted positively in a nested PCR assay. Restriction fragment length polymorphism (RFLP) analysis with the restriction enzymes MseI and AluI of the PCR fragment amplified with the primer pair fU5/rU3 revealed patterns identical to those from the sweet potato little leaf phytoplasma. This is the first report of a phytoplasma in pear in Australia.
Directional Spread of Septoria Leaf Spot in Tomato Rows
Authors: Parker S. K. , Nutter F. W. , Gleason M. L.
Published: May 2007

Disease severity of Septoria leaf spot in rows of fresh-market tomato plants that were not staked was assessed in 1992 and 1993 following inoculation of the center plant in each row. Both temporal disease increase and spatial disease gradients were best described by the logistic model. Apparent infection rates for Septoria leaf spot epidemics averaged 0.282 day-1(SE = 0.015, r2= 0.96, P < 0.0001) in 1992 and 0.260 day-1(SE = 0.011, r2= 0.96, P < 0.0001) in 1993. Apparent infection rates remained relatively constant at increasing distances from initial foci. Estimated values for disease gradient slopes 3 to 5 weeks after inoculation ranged from -0.26 to -1.05 m-1. Velocities of disease spread ranged from 0.3 to 1.3 m/day. Results of analysis of disease severity data for these 2 years suggest that Septoria leaf spot epidemics can develop at rapid rates, but steep disease gradients limit the velocity of spread.
Prunus tomentosa as a Diagnostic Host for Detection of Plum Pox Virus and Other Prunus Viruses
Authors: Damsteegt V. D. , Waterworth H. E. , Mink G. I. , Howell W. E. , Levy L.
Published: May 2007

The efficacy of seedlings of Prunus persica cv. GF 305, P. persica cv. Siberian C, and P. tomentosa (Nanking Cherry) as diagnostic indicators of plum pox infection, and of P. tomentosa for other Prunus viruses was evaluated by graft-inoculation with eight different strains or isolates of plum pox virus (PPV) representative of the Marcus (M) and Dideron (D) serogroups; and one isolate each of Prunus necrotic ringspot virus (PNRSV), prune dwarf virus (PDV), and sour cherry green ring mottle virus (GRMV). The initial PPV symptoms that developed in P. tomentosa within 30 days after inoculation were chlorotic banding along the midrib spreading to lateral veins from the leaf base upward, giving the appearance of a chlorotic oak-leaf pattern. Symptoms caused by PPV-M could be distinguished from those caused by PPV-D. Virus titers in infected P. tomentosa and GF 305 were higher than those in Siberian C when measured by triple antibody sandwich enzyme-linked immunosorbent assay. Infections by PNRSV, PDV, and GRMV were evident with the first flush of vegetative growth.
Occurrence of Passiflora Latent Carlavirus in Cultivated and Wild Passiflora Species in Australia
Authors: Pares R. D. , Gunn L. V. , Keskula E. N. , Martin A. B. , Teakle D. S.
Published: May 2007

A carlavirus was found to be widespread in commercial passionfruit (Passiflora edulis) plantings in New South Wales and Queensland. The particles observed were flexuous rods with mean dimensions of 651 × 12 nm. The particles often occurred in cells as aggregates but were never associated with pinwheel inclusion bodies, as is typical with passionfruit woodiness potyvirus. The particles showed a strong affinity (by immunoelectron microscopy) for antiserum prepared against Passiflora latent carlavirus (PLV) from Germany but increasingly less affinity for antisera against potato viruses S and M and PLV from the United States. Survey results indicated that PLV has been present in Australian passionfruit for more than 10 years and is widespread in most commercial cultivars in New South Wales and Queensland. The virus was twice found in wild Passiflora suberosa, once in wild P. subpeltata, and once in a feral seedling of P. edulis near an infected planting of P. edulis.
Infection Components of Wild-Type and Mutant Strains of Colletotrichum gloeosporioides f. sp. aeschynomene on Northern Jointvetch
Authors: Luo Y. , TeBeest D. O.
Published: May 2007

Colletotrichum gloeosporioides f. sp. aeschynomene causes an anthracnose of northern jointvetch, Aeschynomene virginica. Infection components, including lesion number, latent period, lesion expansion rate, and sporulation, were measured in experiments conducted in controlled environments. Two wild-type strains (3-1-3 and CLA 5A), four benomyl-resistant strains (B13, B15, B18 and B21), and four nitrate nonutilizing mutant strains (Nit A, Nit R, Nit L, and Nit T) of the pathogen were tested. Nitrate nonutilizing strains caused significantly fewer lesions on northern jointvetch than did wild-type and benomyl-resistant strains. Latent periods were significantly shorter for the wild-type strain CLA 5A than for most other strains. Lesion expansion rates of all benomyl-resistant strains were significantly slower than those of the wild- type strains. Large variations in sporulation were observed for most strains, and no differences in sporulation were found between wild-type and mutant strains. The usefulness of infection component analysis for the identification of competitiveness of strains of fungal pathogens for biological control of weeds is discussed.
Model for Economic Analysis of Fungicide Usage in Hybrid Corn Seed Production
Authors: Wegulo S. N. , Martinson C. A. , Rivera-C. J. M. , Nutter F. W.
Published: May 2007

A model was used to determine the economic benefits of using fungicides to control foliar diseases of seed corn. The components of the model were (i) increased net return to the seed company from fungicide usage, (ii) increased income, based on a wholesale price of $30 per unit of 80,000 seeds and a premium of $2 per unit of medium-sized seed, and (iii) increased expenses, calculated as the sum of fungicide and fungicide application costs, cost of processing increased seed, and increased payment to the grower by the seed company. Increased payment to the grower was calculated as the product of increased seed yield (before separation into fractions), May futures price for no. 2 commercial corn on 1 March, and an average inbred production factor. Increased net return was calculated by subtracting increased expenses from increased income. Yield data were obtained from fungicide trial experiments in commercial hybrid corn seed production fields in Iowa from 1990 to 1993. Of 169 fungicide treatments applied, 64 and 79% were profitable to the seed company and to the grower, respectively. The results from this study indicate that fungicide usage in hybrid corn seed production can be economically beneficial.
A New Geminivirus Associated with Tomato in the State of São Paulo, Brazil
Authors: Faria J. C. , Souza-Dias J. A. C. , Slack S. A. , Maxwell D. P.
Published: May 2007

The apical growth of about 20% of young tomato plants in observed fields near Campinas, State of São Paulo, Brazil, had yellow streaking of veins. Leaf symptoms developed into patches of yellow mosaic and the leaves became wavy. The whitefly Bemisia tabaci Genn. transmitted a pathogen from the infected tomato plants to healthy tomato and potato plants, reproducing the original symptoms in tomato. The apical leaves of infected potatoes showed yellow or green mottle that developed into leaf distortion with yellow blotches, symptoms indistinguishable from potato-deforming mosaic disease (2). DNA was extracted from these tomato and potato plants (1). Using DNA from the infected tomato plant, polymerase chain reaction (PCR) with the degenerate primer pair PAC1v1978/ PAV1c715 (1), which amplifies part of the rep gene (AC1 ORF), the common region (CR), and part of the cp gene (AV1 ORF), and with the primer pair PBC1v2039/PBV1c800, which amplifies part of BC1 ORF, CR, and part of BV1 ORF, gave virus-specific DNA fragments of the sizes expected from a whitefly-transmitted geminivirus. These were cloned and the complete nucleotide (sequences for DNA-A (pToYA, GenBank accession no. U79998) and DNA-B (pToYB, GenBank accession no. U80042) fragments obtained. Nucleotide identity between the CRs (184 nucleotides) was 90%, strongly indicating that those fragments correspond to a bipartite subgroup III geminivirus. PCR with the DNA from infected potato gave the expected size fragment for DNA-A. The partial sequence of the rep gene was 100% identical to the homologous sequence from the PCR fragment from the infected tomato. A search in the GenBank, EMBL, DDBJ, and PDB databases, using the BLAST program, found no identical geminivirus. The highest identity for the CR was 75% to tomato mottle geminivirus-Florida (ToMoV) and 74% to bean golden mosaic virus-Brazil. For the rep gene, the highest identity was 73% to tomato yellow leaf curl virus-Israel, an Old World geminivi-rus, followed by 71% to tomato golden mosaic virus-Brazil (TGMV) and ToMoV. For the cp gene, the highest identity was 86% to TGMV, followed by 83% to squash leaf curl geminivirus. Therefore, we propose the name tomato yellow vein streak geminivirus (ToYVSV) for this distinct virus (2).

References: (1) M. R. Rojas et al. Plant Dis. 77:340, 1993. (2) J. A. C. Souza-Dias et al. Summa Phytopathol. 22:57, 1996.
Occurrence and Distribution in Rwanda of Soilborne Fungi Pathogenic to the Common Bean
Authors: Rusuku Gerard , Buruchara Robin A. , Gatabazi Martin , Pastor-Corrales Marcial A.
Published: May 2007

The occurrence and distribution of soilborne fungi pathogenic to the common bean were determined by surveys conducted in seven of Rwanda's 10 prefectures during four growing seasons from 1989 to 1990. The pathogens were identified on the basis of symptoms, colony characteristics, reproductive structures, and pathogenicity tests. Of the plants sampled during the March through June 1989 season from four prefectures, 97% exhibited symptoms associated with soilborne pathogens. Root and hypocotyl symptoms appeared in plants sampled during the September through December 1989 season from the prefectures of Kigali (19%), Butare (40%), Gikongoro (33%), and Cyangugu (33%) and during the March through June 1990 season from Gisenyi (60%) and Kibungo (53%). Pythium spp., Macrophomina phaseolina, Rhizoctonia solani, and Fusarium oxysporum f. sp. phaseoli were isolated from all seven prefectures during all four seasons. Sclerotium rolfsii was isolated only during the 1990 September through December season. The frequency of isolation varied by region and season. Pythium spp. were the most frequently isolated fungi from about 40% of the samples, suggesting their potential importance in the root rot complex in Rwanda. The relative importance of the soilborne pathogens and possible relationships with existing cropping systems are discussed. These results will help focus efforts in developing management strategies for common bean diseases caused by soilborne pathogens in Rwanda.
Nonpathogenic Fusarium oxysporum Strain Fo47 Induces Resistance to Fusarium Wilt in Tomato
Authors: Fuchs J.-G. , Moënne-Loccoz Y. , Défago G.
Published: May 2007

Nonpathogenic Fusarium oxysporum strain Fo47 controls the incidence of Fusarium wilt. Four bioassays in which a strain of the pathogen F. oxysporum f. sp. lycopersici and Fo47 were not in direct contact were developed to evaluate whether Fo47 could induce resistance to Fusarium wilt in tomato plants. Fo47 and the pathogen were separated either physically or in time. Bio-assays were carried out under hydroponic conditions (two bioassays), in potting mix, or in autoclaved soil. Strain Fo47 protected tomato against Fusarium wilt in all four bioassays. Inoculation with Fo47 increased chitinase, β-1,3-glucanase, and β-1,4-glucosidase activity in plants, confirming the ability of Fo47 to induce resistance in tomato. This report is the first to demonstrate that a nonpathogenic strain of F. oxysporum can induce resistance to Fusarium wilt in tomato plants. This result has important practical implications for biocontrol of tomato diseases under commercial conditions.
Races of Pseudomonas syringae pv. glycinea on Commercial Soybean in Eastern North Dakota
Authors: Prom L. K. , Venette J. R.
Published: May 2007

In a survey conducted from 1991 to 1993 of 170 commercial soybean (Glycine max) fields in North Dakota, 80% had plants with obvious symptoms of bacterial blight. Strains (n = 164) isolated from field-grown plants and characterized as Pseudomonas syringae pv. glycinea were inoculated onto wounded, fully expanded unifoliolate leaves of differential cultivars Acme, Lindarin, Harosoy, Chippewa, Merit, Flambeau, and Norchief. Reactions of the differentials showed that five of the eight known races in the United States were present in North Dakota. Race 4 constituted 63%, race 6 was 22%, race 2 was 7%, race 3 was 0.3%, and race 5 was 0.1% of the race profile. Five pathogenic strains could not be characterized as one of the known races.
Weed Hosts of the Sugarcane Root Rot Pathogen, Pythium arrhenomanes
Authors: Dissanayake N. , Hoy J. W. , Griffin J. L.
Published: May 2007

Weeds in the Poaceae and Cyperaceae families prevalent in sugarcane fields were evaluated as potential hosts for the root rot pathogen, Pythium arrhenomanes. In greenhouse studies, bermudagrass, broadleaf signalgrass, browntop panicum, barnyardgrass, large crabgrass, goosegrass, itchgrass, johnsongrass, Italian ryegrass, and purple nutsedge became infected when grown in steam-treated soil infested with P. arrhenomanes. However, the extent of root colonization, symptom severity, and growth reductions varied among species. Symptom severity and root colonization by P. arrhenomanes were less when weeds were grown in sugarcane field soil in the greenhouse than when weeds were grown in Pythium-infested, steam-treated field soil. Levels of root colonization by P. arrhenomanes in both experiments were greatest for johnsongrass and itchgrass and lowest for browntop panicum, goosegrass, and Italian ryegrass. For weeds collected from sugarcane fields, frequencies for colonized plants were moderate to high, but the extent of root colonization by P. arrhenomanes was low for all except johnsongrass. The results indicate that weeds can serve as hosts for P. arrhenomanes and may play roles in the epidemiology of Pythium root rot on sugarcane.
Temporal and Spatial Analysis of Grapevine Leafroll-Associated Virus 3 in Pinot Noir Grapevines in Australia
Authors: Habili Nuredin , Nutter Forrest W.
Published: May 2007

An epidemic of grapevine leafroll disease (GLD), caused by grapevine leafroll-associated virus 3 (GLRaV-3), was monitored over an 11-year period in Nuriootpa, South Australia. Inoculum originated from infected budwood, and initial GLD incidence at the time of transplanting in 1986 was 23.1%. Infected vines were planted in a random spatial pattern. Change in disease incidence was not observed until 8 years after planting, when disease incidence increased to 27.9%. Disease incidence increased to 51.9% by 1996. Disease progress and rate curves (dy/dt versus time) indicated that the logistic (R2 = 96.2) and Gompertz (R2 = 96.3) growth models would best describe disease progress. However, the logistic model, which has a simpler data transformation with fewer model assumptions, was chosen for the purpose of comparing this epidemic (South Australia) with a GLRaV-3 epidemic in Cabernet Sauvignon grapevines in New Zealand. The logistic rate of GLD spread with respect to time was 0.35 logit/year in South Australia and was nearly three times faster (1.19 logits/year) for GLRaV-3 spread in New Zealand. Ordinary runs analyses indicated that the arrangement of infected vines within rows in South Australia was random up to 8 years after transplanting but subsequently became highly aggregated. Thus, GLD-infected plants are contributing to new infections (i.e., there is evidence for plant-to-plant spread), and a biotic vector with a steep dispersal gradient from each point source is likely to be involved.