bluuebunny/crossref_metadata_2025 huggingface dataset:
First Report of Zucchini yellow mosaic virus, Watermelon mosaic virus, and Cucumber mosaic virus in Bottlegourd (Lagenaria siceraria) in Serbia
Authors: Dukić N. , Krstić B. , Vico I. , Berenji J. , Duduk B.
Published: May 2007

During a cucurbit disease survey in August 2004, severe symptoms resembling those caused by viruses were observed on bottlegourd (Lagenaria siceraria (Molina) Standl.) in the Vojvodina region of Serbia. Symptoms included stunting, mosaic, green veinbanding, blistering, yellowing, chlorotic spots, leaf deformation, and fruit distortion. Leaf samples from 25 symptomatic plants were collected from two localities for virus identification using mechanical transmission and serological testing. Crude sap extract from leaf samples was mechanically inoculated onto bottlegourd and pumpkin (Cucurbita pepo) under greenhouse conditions. Field-collected bottlegourd and inoculated plants were tested using double-antibody sandwich enzyme-linked immunosorbent assays (DAS-ELISA). Positive reactions were obtained on collected and inoculated plants with polyclonal antiserum (Loewe Biochemica, Sauerlach, Germany) to Zucchini yellow mosaic virus(ZYMV) in 23 samples, with antiserum to Watermelon mosaic virus (WMV) in eight samples, and with antiserum to Cucumber mosaic virus (CMV) in seven samples. Each of the three viruses was detected in single as well as in mixed infections with the other two viruses. Biological characterization of viruses detected in single infections was done on the following indicator plants: Chenopodium amaranticolor, C. quinoa, Cucumis sativus, Cucumis melo, Citrullus lanatus, Nicotiana glutinosa, and N. tabacum cv. Samsun. The symptoms observed on indicator plants for each isolate corresponded to the results of DAS-ELISA (2,3). All three viruses are known to be important pathogens of cucurbit plants and were previously reported in pumpkin in Serbia (1). To our knowledge, this is the first report of ZYMV, WMV, and CMV in bottlegourd in Serbia.

References: (1) N. Dukić et al. J. Agric. Sci. 47:149, 2002. (2) D. E. Lesemann et al. Phytopathol. Z. 108:304, 1983. (3) H. Rahimian and K. Izadpanah. Phytopathol. Z. 92:305, 1978.
Clover yellow vein virus Identified in Ammi majus in Florida
Authors: Irey M. , Adkins S. , Baker C. A.
Published: May 2007

Ammi majus L., a member of the Apiaceae and also known as large bullwort, false Queen Anne's lace, or bishop's-weed, is frequently used in the floral trade to add a lacey look to floral bouquets. A. majus is native to the Mediterranean Region but it is cultivated in major growing areas including Holland, Israel, the United Kingdom, and the United States. During March 2005, virus-like symptoms including mosaic, generalized chlorosis, vein clearing, interveinal chlorosis, and leaf rugosity were observed in nearly all field-grown A. majus plants at two locations in Martin County, Florida. Inclusion body morphology suggested the presence of one or more potyviruses in the symptomatic plants. Potyvirus infection was confirmed in 11 symptomatic plants using a commercially available enzyme-linked immunosorbent assay (ELISA) kit (Agdia, Elkhart, IN). Nucleotide and deduced amino acid sequences of a 1,625-bp region of one of the reverse transcription-polymerase chain reaction products amplified with degenerate potyvirus primers (1) from total RNA of symptomatic plants (GenBank Accession No. DQ333346) were 96 to 97% and 93 to 99% identical, respectively, to Clover yellow vein virus (ClYVV) sequences in GenBank. All symptomatic plants tested were potyvirus positive using ELISA, but only a subset was infected with ClYVV suggesting that the field symptoms were the result of infection with additional potyviruses, all of which are likely aphid transmitted. Although several potyviruses have been reported from A. majus (2), to our knowledge, this represents the first report of ClYVV infection.

References: (1) A. Gibbs and A. Mackenzie. J. Virol. Methods 63:9, 1997. (2) P. Van Dijk and L. Bos. Neth. J. Plant Pathol. 95(Suppl.) 2:1, 1989.
Seed Treatment with Phosphonate (AG3) Suppresses Pythium Damping-off of Cucumber Seedlings
Authors: Abbasi P. A. , Lazarovits G.
Published: May 2007

A formulation of phosphonate (AG3) was tested as a seed treatment for the control of Pythium damping-off of cucumber (Cucumis sativus L.) plants under controlled environment and field conditions. Cucumber seed were treated by soaking for 10 min in phosphonate solution. They were then planted into peat-based mix or sandy-loam soil mixed with Pythium aphanidermatum or P. ultimum inoculum or into muck soil naturally infested with P. irregulare, P. ultimum, and other Pythium spp. Under growth-room conditions, phosphonate seed treatment provided more than 80% control of damping-off in all infested substrates tested. Effective disease control was obtained even when treated seed were stored for 5 weeks and up to 18 months prior to planting. In microplots containing naturally infested muck soil, phosphonate seed treatment decreased the percentage of diseased cucumber plants and increased total fresh weights compared with untreated seed and phosphonate post-planting drench. In field-plot tests 6 weeks after planting treated seed in Pythium-infested muck soil, cucumber stands were 63% compared with 18% in the control, which had no phosphonate exposure, and 53% in the post-planting drench. Tests for potential phytotoxicity in the greenhouse showed that radish and bok choy germination was reduced by phosphonate treatment but corn, cucumber, soybean, sugar beet, tomato, and wheat were not affected. Phosphonate seed treatment is a cost-effective way of protecting cucumber plants from Pythium damping-off.
Root-Knot and Root-Lesion Nematode Suppression by Cover Crops, Poultry Litter, and Poultry Litter Compost
Authors: Everts K. L. , Sardanelli S. , Kratochvil R. J. , Armentrout D. K. , Gallagher L. E.
Published: May 2007

Experiments using soil-incorporated cover crops and amendments of poultry litter (PL) and PL compost to suppress root-knot (RKN) and root-lesion nematodes were conducted in response to increasing nematode populations in Maryland's potato production areas. Identical experiments were established in microplots infested with Meloidogyne incognita or Pratylenchus penetrans. Treatments consisted of 12 3-year rotational sequences comprising potato (year 1) and cucumber (year 2) followed by a moderately RKN-resistant or susceptible soybean cultivar, castor bean, grain sorghum, or sorghum sudangrass; PL or PL compost were amended to some of the RKN-susceptible soybean and sorghum sudangrass plots. In the third year of the rotation, potato followed by soybean was planted in all 12 treatments. The RKN-resistant soybean, castor bean, sorghum sudangrass, and fallow or tillage decreased the populations of M. incognita compared with microplots where RKN-susceptible soybean had been grown. However, RKN populations quickly recovered. Root-lesion nematode was reduced in the spring of 2001 following application of high rates of PL and PL compost in 2000. In the fall of 2001, sorghum sudangrass alone or in combination with PL or PL compost, grain sorghum, or fallow or tillage reduced root-lesion nematodes compared with either soybean cultivar. No treatment affected root-lesion nematode the following year. The use of cover crops and PL compost is an effective method to reduce nematode populations only if successively incorporated into rotational cropping sequences.
Integrated Disease Management of Leaf Spot and Spotted Wilt of Peanut
Authors: Cantonwine E. G. , Culbreath A. K. , Stevenson K. L. , Kemerait R. C. , Brenneman T. B. , Smith N. B. , Mullinix B. G.
Published: May 2007

Field experiments were carried out to evaluate the effects of integrated management of early leaf spot, caused by Cercospora arachidicola, and spotted wilt, caused by Tomato spotted wilt virus (TSWV), on peanut (Arachis hypogaea) using host resistance, two tillage systems, and varying fungicide programs. Effects on pod yield and economic return were assessed. Genotypes C-11-2-39 and Tifrunner demonstrated the best field resistance to TSWV, whereas cvs. DP-1 and GA-01R and line C-28-305 were among the genotypes with the best leaf spot resistance. Epidemics of both diseases were comparable or suppressed in strip-tilled plots compared with conventionally tilled plots. Leaf spot intensity decreased with increased fungicide applications, but to a lesser degree with use of resistance and strip tillage. Yields and net returns were similar between tillage treatments in 2002 and lower in strip tillage in 2003. Genotypes with the greatest yields and returns were C-11-2-39, C-99R, and GA-01R. Returns were comparable among the four-, five-, and seven-spray programs in both years, despite differences in yield. The standard production system, Georgia Green in conventional tillage with seven sprays, resulted in lower returns than half the integrated systems tested in 2002, but had comparable or higher returns than nearly all systems in 2003. When significant, yields and returns were correlated with spotted wilt intensity to a greater degree than leaf spot intensity.
First Report of Rust Disease Caused by Uromyces galegae on Galega officinalis in Turkey
Authors: Tunali B. , Yildirim A. , Aime M. C. , Hernández J. R.
Published: May 2007

Galega officinalis L. is an obnoxious invasive weed in the United States and a potential target for biological control efforts. The plant, a member of the legume family, is native to western Asia and southern Europe. During September 2001, uredinial pustules were observed on leaves of G. officinalis L. in Kizilcahamam, Ankara. Specimens were examined microscopically and compared with published descriptions (2) and herbarium specimens in the U.S. National Fungus Collections, Beltsville, MD. The fungus was subsequently identified as Uromyces galegae (Opiz) Sacc. on the basis of morphological characteristics of the uredinia, urediniospores, and teliospores. The following description is from the Turkish material: uredinia subcircular to oblong, hypophyllous, rarely epiphyllous at petiole, and 0.5 to 1 mm in diameter; urediniospores subovoid to subglobose, 17.5 to 20.0 × 19.5 to 22.5 μm (average = 18.0 × 20.0 μm), wall 1 to 2 μm thick, finely echinulate, cinnamon brown, and with 3 to 5 usually equatorial germ pores; telia similar to uredinia; teliospores irregular in shape ranging from globose to ovoid to triangular, apex papillate, wall 2 to 3 μm thick, thicker at the apex, chestnut brown, strongly verrucose to tuberculate, 17.5 to 22.5 × 22.5 to 27.5 μm (average = 20.3 × 24.5 μm), pedicel hyaline, and easily broken. Voucher specimens are deposited in the U.S. National Fungus Collections (BPI 863535); a nucleotide sequence spanning the ITS2 and 28S rDNA genes of this isolate was obtained and deposited in Gen-Bank (Accession No. DQ250133). U. galegae has been reported on G. officinalis from Bulgaria, Greece, and Italy (1). To our knowledge, this is the first report of U. galegae in Turkey and marks the eastern-most record for its distribution.

References: (1) D. F. Farr et al. Fungal Databases. Systematic Botany and Mycology Laboratory, On-line publication, USDA-ARS, 2005. (2) M. Pantidou and D. M. Henderson. Notes R. Bot. Gard. Edinb. 29:277, 1969.
Factors Affecting the Development of Wood Rot on Lemon Trees Infected with Antrodia sinuosa, Coniophora eremophila, and a Nodulisporium sp.
Authors: Matheron M. E. , Porchas M. , Bigelow D. M.
Published: May 2007

Brown heartwood rot, which often is found in branches within lemon groves in southwestern Arizona, is caused by two basidiomycete fungi, Antrodia sinuosa and Coniophora eremophila. Another fungus, a species of Nodulisporium, has been recovered from small, dying lemon tree branches with an internal white wood rot. Studies were conducted from 1999 through 2002 to compare the extent of wood decay caused by these fungi (i) on lemon tree branches at different times of the year, (ii) on different types of citrus, (iii) on some desert woody perennial plants, and (iv) on lemon tree branches treated with selected fungicides. The mean length of wood decay columns recorded in lemon tree branches inoculated with A. sinuosa, C. eremophila, and the Nodulisporium sp. during the time periods of November to January, February to April, May to July, and August to October was 2.9, 4.7, 13.3, and 15.2 cm, respectively. There was a significant linear correlation between the length of wood decay columns and air temperature for all three pathogens. The mean length of wood decay columns for all time periods in branches inoculated with A. sinuosa, C. eremophila, and the Nodulisporium sp. was 11.8, 5.8, and 9.6 cm, respectively. In two trials, wood decay columns were significantly greater on Lisbon lemon tree branches inoculated with A. sinuosa compared with those on Marsh grapefruit and Valencia orange trees inoculated with the same pathogen. Wood decay in the presence of the Nodulisporium sp. was greater on branches of lemon compared with grapefruit trees in two trials and on lemon compared with orange trees in one of two trials. With the exception of C. eremophila on creosote bush, each of the three wood rot pathogens caused some wood decay in branches of velvet mesquite, salt cedar, Mexican palo verde, and creosote bush, four common desert perennials found in southwestern Arizona. Compared with nontreated but inoculated lemon trees, the length of wood decay columns in branches inoculated with A. sinuosa, C. eremophila, and the Nodulisporium sp. in the presence of propiconazole was reduced by 79, 94, and 92%, respectively, and, in the presence of azoxystrobin, was suppressed by 71, 80, and 89%, respectively. Current management guidelines focus on minimizing branch fractures and other nonpruning wounds in conjunction with early detection and removal of infected branches before the onset of the increased wood decay development period extending from May to October.
Residual Efficacy of Fungicides for Control of Dollar Spot on Creeping Bentgrass
Authors: Latin Richard
Published: May 2007

The duration of effective concentrations of fungicides for control of dollar spot on creeping bentgrass fairways was investigated using a bioassay technique. In each of three runs of the experiment, fungicide treatments were applied once to turf in replicated field plots; then, the plots were sampled periodically over 3 weeks by removing turf plugs from the field. The sampled plugs were placed in incubation containers and inoculated with sections from a 4-day-old colony of Sclerotinia homoeocarpa growing on potato dextrose agar. After a 96-h incubation period, the extent of pathogen growth on the turf plugs was measured. Results described a precipitous decline in effective concentration for all fungicide treatments beginning 7 to 10 days after application. The fungicides were only marginally effective at 14 days after application, and none provided any disease suppression at 21 days after application. The efficacy half-life (EHL) associated with four of the fungicides (chlorothalonil, iprodione, propiconazole, and thiophanate methyl) was estimated with two models. EHL estimates ranged from 6.1 to 15.2 days depending on the fungicide and the model. This research contributes to our knowledge of the duration of effective fungicide concentrations on creeping bentgrass and can provide insight for scheduling fungicide sprays for golf course fairways.
Resistance to Cucurbit yellow stunting disorder virus in Cucumber
Authors: Aguilar Juan M. , Abad Jesús , Aranda Miguel A.
Published: May 2007

Three hundred accessions of Cucumis sativus, including wild cucumbers, land races, traditional cultivars, and breeding lines, were evaluated under natural-infection conditions in order to identify potential sources of resistance to Cucurbit yellow stunting disorder virus (CYSDV). Although 100% of the susceptible control plants showed typical yellowing symptoms induced by CYSDV, another 24 C. sativus accessions showed partial or total absence of yellowing symptoms. In contrast, when CYSDV inoculation was carried out under controlled conditions, only two (A1 and A2) of these 24 accessions showed resistance to the virus. The nature of the resistance found in A1 and A2 plants was characterized by studying the pattern of virus accumulation and symptom development under controlled infection conditions, and by analyzing the possible nonpreference of Bemisia tabaci for these accessions under free-choice conditions. There was a delay in the establishment of the CYSDV infection in A1 and A2 plants which was evident shortly after inoculation and in apical leaves of the plants at long times after inoculation. Symptom severity was also less for A1 and A2 than for a susceptible control at 8 and 12 weeks postinoculation. Thus, delayed viral infection appeared to be associated with decreased symptom severity in A1 and A2 plants. Our results also showed nonpreference for plants of the A2 accession by B. tabaci, the CYSDV vector.
The Effect of Pythium ultimum and Soil Flooding on Two Soybean Cultivars
Authors: Kirkpatrick M. T. , Rothrock C. S. , Rupe J. C. , Gbur E. E.
Published: May 2007

The effect of flooding and Pythium ultimum on soybean, Glycine max, was determined in a series of greenhouse experiments using the cultivars Hutcheson and Archer. Seeds were planted into pasteurized soil either not infested or infested with sand-cornmeal inoculum of P. ultimum and either flooded at emergence for 2 days or at the four leaf node stage (V4) for 5 days. A nonflooded control was included in each experiment. Seeds placed directly into infested soil resulted in little or no stand for Hutcheson regardless of flood treatment, whereas stand was reduced for Archer only in the flooded infested soil treatment. Additional experiments were conducted by placing seed onto a 2- to 5-mm layer of pathogen-free soil on top of the infested soil. Flooding at emergence reduced plant height, growth stage, and top dry weight for Hutcheson and root fresh weight for both cultivars. Greater reductions for Hutcheson in root weight, and top dry weight in P. ultimum-infested soil in the soil layer experiments, also indicated that Hutcheson was more susceptible than Archer. Flooding alone decreased root weights, and infestation with P. ultimum reduced weights further resulting in an additive effect. This also was the case for plant height, growth stage, and top dry weight for Hutcheson for flooding at emergence. Root discoloration was greatly increased for both cultivars in infested soil flooded at emergence. Similar results were found when plants were flooded at V4; however, the effect was not as great as with flooding at emergence. These studies indicate that Pythium damping-off and root rot may account for a portion of the negative response of soybean to flooding. The results also indicate that Archer has some resistance to P. ultimum.
New Outbreaks of Bacterial Wilt of Dry Bean in Nebraska Observed from Field Infections
Authors: Harveson R. M. , Schwartz H. F. , Vidaver A. K. , Lambrecht P. A. , Otto K. L.
Published: May 2007

Bacterial wilt caused by Curtobacterium flaccumfaciens pv. flaccumfaciens was one of the more problematic diseases of dry bean (Phaseolus vulgaris L.) throughout the irrigated High Plains (Colorado, Nebraska, and Wyoming) in the 1960s and early 1970s, but has not been observed since that time. However, in August of 2003, plants exhibiting wilting and irregular, interveinal necrotic foliar lesions surrounded by a bright yellow border were found in three dry bean fields (market class Great Northern) in Scotts Bluff County, Nebraska. During 2004, plants exhibiting identical symptoms were additionally found occurring in more than 40 dry bean fields in western Nebraska. Affected fields were planted with dry bean from multiple market classes and seed sources, including yellow bean, Great Northern bean, and pinto bean, and incidence varied from trace levels to 80 to 90%. Isolations were made from leaf and stem tissues and seeds collected after harvest from infected plants, and all yielded slow-growing, creamy yellow or orange, fluidal colonies on nutrient broth-yeast extract medium. The bacterium was identified as C. flaccumfaciens pv. flaccumfaciens based on cell morphology (coryneformshaped motile rods), positive Gram stain and KOH reactions, fatty acid profiles, and BIOLOG (Hayward, CA) identifications. Great Northern (cv. Orion) plants were inoculated by bacterial suspensions (5 × 107 CFU/ml) injected into leaf axils adjacent to the first fully expanded trifoliolate and were incubated in the greenhouse under ambient conditions fluctuating between 24 and 35°C. Wilting symptoms developed 7 days after inoculation with foliar necrosis and yellowing symptoms appearing after 24 days. Identical bacterial colonies were reisolated from inoculated tissues, completing Koch's postulates. Although recent reports of wilt have been made in North Dakota (2) and western Canada (1) in 1995 and 2002, respectively, they were based only on the presence of discolored seeds observed in dockage from processing plants after harvest. To our knowledge, this report represents the first widespread observations of bacterial wilt from field infections in Nebraska in more than 30 years.

References: (1) J. R. Venette et al. Plant Dis. 79:966, 1995. (2) T. F. Hsieh et al. Plant Dis: 86:1275, 2002.
First Report of Pathogenicity Group-3 of Leptosphaeria maculans on Winter Rape in Hungary
Authors: Szlávik Sz. , Barasits T. , Fernando W. G. D.
Published: May 2007

Blackleg, caused by Leptosphaeria maculans, is an increasing threat to winter rape (Brassica napus L.) in Hungary. The winter rape acreage has been increasing, and the occurrence and severity of the disease has become widespread in all rapeseed-growing regions throughout Hungary in a very short time. The blackleg-infected rape stubbles were collected in the autumn of 2003 in Ikervár, County Vas where the disease was severe. Ascospores were obtained from pseudothecia growing on infected rape stubble (susceptible cvs. GK Helga and Aladin). Three single-spore cultures were grown on V8 agar medium at room temperature and fluorescent light. The culture characteristics fit the type culture description for L. maculans. Pycnidiospores that formed on V8 plates were flooded with 10 ml of sterile distilled water. Seeds of cvs. Westar, Glacier, and Quinta obtained from the Department of Plant Science, University of Manitoba, Canada were sown in plastic pots containing peat mix. Seedlings were maintained in a growth chamber at 24°C with 90% relative humidity and a 16-h photoperiod. Seven days after sowing, cotyledons were wound inoculated with a 10-μl droplet of pycnidiospore suspension (1.5 × 107 spores ml-1). Interaction phenotypes (IP) were scored 10 days after inoculation using a 0 to 9 scale (1). All three isolates from Ikervár were highly virulent on cvs. Westar (8.8 to 8.9) and Glacier (8.1 to 8.3) and avirulent on cv. Quinta (0.8 to 0.9). The IP ratings indicated that these isolates belonged to pathogenicity group-3 (PG-3). To our knowledge, this is the first report of the presence of L. maculans PG-3 in Hungary. At the current time, PG-3 has caused at least 30% yield losses in susceptible cultivars of winter rape.

Reference: (1) A. Mengistu et al. Plant Dis. 75:1279, 1991.
First Report of Alternaria Brown Spot of Citrus Caused by Alternaria alternata in Peru
Authors: Marín J. E. , Fernández H. S. , Peres N. A. , Andrew M. , Peever T. L. , Timmer L. W.
Published: May 2007

Alternaria brown spot, caused by Alternaria alternata (Fr.) Keissler, causes leaf, twig, and fruit lesions and reduces yield and fruit quality of many tangerines (Citrus reticulata Blanco) and their hybrids (3). In 2003, characteristic symptoms of brown spot were observed on young leaves and fruit of ‘Minneola’ tangelo in the Satipo Province of Peru. In 2004, the disease was discovered in the provinces of Chanchamayo, Leoncio Prado, and La Convención in the Junin, Huanuco, and Cusco regions, respectively, as well as in the Apurimac and the Ene valleys. In 2005, it was confirmed in the province of Oxapampa in the Pasco Region. Brown-to-black lesions surrounded by yellow halos and veinal necrosis were observed on young leaves, often causing abscission of young shoots and twig dieback. Light brown, circular lesions were observed on fruit, and when severe, resulted in premature abscission. Isolations from infected leaves and twigs were made on potato dextrose agar (PDA) with 10 μg/ml of benomyl. Colonies that developed after 5 days at 27°C were olive brown-to-black and produced small, muriform, pigmented conidia typical of A. alternata. On PDA without benomyl, gray colonies with conidia typical of Colletotrichum gloeosporioides were recovered frequently. Inoculation of three detached young shoots of ‘Minneola’ by spraying with a suspension of 105 conidia/ml of A. alternata produced leaf and twig symptoms characteristic of the disease after 48 h and confirmed pathogenicity of three isolates. Symptoms were not observed on control leaves sprayed with water nor on an equal number of leaves inoculated with a suspension of 105 conidia/ml of C. gloeosporioides. Reisolation of A. alternata from diseased tissue fulfilled Koch's postulates. DNA was extracted from 17 isolates and a partial endopolygalacturonase gene was amplified and sequenced (2). Sequences of all 17 isolates were identical, and in BLAST searches of the NCBI database, the closest matches were A. alternata accession nos. AY295023.1, AY295022.1, and AY295021.1 with 100, 99.8, and 99.8% sequence similarity, respectively. Phylogenetic analyses revealed that all isolates from Peru clustered with brown spot isolates from Israel, Turkey, South Africa, and Australia (1). These results, along with morphological characterization and pathogenicity tests, confirm the identity of the fungus as the tangerine pathotype of A. alternata. The disease has significantly reduced yield and the commercial value of fruit and may be a limiting factor for the production of susceptible cultivars in those areas of Peru.

References: (1) T. L. Peever et al. Phytopathology 92:794, 2002. (2) T. L. Peever et al. Mycologia 96:119, 2004, (3) L.W. Timmer et al. Pages 19–21 in: Compendium of Citrus Diseases. 2nd ed. L. W. Timmer et al eds. The American Phytopathological Society, St. Paul, MN, 2000.
First Report of Northern Stem Canker of Soybean Caused by Diaporthe phaseolorum var. caulivora in North Dakota
Authors: Bradley C. A. , Li S.
Published: May 2007

In early September 2003, patches of soybean (Glycine max) plants in a field in Foster County, ND had dead branches with reddish brown cankers at the nodes. Stem tissue with cankers from two plants were excised and immersed in a 0.5% NaOCl solution for 1 min, rinsed with sterilized distilled water, and placed into Petri dishes containing potato dextrose agar (PDA) amended with streptomycin sulfate (200 mg/liter). Four fungi were hyphal tipped and grown on PDA, acidified PDA, or water agar (WA) with soybean stem pieces incubated at 21°C with 24-h light and identified by culture and spore morphology after 3 to 4 weeks. Cultures were identified as Diaporthe phaseolorum var. caulivora that produced white colonies with interspersed cottony tufts of mycelium on PDA (1). Stromata were small and scattered irregulary on the plate. Perithecia of the D. phaseolorum var. caulivora isolates were black and globose with eight-spored asci formed on soybean stem pieces on WA. To confirm pathogenicity of the D. phaseolorum var. caulivora isolates, soybean plants (cv. NuTech 0606) were grown in the greenhouse and inoculated with recovered D. phaseolorum var. caulivora isolates. The stems of soybean plants at the V3 stage were excised just below the fourth node. Mycelia plugs of the four different 1-week-old cultures of D. phaseolorum var. caulivora were placed into the large end of disposable micropipette tips (200 μl). The micropipette tip containing a D. phaseolorum var. caulivora culture was subsequently placed over a cut soybean stem. The four D. phaseolorum var. caulivora isolates were used to inoculate 10 stems apiece. To serve as controls, 10 cut soybean stems were inoculated with micropipette tips containing plugs of noninfested PDA and 10 cut stems were not inoculated. Ten days after inoculation, micropipette tips were removed and lesions that had developed on the stem were measured. The mean lesion lengths of the D. phaseolorum var. caulivora inoculated stems ranged from 48 to 82 mm and were significantly (P ≤ 0.05) greater than the lesion lengths of the noninfested PDA (3 mm) and no PDA (1 mm) controls. Northern stem canker was only observed in the one field; however, surveys were not conducted to determine the prevalence of the disease throughout the soybean-production area of North Dakota. To our knowledge, this is the first report of northern stem canker on soybean in North Dakota.

Reference: (1) F. A. Fernandez et al. Stem canker. Pages 33–35 in: Compendium of Soybean Diseases. 4th ed. The American Phytopathological Society, St. Paul, MN, 1999.
Weather Factors Associated with Development of Sorghum Ergot in the Texas Panhandle
Authors: Workneh F. , Rush C. M.
Published: May 2007

Since its first introduction in 1997, sorghum ergot, caused by Claviceps africana, has been observed yearly in the Texas Panhandle, where it has caused occasional epidemics in hybrid-seed production fields. To determine the effect of weather factors on ergot severity, inoculation experiments were conducted in 2003 and 2004 using sequentially planted sorghum plants. Sorghum flowers were inoculated with three inoculum concentrations (1 × 104, 1 × 105, or 1 × 106 spores/ml) prepared from infected sorghum panicles producing fresh honeydew. Each year, inoculations were conducted several times during sorghum flowering periods so that time of inoculations would coincide with different weather conditions. Weather variables (temperature, relative humidity, wind speed, precipitation, and radiation) were collected using an onsite weather station. Infected and uninfected florets were counted 8 to 13 days after inoculation, and the percentage of infected florets per sorghum panicle (severity) was determined. In both years, temperature and relative humidity were the predominant factors responsible for variations in sorghum ergot severity with all inoculum densities. Relationship between ergot severity and each of the two variables depended on inoculum density. Measurable infection occurred at a maximum temperature of 34°C with 1 × 106 spores/ml, while there was little or no infection at 30°C with 1 × 104 spore/ml. Cumulative departures from minimum relative humidity and maximum temperature infection thresholds 12, 18, 24, 36, 48, and 72 h after inoculation were calculated and regressed against ergot severity for each inoculum level. Cumulative departures of hourly temperature and relative humidity from maximum temperature and minimum relative humidity infection thresholds 18 and 24 h after inoculation were best related to sorghum ergot severity (R 2 = 89 and 91; P < 0001, respectively). Models based on these two time-durations then were used in predicting a regional site-specific ergot severity potential using radar-estimated rainfall.
Real-Time PCR Assays for Detection and Quantification of Sweetpotato Viruses
Authors: Kokkinos C. D. , Clark C. A.
Published: May 2007

Viral diseases, especially those caused by mixed infections, are among the economically most important diseases of sweetpotato. The difficulties inherent in detecting, quantifying, and isolating viruses directly from sweetpotato have impeded progress in sweetpotato virus research. Real-time polymerase chain reaction (PCR) assays were developed for the detection and relative quantification in singleplex reactions of the potyviruses Sweet potato feathery mottle virus (SPFMV), Sweet potato virus G (SPVG), and Ipomoea vein mosaic virus (IVMV); the crinivirus Sweet potato chlorotic stunt virus (SPCSV); and the begomovirus Sweet potato leaf curl virus(SPLCV) directly from infected sweetpotato plants. There was no significant effect from potential inhibitors in total nucleic acid extracts from sweetpotato leaves on the performance of the real-time PCR assays. Virus titers of SPFMV, IVMV, and SPVG were quantified using real-time PCR and found to be lower in singly infected sweetpotato plants compared with singly infected Brazilian morning-glory (Ipomoea setosa Ker.) and I. nil cv. Scarlet O'Hara plants. Real-time PCR was a more efficient detection method for SPLCV than conventional PCR assay.
Spatial Pattern of Verticillium Wilt in Commercial Mint Fields
Authors: Johnson Dennis A. , Zhang Hao , Alldredge J. Richard
Published: May 2007

Spatial patterns of mint plants with symptoms of Verticillium wilt caused by Verticillium dahliae were characterized in 10 commercial mint fields in Washington using several spatial analysis methods. The disease was assessed in 0.76-by-0.76-m quadrats (width of mint rows was 0.76 m) in randomly selected study sections varying in size from 5 to 76 m wide by 57 to 396 m long. The variance-to-mean ratio identified aggregation of diseased stems within quadrats even though probability distributions associated with cluster data did not fit the data well. Generally, there was more clustering within than across rows according to both doublets and runs analyses. Total number of wilt foci ranged from 5 to 170 per field, and mean size of foci ranged from 1 to 2.7 quadrats. In one field observed repeatedly, total foci increased from 24 to 104, and the mean size of foci increased from 1.0 to 1.3 quadrats in the same section of the field from one year to the next. Size of foci increased to 2.7 quadrats in a third year of sampling the same field. Mean focus size was larger within than across crop rows in 10 of 13 field-sampling occasions. The proximity index ranged from 0.88 to 1.00, indicating highly compacted disease foci. The statistical methods employed were useful in describing, quantifying, and visualizing spatial patterns of infected mint in commercial fields. Verticillium wilt spread during the life of the perennial mint crop. Inoculum for much of the secondary increase likely did not directly originate from micro-sclerotia present in soil before the crop was planted or from infected rhizomes that originally were planted.
Comparative Efficacy, Selection of Effective Partners, and Application Time of Strobilurin Fungicides for Control of Cercospora Leaf Spot of Sugar Beet
Authors: Karadimos D. A. , Karaoglanidis G. S.
Published: May 2007

In this study, we attempt to optimize the use of strobilurin fungicides by testing the efficacy of azoxystrobin, kresoxim-methyl, pyraclostrobin, and trifloxystrobin under field conditions, by testing for the most efficient partners in fungicide mixtures, and by testing control efficacy of strobilurin fungicides applied at several application times to determine the better options for disease management. Results showed that trifloxystrobin was the most efficient strobilurin fungicide, followed by pyraclostrobin. Azoxystrobin provided a modest to poor control efficacy, whereas kresoxim-methyl provided only poor disease control efficacy. Mixtures of azoxystrobin and trifloxystrobin with either chlorothalonil or maneb and difenoconazole or flutriafol were tested for their efficacy in controlling the disease. The results showed that the azoxystrobin-containing mixtures provided significantly better control compared with that obtained by single applications of each mixture component. The mixtures of trifloxystrobin with maneb or with difenoconazole or flutriafol provided control efficacy similar to that obtained by single applications of trifloxystrobin, whereas the mixture of trifloxystrobin and chlorothalonil provided significantly lower control efficacy compared with the other trifloxystrobin-containing mixtures tested. For both strobilurin fungicides tested, the calculated ratio between the observed and the expected control efficacy ranged around the value of 1, suggesting additive interactions between the mixtures' components. To determine the most appropriate time for strobilurin fungicides application, trifloxystrobin was applied as the first two, the middle two, or the final two consecutive treatments of six fungicide applications. The remaining fungicide treatments in the spray schedules were carried out by applying the systemic fungicide difenoconazole. Results showed that a higher control efficacy was obtained when trifloxystrobin was applied in either of the earlier applications.
First Report of Hop stunt viroid in Apricot in China
Authors: Yang Y. A. , Wang H. Q. , Guo R. , Cheng Z. M. , Li S. F. , Sano T.
Published: May 2007

Hop stunt viroid (HSVd), a member of the family Pospiviroidae, was first described as the causal agent of hop stunt disease in Japan. It has since been found in a wide range of hosts including herbaceous and woody hosts (e.g., hop, cucumber, grapevine, citrus, plum, peach, pear, apricot, almond, and pomegranate). It was also detected and characterized in apricot where infection appears to be latent (1). The viroid occurs frequently in apricot. In southeastern Spain, the presence of HSVd was found to infect 81% of apricot trees (2). Apricots originated in China and are extensively cultivated, but HSVd infection in this host has not been reported. In September 2005, a single symptomatic apricot tree, ‘Yin Bai’, one of the most popular and widely grown cultivars in China, was discovered at the Institute of Fruit Science in Changping District in Beijing, Peoples Republic of China. Observed symptoms included a number of yellow spots with an irregular border that scattered in an irregular manner over the leaf surface. Total RNA was extracted and used for return-polyacrylamide gel electrophoresis and reverse transcription-polymerase chain reaction (RT-PCR) (4). Results of both assays were positive for HSVd. A 297-bp full-length DNA fragment was amplified by RT-PCR using primers R1 (5′-GCTGGATTCTGAGAAGAGTT-3′) complementary to HSVd residues 87–106 for the RT reaction, followed by R2 (5′-AACCCGGGGCTCCTTTCTCA-3′) complementary to HSVd residues 67–84 and forward primer F3 (5′-AACCCGGGGCAACTCTTCTC-3′) residues 79–96 for PCR. The primers are located in the strictly conserved central region of the conserved HSVd group and contain the unique endonuclease restriction site SmaI. The amplified products were cloned into pGEM-T (Promega, Madison, WI) and selected for further analysis on the basis of the results of restriction digests. Six individual clones were sequenced and three different sequences were obtained. Nucleic acid sequence (GenBank Accession No. DQ362901) obtained from one clone was 99.3% (nucleotide changes T206→C, C233→T) identical to HSVd.apr8 (GenBank Accession No. Y09349) (3). Sequence (GenBank Accession No. DQ362904) obtained from three clones was 99.7% (nucleotide change C233→T) and a third sequence (GenBank Accession No. DQ362905) obtained from two clones was 99.3% (nucleotide changes G107→A, C233→T) identical to HSVd.apr8. Further investigation is necessary to determine whether the symptoms observed are associated with the viroid infection. To our knowledge, this is the first report of HSVd isolated from apricot in China.

References: (1) N. Astruc et al. Eur. J. Plant Pathol. 102:837, 1996. (2) M. C. Cañzres et al. Acta Hortic. 472:581, 1998. (3) S. A. Kofalvi et al. J. Gen. Virol. 78:3177, 1997. (4) S. F. Li et al. Ann. Phytopathol. Soc. Jpn. 61:381, 1995.
First Report of Pythium aphanidermatum on Basella rubra in Japan
Authors: Tojo M. , Yonemoto K. , Kawamura A.
Published: May 2007

Basella rubra L. (Indian spinach, Japanese name Tsurumurasaki) is cultivated worldwide as an ornamental and its aerial parts are consumed as a vegetable and health food. A severe rot of leaves, stems, and roots was found on B. rubra cv. Midori grown in a commercial field at Naruto-City (34°11′N, 134°36(E) in Tokushima Prefecture, Japan from May to September 2004. More than 50% of approximately 2,100 plants in the field were destroyed by the disease. Soft, black lesions appeared initially at the base of the stems in 2- to 5-month-old plants and enlarged gradually upward and downward within 2 days after plant injury caused by heavy rainfall. A fluffy, white mass of mycelium appeared on the surface of lesions under moist conditions. A Pythium species was routinely isolated from rotted stems and roots and identified as Pythium aphanidermatum (Edson) Fitzpatrick on the basis of its morphology on a grass leaf water culture (2). Characteristics of isolate OPU743 (NBRC No. 101556, MAFF No. 239847) included hyphae as much as 10 μm wide, terminal oogonia 17.8 to 28.8 μm in diameter, and monoclinous or diclinous antheridia 8.8 to 10.9 μm wide, either terminal or intercalary, with one or rarely two per oogonium. Oospores were aplerotic, 13.5 to 22.6 μm in diameter. Sporangia were terminal or occasionally intercalary, and either inflated filamentous hyphae or complexes of swollen hyphal branches were present in cultures. Cardinal temperatures for growth on potato carrot agar were 10°C minimum, 37°C optimum, and 40°C maximum with a daily radial growth rate of 32.9 mm at 25°C. Pathogenicity tests were conducted on potted 3-month-old B. rubra (cv. Midori). A wound (1 mm deep and 5 mm long made by a razor) on the surface of the stem of the plant was inoculated with an 8-mm-diameter agar disk of isolate OPU743 (grown at 25°C for 48 h on potato dextrose agar) attached to a stem of the plant using a paraffin film. The inoculated plants were placed in transparent plastic bags and kept in a growth chamber at 24 to 26°C with continuous light (82 to 126 μmol·m-2·s-1). The experiment was done four times with three plants in each experiment. The same number of plants was used for the noninoculated control. Dark brown rot of stems and leaves developed on 66.7% of inoculated plants within 2 days after inoculation. P. aphanidermatum reisolated from diseased tissues was morphologically identical to the original isolate OPU743. Noninoculated control plants showed no symptoms. P. aphanidermatum has been described on B. rubra in Brazil (1), but has not been reported from other regions of the world. To our knowledge, this is the first report of P. aphanidermatum on B. rubra in Japan.

References: (1) C. F. Robbs. A Lavoura 74:43, 1972. (2) A. J. Van Der Plaats-Niterink. Stud. Mycol. 21:1, 1981.
Virulence Polymorphism of Puccinia recondita f. sp. tritici and Effectiveness of Lr Genes for Leaf Rust Resistance of Wheat in Ukraine
Authors: Elyasi-Gomari S. , Panteleev V. K.
Published: May 2007

In 2002 and 2003, 1,300 isolates of Puccinia recondita f. sp. tritici were obtained from six commercial cultivars of wheat at three locations in the eastern forest-steppe region of Ukraine. All isolates were tested for virulence on an international set of eight differential cultivars. Seventeen known wheat leaf rust races and several new, unnamed races were identified. The most common races in each year were races 61, 149, and 192. In 2003, up to 20 isolates each of the seven most common leaf rust races plus 8 to 10 isolates of unnamed races were tested for virulence to 35 near-isogenic wheat lines with different single Lr genes for leaf rust resistance. Isolates were polymorphic for virulence on Lr1, Lr2a, Lr2b, Lr2c, Lr9, Lr19, Lr23, Lr26, and the combination Lr27 + Lr31. No isolates were found virulent on Lr24, Lr25, or Lr28, and few isolates were virulent on Lr9. Few isolates of known races but most isolates of the new, unnamed races were virulent on Lr19. The 35 Lr gene lines also were exposed to mixed-race inoculum in field plots to tests effectiveness of their resistance. Lines with Lr24, Lr25, and Lr28 suffered no leaf rust damage in the field, and lines with Lr9, Lr18, Lr35, Lr36, and the combination Lr27 + Lr31 showed less than 10% severity.
Geocenamus brevidens Associated with Reduced Yield of No-Till Annual Spring Wheat in Oregon
Authors: Smiley Richard W. , Whittaker Ruth G. , Gourlie Jennifer A. , Easley Sandra A.
Published: May 2007

Associations between stunt nematodes and yield of no-till annual spring wheat (Triticum aestivum) were examined at two eastern Oregon locations. Geocenamus brevidens was the only species detected at one location and was mixed with Tylenchorhynchus clarus at another location. Six cultivars were planted with or without application of aldicarb during 2001. Inverse correlations between yield and stunt nematode density were significant at the G. brevidens-only site (P = 0.04) but not the G. brevidens + T. clarus site (P = 0.44). Yields were inversely correlated (P < 0.01) with stunt nematode populations at both sites during 2002. Aldicarb improved grain yields at both locations during 2001 (17 and 24%, P < 0.01) but not at the single location treated with aldicarb during 2002 (10%, P = 0.06). A lack of association between yield and T. clarus in 19 previously unreported experiments is discussed. Reduced wheat yield in response to stunt nematodes in Oregon is likely due to parasitism by G. brevidens and not T. clarus. This is the first report associating G. brevidens with suppression of wheat yield in the Pacific Northwest. Further studies are needed to define cropping systems and locations where G. brevidens may cause economic damage.
Effect of Two Allexivirus Isolates on Garlic Yield
Authors: Cafrune E. E. , Perotto M. C. , Conci V. C.
Published: May 2007

Garlic (Allium sativum) is infected by numerous viruses forming a viral-complex, which is widely distributed in the garlic production regions of Argentina. This work is the first report of the effect of two Allexivirus isolates, Garlic virus A (GarV-A) and Garlic virus C (GarV-C), on garlic yield. Garlic cvs. Morado-INTA and Blanco-IFFIVE were used in the experiments, and four treatments were evaluated: plants inoculated with GarV-A only, GarV-C only, virus-free plants (negative control), and plants infected with the virus-complex. Assays were performed in anti-aphid cages and in the field during 2002 and 2003. GarV-A caused significant reductions in bulb weight (14 to 32%) and diameter (6 to 11%) compared with the negative control in the two cultivars under both assay conditions. GarV-C caused less damage than GarV-A (15% in weight and 5% in diameter) with respect to the negative control in cv. Blanco-IFFIVE, and did not produce significant yield losses in cv. Morado-INTA in either year or under either assay condition.
Formation of Conidial Pseudochains by Tomato Powdery Mildew Oidium neolycopersici
Authors: Oichi W. , Matsuda Y. , Nonomura T. , Toyoda H. , Xu L. , Kusakari S.
Published: May 2007

The formation of conidial pseudochains by the tomato powdery mildew Oidium neolycopersici on tomato leaves was monitored using a high-fidelity digital microscope. Individual living conidiophores that formed mature conidial cells at their apex were selected for observation. The conidial cells were produced during repeated division and elongation by the generative cells of the conidiophores. Under weak wind conditions (0.1 m/s), these conidial cells did not separate from each other to produce a chain of conidial cells (pseudochain). The pseudochains dropped from the conidiophores once four conidial cells were connected. The conidiophores resumed conidium production, followed by another cycle of pseudochain formation. The formation of pseudochains by tomato powdery mildew was not influenced by the ambient relative humidity. On the other hand, the conidial cells produced were easily wind dispersed without forming pseudochains when conidiophores were exposed to stronger winds (1.0 m/s). The present study successfully demonstrated that the pathogen required wind to disperse progeny conidia from the conidiophores and produced conidial pseudochains when the wind was below a critical level, independent of high relative humidity as reported previously.