bluuebunny/crossref_metadata_2025 huggingface dataset:
First Report of Sirococcus conigenus on Deodar Cedar in Oregon
Authors: Bronson J. J. , Stanosz G. R. , Putnam M. L.
Published: May 2007

Cedrus deodara is a highly valued conifer widely grown as an ornamental in the Pacific Northwest and southern United States. C. deodara in the Pacific Northwest is normally problem free but occasionally is damaged by dieback of shoot tips, which has been associated with a fungus resembling Sirococcus conigenus. In February 2002, bleeding cankers were observed on 2- to 4-year-old stems of potted nursery stock of C. deodara cv. Karl Fuchs from Clackamas County, OR. Cankers were dark with indistinct margins, shallow, and up to 30 cm long. Infection appeared to have originated with small twigs that had died. Cultures isolated from discolored bark on streptomycin-amended potato dextrose agar (PDA) produced conidiomata with hyaline, fusiform, two-celled conidia typical of S. conigenus (1,3). Inter-simple sequence repeat-polymerase chain reaction fingerprints of an isolate from one of these trees were consistent with the P group of S. conigenus (mostly from hosts in Picea and Pinus spp.) (2). This isolate (02–04, ATCC MYA-2969) was used to inoculate two shoots on each of 12 3-year-old potted deodar cedars in each of two trials. Removing a needle wounded each shoot, and an agar plug colonized with mycelium was placed over the wound and held in place for 2 weeks with Parafilm. Sterile agar plugs were applied to two wounded control shoots on each tree in each trial. After 10 weeks, 25 of 48 inoculated shoots were blighted and drooped with yellow to brown needles that eventually dropped. The pathogen was reisolated from 24 of 25 symptomatic shoots but not from asymptomatic or control shoots. To our knowledge, this is the first confirmed report of S. conigenus as a pathogen of C. deodara.

References: (1) P. F. Cannon and D. W. Minter. Taxon 32:572, 1983. (2) D. R. Smith et al. For. Pathol. 33:141, 2003. (3) B. Sutton. The Coelomycetes. Commonw. Mycol. Inst., Kew, Surrey, England, 1980.
First Report of Heterobasidion parviporum (S Group of H. annosum sensu lato) on Tsuga spp. in Asia
Authors: Dai Y. C. , Korhonen K.
Published: May 2007

Members of the Heterobasidion annosum (Fr.) Bref. complex are among the most important pathogens in coniferous forests of Europe and North America. Three intersterile groups (P, S, and F) have been found in this complex from Europe (1) and were recently segregated into three species based on intersterility, host preferences, and morphology (4). In a survey of wood-rotting fungi in China in 2002, Heterobasidion spp. were found on Tsuga chinensis (Franch.) Pritz and T. dumosa (D. Don) Eichl. in natural forests from the northern Sichuan Province of southwestern China (32°43′ to 33°11′ N, 103°50′ to 103°53′ E.). Basidiocarps of the fungus were relatively common on decayed wood in roots of dead trees, stumps, and fallen trunks. We collected four basidiocarps (Dai 4045, 4051, 4214, and 4224 in the Institute of Applied Ecology, Chinese Academy of Sciences, IFP) from three stands of mixed coniferous forests and made 40 homokaryotic, single-basidiospore cultures (02046, 02047, 02050, and 02051 in the Finnish Forest Research Institute). Two homokaryons from each basidiocarp were paired with homokaryotic tester strains of European H. annosum (P group), H. parviporum Niemelä & Korhonen (S group), and H. abietinum Niemelä & Korhonen (F group). The pairings showed that the progeny from the four basidiocarps are H. parviporum. The Chinese isolates did not form clamp connections with H. annosum sensu stricto, and a strong demarcation line developed in all these pairings. In contrast, the Chinese isolates formed clamp connections in almost every pairing with European H. parviporum, the clamp connections developed in both sides of the pairings, and no distinct demarcation line was present in most of these pairings. The Chinese homokaryons were also compatible with European H. abietinum, but in most of these pairings, clamp connections were found in the isolate from China but not in the European tester, and a demarcation line was present in most of the pairings. In contrast to H. annosum sensu stricto, the Chinese basidiocarps had smaller pores (4.5 to 6 per mm versus 3 to 4.5 per mm), and a thin tomentum on the pileal surface in contrast to the basidiocarps of H. abietinum. Previously, H. parviporum was found in Asia on coniferous hosts such as Abies, Larix, Picea and Pinus spp. (2). The North American S group of H. annosum sensu lato attacks species of Tsuga spp. in western North America (3), but to our knowledge, this is the first report of H. parviporum on native species of Tsuga spp. outside North America.

References: (1) P. Capretti et al. Eur. J. For. Pathol. 20:231, 1990. (2) Y. C. Dai and K. Korhonen. Eur. J. For. Pathol. 29:273, 1999. (3) G. M. Filip and D. J. Morrison. North America. Pages 405–427 in: Heterobasidion annosum. Biology, Ecology, Impact and Control. CAB International, Wallingford, UK, 1998. (4) T. Niemelä and K. Korhonen. Taxonomy of the genus Heterobasidion. Pages 27–33 in: Heterobasidion annosum. Biology, Ecology, Impact and Control. CAB International, Wallingford, UK, 1998.
Identification of Turnip mosaic virus Isolates Causing Yellow Stripe and Spot on Calla Lily
Authors: Chen C. C. , Chao C. H. , Chen C. C. , Yeh S. D. , Tsai H. T. , Chang C. A.
Published: May 2007

Two virus cultures, RC4 and YC5, were isolated in Taiwan from calla lily (Zantedeschia spp.) cv. Black magic displaying yellow spot and stripe on leaves. Both isolates were mechanically transmitted to various hybrids of Zantedeschia and induced systemic symptoms similar to those observed on diseased Black magic. In addition to Zantedeschia spp., the two virus isolates also infected several cruciferous species and induced mosaic symptoms. Electron microscopy revealed the presence of flexuous virus particles about 750 nm in length. The two isolates were propagated in and purified from mustard plants and were used as immunogens for production of antisera in rabbits. In enzyme-linked immunosorbent assay and sodium dodecyl sulfate-immunodiffusion tests, both antisera reacted strongly with their homologous antigens and with antigens of two Turnip mosaic virus (TuMV) isolates from radish (TuMV-R) and lisianthus (TuMV-L), but not with 21 other different potyviruses tested. In reciprocal tests, antisera against TuMV-R and TuMV-L also reacted strongly with RC4 and YC5 antigens, indicating that these two calla lily isolates are serologically indistinguishable from other known TuMV strains. Cloning and sequence analyses confirmed that both isolates shared 95 to 99% of deduced amino acid sequence identities in the coat protein genes with those of various known TuMV strains. This investigation represents the first record of the natural infection of TuMV in calla lily.
Partial Molecular Characterization of Dahlia mosaic virus and Its Detection by PCR
Authors: Nicolaisen M.
Published: May 2007

Dahlia mosaic virus (DMV) is the causal agent of one of the most important diseases of Dahlia pinnata. The nucleotide sequence of a 1,195-bp fragment of its genome was amplified and characterized. Based on this sequence, polymerase chain reaction (PCR) assays were developed for detection of DMV. The nucleotide sequence confirmed the classification of DMV as a member of genus Caulimovirus since it was similar to a region covering partly open reading frames (ORFs) IV and V found in caulimoviruses. The two most closely related viruses on the basis of comparison of ORF V fragments were shown to be Figwort mosaic virus and Mirabilis mosaic virus with 66.6 and 68.1% identity, respectively. Two PCR assays were developed using identical primer pairs: a real-time PCR based on SYBR green chemistry and a conventional PCR. Both methods clearly discriminated DMV-infected and healthy dahlia. The real-time PCR assay detected DMV-infected material that was diluted 105-fold in healthy material.
Improved Efficacy of Newly Formulated Bacteriophages for Management of Bacterial Spot on Tomato
Authors: Balogh B. , Jones J. B. , Momol M. T. , Olson S. M. , Obradovic A. , King P. , Jackson L. E.
Published: May 2007

Bacteriophages are currently used as an alternative method for controlling bacterial spot disease on tomato incited by Xanthomonas campestris pv. vesicatoria. However, the efficacy of phage is greatly reduced due to its short residual activity on plant foliage. Three formulations that significantly increased phage longevity on the plant surface were tested in field and greenhouse trials: (i) PCF, 0.5% pregelatinized corn flour (PCF) + 0.5% sucrose; (ii) Casecrete, 0.5% Casecrete NH-400 + 0.5% sucrose + 0.25% PCF; and (iii) skim milk, 0.75% powdered skim milk + 0.5% sucrose. In greenhouse experiments, the nonformulated, PCF-, Casecrete-, and skim milk-formulated phage mixtures reduced disease severity on plants compared with the control by 1, 30, 51, and 62%, respectively. In three consecutive field trials, nonformulated phage caused 15, 20, and 9% reduction in disease on treated plants compared with untreated control plants, whereas plants treated with PCF- and Casecrete-formulated phage had 27, 32, and 12% and 30, 43, and 24% disease reduction, respectively. Plants receiving copper-mancozeb treatments were included in two field trials and had a 20% decrease in disease in the first trial and a 13% increase in the second one. Skim milk-formulated phage was tested only once and caused an 18% disease reduction. PCF-formulated phage was more effective when applied in the evening than in the morning, reducing disease on plants by 27 and 13%, respectively. The Casecrete-formulated phage populations were over 1,000-fold higher than the nonformulated phage populations 36 h after phage application.
Invasion Pathways of Karnal Bunt of Wheat into the United States
Authors: Marshall David , Work Timothy T. , Cavey Joseph F.
Published: May 2007

Karnal bunt of wheat (caused by Tilletia indica) was first detected in the United States in Arizona in 1996. The seed lots of infected, spring-habit, durum wheat associated with the initial detection were traced to planted fields in California, Arizona, New Mexico, and Texas. However, in the summer of 1997, the disease appeared in unrelated, winter-habit, bread wheat located over 700 km from the nearest potentially contaminated wheat from 1996 (and destroyed prior to reinfection). Here, we examined potential invasion pathways of the fungus associated with the movement of wheat into the United States. We analyzed the USDA/APHIS Port Information Network (PIN) database from 1984 through 2000 to determine likely pathways of introduction based on where, when, and how the disease was intercepted coming into the United States. All interceptions were made on wheat transported from Mexico, with the majority (98.8%) being intercepted at land border crossings. Karnal bunt was not intercepted from any other country over the 17-year period analyzed. Most interceptions were on wheat found in automobiles, trucks, and railway cars. The majority of interceptions were made at Laredo, Brownsville, Eagle Pass, and El Paso, TX, and Nogales, AZ. Karnal bunt was intercepted in all 17 years; however, interceptions peaked in 1986 and 1987. Averaged over all years, more interceptions (19.2%) were made in the month of May than in any other month. Our results indicate that Karnal bunt has probably arrived in the United States on many occasions, at least since 1984. Because of the relatively unaggressive nature of the disease and its reliance on rather exacting weather conditions for infection, we surmised that it is possible this disease has a long period of latent survival between initial arrival and becoming a thriving, established disease.
Evaluation of the MI82 Corn Line as a Source of Resistance to Aflatoxin in Grain and Use of BGYF as a Selection Tool
Authors: Maupin L. M. , Clements M. J. , White D. G.
Published: May 2007

Our objectives were to determine if the corn (Zea mays) inbred MI82 has alleles for resistance to Aspergillus ear rot (caused by Aspergillus flavus) and aflatoxin accumulation in grain that can be transferred to commercially used inbreds, and to determine the types and magnitudes of gene action, heritabilities, and gain from selection for low levels of bright greenish-yellow fluorescence (BGYF), aflatoxin, and ear rot with MI82. Also, we hoped to determine if selection against BGYF would substantially reduce the concentration of aflatoxin in grain. Primary ears and ground grain from inbred MI82 (P1), the susceptible inbred B73 (P2), and the F1, F2, F3, BCP1S1, and BCP2S1generations developed from these inbreds were evaluated for BGYF, concentration of aflatoxin in grain, and severity of Aspergillus ear rot in 2000 and 2001. Dominance was the most important gene action associated with low levels of BGYF and a low concentration of aflatoxin in grain. Heritabilities for low levels of BGYF (83.5%), aflatoxin (74.1%), and ear rot (62.8%) were high. Correlation coefficients between aflatoxin and BGYF were high in both years (r = 0.75 and 0.79 for 2000 and 2001, respectively). Unlike aflatoxin, BGYF was not affected by the year in which plants were grown. Selection for low levels of BGYF prior to selection based on aflatoxin concentration is as effective as selection for either factor alone. MI82 has value in programs designed to improve the resistance of commercially used corn inbreds.
A Rapid PCR-Based Method for the Detection of Magnaporthe oryzae from Infected Perennial Ryegrass
Authors: Harmon Philip F. , Dunkle Larry D. , Latin Richard
Published: May 2007

Gray leaf spot caused by Magnaporthe oryzae is a serious disease of perennial ryegrass in the midwestern United States. Symptoms of gray leaf spot can be confused with those caused by other fungal diseases that also are common during periods of high temperatures and ample moisture. Because turf managers must select appropriate fungicides for remedial treatment, accurate and timely identification of the pathogen is essential for efficient and effective disease management. We developed and evaluated a polymerase chain reaction (PCR)-based method to detect M. oryzae in infected perennial ryegrass tissue. The method utilizes a commercially available kit that is used for isolation and amplification of plant DNA from leaf tissue. The kit protocol was modified and found to be reliable for the extraction of M. oryzae DNA from infected perennial ryegrass. Primers were designed to amplify a 687-bp fragment of the Pot2 transposon that is found in multiple copies in the genome of the pathogen. The protocol amplified amounts of purified DNA as low as 5 pg and consistently and specifically detected M. oryzae in single diseased leaf blades as well as in field samples of infected perennial ryegrass. The total time required for detection was approximately 4 to 8 h.
New Fungicides and Application Strategies Based on Inoculum and Precipitation for Managing Stone Fruit Rust on Peach in California
Authors: Soto-Estrada A. , Förster H. , Hasey J. , Adaskaveg J. E.
Published: May 2007

In greenhouse and field studies, rust on cling peach caused by Tranzschelia discolor was significantly reduced on leaves and fruit compared with that on controls by foliar applications of wettable sulfur, an agricultural oil, a substituted aromatic (e.g., chlorothalonil), as well as benzimidazole (e.g., benomyl, thiophanate-methyl), sterol biosynthesis inhibiting (e.g., myclobutanil, propiconazole, tebuconazole), and strobilurin (e.g., azoxystrobin) fungicides. The timing of treatments was a significant factor in reducing disease in most trials. Protective programs using wettable sulfur, tebuconazole, or azoxystrobin applied after stem lesion detection (ASLD) and before forecasted rains were highly effective. In the most effective programs for managing the disease, however, these fungicides were applied after stem lesion detection and occurrence of rainfall. Under highly conducive field environments for disease, single applications of azoxystrobin or tebuconazole at ASLD were significantly more efficacious than sulfur. Dormant treatments of liquid lime sulfur, chlorothalonil, or thiophanate-methyl/agricultural oil, however, were ineffective in reducing the disease during the subsequent spring and summer seasons. This is the first management program for rust on cling peach that utilizes inoculum and precipitation events to optimize timing of fungicide applications.
Influence of Environmental Factors on Severity of Citrus Scab and Melanose
Authors: Agostini J. P. , Bushong P. M. , Bhatia Alka , Timmer L. W.
Published: May 2007

Citrus scab, caused by Elsinoe fawcettii, and melanose, caused by Diaporthe citri, produce external blemishes on citrus fruit, reducing acceptability of the fruit for the fresh market. In laboratory studies, rough lemon seedlings and grapefruit seedlings were inoculated with conidia of E. fawcettii and D. citri, respectively, and exposed to a range of temperatures and durations of leaf wetness. Scab was most severe at temperatures from 23.5 to 27°C and much less severe at 17, 20, 30, or 32°C. A leaf wetness duration of 4 h was sufficient for some infection, but 12 h of leaf wetness were needed for maximum infection with scab. Melanose was equally severe at 24 and 28°C, moderate at 20°C, and low at 32°C. Melanose infection was minimal with 4 h of leaf wetness, moderate with 8 to 16 h, and reached maximum levels at 24 h or more of leaf wetness. In field studies, grapefruit seedlings with new shoots were placed beneath trees weekly, and disease severity was evaluated in relation to environmental factors. Melanose severity increased sharply with an increase in total weekly rainfall, leaf wetness durations of greater than 80 h per week, and average temperatures above 22°C.
Influence of Wheat Cultivar, Species of Fusarium, and Isolate Aggressiveness on the Efficacy of Fungicides for Control of Fusarium Head Blight
Authors: Mesterházy Á. , Bartók T. , Lamper C.
Published: May 2007

Attempts to control Fusarium head blight (FHB) with fungicides have been highly variable. Variability is caused by cultivar resistance, fungicide efficacy, fungicide coverage, timing, and pathogen aggressiveness. In this research, fungicides were tested on winter wheat cultivars with different levels of resistance to FHB using different isolates of Fusarium graminearum and F. culmorum to evaluate the role of host resistance and isolate aggressiveness on severity of FHB. Fungicides were applied to groups of wheat heads to provide full coverage. Incidence and severity of FHB was measured by the severity of head symptoms, percentage of Fusarium-damaged kernels (FDK), yield loss, and deoxynivalenol (DON) contamination. Development of FHB was affected by fungicides, cultivars, fungal isolates, and most of the two-way interactions of these variables. Among the fungicides tested, those containing tebuconazole tended to be more effective in reducing FHB. Reduction of disease in susceptible cultivars may not be adequate to produce marketable yields under conditions of high disease pressure. In most cases, if a fungicide reduced FHB visual symptoms, similar decreases were detected in yield loss, DON concentration, and FDK reaction. In 1998, an increase in DON contamination compared with the Fusarium check was observed with azoxystrobin and carbendazim on the more susceptible cultivar. This increase in DON with some fungicide requires additional research. Research to develop more resistant cultivars, better spraying technology, and more effective fungicides is also needed.
Sexual Stage Development of Uromyces appendiculatus and Its Potential Use for Disease Resistance Screening of Phaseolus vulgaris
Authors: McMillan M. S. , Schwartz H. F. , Otto K. L.
Published: May 2007

In June 1989, pycnia and aecia of the bean rust pathogen were observed in eastern Colorado on volunteer plants of pinto bean cvs. UI 114 and UI 126 that grew from seed that remained in the field after harvest the previous season. Harvested aeciospores were viable and produced typical reddish-brown uredinia on unifoliolate leaves of UI 114 seedlings in the greenhouse. Evidence of bean rust overwintering has been confirmed in 10 years from 1989 to 2002 in eastern Colorado and the surrounding region. Overwintering conditions were reproduced at Fort Collins, CO in fall 1992 and spring 1993. Debris treatments had significantly higher disease incidence on stems, total number of lesions on stems, disease incidence on leaves, and total number of lesions on leaves of plants of pinto cvs. UI 114 and Olathe than plants without debris. Bean leaves of both cultivars had significantly higher disease incidence than stems. There also was an increased incidence of aecial infection for UI 114 seedlings that germinated through leaf debris with rust compared with stem debris under greenhouse conditions with abundant moisture. Bean leaf debris smaller than 0.36 mm in diameter resulted in significantly more aecial lesions on UI 114 than larger leaf debris and stem debris. Additional greenhouse experiments demonstrated that diverse collections of naturally occurring, overwintered, rust-infested bean debris from eastern Colorado produced different levels of pycnial and aecial infection on pinto cvs. UI 114, Olathe, and Chase. Chase, currently resistant to the uredinial stage of the prevalent bean rust races in Colorado and surrounding states, had a low incidence of aecial lesions on seedling stems when exposed to pycnial and aecial stages in the greenhouse. These observations indicate that selection of bean rust resistance genes should rely on multiple sources of resistant germ plasm to counter the potential increase in new races that could derive from sexual recombination in bean-production regions.
Impact of Planting Dates and Climatic Factors on the Incidence and Severity of Sorghum Grain Mold in Morelos, Mexico
Authors: Montes-Belmont R. , Méndez-Ramírez I. , Flores-Moctezuma H. E. , Nava-Juárez R. A.
Published: May 2007

It is difficult to develop control strategies for grain mold of sorghum because of the limited information on the epidemiology of grain mold in Mexico. The objectives of this study were to identify the fungi associated with grain mold in Morelos, Mexico, and to explore the relationship among planting dates, disease development, and relative humidity and temperature. Fusarium thapsinum was isolated from 97% of the grains from field samples of infested sorghum grains in Morelos, Mexico. The influence of planting dates on the development of sorghum grain mold was determined at Tlayca, Morelos, Mexico, during the rainy seasons of 1998, 1999, and 2000. Incidence of grain mold varied annually, but disease incidence and severity were highest in 1998. Planting dates from 1 June to 13 July had the highest incidence of grain mold during the 3 years. Throughout the study, disease severity was generally low, and yield was not affected. The late planting dates in 1999 and 2000 had reduced yields due to terminal drought of the crop. Increase of disease was predicted by mean temperature, but not by mean relative humidity.
First Report of Papaya ringspot virus on Papaya in Iran
Authors: Pourrahim R. , Farzadfar Sh. , Golnaraghi A. R. , Shahraeen N.
Published: May 2007

Papaya, a popular fruit crop native to the American tropics, was introduced to the southern tropical provinces of Iran in the 1990s and its cultivation is widely increasing in these areas. During April 2000, severe leaf distortion and mottling were observed on papaya trees (Carica papaya) in Hormozgan Province in southern Iran. Affected trees were stunted and yielded less fruit. Samples of papaya leaf extracts (1:10 wt/vol) in 0.01 M potassium phosphate buffer (pH 7.0) were mechanically inoculated on indicator host plants, causing local lesions on Chenopodium amaranticolor and C. quinoa and chlorotic spots followed by systemic mosaic symptoms on Cucurbita pepo. Papaya ringspot virus (PRSV) was detected in the leaf samples of papaya plants and the inoculated Cucurbita pepo plants using double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) with PRSV-specific antisera (polyclonal antibody AS-0086 and PV-0244, DSMZ, Braunschweig, Germany). PRSV causes one of the most destructive diseases of papaya worldwide (1). PRSV has been previously reported from Citrullus vulgaris and Cucumis melo from Iran as Watermelon mosaic virus 1 (2), but to our knowledge, this is the first report of occurrence of PRSV on papaya in Iran.

References: (1) D. E. Purcifull et al. Papaya ringspot virus. No. 292. CMI/AAB, Surrey, England, 1984. (2) F. Ebrahim-Nesbat. Phytopathol. Z. 79:352, 1974.
First Report of Raspberry bushy dwarf virus on Red Raspberry and Grapevine in Slovenia
Authors: Mavrič I. , Marn M. Viršček , Koron D. , Žežlina I.
Published: May 2007

In 2002, severe vein yellowing and partial or complete yellowing of leaves was observed on some shoots of red raspberry (Rubus idaeus) cvs. Golden Bliss and Autumn Bliss. Sap of infected plants of cv. Golden Bliss was inoculated onto Chenopodium quinoa and Nicotiana benthamiana. Faint chlorotic spots were observed on inoculated leaves of C. quinoa approximately 14 days after inoculation but no systemic symptoms appeared. No symptoms were observed on N. benthamiana. Raspberry bushy dwarf virus (RBDV) was detected in the original raspberry plant using double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) with polyclonal antiserum (Loewe Biochemica, Sauerlach, Germany). Systemic infections of inoculated C. quinoa and N. benthaminana were confirmed using DAS-ELISA. In 2001 and 2002, unusual virus symptoms were observed on grapevine grafts (Vitis vinifera) of cv. Laški Rizling. Symptoms appeared as curved line patterns and yellowing of the leaves. No nepoviruses were found in symptomatic plants, but RBDV was confirmed using DAS-ELISA. RBDV infection was later confirmed in grapevine cv. Štajerska Belina with similar symptoms. RBDV was transmitted mechanically from grapevine to C. quinoa where it was detected by immunocapture-reverse transcription-polymerase chain reaction (IC-RT-PCR). IC-RT-PCR was used to amplify a part of the coat protein gene of the virus from raspberry and grapevine, and the amplification products were sequenced (1). The obtained sequence shared at least 93% nucleotide sequence identity with other known RBDV sequences, which confirmed the serological results. To our knowledge, this is the first report of the natural occurrence of RBDV in grapevine and also of RBDV infection of red raspberry in Slovenia.

Reference: (1) H. I. Kokko et al. Biotechniques 20:842, 1996.
First Report of Tobacco ringspot virus in Table Grapes in Michigan
Authors: Schilder A. M. C. , Gillett J. M. , Byrne J. M. , Zabadal T. J.
Published: May 2007

In 1998, several 10-year-old ‘Marquis’ and ‘Vanessa’ (Vitis sp.) table grapevines at the Southwest Michigan Research and Extension Center in Benton Harbor started showing decline symptoms such as stunted shoots with small leaves and berries. Vines eventually stopped producing fruit and died. In 1999, symptomatic vines were indexed on cucumber (Cucumis sativus L. ‘National Pickling’) cotyledons, which developed chlorotic local lesions. Symptomatic cucumber tissue was tested using Ouchterlony double diffusion with polyclonal antibodies for Tomato ringspot virus (ToRSV) and Tobacco ringspot virus (TRSV) provided by D. Ramsdell. Samples tested positive for TRSV. ‘Marquis’ vines (9 of 45) in the affected area also tested positive in double-antibody sandwich enzyme-linked immunosorbent assay with polyclonal antibodies for TRSV (Agdia, Inc., Elkhart, IN). Analysis of soil samples from the site in 1989 yielded five dagger nematodes (Xiphinema americanum Cobb) per g of soil, confirming the potential for virus spread by nematodes (1). TRSV reportedly infects Vitis vinifera L. but not V. labrusca L. (1). ‘Marquis’ and ‘Vanessa’ have V. vinifera heritage. The detection of TRSV has led to the establishment of a program for the production of virus-tested table grape planting stock, as well as research on the utility of nematode-resistant rootstocks for growing table grapes at the infested site.

Reference: (1) R. C. Pearson and A. C. Goheen, eds. Compendium of Grape Diseases, The American Phytopathological Society, St. Paul, MN, 1995.
First Report of Banana mild mosaic virus Isolated from Plantains (Musa AAB) in Colombia
Authors: Reichel H. , Martínez A. K. , Arroyave J. A. , Sedano R. , Morales F. J. , Duterme O. , Kummert J. , Lepoivre P.
Published: May 2007

Plantains (Musa AAB) are important sources of food and income for millions of people in Colombia and other developing countries. Colombia is the largest producer of plantains (2) and the third largest exporter of bananas in the world. In 2001, plants of ‘Dominico-Hartón’ plantain showing mild chlorotic streak symptoms were observed in northwestern Colombia. Electron microscopy of symptomatic tissue extracts revealed the presence of filamentous virus-like particles approximately 800 nm long. Immunocapture reverse-transcription polymerase chain reaction was performed to test for the presence of Banana mild mosaic virus (BanMMV) as described by J. E. Thomas (unpublished, Queensland Department of Primary Industries, Australia) and Sharman et al. (3). For polymerase chain reaction (PCR), the upstream primer No. 193 (5′-CAC TTA GGT TTG TGT GAT GT-3′) (designed in this study by using the computer Program DNAMAN Version 4.13) and the downstream primer Poty1 (5′-GGA TCC CGG GTT TTT TTT TTT TTT TTT V-3′) (1,3; J. E. Thomas, unpublished, Queensland Department of Primary Industries, Australia) were used. Amplification products of the expected size (approximately 900 bp) were obtained and sequenced after cloning in a pCR2.1 plasmid vector. Analyses of nucleic acid sequences using the international sequence databases and the BLAST program yielded nucleotide and amino acid sequence similarities of 80 to 83% and 90 to 92%, respectively, with an Australian isolate of BanMMV (GenBank Accession No. AF314662). The coat protein (CP) gene of the Colombian BanMMV isolate consists of 717 nucleotides. When the CP of the Colombian BanMMV isolates (GenBank Accession Nos. AY319331, AY319332, and AY319333) was compared with the CP of the Australian isolate, a highly variable region was observed in the N-terminus region. To our knowledge, this is the first report of BanMMV isolated from plantains in Colombia and the presence of molecular variability in the CP of BanMMV isolates. BanMMV has been found in Colombia associated with Banana streak virus and Cucumber mosaic virus in plantain.

References: (1) A. Gibbs and A. Mackenzie. J. Virol.Methods 63:9, 1997 (2) N. S. Price. Infomusa 8(2):26, 1999. (3) M. Sharman et al. J. Virol. Methods 89:75, 2000.
Characterization of Penicillium Isolates Associated with Blue Mold on Apple in Uruguay
Authors: Pianzzola M. J. , Moscatelli M. , Vero S.
Published: May 2007

Blue mold caused by Penicillium spp. is the most important postharvest disease of apple in Uruguay. Fourteen isolates of Penicillium were recovered from rotten apple and pear fruit with blue mold symptoms, and from water from flotation tanks in commercial apple juice facilities. Phenotypic identification to species level was performed, and the isolates were tested for sensitivity to commonly used postharvest fungicides. Genetic characterization of the isolates was performed with restriction fragment length polymorphism of the region including the internal transcribed spacer (ITS) ITS1 and ITS2 and the 5.8SrRNA gene (ITS1-5.8SrRNA gene-ITS2) ribosomal DNA region and with random amplified polymorphic DNA (RAPD) primers. Both techniques were able to differentiate these isolates at the species level. RAPD analysis proved to be an objective, rapid, and reliable tool to identify Penicillium spp. involved in blue mold of apple. In all, 11 isolates were identified as Penicillium expansum and 3 as P. solitum. This is the first report of P. solitum as an apple pathogen in Uruguay.
Soilborne Oospores of Phytophthora infestans in Central Mexico Survive Winter Fallow and Infect Potato Plants in the Field
Authors: Fernández-Pavía S. P. , Grünwald N. J. , Díaz-Valasis M. , Cadena-Hinojosa M. , Fry W. E.
Published: May 2007

Survival and infectivity of oospores in soils naturally infested with P. infestans oospores were studied in central Mexico. Sporangia were selectively eliminated from soil samples to determine infectivity attributable to the presence of oospores. Selective elimination of sporangia was achieved by two cycles of wetting and drying the soil. Oospore concentration, viability, and infectivity varied among soils collected during the winter fallow in different locations of central Mexico. In some soils, oospores were infective regardless of the time at which they were collected during the winter fallow. However, oospore viability and infectivity decreased following 2 years of intercropping. The number of stem lesions and initial disease severity were significantly higher in soils with moderate (20 to 39 oospores g-1 soil) oospore infestation compared with soils with low (0 to 19 oospores g-1 soil) infestation. Our study confirms that oospores can survive winter fallow and serve as a source of primary inoculum in the central highlands of Mexico. Oospore survival appeared lower in the Toluca Valley soil, which may be an indication of soil suppressiveness.
Comparison of Detection Methods for a Novel Tobamovirus Isolated from Florida Hibiscus
Authors: Kamenova Ivanka , Adkins Scott
Published: May 2007

A novel tobamovirus recently was isolated from hibiscus in Florida. Serological and molecular methods, including enzyme-linked immunosorbent assay (ELISA), dot-blot immunoassay (DBIA), tissue-blot immunoassay (TBIA), and immunocapture reverse-transcription poly-merase chain reaction (IC-RT-PCR) were compared to evaluate their usefulness for diagnosis of this virus. Each method was tested with partially purified virus preparations and tissue samples from infected hibiscus and Chenopodium quinoa plants. Indirect ELISA was more sensitive than double-antibody sandwich (DAS)-ELISA with all samples tested. The Florida hibiscus virus was detectable in hibiscus leaves and bark up to 1:12,800 and 1:6,400 dilutions, respectively, by indirect ELISA and up to 1:3,200 and 1:400 dilutions by DAS-ELISA. End-point dilutions of partially purified virus preparations from indirect and DAS-ELISA were 4 and 31 ng/ml, respectively. Florida hibiscus virus was detected by DBIA in sap from hibiscus bark and leaves at dilutions up to 1:400 and 1:800, respectively, showing that DBIA was less sensitive than either ELISA method. The virus also was detected reliably by TBIA from leaves and bark of hibiscus plants. The most sensitive method was IC-RT-PCR, which could detect as little as 500 pg/ml of virus in partially purified preparations and was 16- and 32-fold more sensitive than DAS-ELISA with hibiscus bark and leaf extracts, respectively. Over 600 hibiscus samples were tested by various combinations of these methods to validate their usefulness.
First Report of Melampsora larici-populina on Populus spp. in Eastern North America
Authors: Innes L. , Marchand L. , Frey P. , Bourassa M. , Hamelin R. C.
Published: May 2007

In September 2002, yellow spots were observed on the leaf surface of a hybrid poplar (Populus maximowiczii Henry × P. balsamifera L.) grown at the Berthier forest nursery (46°2′N, 73°11′W) in the St. Lawrence Valley (Lanaudière Region, Québec, Canada). Disease severity was low, but the pathogen was present on a hybrid that was previously thought to be resistant to Melampsora medusae Thuem, the only reported poplar rust in eastern North America. Uredinia typical of a Melampsora sp. were observed on the abaxial leaf surface. The observed urediniospores were longer (32 to 48 μm) than the expected range for M. medusae (23 to 35 μm) and possessed an apical bald spot; thick paraphyses were also observed. These characteristics are diagnostic of M. larici-populina Kleb (2). Samples were deposited in the National Mycological Herbarium of Canada (DAOM 232107 and 232108) and in the Quebec Forest Biology Herbarium (QFB14703 and 14704). DNA was extracted from uredinia, and the internal transcribed spacer (ITS) of the ribosomal RNA gene was amplified and sequenced (GenBank Accession Nos. AY429656 and AY429657). There was a 100% match between the two sequences obtained and that of M. larici-populina (GenBank Accession No. AY375267), but there was approximately 12% divergence with the ITS sequence of M. medusae (GenBank Accession No. AY375273-5). This is the first report of M. larici-populina in eastern North America. This fungus was reported on P. trichocarpa × P. deltoides hybrids in the western United States in the early 1990s (1). It appears that M. larici-populina can overwinter in Québec because it was observed again at the nursery in September 2003. The occurrence of M. larici-populina in eastern North America has direct implications for the poplar industry since the host specificities of M. medusae and M. larici-populina differ; P. balsamifera and P. maximowiczii are sensitive to M. larici-populina (3). Hybrids with P. balsamifera or P. trichocarpa components may be particularly at risk.

References: (1) G. Newcombe and G. A. Chastagner. Plant Dis. 77:532, 1993. (2) J. Pinon. Eur. J. For. Pathol. 3:221, 1973. (3) J. Pinon. Silvae Genet. 41:25, 1992.
Prevalence of Botrytis spp. in Onion Seed Crops in the Columbia Basin of Washington
Authors: du Toit Lindsey J. , Derie Mike L. , Pelter Gary Q.
Published: May 2007

Of 12 onion seed lots harvested in the semi-arid Columbia Basin of Washington in 1999 or 2000, 8 were infected and 10 infested with Botrytis aclada at incidences of 1 to 10% and 2 to 26%, respectively. Twenty to forty plants were sampled from each of nine direct-seeded, biennial seed crops in April, June, and July 2001 and assayed for Botrytis spp. Six direct-seeded crops were sampled in October and November 2001 and April, June, and July 2002. One bulb-to-seed crop was sampled in April, June, and July 2002. The incidence of B. aclada increased through each season, reaching 100% in most fields by July. Infections were primarily asymptomatic, with no apparent relationship between plant infection and infection of harvested seed. B, cinerea, B. squamosa, and B. porri were detected in 16, 4, and 4% of the fields, respectively, at lower incidences than B. aclada. Harvested seed from 15 of the fields were infected with B. aclada at <1 to 28%. B, cinerea, B. porri, and B. squamosa were detected in three, three, and none of the harvested lots, respectively.
Occurrence and Relative Incidence of Viruses Infecting Soybeans in Iran
Authors: Golnaraghi A. R. , Shahraeen N. , Pourrahim R. , Farzadfar Sh. , Ghasemi A.
Published: May 2007

A survey was conducted to determine the incidence of Alfalfa mosaic virus (AlMV), Bean common mosaic virus (BCMV), Bean yellow mosaic virus (BYMV), Blackeye cowpea mosaic virus (BlCMV), Cucumber mosaic virus (CMV), Pea enation mosaic virus (PEMV), Peanut mottle virus (PeMoV), Soybean mosaic virus (SMV), Tobacco mosaic virus (TMV), Tobacco ringspot virus (TRSV), Tobacco streak virus (TSV), Tomato ringspot virus (ToRSV), and Tomato spotted wilt virus (TSWV) on soybean (Glycine max) in Iran. Totals of 3,110 random and 1,225 symptomatic leaf samples were collected during the summers of 1999 and 2000 in five provinces of Iran, where commercial soybean is grown, and tested by enzyme-linked immunosorbent assay (ELISA) using specific polyclonal antibodies. Serological diagnoses were confirmed by electron microscopy and host range studies. The highest virus incidence among the surveyed provinces was recorded in Mazandaran (18.6%), followed by Golestan (15.7%), Khuzestan (14.2%), Ardabil (13.9%), and Lorestan (13.5%). Incidence of viruses in decreasing order was SMV (13.3%), TSWV (5.4%), TRSV (4.2%), TSV (4.1%), PEMV (2.9%), BYMV (2.2%), ToRSV (2.1%), AlMV (1.3%), BCMV (0.8%), and CMV (0.6%). Additionally, 1.5% of collected leaf samples had positive reactions in ELISA with antiserum to TMV, indicating the possible infection of soybeans in Iran with a Tobamovirus that is related serologically to TMV. Of 195 leaves from plants showing soybean pod set failure syndrome (PSF) in Mazandaran and Lorestan, only 14 (7.2%) samples had viral infection. No correlation was observed between PSF and presence of the 13 viruses tested, suggesting the involvement of other viruses or factors in this syndrome. To investigate the presence of seed-borne viruses, including SMV, TRSV, ToRSV, and TSV, 7,830 soybean seeds were collected randomly at harvesting time from the major sites of soybean seed production located in Mazandaran and Golestan provinces. According to ELISA analyses of germinated seedlings, 7.1 and 8.9% of the seed samples from Golestan and Mazandaran provinces, respectively, transmitted either SMV, TRSV, ToRSV, or TSV through seed. We also showed that SMV and other seed transmissible viruses, as well as TSWV, usually are the most prevalent viruses in soybean fields in Iran. In this survey, natural occurrence of AlMV, BCMV, BlCMV, BYMV, CMV, PEMV, PeMoV, and TSWV was reported for the first time on soybeans in Iran.
Effect of Prohexadione-Calcium Dose Level on Shoot Growth and Fire Blight in Young Apple Trees
Authors: Norelli J. L. , Miller S. S.
Published: May 2007

Prohexadione-calcium suppresses both shoot growth and fire blight in apple. In young apple orchards, there are conflicting requirements to control fire blight and allow sufficient tree growth for tree establishment. Application of prohexadione-calcium to various cultivars of orchard-grown apple trees ranging in age from newly planted to fifth-leaf trees indicated that fewer high-dose (125 or 250 mg ·liter-1) applications of prohexadione-calcium provided a better balance between fire blight control and growth in young orchards than multiple low-dose (30 or 63 mg·liter-1) applications. The response of early-season shoot growth to prohexadione-calcium treatment dose was linear. However, trees that received high doses of prohexadione-calcium tended to grow more in the latter part of the season, resulting in little or no difference in total seasonal growth between trees that received a few high or multiple low doses of prohexadione-calcium. Enhancement of fire blight resistance by prohexadione-calcium was correlated with shoot growth suppression at the time of inoculation, and the resistance response to prohexadione-calcium treatment dose was linear. Fire blight management strategies that use prohexadione-calcium in young apple orchards are discussed.
Development of Pathotype-Specific SCAR Markers for Detection of Verticillium albo-atrum Isolates from Hop
Authors: Radišek Sebastjan , Jakše Jernej , Javornik Branka
Published: May 2007

Rapid polymerase chain reaction (PCR) assays were developed for the identification and detection of Verticillium albo-atrum hop pathotypes PG1 and PG2 from Slovenia. Of 17 pathotype-linked amplified fragment length polymorphism (AFLP) markers, 11 were cloned successfully and sequenced. To convert polymorphic AFLP markers into pathotype-specific sequence-characterized amplified region (SCAR) markers, 22 PG2- and 10 PG1-specific primer pairs were designed from 16 sequences. When primer specificity was tested on a wide range of Verticillium isolates, 10 PG2- and 6 PG1-specific primer pairs retained amplification specificity for V. albo-atrum Slovene hop isolates, but also amplified sequences in V. albo-atrum and V. dahliae hop isolates from different hop production areas in Europe, as well as in some isolates from other hosts. Primer combinations obtained from the AFLP-9-1 marker were specific only for V. albo-atrum PG2 isolates. The highly specific primers were used in multiplex PCR and a nested PCR to detect the V. albo-atrum PG2 pathotype in xylem tissue of hop plants. These new SCAR markers provide a valuable tool for rapid identification of V. albo-atrum PG1 and PG2 hop pathotypes.
Characterization of Leaf Rust Resistance in Hard Red Spring Wheat Cultivars
Authors: Oelke L. M. , Kolmer J. A.
Published: May 2007

Leaf rust, caused by Puccinia triticina Eriks., is the most common disease of wheat (Triticum aestivum L.) in the United States and worldwide. The objective of this study was to characterize seedling and adult plant leaf rust resistance in hard red spring wheat cultivars grown in Minnesota, North Dakota, and South Dakota, and postulate the identity of the seedling leaf rust resistance genes in the cultivars. Twenty-six cultivars, near-isogenic lines of Thatcher wheat that differ for single leaf rust resistance genes, and three wheat cultivars with known leaf rust resistance genes, were tested with 11 different isolates of leaf rust collected from the United States and Canada. The leaf rust infection types produced on seedling plants of the cultivars in greenhouse tests were compared with the infection types produced by the same isolates on the Thatcher near-isogenic lines to postulate which seedling leaf rust resistance genes were present. Seedling leaf rust resistance genes Lr1, Lr2a, Lr10, Lr16, Lr21, and Lr24 were postulated to be present in spring wheat cultivars. Seedling genes Lr3, Lr14a, and Lr23 likely were present in some cultivars but could not be clearly identified in this study. Most of the cultivars had some level of adult plant leaf rust resistance, most likely due to Lr34. Cultivars that had seedling resistance genes Lr1, Lr2a, Lr10, or Lr16 had poor to intermediate levels of leaf rust resistance in field plots. Cultivars with combinations of seedling resistance genes Lr16 and Lr24 with additional adult plant resistance were highly resistant to leaf rust.
Etiology of Bull's Eye Rot of Pear Caused by Neofabraea spp. in Oregon, Washington, and California
Authors: Henriquez Jose L. , Sugar David , Spotts Robert A.
Published: May 2007

A collection of Neofabraea isolates from pear fruit grown in Oregon, Washington, and California was screened with species-specific primers in a multiplex polymerase chain reaction (PCR). Neofabraea alba was identified most frequently in samples from Oregon and California, whereas N. perennans was found most frequently in samples from Washington. N. alba also was identified from tissue of small cankers and pruning stubs on pear trees using PCR. Bull's eye rot pathogens were isolated from fruit of nine different European pear cultivars, Asian pear, and quince. Overall, N. alba was the most prevalent species in 2001 whereas N. perennans was more prevalent in 2002. An undescribed species of Neofabraea was identified in samples from Medford, OR that corresponds to a species previously found by others using molecular methods. This information increases the known geographic distribution of this undescribed species.