bluuebunny/crossref_metadata_2025 huggingface dataset:
First Report of Soybean Rust Caused by Phakopsora pachyrhizi in the Continental United States
Authors: Schneider R. W. , Hollier C. A. , Whitam H. K. , Palm M. E. , McKemy J. M. , Hernández J. R. , Levy L. , DeVries-Paterson R.
Published: May 2007

Asian soybean rust, caused by Phakopsora pachyrhizi Sydow, has been known to occur in the eastern hemisphere for nearly a century. More recently, it was reported from Hawaii in 1994, eastern and southern Africa from 1996-1998, Nigeria in 2001, and Brazil and Paraguay in 2002. Aerobiological models suggested that urediniospores of the pathogen would be disseminated on wind currents to the continental United States in association with tropical storms if the disease became established north of the equator during hurricane season (U.S. Soybean Rust Detection and Aerobiological Modeling online publication at www.aphis.usda.gov/ppq/ ep/soybean_rust/ ). Since soybean rust was observed at approximately 5°N latitude in South America before several hurricanes impacted the continental United States in September 2004, it seems likely that the introduction was associated with at least one of these tropical storms, especially hurricane Ivan. Symptoms of the disease were first observed on soybean (Glycine max (L.) Merr.) in the continental United States on November 6, 2004 in a field near Baton Rouge, LA. Typical pustules and urediniospores on infected leaves were readily apparent when viewed with a dissecting microscope. Urediniospores were obovoid to broadly ellipsoidal, hyaline to pale yellowish brown with a minutely echinulate thin wall, and measured 18 to 37 × 15 to 24 μm. Paraphyses were cylindric to clavate and slightly thickened at the apex, colorless to pale yellowish brown, and 25–50 × 6–14 μm in size. This morphology is typical of Phakopsora pachyrhizi and P. meibomiae, a less aggressive, western hemisphere species (2). DNA was extracted from leaves containing sori using the Qiagen DNeasy Plant Mini kit. P. pachyrhizi was detected using a real-time polymerase chain reaction (PCR) protocol (1) that differentiates between P. pachyrhizi and P. meibomiae performed in a Cepheid thermocycler with appropriate positive and negative controls. The PCR master mix was modified to include OmniMix beads (Cepheid). The field diagnosis of P. pachyrhizi was confirmed officially by the USDA/APHIS on November 10, 2004, and this was followed on November 11, 2004 by a wide-ranging survey of soybean and kudzu (Pueraria sp.) in soybean production areas in southern and central Louisiana. Collections from this survey also were assayed as described above, and six soybean specimens from five sites were confirmed positive. The disease was not found on kudzu samples. To our knowledge, this is the first report of P. pachyrhizi in the continental United States. Voucher specimens have been placed in the USDA National Fungus Collection.

References: (1) R. D. Frederick et al. Phytopathology 92:217, 2002. (2) Y. Ono et al. Mycol. Res. 96:825, 1992.
First Report of Pear Decline Phytoplasmas on Pear in Serbia
Authors: Duduk B. , Ivanović M. , Obradović A. , Paltrinieri S. , Bertaccini A.
Published: May 2007

During August of 2004, pear (Pyrus communis L.) plants with typical symptoms of pear decline (PD) were observed in orchards in central Serbia. The affected plants showed premature reddening and upward rolling of leaves that often showed down-turned petioles. In some cases, premature defoliation was observed. Although a similar decline of pear was observed earlier, until now, the causal agent had not been identified. DNA was extracted with a chloroform/phenol procedure from fresh leaf midribs and branch phloem scrapes of four symptomatic and one asymptomatic pear plants separately. A nested polymerase chain reaction assay (PCR) was used for phytoplasma detection (first PCR round with P1/P7 (4) phytoplasma universal primer pair, followed by nested PCR with group 16SrX specific primers f01/r01) (3). With these primers, the expected products from phloem scrapes and midrib extracts of symptomatic plant samples were obtained. Restriction fragment length polymorphism (RFLP) analyses of the f01/r01 amplicon, with RsaI and SspI restriction enzymes, discriminating among 16SrX subgroup phytoplasmas, showed profiles corresponding to those of the apple proliferation phytoplasma group, 16SrX-C subgroup, “Candidatus Phytoplasma pyri” (2). A 1,155-bp sequence of 16S rDNA gene for one of the PA2f/r (1) amplicons obtained in nested PCR on P1/P7 products from one of the leaf midrib samples was deposited in GenBank (Accession No. AY949984); both strands of the fragment were sequenced with the Big Dye Terminator reaction kit (Applied Biosystems, Foster City, CA). The sequences were analyzed with the Chromas 1.55 DNA sequencing software (Technelysium, Queensland, Australia) and aligned with BLAST software ( http://www.ncbi.nlm.nih.gov ). The blast search showed 100% homology of this sequence with that of PD strain Y16392, confirming the identity with PD of the phytoplasma detected. To our knowledge, this is the first report of pear decline phytoplasmas in Serbia.

References: (1) M. Heinrich et al. Plant Mol. Biol. Rep. 19:169, 2001. (2) IRPCM Phytoplasma/Spiroplasma Working Team-Phytoplasma Taxonomy Group. Int. J. Syst. Evol. Microbiol. 54:1243, 2004. (3) K.-H. Lorenz et al. Phytopathology 85:771, 1995. (4) Schneider et al. Pages 369–380 in: Molecular and Diagnostic Procedures in Mycoplasmology. Vol I. S. Razin and J. G. Tully, eds. The American Phytopathological Society, 1995.
New Genes for Leaf Rust Resistance in CIMMYT Durum Wheats
Authors: Herrera-Foessel S. A. , Singh R. P. , Huerta-Espino J. , Yuen J. , Djurle A.
Published: May 2007

Leaf rust, caused by Puccinia triticina, has become an important disease of durum wheat (Triticum turgidum) in Mexico since the detection in 2001 of BBG/BN, a new race virulent on all common cultivars and on more than 80% of CIMMYT's durum wheat collection. We investigated the genetic basis and diversity of resistance in nine durum genotypes that are highly resistant to the new race. These resistant durums were crossed with the susceptible cv. Atil C2000 and intercrossed in a half diallel arrangement. Five diverse sources of resistance were identified by evaluating parents, F1, F2, and F3 populations in greenhouse and/or field trials under artificial epidemics of race BBG/BN. The same pair of partially dominant complementary genes determined resistance in Jupare C2001, Hualita, and Pohowera. Somateria and Llareta INIA shared the same dominant resistance gene, whereas a partially dominant gene conferred resistance in two sister lines, Guayacan 2 and Guayacan INIA. A different partially dominant gene present in Storlom was linked in repulsion to another partially dominant gene in Camayo. These diverse resistance genes can be used effectively to control leaf rust, preferably by deploying them in combinations.
The Window of Risk for Emigration ofWheat streak mosaic virusVaries with Host Eradication Method
Authors: Jiang W. , Garrett K. A. , Peterson D. E. , Harvey T. L. , Bowden R. L. , Fang L.
Published: May 2007

The wheat curl mite (WCM), Aceria tosichella, the vector of Wheat streak mosaic virus (WSMV), often survives the summer on volunteer wheat (Triticum aestivum) and may disperse from this “green bridge” in fall to newly planted winter wheat. Because some methods for managing volunteer wheat do not directly kill WCM, there is a window of risk for WCM and WSMV emigration after management has been applied. WCM survival in response to treatment of wheat by glyphosate, paraquat, stem cutting, and withholding water was measured in greenhouse experiments to determine how this window of risk for emigration varies with management. WCM populations on plants treated with paraquat or stem cutting decreased from the beginning of the sampling period. WCM populations on plants treated with glyphosate or that received no water increased up to 3 days after application and then decreased by 10 days after application. If glyphosate is used to manage volunteer wheat infested with WCM, it should be applied well before wheat is planted in fall. WCM in declining populations tended to be in an upright posture that could facilitate emigration via wind. The total green leaf area was strongly correlated with the number of WCM for treated plants and could be used in the field to predict the posttreatment survival of mites that pose a risk of emigration.
Association of a Virus with Wheat Displaying Yellow Head Disease Symptoms in the Great Plains
Authors: Seifers Dallas L. , Harvey Tom L. , Martin T. J. , Haber Steve , She Y.-M. , Ens Werner , Standing Kenneth G. , Salomon Raffi , Gera A.
Published: May 2007

Wheat with yellow head disease (YHD) (yellow heads and mosaic leaf symptoms) has been observed in Kansas since 1997. A pathogen was transmitted from the infected wheat to maize by vascular puncture inoculation and to Nicotiana benthamiana by rub inoculation. The original infected wheat and infected maize and N. benthamiana test plants all produced a unique 32- to 34-kDa protein when analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Time-of-flight mass spectrometry analysis of the unique 32- to 34-kDa protein showed that the amino acid sequence was most closely related to the nucleoprotein of Rice hoja blanca virus, indicating that the virus causing YHD symptoms in wheat is a tenuivirus. Antiserum made to this protein failed to react with extracts made from healthy wheat or wheat infected with Wheat streak mosaic virus or the High Plains virus. The antiserum did react to extracts made from symptomatic wheat, maize, and N. benthamiana, shown by SDS-PAGE to contain the unique protein, and to extracts of wheat with YHD symptoms from Kansas, North Dakota, South Dakota, and Oklahoma. The name Wheat yellow head virus is proposed for this virus.
Transmissibility of Citrus leprosis virus by Brevipalpus phoenicis to Solanum violaefolium
Authors: Rodrigues J. C. V. , Locali E. C. , Freitas-Astua J. , Kitajima E. W.
Published: May 2007

Citrus leprosis virus (CiLV) constitutes one of the most important viruses in citrus in the areas where it occurs. Two morphological types of virus particles have been described from associated leprosis symptoms, nuclear (CiLV-N) and cytoplasmic (CiLV-C) (4). The CiLV-C is more common, representing more than 99% of samples collected from South and Central America (E. W. Kitajima and J. C. V. Rodrigues, unpublished). Both virus types are associated with the mite vector, Brevipalpus phoenicis (Geijskes) (Acari: Tenuipalpidae). So far, CiLV-C has only been naturally transmitted by these mites to citrus (3). Plants of Solanum violaefolium Schott (Solanaceae) and ornamental and sweet orange seedlings were infested with viruliferous adult female mites, colony no. 61 (GenBank Accession No. AY320027) that were previously maintained on citrus seedlings infected with CiLV-C according to Rodrigues et al. (3). Fifteen days after the mites were transferred, spotted yellowish symptoms were observed on leaves of plants of S. violaefolium and similar symptoms were observed after 25 days on citrus leaves. The symptomatic tissues were studied using transmission electron microscopy. Particles typical of CiLV-C were observed in samples from both plant species. To our knowledge, this is the first reported case of mites transmitting CiLV-C to a noncitrus host. Subsequent experiments showed that mites were able to transmit the virus between plants of S. violaefolium. Attempts to transmit the virus by mites from S. violaefolium to citrus were unsuccessful. The dsRNA viral electrophoresis profile showed differences between the two host plants. Reverse transcription-polymerase chain reaction (RT-PCR) and sequencing assays with primers designed to detect CiLV-C (2) amplified DNA fragments of the expected size and base composition. These data suggest the loss or alteration of some viral components from the Solanum sp. host that might be essential for the transmission or infection in citrus. Such a mechanism may explain why, despite the ever-increasing number of Brevipalpus-transmitted viruses in a large number of different host plant species (1), cross transmission is not common. This information shows one of the potential routes for CiLV to invade citrus orchards, and suggests one alternative host plant that allows rapid multiplication of the virus for characterization.

References: (1) E. W. Kitajima et al. Exp. Appl. Acarol. 30:135, 2003. (2) E. C. Locali et al. Plant Dis. 87:1317, 2003. (3) J. C. V. Rodrigues et al. Proc. Int. Org. Citrus Virol. 174, 2000 (4) J. C. V. Rodrigues et al. Exp. Appl. Acarol. 30:161, 2003.
Partial Characterization of a Carla-Like Virus Infecting Yam (Dioscorea spp.) from China
Authors: Lebas B. S. M. , Ochoa-Corona F. M. , Elliott D. R. , Tang Z. , Alexander B. J. R.
Published: May 2007

Dioscorea opposita (yam) from China was tested for viruses during post-entry quarantine in New Zealand during 2004. No obvious symptoms or virus particles were observed from yam. Mechanically inoculated Nicotiana occidentalis cvs. 37B and P1 produced systemic chlorosis, leaf reduction, and stunting, whereas no symptoms were observed on other tested herbaceous plants (Chenopodium amaranticolor, C. quinoa, Cucumis sativum, Gomphrena globosa, N. benthamiana, N. clevelandii, N. glutinosa, N. sylvestris, and N. tabacum cv. White Burley). Numerous filamentous particles (approximately 600 nm long) were observed by using electron microscopy from symptomatic N. occidentalis. Total RNA was extracted from yam and symptomatic N. occidentalis leaf samples using the Qiagen Plant RNeasy kit (Qiagen, Valencia, CA). Reverse transcription (RT) was carried out using random hexamer primers and SuperScript II RNase H¯ reverse transcriptase (Invitrogen, Carlsbad, CA) followed by polymerase chain reaction (PCR) with different primer pairs. Samples tested negative for Chinese yam necrotic mosaic virus (ChYNMV; genus Macluravirus) with specific primers (supplied by T. Kondo, Aomori Green BioCenter, Aomori, Japan). Negative results were also obtained for the genera Potyvirus, Potexvirus, Capillovirus, Trichovirus, and Foveavirus using RT-PCR with broad detection primers (1,2,4). A positive RT-PCR amplification was obtained from the yam and N. occidentalis samples with universal primers for the genus Carlavirus (Agdia Inc., Elkhart, IN). The 275-bp amplified products from the viral replicase were cloned and sequenced. The yam virus shows a high amino acid similarity with Hop latent virus (87.9%), Aconitum latent virus (86.8%) and Potato virus M (86.8%). Filamentous virus particles belonging to the genera Macluravirus, Potyvirus, and Potexvirus have been reported in yam (3). These virus species are not associated with the carlavirus infection since the virus found in D. opposita tested negative using RT-PCR with primers for these genera. There are no carlaviruses reported to be infecting yams, therefore, it may be considered as a new host-virus association.

References: (1) X. Foissac et al. Acta Hortic. 550:37, 2001. (2) S. A. Langeveld et al. J. Gen. Virol. 72:1531, 1991. (3) B. S. M. Lebas. Ph.D. thesis. Greenwich University, Chatham Maritime, UK, 2002. (4) R. A. A. Van der vlugt and M. Berendsen. Eur. J. Plant Pathol. 108:367, 2002.
First Report of Cucumber mosaic virus in Banana from Iran
Authors: Ghotbi T. , Bananej K.
Published: May 2007

Banana bunchy top virus (BBTV), Banana streak virus (BSV), and Cucumber mosaic virus (CMV) (genus Cucumovirus, family Bromoviridae [2]) cause widespread economic losses on banana (Musa sp.) throughout the world and have been reported on banana in different countries including Pakistan along its southeastern border with Iran (1). A survey was conducted from 2004–2005 to identify viruses infecting banana in greenhouses in different growing areas in northern Iran, Mazandaran Province (Sari, Babol, Behshahr, and Ghaemshahr cities). A total of 180 samples from seven banana-growing greenhouses with symptoms of mosaic, chlorosis, stunting, and fruit malformation were collected. All samples were tested for CMV with polyclonal antibodies using double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) (CMV strain D subgroup I; gifted by H. Lecoq, INRA, Avignion, France). For sap inoculation onto indicator test plants, selected ELISA-positive leaf samples were ground in chilled 0.01 M phosphate buffer, pH 7.0, containing 0.15% 2-mercaptoethanol. Chlorotic and necrotic local lesions developed on Chenopodium amaranticolor and Vigna unguiculata (cv. Mashad local) 10 and 12 days postinoculation, respectively. Cucumis sativus and Nicotiana rustica also developed systemic mosaic symptoms (3). All indicator test plants were rechecked for the presence of CMV using DAS-ELISA. On the basis of serological tests and indicator host plants reactions, CMV was identified in 32% of samples including Sari (13.8%), Babol (2.7%), Behshahr (10%) and Ghahemshahr (5%), respectively. Fifty-five samples did not react with CMV antiserum but the presence of symptoms resembling BBTV and BSV (4) emphasizes the need for further investigations to confirm the presence and identities of other viruses.

References: (1) J. Bird and F. L. Wellman. Phytopathology 52:286, 1962. (2) S. K. Choi et al. J. Virol. Methods 83:67, 1999. (3) A. J. Gibbs and B. D. Harrison. Descriptions of Plant Viruses. No.1. CMI/AAB, Surrey, England, 1970. (4) R. C. Ploetz et al., eds. Compendium of Tropical Fruit Diseases. The American Phytopathological Society, St. Paul, MN, 1994.
The Relationship Between Aphis glycines and Soybean mosaic virus Incidence in Different Pest Management Systems
Authors: Burrows M. E. Lee , Boerboom C. M. , Gaska J. M. , Grau C. R.
Published: May 2007

The soybean aphid, Aphis glycines, causes yield loss and transmits viruses such as Soybean mosaic virus (SMV) in soybean (Glycine max). Field experiments were designed to monitor the landing rate of A. glycines and transmission of SMV to soybean grown in six crop management environments. Management systems evaluated were the application of postemergence insecticide or no insecticide, and within each insecticide treatment no herbicide, glyphosate, or imazamox application. In 2001, early-season incidence of SMV was 2%, which increased to 80% within 18 days after the beginning of the A. glycines flight. In 2002, the incidence of SMV was 1% prior to the arrival of A. glycines, and increased to 44% within 21 days. The landing rate of A. glycines was fivefold higher in 2001 than in 2002. The incidence of SMV was lower in insecticide-treated plots in 2002, but no effect of insecticide was seen in 2001. Imazamox slowed the progression of SMV incidence, but the final incidence of SMV-infected plants was the same. Glyphosate had no consistent effect on SMV incidence. Yield was higher in the insecticide-treated plots in 2002, but not 2001. Insecticide and herbicide application had no substantial effects on seed quality.
First Report of Stem Spots Caused by Alternaria sp. on Berberis sp. in Iran
Authors: Mirabadi S. , Soumi F. , Golnaraghi A. R. , Rezaee S.
Published: May 2007

During the summer of 2004, approximately 150 Berberis sp. (Berberis thunbergii cv. Rose Glow) showing dark brown, eye-like elongated spots (7 to 22 mm long and 1 to 3 mm wide) on stems near the crown toward the top were observed in a park in Tehran, the capital of Iran. Red and yellow spots on the leaves and defoliation were also recorded for some of the affected plants. A total of 28 samples from 16 individual plants (sampling included all symptomatic parts of the plants) were collected and evaluated for the possible casual agent of the disease. Fungi with spores that are characteristic of the genus Alternaria (2), including dark mycelium and brief and simple conidiophores with catenulate dictyospores, were isolated from the detached leaf and stem pieces of diseased plants. The pathogenicity of five isolates was investigated using Koch's postulate. Twenty cut stems and 10 rooted plants of Berberis sp., with or without wounding on their stems and leaves, were inoculated with the spore suspension (104 spores per ml) prepared by using 10-day-old cultures of the isolates grown on potato dextrose agar at 25°C in the dark. The inoculated cut stems were covered for 3 days with a plastic tent and kept in a greenhouse at 25 ± 5°C with more than 12 h of light. These covers were not used for the rooted plants that were inoculated under field conditions. For each test, at least two controls were used. Symptoms similar to those observed in the field appeared on inoculated stems in 6 to 7 days. On leaves, dark, reddish brown spots (different from the field observations) were induced 3 to 4 days after inoculation. The disease on leaves, which eventually led to defoliation, was more severe than that observed in the field. Stem spots occurred on covered and uncovered inoculated plants; however, the lesions on the covered plants were deeper than those on the uncovered plants. Both types of plants died 3 to 4 weeks after inoculation. Although the fungi were isolated from diseased plants from one park, similar symptoms also were observed on Berberis sp. planted in other parks and streets, etc. The genus Alternaria (Deuteromycetes) caused leaf and stem spot diseases on different plant hosts (1). To our knowledge, this is the first report of a natural occurrence of Alternaria sp. on Berberis sp. in Iran.

References: (1) G. N. Agrios. Plant Pathology, 4th ed., Academic Press, NY, 1997. (2) M. B. Ellis. More Dematiaceous Hyphomycetes. Commonwealth Mycological Institute, Kew, England, 1976.
Occurrence of Sclerotinia Stem Rot of Osteospermum sp., Felicia amelloides, and Ranunculus asiaticus in Argentina
Authors: Wright E. R. , Rivera M. C. , Chiesa G. , Morisigue D.
Published: May 2007

Three ornamental species, Osteospermum sp. (L.), Felicia amelloides (L.) Voss, and Ranunculus asiaticus L., cultivated in greenhouses on the outskirts of Buenos Aires, showed sudden wilt and death during October 2002. These species are new ornamentals in Argentina. The diseased plants were cultivated in plastic containers filled with commercial potting mix. Soft rot was observed at the base of the plants. Stem lesions became covered with whitish mycelium that produced large, black sclerotia (5 to 7 mm in diameter) characteristic of Sclerotinia sclerotiorum (Lib.) de Bary (1). The fungus was consistently recovered from infected stem pieces that were disinfested for 1 min in 0.2% NaOCl and plated on potato dextrose agar (PDA), pH 7. Pathogenicity of the three isolates obtained from infected plants was confirmed by inoculating 10 3-month-old healthy plants of each species in 14-cm-diameter plastic pots. Each isolate was inoculated on the host from which it had been isolated. Inoculum consisted of three mycelial plugs from 7-day-old PDA cultures that were placed on the substrate at the base of the plants. Control plants were treated with sterile agar plugs. Inoculated and noninoculated plants were covered with transparent plastic bags for 2 days and incubated in a growth chamber at 20 to 24°C with a 12-h photoperiod. All inoculated plants developed symptoms of leaf yellowing and wilt. Soft and watery tissues were observed at the base of the plants, soon followed by the appearance of white mycelium. Disease symptoms were similar to those observed on the original infected plants and appeared 6, 5, and 3 days after inoculation on Osteospermum sp., F. amelloides, and R. asiaticus, respectively. All inoculated plants died within 3 weeks, and control plants remained healthy. S. sclerotiorum was reisolated from inoculated plants of each species, fulfilling Koch's postulates. To our knowledge, this is the first report of the occurrence of Sclerotinia stem rot on these three plant species in Argentina.

Reference: (1) J. E. M. Mordue and P. Holliday. No. 513 in: Descriptions of Pathogenic Fungi and Bacteria. CMI, Kew, Surrey, UK. 1976.
First Report of the East-Asian Type of Bursaphelenchus mucronatus in Pinus sylvestris in Slovenia
Authors: Urek G. , Širca S.
Published: May 2007

Bursaphelenchus mucronatus Mamiya & Enda, a nematode associated with aboveground tissues of pine trees, is very similar morphologically to the pine wood nematode (PWN), B. xylophilus, a devastating pest that has caused widespread losses to pine woods in some parts of Asia since the early 1900s. During 1999, B. xylophilus was identified for the first time in Europe in Portugal (3), leading to concern that pines and other conifers all over Europe might be endangered. To protect forests from PWN and other pests, the European Union and other countries now regulate the importation of all coniferous chips, sawn wood, and logs and also have organized surveys to determine the extend of PWN infestation. Slovenia has approximately 1,227,832 ha of forest that makes up more than 60% of the surface of the country. The percentage of conifers within forests is 47.9% and comprised mainly of Picea, Pinus, Abies, and Larix species (2). During the summers of 2002-2004, approximately 100 ha of conifer forests in Slovenia were surveyed for the presence of PWN. In total, 170 wood samples from dead and dying pine (Pinus sylvestris L., P. nigra Arnold), spruce (Picea abies L.), and fir (Abies alba Miller) were analyzed. B. xylophilus (Steiner & Buhrer) Nickle was not found in the area, but a closely related nematode, B. mucronatus, previously shown to be pathogenic on conifer seedlings (4), was isolated from samples of P. sylvestris. Of 34 P. sylvestris samples analyzed, B. mucronatus was found in three samples. Samples were taken from a conifer forest located in the central part of Slovenia near the international airport of Ljubljana. The species was identified morphologically and also characterized by polymerase chain reaction restriction (PCR)-fragment length polymorphism (RFLP) analysis on the basis of ITS-rDNA fragment patterns. According to RFLP patterns (1), the analyzed species was recognized as the East-Asian type of B. mucronatus. Beside these findings, the specimens of B. homanni (Braasch) and Bursaphelenchus sp. have also been found in Slovenia. The results of the survey show that PWN was not found in Slovenia, but three different species of the Bursaphelenchus genus were present.

References: (1) H. Braasch et al. Nachrbl. Dtsch. Pflanzenschutzd. 51:312, 1999. (2) M. Jurc et al. Zb. Gozdarstva in Lesarstva 72:121, 2004. (3) M. M. Mota et al. Nematology 1:727, 1999. (4) J. R. Sutherland. Pine wilt nematode. Pages 19–20 in: Compendium of Conifer Diseases. E. M. Hansen and K. J. Lewis, eds. The American Phytopathological Society, St. Paul, MN. 1997.
Influence of Plant Age on Symptom Development in Ulmus minor Following Inoculation by Ophiostoma novo-ulmi
Authors: Solla A. , Martín J. A. , Ouellette G. B. , Gil L.
Published: May 2007

In American and European breeding programs, numerous elm trees from many species (Ulmus spp.) and hybrids have been inoculated annually with the fungus Ophiostoma novo-ulmi (the Dutch elm disease pathogen) in screening tests for resistance. Because trees were inoculated at different ages, it appeared necessary to study the influence of host age on the symptoms shown. Four Ulmus minor trees and one U. minor × U. pumila tree were cloned annually from 1994 to 1999. The replicates obtained (usually n = 6) were inoculated on 17 May 2000 with an O. novoulmi strain. At the end of the season, 2-year-old U. minor trees showed average wilting of 8 ± 3% (ES), significantly less than that of 3-year-old trees (34 ± 5%) (P ≤ 0.01). Elms that were 4, 5, 6, and 7 years old showed wilting values of around 50%. A positive relationship between the symptoms shown and the diameter of the elm xylem vessels was observed, and the implications for elm resistance and breeding are discussed. Breeders and pathologists should use trees of the same age and physiological phase when determining the relative resistance among elm clones. It is concluded that under the growing conditions of this experiment, the optimal age for U. minor screening was 4-year-old plants.
Seed Transmission of Wheat streak mosaic virus Shown Unequivocally in Wheat
Authors: Jones Roger A. C. , Coutts Brenda A. , Mackie Alison E. , Dwyer Geoffrey I.
Published: May 2007

Under conditions that excluded any possibility of eriophyid mite vector activity, seed transmission of Wheat streak mosaic virus (WSMV) was shown in eight different wheat genotypes at rates of 0.5 to 1.5%. Virus identification in seedlings came from characteristic symptoms in wheat, enzyme-linked immunosorbent assay with WSMV-specific antibodies, reverse-transcription polymerase chain reaction tests with WSMV-specific primers, and cDNA sequence comparisons with published sequences. Sequence comparisons of four seedborne isolates showed ≥98.6% identity with the eight Australian isolates in GenBank, indicating a common seedborne origin of WSMV. These findings warrant reconsideration of currently accepted views on WSMV epidemiology and the likelihood of introducing it to new locations through planting untested wheat seed and the movement of germplasm.
Characterization of Cylindrocarpon Species, the Cause of Black Foot Disease of Grapevine in California
Authors: Petit Elsa , Gubler Walter Douglas
Published: May 2007

This study investigated phylogenetic divergence, morphological difference, and pathogenic variation among Cylindrocarpon species isolates associated with black foot disease of grapevine (Vitis sp.) in California. To assess phylogenetic divergence, we sequenced the internal transcribed spacer (ITS) of the nuclear ribosomal DNA (rDNA), partial beta-tubulin (BT) gene introns and exons, and the small subunit mitochondrial rDNA. Isolates associated with black foot disease belonged to two paraphyletic species, Cylindrocarpon destructans and C. macrodidymum. The morphology of these isolates was in agreement with published descriptions of both species. We found that C. macrodidymum isolates were reliably distinguishable from C. destructans isolates in culture by a unique orange-dark brown colony color on 2% malt extract agar and genetically by a species-specific 52-bp DNA insertion in the BT region. Selected isolates of each species inoculated onto grapevine rootstock 5C caused typical black foot disease symptoms. This is the first report of C. macrodidymum in California.
Biovar of Ralstonia solanacearum Causing Bacterial Wilt of Tomato in Nigeria
Authors: Adebayo O. S. , Ekpo E. J. A.
Published: May 2007

A survey of southwestern Nigeria showed an outbreak of wilt disease caused by Ralstonia solanacearum in 80% of tomato (Lycopersicon lycopersicum) fields in the production area of Ogun State (7°15′N, 3°25′E) in June 1996. Subsequent surveys conducted in Edo (6°45′N, 5°30′E), Delta (5°15′N, 5°45′E), Lagos (6°30′N, 3°40′E), Oyo (8°40′N, 3°30′E), and Osun (7°50′N, 4°E) states between May and November 1998 identified 60 to 80% infected fields per state. Observations made at the experimental plots of the National Horticultural Research Institute (NIHORT) at Ibadan (7°23′N, 2°50′E) also showed similar infections. Affected plants exhibited initial wilting of terminal leaves followed (within 2 days) by sudden and permanent wilt. For further identification of the causal organism, 10 tomato plants showing wilt symptoms were collected from each of five fields in the vegetable blocks of the NIHORT at Ibadan and 20 farmers' fields in Ogun State. The 10 plants per field were thereafter bulked as one composite sample. Creamy bacterial sap from these samples was plated on tetrazolium chloride media, and plates were incubated at 30°C for 48 h (2). Colonies that were fluidal and white with pink centers were used for biovar determination. Basal media was prepared to include one of three disaccharides (cellobiose, lactose, or maltose) or three hexose alcohols (dulcitol, mannitol, or sorbitol). A loopful of bacterial cells of all 25 isolates was inoculated individually to each of the six media. Cultures were incubated at 30°C for 28 days and monitored daily for color changes. The pathogenicity of the 25 isolates was tested using 10 4-week-old seedlings each of eggplant cv. black beauty, tomato cv. Ibadan local, sweet pepper cv. California wonder, and potato cv. Kufri. Each inoculum was prepared by adjusting the concentration to 107 CFU/ml with a colorimeter at a wavelength of 600 nm (optical density of approximately 0.3). Plants were inoculated by pouring 10 ml of inoculum around the base of each plant. Ten uninoculated seedlings of each cultivar served as the control. Plants were assessed for wilt severity 30 days after inoculation. All isolates utilized the three disaccharides and three hexose alcohols, and according to Hayward's classification, all isolates were biovar 3 (1). Furthermore, the isolates caused rapid wilting of all four test plants. R. solanacearum was easily reisolated from the vascular bundles of the test plants. To our knowledge, this is the first report of this biovar of R. solanacearum affecting tomato crops in Nigeria.

References: (1) A. C. Hayward. J. Appl. Bacteriol, 27:265, 1964 (2) A. Kelman. Phytopathology 44:693, 1954.
First Report of Fusarium Wilt of Cilantro Caused by Fusarium oxysporum in California
Authors: Koike S. T. , Gordon T. R.
Published: May 2007

Cilantro, or coriander (Coriandrum sativum), is a leafy vegetable in the Apiaceae and is grown commercially in California primarily for use as a fresh herb. During 2002 and 2003 in coastal California (Santa Barbara County), commercial cilantro fields showed symptoms of a wilt disease. Affected plants grew poorly and were stunted. Lower foliage turned yellow with reddish tinges, and plants wilted during warmer times of the day. The main stem, crown, and taproot exhibited vascular discoloration that was reddish to light brown. As disease progressed, plants eventually died. For both years, the disease distribution was limited to isolated small patches (each patch measuring less than 1 m2 in area). A fungus was consistently isolated from symptomatic vascular tissue in crowns and taproots. On the basis of colony and conidial morphology, the isolates were identified as Fusarium oxysporum (2). No other fungi or bacteria were recovered from these plants. To test pathogenicity, suspensions containing 1 × 106 conidia/ml were prepared for five isolates. The roots of 30-day-old cilantro plants of four cultivars (30 plants each of Festival, Leisure, Santo, and LSO 14) were clipped and then soaked in the suspensions for 20 min. The roots of 30 plants of each cultivar were soaked in water as a control. Plants were repotted into new redwood bark + peat moss rooting medium and maintained in a greenhouse setting at 24 to 26°C. After 1 month, 95% or more of the inoculated plants showed yellowing and vascular discoloration symptoms similar to those seen in the field. F. oxysporum was reisolated from all inoculated plants. The four cilantro cultivars did not show differences in disease severity. Control plants showed no symptoms, and the fungus was not recovered from these plants. The experiment was repeated and the results were the same. Experiments also were conducted to determine if cilantro isolates could cause disease in celery (Apium graveolens var. dulce). Celery transplants and cilantro seedlings were prepared and inoculated as described above. However, after 2 months, celery plants did not show any disease symptoms, while the cilantro developed wilt symptoms and eventually died. A Fusarium wilt disease has been reported on coriander in Argentina and India where the pathogen was named F. oxysporum f. sp. coriandrii (1,3). To our knowledge, this is the first report of Fusarium wilt of cilantro in California.

References: (1) M. Madia et al. Fitopatologia 34:155, 1999. (2) P. E. Nelson et al. Fusarium species: An Illustrated Manual for Identification. Pennsylvania State University Press, University Park, 1983. (3) U. S. Srivastava. Indian Phytopathol. 22:406, 1969.
Rust Control in Glyphosate Tolerant Wheat Following Application of the Herbicide Glyphosate
Authors: Anderson J. A. , Kolmer J. A.
Published: May 2007

In greenhouse and field trials, transgenically modified wheat (Triticum aestivum) genotypes with tolerance to glyphosate had extremely low infection types to leaf rust caused by Puccinia triticina when treated with a labeled rate of the herbicide glyphosate prior to inoculation with leaf rust. A surfactant solution and a nonglyphosate herbicide had no effect on leaf rust development on the glyphosate tolerant wheat. Glyphosate had a systemic effect in reducing leaf rust development. The leaf rust control by glyphosate decreased with reduced application rates and longer periods of time between glyphosate application and leaf rust infections. The field and greenhouse tests indicated that control of leaf rust in wheat conditioned by glyphosate is transitory and is effective for at least 21, but not more than 35, days after application. Application of glyphosate also reduced infection types on wheat caused by the stem rust fungus, Puccinia graminis f. sp. tritici. Given these results and evidence from the literature that glyphosate can have adverse effects on other pathogens, including other rust fungi, additional investigation of the fungicidal properties of glyphosate are warranted, with particular attention to the timing of glyphosate application relative to fungal infection. The effects of glyphosate on the soybean rust fungus, Phakopsora pachyrhizi, an emerging pathogen in North America, merit immediate investigation.
Suppression of Botrytis Blight of Begonia by Trichoderma hamatum 382 in Peat and Compost-Amended Potting Mixes
Authors: Horst L. E. , Locke J. , Krause C. R. , McMahon R. W. , Madden L. V. , Hoitink H. A. J.
Published: May 2007

Inoculation of an industry standard light sphagnum peat potting mix with Trichoderma hamatum 382 (T382) significantly (P = 0.05) reduced the severity of Botrytis blight, caused by Botrytis cinerea, on begonia plants grown in a greenhouse. In data combined from three experiments, the degree of control provided by T382 did not differ significantly (P = 0.05) from that provided by weekly topical sprays with chlorothalonil. In addition, T382 significantly (P = 0.05) increased shoot dry weight and salability of flowering plants. Incorporation of composted cow manure (5%, vol/vol) into the light peat mix also significantly (P = 0.05) decreased blight severity while shoot dry weight and salability were increased. Blight severity on plants in this compost mix did not differ significantly (P = 0.05) from that on those in the light peat mix inoculated with T382. Finally, T382 and chlorothalonil did not significantly (P = 0.05) affect blight severity, shoot dry weight, or salability of plants grown in the compost mix. Spatial separation was maintained in begonias between the biocontrol agent T382 and the pathogen. It was concluded, therefore, that the decrease in disease severity provided by inoculation of the peat mix with T382 most likely was due to systemic resistance induced in begonia against Botrytis blight. The suppressive effect of the compost mix against Botrytis blight was unusual because composts typically do not provide such effects unless inoculated with a biocontrol agent capable of inducing systemic resistance in plants to disease.
Accurate Assessment of Wheat and Triticale Cultivar Resistance to Septoria tritici and Stagonospora nodorum Infection by Biotin/Avidin ELISA
Authors: Tian Shimin , Wolf Gerhard A. , Weinert Joachim
Published: May 2007

Specific and quantitative biotin/avidin-enzyme-linked immunosorbent assays (BA-ELISA) were evaluated for their ability to assess resistance of wheat and triticale cultivars to Septoria tritici (leaf blotch) and Stagonospora nodorum (leaf and glume blotch) in field trials. Using BA-ELISAs, the antigen amounts of S. tritici and of Stagonospora nodorum were measured in the flag leaf (F) and the first leaf below it (F-1) of five cultivars of triticale at Zadok's growth stage (GS) 75–80 and in 11 cultivars of wheat at GS 73–75 in 2001 and 2002. The presence of the pathogens was found to be specific to parts of the plants, cultivar, and plant species. Stagonospora nodorum was the dominant leaf blotch pathogen in triticale, while both Septoria tritici and Stagonospora nodorum occurred commonly in wheat. Close correlations were obtained between the pathogen amount measured by BA-ELISA and the percentage of necrotic leaf area in the tested cultivars. The BA-ELISA values for the tested triticale and wheat cultivars were ranked, and they correlated well with the susceptibility ratings given in the cultivar list recommended by Bundessortenamt (German Federal Office of Plant Variety), which is based on visual assessment of the leaf blotch complex caused by S. tritici and Stagonospora nodorum. The relative susceptibilities of individual wheat cultivars to both pathogens were similar. In conclusion, BA-ELISA provided for an accurate diagnosis and quantification of S. tritici and Stagonospora nodorum in infected plant tissue, and therefore can be used to assess resistance to these fungi in a disease complex in both early-stage breeding lines and field trials.
Reactions of Perennial Grain Accessions to Four Major Cereal Pathogens of the Great Plains
Authors: Cox C. M. , Garrett K. A. , Cox T. S. , Bockus W. W. , Peters T.
Published: May 2007

Methods of disease management used in annual grain crops, especially cultural practices designed to disrupt the disease cycle of a particular pathogen, will not necessarily be applicable to perennial grain crops. Resistance to multiple pathogens, therefore, will clearly be important in disease management. The objective of this research was to evaluate disease resistance in 10 perennial grain accessions (one to two accessions of each: perennial wheat (Thinopyrum sp. × Triticum aestivum), intermediate wheatgrass (Thinopyrum intermedium), perennial rye (Secale montanum), hexaploid triticale (Triticum turgidum × S. montanum), octoploid triticale (Triticum aestivum × S. montanum), tetraploid perennial rye (Secale cereale × S. montanum), and tall wheat-grass (Thinopyrum ponticum)) to tan spot (caused by Pyrenophora tritici-repentis), take-all (caused by Gaeumannomyces graminis var. tritici), wheat streak mosaic, and barley yellow dwarf, four important diseases of the Great Plains. Several of the grasses were resistant to tan spot, barley yellow dwarf, and wheat streak mosaic. Indeed, the wild grasses and perennial donors T. intermedium (including BFPMC1), T. ponticum, and S. montanum, in addition to Permontra, a tetraploid perennial rye, were highly resistant to all three diseases. Additionally, the remaining grasses tested were also more resistant to tan spot than the susceptible wheat control. However, none of the 10 grass accessions appeared highly resistant to take-all, and substantial losses in biomass were observed, although such effects may be moderated under field conditions due to the potential for take-all decline in perennial plantings.
Fragaria chiloensis cryptic virus: A New Strawberry Virus Found in Fragaria chiloensis Plants from Chile
Authors: Tzanetakis I. E. , Martin R. R.
Published: May 2007

Molecular characterization of Fragaria chiloensis latent virus (FClLV) (3) was based on shotgun cloning of double-stranded RNA (dsRNA) obtained from a Chilean Fragaria chiloensis plant. While the majority of the clones acquired belonged to FClLV, several had similarities with the RNA polymerases of viruses of the family Partitiviridae. A region of more than 1 kb of the putative virus (GenBank Accession No. DQ093961) was acquired by a combination of shotgun cloning and reverse transcription-polymerase chain reaction (RT-PCR) (3) and was compared against sequences found in GenBank. The Alphacryptovirus Beet cryptic virus 3 (Genbank Accession No. S63913) and the RNA-dependent RNA polymerase encoded using dsRNA isolated from Pyrus pyrifolia (Genbank Accession No. BAA34783) produced the most significant alignments with approximately 40% amino acid sequence identity and 60% amino acid similarity with the coding region of the sequenced portion of the virus. Detection primers F (5′AAGTCCGTGAGCACTGCCAT3′) and R (5′TGAATACAAGTAACGGGAATTGA3′) that amplify a 152-bp fragment of the putative virus were developed and used for RT-PCR detection of the virus as described (4) in 20 F. chiloensis plants obtained from the National Clonal Germplasm Repository (NCGR) in Corvallis, OR. These 20 plants as well as the plant used for the dsRNA isolation were a subset of F. chiloensis clones collected from Chile in 1990 and 1992 as germplasm for the Fragaria collection in the NCGR system (2). Seven of the plants were found to be infected with the virus as determined using RT-PCR and sequencing of the amplicons. There was no correlation between the presence of FClLV and the novel virus. To eliminate the possibility that the sequenced region was encoded by F. chiloensis genome, DNA was isolated (DNeasy; QIAGEN Inc., Valencia, CA) and used as a template in PCR, and no amplicons were obtained in these tests. The possibility that the putative virus belonged to the Endornavirus genus was also examined. DsRNA was extracted, and individual bands were gel purified and subjected to cloning as described (4) and RT-PCR amplification. Both methods indicated that the polymerase region was encoded by a dsRNA species of approximately 1.8 kb, which is similar in size to the genomic molecules of other cryptic viruses that encode the virus polymerase (1). This information indicated that the virus is a novel cryptic virus and the name Fragaria chiloensis cryptic virus is proposed.

References: (1) G. Boccardo and T. Candresse. Arch. Virol. 150:399, 2005. (2) J. S. Cameron et al. Acta Hortic. 348:65, 1993. (3) I. E. Tzanetakis and R. R. Martin. Virus Res. 112:32, 2005. (4) I. E. Tzanetakis et al. Plant Dis. 88:383, 2004.