bluuebunny/crossref_metadata_2025 huggingface dataset:
Pathogenicity to Ornamental Plants of Some Existing Species and New Taxa of Phytophthora from Irrigation Water
Authors: Hong Chuanxue , Richardson Patricia A. , Kong Ping
Published: July 2008

Eighteen isolates from 12 species of Phytophthora, including several new taxa, were tested for pathogenicity to six ornamental and four vegetable species. The following three inoculation methods were used depending on infection court targeted: vermiculite culture inoculation for roots, agar block inoculation for fruit, and zoospore inoculation for foliage. All six new taxa (P. irrigata, P. hydropathica, Dre III, Cil I, Cip-like, and Gon I) are pathogenic to one or more test plants. Specifically, taxon Cil I was identified as a growing threat to horticultural crops, particularly ornamental crops in container production nurseries. The potential host list of P. tropicalis was expanded to four new families (Apocynaceae, Asteraceae, Begoniaceae, and Fabaceae) and one additional genus within each of three existing families (Ericaceae, Cucurbitaceae, and Solanaceae). New potential hosts were also identified for other existing species of Phytophthora. The practical implications of these results in crop health management programs for both ornamental and vegetable crops locally, and for development and implementation of agricultural biosecurity programs globally, are discussed.
Stabilization of Resistance to Leptosphaeria maculans in Brassica napus–B. juncea Recombinant Lines and Its Introgression into Spring-Type Brassica napus
Authors: Chèvre A.-M. , Brun H. , Eber F. , Letanneur J.-C. , Vallee P. , Ermel M. , Glais I. , Li Hua , Sivasithamparam K. , Barbetti M. J.
Published: July 2008

The value of Katanning Early Maturing (KEM) breeding lines from Western Australia, derived from Brassica napus × B. juncea crosses, was assessed as a source of germplasm for resistance to blackleg disease (caused by Leptosphaeria maculans) in spring-type oilseed rape cultivars. The stability of blackleg resistance in these KEM lines was related to key cytological characteristics to determine why there are poor levels of introgression of this resistance into progeny. Promising recombinant KEM lines were crossed with the spring-type B. napus cv. Dunkeld, which has useful polygenic resistance to blackleg, and screened for resistance. The lines were analyzed cytologically for pairing of bivalents in each generation to aid in the selection of stable recombinant lines. KEM recombinant lines showing regular meiotic behavior and a high level of blackleg resistance were obtained for the first time. We also showed that the stable introgression of the B. juncea resistance from the KEM lines into a ‘Dunkeld’ background was possible. Inoculation of selfing and backcross populations with isolates of L. maculans having different AvrLm genes indicated that the B. juncea resistance gene, Rlm6, had been introgressed into a B. napus spring-type cultivar carrying polygenic resistance. The combination of both resistances would enhance the overall effectiveness of resistance against L. maculans. This is clearly needed in Australia and France where cultivars relying upon single dominant gene-based resistance for their effectiveness have proved not durable.
Seedling Resistance to Tan Spot and Stagonospora nodorum Leaf Blotch in Wild Emmer Wheat (Triticum dicoccoides)
Authors: Chu C.-G. , Xu S. S. , Faris J. D. , Nevo E. , Friesen T. L.
Published: July 2008

Tan spot and Stagonospora nodorum blotch (SNB), caused by Pyrenophora tritici-repentis and Stagonospora nodorum, respectively, are two destructive foliar diseases of wheat, causing significant yield reduction worldwide. The objective of this study was to evaluate 172 accessions of wild emmer wheat (Triticum dicoccoides) for seedling resistance to tan spot and SNB. All accessions were inoculated with P. tritici-repentis race 1 and a mixture of three diverse isolates of S. nodorum, respectively. The accessions were also evaluated for sensitivity to host-selective toxins (HSTs), including ToxA produced by both S. nodorum and P. tritici-repentis and culture filtrate produced by S. nodorum. A total of 34 accessions were resistant to tan spot, and 136 accessions were resistant to SNB. Among these accessions, 31 were resistant to both diseases. Significant correlations between HST insensitivity and disease resistance were observed. Our results showed that T. dicoccoides is a good genetic source of resistance to tan spot and SNB in wheat.
Physiologic Specialization of Puccinia triticina on Wheat in the United States in 2006
Authors: Kolmer J. A. , Long D. L. , Hughes M. E.
Published: July 2008

Collections of Puccinia triticina were obtained from rust-infected leaves provided by cooperators throughout the United States and from surveys of wheat fields and nurseries in the Great Plains, Ohio River Valley, southeast, California, and Washington State in order to determine the virulence of the wheat leaf rust population in 2006. Single uredinial isolates (718 in total) were derived from the collections and tested for virulence phenotype on lines of Thatcher wheat that are near-isogenic for leaf rust resistance genes Lr1, Lr2a, Lr2c, Lr3a, Lr9, Lr16, Lr24, Lr26, Lr3ka, Lr11, Lr17a, Lr30, LrB, Lr10, Lr14a, Lr18, Lr2, and Lr28 and winter wheat lines with genes Lr41 and Lr42. In the United States in 2006, 56 virulence phenotypes were found. Virulence phenotypes TDBJG, TDBGG, and TDBJH were among the four most common phenotypes and were all virulent to resistance gene Lr24. These phenotypes were found throughout the Great Plains region. Phenotype MLDSD with virulence to Lr9, Lr17, and Lr41 was also widely distributed in the Great Plains. In the soft red winter wheat region of the southeastern states, phenotypes TCRKG and MBRKG with virulence to genes Lr11, Lr26, and Lr18 were among the common phenotypes. Virulence phenotypes with virulence to Lr16 were most frequent in the spring wheat region of the northern Great Plains. Virulence to Lr21 was not found in any of the tested isolates.
First Report of Impatiens necrotic spot virus Infecting Lettuce in California
Authors: Koike S. T. , Kuo Y.-W. , Rojas M. R. , Gilbertson R. L.
Published: July 2008

Impatiens necrotic spot virus (INSV; family Bunyaviridae, genus Tospovirus) is an important pathogen of ornamental plants in North America and Europe, particularly in the greenhouse industry (2,3). However, INSV is now emerging as a pathogen of vegetable crops. During the 2006 and 2007 growing seasons, lettuce (Lactuca sativa) in Monterey County, CA showed necrotic spotting, leaf chlorosis, and plant stunting typical of symptoms induced by Tomato spotted wilt virus (TSWV). Significant and damaging outbreaks of these disease symptoms were found in numerous romaine, greenleaf, redleaf, butterhead, and iceberg lettuce fields in Monterey and San Benito counties. Samples from symptomatic plants from 21 of 27 fields in Monterey County were negative when tested with TSWV immunostrips (Agdia, Elkhart, IN); however, tests of the TSWV-negative samples with INSV immunostrips were positive. In most fields where INSV was detected, disease development was limited to the edges of fields and disease incidence was <5%; however, some fields had incidences >50% and crop loss was experienced. The virus causing the tospovirus symptoms in the TSWV-negative lettuce was sap transmitted to Nicotiana benthamiana and lettuce, where it induced chlorosis and necrosis. Symptoms in N. benthamiana were consistent with INSV infection, and those in lettuce were similar to symptoms observed in the field. Immunostrip tests confirmed that symptomatic N. benthamiana and lettuce plants were infected with INSV. To further confirm the identity of this virus, reverse transcription (RT)-PCR analysis was conducted with an INSV primer pair that directs the amplification of a ~1.3-kb fragment from the small RNA of INSV (4). The 1.3-kb fragment was amplified from RNA from symptomatic lettuce plants that were INSV positive with immunostrips, and not from asymptomatic lettuce. A total of 38 of 54 samples showing tospovirus-like symptoms were confirmed to be infected with INSV by RT-PCR. Sequences of two representative 1.3-kb DNA fragments were 98 to 99% identical with sequences of INSV isolates from Japan, Italy, and The Netherlands (GenBank Accession Nos. AB109100, DQ425096, and X66972). Taken together with the previous identification of the INSV vector, the western flower thrips (Frankliniella occidentalis), in central California lettuce (1), these results confirm that INSV induced tospovirus symptoms in lettuce fields in Monterey County in 2007. To our knowledge, this is the first report of the occurrence of INSV infecting lettuce in California.

References: (1) W. E. Chaney. Annu. Rep. California Lettuce Res. Board. 2006. (2) M. Daughtrey et al. Plant Dis. 81:1220, 1997. (3) M. D. Law and J. W. Moyer. J. Gen. Virol. 71:933, 1990. (4) R. A. Naidu et al. Online publication. doi: 10.1094/PHP-2005-0727-01-HN. Plant Health Progress, 2005.
First Report of Fruit Rot of Strawberry Caused by an Alternaria sp. in Taiwan
Authors: Ko Y. , Chen C. Y. , Yao K. S. , Liu C. W. , Maruthasalam S. , Lin C. H.
Published: July 2008

In March 2005, a fruit rot disease was found in several commercial strawberry (Fragaria × ananassa Duchesne) fields at Fongyuan, 24.25°N, 120.72°E, in Taichung County in central Taiwan. The disease was rare and was negligible in most cultivated areas. However, disease incidence has increased by 4 to 5% over the last 2 years and causes significant postharvest losses. In storage, symptoms on berries include light brown-to-black, sunken, irregularly shaped lesions. The lesions gradually enlarge and become firm with a dark green-to-black, velvety surface composed of mycelia, conidiophores, and conidia. Twelve single conidial isolates (AF-1 to AF-12) of a fungus were isolated by placing portions of symptomatic fruit from four locations onto acidified potato dextrose agar (PDA) and incubating at 24 ± 1°C. One isolate from each of the four locations, AF-2, 6, 9, and 12, was selected for identification and pathogenicity studies. The fungus was identified as an Alternaria sp. according to the morphological descriptions of A. tenuissima (2,3). Conidiophores were simple or branched, straight or flexuous, septate, pale to light brown, 3.0 to 5.0 μm in diameter, and bore two to six conidia in a chain. Conidia were dark brown, obclavate or oval, and multicellular with seven transverse (in most cases) and numerous longitudinal septa. Conidia were 15.5 to 56.5 μm (average 35.0 μm) long × 6.0 to 15.0 μm (average 11.0 μm) wide at the broadest point. The pathogen was consistently isolated from berries in the field or in storage. Pathogenicity tests were conducted by inoculating 12 surface-sterilized berries with each of the four isolates. Approximately 300 μl of a spore suspension (2 × 105 conidia per ml) was placed at two points on the uninjured surface of each fruit and allowed to dry for 5 min. Control fruits were treated with sterile water. The berries were then enclosed in a plastic bag and incubated at 24 ± 1°C for 2 days. Disease symptoms similar to those described above were observed on 95% of inoculated berries 3 days after inoculation, while no symptoms developed in control berries. Reisolation from the inoculated berries consistently yielded the Alternaria sp. described above. Pathogenicity tests were performed three times. Previously, strawberry fruit rot caused by A. tenuissima was reported from Florida (2) and Malaysia (1), however, to our knowledge, this is the first report of fruit rot of strawberry caused by a species of Alternaria in Taiwan.

References: (1) W. D. Cho et al. List of Plant Diseases in Korea. Korean Society of Plant Pathology, 2004. (2) C. M. Howard and E. E. Albregts. Phytopathology 63:938, 1973. (3) R. D. Milholland. Phytopathology 63:1395, 1973.
First Report of Dollar Spot of Buffalograss Caused by Sclerotinia homoeocarpa in Oklahoma
Authors: Marek S. M. , Moncrief I. R. , Walker N. R.
Published: July 2008

Buffalograss (Buchloe dactyloides (Nutt.) Engelm.) is a perennial, warm-season grass native to the central plains of North America and a dominant plant over much of the shortgrass prairie ecosystem. Its prostrate growth habit and excellent drought tolerance make it a commercially promising turfgrass species, and numerous turf-type cultivars have been released. In the spring of 2007, the southern plains states experienced prolonged periods of excessive precipitation during which numerous buffalograss swards throughout north-central Oklahoma exhibited symptoms of dollar spot (1). A fungus morphologically identical to Sclerotinia homoeocarpa Bennett was consistently isolated from diseased buffalograss leaves collected from three locations in Oklahoma, two from Payne County and one from Logan County. Thirty-day-old seedlings of B. dactyloides (‘Cody’ and ‘Topgun’) and Agrostis stolonifera (‘SR1020’) were inoculated by placing potato dextrose agar (PDA) plugs, colonized by mycelia of each S. homoeocarpa isolate, onto the seedlings' leaves. Sterile PDA plugs were placed on plants as controls. Leaf lesions developed after 4 days only on inoculated plants, and S. homoeocarpa was reisolated from lesions, satisfying Koch's postulates. The nuclear ribosomal internal transcribed spacer (ITS) region was amplified from DNA extracted from cultures of the three buffalograss isolates and a bentgrass isolate using primers ITS4 and ITS5 (2) and sequenced. Sequences were similar to one another (97 to 99% identical), however, two isolates shared a 420-bp, type I intron in the 18S small subunit rDNA. A search of GenBank at NCBI found the ITS sequences were most similar to the ITS regions of other S. homoeocarpa accessions (97% identical). The ITS sequences from the four isolates were deposited in GenBank (Accession Nos. EU123800–EU123803). To our knowledge, this is the first report of dollar spot on a native, warm-season grass in the United States and the disease appears to be endemic to buffalograss in Oklahoma and Kansas (N. A. Tisserat, personal communication).

References: (1) R. W. Smiley et al. Page 22 in: Compendium of Turfgrass Diseases. 3rd ed. The American Phytopathological Society, St. Paul, MN, 2005. (2) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Applications. Academic Press Inc., New York, 1990.
First Report of Tar Spot on Orange Geiger, Cordia sebestena, Caused by Diatractium cordianum in Florida
Authors: Palmateer A. J. , Pérez J. M. , Cating R. A. , Ploetz R. C. , Hoy M. A.
Published: July 2008

In July 2007, tar spot symptoms were observed on the leaves of orange Geiger, Cordia sebestena L. (Boraginaceae), in the landscape and a commercial nursery in Homestead, FL. The disease appears to be spreading and is locally severe. Symptoms were circular, slightly hypertrophied spots approximately 5 to 8 cm in diameter, which were slightly chlorotic on the abaxial surface and had numerous circular blackened stroma, 0.2 to 0.4 mm in diameter, on the adaxial surface. As leaves aged and yellowed, the areas around the spots remained pale green. Embedded in the stroma were numerous perithecia, 173 to 312 μm in diameter, circular to irregular in shape, with lateral necks as much as 200 μm long and 73 to 104 μm in diameter. Asci, 77 to 92 × 11 to 13 μm, contained elongate, two-celled ascospores, 50 to 61 × 3 to 5 μm that had a conspicuous constriction at the dividing cell wall. These dimensions and the pathogen's appearance matched closely with those published for Diatractium cordianum (Ellis & Kelsey) Syd (1). Young, symptomless leaves of C. sebestena were sprayed to runoff with a suspension of ascospores approximately 104 ml–1 that were harvested from affected leaves. Inoculated leaves were placed on water-saturated paper towels in petri plates and maintained in a growth chamber at 25°C with fluorescent light at 10 h day–1. Symptoms similar to those observed on affected trees in the landscape began to develop after 21 days and perithecia were evident after 28 days. An ITS 1, ITS 2, and 5.8s rDNA sequence was deposited in GenBank (Accession No. EU541488). A herbarium specimen was deposited at the U.S. National Fungus Collections (BPI No. 878441). This is a new host record for D. cordianum and is the first time the pathogen has been reported in the United States. Previous records were from Venezuela and several Caribbean islands, including Cuba and Jamaica. Symptoms of this disease have not been observed on Texas wild olive, Cordia boissieri, in close proximity to affected C. sebestena. P. F. Cannon (1) indicated that the disease had no economic impact. However, the conspicuous nature of symptoms on C. sebestena and the importance of this tree in the South Florida ornamental trade (2) suggest that this disease may become significant on the latter host.

References: (1) P. F. Cannon. Mycol. Res. 92:327, 1989. (2) E. F. Gilman and D. G. Watson. Fact Sheet ST-182. Univ. Fla, Fla Coop Ext. Serv., 1993.
First Report of Pine Wilt Disease on Pinus koraiensis in Korea
Authors: Han H. , Chung Y.-J. , Shin S.-C.
Published: July 2008

Pine wilt disease is one of the most important forest tree diseases, especially in the East Asian countries of Japan, China, and Korea. The causal agent, Bursaphelenchus xylophilus (3), is transmitted by the insect vectors, pine sawyer beetles (Monochamus spp.). The vectors mainly attack coniferous trees and the infected trees die within several weeks. In Korea, pine wilt disease was first reported in Busan City in 1988, and now, the damaged area covers 7,820 ha and more than 60 cities in Korea. The main host trees are Pinus densiflora and P. thunbergii, which are the most common pines distributed in Korea. In 2006, however, we found pine wilt disease in a forest of P. koraiensis located in Gwangju City in Gyeonggi Province. Symptoms were systemic and leaves turned brown or yellowish. Wood samples were collected from the affected trees, and nematodes were extracted by a modified Baermann's funnel method. After 24 h, nematodes were collected from wood chips, and morphology was observed with an inverted light microscope (Leica DE/DMI 3000B, Wetzlar, Germany). Morphology was characterized by a typical Aphelenchoid-type esophagus, head constriction, female vulva flap, female tail, and a male spicule shape similar to B. xylophilus. For more accurate identification, DNA was extracted from individual nematodes with a DNeasy Kit (Qiagen, Valencia, CA). The internal transcribed spacers (ITS) 1 and 2 and 5.8S regions were amplified by PCR (1). Sequenced nucleotide information was compared with the sequences of B. xylophilus already reported in GenBank (Accession Nos. AB294736, AB277208, AM 157747, AY 347913, and BXU92464). ITS DNA sequences of the nematode from Korean pine was >99% identical to B. xylophilus in GenBank. The B. xylophilus from Korean pine tree was also successfully cultured in Botrytis cinerea medium and pathogenicity was tested from June to October 2007. More than 95% mortality was observed with the inoculation of 20 replicate 15-year-old trees of P. koraiensis and P. densiflora with 15,000 nematodes per tree. Therefore, we confirmed that pine wilt disease occurred in P. koraiensis in Korea. P. koraiensis is an endemic species in Korea and distribution is limited to the northern Korean Peninsula and some locations in Russia. It has been shown that P. koraiensis is susceptible to the pine wood nematode by an inoculation test in Japan (2); however, to our knowledge, this is the first report of pine wilt disease on P. koraiensis under field conditions in Korea.

References: (1) W. K. Burgermeister et al. Russ. J. Nematol. 13:29, 2005. (2) K. Futai and T. Furuno. Bull. Kyoto Univ. For. 51:3, 1979. (3) G. Steiner and E. M. Buhrer. J. Agr. Res. 48:946, 1934.
High Susceptibility of Olive Cultivar FS-17 to Alternaria alternata in Southern Spain
Authors: Moral J. , De la Rosa R. , León L. , Barranco D. , Michailides T. J. , Trapero A.
Published: July 2008

Traditional olive orchards in Spain have been planted at a density of 70 to 80 trees per ha with three trunks per tree. During the last decade, the hedgerow orchard, in which planting density is approximately 2,000 trees per ha, was developed. In 2006 and 2007, we noted a severe outbreak of fruit rot in FS-17, a new cultivar from Italy, in an experimental hedgerow planting in Córdoba, southern Spain. The incidence of fruit rot in ‘FS-17’ was 80% in January of 2006 and 24% in January of 2007. Cvs. Arbosana, IRTA-i18 (a selected clone from ‘Arbequina’), and Koroneiki had no symptoms in either year of the study. Disease incidence in ‘Arbequina’ was <0.1% only in 2006. Affected fruits were soft with gray-white skin and they eventually mummified. Black-green sporodochia were observed on the surface of diseased fruits. A fungus was isolated from diseased fruits on potato dextrose agar (PDA) and incubated at 22 to 26°C with a 12-h photoperiod. After 8 days of growing on PDA, fungal colonies formed conidial chains having a main axis with up to 10 conidia and secondary and tertiary short branches with two to four conidia. Conidia were obpyriform, ovoid, or ellipsoidal, without a beak or with a short beak, had up to four transverse septa, and measured 11.7 to 24.7 (mean 19.6) μm long and 7.7 to 13.0 (mean 9.6) μm wide at the broadest part of the conidium. The length of the beak of conidia was variable, ranging from 0 to 28.6 (mean 5.5) μm. The fungus was identified as Alternaria alternata (1). Pathogenicity tests were performed by spraying 40 mature fruits of ‘FS-17’ with a spore suspension (1 × 106 spores per ml). The same number of control fruits was treated with water. After 21 days, inoculated fruit developed symptoms that had earlier been observed in the field. A. alternata was reisolated from lesions on all infected fruits. The fungus was not isolated from any of the control fruits. The experiment was performed twice. The new growing system and the high susceptibility of some olive cultivars, such as FS-17, may result in a high incidence of disease caused by a pathogen that is generally characterized as weakly virulent. To our knowledge, this is the first report of A. alternata causing a severe outbreak of fruit rot on olive trees in the field.

References: (1) B. M. Pryor and T. J. Michailides. Phytopathology 92:406, 2002.
Crown Rot of Strawberry Caused by Macrophomina phaseolina in California
Authors: Koike S. T.
Published: July 2008

In 2006 and 2007, severely diseased strawberry (Fragaria × ananassa) plants were observed in five commercial fields in southern California (Orange County). Disease generally occurred in discrete patches. Within such patches, disease incidence ranged from 10 to 75%. Symptoms consisted of wilting of foliage, drying and death of older leaves, plant stunting, and eventual collapse and death of plants. When plant crowns were dissected, internal vascular and cortex tissues were dark brown to orange brown. Fruiting bodies or other fungal structures were not observed. A fungus was consistently isolated from symptomatic crown tissue that had been surface sterilized and placed on acidified corn meal agar (LA-CMA). All isolates produced numerous, dark, irregularly shaped sclerotia that were 67 to 170 μm long and 44 to 133 μm wide. When isolates were grown on 1.5% water agar with dried and sterilized wheat straw, dark, ostiolate pycnidia and hyaline, single-celled, cylindrical conidia were produced. On the basis of these characters, all isolates were identified as Macrophomina phaseolina (1). The symptomatic plants tested negative for Colletotrichum spp., Phytophthora spp., Verticillium dahliae, and other pathogens. Inoculum for pathogenicity tests was produced by growing six isolates on CMA on which sterilized wood toothpicks were placed on the agar surface. After 1 week, toothpicks were removed and inserted 4 to 5 mm deep into the basal crown tissue of potted strawberry plants (cv. Camarosa) grown in soilless, peatmoss-based rooting medium. Ten plants were inoculated per isolate and one toothpick was inserted per plant. Ten control strawberry plants were treated by inserting one sterile toothpick into each crown. All plants were then grown in a shadehouse. After 2 weeks, all inoculated plants began to show wilting and decline of foliage. By 4 weeks, all inoculated plants had collapsed. Internal crown tissue was discolored and similar in appearance to the original field plants. M. phaseolina was isolated from all inoculated plants. Control plants did not exhibit any disease symptoms, and crown tissue was symptomless. The test was repeated and the results were similar. While M. phaseolina has been periodically associated with strawberry in California (3), to my knowledge, this is the first report of charcoal rot disease on commercial strawberry in California. Charcoal rot of strawberry has been reported in Egypt, France, India, Israel, and the United States (Florida and Illinois) (2,4). Similar to previous reports (2,4), many of the affected California fields were not preplant fumigated with methyl bromide + chloropicrin fumigants, and it is possible that under these changing production practices this pathogen may increase in importance in California.

References: (1) P. Holliday and E. Punithalingam. No. 275 in: Descriptions of Pathogenic Fungi and Bacteria. CMI, Kew, Surrey, UK, 1970. (2) J. Mertely et al. Plant Dis.89:434, 2005. (3) S. Wilhelm. Plant Dis. Rep. 41:941, 1957. (4) A. Zveibil and S. Freeman. Plant Dis. 89:1014, 2005.
First Report of Black raspberry necrosis virus in Rubus canadensis in Tennessee
Authors: Sabanadzovic S. , Ghanem-Sabanadzovic N. Abou
Published: July 2008

Symptoms that resembled virus infection were observed on several smooth blackberry (Rubus canadensis L.) plants in the Great Smoky Mountain National Park (GSMNP) during a project carried out in the summer and fall of 2006 as part of All Taxa Biodiversity Inventory (ATBI) activities (2). Diseased specimens showed chlorosis and mottling as well as deformation of younger leaves. Symptomatic leaves were collected, and preliminary screening by double-antibody sandwich (DAS)-ELISA did not detect Tobacco ringspot virus (TRSV), Tomato ringspot virus (ToRSV), Tomato spotted wilt virus (TSWV), Raspberry bushy dwarf virus (RBDV), or Impatiens necrotic spot virus (INSV) in these samples. Double-stranded RNA (dsRNA) extracted from symptomatic leaves of two diseased specimens (GSM-1 and GSM-2) revealed two bands with sizes estimated at 7.5 and 6.5 kb. Purified dsRNAs from specimen GSM-1 were used as a template to generate random-primed cDNA clones. Several clones were sequenced and analysis of approximately 3 kb of contiguous sequence (GenBank Accession No. EU419645) revealed the presence of a single open reading frame encoding a protein containing the complete proteinase and partial polymerase domains. BLAST analysis showed that the virus from R. canadensis shared 77 and 87% nucleotide and amino acid sequence identity, respectively, with the recently described putative sadwavirus Black raspberry necrosis virus (BRNV) (GenBank Accession No. NC_008182) (1), suggesting that this virus is a distinct isolate of BRNV. The virus shared a lower degree of identity with the analogous sequences of other viruses belonging to the genus Sadwavirus, with only 48 and 37% identity with Strawberry mottle virus (GenBank Accession No. NC_003445) and Satsuma dwarf virus (GenBank Accession No. NC_003785), respectively. To our knowledge, this is the first report of BRNV in GSMNP and Tennessee, indicating that it may be widespread in native Rubus spp. through the southeastern United States.

References: (1) A. Halgren et al. Phytopathology 97:44, 2007. (2) M. J. Sharkey. Fla. Entomol. 84:556, 2001.
Sources of Inoculum for Phytophthora ramorum in a Redwood Forest
Authors: Davidson J. M. , Patterson H. A. , Rizzo D. M.
Published: July 2008

Sources of inoculum were investigated for dominant hosts of Phytophthora ramorum in a redwood forest. Infected trunks, twigs, and/or leaves of bay laurel (Umbellularia californica), tanoak (Lithocarpus densiflorus), and redwood (Sequoia sempervirens) were tested in the laboratory for sporangia production. Sporangia occurred on all plant tissues with the highest percentage on bay laurel leaves and tanoak twigs. To further compare these two species, field measurements of inoculum production and infection were conducted during the rainy seasons of 2003-04 and 2004-05. Inoculum levels in throughfall rainwater and from individual infections were significantly higher for bay laurel as opposed to tanoak for both seasons. Both measurements of inoculum production from bay laurel were significantly greater during 2004-05 when rainfall extended longer into the spring, while inoculum quantities for tanoak were not significantly different between the 2 years. Tanoak twigs were more likely to be infected than bay laurel leaves in 2003-04, and equally likely to be infected in 2004-05. These results indicate that the majority of P. ramorum inoculum in redwood forest is produced from infections on bay laurel leaves. Years with extended rains pose an elevated risk for tanoak because inoculum levels are higher and infectious periods continue into late spring.
Colonization of Resistant and Susceptible Lettuce Cultivars by a Green Fluorescent Protein-Tagged Isolate of Verticillium dahliae
Authors: Vallad G. E. , Subbarao K. V.
Published: July 2008

Interactions between lettuce and a green fluorescent protein (GFP)-expressing, race 1 isolate of Verticillium dahliae, were studied to determine infection and colonization of lettuce cultivars resistant and susceptible to Verticillium wilt. The roots of lettuce seedlings were inoculated with a conidial suspension of the GFP-expressing isolate. Colonization was studied with the aid of laser scanning confocal and epi-fluorescence microscopes. Few differences in the initial infection and colonization of lateral roots were observed between resistant and susceptible cultivars. Hyphal colonies formed on root tips and within the root elongation zones by 5 days, leading to the colonization of cortical tissues and penetration of vascular elements regardless of the lettuce cultivar by 2 weeks. By 8 to 10 weeks after inoculation, vascular discoloration developed within the taproot and crown regions of susceptible cultivars well in advance of V. dahliae colonization. Actual foliar wilt coincided with the colonization of the taproot and crown areas and the eruption of mycelia into surrounding cortical tissues. Advance colonization of stems, pedicels, and inflorescence, including developing capitula and mature achenes was observed. Seedborne infection was limited to the maternal tissues of the achene, including the pappus, pericarp, integument, and endosperm; but the embryo was never compromised. Resistant lettuce cultivars remained free of disease symptoms. Furthermore, V. dahliae colonization never progressed beyond infected lateral roots of resistant cultivars. Results indicated that resistance in lettuce may lie with the plant's ability to shed infected lateral roots or to inhibit the systemic progress of the fungus through vascular tissues into the taproot.
Quantitative Trait Loci for Seedling and Adult Plant Resistance to Stagonospora nodorum in Wheat
Authors: Shankar M. , Walker E. , Golzar H. , Loughman R. , Wilson R. E. , Francki M. G.
Published: July 2008

Stagonospora nodorum blotch (SNB) caused by Stagonospora nodorum is a severe disease of wheat (Triticum aestivum) in many areas of the world. S. nodorum affects both seedling and adult plants causing necrosis of leaf and glume tissue, inhibiting photosynthetic capabilities, and reducing grain yield. The aims of this study were to evaluate disease response of 280 doubled haploid (DH) individuals derived from a cross between resistant (6HRWSN125) and susceptible (WAWHT2074) genotypes, compare quantitative trait loci (QTL) for seedling and adult plant resistance in two consecutive years, and assess the contribution of QTL on grain weight. Flag leaves and glumes of individuals from the DH population were inoculated with mixed isolates of S. nodorum at similar maturity time to provide accurate disease evaluation independent of morphological traits and identify true resistance for QTL analysis. Fungicide protected and inoculated plots were used to measure relative grain weight (RGW) as a yield-related trait under pathogen infection. The lack of similar QTL and little or no correlation in disease scores indicate different genes control seedling and adult plant disease and independent genes control flag leaf and glume resistance. This study consistently identified a QTL on chromosome 2DL for flag leaf resistance (QSnl.daw-2D) and 4BL for glume resistance (QSng.daw-4B) from the resistant parent, 6HRWSN125, explaining 4 to 19% of the phenotypic variation at each locus. A total of 5 QTL for RGW were consistently detected, where two were in the same marker interval for QSnl.daw-2D and QSng.daw-4B indicating the contribution of these QTL to yield related traits. Therefore, RGW measurement in QTL analysis could be used as a reliable indicator of grain yield affected by S. nodorum infection.
Characterization of a Resistance Locus (Pfs-1) to the Spinach Downy Mildew Pathogen (Peronospora farinosa f. sp. spinaciae) and Development of a Molecular Marker Linked to Pfs-1
Authors: Irish B. M. , Correll J. C. , Feng C. , Bentley T. , de los Reyes B. G.
Published: July 2008

Downy mildew is a destructive disease of spinach worldwide. There have been 10 races described since 1824, six of which have been identified in the past 10 years. Race identification is based on qualitative disease reactions on a set of diverse host differentials which include open-pollinated cultivars, contemporary hybrid cultivars, and older hybrid cultivars that are no longer produced. The development of a set of near-isogenic open-pollinated spinach lines (NILs), having different resistance loci in a susceptible and otherwise common genetic background, would facilitate identification of races of the downy mildew pathogen, provide a tool to better understand the genetics of resistance, and expedite the development of molecular markers linked to these disease resistance loci. To achieve this objective, the spinach cv. Viroflay, susceptible to race 6 of Peronospora farinosa f. sp. spinaciae, was used as the recurrent susceptible parent in crosses with the hybrid spinach cv. Lion, resistant to race 6. Resistant F1 progeny were subsequently backcrossed to Viroflay four times with selection for race 6 resistance each time. Analysis of the segregation data showed that resistance was controlled by a single dominant gene, and the resistance locus was designated Pfs-1. By bulk segregant analysis, an amplified fragment length polymorphism (AFLP) marker (E-ACT/M-CTG) linked to Pfs-1 was identified and used to develop a co-dominant Sequence characterized amplified region (SCAR) marker. This SCAR marker, designated Dm-1, was closely linked (≈1.7 cM) to the Pfs-1 locus and could discriminate among spinach genotypes that were homozygous resistant (Pfs-1Pfs-1), heterozygous resistant (Pfs-1pfs-1), or homozygous susceptible (pfs-1pfs-1) to race 6 within the original mapping population. Evaluation of a wide range of commercial spinach lines outside of the mapping population indicated that Dm-1 could effectively identify Pfs-1 resistant genotypes; the Dm-1 marker correctly predicted the disease resistance phenotype in 120 out of 123 lines tested. In addition, the NIL containing the Pfs-1 locus (Pfs-1Pfs-1) was resistant to multiple races of the downy mildew pathogen indicating Pfs-1 locus may contain a cluster of resistance genes.
Variability in Morphology and Aggressiveness Among North American Vegetative Compatibility Groups of Colletotrichum coccodes
Authors: Aqeel A. M. , Pasche J. S. , Gudmestad N. C.
Published: July 2008

North American isolates of Colletotrichum coccodes, representing six vegetative compatibility groups (NA-VCG), were used to study morphological and pathogenic variability. The objective was to determine if variability in conidial and microsclerotial size was related to pathogenicity. Significant differences were detected in length, width, and length/width ratios of conidia as well as in the length and width of microsclerotia among the NA-VCGs. The longest and widest conidia were produced by isolates belonging to NA-VCG1 and the largest microsclerotia were produced by isolates of NA-VCG2. Conidial and microsclerotial lengths and widths also were affected significantly by type of growth medium. There was no relationship between the size of conidia and the size of microsclerotia among the NA-VCGs studied. Conidial and microsclerotial size may affect inoculum potential and survival as isolates of NA-VCG2 have been demonstrated to occur more frequently than other NA-VCGs. Aggressiveness of 17 isolates of C. coccodes representing six NA-VCG's was studied on three potato cultivars using foliar and root inoculation methods. C. coccodes infection reduced tuber weight in all cultivars with both inoculation methods although tuber weight reductions were significantly higher following root inoculations than foliar inoculations. Pathogenic aggressiveness varied among NA-VCGs. Isolates belonging to NA-VCG2 and 3 were the least aggressive on potato foliage and isolates of NA-VCG1, 2, 3, 4, and 5 produced higher microsclerotial density on all three cultivars compared with isolates of NA-VCG6. Across inoculation methods, isolates of C. coccodes belonging to NA-VCG2 and 6 were the most aggressive based on reductions in tuber weight. Umatilla Russet was the most susceptible cultivar to C. coccodes compared to other cultivars regardless of inoculation method. These results demonstrate variability in morphology and pathogenic aggressiveness among the NA-VCGs of C. coccodes but these traits are not related.
Identifying Quantitative Trait Loci for Resistance to Sclerotinia Head Rot in Two USDA Sunflower Germplasms
Authors: Yue B. , Radi S. A. , Vick B. A. , Cai X. , Tang S. , Knapp S. J. , Gulya T. J. , Miller J. F. , Hu J.
Published: July 2008

Sclerotinia head rot is a major disease of sunflower in the world, and quantitative trait loci (QTL) mapping could facilitate understanding of the genetic basis of head rot resistance and breeding in sunflower. One hundred twenty-three F2:3 and F2:4 families from a cross between HA 441 and RHA 439 were studied. The mapping population was evaluated for disease resistance in three field experiments in a randomized complete block design with two replicates. Disease incidence (DI) and disease severity (DS) were assessed. A genetic map with 180 target region amplification polymorphism, 32 simple sequence repeats, 11 insertion-deletion, and 2 morphological markers was constructed. Nine DI and seven DS QTL were identified with each QTL explaining 8.4 to 34.5% of phenotypic variance, suggesting the polygenic basis of the resistance to head rot. Five of these QTL were identified in more than one experiment, and each QTL explained more than 12.9% of phenotypic variance. These QTL could be useful in sunflower breeding. Although a positive correlation existed between the two disease indices, most of the respective QTL were located in different chromosomal regions, suggesting a different genetic basis for the two indices.
Genetic Structure of Populations of Rhizoctonia solani Anastomosis Group-1 IA from Soybean in Brazil
Authors: Ciampi M. B. , Meyer M. C. , Costa M. J. N. , Zala M. , McDonald B. A. , Ceresini P. C.
Published: July 2008

The Basidiomycete fungus Rhizoctonia solani anastomosis group (AG)-1 IA is a major pathogen of soybean in Brazil, where the average yield losses have reached 30 to 60% in some states in Northern Brazil. No information is currently available concerning levels of genetic diversity and population structure for this pathogen in Brazil. A total of 232 isolates of R. solani AG1 IA were collected from five soybean fields in the most important soybean production areas in central-western, northern, and northeastern Brazil. These isolates were genotyped using 10 microsatellite loci. Most of the multilocus genotypes (MLGTs) were site-specific, with few MLGTs shared among populations. Significant population subdivision was evident. High levels of admixture were observed for populations from Mato Grosso and Tocantins. After removing admixed genotypes, three out of five field populations (Maranhao, Mato Grosso, and Tocantins), were in Hardy-Weinberg (HW) equilibrium, consistent with sexual recombination. HW and gametic disequilibrium were found for the remaining soybean-infecting populations. The findings of low genotypic diversity, departures from HW equilibrium, gametic disequilibrium, and high degree of population subdivision in these R. solani AG-1 IA populations from Brazil are consistent with predominantly asexual reproduction, short-distance dispersal of vegetative propagules (mycelium or sclerotia), and limited long-distance dispersal, possibly via contaminated seed. None of the soybean-infecting populations showed a reduction in population size (bottleneck effect). We detected asymmetric historical migration among the soybean-infecting populations, which could explain the observed levels of subdivision.
Integrated Approach for Detection of Nonculturable Cells of Ralstonia solanacearum in Asymptomatic Pelargonium spp. Cuttings
Authors: Marco-Noales E. , Bertolini E. , Morente C. , López M. M.
Published: July 2008

Ralstonia solanacearum (biovar 2, race 3) is a soil and water-borne pathogen that causes serious diseases in several solanaceous hosts. It can also infect geranium plants, posing an important threat to their culture when latently infected cuttings are imported from countries where the pathogen is endemic. R. solanacearum can be present in very low numbers in asymptomatic geranium cuttings, and/or in a particular stressed physiological state that escapes direct isolation on the solid media usually employed. Consequently, an integrated protocol has been developed to analyze asymptomatic geranium cuttings routinely. The first screening tests include isolation and co-operational-polymerase chain reaction (Co-PCR), based on the simultaneous and co-operational action of three primers from 16S rRNA of R. solanacearum. This method was selected as the most sensitive one, able to detect only 1 cell/ml including nonculturable cells. When isolation is negative but Co-PCR is positive, the bioassay in tomato plants is proposed, since stressed bacterial cells or those present in low numbers that do not grow on solid media can be recovered from inoculated tomato plants and retain pathogenicity. This methodology has been demonstrated to be useful and has allowed us to assess the relevance of the physiological status of bacterial cells and its implications in detection. It also reveals the risk of introducing R. solanacearum through asymptomatic geranium material when relying only on bacterial isolation.
Differential profiling of selected defence‐related genes induced on challenge with Alternaria brassicicola in resistant white mustard and their comparative expression pattern in susceptible India mustard
Authors: GHOSE KAUSHIK , DEY SANJUKTA , BARTON HANNAH , LOAKE GARY J. , BASU DEBABRATA
Published: July 2008

The lack of availability of sources of resistance against Alternaria brassicicola within the family Brassicaceae has made oilseed mustard plants a target for one of the most damaging and widespread fungal diseases, Alternaria black spot. Of the other non‐host‐resistant/tolerant plants, Sinapis alba, white mustard, is considered to be the most important apart from Arabidopsis. To understand the defence response of S. alba upon incompatible interaction with this pathogen, a functional genomic approach using cDNA amplified fragment length polymorphism was performed. The highly reproducible bands, found to be either more amplified or uniquely present in infected S. alba plants compared with non‐infected plants, were further subjected to comparative reverse Northern analysis in the incompatible white mustard (S. alba) and compatible India mustard (Brassica juncea L.) plants. The suppression of 46% of the genes in the compatible background indicates the possibility of effective and specific recognition of Alternaria in S. alba. Analysis of the 118 genes up‐regulated specifically in infected S. alba compared with B. juncea showed that 98 genes have similarity to proteins such as receptor‐like protein kinase genes, genes involved with calcium‐mediated signalling and salicylic acid‐dependent genes as well as other genes of known function in Arabidopsis. The apparent expression profile data were further confirmed for selected genes by quantitative real‐time polymerase chain reaction analysis. Classification of these genes on the basis of their induction pattern in Arabidopsis indicates that the expression profile of several of these genes was distinct in S. alba compared with B. juncea.
ABCB1 polymorphisms may have a minor effect on ciclosporin blood concentrations in myasthenia gravis patients
Authors: Zhang Ya‐tong , Yang Li‐ping , Shao Hong , Li Ke‐xin , Sun Chun‐hua , Shi Lu‐wen
Published: July 2008

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

• Numerous studies have shown that MDR1 polymorphisms in the form of single nucleotide poymorphisms or haplptype affect ciclosporin pharmacokinetics or blood concentrations in organ transplantation patients, but some results conflict with others.

WHAT THIS STUDY ADDS

• We had thought that the diease condition might conceal the minor effect of MDR1 polymorphisms.

• We chose myasthenia gravis patients as a population in which disease conditions were less severe.

• We also used different pharmacokinetics indices, such as dose‐adjusted trough blood concentrations, dose‐adjusted peak blood concentrations and trough blood concentrations under the same ciclosporin regimen.

AIMSCiclosporin (CsA), which is widely used in autoimmune disease and transplantation, has a narrow therapeutic index. It also shows considerable interindividual variability in its pharmacokinetics, which may be attributable to polymorphisms of the multidrug efflux pump P‐glycoprotein, encoded by MDR‐1. The aim was to determine the role of genetic polymorphisms in MDR‐1 with respect to interindividual variability of CsA blood concentrations in myasthenia gravis (MG) patients.

METHODSMG patients (n = 129) receiving CsA were genotyped for MDR‐1 1236C→T (exon 12), 2677G→T (exon 21) and 3435C→T (exon 26). Trough blood and peak blood concentrations were determined to see if there was correlation with the corresponding genotype.

RESULTSWe observed a trend for CsA blood concentrations, especially peak blood concentrations, to be higher with the wild‐type allele compared with minor alleles in genotype and haplotype. Furthermore, under the same CsA regimen, it was found that the trough concentrations of variant genotype (ABCB1 1236TT or ABCB1 2677TT) were significant greater than those of wild‐type (ABCB1 1236CC or ABCB1 2677GG, respectively) (P = 0.0222 and 0.0081). The trough concentrations of wild‐type haplotype pair group were significantly lower those that of the mutant type pair group (TT‐TT‐TT) (P = 0.007).

CONCLUSIONSABCB1 polymorphisms in both genotype and haplotype may have a minor effect on the CsA blood concentrations.