bluuebunny/crossref_metadata_2025 huggingface dataset:
First Report of Daylily Rust Caused by Puccinia hemerocallidis in the Western Cape Province of South Africa
Authors: Mostert L. , Bester W. , Coertze S. , Wood A. R.
Published: June 2008

Rust symptoms were first observed on daylily plants (Hemerocallis spp.) during February 2007 in a garden near Paarl in the Western Cape (WC) Province of South Africa. Another occurrence was found during November 2007 on daylily plants in a garden near Franschhoek (WC). Upon further investigation, diseased daylily plants were found during February 2008 in nurseries in Stellenbosch, Buffeljagsrivier, and George (WC). The cultivars that have been infected include Laura Lane, Anna Mae Hager, and Russian Rhapsody. Symptoms included yellow-to-brown streaks on the leaves. Leaves had small chlorotic spots on the adaxial side, and on the abaxial side, were many small orange-to-yellow erumpent pustules with yellow-to-orange, pulverulent urediniospores. The rust fungus was identified as Puccinia hemerocallidis Thüm. The morphology matches that given in Hernández et al. (1). Urediniospores were globose to ellipsoid with yellow contents and measured 22 to 31 × 16 to 26 μm (mean 25.5 × 22 μm, n = 25). Spore walls were echinulate, hyaline, 2 to 3 μm thick, and with obscure germ pores. No teliospores were observed. Herbarium specimens have been lodged in the South African National Fungus Collection in Pretoria (PREM 59814, 59855, and 59856). The alternative host, Patrinia spp., is not endemic to South Africa and according to several nurseries in the WC, also not sold. P. hemerocallidis has previously been reported from eastern Asia, the United States, and Costa Rica (1,2). To our knowledge, this is the first report of P. hemerocallidis on daylilies in South Africa.

References: (1) J. R. Hernandez et al. Plant Dis. 86:1194, 2002. (2) J. L. Williams-Woodward et al. Plant Dis. 85:1121, 2001.
First Report of Sclerotinia sclerotiorum on Calceolaria integrifolia in Italy
Authors: Garibaldi A. , Minuto A. , Gullino M. L.
Published: June 2008

Calceolaria integrifolia L. is an ornamental species grown as a potted plant in Liguria, northern Italy. In the winter of 2006, extensive chlorosis was observed on approximately 10% of the 10-month-old potted plants in a commercial greenhouse. Initial symptoms included stem necrosis and darkening of leaves. As stem and foliar necrosis progressed, infected plants wilted and died. Wilt occurred on young plants within a few days after the initial appearance of symptoms. Infected plants were characterized by the presence of soft, watery tissues that became covered with white mycelium and dark sclerotia. The diseased stem tissue was surface sterilized for 1 min in 1% NaOCl and plated on potato dextrose agar (PDA) amended with 100 mg/liter of streptomycin sulfate. Sclerotinia sclerotiorum (Lib.) de Bary (3) was consistently recovered from infected stem pieces. Sclerotia observed on infected plants measured 0.7 to 1.0 × 2.8 to 4.4 mm (average 1.6 to 2.1 mm). Sclerotia produced on PDA measured 1.0 to 1.1 × 3.0 to 4.2 mm (average 1.7 to 2.3 mm). The internal transcribed spacer (ITS) region of rDNA was amplified with primers ITS4/ITS6 and sequenced. BLASTn analysis (1) of the 522-bp amplicon resulted in 100% homology with the sequence of S. sclerotiorum. The nucleotide sequence has been assigned GenBank Accession No. EU 627004. Pathogenicity of two isolates obtained from infected plants was confirmed by inoculating 10 120-day-old plants grown in individual 14-cm-diameter pots maintained in a greenhouse under partial shade. Inoculum consisted of 1 cm2 of mycelial plugs excised from a 10-day-old PDA culture of each isolate. Plants were inoculated by placing a mycelial plug on the soil surface around the base of each plant. Ten plants were inoculated per isolate and an equal number of noninoculated plants served as controls. The trial was repeated once. All plants were kept at temperatures ranging between 8 and 17°C (average 12.5°C) and watered as needed. All inoculated plants developed leaf yellowing within 8 days after inoculation, soon followed by the appearance of white mycelium and sclerotia, and then by wilt. Control plants remained symptomless. S. sclerotiorum was reisolated from the stems of inoculated plants. S. sclerotiorum was reported previously on a Calceolaria sp. in the United States (2). To our knowledge, this is the first report of white mold on C. integrifolia in Italy. The economic importance of this disease is currently limited.

References (1) S. F. Altschul et al. Nucleic Acids Res. 25:3389, 1997. (2) Anonymous. USDA Agric. Handb. 165:441, 1960. (3) N. F. Buchwald. Den. Kgl. Veterin.er-og Landbohojskoles Aarsskrift 75, 1949.
First Report of Paulownia Witches'-Broom Phytoplasma in China
Authors: Yue H. N. , Wu Y. F. , Shi Y. Z. , Wu K. K. , Li Y. R.
Published: June 2008

Paulownia witches'-broom (PaWB) is one of the most important diseases affecting Paulownia tomentosa trees in China. According to 2006 statistics, the disease has affected 880,000 ha of trees for timber production causing billions of dollars in economic losses. During the spring and summer of 2006, a survey was done in Shaanxi Province to confirm phytoplasma infection of paulownia trees exhibiting symptoms of witches'-broom, stunting, yellowing, and proliferating secondary shoots. Foliage samples were collected from 24 symptomatic and 8 symptomless paulownia plants in eight different production fields. Total DNA was extracted from 0.5 g of leaf midrib and stem phloem tissue with a modified cetyltrimethylammoniumbromide (CTAB) method (3). Resulting DNA extracts were analyzed by a nested PCR assay using phytoplasma 16S rRNA gene primer pairs R16mF2/R16mR1 followed by R16F2n/ R16R2 (1), which amplified a 1.4-kb and a 1.2-kb product, respectively, from symptomatic plants. Restriction fragment length polymorphism (RFLP) analysis of the nested 1.2-kb 16S rDNA products with AluI, MseI, HhaI, HpaI, RsaI, BfaI, HinfI, and TaqI endonuclease (2) indicated that all symptomatic plants were infected by a phytoplasma belonging to aster yellows group (16SrI) subgroup D (16SrI-D) phytoplasma strains. A 1.2-kb 16S rDNA sequence (GenBank Accession No. DQ851169) derived from representative strain PaWB-Shaanxi was identical (100%) to that of PaWB phytoplasma (L27033), a known subgroup 16SrI-D strain from Taiwan (2). The agreement between the RFLP analysis and sequence data confirms that PaWB from Shaanxi is a member of subgroup 16SrI-D. To our knowledge, this is the first report of PaWB disease being present in China and of its association with the 16SrI-D subgroup.

References: (1) D. E. Gundersen and I.-M. Lee. Phytopathol. Mediterr. 35:144, 1996. (2) I.-M. Lee et al. Inst. J. Syst. Bacteriol. 48:1153, 1998. (3) Y. Qi et al. Biotechnol. Bull. 4:44, 2004.
First Report of Wisteria vein mosaic virus on Wisteria sinensis in New Zealand
Authors: Ward L. I. , Tang J. Z. , Clover G. R. G.
Published: June 2008

Wisteria vein mosaic virus (WVMV) is a member of the Potyvirus genus. The virus has been reported in Wisteria spp. in Australia, China, the United States, and a number of European countries (2). In 2006, several W. sinensis plants with mottling and mosaic symptoms were observed in a commercial plant nursery in Whenuapai, north of Auckland, New Zealand. These plants had been propagated from a nursery in the New Plymouth area of New Zealand. Sap from the symptomatic Wisteria plants was examined with an electron microscope and elongated and flexuous potyvirus-like particles approximately 750 nm long were observed. RNA was extracted from the symptomatic plants with a Qiagen RNeasy Plant Mini Kit (Doncaster, Australia). The RNA was initially tested using general potyvirus primers, PV1/SP6 (4) and U335 (3), with the cycling conditions of 94°C for 5 min followed by 40 cycles of 94°C for 45 s, 50°C for 45 s, 72°C for 90 s, and a final extension of 72°C for 7 min. The polymerase chain reaction (PCR) product (695 bp) was directly sequenced (GenBank Accession No. EU580146) and a BLAST search in GenBank showed 98% nucleotide identity with WVMV (GenBank Accession no. AF484549). The RNA was then tested using WVMV-specific primers, WVMVF1 and WVMVR1, and the published cycling conditions (2). PCR amplicons of 701 bp were obtained. PCR products were directly sequenced (GenBank Accession No. EU308592), and a BLAST search in GenBank showed 98% nucleotide identity with published sequences of WVMV (GenBank Accession Nos. AF484549 and AY656816). In addition, RNA was extracted from the original isolate of WVMV that was reported in the Netherlands (1; supplied by R. van der Vlugt, Plant Research International) and the RNA was amplified using the WVMV-specific primer pair. The sequence obtained from PCR amplicons of the type isolate (GenBank Accession No. EU308593) showed a 98% nucleotide identity with the New Zealand WVMV isolate and with published sequences of WVMV (as shown above). From the symptomatology, particle morphology, and nucleotide sequences, it is concluded that WVMV is present in New Zealand. The distribution of the virus in New Zealand is not known, but the affected plants at the New Plymouth nursery may have been imported into New Zealand as many as 30 years ago. Although WVMV infection can reduce the quality of commercial plants, the disease is not economically significant in New Zealand.

References: (1) L. Bos. Neth. J. Plant Pathol. 76:8, 1970. (2) G. R. G. Clover et al. Plant Pathol. 52:92, 2003. (3) S. A. Langeveld et al. J. Gen Virol. 72:1531, 1991. (4) A. M. Mackenzie et al. Arch Virol. 143:903, 1998.
Powdery Mildew Caused by Golovinomyces cichoracearum on Paris Daisy (Argyranthemum frutescens) in Italy
Authors: Garibaldi A. , Bertetti D. , Frati S. , Minuto A. , Gullino M. L.
Published: June 2008

Paris daisy (Argyranthemum frutescens), also known as Marguerite daisy, is an economically important crop in the Riviera Ligure (northern Italy) where approximately 18 million potted plants per year are produced for export. During the fall and winter of 2007, Paris daisy ‘Bright Carmen’ plants, started in a greenhouse and growing outside in a commercial nursery at Albenga, showed a previously unknown powdery mildew. Young stems, particularly in the interior portions of the plant, were covered with a white mycelium. As the disease progressed, leaves became covered with the mycelium, resulting in smaller, chlorotic leaves. Conidia were hyaline, cylindrical, borne in chains (two to three conidia per chain) and measured 30 × 12 μm (20 to 34 × 10 to 15 μm). Conidia were generated by conidiophores represented by a foot cell measuring 55 to 101 × 11 to 12 μm followed by two shorter cells measuring 19 to 29 × 11 to 14 and 24 to 33 × 12 to 14 μm. Fibrosin bodies were absent. Chasmothecia were not observed in the collected samples. The internal transcribed spacer (ITS) region of rDNA was amplified using primers ITS4/ITS6 and sequenced. BLASTn analysis (1) of the 441 bp showed a 100% homology with the sequence of Golovinomyces cichoracearum (= Erysiphe cichoracearum) (3). The nucleotide sequence has been assigned GenBank Accession No. EU486992. Pathogenicity was confirmed through inoculation by gently pressing diseased leaves onto leaves of healthy Paris daisy plants of cvs. Blazer Rose, Bright Carmine, Cherry Harmony, Crowned Rose, Fulvia, Sole Mio, Stella 2000, Summit Pink, and Sun Light. Three plants per cultivar were inoculated, while the same number served as noninoculated controls. The pathogenicity test was carried out twice. Plants were maintained in a greenhouse at temperatures ranging from 15 to 21°C. Fifteen days after inoculation, typical symptoms of powdery mildew developed on inoculated plants of all cultivars, with the exception of Stella 2000. The fungus observed on inoculated plants was morphologically identical to that originally observed. Noninoculated plants did not show symptoms. To our knowledge, this is the first report of powdery mildew on A. frutescens in Italy. G. cichoracearum has been reported on Chrysanthemum frutescens in Switzerland (2). The economic impact of this disease is limited but can easily increase because of the intensive cultivation of this crop. The availability of resistant or partially resistant cultivars will help reduce the impact of this new disease. Voucher specimens are available at the AGROINNOVA Collection, University of Torino.

References: (1) S. F. Altschul et al. Nucleic Acids Res. 25:3389, 1997. (2) A. Bolay, Cryptogam. Helv. 20:1, 2005. (3) U. Braun and S. Takamatsu. Schlechtendalia 4:1, 2000.
Canna yellow mottle virus in Canna spp. in Washington State
Authors: Pappu H. R. , Druffel K. B. , Eastwell K. C.
Published: June 2008

Canna (Canna indica) is an important nursery/landscape plant in Washington State with several nurseries producing canna plants for wholesale and retail businesses. Canna plants showing symptoms such as mottling, general yellowing, and veinal chlorosis were found to be widespread (40% symptomatic plants in a nursery of more than 2,000 plants) in Grant County, WA in September 2007. Symptomatic leaves from five plants of each of the following cultivars were tested: Richard Wallace, Crimson Beauty, Wyoming, Petoria, Pink Beauty, Robert Kemp, and Black Knight. Electron microscopic examination of leaf-dip preparations from symptomatic leaves showed badnavirus-like particles of approximately 120 × 30 nm. A badnavirus, Canna yellow mottle virus (CaYMV) (family Caulimoviridae, genus Badnavirus) from canna was first reported from Japan (4) and later in the United States (1,3). Most recently, CaYMV was reported from Italy and the Netherlands (2). Samples were tested for CaYMV by PCR using CaYMV-specific primers, CaYMV-3 (5′- GAC TTC CTG GGT GCA ACA AT -3′) and CaYMV-4 (5′- TCT GTG CAA TCT TGG CGT AG -3′) (2), which produced a 565-bp amplicon. All samples tested gave the amplicon of expected size. The amplicon from one leaf sample from each of the cultivars was cloned and sequenced. Sequence comparisons with those available in the GenBank confirmed that the sequence obtained was that of CaYMV (95% sequence identity). Increased awareness of the prevalence of CaYMV in nurseries and avoiding the propagation and distribution of infected plants are necessary to minimize the further spread of this virus in canna.

References: (1) B. E. L. Lockhart. Acta Hortic. 234:69, 1988. (2) M. T. Marino et al. Online publication. New Disease Reports. http://www.bspp.org.uk/NDR/july2007/2007-08.asp , 2007. (3) M. T. Momol et al. Online publication. doi:10.1094/PHP-2004-0809-01-HN. Plant Health Progress, 2004. (4) S. Yamashita et al. Ann. Phytopathol. Soc. Jpn. 51:642, 1985.
First Report of Lasiodiplodia Fruit Rot of Jackfruit in Taiwan
Authors: Ni H. F. , Chen R. S. , Chang S. F. , Yang H. R.
Published: June 2008

Jackfruit (Artocarpus heterophyllus Lam.) is a tropical fruit that is native to India. Five diseases, including Rhizopus fruit rot and anthracnose fruit rot, have been recorded in Taiwan (2). In 2003, brown lesions were observed on mature or harvested fruits at the Chiayi Agricultural Experiment Branch. The disease caused fruits to collapse and was easily distinguished from anthracnose and Rhizopus fruit rot. In the field, Rhizopus fruit rot was characterized by black flocci sporangia and mycelia covering the flowers and young fruits. Lasiodiplodia fruit rot often occurred on mature or wounded fruit and diseased fruit were covered with gray or black flat mycelia under humid conditions. In the early stage of Lasiodiplodia fruit rot, tiny yellow-brown lesions appeared on the peel. The lesions could rapidly expand to 10 cm in diameter within 5 days and became dark brown with a light margin. The rot symptoms progressed quickly from the peel surface into the sarcocarps that eventually turned black and soft. A fungus was isolated from the margin of the lesions and cultured on acidified potato dextrose agar (PDA) (pH 3.8). The morphology of the fungus was similar to Lasiodiplodia theobromae (Pat.) Griff. & Maubl. (synonym Botryodiplodia theobromae Pat.), which causes the stem-end rot of mango, papaya, and banana in Taiwan. The fungus grew well and produced pycnidia and conidia on PDA. Young conidia were ovate, hyaline, and thin walled without septa. Mature conidia (20 to 28 × 12 to 15 μm) were dark brown and thick walled with one median septum and longitudinal striations. The internal transcribed spacer (ITS) sequence of ribosomal DNA of this fungus was submitted to GenBank (Accession No. EU 407235) and showed 100% sequence identity with that of Botryosphaeria rhodina (anamorph Lasiodiplodia theobromae; GenBank Accession No. DQ458890). On the basis of morphological and molecular criteria, the fungus was identified as L. theobromae (1). Three healthy jackfruit fruits were wounded and inoculated with 2 × 2 mm mycelial agar plugs of the fungus from a monoconidial culture. A sterile agar plug was placed on the wounded site as a control. The fruits were kept in a box to maintain high humidity for 2 days at room temperature. Brown lesions were observed on all inoculated sites 6 days post infection. The pathogen was reisolated from the lesions of inoculated fruits, fulfilling Koch's postulate. The experiment was repeated twice. To our knowledge, this is the first report of L. theobromae causing fruit rot of jackfruit in Taiwan.

References: (1) B. C. Sutton. The Coelomycetes. Commonwealth Mycological Institute, Kew, UK, 1980. (2) Y. P. Tsai, ed. List of Plant Diseases in Taiwan. 4th ed. Taiwan Phytopathological Society, 2002.
First Report of Peach latent mosaic viroid in Peach Trees in Argentina
Authors: Nieto A. M. , Di Feo L. , Nome C. F.
Published: June 2008

Peach trees (Prunus persica L.) with yellowing symptoms on leaves were found in December (summer season) of 2005 in commercial fields in Colonia Caroya, Córdoba, Argentina. This symptom resembled Peach latent mosaic viroid (PLMVd). The viroid-affected trees usually showed vein banding and yellowing symptoms on leaves, fruit suture splitting, delays in budding, flowering and fruit ripening, reduced foliage density, and a spindly appearance. PLMVd is mainly transmitted by the propagation of infected budwood and to a lesser extent by pruning tools and aphids (1). Extraction and partial purification of nucleic acids was made from symptomatic leaves (2) collected during the indicated summer season from seven peach trees from commercial plots. Preliminary identification of the viroid was made by dot-blot hybridization with a PLMVd probe (provided by R. Flores). The positive plants were tested also by reverse transcription (RT)-PCR with PLMVd primers RF-43 (5′-CTGGATCACACCCCCCTCGGAACCAACCGCT-3′) and RF-44 (5′-TGTGATCCAGGTACCGCCGTAGAAACT-3′), which amplify the complete genome. All identified positive samples yielded the correct sized PCR product and four were cloned and sequenced. This local sequence (GenBank Accession No. EU429320) had 97% nucleotide sequence identity with a reported PLMVd sequence (GenBank Accession No. M83545), confirming the identity of the local pathogen as Peach latent mosaic viroid. This result suggests that the source of the pathogen may have been infected budwood introduced from Europe. To our knowledge, this is the first report of this viroid in Argentina.

References: (1) R. Flores et al. Mol. Plant Pathol. 7:209, 2006. (2) V. Pallás et al. J. Gen. Virol. 68:3201, 1987.
Frequency of Sexual Recombination by Mycosphaerella graminicola in Mild and Severe Epidemics
Authors: Cowger C. , Brunner P. C. , Mundt C. C.
Published: June 2008

The importance of sexual recombination in determining fungal population structure cannot be inferred solely from the relative abundance of sexual and asexual spores and reproductive structures. To complement a previously reported study of proportions of Mycosphaerella graminicola ascocarps and pycnidia, we investigated the share of sexual recombinants among isolates randomly derived from the same field at the same time. Early in three successive growing seasons (those ending in 1998, 1999, and 2000), field plots of the susceptible winter wheat cultivar Stephens were inoculated with suspensions of two M. graminicola isolates that each had rare alleles at restriction fragment length polymorphism (RFLP) loci. Near harvest time, leaves were randomly sampled from the same plots, and a population of over 100 monopycnidial isolates was created for each year of the experiment. Natural populations were also sampled from noninoculated plots in the 1999 and 2000 seasons, in order to compare allele frequencies. Based on RFLP haplotypes and DNA fingerprints, isolates from the inoculated plots were categorized by both inspection and Bayesian methods as inoculant clones, recombinants, or immigrants. Inoculation in the 2000 season was delayed, and the recovery rate of inoculant types was just 1 to 2%. In 1998, a high-disease year, and 1999, a low-disease year, inoculants comprised 36 and 22 to 23% of end-of-season samples, respectively. In those 2 years, recombinants as a percentage of inoculant descendants (both sexual and asexual) were 35 and 32%, respectively. By comparison, the study of fruiting bodies had found 93 and 32% of M. graminicola fruiting bodies were ascocarps in 1998 and 1999, respectively. These findings support the hypothesis that sexual recombination makes a relatively consistent contribution to M. graminicola population structure, despite differences in epidemic severity and ascocarp proportions.
Localized Adhesion of Nongerminated Venturia inaequalis Conidia to Leaves and Artificial Surfaces
Authors: Schumacher C. F. A. , Steiner U. , Dehne H.-W. , Oerke E.-C.
Published: June 2008

Adhesion to the host surface is the first step for successful plant pathogen development and has been reported to be associated with both passive and active processes. For conidia of Venturia inaequalis, which depend on leaf wetness for germination, this process has not yet been described. Conidia of V. inaequalis adhered to wet hydrophobic surfaces immediately after contact to the surface, hours before initiation of germination. Attachment of nongerminated conidia was much better on hydrophobic surfaces, such as apple leaves and polystyrene, than on hydrophilic glass. Conidia released adhesive material localized in a droplet named spore tip glue (STG) at the spore apex which interacted with a contact surface only when water was present. Histochemical investigations indicated the presence of proteins and carbohydrates in STG, lectin labeling the presence of β-galactose and N-acetylglucosaminyl residues. Transmission electron microscopy revealed two phases in the STG at the tip of dry mature conidia; as STG was present on the outer side of the intact fungal cell wall its formation should be associated with the secretion of glue through pores of the conidial wall. Surface-active substances affected the adhesion of conidia to hydrophobic surfaces stressing the importance of hydrophobic interactions. The use of protein biosynthesis inhibitors did not affect adhesion of conidia indicating that the adhesive material was preformed. It is concluded that the coincidence of STG, contact to a hydrophobic surface, and free water are essential for the adhesion of V. inaequalis conidia.
Cloning and Characterization of the Antigenic Membrane Protein (Amp) Gene and In Situ Detection of Amp from Malformed Flowers Infected with Japanese Hydrangea Phyllody Phytoplasma
Authors: Arashida R. , Kakizawa S. , Ishii Y. , Hoshi A. , Jung H.-Y. , Kagiwada S. , Yamaji Y. , Oshima K. , Namba S.
Published: June 2008

A Japanese hydrangea phyllody (JHP) disease found throughout Japan causes economic damage to the horticultural industry. JHP phytoplasma-infected Japanese hydrangea plants show several disease symptoms involved in floral malformations, such as virescence, phyllody and proliferation. Here, we cloned and characterized the antigenic membrane protein (Amp) gene homolog from the JHP phytoplasma (JHP-amp), expressed the JHP-Amp protein in Escherichia coli cells, and then obtained an antibody against JHP-Amp. The antibody against JHP-Amp had no cross-reactions with the antibody against the Amp protein from a closely related onion yellows phytoplasma. This serologic specificity is probably due to the high diversity of the hydrophilic domains in the Amp proteins. The in situ detection of the JHP-Amp protein revealed that the JHP phytoplasma was localized to the phloem tissues in the malformed flower. This study shows that the JHP-Amp protein is indeed a membrane protein, which is expressed at detectable level in the JHP phytoplasma-infected hydrangea.
Identification of Specific Fragments of HpaGXooc, a Harpin from Xanthomonas oryzae pv. oryzicola, that Induce Disease Resistance and Enhance Growth in Plants
Authors: Chen Lei , Qian Jun , Qu Shuping , Long Juying , Yin Qian , Zhang Chunling , Wu Xiaojing , Sun Feng , Wu Tingquan , Hayes Marshall , Beer Steven V. , Dong Hansong
Published: June 2008

Harpin proteins from gram-negative plant-pathogenic bacteria can stimulate hypersensitive cell death (HCD) and pathogen defense as well as enhance growth in plants. Two of these diverse activities clearly are beneficial and may depend on particular functional regions of the proteins. Identification of beneficial and deleterious regions might facilitate the beneficial use of harpin-related proteins on crops without causing negative effects like cell death. Here, we report the identification and testing of nine functional fragments of HpaGXooc, a 137-amino-acid harpin protein from Xanthomonas oryzae pv. oryzicola, the pathogen that causes bacterial leaf streak of rice. Polymerase chain reaction-based mutagenesis generated nine proteinaceous fragments of HpaGXooc; these caused different responses following their application to Nicotiana tabacum (tobacco) and Oryza sativa (rice). Fragment HpaG62-137, which spans the indicated amino acid residues of the HpaG, induced more intense HCD; in contrast, HpaG10-42 did not cause evident cell death in tobacco. However, both fragments stimulated stronger defense responses and enhanced more growth in rice than the full-length parent protein, HpaGXooc. Of the nine fragments, the parent protein and one deletion mutant of HpaGXooc tested, HpaG10-42, stimulated higher levels of rice growth and resulted in greater levels of resistance to X. oryzae pv. oryzae and Magnaporthe grisea. These pathogens cause bacterial leaf blight and rice blast, respectively, the two most important diseases of rice world-wide. HpaG10-42 was more active than HpaGXooc in inducing expression of several genes that regulate rice defense and growth processes and activating certain signaling pathways, which may explain the greater beneficial effects observed from treatment with that fragment. Overall, our results suggest that HpaG10-42 holds promise for practical agricultural use to induce disease resistance and enhance growth of rice.
A Fragment of the Xanthomonas oryzae pv. oryzicola Harpin HpaGXooc Reduces Disease and Increases Yield of Rice in Extensive Grower Plantings
Authors: Chen Lei , Zhang Shu-Jian , Zhang Shao-Song , Qu Shuping , Ren Xiuyan , Long Juying , Yin Qian , Qian Jun , Sun Feng , Zhang Chunling , Wang Lingxian , Wu Xiaojing , Wu Tingquan , Zhang Zhongkai , Cheng Zaiquan , Hayes Marshall , Beer Steven V. , Dong Hansong
Published: June 2008

Harpins of phytopathogenic bacteria stimulate defense and plant growth in many types of plants, conferring disease resistance and enhanced yield. In a previous study, we characterized nine fragments of the harpin protein HpaGXooc from Xanthomonas oryzae pv. oryzicola for plant defense elicitation and plant growth stimulation activity relative to the intact protein. In plants grown under controlled conditions, the fragment HpaG10-42 was more active in both regards than HpaGXooc. Here, we demonstrate that the activity of HpaG10-42 in rice under field conditions significantly exceeds that of HpaGXooc, stimulating resistance to three important diseases and increasing grain yield. We carried out tests in 672 experimental plots with nine cultivars of rice planted at three locations. Application protocols were optimized by testing variations in application rate, frequency, and timing with respect to rice growth stage. Of the concentrations (24, 24, 12, and 6 μg/ml), and number and timing of applications (at one to four different stages of growth) tested, HpaG10-42 at 6 μg/ml applied to plants once at nursery seedling stage and three times in the field was most effective. Bacterial blight, rice blast, and sheath blight were reduced 61.6 and 56.4, 93.6 and 76.0, and 93.2 and 55.0% in indica and japonica cultivars, respectively, relative to controls. Grain yields were 22 to 27% greater. These results are similar to results obtained with typical local management practices, including use of chemicals, to decrease disease severities and increase yield in rice. Our results demonstrate that the HpaG10-42 protein fragment can be used effectively to control diseases and increase yield of this staple food crop.
Quantitative Trait Loci for High-Temperature Adult-Plant and Slow-Rusting Resistance to Puccinia striiformis f. sp. tritici in Wheat Cultivars
Authors: Guo Q. , Zhang Z. J. , Xu Y. B. , Li G. H. , Feng J. , Zhou Y.
Published: June 2008

Stripe rust, caused by Puccinia striiformis f. sp. tritici, is one of the most damaging diseases of wheat (Triticum aestivum) globally. High-temperature adult-plant resistance (HTAPR) and slow-rusting have great potential for sustainable management of the disease. The wheat cultivars Luke and Aquileja have been previously reported to possess HTAPR and slow-rusting to stripe rust, respectively. Aquileja displayed less number of stripes per unit leaf area than Luke, while Luke showed lower infection type than Aquileja at adult-plant stages of growth under high-temperature conditions. The objectives of this study were to confirm the resistances and to map the resistance genes in Luke and Aquileja. Luke was crossed with Aquileja, and 326 of the F2 plants were genotyped using 282 microsatellite primer pairs. These F2 plants and their derived F3 families were evaluated for resistance to stripe rust by inoculation in the fields and greenhouses of high- and low-temperatures. Infection type was recorded for both seedlings and adult plants, and stripe number was recorded for adult plants only. Two quantitative trait loci (QTL) were identified, on the short arm of chromosome 2B, to be significantly associated with infection type at adult-plant stages in the fields and in the high-temperature greenhouse. The locus distal to centromere, referred to as QYrlu.cau-2BS1, and the locus proximal to centromere, referred to as QYrlu.cau-2BS2, were separated by a genetic distance of about 23 cM. QYrlu.cau-2BS1 was flanked by the microsatellite markers Xwmc154 and Xgwm148, and QYrlu.cau-2BS2 was flanked by Xgwm148 and Xabrc167. QYrlu.cau-2BS1 and QYrlu.cau-2BS2 explained up to 36.6 and 41.5% of the phenotypic variation of infection type, respectively, and up to 78.1% collectively. No significant interaction between the two loci was detected. Another QTL, referred to as QYraq.cau-2BL, was detected on the long arm of chromosome 2B to be significantly associated with stripe number. QYraq.cau-2BL was flanked by the microsatellite markers Xwmc175 and Xwmc332, and it explained up to 61.5% of the phenotypic variation of stripe number. It is possible that these three QTL are previously unmapped loci for resistance to stripe rust.
In Vitro Analysis of the Interaction ofPseudomonas savastanoipvs.savastanoiandneriiwith Micropropagated Olive Plants
Authors: Rodríguez-Moreno Luis , Barceló-Muñoz Araceli , Ramos Cayo
Published: June 2008

This study assessed the use of in vitro olive plants to evaluate the virulence of Pseudomonas savastanoi pv. savastanoi strains isolated from olive and P. savastanoi pv. nerii strains isolated from oleander knots. First, different olive isolates were inoculated into stem wounds and differences in knot formation and weight of overgrowths were observed for the selected strains. Tissue proliferation was clearly visible in all inoculated plants 30 days after inoculation. Virulence of P. savastanoi pv. nerii mutants with defects in regard to biosynthesis of indole-3-acetic acid and/or cytokinins was tested using this system. In agreement with data previously reported, all mutant strains multiplied in olive but induced attenuated symptoms. To analyze the virulence of P. savastanoi pv. savastanoi affected in their ability to grow in olive tissue, a trpE tryptophan auxotroph mutant was generated using a collection of signature tagged mutagenesis transposons. Virulence of this mutant was clearly reduced as evidenced by swelling of the olive tissue that evolved into attenuated knots. Furthermore, mixed infections with its parental strain revealed that the wild-type strain completely out-competed the trpE mutant. Results shown here demonstrate the usefulness of in vitro olive plants for the analysis of P. savastanoi pvs. savastanoi and nerii virulence. In addition, this system offers the possibility of quantifying virulence differences as weight of overgrowths. Moreover, we established the basis for the use of mixed infections in combination with signature tagged mutagenesis for high-throughput functional genomic analysis of this bacterial pathogen.
Population Structure of Cercospora kikuchii, the Causal Agent of Cercospora Leaf Blight and Purple Seed Stain in Soybean
Authors: Cai G. , Schneider R. W.
Published: June 2008

Random amplified polymorphic DNA (RAPD) and microsatellite-primed polymerase chain reaction (MP-PCR) were used to characterize 164 isolates of Cercospora kikuchii, most of which were collected from Louisiana. Plant tissue (seeds versus leaves), but not host cultivar, had a significant impact on pathogen population differentiation. Cluster analysis showed that the Louisiana population was dominated by a primary lineage (group I) with only a few Louisiana isolates belonging to the minor lineage that also included the non-Louisiana isolates (group II). A previous study showed that isolates could be differentiated according to vegetative compatibility groups (VCGs). However, RAPD and MP-PCR data demonstrated that isolates of C. kikuchii were not generally clustered according to these VCGs. Furthermore, genetic relationships within and between VCGs were examined using sequences of the intergenic spacer region of rDNA. These analyses showed that VCG is not an indicator of evolutionary lineage in this fungus. Our results suggest the likely existence of a cryptically functioning sexual stage in some portion of the C. kikuchii population.
Evidence of Induced Systemic Resistance Against Botrytis elliptica in Lily
Authors: Liu Yi-Hung , Huang Chien-Jui , Chen Chao-Ying
Published: June 2008

Lily leaf blight, caused by Botrytis elliptica, is an important fungal disease in Taiwan. In order to identify an effective, nonfungicide method to decrease disease incidence in Lilium formosanum, the efficacy of rhizobacteria eliciting induced systemic resistance (ISR) was examined in this study. Over 300 rhizobacteria were isolated from the rhizosphere of L. formosanum healthy plants and 63 were identified by the analysis of fatty acid profiles. Disease suppressive ability of 13 strains was demonstrated by soil drench application of bacterial suspensions to the rhizosphere of L. formosanum seedlings. Biocontrol experiments were carried out with Bacillus cereus and Pseudomonas putida strains on L. formosanum and Lilium Oriental hybrid cvs. Acapulco and Star Gazer in greenhouse and field studies. Plants treated with B. cereus strain C1L showed that protection against B. elliptica on L. formosanum could last for at least 10 days and was consistent with high populations of B. cereus on lily roots. Analysis of the expression of LfGRP1 and LsGRP1, encoding glycine-rich protein associated with L. formosanum and cv. Star Gazer, respectively, revealed different responses induced by B. cereus or by the pathogen B. elliptica, suggesting that plant defense responses elicited by each follows a different signaling pathway. According to the results of biocontrol assays and LfGRP1/LsGRP1 gene expression analyses with culture filtrates of B. cereus strain C1L, we propose that eliciting factors of ISR are generated by B. cereus and some of them exhibit thermostable and heat-tolerant traits. This is the first report about ISR-eliciting rhizobacteria and factors effective for foliar disease suppression in lily.
Identification and Quantification of Rhizoctonia solani and R. oryzae Using Real-Time Polymerase Chain Reaction
Authors: Okubara P. A. , Schroeder K. L. , Paulitz T. C.
Published: June 2008

Rhizoctonia solani and R. oryzae are the principal causal agents of Rhizoctonia root rot in dryland cereal production systems of the Pacific Northwest. To facilitate the identification and quantification of these pathogens in agricultural samples, we developed SYBR Green I-based real-time quantitative-polymerase chain reaction (Q-PCR) assays specific to internal transcribed spacers ITS1 and ITS2 of the nuclear ribosomal DNA of R. solani and R. oryzae. The assays were diagnostic for R. solani AG-2-1, AG-8, and AG-10, three genotypes of R. oryzae, and an AG-I-like binucleate Rhizoctonia species. Quantification was reproducible at or below a cycle threshold (Ct) of 33, or 2 to 10 fg of mycelial DNA from cultured fungi, 200 to 500 fg of pathogen DNA from root extracts, and 20 to 50 fg of pathogen DNA from soil extracts. However, pathogen DNA could be specifically detected in all types of extracts at about 100-fold below the quantification levels. Soils from Ritzville, WA, showing acute Rhizoctonia bare patch harbored 9.4 to 780 pg of R. solani AG-8 DNA per gram of soil.. Blastn, primer-template duplex stability, and phylogenetic analyses predicted that the Q-PCR assays will be diagnostic for isolates from Australia, Israel, Japan, and other countries.
Potential Threat of a New Pathotype ofPapaya leaf distortion mosaic virusInfecting Transgenic Papaya Resistant toPapaya ringspot virus
Authors: Bau H.-J. , Kung Y.-J. , Raja J. A. J. , Chan S.-J. , Chen K.-C. , Chen Y.-K. , Wu H.-W. , Yeh S.-D.
Published: June 2008

A virus identified as a new pathotype of Papaya leaf distortion mosaic virus (PLDMV, P-TW-WF) was isolated from diseased papaya in an isolated test-field in central Taiwan, where transgenic papaya lines resistant to Papaya ringspot virus (PRSV) were evaluated. The infected plants displayed severe mosaic, distortion and shoe-stringing on leaves; stunting in apex; and water-soaking on petioles and stems. This virus, which did not react in enzyme-linked immunosorbent assay with the antiserum to the PRSV coat protein, infected only papaya, but not the other 18 plant species tested. Virions studied under electron microscope exhibited morphology and dimensions of potyvirus particles. Reverse transcription-polymerase chain reaction conducted using potyvirus-specific primers generated a 1,927-nucleotide product corresponding to the 3′ region of a potyvirus, showing high sequence identity to the CP gene and 3′ noncoding region of PLDMV. Search for similar isolates with the antiserum against CP of P-TW-WF revealed scattered occurrence of PLDMV in Taiwan. Phylogenetic analysis of PLDMV isolates of Taiwan and Japan indicated that the Taiwan isolates belong to a separate genetic cluster. Since all the Taiwan isolates infected only papaya, unlike the cucurbit-infecting Japanese P type isolates, the Taiwan isolates are considered a new pathotype of PLDMV. Susceptibility of all our PRSV-resistant transgenic papaya lines to PLDMV indicates that the virus is an emerging threat for the application of PRSV-resistant transgenic papaya in Taiwan and elsewhere.
Perception of musical consonance and dissonance: an outcome of neural synchronization
Authors: Shapira Lots Inbal , Stone Lewi
Published: June 2008

While a number of theories have been advanced to account for why musical consonance is related to simple frequency ratios, as yet there is no completely satisfying explanation. Here, we explore the theory of synchronization properties of ensembles of coupled neural oscillators to demonstrate why simple frequency ratios may have achieved a special status and why they are important for auditory perception. The analysis shows that the mode-locked states ordering give precisely the standard ordering of consonance as often listed in Western music theory. Our results thus indicate the importance of neural synchrony in musical perception.
Jaw protrusion enhances forces exerted on prey by suction feeding fishes
Authors: Holzman Roi , Day Steven W , Mehta Rita S , Wainwright Peter C
Published: June 2008

The ability to protrude the jaws during prey capture is a hallmark of teleost fishes, widely recognized as one of the most significant innovations in their diverse and mechanically complex skull. An elaborated jaw protrusion mechanism has independently evolved multiple times in bony fishes, and is a conspicuous feature in several of their most spectacular radiations, ultimately being found in about half of the approximately 30 000 living species. Variation in jaw protrusion distance and speed is thought to have facilitated the remarkable trophic diversity found across fish groups, although the mechanical consequences of jaw protrusion for aquatic feeding performance remain unclear. Using a hydrodynamic approach, we show that rapid protrusion of the jaws towards the prey, coupled with the spatial pattern of the flow in front of the mouth, accelerates the water around the prey. Jaw protrusion provides an independent source of acceleration from that induced by the unsteady flow at the mouth aperture, increasing by up to 35% the total force exerted on attached, escaping and free-floating passive prey. Despite initiating the strike further away, fishes can increase peak force on their prey by protruding their jaws towards it, compared with a ‘non-protruding’ state, where the distance to prey remains constant throughout the strike. The force requirements for capturing aquatic prey might have served as a selective factor for the evolution of jaw protrusion in modern fishes.
A simple modification of the Hodgkin and Huxley equations explains type 3 excitability in squid giant axons
Authors: Clay John R , Paydarfar David , Forger Daniel B
Published: June 2008

The Hodgkin and Huxley (HH) model predicts sustained repetitive firing of nerve action potentials for a suprathreshold depolarizing current pulse for as long as the pulse is applied (type 2 excitability). Squid giant axons, the preparation for which the model was intended, fire only once at the beginning of the pulse (type 3 behaviour). This discrepancy between the theory and experiments can be removed by modifying a single parameter in the HH equations for the K+current as determined from the analysis in this paper. K+currents in general have been described byIK=gK(V−EK), wheregKis the membrane's K+current conductance andEKis the K+Nernst potential. However,IKhas a nonlinear dependence on (V−EK) well described by the Goldman–Hodgkin–Katz equation that determines the voltage dependence ofgK. This experimental finding is the basis for the modification in the HH equations describing type 3 behaviour. Our analysis may have broad significance given the use ofIK=gK(V−EK) to describe K+currents in a wide variety of biological preparations.
The liquid blister test
Authors: Chopin Julien , Vella Dominic , Boudaoud Arezki
Published: June 2008

We consider a thin elastic sheet adhering to a stiff substrate by means of the surface tension of a thin liquid layer. Debonding is initiated by imposing a vertical displacement at the centre of the sheet and leads to the formation of a delaminated region or ‘blister’. This experiment reveals that the perimeter of the blister takes one of three different forms depending on the vertical displacement imposed. As this displacement is increased, we observe first circular, then undulating and finally triangular blisters. We obtain theoretical predictions for the observed features of each of these three families of blisters. The theory is built upon the Föppl–von Kármán equations for thin elastic plates and accounts for the surface energy of the liquid. We find good quantitative agreement between our theoretical predictions and experimental results, demonstrating that all three families are governed by different balances between elastic and capillary forces. Our results may bear on micrometric tapered devices and other systems, where elastic and adhesive forces are in competition.
The method of separation of variables for solving equations describing molecular-motor-assisted transport of intracellular particles in a dendrite or axon
Authors: Kuznetsov A.V , Avramenko A.A
Published: June 2008

This paper presents an analytical solution of one-dimensional transient molecular-motor-assisted transport equations that describe transport of different organelles (such as transport vesicles loaded with a cargo of specific proteins) in a neuron's axon or dendrite. Large intracellular organelles are transported in the cytoplasm by a combined action of diffusion and motor-driven transport. In an axon, organelles are transported away from the neuron's body towards the axon's terminal by kinesin-family molecular motors running on tracks composed of microtubules (MTs); old and used components are carried back towards the neuron's body by dynein-family molecular motors. Using the method of separation of variables, a generalized Fourier series solution for this problem is obtained. The solution uses three different orthogonal sets of eigenfunctions to represent the concentration of free organelles transported by diffusion, MT-bound organelles transported away from the neuron's body, and MT-bound organelles transported towards the neuron's body. Binding/detachment kinetic processes between the organelles and the MT are specified by first-order rate constants; these lead to coupling between the three organelle concentrations.
Niche expansion leads to small-scale adaptive divergence along an elevation gradient in a medium-sized passerine bird
Authors: McCormack John E , Smith Thomas B
Published: June 2008

Niche expansion can lead to adaptive differentiation and speciation, but there are few examples from contemporary niche expansions about how this process is initiated. We assess the consequences of a niche expansion by Mexican jays (Aphelocoma ultramarina) along an elevation gradient. We predicted that jays at high elevation would have straighter bills adapted to feeding on pine cones, whereas jays at low elevation would have hooked bills adapted to feeding on acorns. We measured morphological and genetic variation of 95 adult jays and found significant differences in hook length between elevations in accordance with predictions, a pattern corroborated by analysis at the regional scale. Genetic results from microsatellite and mtDNA variation support phenotypic differentiation in the presence of gene flow coupled with weak, but detectable genetic differentiation between high- and low-elevation populations. These results demonstrate that niche expansion can lead to adaptive divergence despite gene flow between parapatric populations along an elevation gradient, providing information on a key precursor to ecological speciation.
Does face image statistics predict a preferred spatial frequency for human face processing?
Authors: Keil Matthias S
Published: June 2008

Psychophysical experiments suggested a relative importance of a narrow band of spatial frequencies for recognition of face identity in humans. There exists, however, no conclusive evidence of why it is that such frequencies are preferred. To address this question, I examined the amplitude spectra of a large number of face images and observed that face spectra generally fall off more steeply with spatial frequency compared with ordinary natural images. When external face features (such as hair) are suppressed, then whitening of the corresponding mean amplitude spectra revealed higher response amplitudes at those spatial frequencies which are deemed important for processing face identity. The results presented here therefore provide support for that face processing characteristics match corresponding stimulus properties.