bluuebunny/crossref_metadata_2025 huggingface dataset:
Survival of Sporangia of New Clonal Lineages of Phytophthora infestans in Soil Under Semiarid Conditions
Authors: Porter L. D. , Johnson D. A.
Published: June 2007

Currently, there is no information on the viability of sporangia in soil of the new metalaxyl-resistant genotypes of Phytophthora infestans in the semiarid Columbia Basin of Washington and potato-growing regions throughout the world. Sporangia of metalaxyl-resistant US-8 and US-11 clonal lineages of P. infestans survived a maximum of 23 to 30 days in a Shano silt loam and a Quincy loamy fine sand. There were no significant differences between soil types in area under the spore survival curve (AUSSC) in two trials, however, sporangia of P. infestans in the Quincy sand had a significantly greater mean maximum days of sporangia survival (MDSS) than did the Shano silt loam in one of two trials. AUSSC and MDSS were significantly greater (P < 0.05) for sporangia in wet soil than in dry soil under shaded conditions. Mean AUSSC and MDSS significantly decreased (P < 0.01) under nonshaded conditions versus shaded conditions. Three metalaxyl-resistant isolates (two US-8 and one US-11) of P. infestans did not significantly differ (P < 0.05) in AUSSC and MDSS.
Overwintering Viruliferous Frankliniella occidentalis (Thysanoptera: Thripidae) as an Infection Source of Tomato spotted wilt virus in Green Pepper Fields
Authors: Okazaki Shinichiro , Okuda Mitsuru , Komi Kazuhiro , Yoshimatsu Hideaki , Iwanami Toru
Published: June 2007

Populations of overwintering viruliferous Frankliniella occidentalis were evaluated in Tomato spotted wilt virus (TSWV)-affected green pepper fields in Bungo-Ohno City, Oita Prefecture, Japan. A survey of TSWV-infected weeds showed that the incidence of infection was low in weeds. Stellaria aquatica was infected frequently; however, the infections were considered secondary cases since S. aquatica appeared in the fields around late February to early March. In contrast, TSWV was frequently detected from green pepper fruits until they rotted. F. occidentalis primarily inhabited and reproduced on the green pepper fruits and moved to Lamium amplexicaule when the fruits rotted and subsequently spread to other weed species as young shoots or flowers appeared. The flying activity level of F. occidentalis rose in late February, and viruliferous F. occidentalis transmitted TSWV to green pepper plants. We concluded that TSWV-infected green pepper fruits discarded in greenhouses and fields are the major source of infection.
A Leaf Spot and Blight of Greenhouse Tomato Seedlings Incited by a Herbaspirillum sp.
Authors: Obradovic Aleksa , Jones Jeffrey B. , Minsavage Gerald V. , Dickstein Ellen R. , Momol Timur M.
Published: June 2007

A leaf spot and blighting were observed on leaves of tomato transplants from a producer in Florida in 2001 and 2002. A nonfluorescent bacterium was isolated consistently from affected tissue. The typical bacterium was a gram negative, strictly aerobic, slightly curved rod with one or two flagella. Sequence analysis of the 16S rRNA indicated that two representative strains, F1 and SE1, had greater than 99% nucleotide sequence identity with Herbaspirillum huttiense and H. rubrisubalbicans. The cellular fatty acid composition of the total of 16 tomato strains was very similar to H. huttiense and H. rubrisubalbicans. Based on carbon utilization, six of nine strains tested with the Biolog system were identified as Herbaspirillum spp. The tomato strains were oxidase positive and grew at 40°C, but were negative for levan production, pectate hydrolysis, and arginine dihydrolase activity. Based upon this polyphasic analysis, we concluded that the strains were most closely related to H. huttiense, although placement in this species would require further analyses. However, the tomato strains and H. rubrisubalbicans, but not H. huttiense, caused confluent necrosis when infiltrated at high concentrations into tomato leaves and were able to produce leaf spot symptoms on inoculated tomato seedlings in the greenhouse. Using pulsed-field gel electrophoresis, we determined that there was considerable variability between the strains collected in 2001 and 2002.
Consideration of Nonparametric Approaches for Assessing Genotype-by-Environment (G × E) Interaction with Disease Severity Data
Authors: Madden L. V. , Paul P. A. , Lipps P. E.
Published: June 2007

Determination of host genotype-by-environment (G × E) interaction is needed to assess the stability of cultivar traits such as plant disease resistance and to reveal differences in aggressiveness or virulence of pathogen strains among locations. Here we explored the use of rank-based methodology to quantify the concordance (or discordance) of disease responses of host genotypes across environments, based on the Kendall coefficient of concordance (W) and ancillary test statistics, in order to determine the extent to which environment affected rankings of genotypes. An analysis of four data sets for disease severity of gray leaf spot of maize (with genotypes planted in as many as 11 locations in a given year) revealed highly significant concordance (P ≤ 0.001) overall, indicating that genotypes varied little in within-environment rankings. This suggests that the G × E interaction was small or nonexistent (in terms of rankings). A novel rank-based method by Piepho was evaluated to further elucidate the interaction (if any) through a test for variance homogeneity. The Piepho test statistic was not significant (P > 0.25) for any of the gray leaf spot data sets, confirming the stability of genotypes across environments for this pathosystem; however, analysis of published data sets for other pathosystems indicated significant results. The relationship shown by Hühn, Lotito, and Piepho between the ratio of genotype and residual variances of the original data and the rank-based W statistic was evaluated using Monte Carlo simulations. A more general functional relationship was developed that is applicable over a wide range of number of genotypes and environments in the analyzed studies. This confirms previously shown linkages between rankings of genotypes within environments and variability in the original (unranked) data, thus permitting ease of interpretation of parametric and nonparametric results.
Banana streak virus Identified for the First Time in Peru in Cavendish Banana (Musa AAA)
Authors: Pasberg-Gauhl C. , Lockhart B. E. L. , Castro-Mendivil Dibos F. , Rojas Llanque J. C.
Published: June 2007

In October of 2005, a field survey was done in the province of Piura in northern Peru to determine the cause of a disease known locally as “mosaico” that was affecting organic Cavendish banana (Musa AAA) grown for the export market. Disease symptoms consisted of pronounced chlorotic and necrotic lesions on leaves of affected plants. Twenty-four farms were visited, and at each location, 10 randomly selected plants at flowering stage were evaluated for disease incidence and severity. Plants showing virus-like symptoms were observed in 18 of the 24 locations (75%). Fifty-two banana leaf samples, 27 from plants showing virus-like symptoms and 25 from asymptomatic plants, were tested for the presence of Banana streak virus (BSV), Cucumber mosaic virus (CMV), and Banana mild mosaic virus (BanMMV) by immunosorbent electron microscopy (ISEM) using partially purified leaf tissue extracts (2).The same extracts were also tested by immunocapture PCR (IC-PCR) for presence of BSV and specific BSV isolates (BSV-OL, BSV-GF, BSV-IM, and BSV-CAV) using badnavirus-specific degenerate primers and BSV isolate-specific primers, respectively (1). Seventeen of 27 leaf samples showing virus-like symptoms (63%) tested positive for BSV by ISEM and IC-PCR using badnavirus, but not isolate-specific, primers. The symptoms on the 10 samples that tested negative were not typical of BSV infection. One asymptomatic leaf sample (4%) also tested positive for BSV. To validate the PCR results, the nucleotide sequence of the amplicon from a plant showing the most prevalent foliar symptom type was determined. This sequence (GenBank Accession No. DQ674317) had ≤86% homology to the corresponding ORF III polyprotein region of BSV and other badnaviruses. Neither CMV nor BanMMV was detected in any of the 52 samples tested. From these results, it was concluded that “mosaico” disease of organic Cavendish bananas in northern Peru is associated frequently with BSV infection and that there is a high incidence of BSV infection in this area. To our knowledge, this is the first report of BSV occurrence in Peru. It was both surprising and interesting that neither BSV-OL nor BSV-GF, the two BSV isolates found most commonly in banana (Musa AAA) and plantain (Musa AAB) in South and Central America (B. E. L. Lockhart, unpublished), was detected in Cavendish banana in northern Peru. Failure to detect BSV-OL and BSV-GF suggests that field infection may be due to vertical transmission by clonal propagation rather than to horizontal transmission from local plantain and that control of “mosaico” disease could therefore be achieved by use of virus-free planting material.

References: (1) A. D. W. Geering et al. Phytopathology 90:921, 2000. (2) B. E. L. Lockhart et al. Phytopathology 82:921, 1992.
Identification of Tomato yellow leaf curl virus and Tomato mottle virus in Two Counties in Alabama
Authors: Akad F. , Jacobi J. C. , Polston J. E.
Published: June 2007

During July 2005, approximately 23% of tomato plants (Solanum lycopersicum L. ‘Sebring’) in a commercial field in St. Clair County, Alabama showed symptoms of stunting, leaf deformation, mottling, and reduced leaf size, which resembled symptoms of Tomato yellow leaf curl virus (TYLCV). A high population of whiteflies (Bemisia tabaci) was observed in this field, and as the season progressed, 100% of the plants became symptomatic. During October 2006, similar symptoms in tomato were observed at low incidences (less than 10%) in a commercial greenhouse in Jefferson County. Two samples from St. Clair County and six from Jefferson County were collected and tested for the presence of a begomovirus by PCR using three pairs of primers, PAR1c496 and PAL1v1978, a degenerate primer pair designed to amplify regions of the begomovirus A component, PBL1v2040 and PCRc154, a degenerate primer pair that amplifies a hypervariable region of the begomovirus B component (3), and C473 and PTYC1v2406, which are specific to TYLCV (1,2). Primer pair PAR1c496 and PAL1v1978 produced two amplicons (1,360 and 1,159 bp) in all samples tested, which suggests the presence of a monopartite and bipartite begomovirus. Primer pair pBL1v2040 and PCRc154 produced a 678-bp amplicon that would be consistent with the presence of a bipartite begomovirus. Primer pair C473 and PTYC1v2406 produced an 850-bp amplicon that would be consistent with the presence of TYLCV. Sequence analysis revealed that the 1,360-bp amplicon had 98% sequence identity to isolates of TYLCV from Cuba (GenBank Accession No. AJ223505), the Dominican Republic (GenBank Accession No. (AF04715), Florida (GenBank Accession Nos. AF260331 and AY530931), Egypt (GenBank Accession No. AY594174), and Almeria (GenBank Accession No. AJ489258). The 1,159-bp amplicon had a 97 to 99% sequence identity to the A component of Tomato mottle virus (ToMoV) Florida (GenBank Accession Nos. L14460, EF028241, and M90495) and Puerto Rico (GenBank Accession No. AY965900). Each of the eight tomato samples were shown to be infected with TYLCV and ToMoV. Symptoms of plants infected with both viruses resembled those of TYLCV because the milder symptoms of ToMoV are masked in the field by the more severe symptoms of TYLCV. To our knowledge, this is the first report of ToMoV and TYLCV in the state of Alabama.

Reference: (1) M. Ghanim et al. Virology 240:295, 1998. (2) M. K. Nakhla et al. Phytopathol. Mediterr. 32:163, 1993. (3) M. R. Rojas et al. Plant Dis. 77:340, 1993.
Occurrence and Molecular Characterization of Squash leaf curl Phillipines virus in Taiwan
Authors: Tsai W. S. , Shih S. L. , Green S. K. , Jan F.-J.
Published: June 2007

Whitefly-transmitted, cucurbit-infecting begomoviruses (genus Begomovirus, family Geminiviridae) have been detected on cucurbit crops in Bangladesh, China, Egypt, Israel, Malaysia, Mexico, the Philippines, Thailand, United States, and Vietnam. Pumpkin plants showing leaf curling, blistering, and yellowing symptoms were observed in the AVRDC fields (Tainan, Taiwan) during 2001 and in nearby farmers' fields during 2005. Two samples from symptomatic plants were collected in 2001 and six collected in 2005. Viral DNAs were extracted (2), and the PCR, with previously described primers, was used to detect the presence of begomoviral DNA-A (4), DNA-B (3), and associated satellite DNA (1). Begomoviral DNA-A was detected in one of the 2001 samples and in all 2005 samples. The PCR-amplified 1.5 kb viral DNA-A from one positive sample each from the 2001 and 2005 collections was cloned and sequenced. On the basis of the 1.5-kb DNA-A sequences, specific primers were designed to completely sequence the DNA-A component. The overlap between fragments obtained using primer walking ranged from 43 to 119 bp with 100% nt identities. The complete DNA-A sequences were determined for the two isolates as 2,734 bp (2001) (GenBank Accession No. DQ866135) and 2,733 bp (2005) (GenBank Accession No. EF199774). Sequence comparisons and analyses were performed using the DNAMAN Sequence Analysis Software (Lynnon Corporation, Vaudreuil, Quebec, Canada). The DNA-A of the begomovirus isolates each contained the conserved nanosequence-TAATATTAC and six open reading frames, including two in the virus sense and four in the complementary sense. On the basis of a 99% shared nucleotide sequence identity, they are considered isolates of the same species. BLASTn analysis and a comparison of the sequence with others available in the GenBank database ( http://www.ncbi.nlm.nih.gov ) indicated that the Taiwan virus shared its highest nt identity (more than 95%) with the Squash leaf curl Philippines virus (GenBank Accession No. AB085793). Virus-associated satellite DNA was not found in any of the samples. DNA-B was found in both samples, providing further evidence that the virus was the same as the bipartite Squash leaf curl Philippines virus. To our knowledge, this is the first report of Squash leaf curl Philippines virus in Taiwan.

References: (1) R. W. Briddon et al. Virology 312:106, 2003. (2) R. L. Gilbertson et al. J. Gen. Virol. 72:2843, 1991. (3) S. K. Green et al. Plant Dis. 85:1286, 2001. (4) M. R. Rojas et al. Plant Dis. 77:340, 1993.
First Report of the Root-Knot Nematode Meloidogyne minor on Turfgrass in Belgium
Authors: Viaene N. , Wiseborn D. B. , Karssen G.
Published: June 2007

The root-knot nematode, Meloidogyne minor, was described during 2004 after it was found on potato roots in a field in the Netherlands and in golf courses in England, Wales, and Ireland (2). Since it is associated with yellow patch disease in turf grass and causes deformation of potato tubers (2), it is important to know whether this organism is already widespread in these and neighboring countries. In addition, it has a relatively wide host range (2,4). A small survey conducted in Belgium was comprised of 10 golf courses geographically spread over the country. In each location, 3 to 9 samples were taken (one per green) consisting of 30 to 40 cores (1.5 × 20 cm deep). Nematodes were extracted from a 200-g subsample (containing roots) from each sample using zonal centrifugation (1). All Meloidogyne spp. were mounted on semipermanent slides and identified morphologically. M. minor was discovered in 3 of 6 samples taken in April 2006 from a golf course in Hasselt (northeastern Belgium). Between 41 and 50 M. minor per 100 g of soil were found together with M. naasi (7 to 20 individuals per 100 g of soil). Occurrence of M. minor together with other Meloidogyne species has been reported in natural and cultivated sites (2,4). Moreover, spores of Pasteuria spp. were clearly visible on 42% of the observed second-stage juveniles of M. minor, but not on those of M. naasi. The infected juveniles had between 2 and 15 spores attached to their cuticles. Additional juveniles were extracted from the soil samples and used for molecular identification by real-time PCR (2), which confirmed the presence of M. minor. There were no symptoms on the grass, consisting of a mixture of Agrostis stolonifera (10%), Festuca rubra (30%), and Poa annua (60%). Grass was sown in Rhine sand and heath land compost used for the construction of the greens in Hasselt. It could be that these soil amendments were infested with M. minor or that M. minor was introduced by other means, e.g., shoes, maintenance machinery, or golf equipment. On the other hand, the detection of M. minor in this small survey indicates that the species may be prevalent in golf courses in the region. The nematode has been found in several golf courses and sport fields in the United Kingdom and the Netherlands, including a golf course at Breda (close to the Belgian border) (3). The survey will be expanded to include grasslands and dune areas, the presumed natural habitat of M. minor.

References: (1) G. A. Hendrickx. Nematologica 41:308, 1995. (2) G. Karssen et al. Nematology 6:59, 2004. (3) W. Lammers et al. Meloidogyne minor. Pest Risk Assessment. Online publication, www.minlnv.nl/pd - Schadelijke organismen, 2006. (4) S. J. Turner and C. C. Fleming. Comm. Appl. Biol. Sci. Ghent University 70:885, 2005.
First Report of Haplotype I-b of Phytophthora infestans in Central Mexico
Authors: Garay-Serrano E. , Fernández-Pavía S. P. , Rodríguez-Alvarado G. , Flier W. G. , Lozoya-Saldaña H. , Rojas-Martínez R. I. , Goss E. M. , Grünwald N. J.
Published: June 2007

Central Mexico is considered a center of genetic diversity for Phytophthora infestans on the basis of a range of genotypic and phenotypic characteristics (3). Surprisingly, while mitochondrial DNA (mtDNA) haplotypes I-a, II-a, and II-b have been reported from central Mexico, haplotype I-b has not been found in central Mexico (1). Therefore, a more extensive search for haplotypes was conducted in areas where sexual reproduction occurs. During the summer of 2003, leaflets of cvs. Rosita and Tollocan with a single lesion of late blight were collected in the area of Villarreal, located in Terrenate County in Tlaxcala, Mexico (170 km northeast of Mexico City). Fourteen P. infestans isolates were characterized for mtDNA haplotype, isozyme genotype (glucose 6- phosphate isomerase [Gpi] and peptidase [Pep]), and mating type. Isolation, mating type, and isozyme genotype were characterized following reported protocols (1,4). MtDNA haplotype was determined by amplifying and digesting the P2 and P4 regions and comparing amplicons to those of reference strains of known haplotype (1,2). Twelve isolates were mtDNA haplotype I-a and two were I-b. While the mtDNA I-b has been associated with the US-1 lineage (mating type: A1, Gpi: 86/100, Pep: 92/100), the genotypes for the Mexican isolates were A2, 86/100 Gpi, 100/100 Pep from cv. Rosita and A2, 86/100 Gpi, 92/100 Pep from cv. Tollocan. To our knowledge, this is the first report of the I-b mtDNA haplotype of P. infestans from central Mexico and it is now clear that all four haplotypes exist in Mexico. This finding therefore, stresses the importance of including a representative regional sampling of Mexican and Andean isolates in studies inferring the origin of this species.

References: (1) W. G. Flier et al. Phytopathology 93:382, 2003. (2) G. W. Griffith and D. S. Shaw. Appl. Environ. Microbiol. 64:4007, 1998. (3) N. J. Grünwald and W. G. Flier. Ann. Rev. Phytopathol. 43:171, 2005. (4) N. J. Grünwald et al. Phytopathology 91:882, 2001.
Occurrence of Blight Caused by Sclerotium rolfsii on Lolium perenne in Argentina
Authors: Goldring L. , Lacasa M. , Wright E. R. , Pérez B. A. , Rivera M. C.
Published: June 2007

A perennial ryegrass (Lolium perenne L.) lawn located at Castelar (Buenos Aires Province) showed disease symptoms during the summer of 2003. Chlorotic patches as much as 15 cm in diameter appeared on the lawn. Later, dead plants with white mycelia developing on the crown and surrounding soil occurred at the periphery of the rings. Plants showed leaf chlorosis and crown and root rot. No sclerotia developed on plant organs. Diseased plants were collected, washed with running tap water for 4 h, and disinfested in 5% NaOCl for 2 min. Pieces, 3 to 5 mm long from symptomatic leaves, crowns, and roots, were incubated on 2% potato dextrose agar (PDA) at 22 to 25°C with a 12-h light/dark cycle. Mycelia growing on the soil surface was transferred to PDA and incubated under the same conditions. After 3 to 4 days, white, conspicuous mycelia that produced sclerotia grew from diseased tissue pieces and soil mycelial samples. Sclerotia were nearly spherical, 1 to 2 mm in diameter, white but turning brown with age, and produced in large numbers over the entire colony surface. Primary hyphae showed clamp connections at the septa. A pathogenicity test was performed with 20 1-month-old plants of L. perenne grown in a 1:1 (v/v) mixture of sand and soil contained in 24- × 17- × 4-cm plastic trays. Seven-day-old fungal cultures grown on PDA were cut into 1- cm2 pieces and placed among the plants on the substrate. Each tray was inoculated with seven inoculum pieces. Five trays of plants were inoculated with the fungus, and plants in five trays that served as controls had only sterile pieces of PDA placed on the substrate. All plants were maintained at 25°C and watered frequently. First symptoms, consisting of chlorosis, were observed 4 days after inoculation. Of the plants, 34, 59, 60, 65, and 70% developed symptoms 6, 9, 14, 17, and 21 days after inoculation, respectively. Control plants remained healthy. The fungus was reisolated from diseased plants and identified as Sclerotium rolfsii Sacc. (teleomorph Athelia rolfsii (Curzi) C.C. Tu & Kimbr.) on the basis of morphological and cultural characteristics (3,4). The disease has been observed causing stalk rot on perennial ryegrass in the United States (1) and Australia (2). To our knowledge, this is the first report of S. rolfsii causing disease on L. perenne in Argentina.

References: (1) D. F. Farr et al. Fungi on Plants and Plant Products in the United States. The American Phytopathological Society. St. Paul, MN. 1989. (2) D. F. Farr et al. Fungal Databases. Systematic Botany and Mycology Laboratory. Online publication. ARS, USDA, 2007. (3) J. E. M. Mordue. No. 410 in: Descriptions of Pathogenic Fungi and Bacteria. CMI, Kew, UK, 1974. (4) Z. K. Punja and A. Damiani. Mycologia 88:694, 1996.
First Report of Powdery Mildew on Tomato Caused by Oidium neolycopersici in Venezuela
Authors: Montilla J. O. , González M. S. , Renaud D.
Published: June 2007

During 2004 and 2005, a powdery mildew was observed in tomato (Lycopersicon esculentum Mill. cv. Rio Grande) fields in several states in Venezuela. Symptoms included development of patches of dense white mycelium, predominantly on the upper leaf surface. Leaves in the middle and lower canopies were the most affected. Similar symptoms sometimes were observed on stems. The foliage of infected plants turned yellow and showed necrosis followed by desiccation and rapid defoliation. Microscopic examination revealed the presence of typical structures of the Oidium genus. Hyphae were hyaline and septate. Conidiophores were unbranched, erect, measured 51 to 108 (80) μm, and consisted of 3 or 4 cells. Conidia were hyaline, ellipsoidal to ovoidal, and measured 16 to 43 (30) × 12 to 22 (16) μm. Conidia were produced singly, without fibrosin bodies. Conidial polar germination was common. Appressoria were lobed. The sexual stage was not found. The fungus was identified as Oidium neolycopersici, recently recognized as a distinct species (1,2). Conidia from infected tomato leaves were shaken onto leaves of 10 plants of L. esculentum and L. pimpinellifolium (Jusl.) Mill. and five plants of a weed (Physalis peruviana L.). Noninoculated plants served as a control. Symptoms that developed on all inoculated plants were similar to those of plants naturally infected. Within 7 to 8 days, symptoms in L. esculentum consisted of small colonies that quickly covered large portions of foliar tissue. L. pimpinellifolium showed small and localized symptoms after 10 days and P. peruviana showed symptoms after 15 days. To our knowledge, this is the first report of O. neolycopersici in Venezuela.

References: (1) H. Jones et al. Mol. Plant Pathol. 2:303, 2001. (2) L. Kiss et al. Mycol. Res. 105:684, 2001.
Two Amino Acid Substitutions in the Coat Protein of Pepper mild mottle virus Are Responsible for Overcoming the L4 Gene-Mediated Resistance in Capsicum spp.
Authors: Genda Yoshikatsu , Kanda Ayami , Hamada Hiroyuki , Sato Kyoko , Ohnishi Jun , Tsuda Shinya
Published: June 2007

The Capsicum spp. L genes (L1 to L4) confer resistance to tobamoviruses. Currently, the L4 gene from Capsicum chacoense is the most effective resistance gene and has been used widely in breeding programs in Japan which have developed new resistant cultivars against Pepper mild mottle virus (PMMoV). However, in 2004, mild mosaic symptoms began appearing on the leaves of commercial pepper plants in the field which possessed the L4 resistance gene. Serological and biological assays on Capsicum spp. identified the causal virus strain as a previously unreported pathotype, P1,2,3,4. PMMoV sequence analysis of the virus and site-directed mutagenesis using a PMMoV-J of the P1,2 pathotype revealed that two amino acid substitutions in the coat protein, Gln to Arg at position 46 and Gly to Lys at position 85, were responsible for overcoming the L4 resistance gene.
Systemic Acquired Resistance in Canola Is Linked with Pathogenesis-Related Gene Expression and Requires Salicylic Acid
Authors: Potlakayala Shobha D. , Reed Darwin W. , Covello Patrick S. , Fobert Pierre R.
Published: June 2007

Systemic acquired resistance (SAR) is an induced defense response that confers long-lasting protection against a broad range of microbial pathogens. Here we show that treatment of Brassica napus plants with the SAR-inducing chemical benzo-(1,2,3)-thiadiazole-7-carbothioic acid S-methyl ester (BTH) significantly enhanced resistance against virulent strains of the bacterial pathogen Pseudomonas syringae pv. maculicola and the fungal pathogen Leptosphaeria maculans. Localized preinoculation of plants with an avirulent strain of P. syringae pv. maculicola also enhanced resistance to these pathogens but was not as effective as BTH treatment. Single applications of either SAR-inducing pretreatment were effective against P. syringae pv. maculicola, even when given more than 3 weeks prior to the secondary challenge. The pretreatments also led to the accumulation of pathogenesis-related (PR) genes, including BnPR-1 and BnPR-2, with higher levels of transcripts observed in the BTH-treatment material. B. napus plants expressing a bacterial salicylate hydroxylase transgene (NahG) that metabolizes salicylic acid to catechol were substantially compromised in SAR and accumulated reduced levels of PR gene transcripts when compared with untransformed controls. Thus, SAR in B. napus displays many of the hallmarks of classical SAR including long lasting and broad host range resistance, association with PR gene activation, and a requirement for salicylic acid.
Genetic Diversity in Populations ofXanthomonas campestrispv.campestrisin Cruciferous Weeds in Central Coastal California
Authors: Ignatov A. , Sechler A. , Schuenzel E. L. , Agarkova I. , Oliver B. , Vidaver A. K. , Schaad N. W.
Published: June 2007

Xanthomonas campestris pv. campestris (X. campestris) infects a large number of cruciferous plants, including weeds. California has one of the largest and most diverse populations of wild cruciferous plants in the world. Although considerable information is available on the genetic diversity of X. campestris in commercial crop plants, nothing is known about the diversity in strains infecting weeds. To assess the genetic diversity among strains of X. campestris in weeds in noncultivated and cultivated areas, strains of the pathogen were isolated from populations of cruciferous weeds growing in coastal valley crop-production sites and from remote nonproduction sites along the California central coast. Results of fingerprinting over 68 strains using amplified fragment length polymorphism along with representative strains by sequence analysis showed the presence of seven genotypes. Genotypes A and B were limited to coastal sites; genotypes C, D, and E were from inland cultivated sites; and genotypes F and G were present in both coastal noncultivated and inland cultivated sites. Crop strains were grouped outside any weed strain group and were separated from the weed strains and other pathovars of X. campestris. These results revealed, for the first time, that strains of X. campestris present in noncultivated coastal weed populations generally were unique to a site and genetically distinct from strains present in populations of weeds in crop-production areas located nearby.
Effect of Microclimate on Leveillula taurica Powdery Mildew of Sweet Pepper
Authors: Elad Yigal , Messika Yoel , Brand Michal , David Dalia Rav , Sztejnberg Abraham
Published: June 2007

Sweet pepper-Leveillula taurica microclimate relations were studied under controlled conditions and in commercial greenhouses. Conidial germination occurred at 10 to 37°C and was optimal at 20°C. Conidial viability declined as temperatures increased to 40°C for 6 h. Leaf colonization was optimal at 15 to 25°C. Severe leaf infections occurred at 15 to 20°C and conidiation was suppressed at 20 to 25°C. Highest germination rates were observed at 75 to 85% relative humidity (RH). Severity of leaf coverage by symptoms was high for plants which were subjected to longer periods of temperatures between 10 to 15°C and daytime RH between 85 to 95%, and positively correlated with nighttime RH. Disease severity was negatively correlated with lengthy periods of temperatures >25°C, day and night average temperatures, and average daytime RH. Conversely, leaf shedding was relatively high under conditions characterized by long periods of temperatures >20°C and <13°C, and positively correlated with average daytime temperatures and periods of RH <75%. Increasing nighttime temperatures by heating and daytime temperatures by closing the greenhouse side walls reduced disease in two commercial greenhouse experiments. A midseason shift from a cooler greenhouse climate to warm daytime climate halted epidemic development. Flower number and yield were reduced in infected crops.
Characterization and Distribution of Mating Type Genes in the Dothistroma Needle Blight Pathogens
Authors: Groenewald Marizeth , Barnes Irene , Bradshaw Rosie E. , Brown Anna V. , Dale Angie , Groenewald Johannes Z. , Lewis Kathy J. , Wingfield Brenda D. , Wingfield Michael J. , Crous Pedro W.
Published: June 2007

Dothistroma septosporum and D. pini are the two causal agents of Dothistroma needle blight of Pinus spp. in natural forests and plantations. Degenerate primers amplified portions of mating type genes (MAT1-1-1 and MAT1-2) and chromosome walking was applied to obtain the full-length genes in both species. The mating-type-specific primers designed in this study could distinguish between the morphologically similar D. pini and D. septosporum and between the different mating types of these species. Screening of isolates from global collections of D. septosporum showed that only MAT2 isolates are present in Australian and New Zealand collections, where only the asexual form of the fungus has been found. In contrast, both mating types of D. septosporum were present in collections from Canada and Europe, where the sexual state is known. Intriguingly, collections from South Africa and the United Kingdom, where the sexual state of the fungus is unknown, included both mating types. In D. pini, for which no teleomorph is known, both mating types were present in collections from the United States. These results provided new insights into the biology and global distribution of two of the world's most important pine pathogens and should facilitate management of the diseases caused by these fungi.
Identification of Molecular Markers Linked to aPyrenophora teresAvirulence Gene
Authors: Beattie Aaron D. , Scoles Graham J. , Rossnagel Brian G.
Published: June 2007

Genetic control of avirulence in the net blotch pathogen, Pyrenophora teres, was investigated. To establish an appropriate study system, a collection of 10 net form (P. teres f. teres) and spot form (P. teres f. maculata) isolates were evaluated on a set of eight barley lines to identify two isolates with differential virulence on an individual host line. Two net form isolates, WRS 1906, exhibiting avirulence on the cv. Heartland, and WRS 1607, exhibiting high virulence, were mated and 67 progeny were isolated and phenotyped for reaction on Heartland. The population segregated in a 1:1 ratio, 34 avirulent to 33 virulent (χ2= 0.0, P = 1.0), indicating single gene control of WRS 1906 avirulence on Heartland. Bulked segregant analysis was used to identify six amplified fragment length polymorphism markers closely linked to the avirulence gene (AvrHeartland). This work provides evidence that the P. teres-barley pathosystem conforms to the gene-for-gene model and represents an initial step toward map-based cloning of this gene.
Selective pressures for and against genetic instability in cancer: a time-dependent problem
Authors: Komarova Natalia L , Sadovsky Alexander V , Wan Frederic Y.M
Published: June 2007

Genetic instability in cancer is a two-edge sword. It can both increase the rate of cancer progression (by increasing the probability of cancerous mutations) and decrease the rate of cancer growth (by imposing a large death toll on dividing cells). Two of the many selective pressures acting upon a tumour, the need for variability and the need to minimize deleterious mutations, affect the tumour's ‘choice’ of a stable or unstable ‘strategy’. As cancer progresses, the balance of the two pressures will change. In this paper, we examine how the optimal strategy of cancerous cells is shaped by the changing selective pressures. We consider the two most common patterns in multistage carcinogenesis: the activation of an oncogene (a one-step process) and an inactivation of a tumour-suppressor gene (a two-step process). For these, we formulate an optimal control problem for the mutation rate in cancer cells. We then develop a method to find optimal time-dependent strategies. It turns out that for a wide range of parameters, the most successful strategy is to start with a high rate of mutations and then switch to stability. This agrees with the growing biological evidence that genetic instability, prevalent in early cancers, turns into stability later on in the progression. We also identify parameter regimes where it is advantageous to keep stable (or unstable) constantly throughout the growth.
A model for glioma cell migration on collagen and astrocytes
Authors: Aubert M , Badoual M , Christov C , Grammaticos B
Published: June 2007

We present a model for the migration of glioma cells on substrates of collagen and astrocytes. The model is based on a cellular automaton where the various dynamical effects are introduced through adequate evolution rules. Using our model, we investigate the role of homotype and heterotype gap junction communication and show that it is possible to reproduce the corresponding experimental migration patterns. In particular, we confirm the experimental findings that inhibition of homotype gap junctions favours migration while heterotype inhibition hinders it. Moreover, the effect of heterotype gap junction inhibition dominates that of homotype inhibition.
Improved bounds for composites and rigidity of gradient fields
Authors: Albin Nathan , Conti Sergio , Nesi Vincenzo
Published: June 2007

We determine an improved lower bound for the conductivity of three-component composite materials. Our bound is strictly larger than the well-known Hashin–Shtrikman bound outside the regime where the latter is known to be optimal. The main ingredient of our result is a new quantitative rigidity estimate for gradient fields in two dimensions.
Probabilistic climate forecasts and inductive problems
Authors: Frame D.J , Faull N.E , Joshi M.M , Allen M.R
Published: June 2007

The development of ensemble-based ‘probabilistic’ climate forecasts is often seen as a promising avenue for climate scientists. Ensemble-based methods allow scientists to produce more informative, nuanced forecasts of climate variables by reflecting uncertainty from various sources, such as similarity to observation and model uncertainty. However, these developments present challenges as well as opportunities, particularly surrounding issues of experimental design and interpretation of forecast results. This paper discusses different approaches and attempts to set out what climateprediction.net and other large ensemble, complex model experiments might contribute to this research programme.
Confidence, uncertainty and decision-support relevance in climate predictions
Authors: Stainforth D.A , Allen M.R , Tredger E.R , Smith L.A
Published: June 2007

Over the last 20 years, climate models have been developed to an impressive level of complexity. They are core tools in the study of the interactions of many climatic processes and justifiably provide an additional strand in the argument that anthropogenic climate change is a critical global problem. Over a similar period, there has been growing interest in the interpretation and probabilistic analysis of the output of computer models; particularly, models of natural systems. The results of these areas of research are being sought and utilized in the development of policy, in other academic disciplines, and more generally in societal decision making. Here, our focus is solely on complex climate models as predictive tools on decadal and longer time scales. We argue for a reassessment of the role of such models when used for this purpose and a reconsideration of strategies for model development and experimental design. Building on more generic work, we categorize sources of uncertainty as they relate to this specific problem and discuss experimental strategies available for their quantification. Complex climate models, as predictive tools for many variables and scales, cannot be meaningfully calibrated because they are simulating a never before experienced state of the system; the problem is one of extrapolation. It is therefore inappropriate to apply any of the currently available generic techniques which utilize observations to calibrate or weight models to produce forecast probabilities for the real world. To do so is misleading to the users of climate science in wider society. In this context, we discuss where we derive confidence in climate forecasts and present some concepts to aid discussion and communicate the state-of-the-art. Effective communication of the underlying assumptions and sources of forecast uncertainty is critical in the interaction between climate science, the impacts communities and society in general.
Valvulogenesis: the moving target
Authors: Butcher Jonathan T , Markwald Roger R
Published: June 2007

Valvulogenesis is an extremely complex process by which a fragile gelatinous matrix is populated and remodelled during embryonic development into thin fibrous leaflets capable of maintaining unidirectional flow over a lifetime. This process occurs during exposure to constantly changing haemodynamic forces, with a success rate of approximately 99%. Defective valvulogenesis results in impaired cardiac function and lifelong complications. This review integrates what is known about the roles of genetics and mechanics in the development of valves and how changes in either result in impaired morphogenesis. It is hoped that appropriate developmental cues and phenotypic endpoints could help engineers and clinicians in their efforts to regenerate living valve alternatives.
Peptide nucleic acid fluorescence in situ hybridization for rapid detection of Klebsiella pneumoniae from positive blood cultures
Authors: Søgaard Mette , Hansen Dennis S. , Fiandaca Mark J. , Stender Henrik , Schønheyder Henrik C.
Published: June 2007

This study evaluated a novel peptide nucleic acid (PNA) probe targeting a region of the 23S rRNA gene of Klebsiella pneumoniae by fluorescence in situ hybridization (FISH). Analytical performance was determined using 39 reference strains and other well-characterized strains of Klebsiella spp. and Enterobacter aerogenes. The probe was found to be specific for the K. pneumoniae complex (K. pneumoniae including Klebsiella ozaenae and Klebsiella variicola). The diagnostic accuracy was evaluated with 264 blood cultures containing Gram-negative rods. Using conventional identification as the reference, performance specifications were as follows: sensitivity 98.8 %, specificity 99.5 %, positive predictive value 98.8 % and negative predictive value 99.5 %. Discrepancies were resolved by PNA FISH retest and phenotypic tests. In conclusion, the K. pneumoniae probe provided an accurate diagnosis within 3 h and may supplement other methods for direct identification of Gram-negative bacteria.
A specific real-time PCR assay for the detection of Bordetella pertussis
Authors: Vincart Benoit , De Mendonça Ricardo , Rottiers Sylvianne , Vermeulen Françoise , Struelens Marc J. , Denis Olivier
Published: June 2007

A novel real-time PCR (RT-PCR) assay was developed for detection ofBordetella pertussisin respiratory specimens by targeting the pertactin gene.In vitroevaluation with reference strains and quality control samples showed analytical sensitivity equivalent to and specificity superior to those of PCR assays which target the IS481element. The pertactin-based RT-PCR assay offers better discrimination betweenB. pertussisand otherBordetellaspecies than previously described assays.
Interpretive criteria to differentiate low- and high-level mupirocin resistance in Staphylococcus aureus
Authors: Moreira de Oliveira Naira Elane , Cardozo Ana Paula Couto Marques , Marques Elizabeth de Andrade , Netto dos Santos Kátia Regina , deMarval Marcia Giambiagi
Published: June 2007

Meticillin-resistant Staphylococcus aureus isolates were classified into three mupirocin susceptibility groups by the disc diffusion method using 5 and 200 μg mupirocin discs. The zone diameter observed for a 5 μg disc distinguished MupS from the resistant strains (either MupRL or MupRH). On the other hand, a 200 μg disc distinguished the high-resistance MupRH strains from the other two (MupS or MupRL). Thus, the concomitant use of 5 and 200 μg mupirocin discs allowed the clear distinction among the three mupirocin susceptibility groups, MupS, MupRL or MupRH.
Novel protein targets of the humoral immune response to Listeria monocytogenes infection in rabbits
Authors: Yu Wei Ling , Dan Hanhong , Lin Min
Published: June 2007

The role of the humoral immune response in protective immunity against listerial infection has been overlooked and is essentially unknown. This study aimed to discover the protein targets ofListeria monocytogenesthat elicit an antibody response following infection in a rabbit model. A genomic expression library forL. monocytogeneswas constructed and differentially screened to identify genes encoding proteins that reacted with antiserum from rabbits infected with liveL. monocytogenesserotype 4b (RαL), but not with that from animals immunized with heat-killed bacteria (RαK). Thirty-one clones expressing proteins that reacted exclusively with RαL were identified and sequenced. Sequence analysis, together with Western blot analysis of the proteins expressed from positive clones, led to the identification of eightL. monocytogenesproteins as targets of humoral immune responses during listerial infection: three internalin members (InlA, InlD and InlC2) and five novel proteins of unknown function (designated IspA, IspB, IspC, IspD and IspE, respectively). Exhibition of humoral immune responses to these proteins in actively infected rabbits but not in animals receiving heat-killedL. monocytogenessuggested that they were induced or significantly upregulatedin vivoduring infection and thus are important inListeriapathogenesis. With the exception of antibodies to InlA, this is the first demonstration of antibodies to the other seven proteins in infected hosts. These immunogenic proteins may be useful candidates for elucidation of the role of antibodies in protective immunity in the context of listerial infection, as well as potential targets for serodiagnostic reagents and vaccine and drug development.
Type-specific and cross-reactive antibodies induced by human papillomavirus 31 L1/L2 virus-like particles
Authors: Xu Yufei , Wang Qingyong , Han Yehua , Song Guoxing , Xu Xuemei
Published: June 2007

The aim of this study was to determine whether antibodies induced by human papillomavirus (HPV) type 31 L1/L2 virus-like particles (VLPs) could cross-react with VLPs of the closely related HPV-16 and distantly related HPV-11, and to investigate the potential role of the L2 protein in L1/L2 VLPs in inducing cross-neutralizing antibodies. Antisera were prepared from rabbits immunized with intact or denatured HPV-31 L1/L2 VLPs. Cross-reaction and cross-neutralization were analysed by Western blotting and ELISA, and by haemagglutination inhibition, respectively. Western blotting results showed that H31 L1/L2 (D) antiserum (antiserum from a rabbit immunized with denatured HPV-31 L1/L2 VLPs) could cross-react with the L1 protein of HPV-11 and -16. HPV-31 L1/L2 VLP antiserum showed strong cross-reaction with and cross-neutralization of HPV-16 VLPs, but this was significantly less with HPV-11 VLPs. In addition, the cross-neutralizing activity against HPV-16 L1/L2 VLPs was slightly higher than that against HPV-16 L1 VLPs, although the difference was not statistically significant. Epitope-blocking ELISA showed that mAb H16.V5 could partially inhibit the cross-reaction of HPV-31 L1/L2 VLP antiserum with HPV-16 L1/L2 VLPs. These results suggested that (i) H31 L1/L2 (D) antiserum could cross-react with L1 protein from both closely related and distantly related HPV types, but HPV-31 L1/L2 VLP antiserum could only cross-neutralize closely related HPV types, (ii) surface-exposed epitopes of the L2 protein in L1/L2 VLPs may induce only low titres of cross-neutralizing antibodies and (iii) certain epitopes that cross-reacted with HPV-31 L1/L2 VLP antiserum are located close to the epitopes recognized by mAb H16.V5. These findings may provide suggestions for the design of multivalent VLP vaccines.
The first UK isolate of ‘Bordetella ansorpii’ from an immunocompromised patient
Authors: Fry Norman K. , Duncan John , Malnick Henry , Cockcroft Paul M.
Published: June 2007

What is believed to be the first clinical isolate of ‘Bordetella ansorpii’ in the UK from an immunocompromised patient is described. The only previously documented isolation of ‘B. ansorpii’ was following the initial culture of a single strain from an epidermal cyst of a patient in Korea.