bluuebunny/crossref_metadata_2025 huggingface dataset:
Discovery of an alternate metabolic pathway for urea synthesis in adult
Aedes aegypti
mosquitoes
Authors: Scaraffia Patricia Y. , Tan Guanhong , Isoe Jun , Wysocki Vicki H. , Wells Michael A. , Miesfeld Roger L.
Published: January 2008

We demonstrate the presence of an alternate metabolic pathway for urea synthesis in
Aedes aegypti
mosquitoes that converts uric acid to urea via an amphibian-like uricolytic pathway. For these studies, female mosquitoes were fed a sucrose solution containing
15
NH
4
Cl, [5-
15
N]-glutamine, [
15
N]-proline, allantoin, or allantoic acid. At 24 h after feeding, the feces were collected and analyzed in a mass spectrometer. Specific enzyme inhibitors confirmed that mosquitoes incorporate
15
N from
15
NH
4
Cl into [5-
15
N]-glutamine and use the
15
N of the amide group of glutamine to produce labeled uric acid. More importantly, we found that [
15
N
2
]-uric acid can be metabolized to [
15
N]-urea and be excreted as nitrogenous waste through an uricolytic pathway.
Ae. aegypti
express all three genes in this pathway, namely, urate oxidase, allantoinase, and allantoicase. The functional relevance of these genes in mosquitoes was shown by feeding allantoin or allantoic acid, which significantly increased unlabeled urea levels in the feces. Moreover, knockdown of urate oxidase expression by RNA interference demonstrated that this pathway is active in females fed blood or
15
NH
4
Cl based on a significant increase in uric acid levels in whole-body extracts and a reduction in [
15
N]-urea excretion, respectively. These unexpected findings could lead to the development of metabolism-based strategies for mosquito control.
Biosynthesis of the enediyne antitumor antibiotic C-1027 involves a new branching point in chorismate metabolism
Authors: Van Lanen Steven G. , Lin Shuangjun , Shen Ben
Published: January 2008

C-1027 is an enediyne antitumor antibiotic composed of four distinct moieties: an enediyne core, a deoxy aminosugar, a β-amino acid, and a benzoxazolinate moiety. We now show that the benzoxazolinate moiety is derived from chorismate by the sequential action of two enzymes—SgcD, a 2-amino-2-deoxyisochorismate (ADIC) synthase and SgcG, an iron–sulfur, FMN-dependent ADIC dehydrogenase—to generate 3-enolpyruvoylanthranilate (OPA), a new intermediate in chorismate metabolism. The functional elucidation and catalytic properties of each enzyme are described, including spectroscopic characterization of the products and the development of a fluorescence-based assay for kinetic analysis. SgcD joins isochorismate (IC) synthase and 4-amino-4-deoxychorismate (ADC) synthase as anthranilate synthase component I (ASI) homologues that are devoid of pyruvate lyase activity inherent in ASI; yet, in contrast to IC and ADC synthase, SgcD has retained the ability to aminate chorismate identically to that observed for ASI. The net conversion of chorismate to OPA by the tandem action of SgcD and SgcG unambiguously establishes a new branching point in chorismate metabolism.
Binaural jitter improves interaural time-difference sensitivity of cochlear implantees at high pulse rates
Authors: Laback Bernhard , Majdak Piotr
Published: January 2008

Interaural time difference (ITD) arises whenever a sound outside of the median plane arrives at the two ears. There is evidence that ITD in the rapidly varying fine structure of a sound is most important for sound localization and for understanding speech in noise. Cochlear implants (CIs), neural prosthetic devices that restore hearing in the profoundly deaf, are increasingly implanted to both ears to provide implantees with the advantages of binaural hearing. CI listeners have been shown to be sensitive to fine structure ITD at low pulse rates, but their sensitivity declines at higher pulse rates that are required for speech coding. We hypothesize that this limitation in electric stimulation is at least partially due to binaural adaptation associated with periodic stimulation. Here, we show that introducing binaurally synchronized jitter in the stimulation timing causes large improvements in ITD sensitivity at higher pulse rates. Our experimental results demonstrate that a purely temporal trigger can cause recovery from binaural adaptation. Thus, binaurally jittered stimulation may improve several aspects of binaural hearing in bilateral recipients of neural auditory prostheses.
Hypothesis-based RNAi screening identifies neuroprotective genes in a Parkinson's disease model
Authors: Hamamichi Shusei , Rivas Renee N. , Knight Adam L. , Cao Songsong , Caldwell Kim A. , Caldwell Guy A.
Published: January 2008

Genomic multiplication of the locus-encoding human α-synuclein (α-syn), a polypeptide with a propensity toward intracellular misfolding, results in Parkinson's disease (PD). Here we report the results from systematic screening of nearly 900 candidate genetic targets, prioritized by bioinformatic associations to existing PD genes and pathways, via RNAi knockdown. Depletion of 20 gene products reproducibly enhanced misfolding of α-syn over the course of aging in the nematode
Caenorhabditis elegans
. Subsequent functional analysis of seven positive targets revealed five previously unreported gene products that significantly protect against age- and dose-dependent α-syn-induced degeneration in the dopamine neurons of transgenic worms. These include two trafficking proteins, a conserved cellular scaffold-type protein that modulates G protein signaling, a protein of unknown function, and one gene reported to cause neurodegeneration in knockout mice. These data represent putative genetic susceptibility loci and potential therapeutic targets for PD, a movement disorder affecting ≈2% of the population over 65 years of age.
The Expression of a Bean PGIP in Transgenic Wheat Confers Increased Resistance to the Fungal Pathogen Bipolaris sorokiniana
Authors: Janni Michela , Sella Luca , Favaron Francesco , Blechl Ann E. , De Lorenzo Giulia , D'Ovidio Renato
Published: January 2008

A possible strategy to control plant pathogens is the improvement of natural plant defense mechanisms against the tools that pathogens commonly use to penetrate and colonize the host tissue. One of these mechanisms is represented by the host plant's ability to inhibit the pathogen's capacity to degrade plant cell wall polysaccharides. Polygalacturonase-inhibiting proteins (PGIP) are plant defense cell wall glycoproteins that inhibit the activity of fungal endopolygalacturonases (endo-PGs). To assess the effectiveness of these proteins in protecting wheat from fungal pathogens, we produced a number of transgenic wheat lines expressing a bean PGIP (PvPGIP2) having a wide spectrum of specificities against fungal PGs. Three independent transgenic lines were characterized in detail, including determination of the levels of PvPGIP2 accumulation and its subcellular localization and inhibitory activity. Results show that the transgene-encoded protein is correctly secreted into the apoplast, maintains its characteristic recognition specificities, and endows the transgenic wheat with new PG recognition capabilities. As a consequence, transgenic wheat tissue showed increased resistance to digestion by the PG of Fusarium moniliforme. These new properties also were confirmed at the plant level during interactions with the fungal pathogen Bipolaris sorokiniana. All three lines showed significant reductions in symptom progression (46 to 50%) through the leaves following infection with this pathogen. Our results illustrate the feasibility of improving wheat's defenses against pathogens by expression of proteins with new capabilities to counteract those produced by the pathogens.
Phenotypes and Functional Effects Caused by Various Viral RNA Silencing Suppressors in Transgenic Nicotiana benthamiana and N. tabacum
Authors: Siddiqui Shahid Aslam , Sarmiento Cecilia , Truve Erkki , Lehto Harry , Lehto Kirsi
Published: January 2008

RNA silencing suppressor genes derived from six virus genera were transformed into Nicotiana benthamiana and N. tabacum plants. These suppressors were P1 of Rice yellow mottle virus (RYMV), P1 of Cocksfoot mottle virus, P19 of Tomato bushy stunt virus, P25 of Potato virus X, HcPro of Potato virus Y (strain N), 2b of Cucumber mosaic virus (strain Kin), and AC2 of African cassava mosaic virus (ACMV). HcPro caused the most severe phenotypes in both Nicotiana spp. AC2 also produced severe effects in N. tabacum but a much milder phenotype in N. benthamiana, although both HcPro and AC2 affected the leaf tissues of the two Nicotiana spp. in similar ways, causing hyperplasia and hypoplasia, respectively. P1-RYMV caused high lethality in the N. benthamiana plants but only mild effects in the N. tabacum plants. Phenotypic alterations produced by the other transgenes were minor in both species. Interestingly, the suppressors had very different effects on crucifer-infecting Tobamovirus (crTMV) infections. AC2 enhanced both spread and brightness of the crTMV-green fluorescent protein (GFP) lesions, whereas 2b and both P1 suppressors enhanced spread but not brightness of these lesions. P19 promoted spread of the infection into new foci within the infiltrated leaf, whereas HcPro and P25 suppressed the spread of crTMV-GFP lesions.
Patterns of Expression of a Lolitrem Biosynthetic Gene in the Epichloë festucae–Perennial Ryegrass Symbiosis
Authors: May Kimberley J. , Bryant Michelle K. , Zhang Xiuwen , Ambrose Barbara , Scott Barry
Published: January 2008

Lolitrem B is synthesized by Epichloë festucae in associations with Pooid grasses. A complex cluster of at least 10 genes (ltm genes) is required for its synthesis. An early step in this pathway is catalyzed by ltmM, a symbiosis-expressed gene. PltmM-gusA reporter gene analysis was used to monitor ltmM gene expression patterns in planta. The minimum promoter length required for high-level gusA expression in infected seedlings is in the range of 480 to 782 bp. gusA was expressed by the endophyte in all infected vegetative plant tissues and in epiphyllous hyphae. Spikelets from reproductive tillers were analyzed at different developmental stages. During pre-anthesis, gusA expression was observed in all infected floral organs except the immature gynoecium. In post-anthesis florets, gene expression occurred almost exclusively in the gynoecium. Expression of gusA by the endophyte was observed in germinating seeds 24 h postimbibition and seedlings older than 6 days postimbibition in hyphae from the mesocotyl to the tip of the emerging first leaf. This work provides a detailed analysis of the spatial and temporal expression patterns of a symbiosis-expressed gene in planta.
Identification of Quantitative Trait Loci Controlling Symptom Development During Viral Infection inArabidopsis thaliana
Authors: Sicard Ophélie , Loudet Olivier , Keurentjes Joost J. B. , Candresse Thierry , Le Gall Olivier , Revers Frédéric , Decroocq Véronique
Published: January 2008

In compatible interactions between plants and viruses that result in systemic infection, symptom development is a major phenotypic trait. However, host determinants governing this trait are mostly unknown, and the mechanisms underlying it are still poorly understood. In a previous study on the Arabidopsis thaliana–Plum pox virus (PPV) pathosystem, we showed a large degree of variation in symptom development among susceptible accessions. In particular, Cvi-1 (Cape Verde islands) accumulates viral particules but remains symptomless, Col-0 (Columbia) sometimes shows weak symptoms compared with Ler (Landsberg erecta), which always shows severe symptoms. Genetic analyses of Col × Ler and Cvi × Ler F2 and recombinant inbred line (RIL) populations suggested that symptom development as well as viral accumulation traits are polygenic and quantitative. Three of the symptom quantitative trait loci (QTL) identified could be confirmed in near-isogenic lines, including PSI1 (PPV symptom induction 1), which was identified on the distal part of chromosome 1 in both RIL populations. With respect to viral accumulation, several factors have been detected and, interestingly, in the Col × Ler population, two out of three viral accumulation QTL colocalized with loci controlling symptom development, although correlation analysis showed weak linearity between symptom severity and virus accumulation. In addition, in the Cvi × Ler RIL population, a digenic recessive determinant controlling PPV infection was identified.
Endophytic Actinobacteria Induce Defense Pathways in Arabidopsis thaliana
Authors: Conn V. M. , Walker A. R. , Franco C. M. M.
Published: January 2008

Endophytic actinobacteria, isolated from healthy wheat tissue, which are capable of suppressing a number wheat fungal pathogens both in vitro and in planta, were investigated for the ability to activate key genes in the systemic acquired resistance (SAR) or the jasmonate/ethylene (JA/ET) pathways in Arabidopsis thaliana. Inoculation of A. thaliana (Col-0) with selected endophytic strains induced a low level of SAR and JA/ET gene expression, measured using quantitative polymerase chain reaction. Upon pathogen challenge, endophyte-treated plants demonstrated a higher abundance of defense gene expression compared with the non-endophyte-treated controls. Resistance to the bacterial pathogen Erwinia carotovora subsp. carotovora required the JA/ET pathway. On the other hand, resistance to the fungal pathogen Fusarium oxysporum involved primarily the SAR pathway. The endophytic actinobacteria appear to be able to “prime” both the SAR and JA/ET pathways, upregulating genes in either pathway depending on the infecting pathogen. Culture filtrates of the endophytic actinobacteria were investigated for the ability to also activate defense pathways. The culture filtrate of Micromonospora sp. strain EN43 grown in a minimal medium resulted in the induction of the SAR pathway; however, when grown in a complex medium, the JA/ET pathway was activated. Further analysis using Streptomyces sp. strain EN27 and defense-compromised mutants of A. thaliana indicated that resistance to E. carotovora subsp. carotovora occurred via an NPR1-independent pathway and required salicylic acid whereas the JA/ET signaling molecules were not essential. In contrast, resistance to F. oxysporum mediated by Streptomyces sp. strain EN27 occurred via an NPR1-dependent pathway but also required salicylic acid and was JA/ET independent.
A β-1,3 Glucan Sulfate Induces Resistance in Grapevine against Plasmopara viticola Through Priming of Defense Responses, Including HR-like Cell Death
Authors: Trouvelot S. , Varnier A.-L. , Allègre M. , Mercier L. , Baillieul F. , Arnould C. , Gianinazzi-Pearson V. , Klarzynski O. , Joubert J.-M. , Pugin A. , Daire X.
Published: January 2008

Sulfated laminarin (PS3) has been shown previously to be an elicitor of plant defense reactions in tobacco and Arabidopsis and to induce protection against tobacco mosaic virus. Here, we have demonstrated the efficiency of PS3 in protecting a susceptible grapevine cultivar (Vitis vinifera cv. Marselan) against downy mildew (Plasmopara viticola) under glasshouse conditions. This induced resistance was associated with potentiated H2O2 production at the infection sites, upregulation of defense-related genes, callose and phenol depositions, and hypersensitive response-like cell death. Interestingly, similar responses were observed following P. viticola inoculation in a tolerant grapevine hybrid cultivar (Solaris). A pharmacological approach led us to conclude that both callose synthesis and jasmonic acid pathway contribute to PS3-induced resistance.
Veinal Necrosis Induced by Turnip mosaic virus Infection in Arabidopsis Is a Form of Defense Response Accompanying HR-Like Cell Death
Authors: Kim Bomin , Masuta Chikara , Matsuura Hideyuki , Takahashi Hideki , Inukai Tsuyoshi
Published: January 2008

In the pathosystems of Turnip mosaic virus (TuMV) with Brassicaceae crops, various symptoms, including mosaic and necrosis, are observed. We previously reported a necrosis-inducing factor TuNI in Arabidopsis thaliana, a model species. In this study, we show that the necrotic symptom induced by TuNI, observed along the veins, was actually a form of defense response accompanying a hypersensitive reaction (HR)-like cell death in the veinal area. The virus is often localized in the necrotic region. The necrotic response is associated with the production of H2O2, accumulation of salicylic acid (SA), emission of ethylene, and subsequent expression of defense-related genes. Additionally, this HR-like cell death is eased or erased by a shading treatment. These features are similar to the HR-associated resistance reaction to pathogens. However, unlike HR, two phytohormones—SA and ethylene—are involved in the necrosis induction, and both SA- and ethylene-dependent pathogenesis-related genes are activated. We concluded that the veinal necrosis induced by TuMV is regulated by a complex and unique network of at least two signaling pathways, which differs from the signal transduction for the known HR-associated resistance.
Pseudomonas syringae pv. tomato DC3000 Uses Constitutive and Apoplast-Induced Nutrient Assimilation Pathways to Catabolize Nutrients That Are Abundant in the Tomato Apoplast
Authors: Rico Arantza , Preston Gail M.
Published: January 2008

The plant apoplast is the intercellular space that surrounds plant cells, in which metabolic and physiological processes relating to cell wall biosynthesis, nutrient transport, and stress responses occur. The apoplast is also the primary site of infection for hemibiotrophic pathogens such as P. syringae, which obtain nutrients directly from apoplastic fluid. We have used apoplastic fluid extracted from healthy tomato leaves as a growth medium for Pseudomonas spp. in order to investigate the role of apoplastic nutrients in plant colonization by Pseudomonas syringae. We have confirmed that apoplast extracts mimic some of the environmental and nutritional conditions that bacteria encounter during apoplast colonization by demonstrating that expression of the plant-induced type III protein secretion pathway is upregulated during bacterial growth in apoplast extracts. We used a modified phenoarray technique to show that apoplast-adapted P. syringae pv. tomato DC3000 expresses nutrient utilization pathways that allow it to use sugars, organic acids, and amino acids that are highly abundant in the tomato apoplast. Comparative analyses of the nutrient utilization profiles of the genome-sequenced strains P. syringae pv. tomato DC3000, P. syringae pv. syringae B728a, P. syringae pv. phaseolicola 1448A, and the unsequenced strain P. syringae pv. tabaci 11528 with nine other genome-sequenced strains of Pseudomonas provide further evidence that P. syringae strains are adapted to use nutrients that are abundant in the leaf apoplast. Interestingly, P. syringae pv. phaseolicola 1448A lacks many of the nutrient utilization abilities that are present in three other P. syringae strains tested, which can be directly linked to differences in the P. syringae pv. phaseolicola 1448A genome.
Susceptibility in Viburnum to Phytophthora ramorum
Authors: Grünwald Niklaus J. , Kitner Megan , McDonald Virginia , Goss Erica M.
Published: January 2008

Phytophthora ramorum, the causal agent of sudden oak death on oak and tanoak and Ramorum blight or Ramorum shoot dieback on ornamentals, is a recently emerged pathogen. Viburnum is a genus of commonly grown ornamental shrubs known to be susceptible to P. ramorum. The entire genus has been placed on the P. ramorum host list. The range of susceptibility of genotypes in the genus is currently not understood. We evaluated whether or not cultivars in the genus Viburnum differ in susceptibility to P. ramorum in controlled, detached leaf inoculations using two isolates belonging to the two clonal lineages found in Oregon. The genus Viburnum shows remarkable differences in susceptibility to infection by P. ramorum. Viburnum genotypes differed significantly in susceptibility to P. ramorum in detached leaf inoculations. V. × burkwoodii was consistently the most susceptible host genotype, followed by V. plicatum ‘Mariesii’ and V. lentago. Most cultivars evaluated for resistance to P. ramorum were not susceptible or developed only small lesions as determined with a detached leaf assay. Our work only provides information on leaf based resistance, and inferences on epidemic development in whole canopies and under field conditions cannot currently be made.
A Fungal Symbiont of the Redbay Ambrosia Beetle Causes a Lethal Wilt in Redbay and Other Lauraceae in the Southeastern United States
Authors: Fraedrich S. W. , Harrington T. C. , Rabaglia R. J. , Ulyshen M. D. , Mayfield A. E. , Hanula J. L. , Eickwort J. M. , Miller D. R.
Published: January 2008

Extensive mortality of redbay has been observed in the coastal plain counties of Georgia and southeastern South Carolina since 2003 and northeastern Florida since 2005. We show that the redbay mortality is due to a vascular wilt disease caused by an undescribed Raffaelea sp. that is a fungal symbiont of Xyleborus glabratus, an exotic ambrosia beetle. Trees affected by the disease exhibit wilt symptoms that include a black discoloration of the sapwood. Redbay trees and containerized seedlings died within 5 to 12 weeks after inoculation with the Raffaelea sp. When redbay seedlings were challenged with X. glabratus, the beetles tunneled into 96% of the plants, 70% died, and the Raffaelea sp. was recovered from 91%. X. glabratus and the Raffaelea sp. have also been associated with mortality of sassafras, and the Raffaelea sp. has been isolated from wilted pondberry and pondspice. Additional inoculation studies have shown that the Raffaelea sp. is pathogenic to sassafras, spicebush, and avocado, but not to red maple. Female adults of X. glabratus have paired mycangia near the mandibles, and the Raffaelea sp. is routinely isolated from the heads of beetles. The fungus is apparently introduced into healthy redbay during beetle attacks on stems and branches. The wilt currently affecting redbay and sassafras represents a major threat to other members of the Lauraceae indigenous to the Americas, including avocado in commercial production.
Occurrence of Two Little Cherry Viruses in Sweet Cherry in Washington State
Authors: Bajet N. B. , Unruh T. R. , Druffel K. L. , Eastwell K. C.
Published: January 2008

Little cherry disease, one of the major viral diseases of sweet cherry (Prunus avium) worldwide, is associated with either of two closteroviruses, Little cherry virus 1 (LChV-1) and Little cherry virus 2 (LChV-2). Two sets of primers corresponding to a portion of the replicase gene of LChV-1 and LChV-2 were used in one-tube reverse-transcription polymerase chain reactions to detect these viruses in total RNA extracts of field-collected sweet cherry tissues. LChV-1 and LChV-2 were detected both alone and in combination in five sweet cherry orchards in Washington State. Sequence analysis of a 240-nucleotide (nt) fragment of the replicase open reading frame (ORF)1b and a 232-nt fragment from a portion of ORF8 and the 3′ untranslated region (UTR) of LChV-1 indicated that North American (NA) isolates shared 90 to 99% nucleotide identity in both genome segments analyzed. In contrast, comparisons of NA isolates to two Eurasian isolates of LChV-1 indicated shared nucleotide identities of 79 to 82% in the replicase fragment and 89 to 90% in the ORF8/3′UTR fragment. Sequence variation in the replicase region did not affect detection of LChV-1 in 12 isolates using the replicase-specific primers reported here. This article represents the first report of LChV-1 and LChV-2 in sweet cherry in Washington.
Population Variation of Apple Scab (Venturia inaequalis) Isolates from Asia and Europe
Authors: Xu Xiangming , Yang Jiarong , Thakur Vijay , Roberts Anthony , Barbara Dez J.
Published: January 2008

Apple scab, caused by Venturia inaequalis, is one of the most of damaging diseases worldwide on apple and currently is managed mainly by scheduled applications of fungicides. Understanding pathogen population structure is important for breeding and deployment of resistant cultivars. Isolates of V. inaequalis were sampled from a number of cultivars in China, India, and the United Kingdom to estimate differences in pathogen populations. Amplified fragment length polymorphism (AFLP) markers were used to genotype isolates, mostly from China and the United Kingdom. The AFLP data indicated that, overall, there were significant differences in V. inaequalis populations from China and the United Kingdom. Within China, there was no significant differentiation associated with their geographical or cultivar origins. In contrast, populations from four cultivars in two U.K. orchards (monoculture of Gala and a mixture orchard of Bramley, Cox, and Worcester) differed significantly. Furthermore, populations from Gala and Worcester were more homogenous than expected but those from Cox were more diverse than expected. In total, 80 isolates were selected randomly from three countries for virulence testing: 20 from the United Kingdom (10 from Gala and 10 from Cox), 30 from China (10 from Gala, 10 from Fuji, and 10 from Qingquan), and 30 from India (10 from Gala, 10 from Golden Delicious, and 10 from Black Ben Davis); of these 80 isolates, 41, 47, and 59 were inoculated against each of these cultivars in the United Kingdom, India, and China, respectively. The two local cultivars from India (Black Ben Davis) and the United Kingdom (Cox) were more resistant against non-indigenous isolates, particularly those from China, than they were against indigenous isolates; the Chinese local cultivar (Qingguan) showed a higher general level of resistance against isolates regardless of their origin.
Optimizing Efficacy of New Postharvest Fungicides and Evaluation of Sanitizing Agents for Managing Citrus Green Mold
Authors: Kanetis Loukas , Förster Helga , Adaskaveg James E.
Published: January 2008

Three new fungicides, azoxystrobin, fludioxonil, and pyrimethanil, that belong to different chemical classes are highly effective in managing citrus green mold and are being registered for postharvest use in the United States. Recirculating in-line drenches provided a significantly improved efficacy compared with standard low-volume spray applications. To prevent pathogen contamination of drench solutions, two oxidizing disinfectants, sodium hypochlorite and hydrogen peroxide/peroxyacetic acid (HPPA) solutions, were evaluated. Inhibition of conidial germination of Penicillium digitatum was dependent on the pH of the solution and the exposure time for each sanitizing agent. Chlorine (50 mg/liter) and HPPA (2,700 mg/liter) effectively inhibited germination in 40- and 240-s exposures, respectively, at pH 7. All fungicides tested were compatible and effective with HPPA, whereas fludioxonil, azoxystrobin, and thiabendazole, but not imazalil and pyrimethanil, were compatible with chlorine. In laboratory studies, sodium bicarbonate (SBC, 3%) significantly increased the efficacy of the three fungicides (250 mg/liter) and had no adverse effect on their stability in aqueous solutions. Fludioxonil (300 mg/liter)-SBC mixtures were still highly effective when applied 24 h after fruit inoculation. In experimental packingline studies, SBC or SBC-chlorine improved the efficacy of fludioxonil, whereas azoxystrobin was effective with and without these additives. Heating of drench solutions of fludioxonil (300 mg/liter) to 50°C did not improve decay control. In conclusion, in-line recirculating drench applications and fungicide-sanitizer-SBC mixtures significantly increased fungicide efficacy and provide an integrated approach for optimizing fungicide efficacy. These strategies also should minimize the selection for resistant isolates of the pathogen.
Three Colopterus Beetle Species Carry the Oak Wilt Fungus to Fresh Wounds on Red Oak in Missouri
Authors: Hayslett Maya , Juzwik Jennifer , Moltzan Bruce
Published: January 2008

Beetles in the family Nitidulidae can transmit the oak wilt fungus, Ceratocystis fagacearum, to fresh wounds on healthy oak trees, leading to infection and disease development. Historically, nitidulid beetles have not been considered important vectors of the pathogen in Missouri. Studies were conducted in the spring of 2005 and 2006 to determine frequencies of nitidulid beetle species contaminated with C. fagacearum visiting fresh wounds on red oak trees in central Missouri. Colopterus truncatus, C. niger, and C. semitectus were the most abundant species collected from fresh wounds and the only species found to be contaminated with Ceratocystis fagacearum. Of 230 beetles assayed for C. fagacearum, 23 yielded the fungus. Contamination frequencies were higher for beetles collected in April than May; no beetles collected in June were contaminated. We hypothesize that Colopterus truncatus, C. niger, and C. semitectus are principal nitidulid beetle vector species in Missouri during spring. The risk for pathogen transmission by these beetles appears to be greatest in April and least in June.
Scanning Electron Microscopy Reveals Different Response Pattern of FourVitisGenotypes toXylella fastidiosaInfection
Authors: Fritschi Felix B. , Lin Hong , Walker M. Andrew
Published: January 2008

The xylem-limited bacterium Xylella fastidiosa causes Pierce's disease (PD), whose disease symptoms are primarily the result of xylem vessel blockage in susceptible grapevines. Stem internode and petiole tissues from infected and uninfected control plants of four grape genotypes (Vitis vinifera, V. rufotomentosa, V. smalliana, and V. arizonica/candicans) differing in PD susceptibility were examined using scanning electron microscopy (SEM). Tyloses, fibrillar networks, and gum plugs were observed in lumens of tracheary elements in petioles and internodes of both water-inoculated control plants and X. fastidiosa–inoculated plants of all genotypes. Bacteria were not observed in control plants. In both petiole and internode tissues, the greatest number of occluded xylem vessels were observed in V. vinifera and the smallest number in V. arizonica/candicans. The number of xylem vessels infested with X. fastidiosa was greatest in V. vinifera and did not differ among the other three genotypes. Systemic infection was found in all genotypes. The frequency with which X. fastidiosa infested vessels were observed using SEM corresponded well with bacterial levels estimated by enzyme-linked immunosorbent assay. Among infected plants, tylose formation in internodes was lowest in V. arizonica/candicans and did not differ among the other three genotypes. Infection with X. fastidiosa strongly induced tylose formation in V. vinifera and V. smalliana but not in V. arizonica/candicans. Analysis across tissues and genotypes indicated an induction of fibrillar networks and gum occlusions in response to X. fastidiosa infection, whereas treatment comparisons within genotypes were not significant except for V. vinifera petioles. Limiting the spread of X. fastidiosa infection by xylem conduit occlusions does not appear to be the mechanism conferring PD resistance or tolerance to V. arizonica/candicans, V. smalliana, or V. rufotomentosa. In contrast, the strong induction of tyloses may be detrimental rather than beneficial for V. vinifera survival after X. fastidiosa infection.
Baseline Sensitivity of Ascochyta rabiei to Azoxystrobin, Pyraclostrobin, and Boscalid
Authors: Wise K. A. , Bradley C. A. , Pasche J. S. , Gudmestad N. C. , Dugan F. M. , Chen W.
Published: January 2008

Ascochyta rabiei, causal agent of Ascochyta blight on chickpea (Cicer arietinum), can cause severe yield loss in the United States. Growers rely on applications of fungicides with site-specific modes of action such as the quinone outside inhibiting (QoI) fungicides azoxystrobin and pyraclostrobin, and the carboximide fungicide boscalid, to manage disease. In all, 51 isolates collected prior to QoI fungicide registration and 71 isolates collected prior to boscalid registration in the United States were tested in an in vitro assay to determine the effective fungicide concentration at which 50% of conidial germination was inhibited (EC50) for each isolate–fungicide combination. The effect of salicylhydroxamic acid (SHAM) on conidia of A. rabiei in the presence and absence of azoxystrobin also was assessed to determine whether the fungus is capable of using alternative respiration. Five of nine A. rabiei isolates tested had significantly higher (P ≤ 0.05) EC50 values when SHAM was not included in media amended with azoxystrobin, indicating that A. rabiei has the potential to use alternative respiration to overcome fungicide toxicity in vitro. EC50 values of azoxystrobin and pyraclostrobin ranged from 0.0182 to 0.0338 μg/ml and from 0.0012 to 0.0033 μg/ml, with mean values of 0.0272 and 0.0023 μg/ml, respectively. EC50 values of boscalid ranged from 0.0177 to 0.4960 μg/ml, with a mean of 0.1903 μg/ml. Establishment of these baselines is the first step in developing a monitoring program to determine whether shifts in sensitivity to these fungicides are occurring in the A. rabiei pathogen population.
First Report of Diplodia seriata, the Anamorph of “Botryosphaeria” obtusa, Causing Fruit Rot of Olive in Spain
Authors: Moral J. , Luque F. , Trapero A.
Published: January 2008

In October, 2006, 1,000 olive fruits (Olea europaea) were collected to study latent infections of Colletotrichum spp., causal agent of anthracnose, in an olive orchard in Córdoba Province (southern Spain). The fruits were incubated at 22 to 24°C and 100% relative humidity. Thirteen percent of the fruits showed a black rot that covered part or all of the fruit and pycnidia formed on the fruit surface. The fungus most consistently isolated from affected fruits was identified as Diplodia seriata, the anamorph of “Botryosphaeria” obtusa, by morphological criteria (1). Pathogenicity tests were performed on 50 immature and 50 mature fruits of olive cv. Hojiblanca. The fruits were washed in sterilized water with Tween 20 at 20 μl/liter and surface sterilized in 20% sodium hypochlorite for 2 min. Twenty-five of the immature and 25 mature fruits were wounded with a sterile 0.5-mm-diameter needle, inoculated by immersion in aqueous conidial suspensions (2.2 × 105 conidia ml–1) for 30 min. The same number of immature and mature fruits, wounded and unwounded, were treated only with sterilized Tween 20 water and served as the control. All fruit were incubated at 22 to 24°C and 100% relative humidity. The experiment was repeated twice. Eight days after inoculation, 75% of the mature inoculated fruits showed a general rot with pycnidia developing on the surface of the fruit. After 20 days, the first symptoms of disease were observed on immature olive fruits (2%) and all mature fruits. After 50 days, only 14% of immature inoculated fruits exhibited symptoms of the disease. The fungus caused mummification of mature fruits. D. seriata was reisolated from lesions on all infected fruits. There were no differences in the amount and severity of disease between wounded and unwounded fruits. Control fruits did not display disease symptoms after 50 days. Incidence of olive fruits affected by D. seriata in olive orchards in southern Spain is unknown, although it may be low since it was detected only in 1 of 12 olive orchards sampled for Colletotrichum spp. in 2006. Incidence of fruit rot associated with D. seriata in this orchard was 1.2% of fruits, which also were affected by Colletotrichum. D. seriata has a worldwide distribution and infects numerous fruit trees. In our research, D. seriata is pathogenic on olive fruits but weakly virulent. To our knowledge, this is the first report worldwide of the anamorph of “B.” obtusa causing fruit rot on olives.

Reference: (1) A. J. L. Phillips et al. Fungal Divers. 25:141, 2007.
First Report of Potato virus Y in Nicotiana mutabilis in France
Authors: Cardin L. , Moury B.
Published: January 2008

Nicotiana mutabilis Stehmann & Semir is a recently described perennial plant species from southern Brazil that produces long floral stems with white to deep pink flowers and is used for its ornamental quality. In 2003, leaf mosaic symptoms were observed in all 30 N. mutabilis plants in a nursery in the south of France. Observation of crude sap preparations with the electron microscope revealed numerous flexuous particles, 700 to 730 nm long and approximately 11 nm wide, associated with “pinwheel”-like cytoplasmic inclusions, typical of the family Potyviridae. A range of plant species inoculated with extracts from five of the symptomatic plants showed reactions typical of Potato virus Y (PVY) (2), and the presence of the virus was confirmed by positive reactions in double-antibody sandwich (DAS)-ELISA with polyclonal antibodies raised against PVY. To test if PVY was responsible for the symptoms observed in N. mutabilis, an isolate was multiplied in N. tabacum cv. Xanthi plants after isolation from local lesions on Chenopodium amaranticolor and was then mechanically inoculated to 12 seedlings of N. mutabilis cv. Marshmallow. After 3 weeks, the 12 inoculated plants showed systemic vein clearing symptoms and PVY was detected by DAS-ELISA. Reverse transcription (RT)-PCR tests using PVY-polyvalent primers (5′-GATGGTTGCCTTGGATGATG and 5′-TAAAAGTAGTACAGGAAAAGCCA) covering the coat protein (CP) coding region amplified a single DNA fragment of the expected 900 bp from total RNA extracts from Xanthi plants inoculated with the five isolates. One of these DNA products was directly sequenced (GenBank Accession No. EU252529) and several accepted methods of phylogenetic analysis compared this sequence to 80 available PVY CP coding sequences and showed that the N. mutabilis PVY belonged to the C1 group (1). Similar to the other PVY strains in the C group, the N. mutabilis isolate was able to induce hypersensitive local lesions in leaves of potato genotypes carrying the Nc gene. However, contrary to the other characterized C1 isolates (1), it was unable to infect systemically cv. Yolo Wonder pepper plants. That peculiar behavior makes the N. mutabilis isolate a tool to identify the viral determinants controlling the host range of PVY.

References: (1) B. Blanco-Urgoiti et al. J. Gen. Virol. 79:2037, 1998. (2) C. Kerlan. No. 414 in: Descriptions of Plant Viruses. CMI/AAB, Kew, Surrey, UK, 2006.
First Report of Rhizome Blight of Ginger Caused by Binucleate Rhizoctonia AG-R in China
Authors: Yang G. H. , Conner R. L. , Cai H. , Li F. , Chen Y. Y.
Published: January 2008

In 2004, rhizome blight of ginger (Zingiber officinale (Willd.) Roscoe) (cv. Yunnanxiaojiang) occurred in the Kunming District of China. The surface of ginger rhizome after harvest was crimpled and covered with white hyphae. Initial symptoms on ginger were wilting on the stem and the color of the rhizome turned from white to light brown with no lesion formation. After 2 weeks, the surface of ginger rhizome was covered with white hyphae and a dry rot set in under humid conditions. The yield loss in ginger almost reached 50% because of the disease. An AG-R tester isolate paired with the unknown 37 isolates of Rhizoctonia spp. from the diseased ginger rhizomes caused a C2 reaction that confirmed their identity. Isolates of AG-R (GenBank Accession Nos. DQ885780 and DQ885781) had 100% sequence similarity with 5.8S rDNA-ITS with the AG-R tester isolate (GenBank Accession No. AF354082). To produce infected soil inoculum, 10 isolates were cultured on potato dextrose agar in a 9-cm petri dish for 3 to 4 days and then covered with approximately 20 g of autoclaved soil and kept at 25°C for 3 to 4 days. Seedlings of ginger (cv, Yunanxiaojiang) were planted in natural potting soil at a density of one plant per vinyl pot (8 cm in diameter, 9 cm high) and grown in the greenhouse for 7 days. Each seedling was inoculated with 7 g of infested soil by placing it around the rhizome. Control plants were inoculated with autoclaved soil. The experiments were carried out three times, each time with three replicates in a growth chamber kept at 25 and 16°C with a 16-h light and 8-h dark photoperiod. After 14 days, the disease severity was recorded based on a scale in which – = no symptoms; + = small lesions on seedlings, no blight; ++ = seedling blight; and +++ = plant dead. All of the 10 tested AG-R isolates caused ginger seedling blight. Rhizoctonia spp. was reisolated from these plants, confirming its pathogenicity. To our knowledge, this is the first report of rhizome blight of ginger caused by Rhizoctonia spp. and binucleate Rhizoctonia AG-R in China.

References: (1) B. Sneh et al. Page 135 in: Identification of Rhizoctonia Species. The American Phytopathological Society, St. Paul, MN, 1998.
First Report of Pythium splendens Associated with Severe Wilt of Muskmelon (Cucumis melo) in Oman
Authors: Al-Sa'di A. M. , Deadman M. L. , Al-Said F. A. , Khan I. , Al-Azri M. , Drenth A. , Aitken E. A. B.
Published: January 2008

Muskmelon (Cucumis melo L.) is one of the most important vegetable crops in Oman. In the fall of 2004, sudden wilt was observed in muskmelon grown in a field at Sultan Qaboos University, Muscat. The disease was characterized by rapid collapse of vines and muskmelon plants at the fruit production to maturation stage, associated with brown-to-dark brown rotted primary and secondary roots. The disease resulted in death of more than 85% of muskmelon plants in that field. On potato dextrose agar (PDA), with published methods (1), Pythium spp. were consistently isolated from crowns and roots of plants showing wilt symptoms. Further identification of five isolates of Pythium with sequences of the internal transcribed spacer (ITS) of the ribosomal DNA (1) using ITS1 and ITS4 primers produced a nucleotide sequence 806 bp long, which was identical among all isolates. Comparison with sequences deposited at the National Center for Biotechnology Information revealed 100% nucleotide similarity to a previously published sequence (Accession No. DQ381808) of isolate P091 of P. splendens from cucumber from Oman, for which identification has also been confirmed by morphological characteristics. The sequence of one isolate of P. splendens (P222) was assigned GenBank Accession No. EF546436 and deposited at CBS under Accession No. CBS121855. In pathogenicity tests conducted in a greenhouse, P. splendens induced damping-off symptoms on 7-day-old muskmelon seedlings and also reproduced the same wilt symptoms observed in the field when 2-month-old muskmelon plants were inoculated with 3-day-old P. splendens grown in PDA. To our knowledge, this is the first report of association of P. splendens with wilt of muskmelon in Oman.

Reference: (1) A. M. Al-Sa'di et al. Plant Pathol. 56:140, 2007.
First Report of Pink Seed of Pea Caused by Erwinia rhapontici in North Dakota
Authors: Wise K. A. , Zhao Y. F. , Bradley C. A.
Published: January 2008

In 2006, a seed lot of dry pea cv. DS Admiral obtained from Bowman County, North Dakota contained seed with bright-to-pale pink discoloration on the seed coat. Five discolored seeds and five seeds with normal appearance were surface disinfected in a 0.5% NaOCl solution for 1 min and rinsed with sterilized distilled water for 1 min. Seeds were placed onto potato dextrose agar (PDA) and incubated at 22°C. Three days later, the discolored seeds produced pink bacterial colonies and a pink pigment that diffused throughout the PDA. The pink bacterial colonies were tentatively identified as Erwinia rhapontici on the basis of colony and pigment color (2,3). No fungi or bacteria grew from the seed with normal appearance. A pink bacterial colony growing from one of the discolored seeds was streaked onto PDA and a single colony was obtained. A streaked plate incubated at 37°C showed no growth, which distinguishes E. rhapontici from Brenneria rubrifaciens (formerly E. rubrifaciens) (1–3). To confirm the identity, the isolate was sent to the Bacterial Identification and Fatty Acid Analysis Laboratory at the University of Florida, Gainesville. Fatty acid analysis indicated a similarity index of 0.515 for E. rhapontici. For an additional confirmation of identity, the 16S ribosomal DNA (rDNA) gene was amplified from the E. rhapontici isolate with universal primers fD1 and rP1 (4). The PCR product was cloned into pGEM-T easy vector (Promega, Madison, WI) and sequenced with primers SP6 and T7 at the Keck Biotechnology Center at the University of Illinois, Urbana. The resulting nucleotide sequence was compared with 16S rDNA sequences deposited in the ribosomal database ( http://rdp.cme.msu.edu/seqmatch/seqmatch_intro.jsp ) and showed highest identity to sequences of E. rhapontici or E. persicinus strains. To confirm pathogenicity, the basal ends of five pods on each of six pea plants (cv. Carneval) were syringe injected with 0.1 ml of suspension containing the obtained E. rhapontici isolate in the greenhouse by the methods as previously described (2). As a control, five pods on each of two plants were injected with 0.1 ml of sterile distilled water. Twenty-eight of the 51 seeds obtained from the bacteria-inoculated pods had pink seed symptoms, while seeds from the control pods appeared normal. Isolations from symptomatic and asymptomatic seed were performed as described above, and E. rhapontici was obtained from symptomatic seed. To our knowledge, this is the first report of pink seed of pea caused by E. rhapontici in North Dakota. The first report of this disease on pea in the United States was from Montana (3).

References: (1) L. Hauben et al. Syst. Appl. Microbiol. 21:384, 1998. (2) H. C. Huang et al. Can. J. Plant Pathol. 12:445, 1990. (3) B. K. Schroeder et al. Plant Dis. 86:188, 2002. (4) W. G. Weisburg et al. J. Bacteriol. 173:697, 1991.