Correction: Widespread mortality of trembling aspen (Populus tremuloides) throughout interior Alaskan boreal forests resulting from a novel canker disease

[This corrects the article DOI: 10.1371/journal.pone.0250078.].

Recommendations of generic names in Diaporthales competing for protection or use

In advancing to one name for fungi, this paper treats generic names competing for use in the order Diaporthales (Ascomycota, Sordariomycetes) and makes a recommendation for the use or protection of one generic name among synonymous names that may be either sexually or asexually typified. A table is presented that summarizes these recommendations. Among the genera most commonly encountered in this order, Cytospora is recommended over Valsa and Diaporthe over Phomopsis. New combinations are introduced for the oldest epithet of important species in the recommended genus. These include Amphiporthe tiliae, Coryneum lanciforme, Cytospora brevispora, C. ceratosperma, C. cinereostroma, C. eugeniae, C. fallax, C. myrtagena, Diaporthe amaranthophila, D. annonacearum, D. bougainvilleicola, D. caricae-papayae, D. cocoina, D. cucurbitae, D. juniperivora, D. leptostromiformis, D. pterophila, D. theae, D. vitimegaspora, Mastigosporella georgiana, Pilidiella angustispora, P. calamicola, P. pseudogranati, P. stromatica, and P. terminaliae.

Strong genetic differentiation between North American and European populations of Phytophthora alni subsp. uniformis

Alder decline caused by Phytophthora alni has been one of the most important diseases of natural ecosystems in Europe during the last 20 years. The emergence of P. alni subsp. alni -the pathogen responsible for the epidemic-is linked to an interspecific hybridization event between two parental species: P. alni subsp. multiformis and P. alni subsp. uniformis. One of the parental species, P. alni subsp. uniformis, has been isolated in several European countries and, recently, in North America. The objective of this work was to assess the level of genetic diversity, the population genetic structure, and the putative reproduction mode and mating system of P. alni subsp. uniformis. Five new polymorphic microsatellite markers were used to contrast both geographical populations. The study comprised 71 isolates of P. alni subsp. uniformis collected from eight European countries and 10 locations in North America. Our results revealed strong differences between continental populations (Fst = 0.88; Rst = 0.74), with no evidence for gene flow. European isolates showed extremely low genetic diversity compared with the North American collection. Selfing appears to be the predominant mating system in both continental collections. The results suggest that the European P. alni subsp. uniformis population is most likely alien and derives from the introduction of a few individuals, whereas the North American population probably is an indigenous population.

Evaluation of resistance to Rhabdocline needlecast in Douglas fir variety Shuswap, with quantitative polymerase chain reaction

A quantitative polymerase chain reaction assay was developed that could detect DNA of Rhabdocline pseudotsugae and R. oblonga among DNA of Douglas fir needles to a limit as low as three copies of target DNA. Differential infection rates of two varieties (seed sources) of Douglas fir interplanted in a field were studied in relation to staggered bud breaks. Infection of Douglas fir var. San Isabel corresponded to ascospore release times for Rhabdocline spp., whereas infection of var. Shuswap Lake did not occur throughout the spore release period during 2 years of study, despite abundant inoculum and adequate moisture during bud break. Rhabdocline spp. DNA was never detected in Shuswap Lake and disease symptoms were not observed in any year. We provide evidence that Shuswap Lake is resistant and probably immune to Rhabdocline spp. infection and Rhabdocline needlecast under Michigan conditions.

Isotopologue fractionation during N(2)O production by fungal denitrification

Identifying the importance of fungi to nitrous oxide (N2O) production requires a non-intrusive method for differentiating between fungal and bacterial N2O production such as natural abundance stable isotopes. We compare the isotopologue composition of N2O produced during nitrite reduction by the fungal denitrifiers Fusarium oxysporum and Cylindrocarpon tonkinense with published data for N2O production during bacterial nitrification and denitrification. The fractionation factors for bulk nitrogen isotope values for fungal denitrification were in the range -74.7 to -6.6 per thousand. There was an inverse relationship between the absolute value of the fractionation factors and the reaction rate constant. We interpret this in terms of variation in the relative importance of the rate constants for diffusion and enzymatic reduction in controlling the net isotope effect for N2O production during fungal denitrification. Over the course of nitrite reduction, the delta(18)O values for N2O remained constant and did not exhibit a relationship with the concentration characteristic of an isotope effect. This probably reflects isotopic exchange with water. Similar to the delta(18)O data, the site preference (SP; the difference in delta(15)N between the central and outer N atoms in N2O) was unrelated to concentration during nitrite reduction and, therefore, has the potential to act as a conservative tracer of production from fungal denitrification. The SP values of N2O produced by F. oxysporum and C. tonkinense were 37.1 +/- 2.5 per thousand and 36.9 +/- 2.8 per thousand, respectively. These SP values are similar to those obtained in pure culture studies of bacterial nitrification but quite distinct from SP values for bacterial denitrification. The large magnitude of the bulk nitrogen isotope fractionation and the delta(18)O values associated with fungal denitrification are distinct from bacterial production pathways; thus multiple isotopologue data holds much promise for resolving bacterial and fungal production. Our work further provides insight into the role that fungal and bacterial nitric oxide reductases have in determining site preference during N2O production.

Phlyctema vagabunda Causes Coin Canker of Ash (Fraxinus spp.) in North America

During the spring of 2001, nursery-grown ash trees in Michigan and Ontario, Canada displayed coin cankers that were previously described (1). Cankered cultivars included Cimmaron®, ChampTree®, and Urbanite® (Fraxinus pennsylvanica), and Autumn Purple® (F. americana). Tissue from surface-sterilized cankers (0.06% sodium hypochlorite or 70% ethanol, 3 min) was placed onto one-half strength potato dextrose agar amended with 200 ppm of streptomycin sulfate (½ SPDA). Plates were incubated at 20 and 4°C in the dark. Phlyctema vagabunda (anamorph of Neofabraea alba (E.J. Guthrie) Verkley, (1999)) was isolated on the 4°C plates from most tissue pieces from all cultivars. P. vagabunda causes stem cankers of apple (Malus spp.) (1) but its pathogenicity to ash has never been demonstrated (2). Inoculations with P. vagabunda were made to green and white ash to fulfill Koch's postulates. Apple trees were also inoculated with the ash isolate. In Corvallis, OR, 2-year-old, bare-root ash trees and 15 1-year-old apple seedlings were inoculated in January, 2003. In Michigan, 10 trees each of cvs. Cimmaron® and Autumn Purple® were inoculated in December, 2002. The trees were inoculated with a wound-freezing method (3). Wounded sites received a 5-mm-diameter plug of ½ SPDA on which a 30-day-old culture derived from a single conidium of P. vagabunda AR3664 was actively growing, with sterile ½ SPDA used as a negative control. The plugs were held in place with Parafilm. Each ash in Oregon received three inoculations per stem. Six trees each of cvs. Autumn Purple®, ChampTree®, and Urbanite® and four trees of cv. Cimmeron® were inoculated with the fungus. Four additional trees of each cultivar were treated with sterile ½ SPDA (three sites per tree). Ten seedling apple trees were also inoculated with the fungus (three sites per tree) and five additional trees (five sites per tree) were inoculated with negative control plugs. In Michigan, each tree received two plugs of inoculum and two negative control plugs. All trees were evaluated 4 to 6 months after inoculation. Cankers similar to the originals formed on all ash cultivars in Oregon and Michigan; 97 of 106 inoculated wounds developed cankers on ash, and 29 of 30 inoculated wounds on Malus spp. developed cankers. P. vagabunda was recovered from cankers on each of the inoculated ash and apple trees. Five of 88 controls developed necrotic areas, but Phlyctema spp. were not recovered from any of these wounds. To our knowledge, this is the first report that P. vagabunda causes cankers on Fraxinus spp. and the first to show that Malus spp. can be infected with an ash isolate. References: (1) T. D. Gariépy et al. Mycol. Res. 107:528, 2003. (2) A. Y. Rossman et al. Plant Dis. 86:442, 2002. (3) R. Scorza and P. L. Pusey. Phytopathology 74:569, 1984.

The relationship between children's dental caries experience and the prescription of general anaesthetics. an evaluation of the effectiveness of a Personal Dental Service Pilot

OBJECTIVES

To determine if there was a high correlation between the prescription of a general anaesthetic for dental treatment in young children by a Personal Dental Services (PDS) general anaesthetic pilot and the dental health of children at a ward level.

BASIC RESEARCH DESIGN

Postcode data from an audit of the single dental general anaesthetic provider in an area was extracted and mapped to individual wards. A proxy for the oral health population was obtained by using the results of a large-scale dental prevalence study of five-year-olds. The wards were ranked into quintiles by dmft and a mean dmft calculated for each. There were 1,406 patients who had a general anaesthetic, 74% were aged 11 years or less.

SETTING

A personal dental service dental general anaesthetic pilot in the north of England providing services for a population of approximately 300,000 residents in a non-fluoridated area. RESULTS There was a positive correlation between increasing levels of dental decay in the population and increasing intervention ratios for dental treatment under general anaesthesia (r2 = 0.90).

CONCLUSIONS

The PDS pilot provided dental care under general anaesthesia for more patients from wards with poor dental health than from wards with better dental health.

Distribution of NHS resources for children's dental care in general dental practice in England

OBJECTIVE

To determine the relationship between the distribution of NHS resources in general dental practice and dental need and access to services for the population in England under the age of 18 in different socio-economic areas.

BASIC RESEARCH DESIGN

A proxy for the oral health of under 18 year olds was made from prevalence surveys undertaken on five year old children in each health authority area in 1999/2000. The level of spending per head of the population was ascertained from Dental Practice Board data. Health authorities were grouped according to the eleven United Kingdom Office of National Statistics socio-economic groups. Access was measured by using registration levels of children.

SETTING

General dental practices providing National Health Service treatment for children aged 0-18 in England.

RESULTS

There was no correlation (r = -0.03) between increasing need for dental care using mean dmft as a proxy and increasing spending per head of the population for each health authority. There was a correlation (r = 0.38) between increasing registration rates and increased spending per head. The populations under 18 had more spent on their oral health care living in areas classified as Mixed Economies, Services and Education and Most Prosperous. Those in Inner London, Manufacturing, Ports and Industry had proportionately the least. The difference between the highest and lowest group was 33%. The groups of Authorities were not homogenous in their level of resources with variations between Authorities in the same groups.

CONCLUSIONS

The distribution of NHS resources to general dental practice for people under 18 does not reflect population need. The higher the registration rate for children the greater the amount resources deployed in an area.

Taxonomy and toxicity of Conocybe lactea and related species

Conocybe lactea was examined as part of a larger study on the distribution of amatoxins and phallotoxins in fungi, and the taxonomic relationships between these fungi. As amatoxins are present in the congener C. filaris, the locally abundant C. lactea was examined using HPLC and mass spectroscopy. Amatoxins were not found in C. lactea, but the related phallotoxins were present in small quantities making it the first fungus outside of the genus Amanita in which phallotoxins have been detected. Despite the presence of a related toxin, C. lactea was found not to be taxonomically close to C. filaris. Phylogenetic analyses using nuclear ribosomal RNA genes indicated that North American specimens of C. lactea were conspecific with North American specimens of C. crispa in Conocybe sect. Candidae. European C. crispa was a distinct taxon. The implications of the use of the name C. albipes for these taxa are discussed. Nucleotide data confirmed placement of the sequestrate taxon Gastrocybe lateritia in sect. Candidae, but as a distinct taxon. It is hypothesized that the unique sequestrate morphology of G. lateritia may be caused by a bacterial infection.

Ribosomal DNA sequence divergence and group I introns within the Leucostoma species L. cinctum, L. persoonii, and L. parapersoonii sp. nov., ascomycetes that cause Cytospora canker of fruit trees

Leucostoma species that are the causal agents of Cytospora canker of stone and pome fruit trees were studied in detail. DNA sequence of the internal transcribed spacer regions and the 5.8S of the nuclear ribosomal DNA operon (ITS rDNA) supplied sufficient characters to assess the phylogenetic relationships among species of Leucostoma, Valsa, Valsella, and related anamorphs in Cytospora. Parsimony analysis of the aligned sequence divided Cytospora isolates from fruit trees into clades that generally agreed with the morphological species concepts, and with some of the phenetic groupings (PG 1-6) identified previously by isozyme analysis and cultural characteristics. Phylogenetic analysis inferred that isolates of L. persoonii formed two well-resolved clades distinct from isolates of L. cinctum. Phylogenetic analysis of the ITS rDNA, isozyme analysis, and cultural characteristics supported the inference that L. persoonii groups PG 2 and PG 3 were populations of a new species apparently more genetically different from L. persoonii PG 1 than from isolates representative of L. massariana, L. niveum, L. translucens, and Valsella melastoma. The new species, L. parapersoonii, was described. A diverse collection of isolates of L. cinctum, L. persoonii, and L. parapersoonii were examined for genetic variation using restriction fragment length polymorphism (RFLP) analysis of the ITS rDNA and the five prime end of the large subunit of the rDNA (LSU rDNA). HinfI and HpaII endonucleases were each useful in dividing the Leucostoma isolates into RFLP profiles corresponding to the isozyme phenetic groups, PG 1-6. RFLP analysis was more effective than isozyme analysis in uncovering variation among isolates of L. persoonii PG 1, but less effective within L. cinctum populations. Isolates representative of seven of the L. persoonii formae speciales proposed by G. Défago in 1935 were found to be genetically diverse isolates of PG 1. Two large insertions, 415 and 309 nucleotides long, in the small subunit (SSU) of the nuclear rDNA of L. cinctum were identified as Group 1 introns; intron 1 at position 943 and intron 2 at position 1199. The two introns were found to be consistently present in isolates of L. cinctum PG 4 and PG 5 and absent from L. cinctum PG 6 isolates, despite the similarity of the ITS sequence and teleomorph morphology. Intron 1 was of subgroup 1C1 whereas intron 2 was of an unknown subgroup. RFLP patterns and presence/absence of introns were useful characters for expediting the identification of cultures of Leucostoma isolated from stone and pome fruit cankers. RFLP patterns from 13 endonucleases provided an effective method for selecting an array of diverse PG 1 isolates useful in screening plant germplasm for disease-resistance.

Shoot dieback during prolonged drought in Ceanothus (Rhamnaceae) chaparral of California: a possible case of hydraulic failure

Progressive diebacks of outer canopy branchlets of Ceanothus crassifolius were repeatedly observed after rainless periods up to 9 mo in duration in the Santa Monica Mountains of southern California. Mean xylem pressures of branchlets near the end of drought were as low as -11.2 MPa (N = 22) with a mean of about 60 dead branchlets per shrub. Inoculation (N = 15) with three species of fungi previously isolated from the same population of C. crassifolius did not promote dieback, suggesting that the observed decline was not fungal induced, as had been proposed. Further, at least 50% of healthy-appearing twigs, without symptoms of dieback, contained isolatible endophytic fungi. We used a centrifugal force method to determine the range of xylem pressure causing cavitation (vulnerability curves) for branchlets (N = 12) and roots (N = 16). We combined vulnerability curves with soil texture data (N = 6) into a water transport model that estimated the critical values (P(Lcrit)) of leaf xylem pressure associated with the loss of water from soil to foliage. Maximum P(Lcrit) was between -10 and -11 MPa and within the range of minimum measured xylem pressures of branchlets during drought and dieback. Branchlet dieback correlated with seasonal declines in xylem pressure in concert with declining safety margins from hydraulic failure. Symptoms of dieback were duplicated in the field by partially severing stem xylem that normally supplied branchlets with water. Taken together, these results indicate that loss of hydraulic conductance to foliage was the probable cause of the observed dieback in C. crassifolius. Partial dieback of peripheral branchlets, and its attendant reduction in evaporative surface area, may be a last-resort mechanism for whole-plant water conservation and drought survival in this species.

Phlyctema vagabunda Isolated from Coin Canker of Ash Trees in Michigan

The coelomycetous fungus Phlyctema vagabunda Desm. (teleomorph Neofabraea alba (E.J. Guthrie) Verkley, synonym Pezicula alba E.J. Guthrie) is associated with a serious canker disease of cultivated ash trees in Michigan. Four- to five-year-old trees of Fraxinus americana cv. Autumn Purple and F. pennsylvanica cvs. Champ Tree, Cimmaron, and Urbanite had cankers that were smooth, round, brownish yellow, approximately 2 to 4 cm in diameter with distinct reddish, cracked margins. Immersed, eventually erumpent, unilocular acervuli developed in the central portions of these cankers. The same fungus was isolated both from the conidia as well as from the margin of the canker. The internal transcribed spacer (ITS) (AY064704) and beta-tubulin (AY064702) sequences were identical to sequences identified in GenBank as Pezicula alba from apple (1), and the morphology was consistent with Phlyctema vagabunda as well (2). P. vagabunda has been studied primarily as the cause of Bull's eye canker of apple (1). P. vagabunda under its numerous synonyms has been reported on various hardwood and herbaceous hosts from temperate regions around the world, including the United States. However, it has not been reported previously on species of Fraxinus. A specimen and culture from the ash cankers in Michigan have been deposited (BPI 841384 and CBS 109875). References: (1) S. N. De Jong et al. Mycol. Res. 105:658, 2001. (2) B. C. Sutton. The Coelomycetes. CMI, Kew, Surrey, UK, 1980.

The fertility of HD-affected individuals in Tasmania

A study was conducted of the fertility (number of live births) of Huntington's disease (HD)-affected individuals compared to that of the general population using data from the 1986 Census of Population and Housing. HD-affected individuals were found to be at least as fertile as members of the general population. This finding supports earlier studies.

Reproduction and age of onset of Huntington's disease in Tasmania

This study demonstrates that in Tasmania, individuals born before 1930, with an onset of Huntington's disease (HD) after the mean age of onset, were significantly more fertile than their unaffected siblings and the general population. This applied to both sexes. The mean parental age of men with late-onset disease was significantly greater than that of their unaffected male siblings. The clinical implication is that those individuals at 50% risk of late-onset HD who have achieved their desired family size should be offered sterilisation.