Exploring the utility of Brachypodium distachyon as a model pathosystem for the wheat pathogen Zymoseptoria tritici

peer-reviewedBackground Zymoseptoria tritici, the causative organism of Septoria tritici blotch disease is a prevalent biotic stressor of wheat production, exerting substantial economic constraints on farmers, requiring intensive chemical control to protect yields. A hemibiotrophic pathogen with a long asymptomless phase of up to 11 days post inoculation (dpi) before a rapid switch to necrotrophy; a deficit exists in our understanding of the events occurring within the host during the two phases of infection. Brachypodium distachyon has demonstrated its potential as a model species for the investigation of fungal disease resistance in cereal and grass species. The aim of this study was to assess the physical interaction between Z. tritici (strain IPO323) and B. distachyon and examine its potential as a model pathosystem for Z. tritici. Results Septoria tritici blotch symptoms developed on the wheat cultivar Riband from 12 dpi with pycnidial formation abundant by 20 dpi. Symptoms on B. distachyon ecotype Bd21-1 were visible from 1 dpi: characteristic pale, water soaked lesions which developed into blotch-like lesions by 4 dpi. These lesions then became necrotic with chlorotic regions expanding up to 7 dpi. Sporulation on B. distachyon tissues was not observed and no evidence of fungal penetration could be obtained, indicating that Z. tritici was unable to complete its life cycle within B. distachyon ecotypes. However, observation of host responses to the Z. tritici strain IPO323 in five B. distachyon ecotypes revealed a variation in resistance responses, ranging from immunity to a chlorotic/necrotic phenotype. Conclusions The observed interactions suggest that B. distachyon is an incompatible host for Z. tritici infection, with STB symptom development on B. distachyon comparable to that observed during the early infection stages on the natural host, wheat. However first visible symptoms occurred more rapidly on B. distachyon; from 1 dpi in comparison to 12 dpi in wheat. Consequently, we propose that the interaction between B. distachyon and Z. tritici as observed in this study could serve as a suitable model pathosystem with which to investigate mechanisms underpinning an incompatible host response to Z. tritici.Teagasc Walsh Fellowship Programm

Generating Phenotypic Diversity in a Fungal Biocatalyst to Investigate Alcohol Stress Tolerance Encountered during Microbial Cellulosic Biofuel Production

peer-reviewedConsolidated bioprocessing (CBP) of lignocellulosic biomass offers an alternative route to renewable energy. The crop pathogen Fusarium oxysporum is a promising fungal biocatalyst because of its broad host range and innate ability to co-saccharify and ferment lignocellulose to bioethanol. A major challenge for cellulolytic CBP-enabling microbes is alcohol inhibition. This research tested the hypothesis that Agrobacterium tumefaciens - mediated transformation (ATMT) could be exploited as a tool to generate phenotypic diversity in F. oxysporum to investigate alcohol stress tolerance encountered during CBP. A random mutagenesis library of gene disruption transformants (n=1,563) was constructed and screened for alcohol tolerance in order to isolate alcohol sensitive or tolerant phenotypes. Following three rounds of screening, exposure of select transformants to 6% ethanol and 0.75% n-butanol resulted respectively in increased (≥11.74%) and decreased (≤43.01%) growth compared to the wild –type (WT). Principal component analysis (PCA) quantified the level of phenotypic diversity across the population of genetically transformed individuals and isolated candidate strains for analysis. Characterisation of one strain, Tr. 259, ascertained a reduced growth phenotype under alcohol stress relative to WT and indicated the disruption of a coding region homologous to a putative sugar transporter (FOXG_09625). Quantitative PCR (RT-PCR) showed FOXG_09625 was differentially expressed in Tr. 259 compared to WT during alcohol-induced stress (P<0.05). Phylogenetic analysis of putative sugar transporters suggests diverse functional roles in F. oxysporum and other filamentous fungi compared to yeast for which sugar transporters form part of a relatively conserved family. This study has confirmed the potential of ATMT coupled with a phenotypic screening program to select for genetic variation induced in response to alcohol stress. This research represents a first step in the investigation of alcohol tolerance in F. oxysporum and has resulted in the identification of several novel strains, which will be of benefit to future biofuel research.Funding provided through the Irish Department of Agriculture and Food's Research Stimulus Fund (Project Code RSF 07 513

Learning or leaving? An international qualitative study of factors affecting the resilience of female family doctors

Background: Many countries have insufficient numbers of family doctors, and more females than males leave the workforce at a younger age or have difficulty sustaining careers. Understanding the differing attitudes, pressures, and perceptions between genders toward their medical occupation is important to minimise workforce attrition. Aim: To explore factors influencing the resilience of female family doctors during lifecycle transitions. Design & setting: International qualitative study with female family doctors from all world regions. Method: Twenty semi-structured online Skype interviews, followed by three focus groups to develop recommendations. Data were transcribed and analysed using applied framework analysis. Results: Interview participants described a complex interface between competing demands, expectations of their gender, and internalised expectations of themselves. Systemic barriers, such as lack of flexible working, excessive workload, and the cumulative impacts of unrealistic expectations impaired the ability to fully contribute in the workplace. At the individual level, resilience related to: the ability to make choices; previous experiences that had encouraged self-confidence; effective engagement to obtain support; and the ability to handle negative experiences. External support, such as strong personal networks, and an adaptive work setting and organisation or system maximised interviewees’ professional contributions. Conclusion: On an international scale, female family doctors experience similar pressures from competing demands during lifecycle transitions; some of which relate to expectations of the female's ’role’ in society, particularly around the additional personal pressures of caring commitments. Such situations could be predicted, planned for, and mitigated with explicit support mechanisms and availability of workplace choices. Healthcare organisations and systems around the world should recognise this need and implement recommendations to help reduce workforce losses. These findings are likely to be of interest to all health professional staff of any gender

A one dimensional hydrodynamic simulation of colliding quasi neutral plasma systems

Studies of colliding laser-produced plasmas are of interest in several fields of research, including fusion energy generation, pulsed-laser deposition and potentially as intense short wavelength (X-ray and EUV) light sources. Computer simulations of such systems are a valuable tool in reconciling experimental results with theory and designing new experiments while also providing a platform to explore scenarios which are not easy to realise experimentally. A one-dimensional (1D) hydrodynamic simulation of quasineutrality- compliant colliding plasma systems has been developed and is described. The model is based on a multi-fluid theory due to P W Rambo and J Denavit [J. Comput. Phys. 98 (1992) 317] and uses a flux-corrected transport algorithm with an Eulerian grid in order to solve the three Euler equations for hydrodynamic flow. It includes source terms appropriate for high-density, high-temperature plasmas, such as those produced on dense targets at the focus of intense laser beams. Stagnation and interpenetration effects are simulated by means of collisional momentum coupling between species. Results are compared with the case of colliding plasmas in the absence of collisional coupling

Molecular techniques for studying <i>Fusarium</i> ear blight of wheat

This work has compared polymerase chain reaction (PCR) assays and traditional visual disease assessment to evaluate the severity of Fusarium ear blight (FEB) ofwheat under field and glasshouse conditions. In a field trial, PCR analysis highlighted the problem of diagnosis of FEB of wheat based on visual disease assessment where natural inoculum was present. PCR-based analysis detected F. poae predominantly in the glumes and Microdochium nivale sub-species were predominantly found in the rachis component of ears. M. nivale var. majus was more frequently observed than var. nivale (64 and 36 %, respectively). Quantitative PCR analysis and conventional visual disease assessment were used to evaluate fungicide efficacy against FEB of wheat caused by F. culmorum and F. poae in three glasshouse trials (1994/5-1996/7). Prochloraz and tebuconazole significantly decreased both visual symptoms of FEB and fungal DNA content of F. culmorum and F. poae ear blight of wheat. Overall, both fungicides appeared equally effective, although the efficacy ofthese fungicides was consistently greater as measured by PCR analysis rather than by visual disease assessment. Inoculation with F. culmorum significantly reduced yield (1000 grain weight) whereas inoculation with F. poae had no significant effect on yield. Fusarium culmorum was successfully transformed with the GUS reporter gene. GUS activity levels of transformants varied, but transformation did not affect pathogenicity on wheat seedlings. A GUS transformant was used to study the effectiveness of two fungicides against F. culmorum foot rot of wheat. Primers to the Tri5 gene were used to develop a PCR-based assay for the specific detection of potential trichothecene-producing Fusarium species. These primers were also used to develop an RT-PCR-based assay for the detection and semiquantification of F. culmorum Tri5 gene expression 'relative to p-tubulin gene expression' in RNA extracts from F. culmorum. This assay was used to show that time and fungicides can affect Tri5 gene expression in liquid culture

Weed survey of spring cereals in New Brunswick

En 1986 et 1987, un inventaire des mauvaises herbes a été effectué dans 187 champs de céréales de printemps au Nouveau-Brunswick. Au total, 76 espèces ont été identifiées, 40 d'entre elles étant considérées comme importantes sur le plan agronomique. Environ 50% des espèces étaient vivaces. L'ortie royale (Galeopsis tetrahit), le chiendent (Agropyron repens), la petite oseille (Rumex acetosella), la marguerite blanche (Chrysanthemum leucanthemum), la spargoute des champs (Spergula arvensis) et la stellaire moyenne (Stellaria média) avaient les plus hautes valeurs d'abondance relative. Le chiendent et l'ortie royale avaient les plus fortes densités à 8,0 et 7,1 plantes m-2, respectivement. La densité de mauvaises herbes la plus élevée (103 plantes m-2) a été observée chez l'avoine (Avena sativa) cultivée à la suite de plantes fourragères. La plus faible densité a été détectée chez le blé (Triticum aestivum) suite à une culture de pomme de terre (Solanum tuberosum). La plupart des espèces abondantes étaient tolérantes au MCPA, l'herbicide le plus fréquemment utilisé. Les agriculteurs pourraient lutter plus efficacement contre les mauvaises herbes dans les céréales en choisissant un herbitolérantes au MCPA ou au 2,4-D, et a en pré-plantation ou en post-récolte ses herbes vivaces.During 1986 and 1987, a weed survey of 187 New Brunswick cereal fields was conducted. A total of 76 species were identified of which 40 were considered agronomically important. About 50% of the species were perennial. Hemp-nettle (Galeopsis tetrahit), quack grass (Agropyron repens), sheep sorrel (Rumex acetosella), ox-eye daisy (Chrysanthemum leucanthemum), corn spurry (Spergula arvensis), and chickweed (Stellaria média) had the highest relative abundance values. Quack grass and hemp-nettle had the highest densities at 8.0 and 7.1 plants m-2, respectively. The highest weed density (103 plants m-2) was found in oats (Avena sativa) grown after a forage crop. The lowest density (24 plants m-2) was found in wheat (Triticum aestivum) grown after potatoes (Solarium tuberosum). Most of the abundant species were tolerant to MCPA, the most commonly used herbicide. Farmers could make major improvements in cereal weed control by choosing a herbicide that would control species tolerant to MCPA or 2,4-D, and using preplant or postharvest weed control to minimize the impact of perennial weeds