Phoma stem canker disease on oilseed rape (Brassica napus) in China is caused by Leptosphaeria biglobosa ‘brassicae’

This document is the Accepted Manuscript version of the following article: Ze Liu, Akinwunmi O. Latunde-Dada, Avice M. Hall, Bruce D. L. Fitt, ‘Phoma stem canker disease on oilseed rape (Brassica napus) in China is caused by Leptosphaeria biglobosa ‘brassicae’’, European Journal of Plant Pathology, Vol. 140(4): 841-857, December 2014. The final publication is available at Springer via: http://dx.doi.org/10.1007/s10658-014-0513-7 © Koninklijke Nederlandse Planteziektenkundige Vereniging 2014Phoma stem canker of oilseed rape (Brassica napus) is a globally important disease that is caused by the sibling ascomycete species Leptosphaeria maculans and L. biglobosa. Sixty fungal isolates obtained from oilseed rape stems with phoma stem canker disease symptoms collected from four provinces in China in 1999, 2005 and 2006 were all identified as Leptosphaeria biglobosa, not L. maculans, by PCR diagnostics based on species-specific primers. There were no differences in cultural characteristics (e.g. pigmentation and in vitro growth) between these L. biglobosa isolates from China and those of 37 proven L. biglobosa isolates from Europe or Canada. In studies using amplified fragment length polymorphism (AFLP) markers, Chinese L. biglobosa populations were genetically more similar to European L. biglobosa populations than to the more diverse Canadian L. biglobosa populations. Sequencing of gene fragments of β-tubulin, actin and the internal transcribed spacer (ITS) region of rDNA from L. biglobosa isolates from China, Europe, Australia and Canada showed a closer taxonomic similarity of Chinese L. biglobosa to the European L. biglobosa ‘brassicae’ than to Canadian L. biglobosa ‘canadensis’ or to the Australian L. biglobosa ‘occiaustralensis’ or ‘australensis’ subclades. These results suggest that the Chinese L. biglobosa population in this study is in the same subclade as European L. biglobosa ‘brassicae’ populationsPeer reviewe

Genetic basis of control of Rhynchosporium secalis infection and symptom expression in barley

The genetic basis of several different components of resistance to Rhynchosporium secalis in barley was investigated in a mapping population derived from a cross between winter and spring barley types. Both the severity of visual disease symptoms and amount of R. secalis DNA in leaf tissues were assessed in field trials in Scotland in the 2007/2008 and 2008/2009 growing seasons. Relative expression of symptoms was defined as the residual values from a linear regression of amount of R. secalis DNA against visual plot disease score at GS 50. Amount of R. secalis DNA and visual disease score were highly correlated traits and identified nearly identical QTL. The genetic control of relative expression of symptoms was less clear. However, a QTL on chromosome 7H was identified as having a significant effect on the expression of visual disease symptoms relative to overall amount of R. secalis colonisationPeer reviewedFinal Accepted Versio

A Test of Highly Optimized Tolerance Reveals Fragile Cell-Cycle Mechanisms Are Molecular Targets in Clinical Cancer Trials

Robustness, a long-recognized property of living systems, allows function in the face of uncertainty while fragility, i.e., extreme sensitivity, can potentially lead to catastrophic failure following seemingly innocuous perturbations. Carlson and Doyle hypothesized that highly-evolved networks, e.g., those involved in cell-cycle regulation, can be resistant to some perturbations while highly sensitive to others. The “robust yet fragile” duality of networks has been termed Highly Optimized Tolerance (HOT) and has been the basis of new lines of inquiry in computational and experimental biology. In this study, we tested the working hypothesis that cell-cycle control architectures obey the HOT paradigm. Three cell-cycle models were analyzed using monte-carlo sensitivity analysis. Overall state sensitivity coefficients, which quantify the robustness or fragility of a given mechanism, were calculated using a monte-carlo strategy with three different numerical techniques along with multiple parameter perturbation strategies to control for possible numerical and sampling artifacts. Approximately 65% of the mechanisms in the G1/S restriction point were responsible for 95% of the sensitivity, conversely, the G2-DNA damage checkpoint showed a much stronger dependence on a few mechanisms; ∼32% or 13 of 40 mechanisms accounted for 95% of the sensitivity. Our analysis predicted that CDC25 and cyclin E mechanisms were strongly implicated in G1/S malfunctions, while fragility in the G2/M checkpoint was predicted to be associated with the regulation of the cyclin B-CDK1 complex. Analysis of a third model containing both G1/S and G2/M checkpoint logic, predicted in addition to mechanisms already mentioned, that translation and programmed proteolysis were also key fragile subsystems. Comparison of the predicted fragile mechanisms with literature and current preclinical and clinical trials suggested a strong correlation between efficacy and fragility. Thus, when taken together, these results support the working hypothesis that cell-cycle control architectures are HOT networks and establish the mathematical estimation and subsequent therapeutic exploitation of fragile mechanisms as a novel strategy for anti-cancer lead generation

Search for physics beyond the standard model in events with two leptons of same sign, missing transverse momentum, and jets in proton-proton collisions at root s=13TeV

A data sample of events from proton–proton collisions with two isolated same-sign leptons, missing transverse momentum, and jets is studied in a search for signatures of new physics phenomena by the CMS Collaboration at the LHC. The data correspond to an integrated luminosity of 35.9 fb−1, and a center-of-mass energy of 13 TeV. The properties of the events are consistent with expectations from standard model processes, and no excess yield is observed. Exclusion limits at 95% confidence level are set on cross sections for the pair production of gluinos, squarks, and same-sign top quarks, as well as top-quark associated production of a heavy scalar or pseudoscalar boson decaying to top quarks, and on the standard model production of events with four top quarks. The observed lower mass limits are as high as 1500 GeV for gluinos, 830 GeV for bottom squarks. The excluded mass range for heavy (pseudo)scalar bosons is 350–360 (350–410) GeV. Additionally, model-independent limits in several topological regions are provided, allowing for further interpretations of the results

Quantitative PCR analysis of abundance of airborne propagules of Leptosphaeria species in air samples from different regions of Poland

When airborne propagules of Leptosphaeria maculans and L. biglobosa were collected in Poland at three ecologically different sites from 1 September to 30 November in 2004 to 2008, using a Hirst-type seven-day volumetric spore trap, there were fluctuations in timing of ascospore release and diverse ratios between airborne propagules of both species depending on season, field location and weather conditions. The detection was done using the microscope as well as quantitative PCR with species-specific primers targeted against fragments of β-tubulin genes and quantified with a dual-labelled fluorescent probe approach. This detection chemistry is described for the first time for L. maculans and L. biglobosa. Its advantage over the previous ITS-based SYBR-Green chemistry resides in improved sensitivity and the virtual absence of false positives in the detection of these fungi. There were significant, positive correlations between data obtained using visual assessment of ascospore numbers and DNA concentrations that were measured by qPCR. Climatic differences between the oilseed rape growing regions could have significantly affected the biological processes of pseudothecial maturation and ascospore development of the pathogens. The data suggest that regular rain events of intermediate intensity recorded in the Maritime region favoured the maturation of the pathogen more than the drier weather recorded in the Silesia or Pomerania regions. It was observed that the number of rainy days was of greater importance than the cumulative rainfall to obtain the generative sporulation of the pathogen. Accurate detection of airborne inoculum of pathogenic Leptosphaeria spp. facilitates improved targeting of disease management decisions for oilseed rape protection against phoma stem canker and stem necrosis diseases.Peer reviewe

Fitness cost of virulence differs between the AvrLm1 and AvrLm4 loci in Leptosphaeria maculans (phoma stem canker of oilseed rape)

“The original publication is available at www.springerlink.com” Copyright Springer [Full text of this article is not available in the UHRA]To investigate whether the reported fitness cost of virulence at the AvrLm4 locus in Leptosphaeria maculans is common to other loci, near-isogenic (NI) isolates differing at AvrLm1 locus were produced in vitro. Fitness of virulent (avrLm1) or avirulent (AvrLm1) isolates on Brassica napus without the corresponding R (resistance) gene Rlm1 was investigated in controlled environment (CE) and field experiments. Results indicate that there is a measurable fitness cost for avrLm1 compared to AvrLm1 isolates in terms of number of lesions, size of lesions, distance grown through leaf tissue towards the petiole in CE experiments and systemic growth from leaf lesions to stems in field experiments. There were differences in fitness cost between the AvrLm1 and AvrLm4 loci. There was a cultivar effect on fitness cost of virulence at the AvrLm1 locus but not at the AvrLm4 locus. In CE experiments, the optimal temperature for leaf infection was greater for AvrLm4 isolates than for AvrLm1 isolates. Field experiment results suggest that on the same host AvrLm4 isolates are more fit than AvrLm1 isolates in warmer seasons. The fitness cost at the AvrLm4 locus was generally greater than at the AvrLm1 locus, suggesting that the corresponding R gene Rlm4 may be more suitable than Rlm1 for redeployment in commercial cultivars after an interval of a few years.Peer reviewe