Effects of granular nematicides on the infection of potatoes by Rhizoctonia solani

The granular nematicides aldicarb, oxamyl and ethoprophos often are applied to control plant parasitic nematodes. However, the use of these pesticides may have some disadvantages. In field trials, they increased stem infection of potatoes caused by Rhizoctonia solani Kühn and incidence of black scurf (sclerotia of R. solani ) on tubers. This thesis, reports about possible mechanisms involved in the increased infection in nematicide treated fields. The effects of granular nematicides were studied on:- the pathogenicity of R. solani (Chapters 2 and 3)- the susceptibility of the host plant (Chapter 3)- the microbial antagonism to R. solani (Chapter 2)- the mycophagous soil fauna, i.e. nematodes (Chapters 5 and 7) or springtails and mites (Chapters 6 and 7)Ethoprophos was fungitoxic to R. solani . On Czapek Dox agar (CDA), the EC 50 of the compound was 49 mg l -1and at 100 mg l -1there was a total growth inhibition. Oxamyl showed a slight fungitoxicity. At 100 Mg 1-1 oxamyl in CDA, the growth of R. solani was reduced by 26 %. Aldicarb did not influence the growth of R. solani on CDA, but caused a slight growth stimulation on potato dextrose agar (PDA).The carbamate compounds aldicarb and oxamyl are systemically transported in plants. The presence inside the plant might, therefore, have some effect on the host-plant resistance to R. solani . The organophosphorus compound ethoprophos is not known to have a systemic activity, so it differs from the other two nematicides with respect to the uptake by the host plant. It was therefore, less likely that the increased infection by R. solani in nematicide-treated soil, was due to a reduced host-plant resistance. Laboratory experiments supplied the evidence that the nematicides did not reduce host-plant resistance.Ethoprophos caused an initial growth inhibition of potato sprouts, but immediately after their emergence, growth was promoted. In laboratory experiments carried out at 15 °C in a growth chamber, the emergence of sprouts was delayed by three days, when tubers were planted in ethoprophos-treated soil. However, most probably due to the fungitoxicity of ethoprophos, the appearance of lesions on the stems was delayed by nine days in this treatment. Oxamyl showed similar effects to ethoprophos, but to a lesser extent, while aldicarb did neither influence sprout development nor the appearance of lesions.The stages in the infection process, including growth of runner hyphae, branching of hyphae on the stem surface, formation of infection cushions and the relationship between size of the infection cushions and size of lesions, were not influenced by any of the nematicides.The previous observations made an indirect effect highly evident. In a study on the infection process was found that the size of lesions was proportional to the size of the infection cushions (dense masses of mycelium from which R. solani penetrates the plant). Any agent that changes the size of infection cushions will alter, therefore, the severity of the disease.By far the most important mycoparasite of R. solani in Dutch potato fields is Verticillium biguttatum , so the study on effects on mycoparasites was focussed on this fungus. The growth of V. biguttatum was strongly stimulated by aldicarb and ethoprophos on potato dextrose agar plates covered with mycelium of R. solani . The mechanism involved was not studied. In the nematicide-treated fields, the incidence of V. biguttatum on stolons was increased. This may be due to an increased availability of substrate (i.e. mycelium of R. solani ) or a reduced activity of the mycophagous soil fauna, as well as from a direct stimulation by the nematicide. At the recommended dosages of aldicarb, oxamyl or ethoprophos, an effect on soil fungistasis was not found, neither in laboratory experiments nor in field experiments.The laboratory experiments indicated that the most probable explanation for the increased disease severity of R. solani in nematicide-treated fields is a suppression of the mycophagous soil fauna. In the experimental fields, the most abundant mycophagous nematodes were Aphelenchus avenae and Aphelenchoides spp. These nematodes could be reared on petri-dishes covered with mycelium of R. solani . In the rhizosphere of plants of which the foliage was removed, numbers of A. avenae increased dramatically. Outside the rhizosphere, only very low numbers of A. avenae and Aphelenchoides spp. were found. It was assumed that the large increase was due to a rapid development of the microflora in the rhizosphere of dying roots. Aldicarb, oxamyl and ethoprophos greatly limited this increase.In a field that had been fumigated with dichloropropene, the granular nematicides hardly affected stem infection and black scurf incidence. Initially, metabolites that may have been formed after fumigation could have had a toxic effect on R. solani . All soil animals were strongly reduced at the beginning of the growing season in the fumigated field. Later in the season, numbers of A. avenae were much higher in the rhizosphere of plants grown in fumigated soil than in non-fumigated soil. Although the granular nematicides reduced numbers of A. avenae also in the fumigated soil, the remaining population density of A. avenae was still high. In nematicide-treated plots, the disease suppression was, therefore, not much lower than in the untreated plots.To simulate potato stems colonized by R. solani , flax straws colonized by the fungus were buried in the field. Mycophagous nematodes rapidly increased on the straws. In aldicarb-treated plots, only low numbers of mycophagous nematodes were observed on these straws. These data show that grazing of mycophagous nematodes on mycelium and probably also on infection cushions of R. solani will be less in nematicide-treated soil than in untreated soil.In one field trial, the effect of the insecticide lindane on R. solani was assessed to discriminate between the role of mycophagous nematodes and mycophagous microarthropods. In lindane-treated plots, stem infection and black scurf incidence were increased to almost the same extent as in aldicarb-treated plots. Lindane did not have any nematicidal activity. This indicates that at least in this field microarthropods may also reduce R. solani by grazing. Aldicarb, ethoprophos and lindane reduced the numbers of most springtails and mites in potato fields. The most abundant springtails were Tullbergia krausbaueri , Isotoma notabilis and Folsomia fimetaria , and the most abundant mites were Pygmephorus sellnicki , Pygmephorus blumentritti , Coccotydeus sp. and Histiosoma litorale . Numbers of Pygmephorus spp. were not reduced in aldicarb- and ethoprophos-treated plots. T. krausbaueri was reduced in lindaneand ethoprophos-treated plots, but only slightly in aldicarb- treated plots.In the laboratory, T. krausbaueri , F. fimetaria and H. litorale could be reared on petri-dishes covered with R. solani or cultures of R. solani in sterilized soil. Pygmephorus spp. and Coccotydeus sp. could not be reared on these cultures, while I. notabilis was not successfully isolated from the field. In laboratory experiments where the microarthropods were introduced in a soil inoculated with R. solani , T. krausbaueri and F. fimetaria caused a strong reduction of stem infection of potatoes. Lowest numbers of T. krausbaueri and F. fimetaria that significantly reduced disease severity were 9800 and 430 individuals per litre soil, respectively. H. litorale did not survive during the experiment, so it was probably not important in grazing on mycelium of R. solani . In similar inoculation experiments, A. avenae was also found to cause a significant reduction in stem infection when inoculated with 500 nematodes per litre. An Aphelenchoides sp. had no effect on stem infection. Nematodes reproduced within a few days at room temperature, while springtails and mites had a much slower reproduction cycle.A. avenae and F. fimetaria seem to be some of the most important mycophagous soil animals that lead to a reduction by R. solani in the field. A smaller contribution in the reduction of disease severity can be expected from T. krausbaueri and other mycophagous soil animals that are only present at low densities. However, some of the species that were not reared in the laboratory on mycelium of R. solani , may also be able to cause a significant reduction of disease severity at low population densities.Any pesticide that reduces the density of mycophagous soil animals will, therefore, facilitate a better development of R. solani . The stimulatory effects of granular nematicides on R. solani on potato seem primarily caused by reduced grazing of the mycophagous soil fauna on the pathogen in nematicide-treated fields.</TT

The clinical value of metabolic syndrome and risks of cardiometabolic events and mortality in the elderly: The Rotterdam study

Background: To evaluate the clinical value of metabolic syndrome based on different definitions [American Heart Association/National Heart, Lung and Blood Institute (AHA/NHLBI), International Diabetes Federation (IDF) and European Group for the Study of Insulin Resistance (EGIR)] in middle-aged and elderly populations. Methods: We studied 8643 participants from the Rotterdam study (1990-2012; mean age 62.7; 57.6% female), a large prospective population-based study with predominantly elderly participants. We performed cox-proportional hazards models for different definitions, triads within definitions and each separate component for the risk of incident type 2 diabetes mellitus, coronary heart disease, stroke, cardiovascular- and all-cause mortality. Results: In our population of 8643 subjects, metabolic syndrome was highly prevalent (prevalence between 19.4 and 42.4%). Metabolic syndrome in general was associated with incident type 2 diabetes mellitus (median follow-up of 6.8years, hazard ratios 3.13-3.78). The associations with coronary heart disease (median follow-up of 7.2years, hazard ratios 1.08-1.32), stroke (median follow-up of 7.7years, hazard ratios 0.98-1.32), cardiovascular mortality (median follow-up of 8.2years, ratios 0.95-1.29) and all-cause mortality (median follow-up of 8.7years, hazard ratios 1.05-1.10) were weaker. AHA/NHLBI- and IDF-definitions showed similar associations with clinical endpoints compared to the EGIR, which was only significantly associated with incident type 2 diabetes mellitus. All significant associations disappeared after correcting metabolic syndrome for its individual components. Conclusions: Large variability exists between and within definitions of the metabolic syndrome with respect to risk of clinical events and mortality. In a relatively old population the metabolic syndrome did not show an additional predictive value on top of its individual components. So, besides as a manner of easy identification of high risk patients, the metabolic syndrome does not seem to add any predictive value for clinical practice

ADAMTS13 activity as a novel risk factor for incident type 2 diabetes mellitus: a population-based cohort study

Aims/hypothesis: ADAMTS13 is a protease that breaks down von Willebrand factor (VWF) multimers into smaller, less active particles. VWF has been associated with an increased risk of incident type 2 diabetes mellitus. Here, we determine whether ADAMTS13 activity and VWF antigen are associated with incident diabetes. Methods: This study included 5176 participants from the Rotterdam Study, a prospective population-based cohort study. Participants were free of diabetes at baseline and followed up for more than 20 years. Cox proportional hazards models were used to examine the association of ADAMTS13 activity and VWF antigen with incident diabetes. Results: ADAMTS13 activity was associated with an increased risk of incident diabetes (HR 1.17 [95% CI 1.08, 1.27]) after adjus

Giant Gravitons - with Strings Attached (III)

We develop techniques to compute the one-loop anomalous dimensions of operators in the ${\cal N}=4$ super Yang-Mills theory that are dual to open strings ending on boundstates of sphere giant gravitons. Our results, which are applicable to excitations involving an arbitrary number of open strings, generalize the single string results of hep-th/0701067. The open strings we consider carry angular momentum on an S$^3$ embedded in the S$^5$ of the AdS$_5\times$S$^5$ background. The problem of computing the one loop anomalous dimensions is replaced with the problem of diagonalizing an interacting Cuntz oscillator Hamiltonian. Our Cuntz oscillator dynamics illustrates how the Chan-Paton factors for open strings propagating on multiple branes can arise dynamically.Comment: 66 pages; v2: improved presentatio

Partonic flow and ϕ\phi-meson production in Au+Au collisions at sNN\sqrt{s_{NN}} = 200 GeV

We present first measurements of the $\phi$-meson elliptic flow ($v_{2}(p_{T})$) and high statistics $p_{T}$ distributions for different centralities from $\sqrt{s_{NN}}$ = 200 GeV Au+Au collisions at RHIC. In minimum bias collisions the $v_{2}$ of the $\phi$ meson is consistent with the trend observed for mesons. The ratio of the yields of the $\Omega$ to those of the $\phi$ as a function of transverse momentum is consistent with a model based on the recombination of thermal $s$ quarks up to $p_{T}\sim 4$ GeV/$c$, but disagrees at higher momenta. The nuclear modification factor ($R_{CP}$) of $\phi$ follows the trend observed in the $K^{0}_{S}$ mesons rather than in $\Lambda$ baryons, supporting baryon-meson scaling. Since $\phi$-mesons are made via coalescence of seemingly thermalized $s$ quarks in central Au+Au collisions, the observations imply hot and dense matter with partonic collectivity has been formed at RHIC.Comment: 6 pages, 4 figures, submit to PR

Measurement of Transverse Single-Spin Asymmetries for Di-Jet Production in Proton-Proton Collisions at s=200\sqrt{s} = 200 GeV

We report the first measurement of the opening angle distribution between pairs of jets produced in high-energy collisions of transversely polarized protons. The measurement probes (Sivers) correlations between the transverse spin orientation of a proton and the transverse momentum directions of its partons. With both beams polarized, the wide pseudorapidity ($-1 \leq \eta \leq +2$) coverage for jets permits separation of Sivers functions for the valence and sea regions. The resulting asymmetries are all consistent with zero and considerably smaller than Sivers effects observed in semi-inclusive deep inelastic scattering (SIDIS). We discuss theoretical attempts to reconcile the new results with the sizable transverse spin effects seen in SIDIS and forward hadron production in pp collisions.Comment: 6 pages total, 1 Latex file, 3 PS files with figure

Novel genetic loci associated with hippocampal volume

The hippocampal formation is a brain structure integrally involved in episodic memory, spatial navigation, cognition and stress responsiveness. Structural abnormalities in hippocampal volume and shape are found in several common neuropsychiatric disorders. To identify the genetic underpinnings of hippocampal structure here we perform a genome-wide association study (GWAS) of 33,536 individuals and discover six independent loci significantly associated with hippocampal volume, four of them novel. Of the novel loci, three lie within genes (ASTN2, DPP4 and MAST4) and one is found 200 kb upstream of SHH. A hippocampal subfield analysis shows that a locus within the MSRB3 gene shows evidence of a localized effect along the dentate gyrus, subiculum, CA1 and fissure. Further, we show that genetic variants associated with decreased hippocampal volume are also associated with increased risk for Alzheimer's disease (rg =-0.155). Our findings suggest novel biological pathways through which human genetic variation influences hippocampal volume and risk for neuropsychiatric illness

Energy dependence of charged pion, proton and anti-proton transverse momentum spectra for Au+Au collisions at \sqrt{s_NN} = 62.4 and 200 GeV

We study the energy dependence of the transverse momentum (pT) spectra for charged pions, protons and anti-protons for Au+Au collisions at \sqrt{s_NN} = 62.4 and 200 GeV. Data are presented at mid-rapidity (|y| < 0.5) for 0.2 < pT < 12 GeV/c. In the intermediate pT region (2 < pT < 6 GeV/c), the nuclear modification factor is higher at 62.4 GeV than at 200 GeV, while at higher pT (pT >7 GeV/c) the modification is similar for both energies. The p/pi+ and pbar/pi- ratios for central collisions at \sqrt{s_NN} = 62.4 GeV peak at pT ~ 2 GeV/c. In the pT range where recombination is expected to dominate, the p/pi+ ratios at 62.4 GeV are larger than at 200 GeV, while the pbar/pi- ratios are smaller. For pT > 2 GeV/c, the pbar/pi- ratios at the two beam energies are independent of pT and centrality indicating that the dependence of the pbar/pi- ratio on pT does not change between 62.4 and 200 GeV. These findings challenge various models incorporating jet quenching and/or constituent quark coalescence.Comment: 19 pages and 6 figure

Meta-analysis of type 2 Diabetes in African Americans Consortium

Type 2 diabetes (T2D) is more prevalent in African Americans than in Europeans. However, little is known about the genetic risk in African Americans despite the recent identification of more than 70 T2D loci primarily by genome-wide association studies (GWAS) in individuals of European ancestry. In order to investigate the genetic architecture of T2D in African Americans, the MEta-analysis of type 2 DIabetes in African Americans (MEDIA) Consortium examined 17 GWAS on T2D comprising 8,284 cases and 15,543 controls in African Americans in stage 1 analysis. Single nucleotide polymorphisms (SNPs) association analysis was conducted in each study under the additive model after adjustment for age, sex, study site, and principal components. Meta-analysis of approximately 2.6 million genotyped and imputed SNPs in all studies was conducted using an inverse variance-weighted fixed effect model. Replications were performed to follow up 21 loci in up to 6,061 cases and 5,483 controls in African Americans, and 8,130 cases and 38,987 controls of European ancestry. We identified three known loci (TCF7L2, HMGA2 and KCNQ1) and two novel loci (HLA-B and INS-IGF2) at genome-wide significance (4.15 × 10(-94)<P<5 × 10(-8), odds ratio (OR)  = 1.09 to 1.36). Fine-mapping revealed that 88 of 158 previously identified T2D or glucose homeostasis loci demonstrated nominal to highly significant association (2.2 × 10(-23) < locus-wide P<0.05). These novel and previously identified loci yielded a sibling relative risk of 1.19, explaining 17.5% of the phenotypic variance of T2D on the liability scale in African Americans. Overall, this study identified two novel susceptibility loci for T2D in African Americans. A substantial number of previously reported loci are transferable to African Americans after accounting for linkage disequilibrium, enabling fine mapping of causal variants in trans-ethnic meta-analysis studies.Peer reviewe

Search for leptophobic Z ' bosons decaying into four-lepton final states in proton-proton collisions at root s=8 TeV

Peer reviewe