Yield of ‘Superior’ potatoes (Solanum tuberosum) and dynamics of root-lesion nematode (Pratylenchus penetrans) populations following “nematode suppressive” cover crops and fumigation

De 1992 à 1996, des études ont été menées à Simcoe, Ontario, pour évaluer diverses espèces de cultures de couverture comme alternatives possibles à la fumigation précédant la culture de la pomme de terre (Solanum tuberosum). Le seigle (Secale cereale), une culture de couverture hivernante fréquente dans les systèmes de production de légumes, est un excellent hôte pour le nématode des lésions racinaires (Pratylenchus penetrans) et lui procure un hôte convenable pour hiverner dans les sols sableux grossiers. Les fumigants Vorlex Plus CP et Telone IIB ont été comparés à la moutarde ‘Domo’ (Brassica juncea) pour les années 1993 et 1994 de production de pommes de terre. Le seigle mélangé au trèfle rouge (Trifolium pratense) a été inclus en tant que système connu de culture de couverture hôte. Les plantes cyanogénétiques telles la moutarde ‘Domo’ (1994) ou la moutarde ‘Cutlass’ (1995, 1996), le canola ‘Forge’ (Brassica rapa), les hybrides sorgho/sorgho herbacé ‘Sordan 79’ et ‘Trudan 8’ (Sorghum bicolor) et le lin (Linum usitatissimum) ont été comparées au fumigant Vorlex Plus CP et au sorgho ‘NK557’ (Sorghum vulgare) quant à leurs effets sur les rendements de la pomme de terre et sur les nématodes. Une fumigation superficielle (15 cm) et une en profondeur (45 cm) avec le Vorlex Plus CP ont aussi été comparées pour les années 1994 à 1996 de production de pommes de terre. Il y avait peu de différence de décelable entre tous les traitements en pourcentage ou en jours pour atteindre 50 % d’émergence des pommes de terre. Les rendements totaux et vendables les plus élevés ont été obtenus avec la fumigation au Telone IIB, puis avec la fumigation au Vorlex Plus CP et la moutarde ‘Domo’, suivis du traitement témoin et de la couverture de seigle et de trèfle rouge. Les populations de nématodes ont dépassé le seuil de 1000 kg-1 de sol pour tous les traitements et étaient les plus élevées pour les pommes de terres qui suivaient la couverture de seigle et de trèfle rouge. Les rendements et la répression des nématodes avec les hybrides sorgho/sorgho herbacé et les moutardes semblaient intermédiaires entre la fumigation et la non-fumigation. Toutes les cultures de couverture semblaient être des hôtes au champ pour le nématode des lésions racinaires et la réduction des niveaux des populations n’apparaît que lorsque intervient la destruction par l’hiver. La mortalité des nématodes était excellente avec la fumigation et n’était surpassée que par la mortalité hivernale après incorporation de ‘Sordan 79’. L’emploi du ‘Sordan 79’ pendant au moins une partie de l’été suivi de son incorporation a été une alternative à la fumigation précédant la culture de la pomme de terre. Le passage en profondeur d’un chisel semble réduire les populations de nématodes probablement par un effet physique. Là où les populations de nématodes le justifient, une fumigation en profondeur avant la culture de la pomme de terre semble de mise.Studies were conducted at Simcoe, Ontario from 1992 to 1996 to evaluate various cover crop species as possible alternatives to fumigation prior to potatoes (Solanum tuberosum). Cereal rye (Secale cereale), a common overwinter cover crop in vegetable production systems, is an excellent host for the root-lesion nematode (Pratylenchus penetrans) and provides a suitable overwintering host on coarse sandy soils. Vorlex Plus CP and Telone IIB fumigants were compared to 'Domo' mustard (Brassica juncea) for the 1993 and 1994 potato crop years. Rye plus red clover (Trifolium pratense) was included as a known host cover crop system. Cyanogenic plants including 'Domo' mustard (1994) or 'Cutlass' mustard (1995, 1996), 'Forge' canola (Brassica rapa), 'Sordan 79' and 'Trudan 8' sorghum-sudangrass hybrids (Sorghum bicolor), and flax (Linum usitatissimum) were compared to Vorlex Plus CP fumigant and 'NK557' sorghum (Sorghum vulgare) for effects on potato yield and nematodes. Shallow (15 cm) and deep (45 cm) fumigation with Vorlex Plus CP were also compared prior to potatoes for the 1994 to 1996 crop years. There was little detectable difference in percent or days to 50% emergence of potatoes following any treatment. Highest total and marketable yields resulted from Telone IIB fumigation, then Vorlex Plus CP fumigation and 'Domo' mustard, followed by control and rye plus red clover cover. Populations of nematodes surpassed the threshold of 1000 kg-1 soil in all treatments and were highest in potatoes following rye plus red clover. Yield and nematode control following sorghum-sudangrass hybrids and mustards appeared to be intermediate between fumigated and not fumigated. All of the cover crops appeared to be root-lesion nematode hosts in the field, and reduction of population levels appeared to result after incorporation or nematode winterkill. Nematode mortality was excellent with fumigation and next best from kill over the winter after 'Sordan 79' incorporation. 'Sordan 79' grown over at least part of the summer followed by incorporation was an alternative to fumigation prior to potatoes. Deep chiselling appears to reduce nematode population, possibly by physical action. Where nematode populations warrant, deep fumigation prior to potatoes appears to be of merit

Inhibition of Pratylenchus penetrans by intercroping of Rudbeckia hirta and Lycopersicon esculentum in pot cultivation

Dans la culture en pot en serre chaude sur une période de 6 semaines, la densité de population du Pratylenchus penetrans a diminué sévèrement avec Rudbeckia hirta seul et avec un mélange de R. hirta et de tomate, tandis que la tomate seule a supporté la population de nématodes. La réduction de population est attribuée en partie à l'effet nématicide connu du thiarubrine C de R. hirta. De façon générale, la présence du R. hirta dans le pot de tomate a simplement supprimé légèrement la croissance de l'une ou l'autre des plantes durant les 6 semaines.In greenhouse pot culture over a 6-week period, population density of Pratylenchus penetrans declined pronouncedly both under Rudbeckia hirta alone and under a R. hirta - tomato combination, whereas tomato alone supported the nematode population. Population reduction is attributed in part to the known nematicidal effect of thiarubrine C in R. hirta. Overall, the presence of R. hirta in the tomato pot only slightly suppressed growth of either plant during the 6 weeks

Fluctuations of populations of the pin nematode Paratylenchus projectus under selected potato management practices

Des expériences sur la distribution et la survie du nématode de goupille Paratylenchus projectus dans des systèmes de production de pomme de terre et sur son contrôle par divers mécanismes sont décrites. Les meilleures stratégies de gestion pour le nématode de goupille incluent l'utilisation du lin textile ou d'une moutarde ou canola à haut-glucosinolate, l'utilisation de 'Trudan 8' sudangrass comme ajout de matière organique dans le sol, et le labourage peu profond mais complet d'un sol sablonneux en automne ou au début du printemps pour perturber le sol. En général, plusieurs graminées et légumineuses devraient être évitées comme cultures de protection.Experiments on the distribution and survival of pin nematode Paratylenchus projectus in potato growing systems and on its control by various mechanisms are described. Preferable management strategies for the pin nematode include the use of flax or a high-glucosinolate mustard or canola, the use of 'Trudan 8' sudangrass to add organic matter into the soil, and shallow but thorough tillage of a sandy soil in the fall or in early spring to disrupt the soil. In general, many grasses and legumes should be avoided as cover crops

A note on the occurrence of root lesion nematodes under native sand-prairie plant species in the Regional Municipality of Haldimand-Norfolk, Ontario

Le nématode des lésions des racines (Pratylenchus penetrans), le nématode phytoparasite le plus important du sud de l'Ontario, possède une gamme d'hôtes extrêmement large. À cause de la nécessité de réprimer ces parasites avec des cultures recouvrantes qui sont peu ou pas hôtes, plusieurs espèces indigènes des prairies sablonneuses ont été évaluées pour leur susceptibilité au nématode des lésions. Onze espèces appartenant à quatre familles (Asclepiadaceae, Asteraceae, Poaceae et Fabaceae) ont été identifiées commes des hôtes faibles. Les populations très faibles de P. penetrans sur ces espèces indiquent qu'elles pourraient avantageusement servir comme cultures recouvrantes.The root lesion nematode Pratylenchus penetrans, which is the most important plant-parasitic nematode in southern Ontario, has an extremely wide host range. Because of the need to suppress lesion nematodes with cover-crop species which are poor or non-hosts of this parasite, a number of native sand-prairie species were evaluated for susceptibility. Eleven plant species belonging to the families Asclepiadaceae, Asteraceae, Poaceae and Fabaceae were determined to support very low numbers of P. penetrans and consequently to have potential as beneficial cover-crops

A new terrestrial palaeoenvironmental record from the Bering Land Bridge and context for human dispersal

Palaeoenvironmental records from the now-submerged Bering Land Bridge (BLB) covering the Last Glacial Maximum (LGM) to the present are needed to document changing environments and connections with the dispersal of humans into North America. Moreover, terrestrially based records of environmental changes are needed in close proximity to the re-establishment of circulation between Pacific and Atlantic Oceans following the end of the last glaciation to test palaeo-climate models for the high latitudes. We present the first terrestrial temperature and hydrologic reconstructions from the LGM to the present from the BLB’s south-central margin. We find that the timing of the earliest unequivocal human dispersals into Alaska, based on archaeological evidence, corresponds with a shift to warmer/wetter conditions on the BLB between 14 700 and 13 500 years ago associated with the early Bølling/Allerød interstadial (BA). These environmental changes could have provided the impetus for eastward human dispersal at that time, from Western or central Beringia after a protracted human population standstill. Our data indicate substantial climate-induced environmental changes on the BLB since the LGM, which would potentially have had significant influences on megafaunal and human biogeography in the region. © 2018 The Authors

A discursive approach to narrative accounts of hearing voices and recovery

Substantive objective: To research the range of discursive constructions ‘recovered’ voice hearers employ to describe hearing voices and the implications for positioning and subjectivity (what can be thought and felt) using each construction. Methodological objective and method: To explore a ‘sympathetic’ application of Foucauldian discourse analysis, adapting Willig’s (2008 Willig, C. 2008. Introducing Qualitative Research in Psychology, Maidenhead: Open University Press. ) method, analysing two published accounts. Results and conclusions: Heterogeneous discursive constructions for talking about hearing voices were identified, including: ‘many-’selves’’, ‘taking-the-lead-in-your-own-recovery’, ‘voices-as-an-’imagined-world’’ and ‘voices-as-a-coping-strategy-for-dealing-with-trauma’. The discourse of the biomedical model was not prominent, suggesting alternate discursive constructions may create subjects with a greater capacity for ‘living with voices’ and create a subjectivity from which vantage point the experience holds meaning and value and can be integrated into life experiences. This research may have useful clinical applications for mental health services aiming to collaboratively explore service users’ ways of understanding hearing voices

Divided communities and contested landscapes: Mobility, development and shifting identities in migrant destination sites in Papua New Guinea

Internal conflicts at the local and national levels in several South Pacific countries have revealed the fragility of national unity and the difficulties nations face in governing and managing their own economic development. In Papua New Guinea, the focus of this paper, an uncertain economic future for many rural and urban communities, and rising inequalities in income opportunities and access to resources, have coincided with greater intolerance of migrants at sites of high in-migration by customary landowners and provincial and local authorities. This paper draws on fieldwork undertaken in the major oil palm growing regions of Papua New Guinea where migrants from densely populated regions of the country have settled on state land alienated from customary landowners. We examine how struggles over land, resource control and development are polarising migrant and landowner identities resulting in increasing tensions and episodic communal violence. A settler identity is emerging based on a narrative of nation building and national development, while an ethno-regional identity amongst customary landowners is undermining the citizen rights of migrants and challenging the role and authority of the state in land matters

Eco-evolutionary dynamics on deformable fitness landscapes

Conventional approaches to modelling ecological dynamics often do not include evolutionary changes in the genetic makeup of component species and, conversely, conventional approaches to modelling evolutionary changes in the genetic makeup of a population often do not include ecological dynamics. But recently there has been considerable interest in understanding the interaction of evolutionary and ecological dynamics as coupled processes. However, in the context of complex multi-species ecosytems, especially where ecological and evolutionary timescales are similar, it is difficult to identify general organising principles that help us understand the structure and behaviour of complex ecosystems. Here we introduce a simple abstraction of coevolutionary interactions in a multi-species ecosystem. We model non-trophic ecological interactions based on a continuous but low-dimensional trait/niche space, where the location of each species in trait space affects the overlap of its resource utilisation with that of other species. The local depletion of available resources creates, in effect, a deformable fitness landscape that governs how the evolution of one species affects the selective pressures on other species. This enables us to study the coevolution of ecological interactions in an intuitive and easily visualisable manner. We observe that this model can exhibit either of the two behavioural modes discussed in the literature; namely, evolutionary stasis or Red Queen dynamics, i.e., continued evolutionary change. We find that which of these modes is observed depends on the lag or latency between the movement of a species in trait space and its effect on available resources. Specifically, if ecological change is nearly instantaneous compared to evolutionary change, stasis results; but conversely, if evolutionary timescales are closer to ecological timescales, such that resource depletion is not instantaneous on evolutionary timescales, then Red Queen dynamics result. We also observe that in the stasis mode, the overall utilisation of resources by the ecosystem is relatively efficient, with diverse species utilising different niches, whereas in the Red Queen mode the organisation of the ecosystem is such that species tend to clump together competing for overlapping resources. These models thereby suggest some basic conditions that influence the organisation of inter-species interactions and the balance of individual and collective adaptation in ecosystems, and likewise they also suggest factors that might be useful in engineering artificial coevolution

Measurement of the polarisation of W bosons produced with large transverse momentum in pp collisions at sqrt(s) = 7 TeV with the ATLAS experiment

This paper describes an analysis of the angular distribution of W->enu and W->munu decays, using data from pp collisions at sqrt(s) = 7 TeV recorded with the ATLAS detector at the LHC in 2010, corresponding to an integrated luminosity of about 35 pb^-1. Using the decay lepton transverse momentum and the missing transverse energy, the W decay angular distribution projected onto the transverse plane is obtained and analysed in terms of helicity fractions f0, fL and fR over two ranges of W transverse momentum (ptw): 35 < ptw < 50 GeV and ptw > 50 GeV. Good agreement is found with theoretical predictions. For ptw > 50 GeV, the values of f0 and fL-fR, averaged over charge and lepton flavour, are measured to be : f0 = 0.127 +/- 0.030 +/- 0.108 and fL-fR = 0.252 +/- 0.017 +/- 0.030, where the first uncertainties are statistical, and the second include all systematic effects.Comment: 19 pages plus author list (34 pages total), 9 figures, 11 tables, revised author list, matches European Journal of Physics C versio

Observation of a new chi_b state in radiative transitions to Upsilon(1S) and Upsilon(2S) at ATLAS

The chi_b(nP) quarkonium states are produced in proton-proton collisions at the Large Hadron Collider (LHC) at sqrt(s) = 7 TeV and recorded by the ATLAS detector. Using a data sample corresponding to an integrated luminosity of 4.4 fb^-1, these states are reconstructed through their radiative decays to Upsilon(1S,2S) with Upsilon->mu+mu-. In addition to the mass peaks corresponding to the decay modes chi_b(1P,2P)->Upsilon(1S)gamma, a new structure centered at a mass of 10.530+/-0.005 (stat.)+/-0.009 (syst.) GeV is also observed, in both the Upsilon(1S)gamma and Upsilon(2S)gamma decay modes. This is interpreted as the chi_b(3P) system.Comment: 5 pages plus author list (18 pages total), 2 figures, 1 table, corrected author list, matches final version in Physical Review Letter