Evaluation of resistance reaction of maize germplasm to common foliar diseases in Kenya

Use of resistance varieties is the most practical method of managing crop diseases. There is a great variation in terms of resistance reaction to diseases among the various maize germplasm and with the liberization of seed market, the sector has witnessed proliferation of massive introduction of new varieties whose reaction to diseases cannot be ascertained. This study was conducted to evaluate the reaction of maize varieties to northern leaf blight (NLB), common maize rust, gray leaf spot (GLS) and maize streak disease (MSD). The experiment was conducted at Kabete Field Station, University of Nairobi for two seasons namely short rains and long rains. The germplasm was bought from the commercial seed stockists and the landraces obtained from KARI Katumani and from farmers. The diseases were assessed by monitoring and scoring for disease incidence and severity. The appropriate scoring keys were used for determination of disease severity. All the varieties showed symptoms of the four diseases in both seasons but the intensity of the diseases differed significantly among the different varieties. Disease incidence was highest for common rust with a mean of 14.29% for the variety DH04, while disease incidence was highest (19.21%) for northern leaf blight in season two for Kinyanya which is a landrace. Gray leaf spot and the common smuts had the lowest mean incidence ranging from 0 to 0.25% for common smut and 0 to 2.6% for gray leaf spot. Season two had comparatively higher disease incidence means compared to season one. Meteorological data showed that season two had more rains and this explains the reasons behind this. Though all the varieties screened were found to be affected by the diseases to various levels, the varieties displayed significant differences in the disease incidence and severity. This shows that use of resistance varieties should be considered in the management of maize diseases. Focus should also be on pyramiding genes for resistance in the breeding programmes to develop varieties with multiple resistance to different diseases. Key words: Disease incidence and severity, disease score, symptoms, varietie

Susceptibility of common weeds and cultivated crops in major maize growing agroecological zones of Uganda to viruses causing maize lethal necrosis disease

Maize lethal necrosis (MLN) disease is caused when maize plants become co-infected with Maize chlorotic mottle virus (MCMV) and potyviruses notably Sugarcane Mosaic Virus (SCMV). Apart from maize, little is known about susceptibility of weed species and cultivated crop species usually growing in proximity with maize to MLN viruses in Uganda. The common weeds and crop plants were mechanically inoculated with combined sap from MCMV and SCMV infected maize plants. Samples were tested for MLN causing viruses by Double Antibody Sandwich Enzyme-Linked Immunosorbent Assay (DAS-ELISA) and Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR). The weeds that were susceptible to MCMV were Digitaria abyssinica, Eleusine africana and Roetboellia cochinchinensis; while those susceptible to SCMV were Pennisetum purpureum, Panicum maximum and Roetboellia cochinchinensis. The cultivated crops were susceptible only to MCMV and included cassava (Manihot esculenta), groundnut (Arachis hypogaea) and bean (Phaseolus vulgaris). Common weeds and cultivated crops growing close to maize in Uganda have differential susceptibility to MLN causing viruses and can act as reservoirs of MLN causing viruses. It is critical to identify non-MLN hosts in cultivated crops for crop rotation and early weeding to reduce on MLN virus inoculum in cropping syste

Optimisation of a somatic embryogenesis and transformation protocol for farmer-preferred cassava cultivars in Kenya

Cassava ( Manihot esculenta Crantz ) is a major food crop in developing countries, and holds potential for industrial use. It is, however, affected by various biotic and abiotic stresses that greatly affect its production. The existing regeneration and transformation protocols are not compatible with all cassava cultivars, thus efficient and robust transformation and regeneration protocols for farmer-preferred cultivars need to be optimised for ease of transfer of novel genes. The objective of this study was to develop an efficient transformation and regeneration protocol for a farmer-preferred Kenyan cassava cultivar. We cultured immature leaf lobe and stem explants on Murashige and Skoog (MS) medium, supplemented with varying concentrations of 2,4-dichlorophenoxyacetic acid (2,4-D), Picloram and \ue1-naphthalene acetic acid (NAA). Plants were recovered on media with 6-Benzylaminopurine (BAP) and GA3 under a 16 hour light/8 hour darkness photoperiod regime. Results showed high regeneration and transformation frequencies for both cultivars. High frequencies of callus induction (>98%) for both cultivars, were obtained when 2,4-D and Picloram were used. Similarly, both auxins initiated somatic embryogenesis, with Picloram producing the highest frequency of somatic embryos (>92%) in TMS 60444, using stem explants. Gus assays revealed high frequencies of transformation of >77% (TMS 60444) and 60% (Kibanda meno mkubwa). This protocol offers promising perspectives for rapid improvement of these cultivars and, therefore, provides a platform for cleaning planting materials, as well as cassava genetic improvement programmes such as control of viral diseases.Le manioc ( Manihot esculenta Crantz ) est une culture vivri\ue8re de grande importance pour les pays en d\ue9veloppement, avec un potentiel pour l\u2019usage industriel. N\ue9anmoins, le manioc est sujet \ue0 des stress d\u2019origines biotique et abiotique, affectant sa production. Les protocoles de r\ue9g\ue9n\ue9ration et de transformation existante ne sont pas compatibles avec toutes les accessions de manioc. Ainsi, il est n\ue9cessaire de d\ue9velopper des protocoles de r\ue9g\ue9n\ue9ration et de transformation efficaces pour les accessions adopt\ue9es par les paysans, afin de faciliter les transferts de g\ue8nes d\u2019int\ue9r\ueat. L\u2019objectif de cet etude \ue9tait de d\ue9velopper un protocole de r\ue9g\ue9n\ue9ration et de transformation adapte a la vari\ue9t\ue9 de manioc. Des feuilles et tiges immatures ont \ue9t\ue9 cultiv\ue9es sur des media Murashige et Skoog (MS), auxquels diff\ue9rentes concentrations de 2,4-dichlorophenoxyacetic acide (2,4-D), Picloram et \ue1-naphtal\ue8ne ac\ue9tique acide (NAA). Les plantes ont \ue9t\ue9 recouvertes de 6-Benzylaminopurine (BAP) et GA3 sous une photop\ue9riode de 16h jour/8h nuit. Les r\ue9sultats ont montr\ue9 des fr\ue9quences \ue9lev\ue9es de r\ue9g\ue9n\ue9ration et de transformation pour les deux cultivars Kibanda meno mkubwa et TMS 60444. Des fr\ue9quences \ue9lev\ue9es d\u2019induction de callosit\ue9s (>98%) ont \ue9t\ue9 obtenues pour les deux cultivars, lorsque 2,4-D et Picloram ont \ue9t\ue9 utilis\ue9s. De la m\ueame fa\ue7on, les deux embryogen\ue8ses somatiques initi\ue9es a l\u2019auxine, avec des explants de tiges et du Picloram ont exhibe la fr\ue9quence la plus \ue9lev\ue9e d\u2019embryon somatique (>92%) en TMS 60444. Des essais de Gus ont r\ue9v\ue9l\ue9s des fr\ue9quences \ue9lev\ue9es de transformation >77% (TMS 60444) et 60% (Kibanda meno mkubwa). Ce protocole offre des perspectives pour l\u2019am\ue9lioration rapide de ces cultivars, et par cons\ue9quent, fournit une plateforme pour la production de mat\ue9riels de culture propres, mais aussi servira d\u2019outil dans les programmes d\u2019am\ue9lioration g\ue9n\ue9tique visant la lutte contre les maladies virales

Multilateral benefit-sharing from digital sequence information will support both science and biodiversity conservation

Open access to sequence data is a cornerstone of biology and biodiversity research, but has created tension under the United Nations Convention on Biological Diversity (CBD). Policy decisions could compromise research and development, unless a practical multilateral solution is implemented

On the mechanisms governing gas penetration into a tokamak plasma during a massive gas injection

A new 1D radial fluid code, IMAGINE, is used to simulate the penetration of gas into a tokamak plasma during a massive gas injection (MGI). The main result is that the gas is in general strongly braked as it reaches the plasma, due to mechanisms related to charge exchange and (to a smaller extent) recombination. As a result, only a fraction of the gas penetrates into the plasma. Also, a shock wave is created in the gas which propagates away from the plasma, braking and compressing the incoming gas. Simulation results are quantitatively consistent, at least in terms of orders of magnitude, with experimental data for a D 2 MGI into a JET Ohmic plasma. Simulations of MGI into the background plasma surrounding a runaway electron beam show that if the background electron density is too high, the gas may not penetrate, suggesting a possible explanation for the recent results of Reux et al in JET (2015 Nucl. Fusion 55 093013)

Velocity-space sensitivity of the time-of-flight neutron spectrometer at JET

The velocity-space sensitivities of fast-ion diagnostics are often described by so-called weight functions. Recently, we formulated weight functions showing the velocity-space sensitivity of the often dominant beam-target part of neutron energy spectra. These weight functions for neutron emission spectrometry (NES) are independent of the particular NES diagnostic. Here we apply these NES weight functions to the time-of-flight spectrometer TOFOR at JET. By taking the instrumental response function of TOFOR into account, we calculate time-of-flight NES weight functions that enable us to directly determine the velocity-space sensitivity of a given part of a measured time-of-flight spectrum from TOFOR

Measurement of the View the tt production cross-section using eμ events with b-tagged jets in pp collisions at √s = 13 TeV with the ATLAS detector

This paper describes a measurement of the inclusive top quark pair production cross-section (σtt¯) with a data sample of 3.2 fb−1 of proton–proton collisions at a centre-of-mass energy of √s = 13 TeV, collected in 2015 by the ATLAS detector at the LHC. This measurement uses events with an opposite-charge electron–muon pair in the final state. Jets containing b-quarks are tagged using an algorithm based on track impact parameters and reconstructed secondary vertices. The numbers of events with exactly one and exactly two b-tagged jets are counted and used to determine simultaneously σtt¯ and the efficiency to reconstruct and b-tag a jet from a top quark decay, thereby minimising the associated systematic uncertainties. The cross-section is measured to be: σtt¯ = 818 ± 8 (stat) ± 27 (syst) ± 19 (lumi) ± 12 (beam) pb, where the four uncertainties arise from data statistics, experimental and theoretical systematic effects, the integrated luminosity and the LHC beam energy, giving a total relative uncertainty of 4.4%. The result is consistent with theoretical QCD calculations at next-to-next-to-leading order. A fiducial measurement corresponding to the experimental acceptance of the leptons is also presented

Search for TeV-scale gravity signatures in high-mass final states with leptons and jets with the ATLAS detector at sqrt [ s ] = 13TeV

A search for physics beyond the Standard Model, in final states with at least one high transverse momentum charged lepton (electron or muon) and two additional high transverse momentum leptons or jets, is performed using 3.2 fb−1 of proton–proton collision data recorded by the ATLAS detector at the Large Hadron Collider in 2015 at √s = 13 TeV. The upper end of the distribution of the scalar sum of the transverse momenta of leptons and jets is sensitive to the production of high-mass objects. No excess of events beyond Standard Model predictions is observed. Exclusion limits are set for models of microscopic black holes with two to six extra dimensions

Search for dark matter produced in association with a hadronically decaying vector boson in pp collisions at sqrt (s) = 13 TeV with the ATLAS detector

A search is presented for dark matter produced in association with a hadronically decaying W or Z boson using 3.2 fb−1 of pp collisions at View the MathML sources=13 TeV recorded by the ATLAS detector at the Large Hadron Collider. Events with a hadronic jet compatible with a W or Z boson and with large missing transverse momentum are analysed. The data are consistent with the Standard Model predictions and are interpreted in terms of both an effective field theory and a simplified model containing dark matter

Measurement of the cross section for isolated-photon plus jet production in pp collisions at √s=13 TeV using the ATLAS detector

The dynamics of isolated-photon production in association with a jet in proton–proton collisions at a centre-of-mass energy of 13 TeV are studied with the ATLAS detector at the LHC using a dataset with an integrated luminosity of 3.2 fb−1. Photons are required to have transverse energies above 125 GeV. Jets are identified using the anti- algorithm with radius parameter and required to have transverse momenta above 100 GeV. Measurements of isolated-photon plus jet cross sections are presented as functions of the leading-photon transverse energy, the leading-jet transverse momentum, the azimuthal angular separation between the photon and the jet, the photon–jet invariant mass and the scattering angle in the photon–jet centre-of-mass system. Tree-level plus parton-shower predictions from Sherpa and Pythia as well as next-to-leading-order QCD predictions from Jetphox and Sherpa are compared to the measurements