Biology and control of Rhizoctonia solani on rapeseed : A Review

Le Rhizoctonia solani AG2-1 est le principal agent pathogène causant la fonte des semis chez les plantules et les plantes matures (dessèchement prématuré des pieds) sur le colza et le canola (Brassica napus et B. râpa) dans l'Ouest canadien et aux États-Unis; les isolats du groupe AG4 affectent surtout les plantes adultes en causant le rhizoetone commun. L'infection des plantules par AG2-1 est favorisée par les températures fraîches au moment du semis, alors que les températures chaudes survenant tard au cours de la saison de croissance favorisent davantage l'infection des plantes matures par les isolats de AG4. Des données d'enquête montrent que le développement de la maladie est favorisé par une humidité du sol élevée, de bas niveaux d'azote, de phosphore et de potassium, ainsi que par des teneurs élevées en cuivre dans les sols à texture fine. Une résistance modérée chez la moutarde (Sinapis alba) et quelques autres espèces semblables semble être d'origine génétique et elle devrait être utilisée dans des programmes d'amélioration génétique. La carboxine et l'iprodione en mélange avec des insecticides gamma-HCH sont homologués au Canada comme traitements de semence afin de réprimer la fonte des semis et la pourriture racinaire des plantules, mais ce traitement ne réprime pas le dessèchement prématuré des pieds.Rhizoctonia solani AG2-1 is the principal pathogen causing damping-off and seedling and mature plant root rot (brown girdling root rot) in oilseed rape and canola (Brassica napus and B. rapa) in western Canada and the United States; AG4 isolates mainly attack adult plants and cause basai stem rot. Seedling infection by AG2-1 is favoured by cool weather atthe time of planting, whereas warm weather late in the growing season is more conducive for infection of mature plants by AG4 isolates. Survey data show that disease development is favoured by high soil moisture, low levels of nitrogen, phosphorus and potassium and high levels of copper in fine-textured soils. Moderate resistance in condiment mustard (Sinapis alba) and some other species appears to be genetically controlled and should be utilised in breeding programmes. Carboxin and iprodione in mixtures with insecticide gamma-HCH are recommended in Canada as seed treatments to control damping-off and seedling root rot, but do not control brown girdling root rot

Influence of soil moisture, seeding date, and Rhizoctonia solani isolates (AG2-1 and AG4) on disease incidence and yield in canola

Non-Peer Reviewe

Rhizobacterial influence on healthy stand establishment of canola grown in Rhizoctonia solani infested fields of Saskatchewan

Non-Peer ReviewedPre-emergence seedling damping-off, seedling blight, and brown girdling root rot caused by R. solani are important diseases of canola/rape seed in western Canada. Annual yield losses in excess of 20-30% have been reported in several infected fields. Cultural control methods or resistant cultivars are currently unavailable for these diseases. Chemical fungicides have been developed for use to control the disease, but the success rate has been varied. However, the use of chemicals is becoming less acceptable from an environmental point of view. Several studies indicated that biological control using plant growth promoting rhizobacteria may also be effective in controlling R. solani. Field plots were established in Saskatoon, Regina and Melfort, SK, in 1990, 1991 and 1992 to evaluate the potential of rhizobacterial strains as seed treatments to increase the healthy stand of canola CV. Westar grown in R. solani infested field. The bacteria were formulated either in sterile peat or in a liquid carrier and applied to seed just before planting. Bacterized seed were mechanically planted in replicated field plots artificially infested with R. solani. Final healthy stand was measured 30 days after planting. Grain yields were determined by harvesting the plots. Seed bacterization significantly increased the final healthy stand compared to non-bacterized controls. Strains which increased stand showed in vitro antagonistic activity to not only R. solani but also other pathogens such as Pythium ultimum, Fusarium solani and F. oxysporum. Some of these strains induced root elongation of canola under laboratory conditions. Rhizosphere colonization, chemical compatibility and shelf-life of the important bacteria will be discussed

Non-monotonic variation with salt concentration of the second virial coefficient in protein solutions

The osmotic virial coefficient $B_2$ of globular protein solutions is calculated as a function of added salt concentration at fixed pH by computer simulations of the ``primitive model''. The salt and counter-ions as well as a discrete charge pattern on the protein surface are explicitly incorporated. For parameters roughly corresponding to lysozyme, we find that $B_2$ first decreases with added salt concentration up to a threshold concentration, then increases to a maximum, and then decreases again upon further raising the ionic strength. Our studies demonstrate that the existence of a discrete charge pattern on the protein surface profoundly influences the effective interactions and that non-linear Poisson Boltzmann and Derjaguin-Landau-Verwey-Overbeek (DLVO) theory fail for large ionic strength. The observed non-monotonicity of $B_2$ is compared to experiments. Implications for protein crystallization are discussed.Comment: 43 pages, including 17 figure

Large-Eddy Simulations of Magnetohydrodynamic Turbulence in Heliophysics and Astrophysics

We live in an age in which high-performance computing is transforming the way we do science. Previously intractable problems are now becoming accessible by means of increasingly realistic numerical simulations. One of the most enduring and most challenging of these problems is turbulence. Yet, despite these advances, the extreme parameter regimes encountered in space physics and astrophysics (as in atmospheric and oceanic physics) still preclude direct numerical simulation. Numerical models must take a Large Eddy Simulation (LES) approach, explicitly computing only a fraction of the active dynamical scales. The success of such an approach hinges on how well the model can represent the subgrid-scales (SGS) that are not explicitly resolved. In addition to the parameter regime, heliophysical and astrophysical applications must also face an equally daunting challenge: magnetism. The presence of magnetic fields in a turbulent, electrically conducting fluid flow can dramatically alter the coupling between large and small scales, with potentially profound implications for LES/SGS modeling. In this review article, we summarize the state of the art in LES modeling of turbulent magnetohydrodynamic (MHD) ows. After discussing the nature of MHD turbulence and the small-scale processes that give rise to energy dissipation, plasma heating, and magnetic reconnection, we consider how these processes may best be captured within an LES/SGS framework. We then consider several special applications in heliophysics and astrophysics, assessing triumphs, challenges,and future directions

Anemia prevalence in women of reproductive age in low- and middle-income countries between 2000 and 2018

Anemia is a globally widespread condition in women and is associated with reduced economic productivity and increased mortality worldwide. Here we map annual 2000–2018 geospatial estimates of anemia prevalence in women of reproductive age (15–49 years) across 82 low- and middle-income countries (LMICs), stratify anemia by severity and aggregate results to policy-relevant administrative and national levels. Additionally, we provide subnational disparity analyses to provide a comprehensive overview of anemia prevalence inequalities within these countries and predict progress toward the World Health Organization’s Global Nutrition Target (WHO GNT) to reduce anemia by half by 2030. Our results demonstrate widespread moderate improvements in overall anemia prevalence but identify only three LMICs with a high probability of achieving the WHO GNT by 2030 at a national scale, and no LMIC is expected to achieve the target in all their subnational administrative units. Our maps show where large within-country disparities occur, as well as areas likely to fall short of the WHO GNT, offering precision public health tools so that adequate resource allocation and subsequent interventions can be targeted to the most vulnerable populations.Peer reviewe