Notes: The barley accession Q21861 possesses resistance to the stem-rust (Puccinia graminis f.sp. tritici), leaf-rust (P. hordei), and powdery-mildew (Blumeria graminis f.sp. hordei) pathogens. An anther-culture-derived doubled-haploid population was produced from F1 plants from a cross of this accession and the susceptible breeding line SM89010 as a means of rapidly and efficiently determining the genetics of multiple disease resistance. The doubled-haploid population segregated 1:1 (resistant:susceptible) for resistance to the stem rust pathotype QCC indicating the involvement of a single resistance gene, rpg4. Two-gene (3:1) and one-gene (1:1) segregation ratios were observed for resistance to the stem-rust pathotype MCC at low (23–25°c) and high (27–29°C) temperature, respectively. These different segregation patterns were due to a pathotype × temperature interaction exhibited by rpg4 and Rpg1. another stem-rust-resistance gene present in Q21861. One-gene and two-gene segregation ratios were observed in reaction to the leaf rust and powdery mildew pathogens. These data demonstrate the utility of doubled haploid populations for determining the genetics of multiple disease resistance in barley.

Notes: The present study was undertaken in order to test the hypothesis that homologous erythrocytes (E) coated in vivo with C3d could modulate the immunoglobulin (Ig) synthesis of human peripheral blood mononuclear cells (PBMC), stimulated with pokeweed mitogen (PWM) in vitro. E from healthy individuals were found to enhance markedly the Ig synthesis of PBMC cultures stimulated with suboptimal doses (0.01 μg/ml) of PWM. E coated in vivo with increasing amounts of C3d (1.4–6.3 times the amounts on normal E), obtained from patients with systemic lupus erythematosus, failed to induce any significant increase in Ig synthesis of PBMC cultures stimulated with suboptimal PWM doses, compared with cultures co-stimulated in parallel with normal E. In contrast, an increase in IgM and IgG synthesis was observed in about 50% of PBMC cultures from different donors when stimulated with PWM in the presence of L- touted with Ohm vivo (from a patient with congenital factor I deficiency), compared with the Ig synthesis in cultures co-stimulated in parallel with normal E. In contrast to the inability of C3d-coated E to modulate B-cell proliferation, the monoclonal anti-CR2 antibody OKB7 was found to be mitogenic for unstimulated peripheral B cells.

Notes: Kinetic effects associated with the electron motion along magnetic field lines in low-beta plasmas are studied. Using the gyrokinetic description of electrons, a kinetic analog of the reduced magnetohydrodynamic equations is derived, and it is shown that in the strongly nonlinear regime they possess localized solutions in the form of dipolar vortices, which can efficiently interact with resonant electrons. In the adiabatic limit, evolution equations are derived for the vortex parameters, describing exchange of the energy, enstrophy, and of the Poynting vector between the vortex and resonant particles. The evolution equations indicate the possibility of excitation of plasma vortices by electron beams.

Notes: The merging of two identical vortices is studied numerically using a spectral code. It is noted that the enstrophy cascade is most active on the distorted vortex boundaries, with a Kolmogorov-like spectrum E(k)≈k−α, α≤4, developed at high wave numbers. The inverse energy cascade is completed when the vortices merge into one of larger size. © 1996 American Institute of Physics.

Notes: A localized stationary dipole solution to the Euler equations with a relationship between the vorticity and streamfunction given as ω=−ψ+ψ3 is presented. By numerical integration of the Euler equations this dipole is shown to be unstable. However, the initially unstable dipole reorganizes itself into a new nonlinear dipole, which is found to be stable. This new structure has a functional relationship given as ω=αψ+βψ3−γψ5. Such dipoles are stable to head-on collisions and they are capable of creating tripolar structures when colliding off axis. The effects of increasing Newtonian viscosity on the nonlinear dipole is studied revealing that even though the nonlinearity is weakening, the dipole does not relax towards a Lamb dipole. © 1995 American Institute of Physics.

Notes: Three field experiments were conducted in lupin in 1997, 1998 and 1999 to study two aspects of selectivity of post-emergence weed harrowing; the ability of the crop to resist soil covering (the initial damage effect), and the ability of the crop to tolerate soil covering (the recovery effect). Each year soil covering curves and crop tolerance curves were established in three early growth stages of lupin. Soil covering curves connected weed control and crop soil cover in weedy plots, and crop tolerance curves connected crop yield and crop soil cover in weed-free plots. The experiments showed that both resistance and tolerance were unaffected by the growth stage of lupin within the range from the cotyledon to the 7–8 leaf growth stages. Tolerance to soil covering was also unaffected by year whereas the ability of the crop to resist soil covering was highly affected by year. Lupin showed high tolerance to soil covering but a rather low ability to resist soil covering. Harrowing at multiple growth stages supported the finding that lupin is fairly tolerant to soil covering. Advantages and disadvantages of using soil covering as a measure of crop damage is discussed. In conclusion, weed harrowing in lupin showed positive prospects because of high tolerance to crop soil cover.

Notes: A modelling procedure for prediction of the optimum intensity of harrowing on crop yield is developed. The models are applicable when harrowing is carried out to control annual weed seedlings at early crop growth stages without assessment of associated crop damage. The opti-mum intensity of harrowing is expressed either as number of harrowings or percentage weed con-trol calculated on weed densities or weed dry matter. To verify the modelling approach field experiments in peas were conducted during 1991. Harrowings at progressive intensities were carried out at different growth stages of peas. The optimum yield responses varied between 0% to 5% corresponding to 0% to 70% weed control in terms of weed dry matter reductions. Significant crop damage was associated with harrowing, and yield increases of 13% to 18% were recorded from herbicide application corresponding to 96% to 100% weed control. Modelisation des rendements apres desherbage mecanique par hersage a des stades precoces en cultures de pois (Pisum sativum L.) Un schéma de modélisaation pour prévoir l'optimum d'intensité de hersage pour le rendement de la culture a été développé. Les modèles sont applicables quand le hersage est conduit pourdétruire les plantules d'adventices annuelles à des stades précoces de la culture sans estimation du dégât à la culture associée. L'intensité optimale de hersage est exprimé soil par le nombre de hersages ou le pourcentage d'adventices détruites calculé sur la densité en adventices ou le poids de matiàre sàche. Pour vérifier l'approche par modélisation, des essais de plein champ sur pois ont été conduits en 1991. Des hersages a des intensités progressives ont été conduits à différents stades des pois. Les optima de gain de rendement ont varié entre 0 et 5% correspondant à des destructions d'adventice de 0 à 70% en terme de réductions de matiére sèche. Des dégâts aux cultures ont été associés au hersage et des augmentations de rendements de 13 à 18% ont été observées après des applications herbicides correspondant à 96–100% d'effica-cité. Ertragsmodelle für die mechanische Unkraut bekämpfung durch Eggen in frühen Entwick-lungsstadien der Erbse (Pisum sativum L.) Es wird ein Modell für die Vorhersage der optimalen Intensität des Eggens auf den Ertrag entwickelt, das angewendet werden kann, wenn das Eggen zur Bekämpfung von annuellen Unkräutern in frühen Entwicklungsstadien eingesetzt wird, ohne dabei Kulturpflanzenschaden zu berücksichtigen. Die optimale Intensität des Eggens wird entweder als Anzahl der Eggen striche als Grad der Unkrautbekämpfung, berechnet aus Unkrautdichten oder Unkraut-trockenmasse, ausgedrückt. Zur Überprüfung des Models wurden 1991 Feldversuche durchge-führt, wobei die Erbsen in verschiedenen Entwicklungsstadien mit zunehmender Inten-sität geeggt wurden. Die Ertragsreaktionvariierte zwischen 0 und 5% entsprechend 0 bis 70% Wirkungsgrad, bestimmt als Abnahtne der Unkrauttrockenmasse. Mit dem Eggen waren signifikante Schaden an der Kulturpflanze verbunden. Bei chemischer Unkrautbekämpfung mit 96 bis 100% Wirkunggrad nahmen die Enräge urn 13 bis 18% zu.

Notes: Selectivity, defined as the ratio between weed control and crop burial in soil as a result of harrowing, has been used to test different implements according to their degree of selective operation. For this purpose a concept considering qualitative and quantitative aspects of selectivity has been proposed. This makes it possible to determine whether differences in selective mode of operation were caused by construction or by application of implements. Analysis of covariance was used to make this separation. Only if implements affected parameters in a model describing the relationship between crop soil cover and weed control were they suggested to operate with different selectivities. Crop soil cover was assessed by visual score as percentage of crop leaf area covered by soil as a result of harrowing. Using this method it was shown that none of the five harrows tested could be separated on the basis of their selective mode of operation. Selectivity was shown to be influenced by day of treatment, composition of the weed flora, site characteristics and degree of weed control. Harrowing at late crop growth stages was more selective than expected. Essai de hersage pour lutter mecaniquement contre les mauvaises herbes annuelles dans les cultures La sélectivité, définie comme le ratio entre la destruction des mauvaises herbes et l'en fouissement de la culture dans le sol après un hersage, a été utilisée pour tester différents matériels en regard de leur degré d'opération sélective. Pour cela, un concept prenant en compte les aspects qualitatifs et quantitatifs de la sélectivité a été proposé. Celui-ci permet de déterminer si les différences de sélectivité viennent de la construction ou de la mise en oeuvre des matériels. Une analyse de covar-iance a été utilisée pour opérer cette séparation. Seulement si les matériels affectaient les paramètres dans un modèle décrivant la relation entre la couverture de la culture par le sol et le deshérbage, il était envisagé d'opérer avec différentes sélectivités. La couverture de la culture par le sol a étéévaluée par une estimation visuelle du pourcentage de surface foliaire recouverte par le sol après un hersage. Par cette méthode il a été montré qu'aucun des 5 hersages testés ne pouvait être séparé sur la base de leur mode d'opération sélective. La sélectivité a été montrée comme étant influencée par le jour de traitement, la composition de la flore adventice, les caractéristiques du site et le taux de desherbage. Un hersage aux stades tardifs de la culture a été plus sélectif que ce que l'on attendait. Wirksamkeit verschiedener Eggen zur mechanischen Bekämpfung einjähriger Unkräuter in landwirtschaftlichen Kulturen Es wurden verschiedene Geräte nach ihrer selektiven Wirksamkeit beurteilt, wobei die Selektivität als Verhältnis zwischen der Bekämpfung der Unkräuter und dem Verschütten der Kulturpflanzen definiert wurde. Hierfür wurde ein Konzept vorgeschlagen, das die qualitativen und quantitativen Aspekte der Selektivität berücksichtigt. Dadurch konnte bestimmt werden, ob Selektivitätsunterschiede durch die Konstruktion oder durch die Anwendung eines Geräts bedingt waren. Die Unterscheidung erfolgte mittels Kovarianz Analyse. Nur wenn Geräte die Parameter eines Modells über die Beziehung zwischen dem Verschütten der Kulturpflanzen und der Unkrautbekämpfung beeinflußten, wurden ver-schiedene Selektivität angenommen. Das Verschutten der Kulturpflanzen wurde als prozentuale Bedeckung der Blattflächen mit Boden bonitiert. Danach ergab sich, daß die 5 getesteten Eggen in ihrer selektiven Wirkung nicht unterschieden werden konnten. Die Selektivitität wurde vom Tag der Behandlung, der Zusammensetzung der Unkrautflora, den Eigenschaften des Standorts und dem Grad der Unkrautbekämpfung beeinflußt. Das Eggen in fortgeschrittenen Entwicklungsstadien der Kulturpflanzen war selektiver als erwartet.

Notes: Two experiments were conducted in 14 spring barley cultivars to investigate if crop tolerance to post-emergence weed harrowing is related to morphological traits that reflect competitiveness. The experiments were carried out in organically grown fields where low weed densities and biomass production were assumed to be without significant influence on crop growth. The experiments showed that different cultivars responded differently to post-emergence weed harrowing in terms of yield reduction. Taller and higher yielding cultivars with high leaf area index (LAI) tended to be less tolerant to post-emergence weed harrowing than shorter and lower yielding cultivars with low LAI. This conclusion, however, is only valid for 13 of 14 cultivars because one very tall cultivar was tolerant to harrowing. Although the tallest and highest yielding cultivars were damaged the most, they remained the highest yielding cultivars after weed harrowing. This study is the first attempt to relate competitiveness of cereal cultivars to tolerance to harrowing, and it is thought provoking that competitiveness and tolerance is found to be counterproductive.