Additive effect of the root-lesion nematode Pratylenchus penetransand the fungus Rhizoctonia solanion potato yield and damage

The significance of nematodes for disease development caused by other soil-borne pathogens has been demonstrated in many crops throughout the world and specifically prevalent are interactions between plant-parasitic nematodes and species of plant pathogenic fungi. Here, the interaction between the fungusRhizoctonia solani(AG2) and the migratory endoparasitic root-lesion nematodePratylenchus penetranswas investigated on potato. The hypotheses were that the combination ofR. solaniandP. penetranswould result in more severe canker lesions, reduced quality of the tubers and lower tuber yield, and we also expected higher nematode levels to render more nematode damage. To test this, potato plants were grown in pots in two replicate experiments and the presence and/or abundance of the two pathogens were controlled. The first three hypotheses were rejected as (1) the tuber yield decreased when the fungus and nematode occurred together but not more than the sum of their separate effects, i.e. additive, (2) there was no effect of presence of nematodes on the incidence of stem canker, and (3) the quality of tubers was actually partly improved as the presence of the nematodes reduced the likelihood of elephant hide on the tubers in one of the experiments. As expected, there were more visible nematode damages with addition of more nematodes, but beyond that the different nematode levels rendered in most cases similar responses. To have knowledge about interactions between pathogens, as the one showed here, is essential for disease control through appropriate management methods

The power of light: Impact on the performance of biocontrol agents under minimal nutrient conditions

BackgroundThe spectral distribution of light (different wavelength) has recently been identified as an important factor in the dynamics and function of leaf-associated microbes. This study investigated the impact of different wavelength on three commercial biocontrol agents (BCA): Bacillus amyloliquefaciens (BA), Pseudomonas chlororaphis (PC), and Streptomyces griseoviridis (SG). MethodsThe impact of light exposure on sole carbon source utilization, biofilm formation, and biosurfactant production by the selected BCA was studied using phenotypic microarray (PM) including 190 sole carbon sources (OmniLog (R), PM panels 1 and 2). The BCA were exposed to five monochromatic light conditions (420, 460, 530, 630, and 660 nm) and darkness during incubation, at an intensity of 50 mu mol m(-2) s(-1). ResultsLight exposure together with specific carbon source increased respiration in all three BCA. Different wavelengths of light influenced sole carbon utilization for the different BCA, with BA and PC showing increased respiration when exposed to wavelengths within the blue spectrum (420 and 460 nm) while respiration of selected carbon sources by SG increased in the presence of red light (630 and 660 nm). Only one carbon source (capric acid) generated biosurfactant production in all three BCA. A combination of specific wavelength of light and sole carbon source increased biofilm formation in all three BCA. BA showed significantly higher biofilm formation when exposed to blue (460 nm) and green (530 nm) light and propagated in D-sucrose, D-fructose, and dulcitol. PC showed higher biofilm formation when exposed to blue light. Biofilm formation by SG increased when exposed to red light (630 nm) and propagated in citraconic acid. ConclusionTo increase attachment and success in BCA introduced into the phyllosphere, a suitable combination of light quality and nutrient conditions could be used

Grain legume-cereal intercropping enhances the use of soil-derived and biologically fixed nitrogen in temperate agroecosystems: a meta-analysis

Grain legumes are known for their benefits to deliver ecosystem services on provisioning of protein-rich food and feed, reducing greenhouse gas emissions through the symbiotic nitrogen fixation function and diversification of cropping systems. Intercropping is an agroecological practice in which two or more crop species are grown simultaneously in the same field, thereby maximizing the use of resources to enhance yields in low input systemsand the resilience of cropping systems. We quantified the effect of grain legume-cereal intercropping on the useof N resources in temperate agroecosystems, focusing on dinitrogen (N2) fixation and soil-derived nitrogenacquisition using a meta-analysis of 29 field-scale studies. We estimated and compared effects of different intercrop compositions (proportion of each species in the intercrops), fertilization rates, crop species, soil properties, and other management practices on the symbiotic N2 fixation and the acquisition of soil-derived nitrogenby the cereals and grain legumes. The proportion of N derived from N2 fixation was on average 14 % (95 % CI =[11, 16]) higher in intercropped grain legumes (76 %) compared to legume sole crops (66 %). On the other hand,intercropping reduced the amount of N2 fixed (kg ha−1) by about 15 %, when N2 fixation in inter- and solecropped legumes was expressed at equivalent density by compensating for the sown legume proportion in intercrops relative to their sole crop sowing rate. The results were mainly influenced by the intercrop composition,legumes species and the method used to quantify N2 fixation. Soil-derived nitrogen acquisition in intercroppedgrain legumes was significantly reduced (−47 %, 95 % CI = [−56, −36]) compared to sole crop legumes,expressed at equivalent density, while the soil N acquired by intercropped cereals was much higher (+61 %, 95% CI = [24, 108]) than in sole crop cereals. Total soil N acquisition (legume + cereal) was significantly higherin intercrops than in legume sole crops (+25 %, 95 % CI = [1, 54]), while there was no significant differencebetween intercrops and cereal sole crops. The meta-analysis confirms and highlights that intercropping consistently stimulates complementary N use between legumes and cereals by increasing N2 fixation by grain legumes and increasing soil N acquisition in cereals. Based on the results of this analysis it would be suggested thatcropping systems diversification via intercropping can be used for simultaneous production of both cereals andgrain legumes, while increasing the use of N-sources and reducing external inputs of N fertilizers, thereby enhancing the sustainability of agriculture

Inflationsprognoser – En jämförelse av en klassisk och en bayesiansk skattning

Denna studie behandlar prognostisering av månadsinflation och utgörs av en jämfö-relse mellan en skattningsmetod som enbart använder data för den specifika situationen – en klassisk metod – och en skattningsmetod som använder både datan och annan kunskap – en bayesiansk metod. Bägge skattningsmetoderna används på en enkel modell för månadsinflation i Sverige, Norge, Eurozonen, Storbritannien, Japan och USA, och jämförelsen sker genom att undersöka skattningarnas prognoskraft. För den bayesianska skattningen används, utöver datan för det aktuella landet, information från ett närliggande land. De bägge skattningsmetoderna genomförs för varje månad under en längre tidsperiod, för varje skattning beräknas prognoser över de nästkommande sex månaderna, och jämförelsen sker genom att beräkna prognosernas kvadratfel. Resultaten pekar på att de klassiska och de bayesianska prognoserna är likvärdiga. Det finns vidare inga tecken på att den bayesianska metoden har särskild fördel vid små datamängder.This paper covers forecasting of monthly inflation and consists of a comparison between an estimation method solely based on data – a classical method – and an estimation method based on that data and other knowledge – a Bayesian method. Both methods are applied to a simple model of monthly inflation in Sweden, Norway, the Euro area, Great Britain, Japan and the US, and the comparison is performed by examining the forecasting results of the two estimations. The Bayesian method is, the current data aside, based on information from a similar country. The estimation results are calculated for each month in an interval covering several years, six month forecasts are calculated from each estimation, and the squared errors of the forecasts are calculated and compared. The study indicates that the estimation methods are equivalent. There are, furthermore, no signs that the Bayesian method performs especially well for small data sets

Residual Spatial Correlation in Two-Way Error Panel Data Models

This thesis examines the spatial autocorrelation in residuals of two-way error panel data models. Three types of models are examined: the standard linear panel data model, the dynamic panel data model, and the spatial lag panel data model. A known theoretical result for the linear model, that the within estimator applied to independent observations results in a spatial correlation in the residuals which is proportional to the inverse of the number of observed individual units, is supported in a Monte Carlo study. Similar Monte Carlo results are shown for the dynamic and spatial models. The Monte Carlo study shows the effect of residual correlation on the maximum likelihood estimation of the spatial model and on residual tests for spatial correlation. Randomization tests for spatial correlation are formulated and their properties are evaluated. The results suggest that a randomization test for local spatial autocorrelation is the most suitable test for samples large in number of individual regions and small in number of time points. The model estimation methods and tests for residual spatial autocorrelation are applied in an empirical examination of regional unemployment in Southern Sweden. The study shows that the spatial lag model is sensitive to choice of spatial weight matrix and indicates the presence of a spatial structure which is not fully captured by the applied models and weight matrices.Denna uppsats behandlar förekomsten av rumslig autokorrelation i residualer till paneldatamodeller med tvåvägsfel. Tre modelltyper undersöks: den linjära paneldatamodellen, en dynamisk paneldatamodell och en spatial paneldatamodell. Ett känt resultat för den linjära modellen, att minsta kvadrat-skattaren tillämpad på oberoende observationer resulterar i en rumslig korrelation i residualserien vars storlek är proportionell till inversen av antalet observerade individer, undersöks i en Monte Carlo-studie. Liknande simuleringsresultat ges för de dynamiska och rumsliga modellerna. Monte Carlo-studien visar effekten av residualkorrelation på maximum likelihood-skattningen av den rumsliga modellen och på hypotestester för rumslig korrelation. Randomiseringstest för rumslig korrelation formuleras och testas. Resultaten pekar mot att ett randomiseringstest för lokal rumslig autokorrelation är det lämpligaste testet för stickprov över ett stort antal regioner och ett lågt antal tidpunkter. De tre typerna av paneldatamodeller skattas i en empirisk undersökning av regional arbetslöshet i södra Sverige (Skåne). Tester för rumslig autokorrelation tillämpas på modellernas residualer. Studien visar att den rumsliga paneldatamodellen är känslig för val av viktmatris och pekar på förekomsten av en rumslig struktur som inte helt fångas av de tillämpade modellerna och viktmatriserna

Judicial Tax Treaty Override by the Swedish Supreme Administrative Court : Analysis of RÅ 2008 not 61

Varje suverän stat bestämmer sin beskattningsrätt, de subjekt och objekt som staten ålägger skatt. Om två skilda staters beskattning träffar samma person och transaktion, uppstår in-ternationell juridisk dubbelbeskattning. Eftersom dubbelbeskattning kan leda till en mycket hög beskattning av en enskild, och därmed verka som ett hinder för internationell handel, ingår stater skatteavtal i vilka rätten att beskatta fördelas mellan staterna. Skatteavtalen skapar därmed en inskränkning av den rätt staten tar sig i den interna lagstiftningen. Sverige har ett 90-tal skatteavtal med olika länder; en majoritet av dessa följer den avtalsmodell som arbetats fram inom OECD. När Sverige ingår ett skatteavtal ska avtalet införlivas med svensk rätt för att bli gällande lag. Det sker genom en särskild inkorporeringslag. I den interna skatterätten finns regler som förhindrar skatteflykt. Ett exempel på sådana regler är CFC-lagstiftning, genom vilken staten utökar sitt skatteanspråk till att omfatta vis-sa utländska bolag som ägs av personer med hemvist i staten. Vid CFC-beskattning beskattas ägaren för den vinst som sker i bolaget. Det har länge pågått en debatt om huruvida CFC-lagstiftning är förenlig med skatteavtalen, och då främst artiklarna 7 (inkomst av rörelse) och 10 (utdelning) i OECD:s modellavtal. Under 2008 avgjorde Regeringsrätten frågan om förenlighet mellan CFC-beskattning och skatteavtalen. I RÅ 2008 not. 61 hade Skatterättsnämnden funnit att det svensk-schweiziska skatteavtalet inte förhindrade den svenska CFC-beskattningen. Nämnden hade tolkat avtalets artiklar och funnit att den svenska beskattningen var möjligt. Regeringsrätten fastställde nämndens beslut, men resonerade på ett annat sätt. Domstolen fann att inkorporeringsla-gen och den interna CFC-lagstiftningen var likställda. Skatteavtalet skulle alltså ej ha ett fö-reträde. Då lika lagar motsäger varandra uppstår en regelkonkurrens. Denna konkurrens kan lösas genom att tillämpa principerna om speciallags respektive senare lags företräde. Regeringsrätten fann att CFC-reglerna ska ha företräde eftersom de tillkommit senare än skatteavtalet och är riktade mot just den situation fallet gällde. Domen blev kritiserad för att den frångår den folkrättsliga förpliktelsen att tillämpa avtalet. I uppsatsen analyseras RÅ 2008 not. 61. Analysen utgår ifrån fyra delsyften: varför och hur tillämpar domstolen regelkonkurrens; finns det en grund för ett företräde för skatteavtal framför intern rätt; utgör domen ett tax treaty override; och vad hade en tolkning av avtalet kunnat ge för resultat? Slutsatsen innefattar kritik av Regeringsrätten dom, särskilt gällande tillämpning av principerna för regelkonkurrens, men ger även visst stöd för domstolens resonemang kring när regelkonkurrens uppstår

Can Cd content in crops be controlled by Se fertilization? A meta-analysis and outline of Cd sequestration mechanisms

Aim: Cadmium mitigation in crops is a worldwide concern. Selenium application has been suggested as a potential solution to reduce cadmium concentration in plants, but published results were contradictory. We analysed literature data with respect to the effect of selenium addition on cadmium uptake and elucidated processes possibly involved. Method: A meta-analysis was performed on data collected from previously published studies presenting cadmium concentration in plants subjected to selenium treatments. Metaregression random models were run to test the impact of different factors. In addition, soil and crop inventory data exemplifying the natural variation of Cd and Se in soil were evaluated. Results: The results highlighted a significant reduction of cadmium concentration in crops after selenium addition. The reduction was dose-dependent for crops growing under aerobic, but not for plants cultivated under anoxic conditions such as rice. This suggests that different process can be involved. Conclusion: We demonstrated the potential of selenium fertilization to mitigate cadmium uptake and highlighted that for non-rice species, the main process seems to take place in the soil, while mechanisms in roots restricting uptake may be involved for all crops. The inventory data also indicated an impact of natural soil Se on Cd contents in crops

Temporal Interactions between Root-Lesion Nematodes and the Fungus Rhizoctonia Solani Lead to Reduced Potato Yield

Soil microorganisms and soil fauna may have a large impact on the tuber yield of potato crops. The interaction between root-lesion nematodes and the pathogenic fungus Rhizoctonia solani Kuhn was studied on potato plants grown in pots under controlled conditions. In two similar experiments, different combinations of nematodes and fungal mycelium were added to the pots at three occasions; at planting, after 14 days, and after 28 days. The nematodes reduced root biomass and the combination of nematodes and R. solani resulted in reduced tuber yield in both experiments, but the interaction was not synergistic. In contrast, the number of stem canker lesions decreased in the presence of nematodes compared to treatments with R. solani only. The time of inoculation influenced the severity of both fungal and nematode damage. The nematode damage on tubers was less severe if the nematodes were added at 28 days, while the number of severe stem canker lesions increased if the fungus was added at 28 days. However, the time of nematode inoculation did not affect the incidence of fungal damage, hence the nematodes did not assist R. solani to infect the plant. Our results highlight the underestimated importance of root-lesion nematodes, not resulting in obvious above ground symptoms or misshaped tubers yet affecting the performance of other pathogens