Time filter

Source Type

Örebro, Sweden

Anders J.,Precision Agriculture and Pedometrics | Katarzyna M.-S.,Precision Agriculture and Pedometrics | Gunnar B.,Plant Nutrition and Soil Biology | Ann-Charlotte W.,Precision Agriculture and Pedometrics | Ann-Charlotte W.,HS Konsult AB
European Journal of Plant Pathology

Clubroot (Plasmodiophora brassicae) is a serious soil-borne disease in brassica crops world-wide. We report on a time series of soil samples from Swedish long-term fertility trials started in 1957, 1963 and 1966, which were analyzed for the amount of P. brassicae DNA. The crop rotations included a brassica crop every 4 or 6 years. All experimental sites with a 4-year rotation of oilseed rape, except one with calcium carbonate in the soil profile, showed high (>1000 fg DNA g−1 soil) levels of P. brassicae DNA after 9, 11 and 12 rotations. In contrast, detectable levels (>5 fg DNA g−1 soil) of P. brassicae were found only at one of five sites with a 6-year rotation of spring oilseed rape. In years with high levels of P. brassicae DNA, low yield was reported and a subsequent decline in P. brassicae DNA in soil was observed. Different NPK (nitrogen/phosphorus/potassium) fertiliser regimes resulted in similar P. brassicae DNA levels. The robustness and reliability of the method applied was verified by analyses of soil from individual plots compared with a mixture of plots and by repeated analyses of selected samples, which showed that P. brassicae DNA remained stable during dry storage. © 2016 The Author(s) Source

Wallenhammar A.-C.,Swedish University of Agricultural Sciences | Wallenhammar A.-C.,HS Konsult AB | Almquist C.,Swedish University of Agricultural Sciences | Almquist C.,Eurofins | And 2 more authors.
Plant Pathology

A protocol using real-time polymerase chain reaction (PCR) for the direct detection and quantification of Plasmodiophora brassicae in soil samples was developed and used on naturally and artificially infested soil samples containing different concentrations of P. brassicae. Species-specific primers and a TaqMan fluorogenic probe were designed to amplify a small region of P. brassicae ribosomal DNA. Total genomic DNA was extracted and purified from soil samples using commercial kits. The amount of pathogen DNA was quantified using a standard curve generated by including reactions containing different amounts of a plasmid carrying the P. brassicae target sequence. The PCR assay was optimized to give high amplification efficiency and three to four copies of the target DNA sequence were detected. Regression analysis showed that the standard curve was linear over at least six orders of magnitude (R 2>0·99) and that the amplification efficiency was >92%. The detection limit in soil samples corresponded to 500 resting sporesg -1 soil. The intersample reproducibility was similar to, or higher than, that of assays for other pathogens quantified in soil samples. Bait plants were used to validate the real-time PCR assay. The protocol developed was used to investigate the spatial distribution of P. brassicae DNA in different fields and a significant difference was found between in-field sampling points. The reproducibility of soil sampling was evaluated and showed no significant differences for samples with low levels of inoculum, whereas at higher levels differences occurred. Indicator kriging was used for mapping the probability of detecting P. brassicae within a 2-ha area of a field. A threshold level of 5fg plasmid DNAg -1 soil, corresponding to approximately 3×10 3P. brassicae resting sporesg -1 soil, is suggested for growing resistant cultivars. The results provide a robust and reliable technique for predicting the risk of disease development and for assessing the distribution of disease within fields. © 2011 The Authors. Plant Pathology © 2011 BSPP. Source

This study investigated the effects of intercropping organically grown maize and faba bean under Swedish conditions on yield, forage quality, soil mineral nitrogen (N) content after harvest and weed incidence. Experiments with maize and faba bean as a monocrop and intercrop were performed at three field sites, with various amounts of N (dairy slurry) applied. The land equivalent ratio (LER) was 1.10-1.21 in two of the three experiments. The mean crude protein concentration of the three experiments increased from 63gkg-1, in feed of monocropped maize, to 107gkg-1, in feed of maize intercropped with faba bean. Intercropping had lower N balances compared with monocropped maize and tended to reduce the content of mineral N in the soil after harvest by, on average, 10kgha-1. Weed incidence was slightly reduced by intercropping compared with monocropped maize. In conclusion, the results show that intercropping maize and faba bean in organic production can generate positive yield effects with LER>1. Furthermore, intercropping resulted in higher protein content and lower residual soil mineral N after harvest compared to monocropped maize. Intercropping can thus increase the sustainability of forage production by reducing the need for protein feed and the risk of N pollution. The positive effects of intercropping, i.e. increased yield and reduced soil residual N, were found in the fields with relatively high amount of available N, but not in a field with lower N availability. © 2014 Elsevier B.V. Source

Javed M.T.,University of Stockholm | Stoltz E.,HS Konsult AB | Lindberg S.,University of Stockholm | Greger M.,Hedmark University College
Environmental Science and Pollution Research

The presence of Eriophorum angustifolium in mine tailings of pyrite maintains a neutral pH, despite weathering, thus lowering the release of toxic elements into acid mine drainage water. We investigated if the presence of slightly elevated levels of free toxic elements triggers the plant rhizosphere to change the pH towards neutral by increasing organic acid contents. Plants were treated with a combination of As, Pb, Cu, Cd, and Zn at different concentrations in nutrient medium and in soil in a rhizobox-like system for 48-120 h. The pH and organic acids were detected in the mucilage dissolved from root surface, reflecting the rhizospheric solution. Also the pH of root-cell apoplasm was investigated. Both apoplasmic and mucilage pH increased and the concentrations of organic acids enhanced in the mucilage with slightly elevated levels of toxic elements. When organic acids concentration was high, also the pH was high. Thus, efflux of organic acids from the roots of E. angustifolium may induce rhizosphere basification. © 2012 Springer-Verlag Berlin Heidelberg. Source

Almquist C.,Eurofins | Almquist C.,Swedish University of Agricultural Sciences | Wallenhammar A.-C.,Swedish University of Agricultural Sciences | Wallenhammar A.-C.,HS Konsult AB
Plant Pathology

Sclerotinia stem rot of spring oilseed rape (Brassica napus) is caused by Sclerotinia sclerotiorum. In Sweden, the disease leads to severe crop damage that varies from year to year. A real-time PCR assay was developed and used to determine the incidence of S. sclerotiorum DNA on petals and leaves of spring oilseed rape as well as in air samples, with the aim of finding tools to improve precision in disease risk assessment. Five field experiments were conducted from 2008 to 2010 to detect and study pathogen development. Assessments of stem rot showed significant differences between experimental sites. The real-time PCR assay proved fast and sensitive and the relationship between percentage of infected petals determined using a conventional agar test and the PCR assay was linear (R2> 0·76). There were significant differences in S. sclerotiorum incidence at different stages of flowering. The incidence of S. sclerotiorum DNA on the leaves varied (0-100%), with significantly higher incidence on leaves at lower levels. In one field experiment, S. sclerotiorum DNA was not detected on petals during flowering, whereas the pathogen was detected on leaves, with a corresponding stem rot incidence of 7%. The amount of S. sclerotiorum DNA in sampled air revealed that spore release did not coincide with flowering on that experimental site. Thus, using a real-time PCR assay to determine the incidence of S. sclerotiorum on oilseed rape leaves, rather than on petals, could potentially improve disease risk assessment. © 2014 British Society for Plant Pathology. Source

Discover hidden collaborations