Dynamics of root microorganisms in closed hydroponic cropping systems

Greenhouse production of vegetables in closed hydroponic cropping systems is a resource-efficient technique for the production of high-quality produce with a high yield per unit area. While this type of cropping system allows savings in terms of water and nutrient use, the recirculation of water increases the risk of pathogen dispersal. Oomycetous pathogens in particular, such as Pythium, thrive in aquatic environments and are among the most destructive pathogens. Root pathogen outbreaks could be controlled by sustaining a stable and high level of general microbiota. It is therefore of utmost importance to understand how biotic and abiotic factors affect the indigenous root-associated microbiota. In the present thesis, the impact of pathogen inoculation, plant age, nutrient availability and use of plant protection products on microbial communities associated with root and nutrient solution was investigated. It was demonstrated that all these factors had an effect on the indigenous microorganisms. Plant age in particular was a significant driver of microbial community structure due to its significant impact on root exudation patterns. Using 454-pyrosequencing, the effect on bacterial communities of the inoculation of P. ultimum was visualized. Although the effect was strongest at the fruit-bearing plant stage, clear differences were seen also in the seedling and flowering stages. Nutrient availability was revealed to have an impact on the number of colony-forming units of bacteria, fungi and fluorescent pseudomonads. Organic carbon specifically was shown to be the main driving force of microbial growth. However, not only the quantity, but also the quality and ratios between the different organic and inorganic nutrients had an effect on microbial numbers. Through DGGE analysis, a shift in the bacterial community structure was seen after the addition of a fungicide in the nutrient solution. The microorganisms present in the nutrient solution were not able to degrade the fungicide. This thesis also demonstrates the importance of combining culture-dependent and culture-independent methods in the analysis of microbial communities

Commercial wash of leafy vegetables do not significantly decrease bacterial load but leads to shifts in bacterial species composition

Production of leafy vegetables for the “Ready-to-eat”-market has vastly increased the last 20 years, and consumption of these minimally processed vegetables has led to outbreaks of food-borne diseases. Contamination of leafy vegetables can occur throughout the production chain, and therefore washing of the produce has become a standard in commercial processing. This study explores the bacterial communities of spinach (Spinacia oleracea) and rocket (Diplotaxis tenuifolia) in a commercial setting in order to identify potential contamination events, and to investigate effects on bacterial load by commercial processing. Samples were taken in field, after washing of the produce and at the end of shelf-life. This study found that the bacterial community composition and diversity changed significantly from the first harvest to the end of shelf-life, where the core microbiome from the first to the last sampling constituted <2% of all OTUs. While washing of the produce had no reducing effect on bacterial load compared to unwashed, washing led to a change in species composition. As the leaves entered the cold chain after harvest, a rise was seen in the relative abundance of spoilage bacteria. E. coli was detected after the washing indicating issues of cross-contamination in the wash water

Comparison of two commercial recirculated aquacultural systems and their microbial potential in plant disease suppression

Background: Aquaponics are food production systems advocated for food security and health. Their sustainability from a nutritional and plant health perspective is, however, a significant challenge. Recirculated aquaculture systems (RAS) form a major part of aquaponic systems, but knowledge about their microbial potential to benefit plant growth and plant health is limited. The current study tested if the diversity and function of microbial communities in two commercial RAS were specific to the fish species used (Tilapia or Clarias) and sampling site (fish tanks and wastewaters), and whether they confer benefits to plants and have in vitro antagonistic potential towards plant pathogens. Results: Microbial diversity and composition was found to be dependent on fish species and sample site. The Tilapia RAS hosted higher bacterial diversity than the Clarias RAS; but the later hosted higher fungal diversity. Both Tilapia and Clarias RAS hosted bacterial and fungal communities that promoted plant growth, inhibited plant pathogens and encouraged biodegradation. The production of extracellular enzymes, related to nutrient availability and pathogen control, by bacterial strains isolated from the Tilapia and Clarias systems, makes them a promising tool in aquaponics and in their system design. Conclusions: This study explored the microbial diversity and potential of the commercial RAS with either Tilapia or Clarias as a tool to benefit the aquaponic system with respect to plant growth promotion and control of plant diseases

Nulägesanalys trädgård

Rapporten Nulägesanalys - trädgård har genomförts inom ramen för projektgruppen Insatsstyrka trädgård. Syftet med inventeringen har varit att ge svar på vem som jobbar med trädgårdsvetenskap, vilka forskargrupper och med vilka forskningsämnen, samt identifiera framtida arbetsfält inom ämnet trädgårdsvetenskap och därmed ge uppslag för framtida utveckling av forskningsfält, utbildning och samverkan. I detta ingår att kartlägga trädgårdsvetenskaplig forskning, utbildning och samverkan vid SLU. Nulägesanalysen förväntas därmed ge en grund för fortsatt strategiskt arbete med att utveckla ämnet trädgårdsvetenskap (Horticultural Science) utifrån inventerade resurser och förutsättningar

Психологическое влияние рекламы на потребителей славянских государств

Материалы IX Междунар. науч. конф. студентов, аспирантов и молодых ученых, Гомель, 19-20 мая и 7 июня 2016 г

Scenarier för växtföljd i ekologisk växthusproduktion

With the new EU legislation 2018/848 that entered into force on January 1, 2022, the exemption for cultivation in confined beds in organic production in greenhouses and tunnels disappeared. All production must take place in natural soil , where the soil is in contact with the subsoil. The conversion applies to all cultivation in confined beds, but those who were certified as organic before 28 June 2017 have a deferral of the conversion until 31 December 2031. For all others, the change applies as of 1 January 2022. In addition to the fact that organic production in greenhouses must take place in soil in contact with the bedrock, the new legislation places emphasis on plant diversity and soil fertility. The factsheet displays alternatives for how to proceed with this shift in paradigm

Växtföljder vid ekologisk odling i växthus

In June 2018, the EU decided on a new regulation for organic production (2018/848) that gained force on January 1, 2022. The new regulation demands that also greenhouse production must take place in natural soil that is in contact with the subsoil. In addition there must be a crop rotation containing a legume and a green manure crop. In this two-year-long project funded by the Swedish Board of Agriculture, the consequences of the new legislation were evaluated. We employed three short (one-year) vegetable crop rotations, grown year-round in low-tech polytunnels. The trial was conducted on a field certified for organic production in Scania in 2021-2023. The rotations included cucumber as the main crop, sugar pea as a nitrogen-fixing legume, common rue and Japanese radish as an agroecological service crop and leafy vegetables. The rotations were evaluated in terms of agronomic factors, nutrient dynamics, microbial diversity and activity, as well as disease incidence. We found that a two-year trial period provides indications, but allows only limited long-term conclusions after such a short term of observation. Low-tech cultivation with short crop rotations led to limited yields. Common rue as an agro-ecological service crop is not a suitable crop when grown during autumn. No negative effects by common rue on the next crop were observed in the autumn cultivation. Crop rotation related diseases were not notably present. Soil pH and plant available phosphorus increased over time, as did microbial activity. Microbial activity was influenced by the crop grown, but there were no differences between crop rotations. Alpha-diversity in bacterial and fungal communities was high in all rotations. During the short observation period no differences between the crop rotations could be found (beta-diversity)