Background: Crop breeding has changed the nutritional, mineral and non-nutritional composition of crop plants. Non-nutritionals include metabolites such as polyphenols and these have historically been considered as ‘anti-nutritionals’, reflecting their effect upon animal health when fed as major components in diets. Polyphenols are also implicated in the regulation of soil processes, including functional diversity of soil microbes and soil microfauna, soil carbon storage and mineralisation both in a negative and positive way. There may also be other downstream ecological consequences such as changes in soil structural stability, root growth and plant-microbe interactions, including between crops, pathogens and/or symbionts. Since polyphenols encapsulates a large class of molecules these processes are likely to be (polyphenol) functional type dependent, and thus the quality of polyphenols within varieties of crop plants may be important in these processes. The choice of varieties within crop rotations therefore not only has implications for animal health when plants are used as feed, but also for soil ecological functioning. Thus, it is particularly surprising therefore that legumes, as ecologically important crops, which may be defined as “corner stone” species of sustainable food and feed-systems, are having attributes such as polyphenols bred-out to satisfy mainly the animal-feed industries. In addition, legumes are often included in cover crop/grass ley mixtures which are either directly or indirectly used for animal feed or returned to the soil with the aim of improving soil function, with unknown impacts of polyphenol content. Aims/Objectives: To determine the ecological roles of polyphenolic non-nutritionals of legumes in soil function and assess the potential for end uses of the polyphenols found within a value-chain context to support agricultural diversification. The initial project objectives are: Ob.1, chemical characterisation of the quantity and quality of polyphenols in a range of legume species; Ob.2, functional characterisation of the polyphenols for likely environmental impact in soil and other potential uses of material in the value-chain (e.g. cosmetics/biorefining/active ingredients for food industry). Ob3. Establish environmental/management impact on polyphenol production. Ob4, Ecological function assessment of amendments to soil including effects on soil structure, mineralization rates, and downstream ecological function. The first two objectives will account for the initial 12 to 18 months of the project (see below).
Methods/Approach: A whole systems approach will be used to assess all input to the environment and potential end uses within the value chain. For the initial assessment plant varieties will be selected across a range of introduction years, with reference to the “market” for which they were bred (e.g. high-protein soybean, vs fresh-frozen peas vs micronizing for dry milling, varieties used in cover cropping etc). Material is already available at Hutton. Since breeding has likely not only affected the grain polyphenols, above-ground residues and roots will be characterised. Plants will be grown in randomised blocked design experiments in both field and glasshouse conditions to assess the impact of environment on polyphenol production, composition, and partitioning. Methods for assessing polyphenols in primary material and during the process of mineralisation include fractionation using different solvents and precipitation techniques with analysis of the fractions on liquid chromatography coupled with tandem mass spectrometry. Initial assessment of soil impacts may include image analysis of soil structure and material (multispectral), aggregate stability plus C & N analysis of processed field and glasshouse trial material. Outline plan (12 – 18 months): Literature review to assess knowledge on plant materials, polyphenols and map network of polyphenols environmental action in soil. Assess the phenotype of field- and pot-grown legumes to obtain material (grains (including hulls), shoot residues, roots etc) for assessing polyphenols and potential of materials/waste for biorefining. Trials will be assessed for biomass, soil environment during growth and after harvests (physical structural), and common legume diseases. Grains, above-ground residues, and roots will be harvested for the chemical (Ob.1) and functional-characterisations of the types (Ob.2). Student Intellectual Input: During the first year the student will have gained an understanding of polyphenol profiles for a range of species and will have to select which species/products and value chain will be the most impactful to focus upon in the long term. The student will be required to select and develop functional assays to assess the polyphenol production levels and assess which processing methods are practical using material from contained environment & field trials (Ob.3) and how to assess the impact of polyphenol residues on the soil environments (Ob.4). For Ob.4 the student can use unrefined (i.e. as harvested dry) material, or extracted, isolated and/or concentrated polyphenols from one or other of grain (hulls), residues and/or roots from one or more species/varieties, or processing waste after extraction for value-chain products and investigate the effects on a range of soil functions in consultation with primary and secondary supervisors at each institution. This project has the potential to have both environmental impact and create knowledge for product development.
Desirable candidate: This is a multi -disciplinary project encompassing sustainability, plant biology, agriculture and chemistry, therefore expertise in any of these areas would be desirable. It is however not necessary to have expertise in all areas, but an overall enthusiasm for developing sustainable agricultural systems, an interesting in understanding the environmental impact of new products with an interest in chemistry would be desirable.
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