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Phenotyping for improved traits for drought tolerance

The overall objective of WP2 is to identify drought tolerant genotypes by characterising the phenotypic ‘ideotype’ associated with tolerance to drought. We are using controlled environment treatments to identify deep phenotype associations and investigate a wide range of plant material, including some previously identified potentially drought tolerant genotypes of miscanthus and poplar.  Through collaboration on systems modelling, the research also seeks to identify genotypes that are suitable for lysimeter analysis and testing in the field to support the environmental assessment of new germplasm. The research uses lysimeter and field trials to validate and translate findings from short term phenomics analysis of large populations in controlled environment studies to larger scale studies of selected genotypes.

A custom-built phenotyping platform is being used to impose highly reproducible soil water deficits (by frequent watering of pots to a constant weight to simulate well-watered or drought conditions) at Aberystwyth and Lancaster University.  About 100 miscanthus clones and about 100 poplar clones are being screened including some genotypes.  The range of clones covers those from wet and dry regions and includes some known to characteristics expected to be associated with drought tolerance, such as leaf rolling and stay-green, leaf growth and water use efficiency. An unbiased biomass screen is being used to ensure selected genotypes represent a range of potential drought tolerance mechanisms. Plants are being assessed for total crop biomass accumulation and crop water use efficiency (biomass per unit of water applied) to identify clones that maximises biomass production under low water availability.

The research uses the state-of-the-art phenotyping facility at Aberystwyth to produce multi-dimensional data sets that are interrogated for association with drought responses in miscanthus and poplar. This includes both structured (where traits are known) and unsupervised learning (where analysis is not guided by predictions of physiology or phenotypes). Phenomics analysis includes visible, short wave IR and thermal IR imaging to assess a range of morphometric data including shoot mass, leaf number, shape, angle, leaf colour and senescence. With the Consiglio Nazionale Delle Ricerche, image analysis is used to indicate a detailed physiological state of plants and detect the impacts of water stress.  Drought may effect both crop yield and quality and therefore plant composition will be studied using high-throughput metabolic analysis. Fourier Transformed – Infra-red spectroscopy will be used to assess impacts on components such as lignin whose levels affect the quality of biomass production. If obvious phenotypes cannot be associated with high biomass accumulation under drought stress such genotypes will be crossed with a drought sensitive type to produce a mapping family to test for segregation of the phenotype. The translation of short term phenomics analysis to field grown plants will be tested by establishing field trials of cloned plants with rain shelters.

Complementing the research described above, selected genotypes which we know grow relatively well in drought conditions are being assessed at two contrasting locations: Aberystwyth (miscanthus) and at the University of Bolognia (arundo) and lysimeters.  Lysimeter experiments allow growth that is more representative of field conditions to be examined while retaining precision of treatment and measurement. Lysimeters experiments precisely control the water input availability, using previously identified arundo and miscanthus clones selected for diverse drought tolerance traits.  Combined with meteorological measurements, this allows us to determine how much of the water applied to each vessel evaporates to the atmosphere, how much is taken up by the plants, and how much remains in the soil matrix.   In combination with measurements of stomatal conductance, transpiration and photosynthesis, the research will produce a strong assessment of genotype specific water use efficiency.  Fluorescence and dark respiration will indicate photo-oxidative stress and metabolic cost of different drought tolerance mechanisms.  Samples for gene expression will be taken for sequencing.  Data from these detailed studies of selected clones will be used for modelling drought responses and predicting clone performance through systems modelling.  Leaf carbon isotope and volatiles will be analysed in arundo as the volatiles seem to play a major role in controlling stress resistance and overall growth in this species. The lysimeter studies will complement field studies work on the environmental assessment by defining the sensitivity of physiological processes to controlling variables. The field trials are established by Dr Kai Scharz and by Aberystwyth at two contrasting locations in the UK (poor draining soil) and Germany (free draining soil), with and without irrigation.