Tim George

Can indigenous microbes release phosphorus to crops?

An innovative new project aims to select and use indigenous, phosphorus-solubilising fungi and bacteria to increase the yield of crops by reducing phosphorus deficiency in the tropical soils of Cameroon. Isolation and testing of the microbes in the laboratory at SCRI will be followed by trials in Cameroonian fields.

The background - phosphorus in short supply

Photograph of croplands in the dry season (Geoff Squire)Agriculture is the dominant sector in most sub-Saharan countries of Africa. It provides employment for most of the rural population and makes an important contribution to GDP, GNP and foreign exchange. Agricultural productivity is low and the people depending on agriculture are generally poor. Many of the soils are mostly low in fertility (for example, photograph right), particularly in phosphorus (P) and nitrogen, and need to be fertilised for adequate yield.

Clone of Sustainability Research Platform at Balruddery Farm

A new experimental research platform is being established at Balruddery Farm for long-term studies on arable sustainability.Photograph of a poppy field

The overall goal is to test whether or not potential solutions for sustainable agriculture arising from the current RERAD workpackages, actually result in improved arable biodiversity, resilience, crop productivity and yield stability at a commercial, field-scale over at least four rotation cycles (>20 years).

To do this, we will design a sustainable cropping system based on existing research at SCRI that optimises inputs, yield, biodiversity and ecosystem processes. The effect of this ‘sustainable’ system on long-term trends in yield and system health will be tested by comparison with current commercial practice.

Heterologous expression of genes encoding extracellular enzymes to improve access to organic forms of mineral nutrients

While breeding beneficial traits into commercial germplasm and/or managing the agricultural system to maximise the benefit of soil ecology are possible, a more direct route to improve resource capture by plants is to express beneficial genes in crops directly.

In collaboration with Dr Alan Richardson (CSIRO, Australia) we have expressed extracellular phytase genes in plants, in an attempt to improve P acquisition from organic compounds in the soil. Recent experiments have compared plants grown in soils amended with monogastric animal manures (pigs and poultry) which are thought to contain high concentrations of phytate (the substrate of phytase), with those grown in soils amended with low-phytate manure from ruminants (cattle). Plants expressing extracellular phytases had greater P-uptake than untransformed controls when grown in soils amended with high-phytate manures, but had no advantage in soils amended with low-phytate manures.

These results suggest that it may be possible to enhance P-acquisition by crops by increasing rhizosphere phytase activity. Other work done by our group with these plants has also demonstrated that the expression of phytase in plants does not impact on other associated organisms in the system including rhizosphere bacteria, mycorrhizal fungi and aphids.

The role of potato rooting and rhizosphere microorganisms in mineral nutrients acquisition

Potato rooting characteristics to enhance resource capture

Potatoes require large fertiliser inputs and often require irrigation. One way to reduce these inputs is to cultivate genotypes that use resources more efficiently, either because they require less mineral nutrient in their tissues or because they yield with smaller inputs.

These abilities are affected by many factors, but rooting characteristics (such as increased root growth rate, specific root length, and density and length of root hairs) and rhizosphere biochemical processes (such as the exudation of organic acids and enzymes) are of fundamental importance. Understanding the physiological and genetic control of changes in these characteristics as a natural response to limited resource may provide opportunities to improve the acquisition of soil mineral nutrients and water by plants in conventional and organic systems.

Our initial approach has been to assess the ability of potatoes to explore the soil volume, by screening genotypes for rooting characteristics in the field. We have found significant differences in root length between commercial varieties. In future research, this trait might be exploited in breeding programmes for improved resource acquisition.

Improved barley cultivars for better nutrient acquisition

Barley cultivars to cope with nutritional drought

With global environmental change it is essential to ensure resilience of farming systems. In the agricultural landscape of the future, effective use of water and nutrients by crops will be critical to the sustainability of farming systems.

The main objective of this research is to identify barley cultivars which cope with nutritional drought, the reduced availability of nutrients under predicted drier summer conditions. Understanding the interaction between plant responses to water availability and phosphorus deficiency will be crucial. Since many of the physiological responses associated with both stresses are shared, it is imperative that such responses are decoupled to identify the key drivers of relevant phenotypes.

This research employs state-of-the-art techniques to identify genes, transcripts and proteins which control the expression of relevant phenotypes. Applying this understanding to the barley genetic resources exclusive to SCRI will optimise identification of cultivars better able to cope with the future requirements of farmers.

Initial results have demonstrated that while the overriding driver of root proliferation by commercial varieties of barley is water availability there is an additive effect of P-availability. We now need to elucidate whether barley cultivars have genotypic variation in their response to combined water and nutrient limitation.

Rhizosphere Group

The region of the soil surrounding plant roots is the site of active root secretion and microbial activity involved in the cycling of nutrients. In the Rhizosphere Group, we aim to understand the physiology of traits which affect resource capture within the rhizosphere and their genetic control.

There are opportunities to join this research group as a PhD, MSc/MRes or BSc (Hons) student, currently we are offering projects entitled:

Resource Capture

Adequate resources of light, water and mineral nutrients are essential for plants. The Resource Capture Group aims to understand how best to optimise the utilisation of these resources by crops in a changing global environment, by elucidating the genetic control and physiological bases of the traits involved.

We are also interested in how plants compete, as individuals, for these resources and aim to explain this. We have a strong research team that integrates knowledge of plant physiology, particularly of rooting traits, genetics and mathematical modelling. The group is actively involved in the SCRI Living Field educational project.

Environment Plant Interactions

Image of the SCRI site looking towards the River TaySCRI's environmental science research spans across disciplines to gain a holistic understanding of how plants respond to and modify environmental processes. Scottish Government commissioned research is gaining an in-depth understanding of the environment in arable farming systems and this is being used to advise on policy development in Scotland. These skills have also been applied to emerging issues relevant to the UK and Europe, including the UK’s Farm Scale Evaluations, international working groups, IPDM-based alternatives to pesicides and EU-wide studies on the ecological impacts of GM plants.

The environment and the ecology of plants and pests are our key research areas, investigated by a strong multidisciplinary team of scientists in entomology, pathology, plant sciences, vegetation ecology, phytochemistry, mathematical modelling and soil sciences. A major area of interest is integrating processes that occur above ground and in the soil. Research conducted on plant interactions with soil has extended from the understanding of sustainable arable systems to ‘green’ engineering solutions for slope stabilisation with vegetation.

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