Environmental Plant Interactions

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:

Agroecology News Archive

Ecological roles of weeds In an invited plenary talk, Geoff Squire represented the group's ideas on the roles of weeds at the XIII Colloque International sur la Biologie des Mauvaises Herbes held at Dijon, France 8-10 September 2009. The main points of the talk were: weeds have been with us in northern Europe for more than 5000 years - we haven't got rid of them; so we need to understand them better, spend less trying to remove them and make use of their positive roles in the ecosystem. Arable cropping in Scotland is already some way towards coexisting with weeds: its cereal yields and weed seedbanks are both among the highest in the UK!  (Added 14 September 2009)

Publications archive

Refereed publications and major reports from the Agroecology group

Newton, A.C., Begg, G.S., Swanston, J.S. 2008. Deployment of diversity for enhanced crop function. Annals of Applied Biology (doi:10.1111/j.1744-7348.2008.00303.x).

Monocultures are used in high-input systems to maximise short term profitability, but over time yield and quality can become unstable. This paper considers how diversity can be reintroduced to cropping systems to confer stability without compromising quality. It combines expertise between three of SCRI's programmes: Pathology (ACN), Genetics (JSS) and Environment (GSB).

Squire, G.R., Hawes, C., Begg, G.S., Young, M.W. 2009. Cumulative impact of GM herbicide-tolerant cropping on arable plants assessed through species-based and functional taxonomies. Environmental Science and Pollution Research 16(1), 85-94. Published online 2 December 2008 (doi: 10.1007/s11356-008-0072-6).

Co-existence with GM crops in European Agriculture

SIGMEA logoThe EU project SIGMEA is examining the feasibility of growing GM and other crops together in the agricultural landscapes of Europe. A central part of the project - Workpackage 2 or WP2 - collates and analyses experimental studies on geneflow by seed and pollen, but also considers field experiments on the ecological impacts of GM cropping. WP2 has over 20 partners who are sharing and analysing definitive data on over 100 field experiments, making the SIGMEA database the most comprehensive of its type. The agroecology group at SCRI co-ordinates this unique synthesis of biology and agronomy. Contact: Geoff Squire

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