Crop Diversity

Introduction

Several studies within the 2016-2021 Strategic Research Programme (SRP) are aimed at understanding the role of biodiversity in regulating the functions of crop production systems. This includes the impacts of diversity within a species (i.e. genetic diversity) and the diversity of species within a crop system on ecosystem functions such as crop production or resilience, or other trophic levels within a system (for example pests or diseases, or soil communities).  Our current work builds on studies from the previous SRP and other projects in a number of thematic areas.

• Biodiversity-function relationships
• Crop-rare plant interactions
• Safeguarding the genetic diversity of barley
• Related projects
• Publications

Biodiversity-function relationships

An important area of research is in understanding the relationship between the biodiversity within an ecosystem and the way in which that ecosystem functions in terms of (for example) producing food (including the amount of food produced, or the resilience of food production), regulating pests and diseases, or efficiently using available nutrients. We use a range of approaches to explore this issue in more detail, all of them focussing on crop production systems as our experimental model.

Greenhouse studies using artificial barley and arable weed communities indicate that both weed species diversity and barley genotype diversity positively impacted on overall productivity. However, the effects of weed species diversity were much greater. This is probably because the relationship between diversity and functions is strongly regulated by plant traits. Traits are the characteristics of plants such as their growth form, size, resource capture and reproductive mechanisms; in our studies there was more variability in traits between weed species than between barley genotypes, thus enabling weed species diversity to have a greater effect. However the positive effect of barley genotype diversity on productivity was due to genuine complementarity. This means that the individuals within the more diverse crop fitted together “better”, demonstrating that crop genetic diversity can have positive effects on ecosystem functions such as productivity. For more information see Schöb et al. (2015) and Pakeman et al. (2015)

Under the 2016-2021 Strategic Research Program we have extended this work with large-scale field trials to examine diversity-function effects in barley-weed systems. We are currently analysing the results of these new experiments to assess whether similar processes of complementarity are taking place. Initial analyses - presented at the 2016 British Ecological Society Annual Meeting in Liverpool, the poster based on these analyses is available as download - indicate a positive relationship between weed diversity and barley production, and we are exploring this in more detail to identify the underlying mechanisms. The scientific findings from this research have been communicated to stakeholder organisations at a workshop (view the workshop report here), where stakeholder input was gathered to guide further research.

Crop – rare plant interactions

As well as looking at interactions between biodiversity and common arable weeds, we have explored the relationship between crops and survival of rare plants which were once common weeds of arable systems. For a range of reasons, many linked to modern farming practice, these species have now become very rare, and we have tried to understand how biodiversity in crop systems might play a part in their future conservation.

Our greenhouse studies have shown that the diversity of common weeds has strong and negative impacts on the establishment of new weed species in experimental plant communities, in particular on the establishment of rare arable weed species, indicating that these rare species might be inferior competitors compared to common species. For more information see Schöb et al. (2017)

Field trials have shown that one rare weed species, Valerianella rimosa, germinated better when in the presence of a barley crop compared to plots where barley was absent, suggesting that crops might provide the conditions which these rare plants need to establish. We have been following this up with further field trials to examine the response to crops of a wider range of rare plants of arable systems.

Safe-guarding the genetic diversity of barley

By 2020, the genetic diversity of cultivated plants and farmed and domesticated animals and of wild relatives, including other socio-economically as well as culturally valuable species, is maintained, and strategies have been developed and implemented for minimizing genetic erosion and safeguarding their genetic diversity. – CBD Aichi Biodiversity Target 13

The research focuses on a collection of old barley cultivars and landraces from the UK, relevant to Aichi goal 13 ‘to maintain and develop strategies for safeguarding the genetic diversity of cultivated plants’.

Maintenance

More than 400,000 accessions of barley are found in gene banks globally and a significant proportion of these are landraces that are presumed to be already adapted to a wide range of environments. The UK has a rich heritage in barley cultivation and we have sourced a collection of locally adapted ‘heritage’ accessions from the UK and Scandinavia, most of which have been grown for hundreds of years, surviving both changes in climate and agricultural practise.  This collection has been multiplied, genotyped and stored as part of the barley underpinning research, along with geo-referenced landraces and wild relatives sourced from genebanks representing the eco-geographic range of barley (WP 2.1.1 & 2.1.2).

Developing strategies for safeguarding their genetic diversity

We believe that the most appropriate strategy to safeguard this important and novel source of diversity is to use these in contemporary breeding, to develop varieties that maintain, at the least, current yields whilst placing production on a more sustainable and resilient footing. In nature the most important means of maintaining variation to change is by reproduction. Taking this approach, crossing high yielding cultivars with a series of landraces and wild barleys as donors of novel variation, we can start to realise the potential of this untapped genetic resource. Working with a breeding company as part of a European funded project (WHEALBI: Wheat and barley legacy for breeding improvement) we have started to put this into practice using a targeted gene approach to more efficiently transfer new genetic variation into mainstream breeding. This strategy emphasises the importance of connecting landrace collections to state-of-the-art barley genomics tools, including the sequenced genome and gene based marker arrays with variation detected at almost every gene, and to phenotyping. Ultimately we want to manipulate breeding approaches to provide resources for our future needs.

Related projects

DIVERSify: Designing InnoVative plant teams for Ecosystem Resilience and agricultural Sustainability:  Work from the Strategic Research Programme has helped to underpin the development of the new DIVERSify project, which aims to optimise the performance of crop species mixtures (‘plant teams’) as a means to improve yield stability, reduce pest and disease damage, and enhance stress resilience in agricultural systems. A particular focus is on the synergies between cereal and legume species. More information on the DIVERSify project can be found here.

Cereal-legume plant teams are also being developed in the RESAS Research Deliverable 2.1.8 “Novel Crops” where winter species combinations are being developed for biomass end use in silage for feed or anaerobic digestion. Here the focus is on quality (digestibility) and optimisation of the nitrogen-fixing component exploitation in the crop and subsequent crops.

Cereal mixtures can play a role as part of an Integrated Pest Management strategy. More on the James Hutton Institute’s work on IPM can be found here.

Publications

The following is a selection of recent publications on the topics of crop diversity, crop mixtures, and their possible use for developing sustainable farming systems.

• Brooker, R.W., Hewison, R., Mitchell, C., Newton, A.C., Pakeman, R.J., Schöb, C., Karley, A. 2018. The role of crop genetic diversity in determining plant community resilience to experimental drought. Poster presentation to BES Annual Meeting, Birmingham, December 2018.
• Schoeb, C.; Hortal, S.; Karley, A.J.; Morcillo, L.; Newton, A.C.; Pakeman, R.J.; Powell, J.R.; Anderson I.C.; Brooker, R.W. (2017) Species but not genotype diversity strongly impacts the establishment of rare colonisers. Functional Ecology.
• Brooker, R.W. (2016) Nature’s role in feeding the 10 billion: how biodiversity can benefit agriculture. In: Gordon, I.J., Prins, H.H.T. & Squire, G.R. (ed.). Food Production and Nature Conservation: Conflicts and Solutions. Routledge, London, Chapter 12, pp238-257
• Brooker, R.W., Karley, A.J., Newton, A.C., Pakeman, R.J. & Schob, C. (2016) Facilitation and sustainable agriculture: a mechanistic approach to reconciling crop production and conservation. Functional Ecology, 30, 98-107.
• Newton AC, 2016. Exploitation of diversity within crops – the key to disease tolerance? Frontiers in Plant Science 7:665. doi: 10.3389/fpls.2016.00665.
• Brooker, R.W., Bennett, A.E., Cong, W.-F., Daniell, T.J., George, T.S., Hallett, P.D., Hawes, C., Iannetta, P.P.M., Jones, H.G., Karley, A.J., Li, L., McKenzie, B.M., Pakeman, R.J., Paterson, E., Schoeb, C., Shen, J., Squire, G., Watson, C.A., Zhang, C., Zhang, F., Zhang, J. & White, P.J. (2015) Improving intercropping: a synthesis of research in agronomy, plant physiology and ecology. New Phytologist, 206, 107-117.
• Pakeman, R.J., Karley, A.J., Newton, A.C., Morcillo, L., Brooker, R.W. & Schoeb, C. (2015) A trait-based approach to crop-weed interactions. European Journal of Agronomy, 70, 22-32.
• Schoeb, C., Kerle, S., Karley, A.J., Morcillo, L., Pakeman, R.J., Newton, A.C. & Brooker, R.W. (2015) Intraspecific genetic diversity and composition modify species-level diversity-productivity relationships. New Phytologist, 205, 720-730.
• Russell, J.; Mascher, M.; Dawson, I.K.; Kyriakidis, S.; Calixto, C.; Freund, F.; Bayer, M.; Milne, I.; Marshall-Griffiths, T.; Heinen, S.; Hofstad, A.; Sharma, R.; Himmelbach, A.; Knauft, M.; van Zonneveld, M.; Brown, J.W.S.; Schmid, K.; Kilian, B.; Muehlbauer, G.J.; Stein, N.; Waugh R. Adaptation of barley to different environments revealed in the exomes of a rangewide collection of landraces and wild relatives. Nature Genetics, 48, 1024-1030.
• Dawson, I.K.; Russell, J.; Powell, W.; Steffenson, B.; Thomas, W.T.B.; Waugh, R. (2015) Barley: a translational model for adaptation to climate change. New Phytologist, 206, 913-931.