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Brassica : Harvesting the Genome, Diversity and Products

1. Overview and challenges

Brassica species play an important role in global agriculture and horticulture, as well as being the closest crop relatives to Arabidopsis. The species are characterised by a wide range of adaptations that have been domesticated into crops including oilseed rape/Canola and swede (B. napus); cabbage, cauliflower, broccoli, Brussels sprout (B. oleracea); turnip, chinese cabbage and pak choi (B. rapa) and mustards (B. nigra, B. juncea, B. carinata).

Brassica crops contribute both to the economies and health of populations (e.g. via anti-oxidants, vitamins, anti-carcinogenic compounds, etc.) around the world. Crop improvement is a key route to ensuring continued benefits arise from these foods and plant products. Brassica is typical of many crop species in having a larger and more complex genome than the model. The genomic relationships are well characterised, as shown in the 'triangle of U', and these have been exploited to understand the basis of chromosome evolution since divergence from a common progenitor shared with Arabidopsis. The Brassica genomes are particularly 'plastic', with several crop morphotypes within each species. This is the analogous to the situation with dogs, where the diverse morphotypes provide ideal material to study man-directed evolution (artificial selection) and the processes involved in domestication.

A wide range of genetic and genomic resources are available from Brassica, as well as the easy access to information derived from Arabidopsis. Reference linkage maps, a wide range of QTL relevant to basic processes and crop phenotypes and sequence-based information are all available. In addition, there is increasing emphasis on characterising and utilising the diverse allelic variation present in genetic resource collections.  

Considerable progress has been made in the genetic analysis of agronomic and related plant traits in Brassica. Many of these have a complex quantitative inheritance which is exacerbated by interactions between genes, plant development and the environment.  Despite the advantages of using information from Arabidopsis, the current challenge remains the need to identify key genes and understand their regulation in crop plants. There is a pressing requirement to resolve recently identified functional loci (major genes and QTLs) in terms of locus-specific copies of candidate or novel genes located in the context of physical map contigs and the emerging complete genome sequence.

1.1.

The Challenges include:

Understanding, conserving, accessing and harnessing genetic diversity

Developing an information-led approach to crop improvement, with associated cost and efficiency benefits

Identifying traits - adapting to changing climate, markets, land use and energy requirements

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Increasing marketable yields  and harvest index

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Improved sustainable production, including pest and disease control, nutrient and water use efficiency

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Diversity of products affecting human health and wealth

Understanding the genome: intra and inter-genomic polyploidy

Navigating the genome - from traits to sequence and vice versa

Identifying genetic components of variation

Global Integration of information and resources in public domain.

- "Global information, local implementation"

1.2.

Managing Complexity: Crop Improvement for Yield, Quality, Sustainability and   Adaptation to climate change

Higher Plants are complex adaptive systems with overlapping and interacting mechanisms for modulating their own development in response to environmental cues.

Draft White Paper for Multinational Brassica Genome Project (MBGP);   12/01/2006

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