14 ERA-CAPS Mechanistic Analysis of Quantitative Disease Resistance in Brassica by Associative Transcriptomics

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Oilseed rape (OSR, Brassica napus) is a major crop worldwide, producing edible oil, biodiesel and protein for animal feed. Diseases are a major factor limiting OSR production and improved control is an urgent priority. Breeders are increasingly using quantitative disease resistance (QDR) which is considered broad-spectrum and durable. This proposal addresses the current gap in our knowledge which is the identification of the most useful QDR for breeding.

The first layer of active defence in plants is based on the perception of pathogen (or microbe) associated molecular patterns (PAMPs/MAMPs) leading to PAMP-triggered immunity (PTI). PAMPs are essential molecules, conserved in entire kingdoms of microbes, and are recognised by pattern recognition receptors (PRRs) in plants. Within ERA-PG (PRR-CROP) we developed methods for studying PTI in Brassica crops.

We will identify gene loci contributing to QDR against the most important pathogens of OSR using the novel method of associative transcriptomics (AT), developed at JIC in B. napus by the Bancroft group. Using a 'B. napus diversity panel' of 192 diverse lines we will quantify resistance to the most important pathogens: Sclerotinia sclerotiorum, Verticillium spp, Leptosphaeria maculans, Alternaria brassicicola, Pyrenopeziza brassicae, Pseudomonas syringae and Botrytis cinerea. We will quantify induced defence responses to PAMPs and measure salicylic acid, lignin, phenylpropanoid, glucosinolate, and indole metabolites that are implicated in resistance mechanisms. Using AT, we will identify resistance gene loci against multiple pathogens and understand how this relates to metabolite production and PAMP-triggered immunity. We will also investigate glucosinolate partitioning between leaves and seed using mutants of GTR1 and GTR2 transporters and introduce tomato receptor Ve1 into B. napus and assess its ability to mediate resistance against Verticillium wilt.

Pathways to Impact: Our impact plan for non-academic users and beneficiaries is designed primarily to target those communities that are either most affected by the disease problems or involved in formulating policy relevant to disease management. Light leaf spot, caused by the fungal pathogen Pyrenopeziza brassicae, and phoma stem canker, caused by Leptosphaeria spp., are damaging diseases on oilseed rape in the UK, causing substantial yield losses. The information gained from the project will help agronomists to make recommendations to growers on choice of cultivars. New knowledge from this project will help breeders avoid breakdown of cultivar resistance. It will also help improve disease resistance rating for the HGCA Recommended List (RL). Results of this project will be communicated to policy-makers to guide forward planning as part of strategies to achieve the government climate change mitigation target for UK agriculture (Food 2030) by reducing greenhouse gas emissions through improved disease control. The project consortium members have a good track record for engaging with all of these communities.

Scientific Impact: Advancing fundamental scientific knowledge. This project will generate fundamental knowledge on ill-defined pathosystems that are of major significance to oilseed rape production in the UK. The genome-enabled technologies are not only expected to ameliorate the impact of light leaf spot and phoma stem canker disease pressure in the UK, but also they will be applicable to closely related disease problems like barley leaf spot caused by Rhynchosporium commune. The techniques developed in this study are expected have a significant impact on UK and international agricultural industries. Results from the project will reach the scientific community, including plant pathologists, agronomists and crop scientists through publications in prestigious peer-reviewed international journals The principal investigators will actively promote the research at international conferences. New findings will also be communicated as topic sheets or posters at agricultural events (e.g. Cereals', field days, road-shows, workshops). Details of the project will be made available through the research pages of consortium members.

Economic Impact: New breeding lines and disease management. UK agriculture will benefit from the scientific knowledge gained through this project. The breeding company involved in the project will develop breeding lines and commercialize cultivars with stronger and more durable resistance. Through participation of industry in the consortium, needs of end-users are better addressed. New knowledge about light leaf spot and phoma stem canker control will be disseminated to the industry primarily through on-farm advisory and knowledge transfer teams and breeder commercial marketing teams, and more widely through inter-linked websites.

Social Impact: Improvement of food security. The proposed study will have a large impact on the treatment of crop diseases due to generation of more resistant breeding lines and cultivars. This will positively affect the UK population but also have implications for the rest of Europe and beyond. Using the results of the project, we will increase the awareness of the problems associated with crop diseases and subsequent food security. This information will be disseminated via press releases into the popular scientific press and through publically accessible websites.

Exploitation and Application. In order to maximise impact, findings need to be translated into practical solutions and placed in the public domain as quickly as possible. The communication and engagement mechanisms described have been developed specifically for this purpose. The involvement of a wide range of partners (scientists, breeders, advisors) will ensure that results are exploited directly in the arable sector of the agricultural industry during the course of the project.