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

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Brassica napus, a major world-wide crop, comprises a range of crop types including oilseed rape (OSR), grown for edible and industrial oil, biodiesel, protein for animal feed as well as leaf and root vegetables. Diseases are a major factor limiting production, a threat increasing due to climate change and the imminent withdrawal of agrochemicals in Europe. Improved disease control is an urgent priority and breeders are increasingly using quantitative disease resistance (QDR), which is considered broad-spectrum and durable.This research will identify the most useful QDR genes for OSR breeding and understand the mechanisms behind this to enable predictions of their effectiveness and durability. Our consortium combines the leading expertise on the major OSR pathogens, the latest research on defence mechanisms of resistance and expertise in association genetics to identify effective QDR genes. Our industrial partner, KWS, will provide expertise on deployment of QDR in the field and on the development of genetic markers for molecular breeding of improved OSR varieties.We will identify resistance to the most important pathogens of OSR: Sclerotinia sclerotiorum, Verticillium spp, Leptosphaeria maculans, Alternaria brassicicola, Pyrenopeziza brassicae, and the model pathogens Pseudomonas syringae and Botrytis cinerea. A panel of 192 diverse B. napus lines will be screened for resistance against these pathogens in controlled environments and at KWS field trial sites. Schools will contribute in a 'citizen science' project and evaluate resistance at locations throughout Europe. In the same lines, we will quantify induced defence responses to conserved pathogen-associated molecular patterns (PAMPs). We will also quantify salicylic acid, lignin, phenylpropanoid, glucosinolate, and indole metabolites that are implicated in resistance mechanisms. Using association transcriptomics, we will identify resistance gene loci against multiple pathogens and understand how this relates to metabolite production and PAMP-triggered immunity.To test hypotheses about their contribution to resistance, we include studies on specific genes. Whilst glucosinolates contribute to resistance they can reduce the quality of seed. GTR1 and GTR2 are transporters in Arabidopsis that control the allocation of glucosinolates to seeds. We will test gtr1 gtr2 mutants for fitness and create gtr TILLING mutants in Brassica rapa (B. napus A genome) to measure the glucosinolate partitioning between leaves and seed. The work could enable development of OSR with high leaf glucosinolate content for resistance, without compromising seed quality. We will introduce tomato receptor Ve1 into B. napus and assess its ability to mediate resistance against Verticillium wilt. This research will lead to more sustainable production of OSR, with higher productivity through lower vulnerability to biotic stress and less reliance on chemical inputs.