Identification and Characterisation of Candidate Genes in Brassica napus Conferring Resistance to Blackleg Disease

In order to meet the increasing demands on agriculture by a growing global population, it is essential that we develop a comprehensive understanding of the factors that contribute to yield limitation and crop destruction. One key area is the relationship between plant and pathogen. The identification of genes underlying important quantitative trait loci (QTL) is extremely challenging in complex genomes such as Brassica napus (canola/oilseed rape).  However, recent advances in next generation sequencing (NGS) enable much quicker identification of candidate genes.

Here we demonstrate this with the identification of candidate disease resistance genes from Brassica napus for its most devastating fungal pathogen, Leptosphaeria maculans, the causal agent of blackleg disease. Resistance to the disease can be either quantitative or qualitative, in which seedling derived qualitative resistance is conferred by the recognition of an effector molecule by the product/s of a R gene. Qualitative resistance typically results in complete resistance against this pathogen. Candidate CC-NBS-LRR and TIR-NBS-LRR genes, implicated in disease response were identified through analysis of the B. napus genome sequence.Several of these genes were clustered around a region syntenic with major loci for blackleg resistance in B. napus.

By combining phenotypic data with next generation sequencing data, allelic variation within identified candidate genes, between cultivars with known R gene compositions, can be associated with the trait of interest. Molecular analyses of candidate genes using NGS, Long-range PCR (LR-PCR) and high throughput SNP genotyping in diverse cultivars, along with initial validation, will be presented.