AUTHOR=Raman Harsh , Raman Rosy , Coombes Neil , Song Jie , Diffey Simon , Kilian Andrzej , Lindbeck Kurt , Barbulescu Denise M. , Batley Jacqueline , Edwards David , Salisbury Phil A. , Marcroft Steve 

TITLE=Genome-wide Association Study Identifies New Loci for Resistance to Leptosphaeria maculans in Canola

JOURNAL=Frontiers in Plant Science

VOLUME=7

YEAR=2016

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2016.01513

DOI=10.3389/fpls.2016.01513

ISSN=1664-462X

ABSTRACT=<p>Key message “We identified both quantitative and quantitative resistance loci to <italic>Leptosphaeria maculans</italic>, a fungal pathogen, causing blackleg disease in canola. Several genome-wide significant associations were detected at known and new loci for blackleg resistance. We further validated statistically significant associations in four genetic mapping populations, demonstrating that GWAS marker loci are indeed associated with resistance to <italic>L. maculans.</italic> One of the novel loci identified for the first time, <italic>Rlm12</italic>, conveys adult plant resistance in canola.” Blackleg, caused by <italic>Leptosphaeria maculans</italic>, is a significant disease which affects the sustainable production of canola (<italic>Brassica napus</italic>). This study reports a genome-wide association study based on 18,804 polymorphic SNPs to identify loci associated with qualitative and quantitative resistance to <italic>L. maculans</italic>. Genomic regions delimited with 694 significant SNP markers, that are associated with resistance evaluated using 12 single spore isolates and pathotypes from four canola stubble were identified. Several significant associations were detected at known disease resistance loci including in the vicinity of recently cloned <italic>Rlm2</italic>/<italic>LepR3</italic> genes, and at new loci on chromosomes A01/C01, A02/C02, A03/C03, A05/C05, A06, A08, and A09. In addition, we validated statistically significant associations on A01, A07, and A10 in four genetic mapping populations, demonstrating that GWAS marker loci are indeed associated with resistance to <italic>L. maculans</italic>. One of the novel loci identified for the first time, <italic>Rlm12</italic>, conveys adult plant resistance and mapped within 13.2 kb from <italic>Arabidopsis R</italic> gene of TIR-NBS class. We showed that resistance loci are located in the vicinity of <italic>R</italic> genes of <italic>Arabidopsis thaliana</italic> and <italic>Brassica napus</italic> on the sequenced genome of <italic>B. napus</italic> cv. Darmor-<italic>bzh</italic>. Significantly associated SNP markers provide a valuable tool to enrich germplasm for favorable alleles in order to improve the level of resistance to <italic>L. maculans</italic> in canola.</p>