title: Microsatellite markers used for genome-wide association mapping of partial resistance toSclerotinia sclerotiorumin a world collection ofBrassica napus.
abstract: The fungal pathogenSclerotinia sclerotiorumcauses stem rot of oilseed rape (Brassica napus) worldwide. In preparation for genome-wide association mapping (GWAM) of sclerotinia resistance inB. napus, 152 accessions from diverse geographical regions were screened with a single Canadian isolate, #321. Plants were inoculated by attaching mycelium plugs to the main stem at full flower. Lesion lengths measured 7, 14 and 21 days after inoculation were used to calculate the area under the disease progress curve (AUDPC). Depth of penetration was noted and used to calculate percent soft and collapsed lesions (% s + c). The two disease traits were highly correlated (r= 0.93). Partially resistant accessions (AUDPC <7 and % s + c <2) were identified primarily from South Korea and Japan with a few from Pakistan, China and Europe. Genotyping of accessions with 84 simple sequence repeat markers provided 690 polymorphic loci for GWAM. The general linear model in TASSEL best fitted the data when adjusted for population structure (STRUCTURE), GLM + Q. After correction for positive false discovery rate, 34 loci were significantly associated with both disease traits of which 21 alleles contributed to resistance, while the remaining enhanced susceptibility. The phenotypic variation explained by the loci ranged from 6 to 25 %. Five loci mapped to published quantitative trait loci conferring sclerotinia resistance in Chinese lines.
authors.affiliation: Agriculture and Agri-Food Canada, 107 Science Place, Saskatoon, SK S7N0X2 Canada ; International Center for Agricultural Research in the Dry Areas (ICARDA), Rabat, Morocco.
authors.forename: Sanjaya
authors.initials: S
authors.lastname: Gyawali
authors.affiliation: Agriculture and Agri-Food Canada, 107 Science Place, Saskatoon, SK S7N0X2 Canada.
authors.forename: Myrtle
authors.initials: M
authors.lastname: Harrington
authors.affiliation: Agriculture and Agri-Food Canada, 107 Science Place, Saskatoon, SK S7N0X2 Canada.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Durkin
authors.affiliation: Agriculture and Agri-Food Canada, 107 Science Place, Saskatoon, SK S7N0X2 Canada.
authors.forename: Kyla
authors.initials: K
authors.lastname: Horner
authors.affiliation: Agriculture and Agri-Food Canada, 107 Science Place, Saskatoon, SK S7N0X2 Canada.
authors.forename: Isobel A P
authors.initials: IA
authors.lastname: Parkin
authors.affiliation: Agriculture and Agri-Food Canada, 107 Science Place, Saskatoon, SK S7N0X2 Canada.
authors.forename: Dwayne D
authors.initials: DD
authors.lastname: Hegedus
authors.affiliation: Agriculture and Agri-Food Canada, 107 Science Place, Saskatoon, SK S7N0X2 Canada.
authors.forename: Diana
authors.initials: D
authors.lastname: Bekkaoui
authors.affiliation: Agriculture and Agri-Food Canada, 107 Science Place, Saskatoon, SK S7N0X2 Canada.
authors.forename: Lone
authors.initials: L
authors.lastname: Buchwaldt
keywords: Brassica napus; Canola; Genome-wide association mapping; Oilseed rape; SSR; Sclerotinia sclerotiorum; Simple sequence repeats; Stem rot