Complexities of chromosome landing in a highly duplicated genome: toward map-based cloning of a gene controlling blackleg resistance in Brassica napus.
The LmR1 locus, which controls seedling resistance to the blackleg fungus Leptosphaeria maculans in the Brassica napus cultivar Shiralee, was positioned on linkage group N7. Fine genetic mapping in a population of 2500 backcross lines identified three molecular markers that cosegregated with LmR1. Additional linkage mapping in a second population colocalized a seedling resistance gene, ClmR1, from the cultivar Cresor to the same genetic interval on N7 as LmR1. Both genes were located in a region that showed extensive inter- and intragenomic duplications as well as intrachromosomal tandem duplications. The tandem duplications seem to have occurred in the Brassica lineage before the divergence of B. rapa and B. oleracea but after the separation of Brassica and Arabidopsis from a common ancestor. Microsynteny was found between the region on N7 carrying the resistance gene and the end of Arabidopsis chromosome 1, interrupted by a single inversion close to the resistance locus. The collinear region in Arabidopsis was assayed for the presence of possible candidate genes for blackleg resistance. These data provided novel insights into the genomic structure and evolution of plant resistance loci and an evaluation of the candidate gene approach using comparative mapping with a model organism.
Mayerhofer
Reinhold
R
Department of Biological Sciences, University of Alberta, G-404 Biological Sciences Building, Edmonton, Alberta T6G 2E9, Canada. rmayerho@ualberta.ca
Wilde
Kris
K
Mayerhofer
Marion
M
Lydiate
Derek
D
Bansal
Vipan K
VK
Good
Allen G
AG
Parkin
Isobel A P
IA
D001203:Ascomycota; D001483:Base Sequence; D015139:Blotting, Southern; D029688:Brassica napus / Q000235:genetics*; D002874:Chromosome Mapping; D032461:Chromosomes, Plant / Q000235:genetics*; D019295:Computational Biology; D003433:Crosses, Genetic; D017931:DNA Primers; D019143:Evolution, Molecular; D018745:Genome, Plant / Q000235:genetics*; D007113:Immunity, Innate / Q000235:genetics*; D008969:Molecular Sequence Data; D010935:Plant Diseases / Q000235:genetics / Q000382:microbiology*; D017422:Sequence Analysis, DNA; D026801:Synteny / Q000235:genetics
D017931:DNA Primers