Construction of an integrated genetic linkage map for the A genome of Brassica napus using SSR markers derived from sequenced BACs in B. rapa.
BACKGROUND
The Multinational Brassica rapa Genome Sequencing Project (BrGSP) has developed valuable genomic resources, including BAC libraries, BAC-end sequences, genetic and physical maps, and seed BAC sequences for Brassica rapa. An integrated linkage map between the amphidiploid B. napus and diploid B. rapa will facilitate the rapid transfer of these valuable resources from B. rapa to B. napus (Oilseed rape, Canola).


RESULTS
In this study, we identified over 23,000 simple sequence repeats (SSRs) from 536 sequenced BACs. 890 SSR markers (designated as BrGMS) were developed and used for the construction of an integrated linkage map for the A genome in B. rapa and B. napus. Two hundred and nineteen BrGMS markers were integrated to an existing B. napus linkage map (BnaNZDH). Among these mapped BrGMS markers, 168 were only distributed on the A genome linkage groups (LGs), 18 distrubuted both on the A and C genome LGs, and 33 only distributed on the C genome LGs. Most of the A genome LGs in B. napus were collinear with the homoeologous LGs in B. rapa, although minor inversions or rearrangements occurred on A2 and A9. The mapping of these BAC-specific SSR markers enabled assignment of 161 sequenced B. rapa BACs, as well as the associated BAC contigs to the A genome LGs of B. napus.


CONCLUSIONS
The genetic mapping of SSR markers derived from sequenced BACs in B. rapa enabled direct links to be established between the B. napus linkage map and a B. rapa physical map, and thus the assignment of B. rapa BACs and the associated BAC contigs to the B. napus linkage map. This integrated genetic linkage map will facilitate exploitation of the B. rapa annotated genomic resources for gene tagging and map-based cloning in B. napus, and for comparative analysis of the A genome within Brassica species.
National Key Laboratory of Crop Genetic Improvement and National Center of Plant Gene Research (Wuhan), Huazhong Agricultural University, Wuhan 430070, China.
Jinsong
J
Xu
Xiaoju
X
Qian
Xiaofeng
X
Wang
Ruiyuan
R
Li
Xiaomao
X
Cheng
Yuan
Y
Yang
Jie
J
Fu
Shunchang
S
Zhang
Graham J
GJ
King
Jiangsheng
J
Wu
Kede
K
Liu
D001483:Base Sequence; D029688:Brassica napus / Q000235:genetics*; D029741:Brassica rapa / Q000235:genetics*; D002874:Chromosome Mapping / Q000379:methods*; D022202:Chromosomes, Artificial, Bacterial / Q000235:genetics*; D020451:Contig Mapping; D008040:Genetic Linkage; D005819:Genetic Markers; D018745:Genome, Plant / Q000235:genetics*; D018598:Minisatellite Repeats / Q000235:genetics*; D015203:Reproducibility of Results; D012639:Seeds / Q000235:genetics; D017422:Sequence Analysis, DNA
D005819:Genetic Markers