title: Genetic linkage maps for Asian and American lotus constructed using novel SSR markers derived from the genome of sequenced cultivar.
abstract: BACKGROUND
  The genus Nelumbo Adans. comprises two living species, N. nucifera Gaertan. (Asian lotus) and N. lutea Pers. (American lotus). A genetic linkage map is an essential resource for plant genetic studies and crop improvement but has not been generated for Nelumbo. We aimed to develop genomic simple sequence repeat (SSR) markers from the genome sequence and construct two genetic maps for Nelumbo to assist genome assembly and integration of a genetic map with the genome sequence.
  
  
  RESULTS
  A total of 86,089 SSR motifs were identified from the genome sequences. Di- and tri-nucleotide repeat motifs were the most abundant, and accounted for 60.73% and 31.66% of all SSRs, respectively. AG/GA repeats constituted 51.17% of dinucleotide repeat motifs, followed by AT/TA (44.29%). Of 500 SSR primers tested, 386 (77.20%) produced scorable alleles with an average of 2.59 per primer, and 185 (37.00%) showed polymorphism among two parental genotypes, N. nucifera 'Chinese Antique' and N. lutea 'AL1', and six progenies of their F1 population. The normally segregating markers, which comprised 268 newly developed SSRs, 37 previously published SSRs and 53 sequence-related amplified polymorphism markers, were used for genetic map construction. The map for Asian lotus was 365.67 cM with 47 markers distributed in seven linkage groups. The map for American lotus was 524.51 cM, and contained 177 markers distributed in 11 genetic linkage groups. The number of markers per linkage group ranged from three to 34 with an average genetic distance of 3.97 cM between adjacent markers. Moreover, 171 SSR markers contained in linkage groups were anchored to 97 genomic DNA sequence contigs of 'Chinese Antique'. The 97 contigs were merged into 60 scaffolds.
  
  
  CONCLUSIONS
  Genetic mapping of SSR markers derived from sequenced contigs in Nelumbo enabled the associated contigs to be anchored in the linkage map and facilitated assembly of the genome sequences of 'Chinese Antique'. The present study reports the first construction of genetic linkage maps for Nelumbo, which can serve as reference linkage maps to accelerate characterization germplasm, genetic mapping for traits of economic interest, and molecular breeding with marker-assisted selection.
authors.affiliation: Key Laboratory of Aquatic Plant and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, Hubei, 430074, China.
authors.forename: Mei
authors.initials: M
authors.lastname: Yang
authors.forename: Yanni
authors.initials: Y
authors.lastname: Han
authors.forename: Robert
authors.initials: R
authors.lastname: VanBuren
authors.forename: Ray
authors.initials: R
authors.lastname: Ming
authors.forename: Liming
authors.initials: L
authors.lastname: Xu
authors.forename: Yuepeng
authors.initials: Y
authors.lastname: Han
authors.forename: Yanling
authors.initials: Y
authors.lastname: Liu
mesh_terms: D002874:Chromosome Mapping; D018745:Genome, Plant / Q000235:genetics*; D023281:Genomics; D005838:Genotype; D018895:Microsatellite Repeats / Q000235:genetics*; D031653:Nelumbo / Q000235:genetics* / Q000254:growth & development; D011110:Polymorphism, Genetic / Q000235:genetics