title: A high-density genetic map for anchoring genome sequences and identifying QTLs associated with dwarf vine in pumpkin (Cucurbita maxima Duch.).
abstract: BACKGROUND
  Pumpkin (Cucurbita maxima Duch.) is an economically important crop belonging to the Cucurbitaceae family. However, very few genomic and genetic resources are available for this species. As part of our ongoing efforts to sequence the pumpkin genome, high-density genetic map is essential for anchoring and orienting the assembled scaffolds. In addition, a saturated genetic map can facilitate quantitative trait locus (QTL) mapping.
  
  
  RESULTS
  A set of 186 F2 plants derived from the cross of pumpkin inbred lines Rimu and SQ026 were genotyped using the genotyping-by-sequencing approach. Using the SNPs we identified, a high-density genetic map containing 458 bin-markers was constructed, spanning a total genetic distance of 2,566.8 cM across the 20 linkage groups of C. maxima with a mean marker density of 5.60 cM. Using this map we were able to anchor 58 assembled scaffolds that covered about 194.5 Mb (71.7%) of the 271.4 Mb assembled pumpkin genome, of which 44 (183.0 Mb; 67.4%) were oriented. Furthermore, the high-density genetic map was used to identify genomic regions highly associated with an important agronomic trait, dwarf vine. Three QTLs on linkage groups (LGs) 1, 3 and 4, respectively, were recovered. One QTL, qCmB2, which was located in an interval of 0.42 Mb on LG 3, explained 21.4% phenotypic variations. Within qCmB2, one gene, Cma_004516, encoding the gibberellin (GA) 20-oxidase in the GA biosynthesis pathway, had a 1249-bp deletion in its promoter in bush type lines, and its expression level was significantly increased during the vine growth and higher in vine type lines than bush type lines, supporting Cma_004516 as a possible candidate gene controlling vine growth in pumpkin.
  
  
  CONCLUSIONS
  A high-density pumpkin genetic map was constructed, which was used to successfully anchor and orient the assembled genome scaffolds, and to identify QTLs highly associated with pumpkin vine length. The map provided a valuable resource for gene cloning and marker assisted breeding in pumpkin and other related species. The identified vine length QTLs would help to dissect the underlying molecular basis regulating pumpkin vine growth.
authors.affiliation: Beijing Vegetable Research Center, BAAFS, Key Laboratory of Biology and Genetic Improvement of Horticultural Crops (North China), Ministry of Agriculture, Beijing Key Laboratory of Vegetable Germplasm Improvement, Beijing, 100097, P.R. China. zhangguoyu@nercv.org.
authors.forename: Guoyu
authors.initials: G
authors.lastname: Zhang
authors.affiliation: Beijing Vegetable Research Center, BAAFS, Key Laboratory of Biology and Genetic Improvement of Horticultural Crops (North China), Ministry of Agriculture, Beijing Key Laboratory of Vegetable Germplasm Improvement, Beijing, 100097, P.R. China. renyi@nercv.org.
authors.forename: Yi
authors.initials: Y
authors.lastname: Ren
authors.affiliation: Beijing Vegetable Research Center, BAAFS, Key Laboratory of Biology and Genetic Improvement of Horticultural Crops (North China), Ministry of Agriculture, Beijing Key Laboratory of Vegetable Germplasm Improvement, Beijing, 100097, P.R. China. hs738@cornell.edu.|Boyce Thompson Institute for Plant Research, Cornell University, Ithaca, NY, 14853, USA. hs738@cornell.edu.
authors.forename: Honghe
authors.initials: H
authors.lastname: Sun
authors.affiliation: Beijing Vegetable Research Center, BAAFS, Key Laboratory of Biology and Genetic Improvement of Horticultural Crops (North China), Ministry of Agriculture, Beijing Key Laboratory of Vegetable Germplasm Improvement, Beijing, 100097, P.R. China. guoshaogui@nercv.org.
authors.forename: Shaogui
authors.initials: S
authors.lastname: Guo
authors.affiliation: Beijing Vegetable Research Center, BAAFS, Key Laboratory of Biology and Genetic Improvement of Horticultural Crops (North China), Ministry of Agriculture, Beijing Key Laboratory of Vegetable Germplasm Improvement, Beijing, 100097, P.R. China. zhangfan@nercv.org.
authors.forename: Fan
authors.initials: F
authors.lastname: Zhang
authors.affiliation: Beijing Vegetable Research Center, BAAFS, Key Laboratory of Biology and Genetic Improvement of Horticultural Crops (North China), Ministry of Agriculture, Beijing Key Laboratory of Vegetable Germplasm Improvement, Beijing, 100097, P.R. China. zhangjie@nercv.org.
authors.forename: Jie
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Beijing Vegetable Research Center, BAAFS, Key Laboratory of Biology and Genetic Improvement of Horticultural Crops (North China), Ministry of Agriculture, Beijing Key Laboratory of Vegetable Germplasm Improvement, Beijing, 100097, P.R. China. zhanghaiying@nercv.org.
authors.forename: Haiying
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Beijing Vegetable Research Center, BAAFS, Key Laboratory of Biology and Genetic Improvement of Horticultural Crops (North China), Ministry of Agriculture, Beijing Key Laboratory of Vegetable Germplasm Improvement, Beijing, 100097, P.R. China. jiazhangcai@nercv.org.
authors.forename: Zhangcai
authors.initials: Z
authors.lastname: Jia
authors.affiliation: Boyce Thompson Institute for Plant Research, Cornell University, Ithaca, NY, 14853, USA. zf25@cornell.edu.|USDA-ARS, Robert W. Holley Center for Agriculture and Health, Ithaca, NY, 14853, USA. zf25@cornell.edu.
authors.forename: Zhangjun
authors.initials: Z
authors.lastname: Fei
authors.affiliation: Beijing Vegetable Research Center, BAAFS, Key Laboratory of Biology and Genetic Improvement of Horticultural Crops (North China), Ministry of Agriculture, Beijing Key Laboratory of Vegetable Germplasm Improvement, Beijing, 100097, P.R. China. xuyong@nercv.org.
authors.forename: Yong
authors.initials: Y
authors.lastname: Xu
authors.affiliation: Beijing Vegetable Research Center, BAAFS, Key Laboratory of Biology and Genetic Improvement of Horticultural Crops (North China), Ministry of Agriculture, Beijing Key Laboratory of Vegetable Germplasm Improvement, Beijing, 100097, P.R. China. lihaizhen@nercv.org.
authors.forename: Haizhen
authors.initials: H
authors.lastname: Li
mesh_terms: D002874:Chromosome Mapping; D028464:Cucurbita / Q000235:genetics* / Q000378:metabolism; D018745:Genome, Plant; D023281:Genomics; D005838:Genotype; D005875:Gibberellins / Q000096:biosynthesis; D059014:High-Throughput Nucleotide Sequencing; D010641:Phenotype; D020641:Polymorphism, Single Nucleotide; D040641:Quantitative Trait Loci
chemical_list: D005875:Gibberellins