Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/15/2006
Publication Date: 1/20/2007
Citation: Staub, J.E., Sun, Z., Chung, S., Lower, R.L. 2007. Colinearity among genetic linkage maps in cucumber. HortScience. 40:20-27. Interpretive Summary: It is important for cucumber breeders to know the location of genes (inherited units that cause trait expression) on chromosomes (an array of genes) in order to increase breeding efficiency and effectiveness. Cucumber breeders have constructed gene maps (groups of chromosomes depicting the organization of the genetic structure of an organism) in the last 15 years. These maps have been created using different genetic material (parents used in crossing to create maps) and techniques (crossing schemes between parents to make hybrids) and thus it has been difficult to compare them to determine if genes from one map are the same and in the same position (in the array of genes on chromosomes) on chromosomes. Thus, a project was designed to compare the genetic maps that have been constructed in cucumber in order to examine the position of genes on chromosomes. Results indicate that genes on chromosomes in the maps examined are in the same position. This is important because now plant breeders can use information on the map interchangeably. This allows the plant breeder or geneticist flexibility in creating lines and hybrids (line crossed with a line) to test for improved yield and quality traits. This increases the efficiency and effectiveness of plant breeders for the development of improved cucumber hybrids that is needed in commercial production. This allows new, unique hybrids to be marketed rapidly so that the U.S. grower can be more competitive in the global market place to insure sustained economical advantage of U.S. agriculture.
Technical Abstract: Hybrid development in cucumber (Cucumis sativus L. var. sativus; 2n = 2x = 14) involves the ubiquitous use of closely related (3-8% polymorphism) elite lines. Given this, and the existence of only few relatively unsaturated genetic maps, a molecular marker map position assessment was performed to appraise the relative degree of map colinearity in this species. The position of random amplified polymorphic DNAs (RAPD), sequenced characterized amplified regions (SCARs), simple sequence repeat (SSR), restriction fragment length polymorphisms (RFLP), and fluorescent amplified fragment length polymorphism (fAFLP) markers were compared in maps constructed from four diverse populations. Maps by Fazio et al. (2003; narrow-based processing type; C. s. var. sativus; ~12% polymorphism), Bradeen et al. [2001; narrow (C. s. var. sativus; ~8% polymorphism) - and broad (C. s. var. sativus x C. s. var. hardwickii (R.) Alef.; ~12%)-based ], and a narrow-based map in processing cucumber constructed from a line 2A x Gy8 mating (C. s. var. sativus; ~7% polymorphism) were compared. In seven linkage groups (LG), 19 [i.e., fAFLP (17), SSR (1), and RAPD (1)], 43 [fAFLP (11), SCAR (13), RAPD (17), little leaf (ll) and determinate (de)], 18 [fAFLP (2), RFLP (9), RAPD (6), and downy mildew (dm)], and 3 [fAFLP (1), RAPD (2), and gynoecious (F)] markers were found to be common between the 2A x Gy8 map and that of Fazio et al. (2003a), Fazio et al. (2003a) and Bradeen et al. (2001; narrow-based), Bradeen et al. (2001) narrow- and broad-based, and Bradeen et al. (2001; broad-based) and Fazio et al. (2003a), respectively. Three markers (fAFLP E14M62-214, and SCAR/RAPD AA9B and BC388) were found to be common between maps of Fazio et al. (2003) and Bradeen et al. (2001). Common markers in LG 1 between the 2A x Gy8, Fazio et al. (2003), and Bradeen et al. (2001;broad-based) maps were used as anchor markers for map position comparisons of yield component quantitative trait loci (QTL). The relative order of anchor markers in each of six linkage groups (LG1, 2, 4-7) that possessed two or more anchor markers within each group was collinear. Commonalities in the position of some yield component QTL exist in LG1 of the maps examined, and general synteny among these maps indicates the potential value of map merging to increase cucumber map saturation for universal application to breeding.