family comprises about 120 genera and 800 species, including many economically important vegetable and fruit crops such as cucumber (Cucumis sativus
L.), melon (C. melo
L.), watermelon (Citrullus lanatus
(Thunb.) Matsum. & Nakai), squash and pumpkin (Cucurbita spp
. Cucurbits are mostly prostrate or climbing herbaceous annuals that have coiled tendrils and they are characterized by having unisexual flowers and inferior ovaries. Although cucurbits vary in chromosome numbers, their genome sizes have not changed as significantly as in some other botanical families like Brassicaceae and Poaceae (e.g., cucumber: 2n
14, 367 Mb; melon: 2n
24, 480 Mb; watermelon: 2n
22, 430 Mb, and squash and pumpkin: 2n
40, 539 Mb) 
. It seems that chromosome numbers of cucurbits correlate directly with their genome sizes. Differences in cucurbit genome size might be attributable to the structure and position of centromeres and telomeres, and the other repeat-related genomic elements. Genomic resources for cucurbits are scarce, and high density genetic linkage maps have not been reported for cucurbit species. This lack of genomic information seriously hampers genome assembly and genetic analysis in cucurbits.
In the genus of Cucumis
, cucumber is the only species with a haploid chromosome number of seven (for other Cucumis
species, basic number
12). It is cross-incompatible with other Cucumis
species and consequently, cucumber has a narrow genetic basis within domesticated market types 
. India was thought to be the center of origin and domestication of this species where two botanical varieties C. s.
L. (cultivated) and the feral form C. s.
(R.) Alef coexist.
Unsaturated cucumber linkage maps have been developed using morphological traits, isozymes, and molecular markers, where markers (<300 loci) were often positioned in more than seven linkage groups 
. Cytogenetic maps have also been constructed in cucumber using C-banding and fluorescence in situ
hybridization (FISH) 
, allowing identification of seven morphologically distinct chromosomes. However, none of the maps ware integrated with cytogenetic map. Marker-trait associations have been effective in achieving selection gain for yield components during marker-assisted backcrossing 
, but marker-assisted selection (MAS) of quantitative trait loci seems to be unpredictable due to lack of a high-resolution genetic map 
The availability of high-density maps in cucumber would facilitate whole genome sequencing and positional cloning, enhance MAS, and provide opportunities to investigate synteny among cucurbit species (e.g., cucumber and melon). SSRs (simple sequence repeats) or microsatellites are tandem repeats of short DNA sequences ranging in length from one to six base pair (bp), which are abundant and ubiquitous in all eukaryotic genomes 
. Because of their high level of polymorphism, ubiquity, and co-dominance, SSRs have become a valuable source of molecular markers in genetic analysis 
. Only a limited number of SSR markers, however, have been developed for cucumber through exploiting EST sequences and screening genomic libraries 
, which has hampered use of molecular markers in genetic analysis and MAS in cucurbits.
We present herein the development of a saturated SSR-based cucumber linkage map employing 3× Sanger shotgun sequences. We used FISH to assign linkage groups to a cytogenetic map and to define chromosomal rearrangements between C. sativus var. sativus and var. hardwickii. The integrated genetic-cytogenetic map described herein provides a platform for genetic and genomic analysis that does not currently exist in cucurbits.