An Extended Intervarietal Microsatellite Linkage Map of Cucumber, Cucumis sativus L.

A recombinant inbred line (RIL) population derived from two cultivated cucumber (Cucumis sativus var. sativus L., 2n = 2x = 14) lines, Gy7 (synonym G421) and H-19, was previously used to map yield and fruit quality components. However, the map consisted mainly of dominant markers (i.e., random amplified polymorphic DNAs or amplified fragment length polymorphisms) limiting its use in plant improvement and map-based gene cloning. We report here a moderately saturated genetic map derived from this RIL population that incorporates codominant microsatellite [simple sequence repeat (SSR)] markers and two architectural traits, little leaf (ll) and determinate (de), growth habit. Of 821 cucumber genomic SSR primer pairs evaluated for map construction, 140 (17.0%) were polymorphic between the mapping parents. In combination with 42 previously mapped sequence characterized amplified region (SCAR) and SSR makers, these polymorphic markers were used to construct a linkage map with 46 RILs and 176 mapped loci spanning approximate to 400 cM across seven linkage groups (LG). The numbers of loci mapped on LG 1 through 7 were 11, 6, 35, 18, 46, 45, and 15, respectively. The ll locus was flanked by SSR02355 and SSR03940 (4.2 and 3.6 cM from ll, respectively), and de was flanked by CSWCTT14b and SSR13251 (1.4 and 4.2 cM from the de, respectively). The SSR markers linked with the de and ll genes were mapped to Chromosome 6. No recombination suppression was detected among the mapped loci examined. This Gy7 x H-19 RIL-based genetic map shared 94 marker loci with a previously reported Rh-based linkage map derived from a wide cross between C. sativus var. swims line Gy14 and C. sativus var. hardwickii Alef. R. PI 183967. Comparative mapping supported previous findings that genomic differences (likely chromosomal rearrangements) exist between Gy14 and PI 183967.