Search Results

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 ≈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 × H-19 RIL-based genetic map shared 94 marker loci with a previously reported RIL-based linkage map derived from a wide cross between C. sativus var. sativus 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.

Scab, caused by Cladosporium cucumerinum Ell. et Arthur, is a prevalent disease of cucumber (Cucumis sativus L.) worldwide. Scab can cause serious losses for cucumber production, especially in protected culture such as high tunnel production. Resistance to cucumber scab is dominant and is controlled by a single gene, Ccu. Breeding for resistant cultivars is the most efficient way to control the disease. Selection for resistance might be made easier if the gene were mapped to linked markers. Thus far, there are no tightly linked (genetic distance less than 1 cM) simple sequence repeat (SSR) markers for the Ccu gene, and no studies on mapping of the Ccu gene in cucumber using SSR markers. The objective of this study was to identify SSR markers for use in molecular breeding of scab resistance. In this study, we used a population of recombinant inbred lines (RILs). The population included 148 individuals derived from the cucumber inbred line 9110 Gt (Ccu Ccu) crossed with line 9930 (ccu ccu). The Ccu gene was mapped to linkage group 2, corresponding to chromosome 2 of cucumber. The flanking markers SSR03084 and SSR17631 were linked to the Ccu gene with distances of 0.7 and 1.6 cM, respectively. The veracity of SSR03084 and SSR17631 was tested using 59 diverse inbred lines and hybrids, and the accuracy rate for the two markers was 98.3%. In conclusion, two SSRs closely linked to scab resistance gene Ccu have been identified and can be used in a cucumber breeding program.