A Genetic Linkage Map including Loci for Male Sterility, Sugars, and Ascorbic Acid in Melon

Our objectives were to construct a randomly amplified polymorphic DNA (RAPD) marker-based linkage map using an F2 population derived from the melon (Cucumis melo) cross of 'Deltex' · TGR 1551, and map quantitative trait loci (QTL) for sucrose, total soluble solids (TSS), ratio of sucrose to total sugars (RSTS), and ascorbic acid as well as the ms-3 locus for male sterility previously reported in other muskmelon crosses. Due to the dominant character of RAPD markers, we scored 192 'Deltex'- and 158 TGR 1551-derived markers. One hundred eighty (94%) of the 192 markers fit the expected 3:1 ratio. On the basis of the 180 markers, we constructed a 'Deltex' linkage map of 171 markers distributed on 12 linkage groups (LGs) with a total map distance of 1182 cM. One hundred fifty (95%) of the 158 markers were identified to be nondistorted. We developed a TGR 1551 linkage map of 138 markers distributed on 12 LGs with a total distance of 1163 cM. A combined map of 12 LGs with a total map distance of 1394 cM was made from 82 marker pairs expressing codominance. Nine LGs were integrated into those of the existing composite map by 17 anchor markers. We mapped the ms-3 locus for male sterility on LG 9, which corresponds to LG 10 of the classical mapand LG VII of the composite map. Six QTL for sucrose were located on LGs 2, 3, 4, 6, and 11. Three on LGs 3, 4, and 6 and four on LGs 2, 3, 6, and 11 of the six QTL for sucrose were also noted to be QTL for TSS and RSTS, respectively. A single QTL for ascorbic acid was placed on LG 5. This map will also be used to identify QTL for fruit sweetness, quality, size, and shape traits, as well as disease resistance.