extended linkage map for watermelon based on SRAP, AFLP, SSR, ISSR, and RAPD markers

Seventy-one amplified fragment length polymorphism (AFLP), 93 sequence related amplified polymorphism (SRAP), and 14 simple sequence repeat (SSR) markers were used to extend an initial genetic linkage map for watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai]. The initial map was based on 151 randomly amplified polymorphic DNA (RAPD) and 30 and inter-simple sequence repeat (ISSR) markers. A testcross population previously used for mapping of RAPD and ISSR markers was used in this study: (plant accession Griffin 14113 [C. lanatus var. citroide (L.H. Bailey) Mansf.] x the watermelon cultivar New Hampshire Midget (C. lanatus var. lanatus)) x PI 386015 [C. colocynthis (L.) Schrad.]. The linkage map contains 360 DNA markers distributed on 19 linkage groups, and covers a genetic distance of 1976 cM with an average distance of 5.8 cM between two markers. A genomic DNA clone representing 1-amino-cyclopropane-1-carboxylic acid (ACC-) synthase gene, involved in ethylene biosynthesis, was also mapped. As in previous mapping studies for watermelon, a large number of AFLP and SRAP markers were skewed away from the 1:1 segregation ratio, and had to be excluded from the final mapping analysis. The stringent mapping criteria (JoinMap 3.0 mapping program) produced linkage groups with marker order consistent with those reported in previous mapping study for watermelon.