CONSTRUCTION OF A LINKAGE MAP IN CUCUMIS MELO (L.) USING RANDOM AMPLIFIED POLYMORPHIC DNA MARKERS

Abstract

We are now in the course of constructing a linkage map mainly using random amplified polymorphic DNA (RAPD) markers, for locating and studying several disease resistance genes in Cucumis melo L. Here we report some of our work based on the RAPD mapping. In RAPD analysis, restriction enzymes were used to digest template DNA before PCR for searching polymorphisms. It has been reported previously that enzyme digestion may cause the change of electrophoretic banding patterns (Williams, et al., 1993). In this study, we have found that the use of restriction enzymes is very helpful to detect new polymorphisms. The more enzymes used, the more polymorphic RAPD markers could be detected, thus enhancing the efficiency of the mapping process. An experimental population, consisting of 2 parents, 5 F1 hybrids, and 77 F2 progenies derived from one of the F1 plants, was used for polymorphic marker screening and segregation data collection. MAPMAKER/EXP computer program was used for linkage analysis. The updated linkage map comprises 125 RAPD markers in 29 linkage groups, and has 1347.9 cM in total. There are 61 unlinked markers. We estimate that the present map may have covered 42–59 % of the total genome.