Towards an expanded and integrated linkage map of cucumber (Cucumis sativus L.)

Linkage maps in cucumber (Cucumis sativus var. sativus L.) have been constructed using morphological traits, isozymes, restriction fragment length polymorphisms (RFLPs), and random amplified polymorphic DNAs (RAPDs). The lack of polymorphism in cucumber has led to the construction of relatively unsaturated maps (13- to 80-point). We have added amplified fragment length polymorphism (AFLP) markers to existing narrow-based (within C. sativus) and wide-based (C. sativus x C. sativus var. hardwickii) maps. JOINMAP v. 2.0 was used to construct maps and to join these with historical maps from several previous studies. Our narrow- and wide-based merged maps contain 255 and 197 markers, respectively, including morphological traits, disease resistance loci, isozymes, RFLPs, RAPDs, and AFLPs. Condensation of total map distance occurred in merged maps compared to historic maps using many of the same markers. This phenomenon is most likely due to differences in map construction algorithms. The merged maps represent the best fit of the data used and are an important first step towards the construction of a comprehensive linkage map for cucumber. Identification of additional anchor markers between the narrow- and wide-based maps presented here may allow their future integration into a unified model.