To merge two or more linkage maps using JoinMap, begin by ensuring you have the software installed on your computer, which you can download from the official JoinMap website. Prepare your data files for each linkage map, making sure they include marker names and genotype information in supported formats such as Excel or text files. Open JoinMap and create a new project, specifying the directory for your data files. Import the datasets for each linkage map into the project. Identify common markers between the different linkage maps within JoinMap, as these will serve as reference points for merging. Create linkage groups for each dataset, allowing JoinMap to assign markers based on their recombination frequencies. Use the 'Join' function to align linkage groups from different datasets, leveraging the common markers for accurate alignment. Execute the merging process, and JoinMap will integrate the maps into a single linkage map. Review and edit the merged map to ensure accuracy, resolving any discrepancies. Finally, export the merged linkage map from JoinMap in your desired format. Ensure consistency in marker names and data formats.