One of the earliest examples of a high-density molecular marker map was in tomato.
This is just one of the 12 chromosomes of tomato, from the 1992 genetic map (Tanksley et al. 1992).
The markers in “( )” could not be ordered at a LOD of 3, only 2; they are placed in the position that they are most likely, as this could still be helpful information to some researchers.
Note also that some markers clustered together and could not be ordered. This could be a function of the relatively small population (67 F2 progeny); a larger population might give better resolution.
These markers are RFLPs; however, since this publication many have been converted into sequence-tagged primers that can be used as PCR markers (available at http://www.sgn.cornell.edu).