Construction of a genetic linkage map in celery using DNA-based markers.

A F2 population of two celery cultivated types (Apium graveolens L. var. rapaceum and A. graveolens L. var. secalinum) was used to construct a linkage map consisting of 29 RFLP (restriction fragment length polymorphism), 100 RAPD (random amplified polymorphic DNA), four isozyme, one disease resistance, and one growth habit markers. The map contains 11 major groups and 9 small groups and has a total length of 803 cM with an average distance of 6.4 cM between two adjacent loci. Ten percent of the RAPDs segregated as codominant markers and their allelic homologies were tested by Southern hybridization. One-quarter of the dominant RAPDs were linked in repulsion phase, whereas the majority of them were linked to either codominant or dominant markers in coupling phase. About 10% of the markers showed significant segregation distortion. The detectable level of duplications in the celery genome was relatively low.