INTEGRATION OF THE CLASSICAL AND MOLECULAR LINKAGE MAPS OF TOMATO CHROMOSOME-6

In the past, a classical map of the tomato genome has been established that is based on linkage data from intraspecific Lycopersicon esculen tum crosses. In addition, a high density molecular linkage map has rec ently been constructed using a L. esculentum X L. pennellii cross. As the respective maps only partially match, they provide limited informa tion about the relative positions of classical and molecular markers. In this paper we describe the construction of an integrated linkage ma p of tomato chromosome 6 that shows the position of cDNA-, genomic DNA - and RAPD markers relative to 10 classical markers. Integration was a chieved by using a L. esculentum line containing an introgressed chrom osome 6 from L. pennellii in crosses to a variety of L. esculentum mar ker lines. In addition, an improved version of the classical linkage m ap is presented that is based on a combined analysis of new linkage da ta for 16 morphological markers and literature data. Unlike the classi cal map currently in use, the revised map reveals clustering of marker s into three major groups around the yv, m-2 and c loci, respectively. Although crossing-over rates are clearly different when comparing int raspecific L. esculentum crosses with L. esculentum x L. pennellii cro sses, the clusters of morphological markers on the classical map coinc ide with clusters of genomic- and cDNA-markers on the molecular map co nstructed by Tanksley and coworkers.