A FIRST LINKAGE MAP OF CICHORIUM-INTYBUS L. USING A ONE-WAY PSEUDO-TESTCROSS AND PCR-DERIVED MARKERS

We have used a one-way pseudo-testcross mapping strategy in combinatio n with different types of PCR-based markers (RAPD, AFLP, SAMPL) to con struct a first linkage map for variegated chicory (Cichorium intybus L . var. silvestre Biskoff, n = 9), a self-incompatible vegetable specie s. The success of such a strategy depends on the presence of sufficien tly high levels of heterozygosity in the individual plant which is bei ng mapped and on the informativeness of the marker system that is used . A total of 371 markers, comprising 16 RAPDs, 72 SAMPLs and 283 AFLPs , were scored in 46 F-1 individuals obtained from an interspecific cro ss between a C. intybus outbred individual and a C. endivia inbred lin e. Grouping of the markers at a LOD score of 4.0 resulted in 13 Linkag e groups covering 1330 cM. A framework map covering 1201.4 cM was asse mbled by using all markers that could be ordered with a LOD greater th an 2.0. We estimate the total genome size of chicory to be ca. 1405 cM , thus considerably smaller than that estimated for lettuce (1950 cM). The usefulness of the different marker systems that were applied is a nalysed in terms of level of heterozygosity and marker index, i.e. num ber of different genetic loci that may be simultaneously analysed per experiment. Out of the 371 markers, 50 of them showed segregation dist ortion which is discussed in terms of the hybrid origin of the variega ted chicory.