1 Laboratory of Plant Breeding Wageningen University PO Box 386 6700 AJ Wageningen The Netherlands 2 Keygene PO Box 216 6700 AE Wageningen The Netherlands
The most complete published genetic map of lettuce is based on an intraspecific L. sativa cross (Calmar x Kordaat) and comprises 152 RFLP markers and 130 RAPDs on 13 major linkage groups, while lettuce has nine chromosomes. In order to construct a dense genetic linkage map, covering the nine chromosomes, an interspecific cross was made between the cultivated lettuce L. sativa and the wild related species L. saligna. As L. saligna is genetically very remote from L. sativa it was expected that AFLP® marker analysis would easily reveal high numbers of polymorphisms. Indeed, 80 % of the AFLP® amplification products were specific for one of the two parent species. A total of 126 F2 plants from this interspecific cross were AFLP®-fingerprinted by using twelve EcoRI-MseI primer combinations. In total, 497 amplification products were scored and 398 were mapped unambiguously, 207 as codominant and 191 as dominant markers. In addition, 11 microsatellites were scored, four codominantly and seven dominantly. By using the software mapping program Joinmap 2.0 and a threshold LOD value for grouping of 6.0, ten linkage groups were identified. The two smallest linkage groups probably correspond to the same chromosome. The total map comprises 409 markers and has a total genetic length of 876 cM. Three linkage groups in the map showed severe skewness of markers at the distal parts of the chromosome and for one linkage group all markers showed skewness. In addition, a genetic map was constructed from another interspecific F2 population from a cross between L. sativa and another L. saligna accession. The resulting map was very similar to the one described above. Reference: Rick V. Kesseli, Ilan Paran and Richard Michelmore (1994). Analysis of a detailed genetic linkage map of Lactuca sativa (Lettuce) constructed from RFLP and RAPD markers. Genetics 136:1435-1446. AFLP® is a registered trademark of Keygene N.V.
Plant & Animal Genome VIII Conference Plant & Animal Genome VIII Conference