CROSSABILITY ANALYSIS IN SUBGENUS TULIPA OF THE GENUS TULIPA L

A range of almost 1400 cross combinations has been carried out between 31 species of Tulipa subgenus Tulipa. Most of the sections are well s eparated reproductively from each other. The designated species aggreg ates in section Clusianae appeared to be intersterile. Also in section Kolpakowskianae the species, as far as used, cannot be combined. Some crosses between species of section Tulipanum succeeded. The species o f sections Eichleres and Tulipa (including the cultivated tulip T. ges neriana) could be combined in various ways, although the highest level of seed set was achieved within either section. The crossability data support the current taxonomic division. The level of reproductive iso lation between sympatric species is discussed, and the importance of c rossability studies for plant breeding in Tulipa pointed out briefly.