VARIATION IN TARAXACUM-BESSARABICUM AND ALLIED TAXA OF THE SECTION PIESIS (COMPOSITAE) - ALLOZYME DIVERSITY, KARYOTYPES AND BREEDING-BEHAVIOR

Allozyme techniques, karyotype analyses and cultivation experiments we re carried out on 20 population samples of Taraxacum sect. Piesis (Com positae), viz. T bessarabicum (17 samples from W. and C. Europe, Ukrai ne and Crimea, Central Asia and the Altai), T salsum from Crimea, T x mesohalobium from Crimea, and T stenolepium from the Caucasus. The tax a studied share a primitive, symmetrical karyotype. All taxa studied a re sexual, T bessarabicum mostly autogamous. Sexuality at the tetraplo id level (T stenolepium) and occasional male sterility in a sexual (T bessarabicum in Moravia) were recorded for the first time in the genus . Selfing, diploidy and the highly predictable habitat may account for the mostly low level within population allozyme variation in T bessar abicum. W. and C. European samples of T bessarabicum are almost invari able allozymically and, as a group, have no unique alleles. The Crimea n and Asian group of populations shows higher levels of allozyme varia tion and has 15 alleles not found in the former group at 13 loci studi ed. Recent migration from one source region is suggested to account fo r the homogeneity of the western group, refugial persistence of allele s and possible introgression from sympatric species may have resulted in allele richness in the eastern group. Hybridization between T bessa rabicum and T salsum was documented by allozyme patterns in a few plan ts in Crimea. Some aberrant allozyme or karyotypic features of two pop ulations are discussed as well.