The authors report the first discovery of diploid populations of Hieracium naegelianum Panč. subsp. naegelianum and H. naegelianum subsp. ljubotenicum Behr & Zahn., and give the first chromosome counts for H. cernuum Friv., H. gymnocephalum Griseb. ex Pant., H. sparsum Friv., Pilosella pavichii (Heuff.) Holub and P. serbica (F. W. Schultz & Schultz-Bip.) Szeląg from Macedonia and/or Montenegro. A diploid chromosome count for Hieracium renatae Szeląg is confirmed based on material from the whole distribution range of the species. An emasculation experiment showed that all the analyzed diploid Hieracium taxa reproduce sexually.

Chromosome numbers of 46 Hieracium L. and Pilosella Vaill. taxa from Austria, Bulgaria, Czech Republic, Macedonia, Montenegro, Poland, Romania, Serbia and Slovakia are presented. Chromosomes numbers are given for the first time for Hieracium amphigenum Briq. 2n = 3× = 27, H. bohatschianum Zahn 2n = 4× = 36, H. borbasii R. Uechtr. 2n = 4× = 36, H. cernuum Friv. 2n = 2× = 18, H. hazslinszkyi Pax 2n = 3× = 27, H. mirekii Szeląg 2n = 4× = 36, H. polyphyllobasis (Nyár. & Zahn) Szeląg 2n = 3× = 27, H. porphyriticum A. Kern. 2n = 4× = 36, H. racemosum Waldst. & Kit. ex Willd. subsp. racemosum 2n = 3× = 27, H. scardicum Borm. & Zahn 2n = 4× = 36, H. sparsum subsp. ipekanum Rech. fil. & Zahn 2n = 4× = 36, H. sparsum subsp. peristeriense Behr & Zahn, H. sparsum subsp. squarrosobracchiatum Behr & al. 2n = 3× = 27, H. tomosense Simk. 2n = 4× = 36, H. tubulare Nyár. 2n = 4× = 36, H. werneri Szeląg 2n = 3× = 27 and Pilosella fusca subsp. subpedunculata (Zahn) Szeląg, as well as five species of Hieracium sect. Cernua R. Uechtr. not described to date and a hybrid between H. bifidum s. lat. and H. pojoritense Woł

Abstract RAPD analysis was applied to assess the degree of DNA polymorphism in A. fistulosum calli of high chromosomal instability. Nineteen of 24 randomly selected RAPD primers revealed scorable polymorphism between calli and seeds (reference material). Polymorphic band frequency was 55/237 in seeds and 36/233 in calli; variability on the DNA level was thus lower in calli than in seeds (15.4% vs. 23.2% of band positions). UPGMA analysis of Jaccard's coefficients confirmed the genetic similarity of the analyzed cultures. The most distinctive DNA changes in calli involved coincident loss of original bands or the appearance of novel bands. Seven such changes (4 losses, 3 gains) were observed. Our results suggest that changes on the chromosomal level and on the DNA level occurred independently of each other and that different callus lines underwent similar genetic changes during culture, presumably due to strong selection pressure effected by standard in vitro conditions.