XVI International Botanical Congess

By regular caryological investigation (over 20 years) of population of Crepis pannonica in the south of the area (Armenia, Chosrov) a striking spontaneous polymorphism is discovered. Population is presented with diploid (2n=2x=8) and triploid (2n=3x=12)cytoraces. But seed progeny is characterized by polymorphism according to the autosome number (2n=8,9,10,11,12,13,14,15,16) and B-chromosome (1,2,3,4,6 B-chromosomes of standard and derivative type). 40 variants of number polymorphisms are fixed. A great range of structural chromosome mutation is discovered, 9 structural heterozygotes are discribed.High level of structural rearrangement of caryotype in a concrete population is a precondition of B-chromosomes creation. B-chromosomes are viewed as centric fragments appearing during structural changes. It is obvious, that this population characterizing by this kariological lability is a center of variety-formation and speciation.