Chromosomal variation in Crocus vernus Hill (Iridaceae) investigated by insitu hybridization of rDNA and a tandemly repeated sequence

The physical localization of three tandemly-organized repetitive DNA sequen ces was investigated by in situ hybridization to metaphase chromosomes of 1 1 Crocus vernus accessions. The sequences included were the 18S-25S rDNA, t he 5S rDNA and a tandemly-repeated sequence cloned from C. vernus (clone pC vKB8). Ten 2n = 8 karyotypes from accessions ranging across the Alps and th e Pyrenees could be interpreted as variations of a standard karyotype. Poly morphisms were found involving size of the satellite chromosomes, extra 5S rDNA sites, and extensive differences in size and number of pCvKB8 loci. Th e 2n = 16 type did not correspond to any possible tetraploid derived from t he 2n = 8 types. (C) 2000 Annals of Botany Company.