Chromosomal Variation in Crocus vernus Hill (Iridaceae) Investigated by in situ Hybridization of rDNA and a Tandemly Repeated Sequence

The physical localization of three tandemly-organized repetitiveDNA sequences was investigated byin situ hybridization to metaphasechromosomes of 11 Crocus vernus accessions. The sequences includedwere the 18S–25S rDNA, the 5S rDNA and a tandemly-repeatedsequence cloned from C. vernus(clone pCvKB8). Ten 2n = 8 karyotypesfrom accessions ranging across the Alps and the Pyrenees couldbe interpreted as variations of a standard karyotype. Polymorphismswere found involving size of the satellite chromosomes, extra5S rDNA sites, and extensive differences in size and numberof pCvKB8 loci. The 2 n = 16 type did not correspond to anypossible tetraploid derived from the 2 n = 8 types. Copyright2000 Annals of Botany Company Evolution, phylogeny, Crocus vernus Hill (Iridaceae), in situ hybridization, chromosomal polymorphism, karyotype evolution, repetitive DNA