Amounts of ribosomal DNA inAllium (Liliaceae)

Eight species ofAllium subgen.Allium sect.Allium have been studied at the cytological level by means of karyological analyses and at the biochemical level with regard to the proportions of ribosomal DNA. All the species have a basic genome of x = 8.A. sativum, A. commutatum, A. ampeloprasum, andA. vineale possess approximately 0.050% rDNA and two nucleolus organizer regions per basic chromosome set.A. sphaerocephalon andA. arvense have two nucleolus organizers, andA. amethystinum three nucleolus organizers per haploid (n = x) genome: the three species possess approximately 0.075% rDNA.A. acutiflorum has five nucleolus organizer regions per haploid genome and 0.121% rDNA. An attempt to relate these differences with functional and ecological characteristics indicates that evolutionary variation of rDNA proportions is not casual. Such data also can help to define systematic affinities and circumscribe infrageneric taxa.