Cytometric determination of genome size in Colchicum species (Liliales, Colchicaceae) of the western Mediterranean area

Abstract

Genome size has been studied for the first time in the Colchicum genus. Values obtained by flow cytometry were quite stable and specific to each taxon: C. autumnale L., 2C=5.89±0.22 pg, equivalent to 5.7×109 bp (2n=4x=36); C. alpinum DC., 2C=8.06±0.24 pg, equivalent to 7.8×109 bp (2n=6x=56); C. lusitanum Brot., 2C=10.7±0.67 pg, equivalent to 10.3×109 bp (2n= approx. 10x=90–92 and 94–96); C. multiflorum Brot., 2C=16.5±0.69 pg, equivalent to 15.9×109 bp, (2n= approx. 16x=140–148); C. corsicum Baker, 2C=21.3±0.99 pg, equivalent to 20.6×109 bp (2n=22x= approx. 198±2). These values are well below those published for Liliaceae stricto sensu. In Colchicum species from the western Mediterranean area, genome size was highly correlated with ploidy level (R 2=0.99, P<0.001). This relationship is consistent with most previous results, with our new chromosome number count for C. corsicum and with our correction of published erroneous counts for C. lusitanum (2n=102–108). The Calabrian population appeared to be distinct from all of the other plants of the C. alpinum group. Reproducible and accurate, cytometry appears to be a particularly appropriate method for studying this polyploid genus in Western Europe, taking into account that chromosome numbers are difficult to enumerate. It can guide future taxonomic research because it reveals similarities or differences between taxa within this difficult complex.