The systematic value of nuclear DNA content in Galanthus

Abstract

Genome size (Cx-value) was applied as a new criterion to investigate the relationships within the genus Galanthus L. (Amaryllidaceae). More than 150 samples representing all species, from wild and cultivated material, were investigated. Most species of Galanthus have the same basic chromosome number (2n=2x=24). However, the somatic nuclear DNA contents (2C), as measured by flow cytometry with propidium iodide was shown to range from 48.6 to 90.4 pg for the diploids. This implies that the largest genome contains roughly 4 × 10¹⁰ more base pairs than the smallest and has chromosomes that are nearly twice as large. On this basis we assumed that nuclear DNA content as measured using flow cytometry may be used to produce easily obtainable systematic data. Triploidy in G. rizehensis and G. alpinus var. bortkewitschianus, tetraploidy in G. elwesii and hexaploidy in G. lagodechianus were confirmed by flow cytometry. In addition, as well as a number of polyploid cultivars, triploids were also found in G. nivalis and tetraploids and hexaploids in G. transcaucasicus and G. elwesii, respectively. DNA content confirmed the close relationships in some species pairs, including: G. nivalis and G. reginae-olgae, G. krasnovii and G. platyphyllus, G. gracilis and G. elwesii. Further investigation of the taxonomic status of these pairs is suggested. As a rapid diagnostic tool, applicable even in the case of dormant bulbs or sterile plants, flow cytometry has applications for conservation and in particular the monitoring of the trade in bulbous plants.