Chromosome number and genome size of some Centaurea (Asteraceae) from Croatia

Genome size and chromosome number are characteristic species trait important in systematics, taxonomy and evaluation of biodiversity. The Adriatic coast of Croatia presents a unique area for biological and chemical research of plant material. Genus Centaurea (Asteraceae family) is already known for many medicinal plants that present a valuable source of potential medicines. In Croatia 79 Centaurea taxa have been listed, comprising 27 endemics. Previous chemical and biological observations of extracts and volatiles isolated from Centaurea species, showed differences in chemical composition and biological activity of volatile substances between different species. Some Centaurea species have many similarities in their morphological appearance, therefore the criteria of genome size and number of chromosomes contribute to plant material identification. Due to a high demand for a clear and authentic plant material identification in chemical research, genome size and number of chromosomes for six Centaurea species have made prior to chemical and biochemical research of isolated plant extracts. The genome size was estimated using flow cytometry. The chromosome number was determined using the standard karyological methods. The plant samples, seeds and leaves, were collected from wild growing natural populations of Croatia. The studied species present three basic chromosome numbers, x= 9, 10 and 11. The ploidy level of investigated species was diploid and tetraploid. Centaurea cristata and C. rhenana were tetraploid, whilst other species were diploid. The nuclear DNA amounts (2C DNA) range from 1.70 to 3.57 pg. Using the Leitch's et al. criteria all these taxa belong to the group of very small genome size. The results present the novel values for C. cristata, and C. rhenana. The studied species will be the object of our future studies concerning the chemical composition of volatile and non-volatile plant extracts and their biological activity and differences in chemical composition due to a level of ploidy.