Genome size, i.e. the total amount of DNA in an unreplicated somatic nucleus is considered an important character in the biology of organisms, and it is especially relevant for land plants given the extraordinary diversity reported. Despite the continuous growth of data and the efforts aimed at increasing our understanding of plant genome size diversity, more data are needed to have an evenly representation across lineages. With this premise in mind, in this work, we investigated genome size, complemented with chromosome data in eight species of the genus Petrorhagia (Caryophyllaceae) from Turkey. Chromosome counts made indicate that the species studied are diploid except for one species, P. saxifraga, which is probably a tetraploid, based on previously published estimations of nuclear DNA contents. The presence of both basic chromosome numbers x = 15 and x = 13 is confirmed, the latter being restricted to the species P. hispidula and P. cretica. The counts carried out for the Turkish endemic species, in P. hispidula (2n = 26), P. pamphylica (2n = 30) and P. peroninii (2n = 30) represent novel data for the genus. Nuclear DNA contents ranged from 1.24 to 2.32 pg/2C (varying 1.87-fold). Based on available data, genome expansions in the genus seem to have occurred through different evolutionary mechanisms, such as polyploidy and differential repetitive DNA activation, evidencing contrasting genomic trajectories between closely related taxa. This work was supported by Ministry of Science and Innovation - Spanish Government (projects CGL2017-84297-R) and GReB (Grup de Recerca en Biodiversitat i Biosistemàtica vegetals; Generalitat de Catalunya, project 2017SGR1116). J.P. benefited from a Ramón y Cajal fellowship (RYC-2017-2274) funded by MCIN/AEI/ 10.13039/501100011033 and by “ESF Investing in your future”. 1. Introduction 2. Materials and methods 2.1. Plant material 2.2. Chromosome counts 2.3. Sequence alignment and analysis 2.4. Phylogenetic data mapping 3. Results and discussion 3.1. Chromosome numbers in Petrorhagia: presence of two base chromosome number 3.2. Small genomes are prevalent in the genus Petrorhagia 4. Conclusion Acknowledgements References