Determination of nuclear dna content and ploidy level of some aethionema taxa (Brassicaceae) from türki̇ye

The genus Aethionema Aiton, classified within the family Brassicaceae, subfamily Aethionemoideae, and tribe Aethionemeae, is represented worldwide by approximately 70 species, the majority of which are distributed across the Irano-Turanian and Mediterranean phytogeographical regions. Turkey, particularly along the Anatolian diagonal, is not only a gene center for the genus but, together with Iran, also represents one of its major centers of diversification. According to the most recent taxonomic revisions, the genus is represented in the Flora of Turkey by 51 species, 33 of which are endemic, corresponding to an endemism rate of 65%. Taxonomically, Aethionema is among the most complex genera in Turkey. Due to the requirement of mature fruits for accurate species identification, many herbarium specimens remain unidentified or have been misnamed. Published chromosomal studies on this genus are extremely scarce, and existing chromosome counts are insufficient to determine the basic chromosome number. Furthermore, previous studies have reported that chromosomes in Aethionema are very small, which has posed challenges for the determination of chromosome morphology. In this study, nuclear DNA contents and ploidy levels were determined using flow cytometry in 160 accessions belonging to 41 Aethionema taxa naturally occurring in Turkey, collected from different altitudes and geographical regions. In DNA content analyses, Vicia sativa L. (2C=3.65 pg) was used as the reference standard and Propidium Iodide (PI) as the fluorescent dye, with 2C values calculated on a peak basis. For the first time, DNA amounts corresponding to different ploidy levels were reported: diploid (2n=2x=24) in 49 accessions, triploid (2n=3x=36) in 57 accessions, tetraploid (2n=4x=48) in 53 accessions, and pentaploid (2n=5x=60) in three accessions. For taxa with unknown chromosome numbers, predictions were made for a total of 49 accessions using statistical models developed in R software, based on references from previous studies. The results of this study were also compared with previously reported chromosome numbers and DNA contents in the genus and confirmed accordingly. Among the examined samples, the highest 1C value (0.54 pg) was recorded in Aethionema compactum (Hartvig & Strid) Yild., while the lowest 1C value (0.22 pg) was observed in Aethionema spicatum Post. At the conclusion of this study, the nuclear DNA contents and ploidy levels of Aethionema taxa were evaluated in order to contribute to the taxonomy of the genus. The genus was emphasized as a basal group, and the results revealed a lower average DNA content (1C=0.37 pg) compared to previously reported values (1C=0.71 pg). Keywords: Aethionema, Brassicaceae, Cytogenomic, C-Value, Ploidy levels