Abstract
A new species of Centaurea (Asteraceae) from Turkey is described and illustrated. Centaurea nallihanense Uysal & Hamzaoğlu occurs on stony slopes of corrupted oak openings in the Province of Ankara in Central Anatolia. It seems to be similar to C. sect. Ptosimopappus but related to the Cheirolepis-Pseudoseridia complex. Diagnostic characters of similar taxa are provided and a comprehensive discussion is held on the basis of molecular and karyological data. The geographical distribution of the new species is mapped. The chromosome number of C. nallihanense, 2n = 2x = 18, counted in root tips, is also reported and illustrated. Its karyotype formula is 6m+3sm. The karyotype of C. nallihanense consists of mainly metacentric chromosomes with the length ranging from 1.113 to 1.771 µm, and the total haploid chromosome length of 12.909 µm. Also, the ITS gene region of the new species is amplified and sequenced to compare with the relatives and to identify the taxonomical position of the new species within Centaurea.