New Chromosome Number Reports in Cousinia Species (Compositae)

Abstract

The cytological study of several populations in 4 species of Cousinia tenuifolia, C. tabrisiana, C. urumiensis and C. microcephala showed the occurrence of 2n=2x=26 chromosome number in all the species studied, information which is new to science. The species formed mainly bivalents and univalents in the metaphase of meiosis I, but in some populations quadrivalents were also formed due to heterozygote translocations. A wide range of meiotic abnormalities were observed including laggard chromosome formation, chromosomes stickiness and tripolar cell formation, leading to the formation of unreduced pollen grains. The occurrence of 0–2 B-chromosomes was observed in most of the species and populations studied. Karyotype analysis showed that the chromosomes are metacentric (m) and submetacentric (sm), varying in size from 0.55 to 1.79 µm. The ANOVA test showed significant difference in total chromosome length, size of the long arm and short arm of the chromosomes as well as arm ratio of the chromosome pair numbers 1–4 and 8, indicating the role of both quantitative and structural changes of chromosome in cytological diversity of Cousinia species.