Chromosome morphology and karyotyping in native species of Rheum ribes

Rhubarb (Rheum ribes) is a perennial plant of Iranian Zagros rangelands belonging to thepolygonaceae family. It is an edible and therapeutic plant with the stem believed to be a good laxative. Its root extract is used to cure diabetes, stomach upsets, vomiting, smallpox, and measles. Its fresh petioles and stems are also consumed as vegetables and to make jam, desserts, and pickles. Genetic exploration and conservation of this species requires basic cytogenetic information which is highly lacking in the scientific literature. In this study the chromosome characteristics and Karyotype of three Zagros accessions were studid. The analysis of mitotic, distinct metaphasic chromosomes involved seed germination, pretreatment of tissue samples, fixation of cellular and chromosomal structures, hydrolyzation of samples, and chromosome staining. Samples were observed microscopically for chromosome number and morphology which led to the preparation of Karyotype and ideogram of the accessions. The results of the chromosome count showed that all three accessions had 42 chromosomes and their ploidy level remained unsettled. Reports on the number of chromosome and ploidy level in other species of Rheum ribes are contradictory. Karyotype classifications following Stebbins method, placed accessions Isfahan 1 and Isfahan 2 in 1A class group with more Karyotypic symmetry and accession Qom in the 2A Karyotypic class with lower Karyotypic symmetry. Investigation of karyotypic symmetry condition of accessions using Romero Zarco method confirmed the karyotypic symmetry of accession. It was also specified that Isfahan 2 accession had more inter-chromosome symmetry and Isfahan 1 accession had more inter-chromosome symmetry