Chromosome Number Variation in Iranian Populations of Acorus calamus

Abstract

Different ploidy levels, diploid (2n=2x=24) to hexaploid (2n=6x=72) have been reported for Acorus calamus, a perennial medicinal plant. According to available information, there is a significant relationship between the ploidy level and essential oil compositions and medicinal properties of this important genetic resource. However, there is no information about the chromosome number of A. calamus that has been recently rediscovered in Iran. This research was conducted to determine the chromosome number and ploidy level of three A. calamus populations in Iran. The fresh roots were removed from the rhizome and pretreated in 0.002 Mole of 8-hydroxyquinoline and fixed in Ethanol: acetic acid solution for 24 hours. The fixed roots were macerated in 60° C in 1N HCl for about 30 minutes. A squash technique was used with 2% aqueous aceto-orcein as the stain. The somatic chromosome number and karyotype details were studied at least in five well-prepared metaphase plates for each population. The populations studied showed interesting diversity in cytogenetic features; chromosome number and ploidy level. Arzefon and Pelesk populations had two different chromosome number; 2n=2x=24 and 2n=3x=36, while Alandan population had 2n=3x=36 chromosome number. The haploid total chromosomes length of Arzefon, Pelesk, and Alandan populations were 13.28, 11.33 and 11.3 µm respectively. The longest chromosome was 1.48 µm in Arzefon population and the shortest chromosome with a size of 0.61 µm observed in Pelesk population. The existence of this genetic diversity is important in domestication strategies and the use of appropriate cytotype. Based on the results of this research and available information, the basic chromosome number of A. calamus is x = 12.