Investigating Inter- and Intra-specific Karyotypic Diversity of Some Species of Salvia Genus in Iran

The Salvia genus, an important member of the Lamiaceae family, is extensively utilized in the food and pharmaceutical industries. To investigate the karyotypic diversity of this genus, chromosomal studies were conducted on 25 populations belonging to eight different species. Various karyotypic traits were measured and evaluated. With the exception of the tetraploid species S. verticillata L., all other species were diploid. The basic chromosome numbers observed in different species were x = 8, 10, and 11. Among the species, S. glutinosa L. exhibited the highest relative chromatin values (VRC); while, S. spinosa L. had the lowest VRC. In terms of intra-chromosomal asymmetry, the species S. macrosiphon Boiss. displayed the most symmetrical karyotype; whereas, the population of S. glutinosa (243) had the most asymmetrical karyotype. In relation to inter-chromosomal asymmetry, S. reuteriana Boiss. (30,344) exhibited the most asymmetric karyotype. Statistically significant differences (p < 0.01) were observed among the different populations and species in terms of all chromosomal characteristics. Principal components analysis revealed that the first, second, and third components represented parameters related to intra-chromosomal asymmetry, inter-chromosomal asymmetry, and chromosomal length, respectively. Cluster analysis grouped the various populations and species into six different classes. The smallest genetic distance was observed between populations of S. limbata C.A. Mey. (33,295 and 36,916) species; while, the highest genetic distance was found between S. reuteriana Boiss. (20) and S. glutinosa L. (242). In terms of karyotypic evolution, there was no significant difference between different chromosomal basic (x), but more karyotypic evolution was observed among populations with x = 10. Flow cytometry measurements showed that 2C DNA contents varied from 1.65 to 1.88 pg in diploid species and with a 2C value of 2.84 pg being obtained for a tetraploid species. The relative fluorescence intensity (RFI) of propidium iodide-stained nuclei was a function of the number of chromosome sets (x), as shown by the linear equation RFI = 3.7x − 2.4 (R2 = 93%). The data indicated that DNA flow cytometry can be useful for determining the ploidy level in seedling stage in salvia genus. Also, the conventional polyploid evolution of increasing nuclear DNA content has occurred simultaneously with increasing chromosome number. Finally, in this study, the evolutionary relationships of chromosomes with plant morphology and molecular studies have been discussed. The results provide basic data for further studying on genomics, cytobiology and germplasm resource for Salvia genus.