Cytogenetic Diversity Analysis of Genotypes of Elymus hispidus (Opiz) Melderis var. villosus (Hackel) Assadi

Background and Objective: Elymus hispidus (Opiz) Melderis var. villosus (Hackel) Assadi is a key forage grass species with modrate nutritional value and notable resistance to environmental stresses. Investigating the cytogenetic diversity of this species can improve understanding of its genetic structure and support its effective utilization in breeding programs. The aim of this study was to evaluate the karyotypic diversity of 24 different genotypes from various regions of Iran by analyzing chromosomal traits and karyotypic indices.
Materials and Methods: Twenty-four genotypes of E. hispidus var. villosus, collected from diverse regions of Iran and preserved in the National Natural Resources Gene Bank, were provided. Seeds were sown in Petri dishes and prepared for cytogenetic evaluation at the Agricultural and Natural Resources Research Center of Kermanshah Province, Iran. Metaphase chromosomes were prepared from young root cells using conventional staining and observed under a light microscope. Chromosomal parameters, including total chromosome length (CL), long arm length (LA), short arm length (SA), and 19 additional karyotypic indices, were measured. Data were analyzed using analysis of variance (ANOVA) to assess significant differences among genotypes, followed by correlation analysis and hierarchical clustering. Karyotype symmetry indices and Stebbins’ classification system were used to determine the degree of evolutionary advancement and structural symmetry among genotypes.
Results: All studied genotypes were hexaploid (2n=6x=42), but exhibited considerable variation in karyotypic formula. Genotype 19 had the highest total form percentage (TF%) and the lowest intrachromosomal asymmetry index (A1), indicating a more symmetrical karyotype and lower evolutionary advancement, whereas genotype 14 showed greater asymmetry and a higher degree of chromosomal evolution. ANOVA revealed significant differences (p < 0.01) among genotypes for all chromosomal traits. The longest chromosomes were observed in genotypes 23 and 10, while genotypes 6 and 7 had the shortest chromosomes. Cluster analysis grouped the genotypes into three distinct clusters, which corresponded with patterns observed in A1, A2 (interchromosomal asymmetry), coefficient of variation of chromosome length (CVcl), centromeric index variation (CVci), and Stebbins’ classification. Significant positive correlations were observed between total chromosome length, arm lengths, and indices such as relative chromatin value (VRC), difference in relative chromosome length (DRL), and karyotype asymmetry index (AI), suggesting high genetic potential and breeding capacity within these genotypes.
Conclusion: This study demonstrated substantial cytogenetic and karyotypic diversity within E. hispidus var. villosus, highlighting its value as a genetic resource for breeding and genetic improvement programs. Significant variation in chromosomal indices, including chromosome length, arm proportions, and symmetry metrics, reflects a high degree of structural diversity. Such diversity can be exploited to select genotypes with superior forage yield and quality. Utilizing intraspecific diversity, particularly through crosses between genotypes with high genetic distance (based on cluster analysis), can lead to heterosis and improve both quantitative and qualitative traits. These genotypes can be effectively used in intraspecific crossing programs to develop new varieties with higher tolerance to environmental stresses, enhanced forage yield, and increased sustainability of rangeland exploitation.