Karyological variability and chromosomal asymmetry in highland cultivars of Chenopodium quinoa Willd. (Amaranthaceae)

Abstract

Chenopodium quinoa Willd. is rapidly gaining importance worldwide as a superfood. However, structural diversity and asymmetry analyses of chromosomes of different cultivars of the species are largely understudied primarily owing to their small chromosomes. In this paper, karyomorphological investigations were performed on 21 cultivars of C. quinoa with varying seed morphology cultivated widely in the highland regions of the Andes, which is the center of domestication of this species. Somatic chromosome number was found to be 2n= 36 in all cultivars with no occurrence of mixoploidy. Lengths of individual chromosomes varied between 0.63–6.53 μm, with their short arms ranging from 0.25–2.95 μm and long arms between 0.38–3.58 μm. Types of primary constriction ranged from median to sub–terminal. One pair of chromosome in each complement possessed a secondary constriction. Chromosome complements of all cultivars belonged to the asymmetry class 2B with an average asymmetry index value of 3.21±0.61. Values of intra- and inter-chromosomal asymmetry indices were 0.30±0.02 and 0.20±0.02 respectively across all cultivars. The average coefficients of variation of chromosome lengths was 19.77±2.11 and average centromeric index was 16.28±2.12. Arm ratio of the chromosomes varied from 0.34 to 5.76. The mean values of karyotypic asymmetry, symmetry index and karyotype asymmetry index percentage were 17.69±1.53, 147.69±5.54 and 58.71±0.86 respectively. Pearson correlation revealed strong correlation within inter– and intra–chromosomal asymmetry indices. Our analyses uncovered higher chromosomal variation in quinoa than previously found with high inter–varietal similarities among the studied cultivars, revealed from scattered diagrams between asymmetry indices.

Keywords

• Chenopodium quinoa
• chromosome
• karyotype
• chromosomal asymmetry
• inter-varietal symmetry