Diversity in the morphology and antioxidant components of Amaranth (Amaranthus spp.)

The diversity in the morphological characters and antioxidant components of 18 accessions of amaranth germplasm collection at National Plant Genetic Resources Laboratory (NPGRL) was investigated. Morphological characterization was done using standard descriptors published by International Board for Plant Genetic Resources (1981). A total of 34 characters comprising 22 qualitative and 12 quantitative data were observed. Based on Shannon-Weaver Diversity Index, 17 characters (50%) were found to have high diversity (0.67) while two characters were invariant. A total of 299 characters were found to be significantly correlated with one another. Cluster analysis of qualitative and quantitative data produced three and eight clusters, respectively at 0.7 r sup 2. Principal Component Analysis revealed 10 important quantitative characters namely, plant height at flowering and at maturity, leaf length, petiole length, leaf width, stem diameter, terminal inflorescence length, days to flowering, and length of top and lateral branches contributing 84% of the total variation. Using Gower's coefficient at 0.7 r sup 2, five clusters were generated from all the morphological characters. Following the taxonomic key, 4 species A. spinosus, A. gracilis, A. hybrids, and A. tricolor were identified in the 18 accessions used in the study. The results of the taxonomic identification and cluster analysis agree with each other. Evaluation of antioxidant activity, total phenol content, flavonoids and tannins revealed variations in the amaranth collections. GB56174, LSG09-002 and PHL6220G showed good potentials on the parameters measured. Positive correlation among the % antioxidant activity, flavonoids, total phenols and tannins were observed in the study. Some morphological characters were found to be positively and negatively correlated to antioxidant component. Different experiments to evaluate the antioxidant properties of amaranth on different plant parts, growth stages, sampling time, variety, storage condition and length, and cooking time were also conducted. The level of antioxidants in the different parts of amaranth followed the sequence: leaves greater than or equal to flowers greater than stem = roots. No significant difference in the antioxidant components was observed at 3-week and flowering stages of amaranth. The effect of differences in the antioxidant components of amaranth at different sampling time was accession specific. Amaranth leaves could only be stored for 3 days at ambient condition while samples could be kept in the refrigerator for 7 days without a significant reduction in the antioxidant activity of the vegetable. Cooking the amaranth leaves for 3 to 7 min significantly reduced its antioxidant activities compared to fresh and blanched leaves. The water used in cooking the leaves, however, had higher antioxidant activities than the one used for blanching the leaves. Some strategies were recommended to promote the conservation of amaranth through utilization. There is also a need to regenerate the existing amaranth germplasm collections at NPGRL with low viability as well as acquisition of unpresented materials increase genetic diversity.