Precision phenotyping and association between morphological traits and nutritional content in Vegetable Amaranth (Amaranthus spp.)

Amaranth (Amaranthus spp.) is an important leafy vegetable and grain crop which is a good source of nutrients and bioactive compounds, widely consumed in several parts of the world. However, varieties of different Amaranthus species show great phenotypic variation and may also have different nutritional attributes. This study aimed to phenotype vegetable amaranth accessions of four different species (Amaranthus hypochondriacus, Amaranthus cruentus, Amaranthus dubius and Amaranthus blitum) and relate the morphological data to nutritional attributes of the leaves. Ten selected amaranth accessions obtained from the World Vegetable Center collections in Arusha and Taiwan were subjected to a high throughput phenotyping system to determine digital biomass, greenness, plant height and hue of the leaves using 3D scanning. These phenotypic data was correlated with the nutritional traits including carotenoids, flavonoids, vitamin C, minerals and oxalate contents of the various accessions. The analysis of variance for both morphological and nutritional traits showed significant (P≤0.05) difference for most traits recorded between the accessions. The A. blitum (AM1909) had the slowest daily increases in morphological traits compared to other accessions. Significant correlations were also recorded among the various morphological traits. Amaranth accession AM1908 (A. dubius) and AM1910 (A. dubius) had the highest content of most nutrients, while AM1902 (A. hypochondriacus) and AM1903 (A. hypochondriacus) had the lowest nutrient content. Significant correlations were observed between greenness with oxalate and vitamin C contents, as well as between hue values and carotenoids. We conclude that only some of the morphological traits of amaranth are associated with the nutritional content of the leaf. Based on the findings, we recommend that leaf color can be used as breeding trait to target nutritional attributes.