Influence of Agronomic Practices on the Antioxidant Compounds of Pigmented Wheat (Triticum aestivum spp. aestivum L.) and Tritordeum (× Tritordeum martinii A. Pujadas, nothosp. nov.) Genotypes

Abstract

Twelve pigmented wheat genotypes, one tritordeum, and one common wheat were grown in three field experiments under varying nitrogen (N) fertilization rates to investigate the contributions of genotype, environment, and fertilization on the levels of phenolic acids, anthocyanins, carotenoids and antioxidant capacity of the grains. Soluble phenolic acids increased significantly (+16%) in the environment with high soil N content, while bound phenolic acids and anthocyanins decreased (-16 and -57%). N fertilization affected the agronomic and qualitative traits but had limited effects on some bioactive compounds (bound phenolic acids and anthocyanins). The greatest differences appeared among the color groups and within the same color types, with the black group showing the most anthocyanins and phenolic acids (34.4 and 1207 mg·kg^-1) and the highest antioxidant capacity. Some of the cultivars could be promising for the development of innovative supply chains and the production of functional foods, as they showed good yield and quality performances, and good antioxidant features.

Keywords: Triticum aestivum; anthocyanins; antioxidant capacity; carotenoids; nitrogen; phenolic acids; pigmented cereals; technological quality; × Tritordeum martinii.

Figure 1

Wheat and tritordeum genotypes grouped according to the grain color, which depends on the type and position of the pigments within the kernel layers. Pp, purple pericarp; Ba, blue aleurone; Pp + Ba, black grain; Ye, yellow endosperm; Trit, tritordeum.

Figure 2

Comparison of the (A, B) agronomic traits, (C–F) bioactive compounds, and (G, H) antioxidant capacity of the investigated wheat and tritordeum genotypes grouped according to the grain color. Pp, purple pericarp; Ba, blue aleurone; Pp + Ba, black grain; Ye, yellow endosperm; Trit, tritordeum; GY, grain yield; TKW, thousand kernel weight; SPAs, soluble phenolic acids; CWBPAs, cell wall-bound phenolic acids; TAC, total anthocyanin content; pnd-3-glu, peonidin-3-glucoside; cyd-3-rut, cyanidin-3-rutinoside; cyd-3-glu, cyanidin-3-glucoside; dpd-3-glu, delphinidin-3-glucoside; dpd-3-rut, delphinidin-3-rutinoside; TCC, total carotenoid content; AC, antioxidant capacity (FRAP and ABTS assays). The results are expressed on a DW basis. Different letters above the columns indicate significant differences between the six groups at p (F) < 0.05, according to the REGW-F test.

Figure 3

PCA biplot of the analyzed genotypes (n = 378) and phytochemical parameters associated with health-related substances. The table on the left-hand side shows the loadings of the variables for the first two principal components. Loadings greater than 0.4 are indicated in bold. The length of each variable vector is proportional to its contribution to separating the genotypes, and the direction of the vectors indicates their relative contribution to PC1 and PC2. The sample plots are grouped by genotype and by environment, on the basis of the average mean of 3 N levels and 3 replications. The color names on the right-hand side indicate the color of the kernels. Pp, purple pericarp; Ba, blue aleurone; Pp + Ba, black grain; Ye, yellow endosperm. Environments: A (Cigliano, 2019–20), B (Cigliano, 2018–19), C (Carmagnola, 2018–19). SPAs, soluble phenolic acids; CWBPAs, cell wall-bound phenolic acids; TAC, total anthocyanin content; TCC, total carotenoid content; ABTS, antioxidant capacity determined by means of ABTS assay; FRAP, antioxidant capacity determined by means of FRAP assay.