Phenolic Profile and Susceptibility to Fusarium Infection of Pigmented Maize Cultivars

Abstract

Maize is a staple food source in the world, whose ancient varieties or landraces are receiving a growing attention. In this work, two Italian maize cultivars with pigmented kernels and one inbred line were investigated for untargeted phenolic profile, in vitro antioxidant capacity and resistance to Fusariumverticillioides infection. "Rostrato Rosso" was the richest in anthocyanins whilst phenolic acids were the second class in abundance, with comparable values detected between cultivars. Tyrosol equivalents were also the highest in "Rostrato Rosso" (822.4 mg kg^-1). Coherently, "Rostrato Rosso" was highly resistant to fungal penetration and diffusion. These preliminary findings might help in breeding programs, aiming to develop maize lines more resistant to infections and with improved nutraceutical value.

Keywords: FER; Fusarium; anthocyanins; flavonoids; metabolomics; phytoalexins.

FIGURE 1

Phenotype of ears and kernels of “Purple B73” (Aa), “Rostrato Rosso” (Bb), “Nostrano della Val di Non” (Cc), and control (Dd).

FIGURE 2

Not averaged unsupervised hierarchical clustering on the phenolic profile of maize samples (similarity: Euclidean; linkage rule: Ward). Compounds’ intensity was used to build up fold-change based heat map, on the bases of which clusters analysis was done. Agrister was used as a non-pigmented kernel control.

FIGURE 3

Venn diagram of differentially accumulated compounds (Volcano plot analysis, P < 0.01, fold-change > 5), comparing each of the three genotypes against Agrister. The upper diagram (A) represents all the differential phenolic compounds, while the lower one (B) only the up-regulated compounds.

FIGURE 4

(A) Cumulative abundance, expressed as mg kg⁻¹ equivalents, of the different phenolic subclasses in the analyzed maize genotypes, as gained from UHPLC-ESI/QTOF-MS screening analysis. (B) Orthogonal Projections to Latent Structures Discriminant Analysis (OPLS-DA) on maize genotypes according to their phenolic profile. Individual replications are given in the class prediction model score plot.

FIGURE 5

Pictures and box-plots of maize kernels artificially inoculated with F. verticillioides. Examples of treated seedling after RTA assay (A); the same genotypes after ear inoculation in field (C). Box plots representing severity after inoculation in RTA (B) and percentage of FER after field inoculation (D).