Structural Characteristics and Phenolic Composition of Maize Pericarp and Their Relationship to Susceptibility to Fusarium spp. in Populations and Inbred Lines

Maize (Zea mays L.) is one of the most widely cultivated cereals in the world, with multiple uses, including its role as a staple food for humans, as animal feed, and as a key industrial raw material. Its production is threatened by Fusarium spp., a widespread fungal pathogen that causes significant yield losses and contaminates grain with harmful toxins that constitute a health risk for consumers and animals. Among the grain characteristics reported as relevant for tolerance to this pathogen are pericarp thickness and composition, although results remain inconclusive. This study aims to evaluate the structural characteristics and phenolic composition of the pericarp in diverse native pigmented grain maize populations (NPMP) and inbred lines, and their relationship with susceptibility to Fusarium spp. Pigmented maize populations (EOGro, CTlax, EC149Pue, MGto, and ECMex) and inbred lines (B-50, B-50R, B-49 B-4A and B-5A) were used. All materials were grown at the same location, and tolerance to Fusarium spp. was assessed under natural and assisted infection using incidence (IN, %) and severity of infection (SI, %) as indicators. The phenolic composition (total soluble phenolics, phenolic acid fractions, insoluble phenolics, and phlobaphenes) and structural characteristics of the pericarp were determined, and proanthocyanidin content was quantified in the grain. Both IN and SI varied among genetic materials, with NPMP showing greater susceptibility than inbred lines, which had a thicker pericarp. Pericarp thickness was not correlated with IN, but it was relevant for SI, in both NPMP and inbred lines. Insoluble phenolics content was 31.4% higher in inbred lines compared with NPMP. High levels of proanthocyanidins and phlobaphenes were associated with greater tolerance to Fusarium spp. in some maize populations. Tolerance to Fusarium spp. was associated with pericarp thickness in inbred lines, whereas in native pigmented maize populations, it was linked to the accumulations of pigmented phenolics in pericarp.