Genetic variability of kernel phenolics in maize (Zea mays L.) inbreds with differing levels of resistance to gibberella ear rot

A comprehensive study was performed to investigate the kernel phenolics content and profile of a broad range of maize inbreds varying in disease resistance to gibberella ear rot. Three phenolic fractions (soluble free, soluble conjugated, and insoluble bound) at different kernel developmental stages in two growing seasons were analyzed. The phenolics content and profile revealed a genotype dependency. The highest amount and diversity of phenolics were at day 11 after self-pollination in both growing seasons. This was confirmed by a distinctive PCA biplot clustering of phenolics at day 11 compared to other harvesting days for all fractions. A strong negative correlation was found between the conjugated and bound phenolics in both growing seasons (in 2016, r = 0.93, p < 0.0001; and in 2018, r = 0.94, p < 0.0001). In both growing seasons, the main phenolic compounds in the free, conjugated, and bound fractions were chlorogenic acid, caffeic acid, and t-ferulic acid, respectively. Comprehensive results were presented for how the phenolics evolved over the period of kernel development and how their content changed. The PCA-biplot analysis revealed different patterns of clustering for phenolic associations in different fractions as well as in different growing seasons, reflecting the evolution process of individual phenolics during kernel filling period. Overall, genotypes with higher disease resistance possessed higher phenolics in the bound and conjugated fractions at blister stage. This study provides a useful resource of maize inbred phenolics profiles that could be applied in future breeding efforts.