Post-flowering environment determines zein composition and kernel hardness in maize

Abstract

Maize (Zea mays L.) grain endosperm is composed by starch and proteins (mainly zeins, Z1 and Z2) and other minor components. The dry milling industry demands grains with high endosperm hardness, which is determined by both its chemical composition and by the structure established within its components. Kernel hardness is influenced by both genotype and post-flowering environmental conditions, which affect the depositions of these components. This study aimed to explore the variations in zein composition under different post-flowering environments achieved by combining sites, sowing dates, and year, which resulted in different levels of source-sink ratio during the grain filling period. Additionally, we examined the relationship between these variations and kernel hardness. The combination of site, sowing date and genotype resulted in a wide range of protein and total zein percentage, primarily driven by variations in Z1. Moreover, for the semi-dent and flint hybrids, an increase in Z1/Z2 ratio was explained by a higher source-sink ratio during the grain filling period. While variation in total, Z1 and Z2 percentages did not account for the differences in kernel hardness across environments, kernel hardness was linked to an increase in Z1/Z2 ratio. Further research is needed to better understand the mechanisms underlying kernel hardness.