Effects of foliar application of exogenous regulators on the grain quality and starch physicochemical properties of waxy maize

Foliar application of exogenous regulators is an important agronomic practice for improving the grain quality of waxy maize. This study investigated the effects of foliar applications of iron chlorin e6 (ICE6), coronatine (COR), 14-hydroxylated brassinosteroid (14HB) and water control (CK) on the grain quality and starch physicochemical properties of two waxy maize cultivars, namely Jikenuo 2 (JKN2) and Tianguinuo 932 (TGN932). Compared with CK, ICE6, COR, and14HB treatments enhanced the grain sweetness, the contents of soluble sugar, total starch and amylopectin, as well as reduced the pericarp thickness and skin residue rate. Additionally, these three regulators treatments increased the grain hardness and decreased grain resilience. These three regulators treatments increased starch peak viscosity, volume-weighted mean particle size, rapidly and slowly digestible starch, reduce relative crystallinity and resistant starch content. Granule size was the primary determinant factor in grain chewiness and hardness, starch pasting properties and crystallinity predominantly affected grain springiness and resilience. Overall, foliar application of iron chlorin e6, coronatine and 14-hydroxylated brassinosteroid provide new insights for the utilisation of waxy maize starch in the food industry.