Effects of fertilizers and exogenous plant growth regulators on the grain texture and starch physicochemical properties of waxy maize

Background Fertilizers and exogenous plant growth regulators (PGRs) play a critical role in regulating the grain quality of waxy maize. Nevertheless, the combined effects of fertilizers (bio-organic fertilizer, BOF; nitro-based compound fertilizer, NCF; green intelligent fertilizer, GIF) and three PGRs (iron chlorine e6, ICE6; coronatine, COR; 14-hydroxylated brassinosteroid, 14HB), and clean water control, on the grain texture and starch physicochemical properties of waxy maize remain unclear. Results Under BOF and GIF treatments, the grain hardness, springiness, and chewiness were higher than those under NCF. These differences were more pronounced when BOF and GIF combined with PGRs. Compared with NCF, BOF and GIF increased the soluble sugar, total starch and amylopectin contents. In addition, BOF increased starch average granule size while decreasing pasting viscosity, GIF showed the opposite effect on pasting viscosity. Additionally, both BOF and GIF increased increased starch relative crystallinity. The application of ICE6, COR, and 14HB improved grain hardness, springiness, chewiness, total starch and amylopectin contents. Furthermore, three PGRs increased starch average granule size and changed granule volume distribution, increased gelatinization enthalpy and retrogradation enthalpy, decreased relative crystallinity and retrogradation rate. Random forest analysis further identified retrogradation enthalpy and amylopectin content as the primary determinants of grain textural properties. Conclusion Both fertilizers and PGRs modulated grain texture and starch physicochemical properties. Among all combinations, BOF combined with ICE6 exhibited balanced textural parameters and favorable overall starch physicochemical properties suitable for high-quality waxy maize production.