Influence of Exogenous 28-Homobrassinolide Optimized Dosage and EDAH Application on Hormone Status, Grain Filling, and Maize Production

Abstract

Exogenously applied phytohormones improve the endosperm cells and establish greater kernel sink capacity and grain filling, improving grain yield. In this study, 28-Homobrassinolide (HBR) dosages (20, 25, and 30 mg a. i. ha−1) were applied separately at the silking stage under controlled conditions, and EDAH (a mixture of ethephon and diethyl aminoethyl hexanoate) dosage of 90 g a. i. ha−1 was sprayed at the jointing stage to enhance the lodging resistance. Our objective was to investigate whether the application of HBR under controlled conditions or with EDAH could enhance the grain filling rate by regulating endogenous hormones. The results showed that HBR at the silking stage significantly increased endogenous hormones (ABA, IAA, Z+ZR), hampered leaf senescence, enhanced photosynthetic, improved dry matter accumulation in grains, and increased the grain-filling period, filling rate, and thousand-grains weight. Additionally, HBR 25 and 30 mg a. i. ha−1 increased the final yield by 9.9% and 19.5% compared to the control (CK) in 2020 and 14.1% and 18.95% in 2021, respectively. There was no significant difference between the results obtained from HBR-controlled and EDAH treatments at the jointing stage. Thus, we conclude that spraying HBR 25~30 mg a. i. ha−1 under controlled conditions may increase the grain yield under normal weather conditions. In adverse weather conditions and heavy wind, spraying EDAH 90 g a. i. ha−1 at the jointing stage and HBR 30 mg a. i. ha−1 at the silking stage can enhance maize production.